Are 18", 21" pro audio subwoofers better than 12", 15" hifi subwoofers?

Those have similar specs, which one is better in terms of linearity and distortion? At the first glance the LaVoce looks like a better driver since it has more force, higher compliance, better terminals and 1.5 mm of extra xmax.

B&C Speaker 18TBW100 - 18" Subwoofer
LaVoce SAF184.03 - 18" Subwoofer

I'm designing a stereo 3-way active system (for music) with 21" bass, 1 per side. After many-many datasheet checks I still find the RCF LF21X451 the best and nothing models better in WinISD, at least in PA league. It has a fairly "low" Fs of 28Hz and I tune it to exactly that frequency in a ~400-450 liter vented box.

It's rated RMS is 2000 Watts, sensitivity around 95dB (sitting in the box already). An awsome driver.

As amp I chose the Hypex UcD2k but looking at Powersoft too, right now. Still considering if I shall stay with the big Hypex or take the Powersoft route.

Btw I don't really like very deep bass so I'll employ a 24dB/oct filter at around 24Hz and below. In addition this relieves the 2 big boys and makes their sound more precise in the useful/needed region.


Btw lifting bass region via DSP or any other means (EQ, etc) for a sealed box might stress the woofer and it can run out of capable power easily. I'm not a big fan of it.

As somebody mentioned earlier, look for low Fs woofer types with somewhat less sensitivity, that won't harm transients (yet), especially not with a great Class-D amp with plenty of reserves. +3dB reserve should be in the driving amp for a best case scenario (or even more) which means for 1500W RMS you better have something that can deliver 2.5-3kW into 8 Ohms (!). At least on paper. I usually check the real impedance of the woofer and try to extrapolate (think about) how much my amp can deliver into those impedances in the used region.

The Hypex UcD2k can deliver
2500W into 4 Ohms
1600W into 8 Ohms
.. that's why I'm looking for something little bit stronger (for peak reserves).

Link to the RCF if you still want to stick to PA woofers: RCF LF21X451 - 21" Woofer
 
Like I mentioned earlier....consider high-power rackmount class D amps for this class of woofer. A 500w amp trying to push them to full excursion with eq in a small box can run into limits quick. The ultra low noise and distortion is of no benefit in the bass range. Raw power is.
 
There is a pro audio company Bag End that uses pro audio drivers to make subwoofers. Back in the early 2000s their 18” sub got good reviews in HIFI use. The natural response of their driver/sealed box is to roll off at 12db/oct at a high frequency. They apply a patented eq called “dual integrator eq” to get flat response to a very low frequency. To me it seems like a pole shifter type eq similar to the Linkwitz transform, only operating throughout the entire subwoofer bandwidth, which should give a more seamless response.
IME “for music” the amount of sound power that is in the sub 30hz range is not that great. To me it makes a certain amount of sense to have higher efficiency at 40-80 hz where there is more content in music. You will get this from a pro driver versus a heavy coned, low resonance, designed for hifi subwoofer driver.
I’m sure there are trade offs to be had with each approach. A lot of people complain about slow subwoofer response. IME a lot of this can be due to room modes, poor setup and integration of the sub with mains, hi Q alignments that cause resonant behaviour in the woofer and also heat buildup in the driver which causes changes in the alignment, particularly in vented systems.
 
Like I mentioned earlier....consider high-power rackmount class D amps for this class of woofer. A 500w amp trying to push them to full excursion with eq in a small box can run into limits quick. The ultra low noise and distortion is of no benefit in the bass range. Raw power is.

I won't use them in big rooms, nor do I want to achieve crazy high SPL, I just want something that can play subsonic tones without destroying itself and playing very distorted. I don't need more than 500 watts since that is all it takes to run those subwoofers out of excursion at those lower frequencies. Yes, they are rated for more and I can extract more SPL at higher frequencies, but this is not my intended use. I just want deep and clean sounding subwoofers for my living room, that can shake the house with movies special effects and that play a very controled and undistorted bass with music.
 
Are pro audio subwoofers better in terms of transient response and distortion than hifi subwoofers?

In my opinion, the speaker does not have any or very little influence.

No one has answered if the impulse response is an attribute of the speaker itself and that it can be significantly altered according to the type of box in which it is installed. We already know that the sealed ones win here.
Reading this article is not clear either, if it refers to a speaker "in the air" - as when we measure the resonance of it - or already located in its enclosure ...
It's not a typical T / S data, that's why I'm intrigued, can someone clarify this please? ;)


Speaker impulse response explained – the basics – Audio Judgement
 
Woofers you should always design within box (except you're building something exotic without box) :)

T/S is a good baseline and it might give you a hint how something would behave if it behaves like stated in free air (or anechoic chamber) measurements, especially freq. and impedance curves, sometimes with off axis angles too, etc.

On the other hand, a woofer cannot be bought very much lower than its own resonance frequency. To some extent yes, but not very much.

Last but not least, a correction of declining SPLs towards low frequencies needs more and more energy from amp side and more and more motor/cone capability on woofer side. E.g. to correct a -3dB SPL point you have to drive that woofer with 2x more power with every 3dB step so for all those who try some kind of EQ/DSP on frequencies below Fs and box tuning, a juicy amp will be needed as long as the juicy woofer can follow the task.

And it's always better to have an oversized amp than a smaller one (compared to woofer maximum RMS).
 
There is a pro audio company Bag End that uses pro audio drivers to make subwoofers. Back in the early 2000s their 18” sub got good reviews in HIFI use. The natural response of their driver/sealed box is to roll off at 12db/oct at a high frequency. They apply a patented eq called “dual integrator eq” to get flat response to a very low frequency. To me it seems like a pole shifter type eq similar to the Linkwitz transform, only operating throughout the entire subwoofer bandwidth, which should give a more seamless response.
IME “for music” the amount of sound power that is in the sub 30hz range is not that great. To me it makes a certain amount of sense to have higher efficiency at 40-80 hz where there is more content in music. You will get this from a pro driver versus a heavy coned, low resonance, designed for hifi subwoofer driver.
I’m sure there are trade offs to be had with each approach. A lot of people complain about slow subwoofer response. IME a lot of this can be due to room modes, poor setup and integration of the sub with mains, hi Q alignments that cause resonant behaviour in the woofer and also heat buildup in the driver which causes changes in the alignment, particularly in vented systems.

Wanted to flesh out your explanation of how the Bag End ELF Infrasub works, and what the dual integrator is for.

You start by putting a subwoofer in a closed box that is way too small for it in the traditional sense, e.g. Vb < Vas. What does that do to the response? In box the Qb will be around 1 or higher and Fs around 100Hz which is also where the impedance peak is located. With a higher Q value the impedance peak is relatively narrow. The rolloff in frequency response below 100Hz quickly becomes 12dB/octave.

An integrator is a circuit with gain that rises at 6dB/octave. Put two of these in series, and the gain has a 12dB/octave slope. You pair this with the falling 12dB/octave slope to flatten the response. The system is only used from the resonance frequency and below.

The idea is that below resonance the impedance falls back close to Re and flattens out. I think this was supposed to be easier to drive, especially at the lowest frequencies where the impedance is essentially resistive in nature. This is also where you need to apply the largest power boost: by 25Hz you are need 24dB or so. Bag End devised a limiter circuit that keeps the amount lift, and cone excursion, in check. But you will still need a very powerful amplifier for this to work properly, and I was not always so sure that a driver in a box with Vab<<Vas was a good idea from the distortion standpoint. But it did become a successful product.

It's a way to apply extra power to make a subwoofer in a small box possible. It is similar to but different than the Linkwitz Transform circuit.
 
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I'm designing a stereo 3-way active system (for music) with 21" bass, 1 per side. After many-many datasheet checks I still find the RCF LF21X451 the best and nothing models better in WinISD, at least in PA league. It has a fairly "low" Fs of 28Hz and I tune it to exactly that frequency in a ~400-450 liter vented box.

It's rated RMS is 2000 Watts, sensitivity around 95dB (sitting in the box already). An awsome driver.

As amp I chose the Hypex UcD2k but looking at Powersoft too, right now. Still considering if I shall stay with the big Hypex or take the Powersoft route.

Btw I don't really like very deep bass so I'll employ a 24dB/oct filter at around 24Hz and below. In addition this relieves the 2 big boys and makes their sound more precise in the useful/needed region.


Btw lifting bass region via DSP or any other means (EQ, etc) for a sealed box might stress the woofer and it can run out of capable power easily. I'm not a big fan of it.

As somebody mentioned earlier, look for low Fs woofer types with somewhat less sensitivity, that won't harm transients (yet), especially not with a great Class-D amp with plenty of reserves. +3dB reserve should be in the driving amp for a best case scenario (or even more) which means for 1500W RMS you better have something that can deliver 2.5-3kW into 8 Ohms (!). At least on paper. I usually check the real impedance of the woofer and try to extrapolate (think about) how much my amp can deliver into those impedances in the used region.

The Hypex UcD2k can deliver
2500W into 4 Ohms
1600W into 8 Ohms
.. that's why I'm looking for something little bit stronger (for peak reserves).

Link to the RCF if you still want to stick to PA woofers: RCF LF21X451 - 21" Woofer

Here is the driver I use from Funk, and yes it has low Fs, and is about 93dB efficiency:

UH21vU - HARBOTTLE

It's a super woofer for me and does extremely well in mid bass applications as well due to the underhung motor topology, and full pole sleeve shorting ring. Expensive? Yes, just pull out your CC.

Best,
Anand.
 
#

Wanted to flesh out your explanation of how the Bag End ELF Infrasub works, and what the dual integrator is for.

You start by putting a subwoofer in a closed box that is way too small for it in the traditional sense, e.g. Vb < Vas. What does that do to the response? In box the Qb will be around 1 or higher and Fs around 100Hz which is also where the impedance peak is located. With a higher Q value the impedance peak is relatively narrow. The rolloff in frequency response below 100Hz quickly becomes 12dB/octave.

An integrator is a circuit with gain that rises at 6dB/octave. Put two of these in series, and the gain has a 12dB/octave slope. You pair this with the falling 12dB/octave slope to flatten the response. The system is only used from the resonance frequency and below.

The idea is that below resonance the impedance falls back close to Re and flattens out. I think this was supposed to be easier to drive, especially at the lowest frequencies where the impedance is essentially resistive in nature. This is also where you need to apply the largest power boost: by 25Hz you are need 24dB or so. Bag End devised a limiter circuit that keeps the amount lift, and cone excursion, in check. But you will still need a very powerful amplifier for this to work properly, and I was not always so sure that a driver in a box with Vab<<Vas was a good idea from the distortion standpoint. But it did become a successful product.

It's a way to apply extra power to make a subwoofer in a small box possible. It is similar to but different than the Linkwitz Transform circuit.

It would be interesting to compare the spl output vs frequency of an 84db sensitivity heavy cone woofer with a sealed box f3 of 35 hz, q of .7 to a high efficiency pro driver with an f3 of 80 hz and sealed q of .7.
There will certainly be more eq needed for the high efficiency driver but it starts off with much higher sensitivity.
I don’t seem to need kilowatts of power. Perhaps that is necessary for home theatre effects. I was surprised by how little power my subs actually use. In my own music system l use 2 15 in sealed box subs q=.7 with eq similiar to a LT circuit. The woofers are rated at 89 dB powered by a Crown cdi1000. The LEDs on the amp tell me that I rarely exceed 30w even at very loud levels with music. Crossover is around 50hz and main speakers are PI 3 with the upgraded eminence and b and c drivers. They are 95 dB efficient and can play loud without strain. Even blasting blues like Jony Lang at ridiculous levels where you can feel the drums pounding you I am only occasionally getting up to 30w. This is a test everyone should consider trying before going shopping for a kw+ amplifier.
 
It would be interesting to compare the spl output vs frequency of an 84db sensitivity heavy cone woofer with a sealed box f3 of 35 hz, q of .7 to a high efficiency pro driver with an f3 of 80 hz and sealed q of .7.
There will certainly be more eq needed for the high efficiency driver but it starts off with much higher sensitivity.
I don’t seem to need kilowatts of power. Perhaps that is necessary for home theatre effects. I was surprised by how little power my subs actually use. In my own music system l use 2 15 in sealed box subs q=.7 with eq similiar to a LT circuit. The woofers are rated at 89 dB powered by a Crown cdi1000. The LEDs on the amp tell me that I rarely exceed 30w even at very loud levels with music. Crossover is around 50hz and main speakers are PI 3 with the upgraded eminence and b and c drivers. They are 95 dB efficient and can play loud without strain. Even blasting blues like Jony Lang at ridiculous levels where you can feel the drums pounding you I am only occasionally getting up to 30w. This is a test everyone should consider trying before going shopping for a kw+ amplifier.

+ 100

I chose that path, and I am very happy to listen to music.:)
Yes, HT is another story, and bigger problems with neighbors...:D
Below 20 hertz, the strongest walls become paper....
 
I have experience both with rubber-hifi- as well as real pro subs.
I run a 18" GBS3418 in a sealed enclosure within my home theater amped with 800W - did add some ultra-subsonic-"integrator"-pushing to get that magic 20Hz.
I too have a discotheque where I use 2 x 18NLW9400 in BR enclosures, amped at 1200W / 8Ohms per.

Summary:
1. You can't do that 20Hz cinema with a PA subwoofer. The efficiency down there is too low, even adding DSP / EQ etc....in a sealed enclosure.
2. You cannot use a rubber-hifi woofer for high SPL music application. The efficiency within the most important "punch" range 60 - 110Hz is WAY too low.
 
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That driver has a Qts of 0.14 - way too low to be all that practical, even for a vented box. Most woofers from B&C (especially models with neo motors) have rather low Qts.


its fine if you don't design for flat frequency response but instead design for maximum power output capability. A difficult load for a normal amplifier though even with two in series:
Data-Bass
In this example two drivers are capable of 116 dB @ 20Hz @ 1m in ~220L box. To reach that kind of level I have to use 12*15" 8mm xmax drivers in 800L. So the IPAL drivers are significantly outperforming lower quality drivers. However my entire system cost less than two IPAL drivers.
 

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its fine if you don't design for flat frequency response but instead design for maximum power output capability. A difficult load for a normal amplifier though even with two in series:
Data-Bass
In this example two drivers are capable of 116 dB @ 20Hz @ 1m in ~220L box. To reach that kind of level I have to use 12*15" 8mm xmax drivers in 800L. So the IPAL drivers are significantly outperforming lower quality drivers. However my entire system cost less than two IPAL drivers.

I'm not really sure what data you are looking at, but at the page you linked to for the dual opposed IPAL subwoofer the "CEA-2010 max burst" SPL at 20Hz seems to be only 111dB. For TWO 21" drivers that is pretty poor, and the problem is caused by the frequency response of the system (see attached). The low Qts makes the FR droop by 20dB at 20Hz compared to 100Hz. The drivers might be capable (by volume displacement) of more output, but the low Qts motor is preventing that from being generated without a giant amount of EQing and power input a la the Bag End ELF approach. It would be better to use two high Xmax 18" home audio subwoofers with low Fs and Qts~0.4-0.5 in a large box if you want low frequency and high SPL.
 

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