View Full Version : Infinity Quantum 3


M Jarve
01-22-2010, 11:19 AM
What follows are my initial impressions of what Infinity considered, at one time, the "... third-best speaker in the world."

I don't think it's necessary to get into the lineage and intricacies of the Quantum series or the evolution of the Quantum 3, as this information is documented elsewhere by people much more knowledgeable than I. I will say that the Quantum 3 is a vastly scaled-down version of their erstwhile TOTL Quantum Line Source (QLS-1), and, while it uses all the same drivers, it uses less of them (save for the woofer and mid-bass coupler). The hallmarks of the Quantum series were the use of the then revolutionary EMIT tweeter (a planar tweeter), and the Infinity-Watkins "dual-drive" woofer. Further, the upper echelon of the Quantum series utilized phase-aligned driver placements, and simple 1st order crossover networks designed to maintain proper time alignment.

In any event, these were supposed to be the proverbial bee's-knees among speakers, maintaining the performance of the QLS-1, but in a package and price that was just over half the cost.

When I got this set home, I discovered, to my horror, that one of the mid-bass couplers was not operating. Knowing, as I did, that the L-pads in the crossover had seen much better days (and indeed, were more or less corroded beyond redemption), I bypassed the L-pad (as I had done for the EMITs in the other speaker), but found that the coupler was still not outputting any sound. Further investigation found that the driver did indeed have an open voice coil. However, I was undaunted and looked to another set of speakers I had on hand that used a very similar driver as a midrange unit. The other driver, unfortunately, was a 4Ω unit, as opposed to the 8Ω version used in the Quantum 3. I put in the call to the seller, knowing his propensity for having spare parts for everything he owns, to see if I could beg another mid-bass coupler from him. He did not have one though, but offered to make it right by reimbursing me for the cost of another, should I find one.

Having not much left to loose, so to speak, I worked out how installing the 4Ω unit would affect the crossover points. Thankfully, Infinity made my job easier with the addition of many series resistors- what would have been a drop from 8Ω to 4Ω was going to be a more benign 13.5Ω down to 9.5Ω. This meant that the bandpass crossover would narrow its bandpass, but only by a little: from 200-600Hz to ~250Hz-550Hz. This, coupled with the gentle 6dB slope, meant the harm from changing the driver would be minimal.

I mention this mostly because it I think it will have changed the performance (and thus my analysis) of the speakers, but perhaps not to a large degree. I will say that, when I had one speaker configured with the original (working) mid-bass coupler and the other with the substitute, the difference between them was not too great, but it was noticeable. I did replace the mid-bass couplers in both speakers with the ones I had on hand so as to maintain balance between speakers.

So, on to the initial listening. As usual, what follows are just my first impressions, and my opinion is likely to change with further critical listening and the eventual replacement of the mid-bass couplers with the original, correct part.

For the past year (more, actually) I had been using a set of IMF TLS-50's, which are the speakers by which the Quantum 3's are judged. Right off the bat, however, they seem to possess greater similarities than differences. Both offer extended low-frequency response, as well as adequate high-end extension, and both offer smooth, balanced midrange. Where the differences lie are in the details, and when comparing both directly, each holds an edge over the other in certain disciplines.

The first noticeable difference is that the Quantum 3 seems to have some amount of coloration in the midrange. This has the effect, when compared to the TLS-50, of implying a more "boxy" sound. As of right now, I attribute this mostly to the substitute driver I'm using, as this coloration lies right in the range that it is operating in, and the sound is that of the mid-bass coupler not smoothly blending with the dome midrange driver. Aside from that, the midrange region is quite good, with lively, but not hard vocals and strings. The midrange is slightly more forward than it is with the IMF's, but this is most likely due to having to have the L-pads turned up all the way (or nearly so) in order for them to pass sound. Once the L-pads are replaced, and I am better able to dial in the sound, I'm certain that any issues of midrange forwardness will be resolved. As it is, it is only just noticeable and does not distract from listening.

The high-end of the Quantum 3 and the TLS-50 are very much comparable, each possessing very smooth high-frequency reproduction. Where the Quantum 3 has the edge is in the very top-most air. This is a region that the TLS-50 can play into, but it does not seem to impart the same sense of effortless and infinite extension that the Quantum 3 does. Where the TLS-50 holds its own, and indeed outperforms the Quantum 3 (at least in my room) is in giving a sense of space. The Quantum 3 does provide a fairly good L-R soundstage, better than I anticipated given that they are not mirror imaged, it does lack the sort of depth that I've become accustomed to. In that regard, though, it is in good company with other very highly regarded speakers. It's not that they do not give a sense of depth, but rather that I have yet to hear a speaker (aside from properly setup Maggies) that can compete with the TLS-50 in that regard. Further, the dipole, rear-facing tweeter of the Quantum 3 could be a liability in my room, as one just fired down the length of the basement, while the other hits a wall not more than a foot behind it.

Bass performance is where the two systems are most different, and indeed, each covers a performance metric better than the other. Bass from the TLS-50 is exceptionally deep, sonorous, and tuneful. It sounds best with pipe organ, bowed or plucked double-bass, and synthesized ELF bass. What the TLS-50 is deficient in is mid-bass impact, speed, and upper-mid-bass (100-200Hz). The Watkins designed woofer of the Quantum 3 does perform exceptionally well in the lower registers. It very nearly matches the TLS-50 in extension, in my room. Further, because of the sealed cabinet design, the roll-off the low-end is gentler than it is with the TLS-50, giving the impression, on passages where mid's and high's are subdued, that it can play as low or even lower. Where the Quantum 3's really shine, by comparison, is in bass energy. The bass performance is subjectively flatter, and does not have the peculiar mid-bass dip that handicaps the TLS-50 in that range. Nor does the speaker seem to have the more typical bass hump at around 50-80Hz that many speakers use to imply energy or extension. For this, it has superior performance in rock and some high-energy orchestral works, and offers excellent performance elsewhere. Unlike the TLS-50, it does not rattle the walls with a 20Hz sine-wave input at only a watt; it requires 3 or 4 watts to do the same.

One fear I had regarding the Quantum 3 was that I would have to use a different amp. I have grown to really like my Yaqin MC-10L II, and while I have some very good gear "in the stable", they don't possess the utter sonic bliss of the fully-tubed Yaqin. Infinity speakers, especially those with the Watkins licensed woofer, have a reputation of being very difficult to drive speakers and are colloquially known as "amp killers". It would seem, however, that the reputation is worse than the reality. While undoubtedly the Infinity is a difficult or unusual speakers to drive, the Yaqin seems to have no issues with it, provided that I keep the volumes sane, and use the appropriate 4-ohm tap. Indeed, the pairing is more synergistic, I might say, than the amp used to demo the speakers (a highly reputable amp). While certainly the combination will not be winning any SPL competitions, at volumes I normally listen at, and volumes I consider to be quite loud, the pairing never seemed to lack for power. Credit for this I give to the Quantum 3's moderate sensitivity. It seems, on the whole, to be at least 6dB more sensitive than the TLS-50, and I would not be surprised if it were even more sensitive. It is not, however, as sensitive as the JVC zero9, and it would easily take 50 watts of input to accomplish what something like a K-Horn would do with one.

And so there are my initial impressions, handicapped as they are with substitute mid-bass couplers and more dirty pots than your favorite greasy-spoon restaurant. As usual, more listening will bring more comprehensive and fully formed opinions, and I look forward to getting another original mid-bass coupler so that I can more accurately judge the midrange performance.

motorstereo
01-22-2010, 12:53 PM
Thanks for the in depth review and comparison. Only thing that I might add is that the quantum 3's are very very picky about placement. I had mine on a knee wall for a while as it was the only place I could fit those monsters. They sounded bad enough that I thought of selling them. They're directly on the floor now and they're not going anywhere. A major change for the better. Once you have your proper mid bass driver installed you may change your thoughts for the better about them as well. Of course those dirty corroded pots don't help and I'm sure a recap would be nice in these 30 year old speakers as well.
Another thing I might add is there are few things that I dislike worse than carrying mine up or down 2 flights of stairs which I've done several times. Damn those things are heavy and awkward. Good luck in finding your mid bass unit.

M Jarve
01-22-2010, 04:02 PM
Quite right about placement- I think they're even pickier than any Maggie I've had down here. It's taken the better part of an hour and a half, all told, of minor nudging and what not to get them to focus as well as I have.

I also have a bit of an update. I managed, through deft use of a soldering iron and a razor blade, to salvage the bad mid-bass coupler. As it turns out, the tinsel lead was only being held in place by some glue- it was not making contact with the VC, hence the open circuit. I managed to carefully solder the two ends together and now have functioning, original mid-bass couplers in each speaker. Based on the brief amount of listening I've done since, the difference is quite apparent, and for the better. The boxiness I indicated initially is gone, and the blend between the drivers is much better. I'll have to put on some of my "spooky-good imaging" music to see just how far the improvements have carried through.

Probably expect an update later this afternoon after I've listened for a couple of hours.

motorstereo
01-22-2010, 06:01 PM
Hey that's great news that you were able to salvage the mid bass driver Good for you. Glad to hear it made an improvement as I thought it would no doubt. It's nice to know that I'm not alone in my thinking that they're picky on placement. I just could not believe the dramatic difference in mine when I set them on the floor. For a while I even had them on their sides. Don't waste your time trying that one. Right now I'm running mine on a 350 watt carver t amp but I still prefer the much lower powered tube amps powering them. What I really wish is that I had a decent room for them. I've had mine in 4 different rooms and none of them did them justice due to placement issues. These are very nice speakers no doubt but I think they need a big open room with space to open up.

jimreeves
01-22-2010, 06:33 PM
Thanks for the informative and very diplomatic comparison M_Jarve. Your TLS-50's have the reputation for being a first class example of transmission line design and it's nice to hear that the Q3's stay with them by comparison. I've never heard either but hope to someday.
BTW, there were two of the original Philips drivers produced that are interchangeable for mid-bass use in the Quantums, the AD5060/W8 and the AD5062/W8. Pete_B wrote an interesting post in another forum about them, here...
http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=4320

bobrown14
01-23-2010, 08:20 PM
Hi all,

First thing I did to my QLS-IIIs was R&R the L-pads while the woofers were being re-foamed at MillerSound. Mine were corroded but not bad (a bit of dried spilt beer in one). They cleaned up nicely. I don't see how they could be toast. There are not much to them. A good clean and re-lube with FaderLube and they were back to formal glory. Sound mighty fine and dig down REAL deep, listening now to .... Balkan Beat Box.... say it again. Got mine paired with some DQ-10s in a wall of sound stage. QLS-IIIs on the outside with the DQ-10s in between with a sub in the corner. I've got tremendous sound and.. well danceable. It's my shop setup (more dance floor).:banana::banana:

It's all good.

Cheers,

Bob

M Jarve
01-26-2010, 02:00 PM
I have some more time clocked in listening to the Quantum 3's, as well as having cleaned up the L-pads, and taken care of some other issues.

First, the L-pads, as bobbrown indicated, were not a completely lost cause. Of the 6 in use (3 in each speaker), only one was actually beyond redemption. Fortunately, I had a spare on hand that had been used in an old tube O'scope I had in the garage. The big problem part was the center disc in each of the pots. I have a suspicion that they may have been silver plated, as they were completely black and non-conductive (in most areas) before I cleaned them up- after they had a very silvery luster and conducted perfectly well. The one lost-cause one had an issue where the wire coil had corroded through in one place. In any event, all the pots got cleaned up.

After that, and I had them all back together, I was listening and there seemed to be an issue in one channel. The upper midrange was very subdued and the sound-stage pulled hard to the opposite side. Playing a mono recording produced the same results. I thought for sure I had swapped polarity on one channel when I reconnected the speakers, but found that was not the case. All the same, the results were similar to such an occurrence. On the channel where I thought the problem lie, I switched speaker polarity only to find that the results were not entirely dissimilar. I was getting pretty cranky at this point, ready to stick them in a corner and live with the ugly, but eminently musical IMF's. Loaded up on coffee as I was, however, I simply started tearing things apart. First I looked at the wire polarity going to each driver (easier said than done for the front and rear EMIT's, as anyone who has worked on these speakers can attest to). Everything was correct. I then looked at the crossovers. Aside from the fact that there were some different components in each speaker (for instance, one speaker having three caps for the tweeter instead of two, or three resistors for the midrange instead of one) they all worked up to the same nominal value. I then followed the signal path for each driver (again , it's a mess in there), and compared both to the schematic I found on Klaus Pohlig's Infinity Classics site. Apart from neither speaker matching the official schematic, I found nothing particularly wrong. Double-checking, I came upon one piece of the puzzle- like the woofers in one channel, the leads at the crossover for the EMIT's in the "odd" channel were crossed. Swapping them around, and that channel's upper midrange suddenly reappeared and sounded great. The channels also now balanced with each other.

From what I understand, the above is unfortunately typical for earlier Infinity, with numerous changes made during production, and parts substitution run amok. It is also something, however, that would endear the company to me, as I know exactly how that works. :thmbsp:

So more listening I did- now with the proper mids in place and all the connections nicely dressed and all the L-pads sparkling clean. The speakers would now stand or fall for what they were, not for what 30+ years had done to them.

First of all, I want to reiterate that using the correct mid-bass couplers, as one would suspect, did wonders for the tonal balance of the speakers. The tone is now very well balanced and without gaps throughout its entire range. The coherence is also very good, with it being difficult to tell, from my listening position, what ranges each driver is reproducing. In terms of tonal balance and integration, it ranks among the best speakers I've heard.

Dynamics, sense of speed, and guttural, primal power are all massive bullet-points for this speaker. With the Yaqin as the power, the Quantum 3 matches or nearly matches the zero9 in terms of power and impact. It also outclasses the TLS-50 in this regard by an order of magnitude. Particularly with a very high-definition recording of a fireworks display, the sense that there were colorful mortars going off in my listening room was rather amazing. One could actually feel a shifting of the bowls and a rattling of the brain within the skull. Oddly, neither the amp or the speakers seemed strained for power during the performance making me wonder what I could do with 5 times the power that the h/k 775's could afford me. The Quantum 3 further impressed me, as the TLS-50's do, in that such sounds emanated as a single coherent wavefront from the speakers and not as a pop followed by a poof followed by a thud and rumbling that other speakers with less attention to time alignment produce. That little adventure also helped to aleviate the last of my fears about using the Yaqin as the power amp- It did not seem the least bit troubled (sonically) by the unusual and complex load presented by the Quantum 3. As I turned up the volume, it simply reached a point where it quit getting louder and began to gently compress the loudest passages. It also reinforced the observation I made when I brought the amp down to the Cities for Ron's get together and the Yaqin made an awesome showing with the infamous test CD provided by NumbDiver. The transient and peak power response of the Yaqin is quite incredible.

Imaging is very difficult for these speakers in my room. Indeed, I almost gave up on proper imaging as a completely lost cause, and even now, after hours of millimeter adjustments to position and angle, it is only just acceptable- there are, indeed, several bits of masking tape on the floor, lest further tweaking make things worse. The largest offender is the center image- vocalists and the like. Putting on a mono recording of Alice Babs, one would get the impression that her mouth were somehow 3-feet wide. Applying some various (easily reversed) tweaks all managed to exacerbate the effect. Finally, I caught on to the fact that the more severe the tow-in, the better the center imaged. Ultimately, the axis of the midrange domes were crossed just at my head. This turned out to be the best compromise between having an expansive, side-to-side image and a properly proportioned center image.

The depth of the soundstage improved markedly once I had the center properly focused, but I still don't think the IMF's are in any danger of being bested in that discipline.

Off axis, around the basement listening also brought out some interesting contrasts between the Quantum 3's and the TLS-50's.

First, when listening to the Quantum 3's off axis, as I am writing this, there is no doubt that you're listening to a speaker- specifically a box speaker. Not a bad box speaker, by any stretch, but a speaker no less. The TLS-50, by comparison, has a very natural dispersion and radiation pattern that works to very effectively hide the fact that it is a speaker. The Quantum 3 can also seem to accomplish this, but only when you're on-axis and within the 1-foot sweet-spot. The unusual driver arrangement of the TLS-50, which attempts, with success, to emulate a point source works to its advantage.

Cabinet resonance has also reared its head with the Quantum 3. Having gone from the "unresonatable" JVC zero9 (in its Jarve-Falkowski incarnation) to the inherently well braced TLS-50 (with a box-less Magnepan thrown in the mix) I had nearly forgotten what a cabinet resonance sounded like until I heard the very low-level (nearly benign) resonances from Mark B's Infinity Delta system. If the Delta's resonances were benign, however, the Quantum 3's resonance modes are downright lively. There is effectively no bracing internally, and the cabinet is made from robust (but still unbraced) 1-inch thick particle board. The resonances are most apparent from the top of the cabinet, and are strong enough to make a quarter dance across the top if the speaker is fed sine waves of the right frequency; I've found that 230Hz and 460Hz produce the strongest vibrations. Indeed, it is to the point where I would not be totally surprised to see the Quantum 3's get the same treatment the zero9's did (and mirror image them while we're at it... :scratch2:). These resonance modes might even be strong enough that they could be the source of the center image smearing when the speakers are not severely towed in.

That all said, I'm fulling willing to concede that I may be a little bit pickier about the resonance issue (and the imaging issue) after having used speakers that were so superlative in those regards that anything else just cannot fairly compete. And, as for the imaging, I could still be adjusting myself, as they do seem to focus better the longer I listen and subtlety tweak their position.

So, I do think that the Quantum 3 will make a suitable substitute for the TLS-50 as it undergoes further restoration. It may, with time (and proper adjustment, and a better (read "bigger") room) become a permanent part of the stable. Further, it is such a good foundation for a speaker, and such a good concept that I cannot help but wonder of about the possibilities of mating this solid foundation with the sort of unparalleled cabinet building skill that Boy Wonder possesses. It could go from being a great speaker to the level of "Oh my God" that something like the TLS-50 has achieved. Indeed, it is quite a complement to the Quantum 3 that the only real advantage the TLS-50 holds over it at the moment is its far superior imaging ability.

jimreeves
01-26-2010, 02:34 PM
Great stuff once again Mike. I'm surprised to learn that the 3's aren't mirror imaged like the 1's and 2's, guess I should've known by now. I would think that certainly has some effect on their imaging ability as you say.
Box resonance is common to all of the larger Quantums I presume and is next on the to-do list for my QLS1's as time permits.

Anyway, thanks for taking the time to put your thoughts here for the rest of us!

Jim

ejfud
01-26-2010, 03:43 PM
Thanks for sharing Mike. I always like your coverage of such events.

How about some pictures of the beasts?

240sx4u
01-26-2010, 03:57 PM
Ah man, the more I hear these reports the more I desire to move up the infinity chain.

avguytx
01-26-2010, 04:55 PM
Interesting....my Quantum 3's are mirror imaged. But I've seen others in the Quantum line that people owned that weren't mirror imaged, either. I'm sure "left" and "right" designated boxes got to end consumers wrong on occasion. It happens/happened. I love mine. Unfortunately, since life has changed and I'm back in college at 43, I'm not getting to enjoy them now where I'm living since I sold my house in TX last summer. But, they are with my best friend and in his "sound room" ran off *my* Soundcraftsmen stack of gear (A5002 @ 250wpc...recently rebuilt and suh-weet). Mine love power and you can drive them reasonably hard, if so desired, and they just convert that power very, very well. They will be a pair of speakers that remain with me for a long time. I mean, when you only give the price of what you can buy a double cheese burger at Mickey D's from the original owner and in practically perfect condition, how can you go wrong?!?!

motorstereo
01-26-2010, 04:57 PM
Great write up. Thanks for taking the time to do that and post it. Glad to hear you got the miss wired emits corrected. You're right it is a maze inside the q3's.

cdfac
01-26-2010, 05:23 PM
yes, thanks for the writeup and especially the objective comparisons. i'm not surprised by what you're hearing. here are my two cents as a former QLS1 owner:

your substandard imaging is being affected primarily by three things: lack of mirrored drivers, variations between L-pad/pot DCR's with dial in same position (this was causing a shifted vocalist in my case), and need of an XO rebuild. the latter is probably having the biggest effect, which is ironic because you bought them to stand in for your IMFs during their rebuild.

i'm not exactly sure why, but the bigger Quantums all benefit BIG TIME by at least replacing the caps. you can ask everybody that's heard a pair before and after. depth, solidity, and subjective reality of the soundstage improved drastically in my case. now, with the taller tweeter line source and full midrange line source, the QLS1 is always going to image differently than the Q3, but you should be able to improve things a lot if you do decide to put some money into them.

M Jarve
01-27-2010, 10:05 AM
Thanks for sharing Mike. I always like your coverage of such events.

How about some pictures of the beasts?

Thank you indeed.

I would not necessarily describe them as beasts, per se, but they do seem imposing. Their dimensions are actually not too bad, and they weigh only about 90-100-lbs each. The interesting thing about the cabinet design is how shallow the cabinets are in proportion to their width and height- only about 11-inches deep; it increases to 13-inches if you include the grilles and grille stand-offs. The overall appearance is reminiscent of the black monoliths from 2001: A Space Odyssey, but in a woodgrain finish.

The lower opening on the rear is not, as one would suspect, a port opening for the woofer, but rather the terminus of the mid-bass coupler's transmission line.

All the same, here are some pictures:

http://www.audiokarma.org/forums/attachment.php?attachmentid=191829&stc=1&d=1264604655

http://www.audiokarma.org/forums/attachment.php?attachmentid=191830&stc=1&d=1264604655

http://www.audiokarma.org/forums/attachment.php?attachmentid=191831&stc=1&d=1264604655

motorstereo
01-27-2010, 12:37 PM
Those appear to be in very nice shape. Don't you just love those screwball grills though? Everytime I remove mine it makes me wonder what the heck were they thinking of when they designed it.

avguytx
01-27-2010, 06:23 PM
Funny, too, how some Quantum III's had the rear firing EMIT and some didn't. Mine don't have the rear firing tweeter. I'd be interested to know what the actual sound difference there is between the two iterations,

M Jarve
01-27-2010, 07:20 PM
Well, another quick update here. I think I'm starting to finally get the sort of focus from these speakers that I would like to have. Having the day off today, I diddled around with minute changes in position, tilting, and even some room treatments, none of which had a very noticeable difference for the better. So, I eventually reset everything back to where I found the imaging was best.

I sat back, listening to some Alice Babs, when Cerberus, my purebred animal shelter mutt, came and parked himself in front of one of the speakers, with his head obstructing one of the midrange drivers. Alice's voice went from about 3-feet wide down to 2. I chased the dog out of the room and started fiddling with the pots on the back of the speakers. I had, up till then, left them in the approximate center position, as that sounded tonally good. I dialed back the midrange and the mid-bass coupler a little bit (to about the 10-o'clock position), and sat back in my chair.

Hazzah! Alice was now singing between the speakers, not from both speakers simultaneously. I put on some other music (Julee Cruise, Bjrk) and found that the voices now seemed properly centered, and some of the depth that I had lost going from the spooky-good IMF's to the Infinity's was regained.

It's not yet at the spooky-good point, but you can see the lights of that city from where we're at. Knowing now that the L-pads can (seemingly) have an effect on the imaging (while maintaining a subtle control over tone) I think I will experiment more and see if I can dial in something even better.

But, this also means that the last little caveat has been taken care of- even if I cannot improve the imaging over what it is, it is now at least passable, and I should be able to live without the TLS-50's for as long as it takes to get them back to ship-shape.

ejfud
01-27-2010, 08:48 PM
Thanks Mike. I'm not up on the vintage Infinity stuff so it was nice to see what you are talking about.

M Jarve
01-29-2010, 12:42 PM
Well, I think the Quantum 3's have really met their match. There is one track off of the Nine Inch Nails Ghosts CD, track #10 on disc 2, that I've long used to see just how well built a cabinet is. Invariably, anything less than something Bob made fails this test, with the exception being the TLS-50's, which passed with flying colors. This is the sort of track that brings out the worst in speakers, and it did quite a number with the Quantum 3.

As I mentioned (numerous times) above, I'm less than impressed with the cabinet of the Quantum 3- Large surfaces that are not braced with a driver good down to the mid-high 20's makes for very lively walls. When I played the above mentioned track, at moderately high levels (10-15 watts input, as per a rough calculation), I thought for sure the cabinet would self destruct. You could actually see the top of the cabinet vibrate, and the lower portion, below the woofer, was vibrating like it was in some earthquake.

There are two things I intend on trying. The first, and less severe one is to install braces above and below the woofer- this will be complicated by the fact that the input panel is exactly where the lower brace would end up, so I might need to figure on a couple diagonal braces going from just below the woofer to either rear corner.

The second thing, and much more severe, would be to scrap the cabinets entirely and work with Boy Wonder to build new ones, as we did for the JVC zero9's. I'm not keen on this route, however, and (for the time being) neither is Bob, who is not really looking for another project right now.

I do feel compelled to say, however, that as good as these speakers are, the cabinetry employed is of inexcusably poor quality and not very well thought out. Although the materials used (1-inch veneered chip-board) is about par for the time for a higher-end speaker, the lack of any resonance control or bracing, particularly when such large panels are used, is almost negligent. I've owned and seen speakers of much less lineage built to a higher standard, even if they do not necessarily perform as well. This is something unbecoming the "... third-best speaker in the world."

Further experimentation will hopefully allow the speaker to maintain that claim in some basis of reality.

M Jarve
01-29-2010, 01:14 PM
I do want to mention one very strong positive, lest someone think I'm thread-crapping my own thread. The Quantum 3 did pass the 9th Symphony test with one of the best performances I've heard from a set of speakers. It was the closest I've come yet to actually having a seat at Orchestra Hall in my own listening room.

So, their grade, so far, is a solid "B", which puts them in such company as the JVC zero9 (pre-rebuild), Technics SB-X700A(post rebuild), Wharfedale E-50, and Infinity RS-II among other fine speakers. A better/more inert cabinet could possibly bring them to an "A", though.

M Jarve
01-31-2010, 08:08 AM
You know... I find it a bit ironic that I'm fixing up a pair of speakers to use so that I can listen to something while another set of speakers are fixed up. And so it is that I, with the assistance of Boy Wonder, have sought to correct one of the major shortcomings of the Quantum 3. I'll leave you to guess as to what that could be...

In any event, it was rather fortuitous that I decided to do it yesterday, as Bob had decided to "reclaim" materials from an unfinished project, which allowed me some access to nice white oak. I put the new braces around the perimeter of the woofer, three in each cabinet, in roughly a triangular pattern. Chances are that I could have gotten away with two, and I had postulated as many as 4- three seemed like a good compromise.

Two of the braces are below the midline of the woofer, as that is the area that was noisiest, with a single brace at the top-center of the woofer at approximately the dead-middle of the cabinet.

The initial results are very good. There are still strong resonance modes coming from the cabinet, but they are much more benign than the "cabinet about to explode any minute" kind from before the bracing. The flexing I observed on the rear baffle has also been all but eliminated, the exception being at the very highest levels with that one particularly nasty song. If nothing else, it served to move the worst offending vibrations to an SPL level I am unlikely to reach under normal listening, but I may still be in for slight disappointment when I do decide to crank it.

I also think I am going to try something that I found improved the sound of the TLS-50's KEF B-200 woofer, and that is to wrap the stamped metal basket of the woofer in rope-caulk or clay. I don't expect much of an improvement, but the speaker overall is at the point where every little bit helps.

jimreeves
01-31-2010, 09:44 AM
How did you attach the braces? From your description they all mount front to back? Do you feel that bracing side to side is unnecessary?

M Jarve
01-31-2010, 10:04 AM
How did you attach the braces? From your description they all mount front to back? Do you feel that bracing side to side is unnecessary?

Indeed the bracing is front to back- I had considered side-to-side, but the sides of the cabinet did not vibrate all that much to begin with. Indeed, the sides seemed downright dead. The worst of it, and this was common to both cabinets, was the area right below the woofer, and the approximate middle of the rear baffle. The rattling in these areas was so bad that I really did think the baffles might break.

The braces were attached with 1-3/4" drywall screws and wood glue. The braces themselves are 1-1/2"x 3/4" white oak.

The remaining hotspot, almost regardless of level, is the top of the cabinet, which is still lively, but, as I found out through experimentation, the affect is minimal, if not outright inaudible.

bobrown14
02-01-2010, 07:42 PM
All this talk about the QLS-III and it occurred to me to wonder about this:

Mirrored pairs?? Do the tweeters go to the inside or the outside? My pair doesn't have any left/right designations so I'm not sure if they are what was referred to as "mirrored" or not but even if they are not mirrored the tweets are not centered and neither is the mid-bass coupler. So it got me wondering which should be left - the tweets to the inside or to the outside?? Right now I've got the tweets to the inside - I don't know why I decided that was the way they were supposed to be. I just hooked them up that way from the get go. I didn't even think they would sound different if I switched them until I read this thread.

On mirrored speakers; It was my "thought" that speakers built with tweeters and mids off center and each speaker set up opposite, WAS mirrored. Please correct me if I'm wrong on that, and do tell which side the tweeters should be on.... maybe I've got mine all wrong. Although I gotta say - they sound SA-WEET the way they are.

On an another a-side, this past weekend I was getting some falling out something in the sound so I turned one of the l-pads and realized the mids were intermittent. I toke the l-pads apart when I got this pair about a year ago - and cleaned them with DeOxit and sanded the flat metal contacts so that there was no more oxidation. This weekend I gave the pot that was intermittent a shot of Faderlube in the back, took off the knob on the l-pad and gave them a shot (didn't want to remove the woofer and all that) and sure enough the sounds came back to where they should be without any more falling out and to be honest I think they sound A-LOT better, did all 3 pots on both speakers just for measure. It made a significant improvement - again I pulled all six pots and took them apart and cleaned them last year. A shot of Faderlube in from the rear has made a difference in sound for the positive for me, (just sharin).

I'm digging these speakers again. Also - I've not noticed the box rattle that was spoken about here recently. I listen to music that have bass - a lot of bass and bass down lower than traditional electric rock band bass, I'm talking rattling my seat, workbench, widows etc rattle but not the speaker box. I've got the older no rear firing emit version. Oh and amp killer bass..... Yamaha m-2 bit the dust with these but I'm listening to them now with an M-4.

Anyone....?

Cheers,
Bob

M Jarve
02-02-2010, 01:34 PM
I cannot say for sure with regards to the Quantum 3, but most mirror imaged speakers I've seen call for the tweeter to be on the inside edge. Some Wharfedales, my IMF's, the Maggies I've owned, among others seem to use this convention.

jimreeves
02-02-2010, 06:23 PM
Mirrored pairs?? On mirrored speakers; It was my "thought" that speakers built with tweeters and mids off center and each speaker set up opposite, WAS mirrored. Please correct me if I'm wrong on that, and do tell which side the tweeters should be on.... maybe I've got mine all wrong. Although I gotta say - they sound SA-WEET the way they are.
Anyone....?

Cheers,
Bob

According to the Infinity QLS1 manual, the tweets go to the inside. I'm sure it's the same for the Q2's and Q3's if you have a mirrored pair.
http://www.infinity-classics.de/infinity/models/Quantum-series-1976/Quantum-Line-Source-QLS-1/QLS_1_Manual_2_02.jpg

It seems that AKers have a variety of mirrored and not of most models. According to the manual mentioned above, Infinity marked the serial number on the boxes L&R but not the speaker cabinets.

I'd have to agree with the assumption that this was a mixup on the part of the salesperson who sold these pairs when they were new and was unaware that lefts and rights were designated, and new owners who threw out the manuals with the boxes.

If AKers weren't spread all over the map it would be neat to have a "lefties and righties" swap meet!

bobrown14
02-02-2010, 08:08 PM
I cannot say for sure with regards to the Quantum 3, but most mirror imaged speakers I've seen call for the tweeter to be on the inside edge. Some Wharfedales, my IMF's, the Maggies I've owned, among others seem to use this convention.

I have my tweeters on the inside. Seemed natural to me so that's the way I put them. Although I don't remember thinking all that much about it at the time of installation.

If they were not mirrored, is it safe to say the tweeters were the same on BOTH speakers, meaning the tweeters would be on the inside on one and on the same side (outside) on the other one (not my case)?

My bet is they were "supposed" to be sold mirrored. I guess I got lucky. Well actually I know I got lucky with the price I paid (2 Franklins), but they did need to be re-foamed by Bill at Millersound (woofers and one mid bass coupler) and I had to replace one dome mid, cleaned the pots ... no re-cap yet though.

Cheers,
Bob

M Jarve
02-03-2010, 05:13 PM
One more update on the Quantum 3. I've managed to make both the cabinet and the woofer basket as inert as they're going to get. The final bit that needed to be done was to get rid of the cast metal lifters the speakers were on. I replaced them with 1/4" high 3M BumpOns and that got rid of the last bits of rattle.

The cabinets are still quite lively, but at least I don't go nuts every time I put on Bjrk's Hunter, looking for air-leaks, or wondering of a wire in the cabinet is vibrating against a wall.

Indeed, for all but the most extreme levels, their is nary a buzz or rattle to be heard any longer. I cannot say how much the cabinet is or is not contributing to the sound, however, as there are still a couple of "hot-spots" where you can still feel the cabinet vibrating.

Oh! the woes of mere mortal cabinetry! :tears:

jimreeves
02-03-2010, 05:45 PM
If they were not mirrored, is it safe to say the tweeters were the same on BOTH speakers, meaning the tweeters would be on the inside on one and on the same side (outside) on the other one (not my case)?
... no re-cap yet though.

Cheers,
Bob

YES.
BTW, as cdfac said earlier, a recap is a great upgrade. It's relatively cheap, relatively easy with simple soldering tools and talent and can take away a closed-in soundstage that old dried up caps can exhibit. I enjoyed the process actually. :yes:

Mike, it's good to hear that you've got them where you want 'em. I've got to say that I'm envious, but at the same time grateful I don't have your aural sensitivity. :music:

Jim

bobrown14
02-03-2010, 08:00 PM
YES.
BTW, as cdfac said earlier, a recap is a great upgrade. It's relatively cheap, relatively easy with simple soldering tools and talent and can take away a closed-in soundstage that old dried up caps can exhibit. I enjoyed the process actually. :yes:

Mike, it's good to hear that you've got them where you want 'em. I've got to say that I'm envious, but at the same time grateful I don't have your aural sensitivity. :music:

Jim

Re-cap is on the list. Those crossover boards a PITA to get out. I've done it before (not on the QLS-IIIs) and can solder. My speakers don't seem to be as lively as mentioned, I don't have the rear firing tweeters and it made me wonder if that big hole makes the back less rigid. I've got a few things sitting on top of mine and never noticed any movement and I like some bass in my music which is why I've got these speakers.

Cheers,

Bob

M Jarve
02-14-2010, 05:56 PM
Okay- I've been pretty patient with these speakers, but they are still not performing up to the level I think they should.

To hopefully remedy the situation, I've given Boy Wonder free reign to rebuild the cabinets to our standards, which includes mirror-imaging the set. It's also an opportunity to try the new composite hardboard/plywood lanemate material he came up with. The intent is to remain true to the original design, and they will not be severly over-built to the same degree as the zero9's.

Updates as warranted.

jimreeves
02-15-2010, 06:43 AM
This should be interesting. Have you given any thought to enlarging the cabinets and retuning the watkins circuit to a lower frequency? I know the varients were discussed in the watkins white paper sticky thread.

M Jarve
02-15-2010, 04:08 PM
I'm actually pretty happy with the woofer (bass response), and so I don't think I'll be tinkering too much with tuning. One thing I had kind of thought of trying is to install a larger high-pass cap for the 2Ω voice coil. Currently it is 600F, while the lower tuned QLS uses 2000F. I played around with the numbers in a bandpass crossover calculator, but the results were a bit confusing- for instance, the calculator postulated a bandpass of 49 to 60 Hz for the current arrangement (2Ω, 600F, 40mH), which is nonsense. I do intend to replace all the fiberglass with proper Acousta-Stuf, however, as well as install a new set of crossover caps for the tweeters (though that may happen a bit later).

The internal volume will remain approximately the same- I'm gunning for a less than 5% difference (that is, 5% less volume due to bracing), an the midrange TL will likely be of a smaller diameter than it is currently, but that should not make a difference because of how it's arranged.

As for a small update, we rough cut all the panels today and will spend tomorrow gluing them up.

I think, from this point, I'll be updating about these speakers in the DIY forum, as it seems more appropriate.

jimreeves
02-15-2010, 04:36 PM
Wow, coming along fast! Please post a link to that thread here when you update.

BTW, the 2 ohm side of the QLS has a 1400 mfd cap, not 2000. Maybe the Beta/Gamma does.
http://www.infinity-classics.de/infinity/technik/manuals/Quantum_Line_Source_1_technical_sheet.pdf
That was my point in a way, since cabinet volume should have some effect on the tuning circuit you'd want. It's been reported before that Bill Watkins didn't approve of the circuit/volume combination Infinity used in the QLS. I could never make sense of the circuit whether using a bandpass calculator or a narrow bandpass calc.

tubed
02-15-2010, 04:54 PM
Yes, I read somewhere that Infinity sacrificed bass accuracy for the bragging rights for ultra low frequency response. The Watkins woofer sounds wonderful in the smaller Q4 cabinet with solid depth and clarity but is only rated down to 35Hz.

M Jarve
02-15-2010, 05:45 PM
Well, I don't know that they sacrificed much, if anything in the Quantum 3. The bass response goes down pretty deep (very nearly as deep as my TLS-50's, in room), but, of course, I cannot speak to others in the lineup.

The new thread can be found here: http://www.audiokarma.org/forums/showthread.php?t=281998

M Jarve
03-21-2010, 10:51 AM
This is almost deserving of a whole new thread, but I would prefer to keep things neat and tidy, especially considering how I have had three separate threads regarding these speakers going at any given time.

If you read through the posts I've made so far you would likely come to the conclusion that there is little love lost between me and these speakers. But, you would be wrong in that assessment. The harsh remarks I've made about them have been justified and made only because, like a father with an underachieving son, I know they can do better. It is because of this knowledge that I'm disappointed- if they had simply been crap speakers, they would quickly have been passed on and another mark would have been made in the "lesson learned" column of my life. However, I had high hopes for these speakers, as they were intended to make living without my reference IMF TLS-50's bearable, even if only for a while.

The faults I found with these speakers are perhaps more telling of me and my performance expectations than anything "wrong" with the speakers. To many, the Quantum 3 "is what it is", and you take it or leave it at that. For me, however, it "was not what it could be." Thus I, and my ever ingenious partner in crime, Bobfalk, set out to try and correct what I felt was the most egregious shortcoming of these speakers, which was their near/mid field imaging. If we could remedy the over-lively cabinet while we were at it, all the better. The project (experiment, really) turned out both better than I expected and not as good as I had hoped. A happy medium was achieved and the overhaul did indeed mitigate some of the more major issues I had with the set. You can follow that saga using the link in the post above.

Yesterday, I spent the afternoon listening to them and reevaluating them now that they are closer to what they could be, not what they were. First of all, I found almost straight away that I was listening more to the music through them, and not, as I had previously, being distracted by what they were not doing particularly well.

Setup optimally in my room, the imaging capability (now that they're mirror imaged) had improved enormously. Indeed, it comes very close to rivaling the TLS-50 in this regard, though the Quantum 3 still tends to apply a magnifying glass to certain things, growing them out of proportion to the rest of the performance. Still, instruments and vocals are closer to emanating from their respective points in space instead of merely, roughly between the speakers as had been the case. Depth of the sound-field is a now a quality that these speakers posses. Gone is the flat presentation, and in its place is a stage full of all three dimensions. With the TLS-50 as the reference, the Quantum 3 is now 97% of the way there. Bravo!

I originally had no particular qualms about the tonal qualities of the speakers, aside from a slight boxyness to the sound. I had observed that the TLS-50 effectively disappeared and created a credible, if not entirely unshakeable illusion of an actual live performance. The Quantum 3, on the other hand, left no doubt that you were hearing a reproduction of a performance through a loudspeaker. A good loudspeaker, but a loudspeaker no less. I'm pleased to say that, while it's the still the case that the Quantum 3 is not the master of the illusion that the TLS-50 is, it is better than it was by leaps and bounds. The slight colorations that persisted have become almost nonexistent. This is something I credit to having installed bracing in the upper portion of the cabinet, and the slight redesign of the mid-bass coupler's transmission line (larger, longer, and better damped).

As I mentioned in the above referenced thread (the "rebuild" thread), the cabinet resonance issues have not been eliminated. This is something I chalk up to our experimental enclosure materials, but it could also just be the nature of the beast. Still the situation has improved somewhat. The amount of resonance is lower than it had been, and the band(s) that seem to agitate it are narrower and, for my purposes, more benign. It will not pass the Track 10 test of NIN's Ghosts CD 2, but the same could be said for speakers more highly thought of. And it's the reason I use that track as a test, as it does generally bring out the worst in speakers.

On the whole, my opinion of the speakers has changed, and for the better. However, I would still rate them only as a strong B+/weak A- in their current iteration, as I can now say, with some confidence, that if more traditional Falk/Jarve construction techniques and materials had been applied the results would have been even better yet.

M Jarve
03-26-2010, 03:06 PM
I've now had quite a few hours of listening to these speakers on the clock now, and the more I listen, the more I like. I have them dialed in and setup for near perfect imaging (at least as close as it will ever get in my room), and have run a wider variety of music through them.

In particular, the seem to become positively "god-like" when it comes to large orchestral works. Indeed, their dynamic range and and resolving capabilities are uncanny. I've never, and I mean never heard Camille Saint-Sans' Symphony nr. 3 sound so lively, full, and realistic. Backed by the seemingly unending power of my h/k 775 monoblocks, they scaled to the performance magnificently. Of particular notice was how well the piano came through, as every set of speakers I've heard this piece on so far have pushed it almost to the background. Further, among the strings and brass, the piano did not seem to suffer from the soft-edged, wool-blanket effect that seems to affect non-solo piano too easily. Every instrument was resolved with attention to detail and clarity.

Beethoven's Ninth had as good a showing, though the crescendos of the chorus did seem to get a little congested- that could have been the amps starting to run out of power a bit as well, as at that point the "400-watt" (@4Ω) level was just starting to flicker.

Listening to my more standard fare (Radiohead, Bjrk, Portishead, Massive Attack, etc), the performance of the speakers has settled into an area where it is well beyond my expectations. Not perfect, but as good a showing as almost any speaker I've heard. I myself am still adjusting, I think, to their imaging and tonal capabilities. If something like JVC zero9 system is front-row, and the IMF's are more in the center of the hall, the Quantum 3 is somewhere right in between; neither the fully homogenous and congealed sound of the IMF's nor the slightly stratified and analytical reproduction of the zero9's. And, as I mentioned, the IMF's seem to more closely emulate the single, coherent point-source, where as the Quantum 3 is slightly more diffuse, slightly magnifying the vocal ranges (size-wise).

And so, with further consideration, I would put them strongly into the "A-" class.

cdfac
03-26-2010, 03:18 PM
you're going to recap the IMF's, right? it would be interesting to see how the speakers compare if you choose to recap the Q3's too.

my experience with my QLS1's mirrors yours with the Q3's pretty much down the line. if one likes very small scale recordings with pinpoint left-right accuracy, the Quantums may not be for them (although the QLS1's could still work wonders on some Diana Krall), but for medium- and large-scale works, as well as most rock music, they possess some very special qualities. i think you may find that a recap helps out a bit with the overblown imaging, as this can sometimes be due to mismatched crossover points. you might also want to check that the pots are set at equal resistances - even at the same setting, they could be off by several ohms, as i found on the QLS1's.

M Jarve
03-26-2010, 03:35 PM
The IMF's are getting not just a re-cap, but I will be completely dismantling them and replacing all the foam in the TL (it's pretty badly dry-rotted in some places). When it gets to doing the internal baffles, it could get hairy, as there is a chance I could end up breaking them. I'm counting the observation that the internal baffles are just held in with screws and this sort of waxy adhesive/sealant like the front baffle. I'm hoping, among other things, that this takes care of a peculiar notch in the bass response that they currently exhibit.

If after a while longer I decide that I will keep the Q3's as a permanent part of the collection, I might be tempted to recap them then, but, as of right now I have other more pressing matters that I must see to in my listening room, such as getting new tubes for the Yaqin (hopefully before Ron's spring shindig), and re-ordering the correct caps for the IMF's.

Though, I should still ponder whether I will use the same value as the caps currently installed, or if I should go according to the schematic (they don't match- but the schematic also does not show the rear EMIT...).

cdfac
03-26-2010, 03:50 PM
cool. i picked up some RSPM mk IV's which i will recap before too long, but i think the foam looks OK in them, if that's possible after all this time. i'll be interested to watch your progress on the TLS50's. when will you start?

if you recap the Q3's, go by what they have installed. some of the official schematics are messed up, so the differences aren't just from revisions for some models.

jimreeves
03-26-2010, 04:32 PM
Of particular notice was how well the piano came through, as every set of speakers I've heard this piece on so far have pushed it almost to the background. Further, among the strings and brass, the piano did not seem to suffer from the soft-edged, wool-blanket effect that seems to affect non-solo piano too easily. Every instrument was resolved with attention to detail and clarity.
Beethoven's Ninth had as good a showing, though the crescendos of the chorus did seem to get a little congested- that could have been the amps starting to run out of power a bit as well, as at that point the "400-watt" (@4Ω) level was just starting to flicker.


Excellent points Mike and a great description of what I'm hearing with the QLS1's. I've noticed the power-compression issue a few times when things get loud. Surprising how loud it can get before you really notice!


I picked up some RSPM mk IV's which i will recap before too long, but i think the foam looks OK in them, if that's possible after all this time. i'll be interested to watch your progress on the TLS50's. when will you start?

Glad to hear you received the RSPM's Chris, hope they arrived in good shape!
I'll be looking forward to a thread on your project and Mike's with these nice IMF's. Just wish I'd had deeper pockets and more floor space!:thmbsp:

Jim

M Jarve
03-26-2010, 04:56 PM
RSPM's!?!? Great googly-moogly! Those are on my "Holy Grail" list.

The mk. IV is quite a bit newer than my mk. I 50's, and I don't think they used the same foam. I've already sort of started on the 50's, as I have the foam and the wrong set of crossover caps, but I don't think they'll be started in earnest until this summer. They are also due for re-veneering.

cdfac
03-26-2010, 05:42 PM
RSPM's!?!? Great googly-moogly! Those are on my "Holy Grail" list.

yeah, i got super lucky, the price was right and the condition is excellent. Kurtgo picked them up for me (i owe him like 50 favors now!) and is listening to them until we can get them up here from KC.

http://lh6.ggpht.com/_Wbvv9PgiQNI/S6WoCtyKV4I/AAAAAAAANXI/vwAAYO8Jzho/s640/DSC_0002.JPG

http://lh4.ggpht.com/_Wbvv9PgiQNI/S6WoDNVS_FI/AAAAAAAANXM/1OM_kv2re3s/s640/DSC_0003.JPG