While working on extracting and cleaning the pots, and reinstalling (gee, soldering is fun in a confined space, isn't it :no: ), I noticed a discrepency in the real speaker vs the schematic available here (http://www.infinity-classics.de/infinity/models/Quantum-series-1976/index-Quantum.htm)

I've attached a pic of the schematic here for reference.

On the tweeter circuit, the schematic shows the 5 Ohm 25W pot and the capacitor switch, in the leg attached to the positive terminal of the tweeter (solid blue wire). This leg is shown attached to the negative speaker input.

In reality, at least on the one speaker I'm working on, the pot and cap switch are in the other leg, wired between the the fuse (positve input) and the negative terminal of the tweeters (blue/black wires).

I don't think it makes a lot of difference in the operation...or does it? Sure makes you keep going back and forth checking wires and the schematic over and over again though (I thought I was losing it :screwy: ).

I would be interested to hear from any other Q2 owners who have been into the wiring or are presently into it, whether the same thing was noticed.

Another interesting observation (well, to a Q2 owner anyway) is that the tweeters and the mid-bass coupler are wired out of phase to the rest of the drivers. :scratch2:

Seems strange to me I always thought you should maintain polarity. Several years ago I bought a nice center channel speaker for my home theater setup. Got it home hooked it up, got crackly distorted treble. Figured bad tweeter, called where I bought it I got the last one, so I called the manufacturer told them, they sent me a new tweeter went to put it in old one was hooked up backwards :scratch2: , switched wires around sounds great to this day and I have and extra tweeter if I ever need it. :music:

Can't say what's going on, but I seriously doubt that the polarity is actually off. The Quantum series was designed to be both time and phase aligned via both physical driver positioning (phase ring on woofer) and crossover design. Crossovers can cause a phase shift, perhaps that which occurs for the tweeters and midbass is sufficient to have caused a 180 degree inversion. The older Tannoy DCs' crossovers had that happen, but the effect was physically countered with the tweeter driver being situated 1/4 wavelength behind the woofer cone and being connected inversely. Eh, I'm guessing here, but I am certain the drivers are not mixed up like that in actuality.

- JP

Common practice on 2nd Order networks to wire the tweet bassackwards.

Can't say what's going on, but I seriously doubt that the polarity is actually off. The Quantum series was designed to be both time and phase aligned via both physical driver positioning (phase ring on woofer) and crossover design. Crossovers can cause a phase shift, perhaps that which occurs for the tweeters and midbass is sufficient to have caused a 180 degree inversion. The older Tannoy DCs' crossovers had that happen, but the effect was physically countered with the tweeter driver being situated 1/4 wavelength behind the woofer cone and being connected inversely. Eh, I'm guessing here, but I am certain the drivers are not mixed up like that in actuality.

- JP

JP,

Do you mean to say you do not believe the schematic?

I did trace the tweeter circuit to the + / - sign on the tweeter diaphrams, and the schematic is correct. The + on the tweeter is wired to the Neg speaker terminal.

Haven't done the same on the Mid-bass, but since it is "tubed" directly to the back of the cab, perhaps the inversion is to send the wave backwards to be reflected off the back wall????

Would be nice to have the designer on line to discuss all this theory with wouldn't it ??

Common practice on 2nd Order networks to wire the tweet bassackwards.

Why?

JP,

Do you mean to say you do not believe the schematic?

I did trace the tweeter circuit to the + / - sign on the tweeter diaphrams, and the schematic is correct. The + on the tweeter is wired to the Neg speaker terminal.
I do believe the schematic and while you were tracing it, I was as well while swapping drivers between cabinets this afternoon. I was saying that I believe it was intended to counter things the crossover did to the phase. So, I said the schematic is accurate, but it doesn't represent the final polarity of the sound coming from the drivers.

Haven't done the same on the Mid-bass, but since it is "tubed" directly to the back of the cab, perhaps the inversion is to send the wave backwards to be reflected off the back wall????
Not really, the midbass is placed into a transmission line (http://www.t-linespeakers.org/) that doesn't quite work like a dipole as you suspect.

Would be nice to have the designer on line to discuss all this theory with wouldn't it ??
One of them is nearby, Arnie Nudell is in Seattle, I believe, working on his designs for Genesis (www.genesisloudspeakers.com). If someone could figure out a way to make an appointment to visit with him and discuss designs, I'll go and do it (but only if I can also con him into letting me hear some Genesis 1.1s).

- JP

I do believe the schematic and while you were tracing it, I was as well while swapping drivers between cabinets this afternoon. I was saying that I believe it was intended to counter things the crossover did to the phase. So, I said the schematic is accurate, but it doesn't represent the final polarity of the sound coming from the drivers.- JP

Gotcha! My misinterpretation.


Not really, the midbass is placed into a transmission line (http://www.t-linespeakers.org/) that doesn't quite work like a dipole as you suspect. - JP

Need to look into this some more. :scratch2:


One of them is nearby, Arnie Nudell is in Seattle, I believe, working on his designs for Genesis (www.genesisloudspeakers.com). If someone could figure out a way to make an appointment to visit with him and discuss designs, I'll go and do it (but only if I can also con him into letting me hear some Genesis 1.1s). - JP

:D

Why?
Because a 2nd order crossover reverses phase by 180 degrees.

Based on the schematic, it would appear to me that the filters are all first order. It also appears that the woofer circuits include a hi-pass filter and the circuit for each v/c is different. Okay Mr. Infinity Quantum expert (JP :D ), explain all this to me. - Mark

It also appears that the woofer circuits include a hi-pass filter and the circuit for each v/c is different. Okay Mr. Infinity Quantum expert (JP :D ), explain all this to me. - Mark
How 'bout I just let Infinity explain it?

http://www.infinity-classics.de/infinity/models/Quantum-series-1976/Quantum-Line-Source-QLS-1/QLS_1_Brochure_02.jpg

Pretty cool, huh? What the brochure leaves out is that this woofer, thanks to the dual VC design digs down much, much farther than one would expect even from a 12" woofer. Of course, this comes at the expense of being a bit hazardous to amps (the impedance at resonance is actually ~1.8ohms). I wonder why, aside from the amp and patent issues, others haven't utilized dual VC woofers in a similar manner with their designs?

- JP

I just knew you'd have the answer :thmbsp: ...interesting stuff. - Mark

I wonder why, aside from the amp and patent issues, others haven't utilized dual VC woofers in a similar manner with their designs?

- JP

Hey, check out my unpopular thread on the Pioneer DSS-7.....They've got some duallies. :thmbsp:

I just knew you'd have the answer :thmbsp: ...interesting stuff. - Mark

It would more interesting if I could get mine up and running and have a listen to all that theory :D

It would more interesting if I could get mine up and running and have a listen to all that theory :D

Just send them to me. I'll fix you right up.....somehow.

Just send them to me. I'll fix you right up.....somehow.

Mark, appreciate the offer....somehow :D

Actually, I think I'll have em beat once I get the resistors in,,,,,unless something else shows up. It's getting close.

Hey, have you ever heard a set of Quantums? 1,2,or 3 s?

You are probably aware by now of several variations in the Quantum 2 systems sold. Some had a rear EMIT tweeter--smaller than the front three EMIT's. Some had plugs to change the crossover frequency for tweeters and mids. I've seen claims that some were sold that were NOT mirror image pairs with the tweeters on opposite sides of the front of the cabinet. The pair I have has only the crossover frequency plugs without the rear EMIT's but they are a mirror image pair.

I also have a pair of Quantum 3's, which use the same components as the Q2, but only one midrange dome and two EMIT's.

I will be surprised if you aren't thrilled with the sound quality of these speakers. The EMIT's put out seemingly unlimited range of highs. The woofers go well into the 20 HZ range. Overall, they are very neutral-sounding. Often, they sound startingly real with program material you have heard on other lesser systems. I am driving mine now with a Pioneer 1014, which surprisingly handles them very well. They output greater levels when used with my Hafler DH500, though. The first sign of overdriving my pair is the woofers. They will bottom with strong low-frequency input. Mr. Watkins told me this was a problem with the Quantum 2's and worse with the QLS-1 due to excessive cabinet volume. He suggested filling the cabinet to reduce volume by about 1/3. This, however, would reduce very low frequency output. I chose to keep them stock.

Let me know how you like them. Also, if you experience the woofer cone bottoming. I have noticed this does not happen on the Quantum 3's. They sound very much like the Quantum 2's.

Good luck!!

You are probably aware by now of several variations in the Quantum 2 systems sold. Some had a rear EMIT tweeter--smaller than the front three EMIT's. Some had plugs to change the crossover frequency for tweeters and mids. I've seen claims that some were sold that were NOT mirror image pairs with the tweeters on opposite sides of the front of the cabinet. The pair I have has only the crossover frequency plugs without the rear EMIT's but they are a mirror image pair.

I also have a pair of Quantum 3's, which use the same components as the Q2, but only one midrange dome and two EMIT's.



bocoogto,

check out my little database I was trying to put together earlier. I should try to keep this going. It might prove interesting after a while. Yup, there were a few variations.

Want to provide the serials for the Q3s and there particulars?

(7100178 and 7100179) - Non mirrored with rear emit - made in Sept/Oct 1976.

(7103168 & 7206395) - mirror imaged Q3's.

(7104061 & 7104520 - Mirror imaged Q2's , no rear emit, bi-ampable, switchable tweeter xover points - Kencat's.

(7209404 & 7209405) - NON-Mirrored Q3's

(7207664 & 7206975) - Mirrored Q3's - bought new in 1979

(1020711 & 1020712) - non-mirrored Q2's, rear EMIT, no biamp - Charivari's

(7100586 & 7101282) - Mirror imaged Q2's, No backside tweeter - Walllly's

(7101797 & 7102422) - Mirror imaged Q2's, No backside tweeter, and biamped - Bocoogto's

Hmm, my serial numbers still look very out of place in that list, but I have verified that they are original Infinity S/Ns by comparing the sticker, font, etc to that on my new cabinet and they're a match.

Here are the differences I've noted by having my unusual 102071X s/n Q2s side-by-side a single conventionally numbered cab.

1020711 & 1020712:
Rear EMIT (4x4 arrangement on slots vs. 2x8 of front EMITs), fibreglass batting as fill, adjustable tweeter crossover frequency, stacked Callins NP (black and red) electrolytic capacitors in LF crossover, Superior electronics (yellow) elsewhere, not biampable, not mirror imaged (left channel arrangement only). The crossovers are mostly mounted to a board in the base with just the pots on the connection plate. Woofer phase rings are 1 1/4" tall. The base board is not beveled and is held on to the cabinet by four screws. The cosmetic groove on the front is 1/8" wide.

7103657:
No rear EMIT, polyfill, adjustable tweeter crossover frequency, large single can caps in LF crossover, Superior Electronics (yellow) elsewhere, biampable, likely mirror-imaged (right channel driver arrangement). The crossovers are mounted to a board with a large, square hole in the middle and mounted over the connection plate. Woofer phase ring is 5/8" tall. The base board has a 1/4" bevel and is held to the cabinet with just two screws. The cosmetic groove on the front is 1/16".

- JP

Hey, have you ever heard a set of Quantums? 1,2,or 3 s?

Never had the pleasure, Kencat, but I did get to hear Army's RS 2.5's driven by his G-22000 (I think that' it) several months back.....most impressive! - Mark

Never had the pleasure, Kencat, but I did get to hear Army's RS 2.5's driven by his G-22000 (I think that' it) several months back.....most impressive! - Mark

Well, if you ever have the chance to make it up this way, you have an invite to stop in for a visit. Only 1.5 hrs from Toronto if that was a destination. I know it's a far way's off, but you never know :D

7103657:
No rear EMIT, polyfill, adjustable tweeter crossover frequency, large single can caps in LF crossover, Superior Electronics (yellow) elsewhere, biampable, likely mirror-imaged (right channel driver arrangement). The crossovers are mounted to a board with a large, square hole in the middle and mounted over the connection plate. Woofer phase ring is 5/8" tall. The base board has a 1/4" bevel and is held to the cabinet with just two screws. The cosmetic groove on the front is 1/16".

- JP

JP,

Serial is pretty close to mine and features sound the same. Pic look familiar?

Yep, very similar, nearly identical, except that small silver cap is another yellow 'un. There are differences in the crossovers of my older, consecutively numbered Q2s even, but it would seem Infinity standardized the design towards the end.

- JP

JP (and anyone else as well),

Is it a GIVEN that these electrolytics (caps) are all deteriorated to some extent?

Should they be replaced to get the speakers back to original sound? This looks like an expensive endevour :sigh: , but, if need be ,then so be it.

Good question, I've been wondering that myself, though, I've planned to go ahead and recap anyways at least as a precaution. My guess would be that the caps for the tweeters, mids, and maybe even midbass should be recapped. Of what material (polyprop?) to use and what brand to choose are good questions. I have some 20μF polyprop WIMAs on the way that I was planning on using for the mids with a 0.4μF bypass cap to get to the needed value, but I'm just hoping that these are good caps.

Now, as to those two monsters on the Watkins weighing in at 700μF and 1100μF, I don't know. Good polyprops stacked to reach that size would be an extremely expensive option, foil in oil and whatever exotics are out there would be huge and make even a millionaire balk at the price. So, I guess electrolytics are the only option here, but what brand, I know not.

Please, someone chime in with the answers to these questions, there's at least two of us who want to know.

- JP