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15-18" Powered Subwoofer Pair Build

concorde1

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I have March Sointuva speakers on the way.

I am considering building a couple of powered 15"-18" driver subwoofers to fill in the low frequencies and take the load off the Sointuva's.

• My room is about: 13 ft * 15 ft * 11 ft (l*w*h)
• For both music and movies.
• I don't mind waiting for stock, as it will be a while before I purchase parts anyway.
• The aim is to build something with excellent neutrality/linearity and very low THD.
• Thinking of building the boxes with HDF or baltic birch, with a nice veneer on the exterior.

I seek advice on:

• What drivers to use: I am happy to spend a lot on drivers.

• What corresponding plate amps to use: ditto.

• Ported or sealed? I understand ported provides higher SPL output but is more difficult to design?

• How to design the boxes. eg what thickness of HDF, how to brace boxes, how to integrate ports.

My rationale for DIY subs is: I think they are probably easier to design than any other audio component; I want to spend a bit less than a commercial sub; and I have some DIY experience in building my stereo amplifier.

If in the end I don't DIY I think I would instead invest in a couple of Genelec or Perlisten or Arendal.
 

DVDdoug

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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.)
 

ryanosaur

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I have March Sointuva speakers on the way.

I am considering building a couple of powered 15"-18" driver subwoofers to fill in the low frequencies and take the load off the Sointuva's.

• My room is about: 13 ft * 15 ft * 11 ft (l*w*h)
• For both music and movies.
• I don't mind waiting for stock, as it will be a while before I purchase parts anyway.
• The aim is to build something with excellent neutrality/linearity and very low THD.
• Thinking of building the boxes with HDF or baltic birch, with a nice veneer on the exterior.

I seek advice on:

• What drivers to use: I am happy to spend a lot on drivers.

• What corresponding plate amps to use: ditto.

• Ported or sealed? I understand ported provides higher SPL output but is more difficult to design?

• How to design the boxes. eg what thickness of HDF, how to brace boxes, how to integrate ports.

My rationale for DIY subs is: I think they are probably easier to design than any other audio component; I want to spend a bit less than a commercial sub; and I have some DIY experience in building my stereo amplifier.

If in the end I don't DIY I think I would instead invest in a couple of Genelec or Perlisten or Arendal.

If this is your first build, it can be a tough hump to get over. Someplace like GSG Audio could be very helpful with aiding you in picking a complete system based on your wants.
I'm not certain if they are still offering them, but for a minute or two, recently, you could get a Marty Sub and Stereo Integrity SQL 15 Drivers. (I'm working on my own build with 6 of those beasts.)
Beyond that, there are many other options.

How handy are you? Do you have access to tools, clamps, even a wood shop?
What are your Subwoofer goals? Are you chasing single digits? 16 Hz for a Pipe Organ? Home Theater usage or just music?

With good product and modern design, there is literally no reason to look at Sealed builds unless you are very limited on space. Not that you can't get good performance that way, but the efficiency of a Sealed Sub down low requires gobs more power than a well designed ported cabinet.

FWIW, DIY can start to make sense if you have all the tools and you are building multiple Subs. Oh... and you can't value your personal time so much that you are counting labor hours. :p
 

alex-z

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THD is not a great metric for bass quality, as our hearing tolerates a significant amount at low frequencies, particularly at high volume.

Meaning you should build the subs almost entirely for response linearity, and time domain performance. I am a big fan of sealed subs because they have no port compression issues and no port chuffing. Although I do think ported has a place for people who have big rooms and/or enjoy movies. Ported subs have additional output at the tuning frequency, but suffer below and above it. They are not better, just different.



My recommendation would be to build your subs with opposed 12" drivers, which lands the total displacement between a single 15 and 18" driver, but with less inherent cabinet vibration. A pair of Ultimax 12" for example should hit -3dB at roughly 32Hz in a 5ft cabinet, and -10dB at 20Hz. That is without accounting for room gain, you may even see a flat response to 20Hz in-room.


Given their excursion limit, you can expect to put about 850 watts into a pair of them, resulting in 112dB of output at 1 metre at 32Hz. Again, the room gain + second sub will boost that figure.

For the cabinets, 3/4" MDF is more than sufficient if you use bracing and double thickness baffle. An interlocked U shape works great, connecting the weakest point of all panels.

For driving the subs, I would probably go with a Crown XLS2502. It should have enough power to run 1 sub per channel near full output capability. You could use plate amps like the Dayton SPA1000, but I find the efficiency of class AB a poor choice for subwoofer applications.
 

Jon AA

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While doing your own design may be fun and educational, if getting a finished product (that is good) up and running with minimal hassle/risk/work is something you're after, I'd go for a flatpack.

For that room size with those speakers, either 15 or 18 will be more than big enough unless sub 15 Hz content is important to you. For 15" GSG still has their Cube available: https://www.diyaudio.com/community/threads/ground-plane-measurements-results-good-and-bad.352797/

DIYSG has both their Cube and the Kuda (round ports, smaller) available:



If sub 20 Hz content isn't important to you, the Kuda will give you a couple more dB of output. If it is, the Cube is tuned lower.

GSG recommends the Lavoce and it's quite affordable: http://www.loudspeakerdatabase.com/LaVoce/WAF154.00

Many have had great results with the B&C 15DS115-4 http://www.loudspeakerdatabase.com/BC/15DS115 (I'm currently using this one for a build).

One thing that simplifies a build of a DIY--there's no need to use a plate amp. A Crown 1502 bridged maxes these drivers out pretty much and installing terminals/terminal cup for speaker wires is very easy.

If you have room for 18's, that's great. The 18" equivalents of the above are just better and not that much more expensive.
 

morpheusX

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As i mentioned in the other thread, the bigger the woofer, the best returns: more SPL, less distortion, etc.
The only downsize is space, but if you can accommodate it, 21" offer the best result for the money.

If you're concerned with the old "bigger woofers are slow, small woofers are fast", have a look at data-bass.com myths.

Have a look at the new PSA subwoofers, they use the same B&C drivers i suggested before:
- the 18 version: https://www.powersoundaudio.com/products/S1813
- the 21" version: https://www.powersoundaudio.com/products/s2112

Also look at avsforum thread, you can check some details, pics, as well as how the box is built.
 

sarumbear

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I would suggest servo subs, rythmik sells driver and servo combo for diy.
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.
 

blueone

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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.
I agree. If you look over this awesome list of measurements:


You see that there isn't much correlation between the quality of output and distortion measurements and whether or not the drivers employ a servo mechanism.
 

morpheusX

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I would look for options available locally, and testes at 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

I would select based on availability and price, 2 of the above, even sealed, would run circles around any comercial alternative.
Moreover, no need to speculate, just look at data-bass.com analysis and compare.

As the OP is from NZ, it would probably be very expensive to ship large subwoofers (moreover with the added VAT).

By going DIY, you should be able to get one of the above drivers for a good price (500-800$, excluding the Eminence).
So 1600$ in drivers, 1400$ for plate amps (could be even cheaper if you select an external amp with DSP), and then the rest on woodworking, depending on how professional you would like them.

I found this thread amazing, you can check how professional a DIY subwoofer can be made:
 

ryanosaur

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Reviewing recent Sub measurements also shows that there is really no concern that needs to be had in considering a ported build. Modern designs far outperform older designs and blow all the subwoofer myths out of the water.
 

sarumbear

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Reviewing recent Sub measurements also shows that there is really no concern that needs to be had in considering a ported build. Modern designs far outperform older designs and blow all the subwoofer myths out of the water.
Ported is very efficient but you loose the benefit of slower slope, which may offer better deep bass response.
 
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ryanosaur

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Ported is very efficient but you loose the benefit of slower slope, which may offer better deep bass response.
Like everything else in Speaker design, it's tradeoffs. Sealed Subs require more power down low with the ported cabinet giving you more efficiency.

Room size also comes into play when counting on Cabin Gain from Sealed designs to prop up that deeper extension.

Please don't misunderstand, I'm not [email protected] on Sealed, but urging greater consideration based on actual needs and goals (hence my questions in my first reply above) rather than relying on audiophile myths. OP has yet to reply to those questions about what they are really looking to achieve with these Subs.

No disrespect here, just practicality. :)
 

abdo123

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I would have recommended a kit (building a sub is fairly straight forward) but your profile says New Zealand and I’m doubtful of what is available over there.
 

ryanosaur

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I would have recommended a kit (building a sub is fairly straight forward) but your profile says New Zealand and I’m doubtful of what is available over there.
Good catch, great point. Kits and flat packs might not make sense to ship there. (I usually look at where a person is before recommending product and what not. Thank you.)
 

sarumbear

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sarumbear

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Physics didn’t change. Vent resonances are still a problem.
If you are talking the high frequency port resonance that’s not an issue on a subwoofer as it doesn’t operate at those frequencies.
 

jhaider

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I don't think that's a concern at the operating range of a subwoofer.

People can do what they want. I’d not want to cope with a large upper bass or lower midrange pipe resonance.

Besides, in a modern system such compromises are totally unnecessary. Output down low comes from multiples. Here we’re talking at the minimum dual 15s. I’d get two BMS or B&C woofers, put them in the smallest closed box that will push the woofer to rated xmax with the intended power, and be done with it. If for somebody hits their head on concrete and needs more output, add a third.
 
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