Who makes the lowest distortion pro-sound subwoofers?

[thadman]

As is the situation with the 18sound midrange drivers, I haven't been able to track down much information regarding prosound subwoofers.

Who makes the lowest distortion prosound subwoofers? As far as alignment, lets say Infinite Baffle or LT.

The only high performance drivers that I'm aware of that may possibly be given this title are the BMS 18N850, 18Sound 21LW1400, or PD2150/PD2450. What other options are available?

 

[JHelms]

Aura 1808 IMO

 

[Tim__x]

If low distortion is your primary goal, besides picking fundamentally low distortion woofers (an admirable choice to be sure), you should look at your design choices and see what you can do.

Try to keep excursion down, that means more and larger drivers. Horn loading is a terrific choice for low distortion. If you're feeling truely brave you might look into closed loop systems with servo feedback.

 

[thadman]

Infinite Baffle or Linkwitz Transform (10hz) would be the desired alignment. Since Prosound woofers come in sizes up to 24", 120dB at 10hz-100hz seems like a perfectly acceptable challenge with boundary gain included and >2 subwoofers.

10hz would be just a challenge. If they had the displacement capability to drop down to 10hz, then 20hz transients would be a walk in the park. It would also be quite impressive imo.

High pass filter would be adjustable for Output levels desired. For instance:
U571, hpf at 10hz (think 48-96dB/octave)
mundane HT, hpf at 15-20hz
music, hpf at 30hz

If possible, I'd like to keep cost below $2000-2500.

 

[Eva]

Infinite baffle and Linkwitz Transform are the alignments demanding the highest cone displacement for a given SPL and thus they are the ones producing the highest distortion levels, like 10% THD at 40Hz when trying to make it a bit loud.

For low distortion (in that sense) consider horns, they can be designed to produce some low frequecy SPL with little cone displacement.

 

[lne937s]

It seems to me that there is some confusion between dipole and infinite baffle. Infinite baffle presurizes the room and uses the room behind the baffle like an infinitely large box. Dipole does not pressuize the room- with both the front and rear waves being emitted into the same room. Infinite baffle has efficiency like a really large sealed cabinet. Dipole is the most demanding of displacement/excursion- making it difficult to get high spl at low frequencies.

 

[thadman]

It seems to me that there is some confusion between dipole and infinite baffle. Infinite baffle presurizes the room and uses the room behind the baffle like an infinitely large box. Dipole does not pressuize the room- with both the front and rear waves being emitted into the same room. Infinite baffle has efficiency like a really large sealed cabinet. Dipole is the most demanding of displacement/excursion- making it difficult to get high spl at low frequencies.

Hmm, what would suggest that we are unfamiliar with the aforementioned alignments?

 

[pkm]

As is the situation with the 18sound midrange drivers, I haven't been able to track down much information regarding prosound subwoofers.

Who makes the lowest distortion prosound subwoofers? As far as alignment, lets say Infinite Baffle or LT.

The only high performance drivers that I'm aware of that may possibly be given this title are the BMS 18N850, 18Sound 21LW1400, or PD2150/PD2450. What other options are available?

I think your barking up the wrong tree.
Your looking for high Xmax in a high Sensitivity pro sound speaker.Sure their Xmech is high though.

Actual distortion measurements will need to be carried out on all drivers under same conditions.

 

[pkm]

Some measurements of HT woofers

http://www.mfk-projects.com/

 

[lne937s]

Hmm, what would suggest that we are unfamiliar with the aforementioned alignments?

I might have misunderstood, but the comment from Eva about "alignments demanding the highest cone displacement for a given SPL" and that the Linkwitz Transform was developed for dipoles to counteract dipole cancellation.

Going by the general rule of: small size/high efficiency/depth- you can have 2, but not all three. The infinite baffle functions like an infinitely large sealed subwoofer, so it should produce low frequencies efficiently. As such, it would tend to be efficient compared to other sealed alignments (which tend to be low distortion), and therefore not be creating high levels of distortion due to trying to counteract forces of nature...

You just need to make sure you have a subwoofer that fits the application (stiff enough suspension, etc.)

You may want to look at this popular choice for IB... 4 in a manifold with a 500w amp should get you (especially with room gain) quit a bit of low end grunt without any EQ.
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=295-455

 

[PigletsDad]

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.

 

[MaVo]

beyma and bms also show distortion measurements

 

[iand]

If you're looking for a pro-audio 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 (Hvc-Hg) and mathematical Xmax as Hvc-3Hg/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 15-4S : 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

 

[MaVo]

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.

 

[iand]

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.

Tapped horns aren't necessarily more efficient, lower distortion or have higher maximum output tha a reflex of the same size -- I'm just going to post an interesting comparison to the "Collaborative tapped horn project" thread...

Full-size horns are impossible to beat by definition, but oh boy are they big

Ian

 

[Eva]

Tapped horns aren't necessarily more efficient, lower distortion or have higher maximum output tha a reflex of the same size -- I'm just going to post an interesting comparison to the "Collaborative tapped horn project" thread...

Full-size horns are impossible to beat by definition, but oh boy are they big

Ian

This is a risky statement. Remember that in a tapped horn the radiation from both sides of the driver is used and this already produces some gain by itself. Then you have the gain due to horn loading.

A bass reflex box has only one resonant mode (subject to vent "choking" non-linear 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.

 

[iand]

This is a risky statement. Remember that in a tapped horn the radiation from both sides of the driver is used and this already produces some gain by itself. Then you have the gain due to horn loading.

A bass reflex box has only one resonant mode (subject to vent "choking" non-linear 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.

True indeed, *if* you compare one driver in a tapped horn with one driver in a reflex, which is what Tom Danley did in his white paper when he concluded that a tapped horn was much superior. But he was really comparing it to the wrong thing (which is why I don't think my statement is risky)...

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

 

[thadman]

No love for 18sound drivers? They weren't even mentioned in your analysis.

 

[iand]

No love for 18sound drivers? They weren't even mentioned in your analysis.

18sound make some excellent drivers, but not for this purpose -- along with Beyma, DAC, RCF they fall into the category of "drivers with 25mm or shorter coils which shouldn't really call themselves *sub*woofers"...

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.

 

[thadman]

How reasonable would a 30-40hz horn be?