Building a DIY Subwoofer through a builder

[mbhangui]

Hi all,

@randhir_s and myself, both noobs as far as subwoofer goes and are planning to get a subwoofer built through one of few builders that Randhir has managed to locate. Both of us reside in Pune. Usage will be for both HT and stereo.

We have questions

1. Should we go for ported or sealed?
2. Is very low frequency extension good (20 Hz and below)?
3. One or two subwoofers?
4. 10" or 12" or larger (our music room sizes are probably roughly around 150 to 200 sq ft)
5. How much impact the driver has on the quality? So IWAI, Pioneer or SB acoustics?
6. Class ABCDEFG (what kind of amp) to drive the driver
7. Crossover details
8. Any recommended builder?

These are the links to some drivers that we have shortlisted (without any criteria). Please take both of us total noobs. If there are better ones, please suggest the same.

1. https://pioneer-india.in/buy/car-entertainment-car-subwoofers-champion-series/ts-w1212s4/
2. https://sbacoustics.com/product/12in-sb34swpl76-4/
3. https://iwaispeakers.com/product-detail/12-long-throw-subwoofer-4ω-200w/

 

[arunkvivek]

Hi all,

@randhir_s and myself, both noobs as far as subwoofer goes and are planning to get a subwoofer built through one of few builders that Randhir has managed to locate.

We have questions

1. Should we go for ported or sealed?
2. Is very low frequency extension good (20 Hz and below)?
3. One or two subwoofers
4. 10" or 12" or larger (our music room sizes are probably roughly around 150 to 200 sq ft)
5. How much impact the driver has on the quality? So IWAI, Pioneer or SB acoustics?
6. Class ABCDEFG (what kind of amp) to drive the driver
7. Any recommended builder?

If you can manage to place SW away from walls, H frame Open baffles subwoofers are the best VFM. If your real estate forces you to place SW closer to the wall or in corners, then box (ported, sealed or transmission line) is to be chosen.

 

[mbhangui]

If you can manage to place SW away from walls, H frame Open baffles subwoofers are the best VFM. If your real estate forces you to place SW closer to the wall or in corners, then box (ported, sealed or transmission line) is to be chosen.

Is this what you mean by H Frame. Sorry I have no idea of H Frame or transmission line

 

[arunkvivek]

Is this what you mean by H Frame. Sorry I have no idea of H Frame or transmission line
View attachment 88033

Yes, this is h frame... A form of open baffle. It is the easiest to make and if you can manage to get 1 meter space behind the speaker, you would get unbelievable bass.
I have been using them for past 5 years. You can check with FMs like @Hari Iyer @yogibear who have guided many on open baffle builds

 

[mbhangui]

Yes, this is h frame... A form of open baffle. It is the easiest to make and if you can manage to get 1 meter space behind the speaker, you would get unbelievable bass.
I have been using them for past 5 years. You can check with FMs like @Hari Iyer @yogibear who have guided many on open baffle builds

Thank you @arunkvivek. Will consult both Hari and Yogi tomorrow.

 

[Yelamanchili manohar]

Hi all,

@randhir_s and myself, both noobs as far as subwoofer goes and are planning to get a subwoofer built through one of few builders that Randhir has managed to locate. Both of us reside in Pune. Usage will be for both HT and stereo.

We have questions

1. Should we go for ported or sealed?
2. Is very low frequency extension good (20 Hz and below)?
3. One or two subwoofers?
4. 10" or 12" or larger (our music room sizes are probably roughly around 150 to 200 sq ft)
5. How much impact the driver has on the quality? So IWAI, Pioneer or SB acoustics?
6. Class ABCDEFG (what kind of amp) to drive the driver
7. Crossover details
8. Any recommended builder?

These are the links to some drivers that we have shortlisted (without any criteria). Please take both of us total noobs. If there are better ones, please suggest the same.

1. https://pioneer-india.in/buy/car-entertainment-car-subwoofers-champion-series/ts-w1212s4/
2. https://sbacoustics.com/product/12in-sb34swpl76-4/
3. https://iwaispeakers.com/product-detail/12-long-throw-subwoofer-4ω-200w/

Hello Sir

Iam no authority on subwoofers. But below are my 2 cents

1. Ported or sealed :
Ported :
Advantages - Goes lower and will be more effecient and less demanding on power doing so.
Disadvantages - Needs a bigger box than sealed, Poor design can lead to chuffing noise from the port, transient attack in the 100 to 60hz region is slower than sealed box, port induces group delay on the driver output.
Sealed :
Advantages - Smaller box than ported, has a more gradual bass roll of at -12db per octave so easier to get room placement correct, sounds more dynamic with better transient attack and speed.
Dsiadvantages - Needs more power, doesnt go as low in the bass as ported, needs better heat management in the design to avoid the driver voice coil from over-heating.

2. Very low frequency extension below 20hz - Not needed for music, unless one listens to western classical with lots of pipe organs playing , but will be nice to have for HT.

3. One or two - More the merrier, 2 is better than 1 and 4 is better than 2

4. 10 or 12 inch - The bigger the better. Best to go for the largest one can fit. But the box gets bigger with a bigger driver. So space is the main consideration when choosing driver size.

5. Quality of driver - From what I'v read, good subwoofer drivers need not cost a lot, unlike bass drivers. There is a minimum quality requirement that has to met, beyond that, I would spend money on buying 2 or 4 drivers with the money, rather than buying one very high quality driver.

6. Amplifier - Any Class D or AB is fine. I would personally choose class D for more effeciency. For music, the hypex plate amps come with dsp, so the sub can be setup with dsp for better integration into the room and system. However for HT, I would'nt bother, as the AVR will do the room correction and integration anyways.

7. Crossover - Will depend on how the system is setup as whole. Will need more details of the exact chain to elaborate further.

8. I know Sadik Bhai builds great quality and gorgeous looking peices.

 

[Yelamanchili manohar]

Just putting it out there, without suggesting anything

The top wilson speakers come with two bass drivers. The upper bass driver is sealed, and goes till about 60 hz. This gives speed, slam and transient attack. The lower bass driver is ported, this starts at around 60hz and goes all the way to 16hz. This is the best combination for getting speed, slam, transient attack, bass depth and dynamics right.

However, creating a passive low pass filter at 60hz is challenging and will take lots of space. So best done in the digital realm for normal folks like us.

 

[mbhangui]

Hello Sir

Iam no authority on subwoofers. But below are my 2 cents

1. Ported or sealed :
Ported :
Advantages - Goes lower and will be more effecient and less demanding on power doing so.
Disadvantages - Needs a bigger box than sealed, Poor design can lead to chuffing noise from the port, transient attack in the 100 to 60hz region is slower than sealed box, port induces group delay on the driver output.
Sealed :
Advantages - Smaller box than ported, has a more gradual bass roll of at -12db per octave so easier to get room placement correct, sounds more dynamic with better transient attack and speed.
Dsiadvantages - Needs more power, doesnt go as low in the bass as ported, needs better heat management in the design to avoid the driver voice coil from over-heating.

2. Very low frequency extension below 20hz - Not needed for music, unless one listens to western classical with lots of pipe organs playing , but will be nice to have for HT.

3. One or two - More the merrier, 2 is better than 1 and 4 is better than 2

4. 10 or 12 inch - The bigger the better. Best to go for the largest one can fit. But the box gets bigger with a bigger driver. So space is the main consideration when choosing driver size.

5. Quality of driver - From what I'v read, good subwoofer drivers need not cost a lot, unlike bass drivers. There is a minimum quality requirement that has to met, beyond that, I would spend money on buying 2 or 4 drivers with the money, rather than buying one very high quality driver.

6. Amplifier - Any Class D or AB is fine. I would personally choose class D for more effeciency. For music, the hypex plate amps come with dsp, so the sub can be setup with dsp for better integration into the room and system. However for HT, I would'nt bother, as the AVR will do the room correction and integration anyways.

7. Crossover - Will depend on how the system is setup as whole. Will need more details of the exact chain to elaborate further.

8. I know Sadik Bhai builds great quality and gorgeous looking peices.

Sir, each and every point of yours is logical and is what I have kind of arrived at, based on law of physics. Bigger the better is plain simple physics. Larger the surface area, lower the resonant frequency. Also my thought was that quality of the driver is not so important as the case for higher frequencies. Here we are are just compressing and de-compressing air at such a lethargic rate that even a tortoise fed 'muli ka parotha' can probably achieve. At such low frequency the speed is also not so important. Since speed etc are not so important and we have such a small frequency range to operate, the choise of amp also is not so important.

Now I'm not so sure about using a crossover or DSP. My less than 8 k Piano dac that does DSP to seperate LF from HF produces fantastic quality that other dacs costing at least 8x cannot do. So I'm contemplating to implement a DSP solution rather than a crossover. Any thoughts on this?

 

[Yelamanchili manohar]

Sir, each and every point of yours is logical and is what I have kind of arrived at, based on law of physics. Bigger the better is plain simple physics. Larger the surface area, lower the resonant frequency. Also my thought was that quality of the driver is not so important as the case for higher frequencies. Here we are are just compressing and de-compressing air. At such low frequency the speed is also not so important. Since speed etc are not so important and we have such a small frequency range to operate, the choise of amp also is not so important.

Now I'm not so sure about using a crossover or DSP. My less than 8 k Piano dac that does DSP to seperate LF from HF produces fantastic quality that other dacs costing at least 8x cannot do. So I'm contemplating to implement a DSP solution rather than a crossover. Any thoughts on this?

Hello again sir
I would always go with digital crossovers over passive, more so for subwoofers where high quality low pass filters will get very big and very expensive. And same can be done with commensurate quality, with more flexibility and a lot cheaper in the digital realm. If your source or streamer has twin digital outputs, then one can be fed to the paino dac to act as a dac cum digital crossover cum dsp unit to feed the amps running the subwoofer. The second output of the streamer, can feed your other dac feeding the main speakers.

And since your goodselves seem to be considering low frequency performance, ideally below 60hz, then ported will be better. But box will get bigger

I would humbly suggest to spend some time on Diyaudio.com site, as there are lots of subwoofer builds there, which have been very well documented with detailed build pics and drawings. Better to clone a proven design, with some effort expended on getting the exact same driver used in the build, rather than try to build a sub with whatever driver is available in india, and then struggling with the design. The box, build and design is as important, if not more important than the driver itself

 

[mbhangui]

Hello again sir
I would always go with digital crossovers over passive, more so for subwoofers where high quality low pass filters will get very big and very expensive. And same can be done with commensurate quality, with more flexibility and a lot cheaper in the digital realm. If your source or streamer has twin digital outputs, then one can be fed to the paino dac to act as a dac cum digital crossover cum dsp unit to feed the amps running the subwoofer. The second output of the streamer, can feed your other dac feeding the main speakers.

And since your goodselves seem to be considering low frequency performance, ideally below 60hz, then ported will be better. But box will get bigger

I would humbly suggest to spend some time on Diyaudio.com site, as there are lots of subwoofer builds there, which have been very well documented with detailed build pics and drawings. Better to clone a proven design, with some effort expended on getting the exact same driver used in the build, rather than try to build a sub with whatever driver is available in india, and then struggling with the design. The box, build and design is as important, if not more important than the driver itself

Your points noted. I do have multiple digital outputs using what is know as MPD (Music Player Daemon) on my macbooks, linux and raspberry PI. My Piano DAC has 2 outputs (2 L+R for subwoofer and 2 L+R for high pass). In addition to that I have two Toppings DAC (D10 balanced and E30) connected to the same raspberry PI. The subwoofer out is connected right now to a Polk subwoofer which cannot go below 30 Hz.

This is currently my Piano DAC feeding the subwoofer and two v3 mono blocks. The visualization in the middle is the bass. Towards the left and right are the higher frequencies. The phone doesn't capture the low frequencies somehow. This is just felt in the chest and the body. I want to improve this low frequency response and hence the quest to build a better subwoofer than Polk

https://photos.app.goo.gl/CchEzSvrR9zSa18U7

 

[Yelamanchili manohar]

Your points noted. I do have multiple digital outputs using what is know as MPD (Music Player Daemon) on my macbooks, linux and raspberry PI. My Piano DAC has 2 outputs (2 L+R for subwoofer and 2 L+R for high pass). In addition to that I have two Toppings DAC (D10 balanced and E30) connected to the same raspberry PI. The subwoofer out is connected right now to a Polk subwoofer which cannot go below 30 Hz.

This is currently my Piano DAC feeding the subwoofer and two v3 mono blocks. The visualization in the middle is the bass. Towards the left and right are the higher frequencies. The phone doesn't capture the low frequencies somehow. This is just felt in the chest and the body. I want to improve this low frequency response and hence the quest to build a better subwoofer than Polk

https://photos.app.goo.gl/CchEzSvrR9zSa18U7

Thanks sir. Phones always struggle with lower bass

Your goodselves can leave the configuration exactly as it is, and just replace the polk with your new DIY subwoofer fed by a normal power amp. So the piano dac's present subwoofer output will go directly to the power amp driving the DIY sub. And the crossover setting for low pass, can be configured in the piano dac.

Iam not familiar with MPD software etc...but there might be ways to configure the crossover in the playback software itself ( Jriver etc ), which will then also enable input of delays if any, on different channels, to get better time alignment between the sub and speakers. Used this way, Rpi can feed the piano for subwoofer, and the same Rpi can feed the topping dac for higher frequencies played by the main speakers. Time delays if any, due to processing latency in the piano dac or topping, or due to dissimilar distances to sub and speakers, can then be offset in the MPD software itself.

 

[Hari Iyer]

Ported subwoofer will have a higher Q point and could be boomy and difficult to integrate with mains. Also bass can be one note chest thumping type. If you like and enjoy that then ported sub is for you.

On the otherhand a sealed sub with a lower Q will have a gentle roll-off and a more natural and realistic sounding bass and will be easy to integrate with main speaker.

OB bass will again be a low Q and will require carefully driver selection to get a good extension down to 20hz. There will be a dipole roll-off due to baffle width and also a dipole peak which needs to be compensated with a notch filter and a low pass shelving compensator without which integration with main speakers could be a challenge.

 

[yogibear]

H frame if you are willing to cross low, like 140-120Hz to avoid the dipole peak. And ofcourse a suitable driver. It can be a single or dual driver, running active as I prefer it. If done right, it’s a concert level sound / bass. Great experience both for music or even for movies. Very simple to build and you can use room corrections too if needed. However good quality, low distortion driver is a better choice as you can dig really deeper. However you can also go cheap with inexpensive drivers suitable for OB and enjoy H frame bass. Depends on your choice of budget for the project.

I will be taking another take at an OB project just because I have some drivers suitable for the job so wish to put them to use. MTM OB passive mated to H frame, active. Would be a learning experience too…

My early H frame adventures:





And a very enjoyable U frame : loads of different FRs were rolled in this setup.

 

[Hari Iyer]

H frame if you are willing to cross low, like 140-120Hz to avoid the dipole peak

To avoid dipole peak even at 120hz you will need a baffle width of 56 inches which imo is not practical in a living room. You will need both a low pass shelving @ -6db from this dipole peak onwards and also a notch filter at this dipole peak again at -6db to level the response with the mains.

So it all boil downs to how well you can calculate and measure your dipole peak and add compensation for that. Otherwise it will be a difficult project to implement IME.

 

[yogibear]

To avoid dipole peak even at 120hz you will need a baffle width of 56 inches which imo is not practical in a living room. You will need both a low pass shelving @ -6db from this dipole peak onwards and also a notch filter at this dipole peak again at -6db to level the response with the mains.

So it all boil downs to how well you can calculate and measure your dipole peak and add compensation for that. Otherwise it will be a difficult project to implement IME.

I followed Martins directions for H frame construction.

 

[Hari Iyer]

I followed Martins directions for H frame construction.

So as per his direction what is the dipole peak frequency for say a 15" baffle. Martin paper does not talk about dipole roll-off or peak. It talks about mechanical crossover frequency for the h-frame. Linkwitz Lab pages explain the dipole roll-off and dipole peaks in detail

 

[mbhangui]

Is there a specific size/dimensions of the H frame that has to be chosen based on the driver parameters. Or is the H frame dimensions purely dependendent on the driver size?

 

[kapvin]

Sir, each and every point of yours is logical and is what I have kind of arrived at, based on law of physics. Bigger the better is plain simple physics. Larger the surface area, lower the resonant frequency. Also my thought was that quality of the driver is not so important as the case for higher frequencies. Here we are are just compressing and de-compressing air at such a lethargic rate that even a tortoise fed 'muli ka parotha' can probably achieve. At such low frequency the speed is also not so important. Since speed etc are not so important and we have such a small frequency range to operate, the choise of amp also is not so important.

Now I'm not so sure about using a crossover or DSP. My less than 8 k Piano dac that does DSP to seperate LF from HF produces fantastic quality that other dacs costing at least 8x cannot do. So I'm contemplating to implement a DSP solution rather than a crossover. Any thoughts on this?

Piano DAC: yes. this makes immense sense.

A lot will depend on the capability of your builder. the choice of sealed vs ported is determined not just by driver choice, but also room, and desired box size. but if you have the piano dac and you can get a copy of TI software for programming it, it is an excellent well sounding option. to integrate the sub with all the necessary DSP.

if your builder is more of a carpenter, then it might be useful to choose a rigid well braced sealed box. if your builder is a "black box" kinda guy, well then, I guess you have to choose whether to trust him or not.

I think your approach is logical and you have the basics very right. The choice of amp is a bit important, as there will be resonance peaks (and a saddle if you are going ported) in the operating range, so it should be able to those without a hiccup. (but most well designed Class AB amps should be okay and many Class D as well).

some questions:

1. what's the size of your room.
2. how loud do you play your music.
3. where would you place the Sub (in the corner/ under the next to the main) elsewhere
4. which mains do you use. You r signature says RTI A9, and those are one set, which nor known for being bass shy!!

best wishes

Edit: PS the reason I ask these questions is that I see a lot of advice being given on the the forum based on personal experiences and listening choices. following those will only give joy if you listen choices and environment matches the advisor's. please use first principles do zero in on your requirements and then decide on other issues. for eg an H-frame is really nice bass with most kinds of music, but if you listen above moderate levels your amp size and driver excursion requirements become HUGE.

 

[Hari Iyer]

The H- frame box dimensions will be purely dictated by the driver size. A 2 x12" woofer having a low compliance suspension, a Qts oof 0.7+ and a resonance around 25hz to 35hz should be good enough. If the plate amplifier is lower wats then the driver will benefit from lower MMS too. Because of the lower Q at LF, the H- frame will roll-off rapidly @ 12dB/ octave below the dipole peak until resonance of the driver and after that 6db/ octave below the baffle width rolloff. So total roll-off will be around 18db/ octave. Some kind of EQ will be required at the LF to restore the balance using a LP shelving and a notch filter. Failure to do this will make it difficult to integrate with the main speakers. If you this, then enjoy bliss for rest of your audio life.

 

[mbhangui]

Piano DAC: yes. this makes immense sense.

A lot will depend on the capability of your builder. the choice of sealed vs ported is determined not just by driver choice, but also room, and desired box size. but if you have the piano dac and you can get a copy of TI software for programming it, it is an excellent well sounding option. to integrate the sub with all the necessary DSP.

if your builder is more of a carpenter, then it might be useful to choose a rigid well braced sealed box. if your builder is a "black box" kinda guy, well then, I guess you have to choose whether to trust him or not.

I think your approach is logical and you have the basics very right. The choice of amp is a bit important, as there will be resonance peaks (and a saddle if you are going ported) in the operating range, so it should be able to those without a hiccup. (but most well designed Class AB amps should be okay and many Class D as well).

some questions:

1. what's the size of your room.

Around 150 sq ft.

2. how loud do you play your music.

Not loud. The sound cannot be heard inside other rooms.

3. where would you place the Sub (in the corner/ under the next to the main) elsewhere

I have space only in the front left and right (behind the main speakers).

4. which mains do you use. You r signature says RTI A9, and those are one set, which nor known for being bass shy!!

I have two pairs (RtiA8 and Cadence Arista)