Mach One 4024, 4024A, 4029 Information and Upgrades!

[lloydrmc]

Especially since Mach Ones were $200 ($199.50) speakers (albeit 1975 dollars) or $400/pair

T/S ramblings...



My Pioneer S-910 walk all over the VL Mach One, but comparing $1000 speakers to $500 (retail) isn't Realistic (pun intended).

 

[lloydrmc]

As I mentioned on my first post or two on this topic, I don't want anyone to take my work and my commentary on these as being critical of the considerable effort that VL put into improving these speakers. She (or He? Did we ever find out?) most certainly had access to better facilities and equipment than I do, and so if there's doubt to be cast on someone's results, it'd be better cast on mine. However, we don't hear graphs and charts and we don't all prefer the same sound. That said, here's my thoughts on the comparison:

[snip]
If listening pretty close to the speaker, I detect a bit of a "phasey" sound that changes when I move up or down relative to the speaker. As VL mentioned, I think the speaker is best with the L-pads on "-3db".

Switching to the speaker with my crossover, my first impression is that it's smoother and duller. The phasey thing is not there on mine. Not as shouty. Again the loudness contour improves the overall sound significantly, and I suspect that they were designed that way on purpose. .

Not sure what you've done in the intervening years since you posted this. I've read most of this thread, and -in light of your excellent contributions (here and elsewhere in the thread)- I thought you might possibly be interested in my take on some things.

BTW, what you said about the value of my opinions goes (relative to yours, much less VL's) counts even more so for me. YMMV

1) "Loudness Contour" generally bumps up the mids on a receiver/amplifier, so it's no surprise that speakers with a big "hole" there sound better with it on. You may have a point about the speaker being designed that way

2) In a conventional sense, the Mach One tweeter is "sideways" in that the vertical dispersion is going to be wider than the horizontal. I've seen the same (or similar) -sized horns, oriented the same way in other manufacturer's multi (4,5,6) way speakers of the same era. These designs tended to have various drivers placed higher on the baffle, similar to the Mach One. Also note that the tweeter is nowhere near centered on the baffle. This might have to do with polar response (see below)

3) No doubt the more-similar-to-stock VL-modded mid frequency range makes the speaker sound more "phasey", as the mids and tweeters frequency spectrum overlaps quite a bit more with hers, which would effect polar response. Also, as has been noted elsewhere, Mach Ones are NOT good "near field" speakers. BTW,do they blend better if you toe them in?

I think it's a good idea to consider just bringing the leads to each driver to the back of the speaker, so the crossover could be mounted in back, and changed easily. Maybe you could even have standard-spacing banana jacks so it would take mere seconds to plug in a different crossover or change polarity

4) I get where you're coming from with making the mids overlap the tweeters a lot less. Some fairly extensive reading in forums (and related documents) on horns (especially Constant Directivity waveguides/horns) has given me an appreciation for the fact that it's not all about frequency response; dispersion is very important, especially how the dispersion patterns of multiple drivers interact. There are going to be "nulls" (areas where particular frequency ranges cancel each other out) The real trick is controlling how big these nulls are and where along the horizontal plane they are (obviously, the farther the nulls are away from dead center, the better). Note the trickiest part of this interaction is right at crossover frequency

Perhaps the "sideways" tweeter is designed for a better polar response in conjunction with the woofer, while the big frequency overlap the midrange has with a very wide horizontal dispersion (and physically much farther from the woofer) is designed to improve the polar response. That is: the difference in frequencies between the woofer and tweeter may make them interact less.

Wayne Parham actually knows what he's talking about here, if you care to dive in a bit: http://www.audioroundtable.com/PiSpeakers/messages/11054.html

Now: I just bought some gutted 4029 cabinets which had (thankfully) the midrange horns, but -sadly- not the midrange compression driver mounts (or the tweeter horns/mounts, or L-pad mount/tweeter port) My original intent was to do an econowave conversion , and I'm finding that I just don't have the heart to cut them up to do that.

If anyone has read this far has one of each (tweeter & midrange plastic parts/adapters - I don't need the drivers) they could spare for a couple of weeks, I would gladly pay you something to ship it, and then of course ship them right back once I've done some measurements. What I need is the size, depth/placement and exit angle of the metal cone where the each adapter plugs into the rest of the horn, and that plus the dimensions of the tweeter horn. I suppose someone could just take these measurements and post them/PM me. Long story short, I think that -given this information- it would be fairly easy to adapt some modern compression horn drivers, e.g. https://www.parts-express.com/pyle-pds221-titanium-horn-driver-1-3-8-18-tpi--292-2502

 

[lloydrmc]

No, since we are talking about keeping it looking like a Mach 1 with the grill in place. Trust me, easy is not what we are trying for here, it's all about fixing the one problem that never goes away (midrange driver).

Why not just replace the midrange driver then? I have some gutted 4029s which (thankfully) have the midrange horns, but (sadly) don't have the adapters/lenses for the midrange compression drivers (nor -of course- the drivers themselves). Nor any part of the tweeter assemblies. I'm hoping to (at the very least, temporarily) get my hands on one each of the the midrange horn adapters and tweeter horns, or accurate measurements thereof. The best would be to get both entire midrange driver assemblies and tweeter driver/horn assemblies (all of which could of course have blown drivers). I don't want to pay the unobtanium-level pricing for such on ebay. Perhaps I can (eventually) get them on Craigslist, as that's where as much as I do have came from.

The easiest way to improve this speaker would be to find a driver to adapt to the mid horn that would allow it to transform into a two way econowave design. The woofer really does pretty well in an enlarged cabinet, getting a driver that overlaps the woofer better, and also acts as a tweeter would simplify everything. These are just ideas getting thrown around, some of us just like to keep messing with design ideas that can help improve things even more.

Two critical elements of the econowave design would still be missing in that configuraiton: a constant directivity horn (which the Mach One midrange horns most definitely are NOT), and that horn being in close proximity to the woofer so its polar response blends properly with that of the woofer. It appears that what the RS engineers were doing, by putting the actual tweeter "sideways" (more vertical dispersion than horizontal), was to tailor the high frequency polar response in combination with the high frequency overlap reproduced by the midrange driver/horn, to blend in with the polar response of the woofer. Absent the tweeter, and with the midrange horn so far from the woofer the combined polar response would likely be pretty poor.

My modded Mach 4 design pretty much took the VL mods to the end, it really helped them get better, but we still are stuck with the midrange limitations.

Has anyone done an actual, in situ polar response measurement on the midrange and tweeter horns? The problem cited by many is that the mid is too forward. Has anyone tried a zoebel? While that requires an accurate impedance measurement, it would flatten out the rising rate of the driver, which would tame the response, but still allow it to overlap the tweeter frequencies as originally designed.

 

[lloydrmc]

Since the distance between the woofer and the mid was brought up again, I wonder what if? RS Steve, since you made those larger cabs, did you ever consider swapping the position of the mid and tweeter horns? Use pots with longer posts and you could get rid of that tweeter/level control plate altogether. I know it would mess with the classic Mach One look but with a full length grill it would look more understated like the Mac Two. Maybe the drivers would blend together better acoustically and maybe the speaker would have better imaging with a more conventional arrangement. If someone didn't want to build bigger cabs, the could just make a new front baffle for the original Mach One cabs.
Any thoughts on the idea?

The results of such a swap would be unpredictable, it's extraordinarily unlikely that it would be good. The existing placement/orientation of the tweeter/midrange horns seems to be that way to shape the polar response of the drivers.

 

[RS Steve]

I dug up these files posted by Video Lady back while we were doing our mods. It was nice having VL back up the findings with documents, maybe these can help answer any questions.

 

[lloydrmc]

I dug up these files posted by Video Lady back while we were doing our mods. It was nice having VL back up the findings with documents, maybe these can help answer any questions.

View attachment 960741

That answers that! The mid doesn't need a zobel, and the tweeter clearly does.

 

[lloydrmc]

Cool. I have one working spare [midrange driver] myself.

Meanwhile, nearly 2 1/2 years later: Do you suppose I could borrow your magnet-less [non-functional] mid? I would be happy to pay shipping both ways. I have a pair of gutted 4029s that have the mid horn flares and grilles, but no driver/adapter parts (and no tweeter parts at all, or L-Pads). I plan to adapt a different compression driver e.g. https://www.parts-express.com/pyle-pds221-titanium-horn-driver-1-3-8-18-tpi--292-2502 and I was hoping to measure the shape/configuration of the big, plastic, adapter that the mid driver attaches to.

 

[lloydrmc]

I just checked DATS and my 4029 file and the mid has a sudden sharp peak at 2.5k that is consistent with all the mids I checked.

Surely a notch filter could reduce this. Or just adapt different compression drivers to the horns.

 

[lloydrmc]

The tweeters are pretty bad, though. They don't bring much to the table. They cover a lot of the same ground as the midrange and don't really add anything on the high end. Adding felt to the pole didn't really change anything. I'll probably try to roll the mid off around 11-12K, put a 3rd order filter on the tweeter and let it take over from there.

Something I've learned in learning about econowaves is that frequency response isn't everything. Yes, the tweeters cover much of the same frequency, and they're closer to the woofers, and their horns are "sideways" such that their horizontal dispersion is narrower than the vertical. where the midrange horns are the more usual, opposite configuration of the mid horns (horizontal dispersion much wider than the vertical) Clearly this isn't accidental. The way the horns -covering much of the same frequency spectrum- are oriented likely has something to do with the polar response. It could be that having the tweeter closer to the woofer, and operating at a much higher frequency, could have to do with blending the outputs of the woofer (and especially) the tweeter, thus minimizing nulls in that region.

Other speakers of the same era also had a "sideways" horn driver e.g. http://img.auctiva.com/imgdata/1/2/9/3/8/0/6/webimg/804031468_tp.jpg

 

[lloydrmc]

Yes. However, are you asking about porting "rather" than enlarging the volume (using the mid chamber)? If so, hard to say which would add more bass. I'm concerned that the bass would be more boomy with the port, than expanding the volume.

No way porting a too-small-to-be-a-sealed cabinet is going to work well at all. The optimum ported cabinet for any given driver is anywhere between a bit and quite a bit larger than the optimum sealed cabinet. The tradeoff is bass extension (cabinet F3) and efficiency. The F3 in a sealed cabinet is always higher than the FS (resonant frequency of the driver). A vented enclosure can be lower. See below. FS in this case is 22 Hz

With a "high Q" driver like the Mach One woofer, it's "quite a bit" larger. Here's the recommended cabinet sizes per Parts Express for their Mach One replacement woofer:
Sealed Volume:7.54 ft.³
Sealed F3 35 Hz

Vented Volume:23.32 ft.³
Vented F3 17 Hz

23+ cubic feet is ENORMOUS As a comparison, a full-sized "Marty" subwoofer (2' by 2' by 4', with 18" driver) is something like 7 cubic feet

 

[lloydrmc]

[snip]. When I move onto my next project I likely will not be using the mid horn, unless I can come up with a way to tame it sufficiently. As you crank up the volume that bugger really begins to put out. I would think either a more behaved driver or less aggressive horn assembly could do the trick. That horn is impressive looking, but may add too much in efficiency to the driver.
A zobel perhaps http://www.wavecor.com/html/zobel_networks.html
.

 

[lloydrmc]

I think all that's needed is a flange to 1" threaded adapter.

Parts Express has 1-3/8" adapter types but I see no 1".

I find horn driver sizes confusing. The standard, smaller threaded size is 1 3/8" by 18 [threads per inch]. The 1" refers to the size of the voice coil

 

[lloydrmc]

http://meniscusaudio.com/gasket-tape-100ft-p-844.html

I used this, the 3/8" wide width cut down to 1/8". worked perfect.

you can also buy it from them by the foot.

Updated link/URL: https://meniscusaudio.com/product/gasket-tape-100ft/

 

[lloydrmc]

[snip]. My problem has always been with the mid being on top, I feel it needs to be closer to the woofer to blend the crossover points better. With the tweeter in the middle it just sounds too seperate until cranked up. I wish I had a doner cabinet to make a new baffle with the tweeter on top, I would like to test it out and see what the impact would be before building new cabinets. I know this would take away from the factory look but I'm after getting better sound.

The midrange and tweeter frequency range overlap quite a bit. The tweeter is "sideways" (the horn is wider in the vertical dimension, so vertical dispersion will be wider than horizontal). This could be an attempt to blend the polar response more smoothly with the woofer (with fewer nulls). Also note that the tweeter is nowhere near centered, this probably has to do with blending polar response with the conventionally-oriented tweeter, which (again) overlaps frequency response quite a bit with the midrange.

 

[lloydrmc]

Parts Express makes both a 4 and 8 ohm replacement. Write up on the 4 ohm claims its for the 4029. They've been incorrect on their write ups before though.

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=290-182&FTR=mach 1 4 ohm

Replacement Woofer for 15" Realistic Mach One 4 Ohm
Brand: Parts Express

Updated link (now 8 ohm) https://www.parts-express.com/parts...ofer-for-15-realistic-mach-one-8-ohm--290-184

 

[RS Steve]

One of the two pairs of modded Mach 1's I created are still being used daily during the work week at my friends cabinet shop. These babies have taken a few years of serious abuse, not one problem has diminished their performance.

 

[lloydrmc]

I was hoping someone could help me. I did all the Tier one upgrades for my Dad's Mach Ones. Upon listening to them I noticed one of the speakers' mid range didn't sound right. It sounds almost the same as the tweeter. Im not sure if its the felt under the mid range I added or if It was an issue with the recap. I did the unwind on all the coils and replaced with capacitors recommended on page 55 of this thread.

I checked my connections, they all look correct. I checked the impedance of the mid range tweet and it also looked fine. Any recommendations on what to check next?

Please forgive me if this sounds simplistic. Fundamentally, troubleshooting is very simple.
My guess is it's the crossover wiring/component placement. That being said, good way to begin troubleshooting the problem is to swap your mid drivers side for side. If the problem follows the driver, it's the driver. If the same speaker doesn't sound right, it's the crossover.

If it's the mid driver, I'm out of information. I know there's some subtleties in how they're assembled. Or possibly the diaphragm. I can't be more help than that; I'm way out of my depth here.

 

[lloydrmc]

Not sure what you've done in the intervening years since you posted this. I've read most of this thread, and -in light of your excellent contributions (here and elsewhere in the thread)-

Here's Wayne Parham's take. Unlike me, he actually knows what he's talking about.(emphasis mine)
"As you get close to the null angle, the phase between woofer and tweeter becomes nearer to 180 degrees. This causes reduction in amplitude in the crossover overlap band at the null angle. As you move further off-axis the amplitude will rise again if the HF horn has angular coverage past the null angle. Likewise, above the crossover point, there are no nulls because the woofer is not making sound to interfere with the tweeter. So above the crossover point, the horn sets the radiating angle. Here again, if the horn provides a vertical pattern that is taller than the null angle, then the pattern will dip at crossover and rise again at higher frequencies."

Again, since it's the tweeter that's in closer proximity to the woofer, and the it doesn't operate anywhere near the frequency of the woofer, there aren't going to be nulls caused by interference right at the crossover point where both drivers are producing the same frequency range (which is good, because the tweeter horn is "sideways", so the dispersion is wider on the vertical plane).

The midrange is physically much farther away, and horn loaded to boot so nulls at the crossover should be minimized.

Wayne (http://www.audiokarma.org/forums/index.php?members/wayne-parham.6525/) -who is a bonafide expert on speaker design- has chimed in elsewhere in that same thread. Every time takes the time to chime in, it's pure gold.

Here's the link to rest of post quoted above.
http://www.audiokarma.org/forums/in...econowave-speaker.150939/page-23#post-1914683

 

[paysonmark]

I am in the process of re capping and cleaning my 4024's and nova 7's. I have measured the caps with a decent LCR meter, and some of the caps are still very close to factory specs. Can I reuse them in other projects or always use new caps for xover builds, thanks
(for the mach ones I'm using the new values in this thread, and nova 7b 15uf non polarized electrolytic)

 

[rcmtnet]

Did anyone ever compile the 4024a 4029 update process into a pdf document. Early on downloads are unavailable.