Ok that all sounds very exciting, but a common negative of small ports is chuffing. I see that we have 4 of them, but they look really small, like 1.5 to 2 inches. Have you done some high volume near field testing and sweeps to see if it has audible chuffing or odd noises at any particular frequency?
By the way, since you use it for setup and since you feel it is far superior to other options (and because it's free) I've also migrated to the use of HOLMimpulse for my measurements. I think this should help you better interpret my measurements better, which should also help me become better at taking measurements.
By the way, since you use it for setup and since you feel it is far superior to other options (and because it's free) I've also migrated to the use of HOLMimpulse for my measurements. I think this should help you better interpret my measurements better, which should also help me become better at taking measurements.
"...enclosure construction. For instance, materials used, is there CLD,"
A properly built sub enclosure will have its first panel resonance well above the operating range, so there's no point in damping.
"They are small for damping, thus elliminating the need for foam to dampen the resonances. "
Need for damping indicates a too high driver Q.
Also, although an ideal spring/mass/damper system has viscous damping, I believe in a loudspeaker the behavior is nonlinear because it changes from laminar to turbulent at high levels for any practical diameter.
If that were not the case, we wouldn't have to be concerned with port compression.
A properly built sub enclosure will have its first panel resonance well above the operating range, so there's no point in damping.
"They are small for damping, thus elliminating the need for foam to dampen the resonances. "
Need for damping indicates a too high driver Q.
Also, although an ideal spring/mass/damper system has viscous damping, I believe in a loudspeaker the behavior is nonlinear because it changes from laminar to turbulent at high levels for any practical diameter.
If that were not the case, we wouldn't have to be concerned with port compression.
The driver Q is about .25 - about as low as possible. In a bandpass design the Q that you have to worry about is the Helmholtz resonance Q of the front chamber. To make a small box, this Q will be high and needs to be dampen. Yes, there is some port compression due to the increase in resistance at higher velocities, but thats not a bad thing. At higher SPLs the Q goes down and the output level drops slightly, maybe 3 dB max. But at higher SPL we are far more sensitive to bass so a drop in bass level is not a bad thing and in fact could well be a good thing. I have been using this type of sub in my theater for about five years and I find it very desirable. The bass never seems to get of of control no matter how loud you make it.
These are NOT subs that I would use in a pro setting or a club where MAX bass output is a requirement. They are Hi-Fi subs that are not designed to have thunderous output. Remember I recommend three. They are designed to be small and non-obtrusive with a wide bandwidth and relatively low efficiency for a sub.
I think that Matts suggestion is a good one - test the system at high output for extraneous noises. I have not found this to be a problem in mine, but I can think of a test that will highlight this if it is there.
The packaging efficiency and arrangements of the 4 ports looks great.
The only thing that surprises me about this is the top-end extension. The low end is easily handled by multiples and EQ, or if one really wants tons of grunt a separate ULF subwoofer crossed really low, with the advantage that the ULF needn't be that good. Just a big piston with a long throw and lots of power behind it.
100 Hz seems low for all but really big rooms. And a 100 Hz F6 means that it's ~18 dB down at 200 Hz due to the 2d order rolloff at the ends of a 4th order bandpass. So one won't get much in the way of overlap in the 100-200 Hz octave.
Let me post the actual measurements and we'll see what it is. But I suspect that its higher than 100 Hz. I believe that Matt has some simulations which may not be exactly correct.
I sent the picture to my brother, and he thought it looked like a wacky die. I thought that could actually be kind of cool, paint the enclosure high gloss white, and the ports black, and then you wouldn't have to hide them if you didn't want to. Assuming giant dice actually go with your room decor.
the 100hz is what you had told me at an earlier date. You had mentioned 45hz-100hz with a 60hz center, which was following my guess simulation, which was higher, with a higher center as well.
"They have -6db points of something like 45hz and 100hz "
"The low end is easily handled by multiples and EQ, or if one really wants tons of grunt a separate ULF subwoofer crossed really low, with the advantage that the ULF needn't be that good."
I must say I'm puzzled at the willingness to forgo more than an octave at the low end.
"Just a big piston with a long throw and lots of power behind it."
Right, "just" that.
"The low end is easily handled by multiples and EQ, or if one really wants tons of grunt a separate ULF subwoofer crossed really low, with the advantage that the ULF needn't be that good."
I must say I'm puzzled at the willingness to forgo more than an octave at the low end.
"Just a big piston with a long throw and lots of power behind it."
Right, "just" that.
I think that the point is that things like linearity and frequency response don't matter much when all one wants from the sub is 20 -> 40 or 50 Hz. Basically it is just a big piston. I'm not even sure that long throw matters much if it is bandpass. It just needs to pump some air without breaking.
I'm not. Three 12's will get pretty loud down low. Even my three Tannoy System 12 DMT II's, placed in crappy positions for bass can be EQ'ed for flat response without strain down to nearly 20Hz. (They still don't sound as enveloping as a well-setup multisub system, and obviously that response won't hold outside of a very small area.) And I'd be shocked if the nearly 20 year old Tannoy dual concentric design has half the xmax of the B&C 12TBX100 I assume Dr. Geddes is using.
I would imagine that if one takes three of these subs placed per Dr. Geddes' standard rules, and runs three Abbeys or Nathans in front (for 2-3 more bass sources) full range, that will be sufficient for even most electronica played at reference levels in a domestic living room.
Of course, I'm talking about a system for music enjoyment, not one that is designed to make the neighbor's house shake from some faked Hollywood explosion.
Yeah, "just" that. No need for a super-advanced motor and the nth degree of BL/Le/suspension linearity over stroke. I bet even a high-inductance, no-shorting-ring amusical monstrosity such as John Janowitz's old TC-made HE15's would work OK if limited to 40Hz and below with a reasonably steep filter. Or some of the cheap long-throw "car" subwoofers out there. Just use EQ and power to get the output needed.
That's the response I expected, because a 100 Hz F6 sounded low based on your previous posts and my own investigations into smoothing out the modal region in my room using a "quasi-Geddes" subwoofer system (constrained randomized placement along all three axes, but direct radiating subs rather than BP) in my previous home and this one.
Earl,
I've spent a great many years in advertising, marketing, and even in a few in the product photography studio as a photographer and art director. I have only this to say: Earl, stick with your intuition on the product shots, you are doing a perfectly fine job, and please DO NOT pay any attention to Markus76's advice. It's so wrong.
And Markus, with all due respect, please don't quit your day job for a career in product photography.
..Todd
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"Of course, I'm talking about a system for music enjoyment, not one that is designed to make the neighbor's house shake from some faked Hollywood explosion."
Ah, there's the difference, though I submit that there are a lot more effects that require lots of LF besides explosions (probably still faked, but there's been talk on the internet that the people in movies are just pretending too).
It's too complicated and impractical for me to have multiple subs scattered around and still not have the ULF covered, though I agree it's likely to be a better solution than mine, which is 18" Maelstroms centered behind the front and back walls.
I'm hoping my room's deviations from Welti's guidelines don't hinder too much.
Ah, there's the difference, though I submit that there are a lot more effects that require lots of LF besides explosions (probably still faked, but there's been talk on the internet that the people in movies are just pretending too).
It's too complicated and impractical for me to have multiple subs scattered around and still not have the ULF covered, though I agree it's likely to be a better solution than mine, which is 18" Maelstroms centered behind the front and back walls.
I'm hoping my room's deviations from Welti's guidelines don't hinder too much.
Actually the system that you describe will "shake the neighbors house" (depending on how far away your neighbors are of course.)
One time when I was in college the police came to my house because they said that they could hear the stereo from the Police Station. They were probably telling the truth.
Thanks - Turns out I did like Markus background better and reshot the pics. (http://www.gedlee.com/abbey.htm) I think that they are better now, except they look B&W, but are full color. When I look at them real close I can see that I need a longer lense with more glass - another $3000 and I'll be all set.
I used to use an RB67 which had a negative that was 6 cm by 4 cm. Can you imagine!? Thats huge. 90 mm was a "normal" lense. Bright daylight was just about the right amount of light. Things have certainly changed.
This is an option for when I build them that uses all double thickness Oak braces and CLD on all the panels. It adds a lot of weight for what I am not sure is any real benefit, but some people seem to want extra "options"!
Well when you build a speaker as good as it possibly can be, and then slowly strip away certain features of high cost and low return, it makes sense that this would happen. I mean, you over built the enclosure of the Summa's (as I recall you saying), used TAD drivers, etc. You then experimented with cheaper options, found that you got much if not all of the performance you had before for considerably less money. Now you are offering an option that brings back a portion of that build excess, it probably has considerably cost, and I would expect that the benefit would be small. None the less, this would be no different than an audiophile type spending 1000's of dollars on cables for what is probably a very small improvement. Even an amplifier upgrade, after a certain point at least, is only going to make a very very small difference, yet may have very considerable cost.
You could offer an xtreme crossover upgrade with all silver foil inductors and teflon bypass caps. Only 2000 dollars more per speaker, but it will really open up the soundstage.
You could offer an xtreme crossover upgrade with all silver foil inductors and teflon bypass caps. Only 2000 dollars more per speaker, but it will really open up the soundstage.
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