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15-18" Powered Subwoofer Pair Build

sarumbear

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People can do what they want. I’d not want to cope with a large upper bass or lower midrange pipe resonance.
In order for the port resonance to occur the driver has to work at that frequency. Port resonances normally occur at 450Hz or higher. A subwoofer driver’s output will be 20dB or more down at that frequency.
 

jhaider

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In order for the port resonance to occur the driver has to work at that frequency. Port resonances normally occur at 450Hz or higher. A subwoofer driver’s output will be 20dB or more down at that frequency.

Like I said, if other people are willing to cope a large pipe resonance that’s ultimately unnecessary, whatever.
 

sarumbear

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Like I said, if other people are willing to cope a large pipe resonance that’s ultimately unnecesary, whatever.
You do not understand what I tried to explain. There cannot be port resonance on a subwoofer. People does not have to cope.
 

jhaider

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You do not understand what I tried to explain. There cannot be port resonance on a subwoofer. People does not have to cope.

I understand the issue just fine, and the above is simply wrong in the case of most ported subs unless one mistakenly believes a low pass is an infinite cliff. Or, I suppose, if one misuses subs to just give extreme ULF instead deploying them high enough to smooth out the impact of room modes in the upper bass.
 

sarumbear

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I understand the issue just fine, and the above is simply wrong in the case of most ported subs unless one mistakenly believes a low pass is an infinite cliff. Or, I suppose, if one misuses subs to just give extreme ULF instead deploying them high enough to smooth out the impact of room modes in the upper bass.
I did say 20dB or more haven’t I? That’s not a cliff.

A standard subwoofer works at maximum 150Hz. The lowest pipe resonance on a pipe that will fit to a normal size subwoofer enclosure will be at higher than 500Hz. At that frequency the driver is at least 20dB down using a 2nd order filter, much more when using a 4th order. How can such a low level resonance be an issue?

Can you show some subwoofer FR charts that show such resonance?
 
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concorde1

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From https://www.audioholics.com/subwoofer-reviews/perlisten-d215s/conclusion :
image.jpg

Are there any available drivers that match this distortion performance?
 

morpheusX

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concorde1

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I won't attempt specific recommendations but I ALWAYS RECOMMEND running speaker design software, I've used WinISD (FREE).

You plug-in the Thele-Small parameters for your potential drivers and then choose a basic design (sealed or ported, etc,) and the software will recommend the box size, and port dimensions (if you choose ported) and it will plot the predicted frequency response. Then you can experiment with modeling different changes to the size & port if you want to extend the bass, etc. (There are always trade-offs and extending the bass might make a bump in the bass response, etc.)
I put the BMS 18N862 parameters into WinISD. Vented. With no changes, I got this:
Untitled.png
111111.png
212222.png

Newbie question: I notice commercial subs on data-bass, for example from SVS and Rythmik, have decent extension into the 10-20 Hz range; whereas the DIY drivers (like this BMS) have massive drop off, the -3dB point being in the 50Hz area; or on the plot about, the -3dB point being at perhaps 33Hz.

Is this due to DSP being used in end products which uses the headroom to allow reshaping the response? I can't think of anything else that makes sense. These massive sub drivers having poor response according to data-bass must be due to lack of DSP.

--

If I do DIY subs, I am keen to use the BMS 18N862. I'm confused as to how to optimise the settings in WinISD to get the best response, given that DSP will be used later anyway.
 

morpheusX

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Yes, comercial subs have DSP applied.

Nevertheless, if you look at CEA2010 measures:

SVS SB13 Ultra
- 83db @ 10Hz,
- 92.6 @ 16Hz

SVS SB16 Ultra
- 83.9db @ 10Hz,
- 94.7 @ 16Hz

And the BMS 18N862, even without DSP:
- 90.9db @ 10Hz,
- 99.2 @ 16Hz

The single BMS has more 6db on the lowest frequencies, compared to the SVS sealed subs.

Here a real example for dual BMS, in a 50 m2 attic:

Nearfield (woofers bought 3 years apart):

2CqDWxX.png


At MLP without EQ, each sub in isolation:

BbLa1Sp.png


At MLP without EQ, each sub in isolation and both subs:

jAVLrBO.png


Here, the sum of both subs measured, versus using REW Trace Arithmetic

coDdCRX.png



And finally, after using Dirac

D9qkGsR.png
 

Adi777

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The single BMS has more 6db on the lowest frequencies, compared to the SVS sealed subs.

Here a real example for dual BMS, in a 50 m2 attic:
Are there websites with different subwoofer measurements, preferably something a'la ranking?
 

gnarly

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If I do DIY subs, I am keen to use the BMS 18N862.
Very good choice I think.
I've used the 18N862 in single sealed, single ported, and dual ported DIYs. All three types have worked great.

The ported builds were for f-3 @30Hz (for music, not really into HT)
Here's a CEA pass chart for the dual ported build.
 

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Adi777

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Very good choice I think.
I've used the 18N862 in single sealed, single ported, and dual ported DIYs. All three types have worked great.

The ported builds were for f-3 @30Hz (for music, not really into HT)
Here's a CEA pass chart for the dual ported build.
Which woofers are you recommend for subwoofer for home cinema? 21-24 inch especially.
 

gnarly

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Which woofers are you recommend for subwoofer for home cinema? 21-24 inch especially.
I've no experience with drivers that size, or trying to reach much below 30Hz (without EQ boost which i try to avoid for headroom's sake).
Every now and then, I'll use Hornresp to explore 21-24" driver DIY builds to reach lower, and typically look at B&C and 18Sound drivers.
I'd probably build an I-Pal if not budget constrained.

Check out AVS Forum for threads on the big guys.
 

morpheusX

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Which woofers are you recommend for subwoofer for home cinema? 21-24 inch especially.
Where are you located?

If in Europe, you'll have to resort to professional brands, like B&C and 18sound.

In the US, you'll have much more options.
 

jhaider

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I put the BMS 18N862 parameters into WinISD. Vented.

For home use there’s no need to do that. You’ll get plenty of output out of a smaller closed box, which offers the additional benefits of pressurizing the room lower and avoiding vent resonances.

Basically small signal modeling is pointless today. All you really need to concern yourself with is power and excursion. EQ will set the frequency response. A good rule of thumb if you don’t want to get into setting limiters is: enter the driver and your amp power (or the biggest amp you might use) into Unibox or whatever, and find the smallest closed box that will push the driver to rated xmax.

Subs are easy, especially when you’re dealing with this kind of extreme driver.

For reference, I recently had to replace an Aurasound NS18 that started to make some noise after ~15 years of service in three different cabinets (pour out a glass). I used a BMS driver in the I think ~85L closed box, though I think 850 not 862. After EQ there’s no difference I can detect. (The other 2 subs use Aurasound drivers.) The system still extends down to 16Hz with a smooth rolloff below that. It is still smooth to ~700Hz, well beyond my lowpass. Use good drivers and big power, and subs are easy.
 
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Adi777

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Where are you located?
Europe, Poland. Yes, it's not to many options with subwoofers. I think, what will be bettter for my cinema room. Traditional subwoofers or SBA system. Will be only one row of seats, so maybe I don't need a SBA? What do you think?
 

morpheusX

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Europe, Poland. Yes, it's not to many options with subwoofers. I think, what will be bettter for my cinema room. Traditional subwoofers or SBA system. Will be only one row of seats, so maybe I don't need a SBA? What do you think?

In Europe, you should be able to easily get any of this drivers, all tested in data-bass.com

- BMS18N862: https://data-bass.com/#/systems/5c48e01911126b0004ca12ec?_k=qcpf1c
- B&C 21SW152-4: https://data-bass.com/#/systems/5b11dab8a201f10004e39d72?_k=ewio3y
- B&C 21DS115-4: https://data-bass.com/#/systems/5d02b177d6b2560004ebe49e?_k=jdn66m
- Eminence NSW6021-6: https://data-bass.com/#/systems/5d0beab0b3ca0a0004fc82ae?_k=rbou86 (although excellent, this should be too pricier, around 11150$)
- Lavoce SAN214.50: https://data-bass.com/#/systems/5d03f339d349e90004d8fcd5?_k=9rfu7y

Regarding the second question, i don't know!

You could open a thread here, you have the bigger bassheads there :)
- https://www.avsforum.com/forums/diy-speakers-and-subs.155/
 

ryanosaur

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(although excellent, this should be too pricier, around 11150$)
:eek:
Inflation is a b!tch, huh.

All of these Drivers have gone up a bunch over the last year or so. That Eminence used to be available under $700 US
 

bigjacko

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I don’t see any point in servo. If you stay within the limits of linear Xmax an electromagnetic driver is pretty linear. Just select the correct driver for the job.
But correct drivers are not cheap, because it takes a lot to do the engineering right and make them. There are two ways to get good drivers, one is to do as much engineering as purifi, the other one is servo or klippel system. All other ways are close but cannot compete with those two mentioned above. Besides linear Xmax, the other benefits of servo are getting rid of the effect of aging on the driver, driver tolerance, heat compression, limit excursion in a range and able to compromise some part of the driver to get lower price. Those are even better benefit than linear Xmax. I would say servo subs are the real high end subs if the servo works.
 
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