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Infinity Quantum 3

And thus, the saga continues.

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.
 
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?
 
jimreeves said:
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?
Click to expand...

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.
 
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
 
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.
 
bobrown14 said:
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
Click to expand...

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/inf...antum-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!
 
M Jarve said:
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.
Click to expand...

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
 
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 Björk'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:
 
bobrown14 said:
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
Click to expand...

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
 
jimreeves said:
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
Click to expand...

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
 
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.
 
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.
 
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 600µF, while the lower tuned QLS uses 2000µF. 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, 600µF, 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.
 
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.
 
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.
 
The Quantum 3, revisited.

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.
 
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-Saëns' 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, Björk, 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.
 
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.
 
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...).
 
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