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20th February 2008, 06:58 PM  #11 
diyAudio Member
Join Date: Jul 2007
Location: South Worcestershire

JBL at least quote distortion data for their prosound woofers.
Sufficient multiples of their 18" devices (e.g. 2241) would move lots of air with low distortion. 
20th February 2008, 11:54 PM  #12 
diyAudio Member
Join Date: Jan 2006

beyma and bms also show distortion measurements

21st February 2008, 02:19 PM  #13 
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Join Date: Feb 2007
Location: London

If you're looking for a proaudio subwoofer  one that won't run out of linear Xmax at full power down to (say) 30Hz or below  there are few choices.
Taking linear Xmax as (HvcHg) and mathematical Xmax as Hvc3Hg/4 (estimated to agree with DUMAX or Klippel Xmax), we have in order of descending mathematical Xmax (which is what most manufacturers quote): 1. Aura 1808/Seismic 8196 : 100mm underhung 25mm Al coil in 50mm gap  linear Xmax 13mm, mathematical Xmax 19mm  replaced the 6174 (see below), has lasted me for several years now  extremely expensive 2. McCauley 6174 : 100mm overhung 40mm Al coil in 10mm gap  linear Xmax 15mm, mathematical Xmax 17.5mm  relatively low BL, I fried one of these with repetitive 25Hz bass  very expensive, needs huge box 3. BMS 18N850V2 : 100mm overhung 38mm Cu coil in 12mm gap  linear Xmax 13mm, mathematical Xmax 16mm  just plain expensive, I will use this next time (since I need 4 drivers) 4. Ciare 12.00SW / 15.00SW : 100mm overhung 33mm Cu coil in 10mm gap  linear Xmax 11.5mm, mathematical Xmax 14mm  not much margin past Xmax before damage? 5. B&C 21SW150: 150mm overhung 32mm Cu coil in 12mm gap  linear Xmax 10mm, mathematical Xmax 13mm (B&C quote 15mm...)  extremely expensive 21" driver 6. B&C 18SW115 : 115mm overhung 29mm Cu coil in 11mm gap  linear Xmax 9mm, mathematical Xmax 12mm (B&C quote 14mm...) 7. Ciare NDH 154S : 100mm overhung 30mm Cu coil in 14mm gap  linear Xmax 8mm, mathematical Xmax 11.5mm 8. PD 2150 : 150mm overhung 30mm Cu coil in 15mm gap  linear Xmax 7.5mm, mathematical Xmax 11.5mm (PD quote 12mm) Below these there are a lot of drivers with 25mm or shorter coils which shouldn't really call themselves *sub*woofers... Out of all these the Aura/Seismic driver is probably the most linear, especially because there's very little flux or inductance modulation due to the underhung radial neo magnet structure. However it's not suitable for many enclosure types due to very low Qes, and is *very* expensive. The McCauley needs a huge box and is (in my experience) a bit fragile, and it costs almost as much as the Aura (if you can find one). The BMS is probably the best choice overall, it's pretty linear and quiet at high amplitudes, and works well in relatively small reflex boxes e.g. 140l tuned to 32Hz is close to ideal. It's about half the price of the Aura/Seismic driver. The Ciare drivers are good and quite cheap but don't have as much displacement because the diameter is smaller. The B&C and PD 21" look good at first, until you realise that they cost more than a pair of BMS18N850 and have lower power handling, efficiency and displacement. Overall I'd say the BMS18N850V2 is the best bet  the V1 has higher BL and Mmd which again makes it less useful except in a very big horn. Ian 
21st February 2008, 05:00 PM  #14 
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Join Date: Jan 2006

Why limit yourself to linkwitz transformed IB? In comparison with more efficient designs, you loose alot of linear spl on this route, which you have to compensate with lots of drivers, which is like throwing money out of the window. If your goal is high spl and clean sound, nothing beats horns. And since the invention of tapped horns, they can also have a moderate size.

21st February 2008, 07:08 PM  #15  
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Join Date: Feb 2007
Location: London

Quote:
Fullsize horns are impossible to beat by definition, but oh boy are they big :) Ian 

21st February 2008, 07:18 PM  #16  
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Quote:
A bass reflex box has only one resonant mode (subject to vent "choking" nonlinear effects at high SPL) and one corresponding frequency zone where cone displacement is reduced, but in a tapped horn you have several resonant modes and cone displacement nulls across the passband.
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21st February 2008, 08:44 PM  #17  
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Join Date: Feb 2007
Location: London

Quote:
It turns out that if you compare one (expensive) driver in a tapped horn with two (cheaper) drivers in a reflex you end up with the same box size, efficiency, maximum output, cone travel, and cost  see my (rather long) post to the tapped horn thread. If you don't believe me plug the numbers into Hornresp and you'll get the same answers. Vent choking is only a problem if they're too small; each BMS18N850 needs a 200mm diameter port 500mm long, which is over 10% of the box volume but will not suffer this problem. Ian 

21st February 2008, 10:34 PM  #18 
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Join Date: Dec 2005
Location: west lafayette

No love for 18sound drivers? They weren't even mentioned in your analysis.
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21st February 2008, 11:11 PM  #19  
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Join Date: Feb 2007
Location: London

Quote:
Ian P.S. All the above are OK down to 40Hz or so without running out of Xmax, but not lower which is where I'd say a subwoofer should go. 

22nd February 2008, 04:41 PM  #20 
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Join Date: Dec 2005
Location: west lafayette

How reasonable would a 3040hz horn be?
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