Thanks Art. I don't have much direct comparison experience of bass done by large woofers vs multiple small drivers of the same Sd. And of course that's the basic question of this thread.
Small drivers struggle, but mostly because not enough of them are used. I don't hear X-max making up for surface area in my listening experiences. But it would be interesting to find where the two set overlap in sound quality.
Small drivers struggle, but mostly because not enough of them are used. I don't hear X-max making up for surface area in my listening experiences. But it would be interesting to find where the two set overlap in sound quality.
I think we can easily agree on that
sound quality, interesting word
would be nice or convenient if we could narrow it down to just a few variables
but I doubt it
Though a small driver needs to move farther than a big driver for the same SPL, it does not have to "struggle" if designed for long excursion and played within Xmax.
That said, a small driver is often expected to play well above "subwoofer" territory, distortion that would be acceptable if crossed over at 100 Hz turns into nasty IM when the cone is required to play up to 1 or 2K.
Although the 18" design I presently use has slightly more output than the four Lab12" it replaced, the Lab 12" actually go lower with slightly less distortion.
The four dual Lab 12 had no "struggle" putting out more 40 Hz output than eight Meyers 850 P dual 18" cabinets on a side by side outdoor gig.
Simply comes down to linear displacement, and as Inductor wrote, that needs to be measured to confirm.
I have done quite a bit of distortion measurements, and have found the Xmax figures for B&C, Eminence, EV, and JBL to correspond well to the 10% distortion amount.
Have found Xmax over around 6mm to be a very uncertain territory with ample opportunity to produce high distortion. So now my "most practical woofer ever" is a 1.5"VC 28oz 10" using 8 per side. Almost the exact cone area of two 18". So if 4 tens were an 18" the VC would be 6", the magnet would be 122 ounce and Xmax would still be 6.3mm. Not a bad 18 in a much easier enclosure to fabricate.
After all do we have two speakers to compare? A ~6.5" and a bigger 10/12" or 15".how many parameters do we need fixed, to define the goal
I guess the small one should be around 1/4 of the price* (of the big one). Or it will not win.
* make it for 1/4 of the price and 1/4 of the size of the enclosure and same F3/F6/F12 (tail attenuation). Only SPL can be lower because of summing of the group of four. So we have:
1. - SIZE (L/FT3), for the enclosure
2. - F3 (Hz), for lower attenuation F3/F6/F12
3. - SPL (dB)
4. - PRICE
Nice weltersys. Do you have an anechoic chamber or rented time in one? (Open field/accelerometers? Can you describe.) I will have to congratulate you then for your work on distortion measurements, time and lab premises availability if that's the case.
Here is the info gently given by John_E_Janowitz (AE).
http://www.diyaudio.com/forums/mult...rivers-sealed-bass-channel-3.html#post2336334
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To those who say that good 6,5" will beat the crap out of poor old 15" woofer, do you refer to system where 6,5" is in narrow or wide enclosure? It would nice to hear good 6,5"-8" in 50 cm wide box, but if you're talking about narrow baffles I think you can not speak about those in a same day!
One thing for sure & In the day
One thing for sure, it takes less time for the mechanical signal to propagate from the voice coil to the edge of the cone in a smaller driver with similar cone materials as used in the larger driver. Most drivers use paper process cones and IMO only all but the heaviest treated large drivers have a "flopping cone" lacking punch sound smaller drivers seem to lack.
Eight 10" per side is the area of two 18' per side so there is the chance for low distortion bass. People say the bass is like being hit. Even the car stereo challenge guys drool over that setup.
Using a distortion analyzer for accurate measurement of distortion I found when THD from second and/or third harmonic exceeded 3% the apparent pitch center moved higher. At 10% THD the effect was profound, 40Hz at 10% sounded just like an undistorted 80Hz.
The "in the day" woofer used here is an Altec 411-8A. 3.75" x .75" flat wound voice coil, 15", Fs=18Hz, and a 128 ounce magnet. Tapered top plate for 3/8" gap using 1/2" thick material. Still one of the 5 lowest distortion 15s I have ever tested and fit to be one of the best today. But then that was like when, 1960?
Maybe the reference was to the 1920 15"? That would make perfect sense and be exactly correct as Xmax was measured in fractions of a mm.
One thing for sure, it takes less time for the mechanical signal to propagate from the voice coil to the edge of the cone in a smaller driver with similar cone materials as used in the larger driver. Most drivers use paper process cones and IMO only all but the heaviest treated large drivers have a "flopping cone" lacking punch sound smaller drivers seem to lack.
Eight 10" per side is the area of two 18' per side so there is the chance for low distortion bass. People say the bass is like being hit. Even the car stereo challenge guys drool over that setup.
Using a distortion analyzer for accurate measurement of distortion I found when THD from second and/or third harmonic exceeded 3% the apparent pitch center moved higher. At 10% THD the effect was profound, 40Hz at 10% sounded just like an undistorted 80Hz.
The "in the day" woofer used here is an Altec 411-8A. 3.75" x .75" flat wound voice coil, 15", Fs=18Hz, and a 128 ounce magnet. Tapered top plate for 3/8" gap using 1/2" thick material. Still one of the 5 lowest distortion 15s I have ever tested and fit to be one of the best today. But then that was like when, 1960?
Maybe the reference was to the 1920 15"? That would make perfect sense and be exactly correct as Xmax was measured in fractions of a mm.
less time , like in higher frequency ?
similar cone material ?
but those are necessary variables
My testing was done outside, using the RTA function of Smaart.
Sine wave tones run at specific voltage, level of harmonics noted, then converted to a distortion figure in %.
A machine like LMS would make the process easier and faster, but one gets by with the tools one has. The slow process does allow a bit more in depth review of the harmonic cascade than other methods.
More details and results here:
PSW Sound Reinforcement Forums: LAB Lounge => JBL SRX718 - Basic Distortion Measurements
Anyway, speakers are kind of like dogs, it's not the size of the dog in the fight that makes a winner, it's the size of the fight in the dog.
That said, I'd bet on a doberman over a toy poodle.
Art
not even 10 poodles
how about sports cars are fast on the road, but beaten by a truck in the desert
I kind of liked Inductors effort to define the goal by fixed variables
or else we could just as well debate how music sounds on Mars
I kind of liked Inductors effort to define the goal by fixed variables
or else we could just as well debate how music sounds on Mars
In addition to Inductor's list:
"1. - SIZE (L/FT3), for the enclosure
2. - F3 (Hz), for lower attenuation F3/F6/F12
3. - SPL (dB)
4. - PRICE "
since this is the Multi-way forum, I would add:
5. Upper frequency crossover point
6. Allowable distortion
When all the variables are considered, there is no one answer as far as which is better, multiple small woofers or a single large one.
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