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They're at it again! Re-imagining the Infinity Quantum 3.

M Jarve

Audio Geek and NGE Freak
As I implied in another thread, the Infinity Quantum 3 is a good speaker capable of great potential. The tonal qualities, dynamic range, transient response, and so on are, in my estimation, very good. Indeed, it has the potential to knock my current #1 speaker (IMF Studio TLS-50) out of its long held throne. It would take a very good speaker indeed to do that, but the Quantum 3, as it is, cannot achieve that.

The weakness of the Quantum 3 is not in its drivers, crossover, or design (well, maybe a little) but rather in its so-so build quality and inattention to little details (apparently rectified in later versions). For instance, the cabinet is, to say the least, lively, and to say the most, awful. Perhaps that's too harsh, but I am used to a higher standard. Additionally, the version I have is not mirror imaged, although apparently there were mirror imaged versions sold, notably without the rear EMIT.

Even still, I managed to make the existing cabinet as sonically inert as possible, and I fiddled with location for (literally) hours on end, attempting to regain the imaging I had lost when I swapped out the TLS-50 for the Quantum 3.

Imaging, really good, holographic, pin-point spooky-good imaging is something that I have found I cannot live without. It's almost like listening to a well known recording on a system (amp and speakers) that can reproduce truly deep bass. You never knew what you were missing, but once you hear it, it's difficult to hear it any other way. The Quantum 3 was capable as imaging as well as any large speaker can in my room. But, its dimensional resolving power was outclassed by orders of magnitude by the TLS-50. Indeed, there are few speakers that can approach the TLS-50 in this regard and I have yet to hear a set that can actually surpass it. They throw a wide, deep, and exactly proportioned soundstage that is almost unsettling in its accuracy. The Quantum 3, could not do this... Rather it could, but only when the speakers were arranged in such a way that is impractical in my room, and caused faults to appear elsewhere. Placed in the location that had the least amount of problems caused vocals to sound unnaturally large (like a mouth, three feet wide), and prevented the image on the right side from extending past the right-speaker (quite unlike the left channel).

So it was that last night, almost in a fit of anger, I pulled the TLS-50 out of the corner they were tucked into and pressed them back into service. Although the Quantum 3 outclasses them in dynamic range and impact, they brought back the perfect soundstage I missed so much. Given the choice between the Quantum 3's "Big Speaker" performance, or the eery "life" of the TLS-50, I would take the TLS-50.

But, while I was cooling off, I put in a call to Boy Wonder and asked how quickly he could whip up a set of new cabinets for the Quantum 3.

Today wood and glue were bought, and panels rough-cut for a modern take on the Quantum 3. They will be stronger, more inert, and mirror imaged. All the original drivers and design elements from the original will be maintained, including the dimensions and proportions, as well as drivers, crossover, and driver layout, although the set will be mirror imaged. Indeed, I believe it is the lack of mirroring that has lead to such poor soundstage in my room.

The cabinets will be constructed in a more ordinary manor- that is, without our typical (until now) finger jointing. However, the material used will be somewhat experimental. It is a laminate material of alternating layers of hardboard and flooring underlayment. Each layer is approximately 1/4" thick, with each panel being made of 5 layers (two of the flooring underlayment, three of the hardboard). The idea is to have the underlayment provide strength and dimensional stability (the two layers have their grain perpendicular to each other), while the hardboard provides high density mass and additional strength. This is a material Bob though up when I first started designing the Compacts (re-christened the Stripes), and we glued up some samples to play with. Indeed, it is an exceptionally strong material and should make a fine cabinet, but the proof will be in the pudding, as it's said. I will post a picture of the sample block some other time (when I find the battery for my camera), but I will say (in addition) that it looks pretty good to boot.

As usual, pics and updates to follow as time and events allow.
 
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As to my post from your "speaker" thread....the sacrifice of accuracy for low frequency response was in reference to the QLS-1.
I think its kinda interesting Infinity used the same single driver for all the Quantum line and were able to engineer the systems to work wonderfully. The cabinet volume of the QLS 1 is 3 1/2 times larger than the Q5 and almost twice the volume of your Q3. Perhaps the Q3 cabinet volume might be the best for the Watkins driver, not to big nor to small?
 
It almost seems to be becoming a spring tradition.

unemployed {reads unemployable, apparently} carpenter+winter=speaker cabinets.

And in all honestly I wouldn't use my cabinets as foundations for anything larger than a double wide :D

--Bobfalk
 
Here is a pic of the sample block, which is a little different than what we actually did. As I mentioned, we went for 5 layers, with an additional hardboard layer.

When we were handling the pieces today, I was reminded of slate due to the hardness. Indeed, this is not as "dead" a material as MDF, but it seems very much stronger, and any resonant mode it has should be quite high in frequency and therefor relatively benign.

Speaking of the project, we finalized (more or less) the design today. Because the midrange TL will be taking up more volume than the original, and because we're using but-joints and cleats, I opted to make the cabinet deeper by roughly half an inch to try and recover some volume. By my calculations, however, we should still be within 5% of the original volume. This change in volume should also be somewhat negated by the fact that the original fiberglass bats that served as dampening material are being replaced by Acousta-Stuf polyfill.

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Any particular reason you're using the laminate rather than MDF? The Q3 isn't that big a box, I wouldn't have thought higher strength in the material would have trumped the acoustic inertness of MDF. Not a criticism, I think the laminate looks cool, was just wondering what your thinking was on this.

David
 
Any particular reason you're using the laminate rather than MDF? The Q3 isn't that big a box, I wouldn't have thought higher strength in the material would have trumped the acoustic inertness of MDF. Not a criticism, I think the laminate looks cool, was just wondering what your thinking was on this.

David

The main thing is to test this stuff out. Ever since I managed to get the JVC's to admit they had drives inside the cabinets I was thinking of how to counter it. So last year Mike and I made up some samples of this stuff... we shouldn't be allowed free time. We had quite a bit of fun beating the samples to death and concluded that it would be fun to see how it rated compared to our normal 1.5" MDF speaker cabs. The "Stripes" were going to be built out of this mystery material but Menards didn't have tempered hardboard on hand so the STRIPES were made from mere plywood.

The mystery material is a lot stiffer and stronger compared to the MDF but how it will do sonically is anyone's guess. I'll say this I would sooner punch the JCV's than these suckers.

We'll see how they sound.

--Bobfalk
 
"This change in volume should also be somewhat negated by the fact that the original fiberglass bats that served as dampening material are being replaced by Acousta-Stuf polyfill."

I don't believe I've ever come across an Infinity speaker system that used fiberglass batts as original cabinet filler:scratch2:
 
Very interesting project! :thmbsp: I'm always interested in new experiments, and will be following this one closely!

:lurk:
 
Break out the weight set!

I had the opportunity to hear the "Stripes" over at Peter's the other day, very remarkable speakers. I don't know how you guys hit on that combination of drivers and, more elusive, the driver orientation on the baffle, but they really delivered in a lot of ways. I think the larger, horizontal baffle is a lot of the magic. Good job!

About the new panel material: I have been researching constrained layer dampening, of recent, and ran into an article on CLD that uses roofing felt as one of the layers. It provides a very inexpensive solution for raising the dampening properties of cabinet panels. Found the link: cabinet construction, scroll down to the "Panel vibation damping experiments".
 
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Some more progress and pics. The baffle extension for the woofer was made today, and the panels were cut to their final size.

Additionally, the jig for the driver layout was made and so the cutouts should be finished tomorrow (save for the rear baffle).
 

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I see you two are at it again ;)

Looking good Mike and Bob! I love the layup you did for the cab material. It's going to be interesting to see how it works out in that regard.

Might you have these ready for travel say,,, by May 22nd?

RC
 
I had the opportunity to hear the "Stripes" over at Peter's the other day, very remarkable speakers. I don't know how you guys hit on that combination of drivers and, more elusive, the driver orientation on the baffle, but they really delivered in a lot of ways..

Check out the thread for them Mike sort of explains how they came to be
http://www.audiokarma.org/forums/showthread.php?t=234038


I see you two are at it again ;)

Looking good Mike and Bob! I love the layup you did for the cab material. It's going to be interesting to see how it works out in that regard.

Might you have these ready for travel say,,, by May 22nd?

RC

Ron are you suggesting you may be panning another get-together? Should I started marinating the steaks yet?

And I'd hope they are up and running by then... if they aren't either Mike or me will have died a very violent death :boxing:
With any luck they should be functional within a week. We'll see.

--Bobfalk
 
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