DIY sub to complement my 3 way DIY

[arunvenkats]

Recently a friend of mine gave me a SMSL AO300 DAC and power amp. If you remember I made a 3 way which is currently being powered by a Fosi Audio V3 Stereo Power Amplifier. I am very happy with my current setup. But because I have a spare amp (Fosi Audio V3) and SMSL AO300 DAC has a sub out, I am itching to build a sub to complement the current setup. Expecting my only expense being a driver and an enclosure.

First, do you guys think I should add a sub at all? If so, what would be a good budget driver. I am very happy with the peerless driver I used to build my 3 way.

This is a music only scenario. Not using the speaker as any part of a home theatre system. Neither will be the sub.

For reference, this is my 3 way build:

A

Thread '3 way sealed speaker'

Jan 18, 2025

Hi folks,

Happy to present my first serious audio project. A DIY Speaker build. After a couple of months of design, and couple of weeks of sourcing and building the speaker is ready. The speaker itself was ready 3 weeks back, but was waiting for the Dayton calibrated mic to arrive to do an objective measurement. Got the results now, what do you think? Of course the SPL chart is not really the speaker performance alone, it is the speaker+room combination. Recorded at 75dB. Comments and suggestions are most welcome.

The design is a sealed unit. I do not have the...

• arunvenkats
• Replies: 30
• Forum: DIY

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Regards,
Arun

 

[ajuvignesh]

Since you’re into DIY, you can experiment H frame subwoofers and this is perfect for music

 

[diyaudio]

@arunvenkats , will you be able to do EQ needed for H frame?

 

[morerajendra5678]

You can build a subwoofer with 18inch driver to be powered by your Fosi amp V3.

 

[arunvenkats]

Since you’re into DIY, you can experiment H frame subwoofers and this is perfect for music

Thanks for the input. I never knew about H frame and dipole subwoofers. Would love to experiment! More research showed me more dipole designs like W frame and the Ripole. I will research. Thanks for the direction. I am definitely building one of these types.

Regards,
Arun

 

[arunvenkats]

@arunvenkats , will you be able to do EQ needed for H frame?

@diyaudio The AO300 already has sub out. If I connect it with my Fosi Amp to it, I assumed just the volume control in the Fosi should do the EQ. Is my assumption correct?

 

[arunvenkats]

You can build a subwoofer with 18inch driver to be powered by your Fosi amp V3.

I have some space constraint. A 18" driver will have a huge speaker enclosure volume requirement. But I am going to explore the H-Frame and other dipole arrangements mentioned in this thread. They do not have the same volume requirement. But I have a feeling an 18" might be overkill for my music-only requirement and the 8" woofers it is going to complement.

 

[diyaudio]

If this is your first project, go for two 12" sealed subs ie stereo subs, you already have 2 channel amp and sub out. Take JBL car sub driver, they are quite good, make two 14" cubes and stuff them with polyester fill from pillows. You wont be able to beat this system at price to performance ratio.

If you can give 3 feet of empty space behind the H baffle then I can help with the design, you will need active EQ circuit that you will have to build/solder it or use DSP, both are equally valid options. If you take this approach, DM me as I am building an H frame myself.

 

[diyaudio]

Maybe I was not clear, first option is sealed stereo sub, placement against walls, the latter is H frame placed atleast 3 feet from wall behind them

 

[dafreaking]

If this is your first project, go for two 12" sealed subs ie stereo subs, you already have 2 channel amp and sub out. Take JBL car sub driver, they are quite good, make two 14" cubes and stuff them with polyester fill from pillows. You wont be able to beat this system at price to performance ratio.

If you can give 3 feet of empty space behind the H baffle then I can help with the design, you will need active EQ circuit that you will have to build/solder it or use DSP, both are equally valid options. If you take this approach, DM me as I am building an H frame myself.

Do you mean something like this? https://amzn.in/d/2WyQ32B - Jbl A1300Hi 1300W Wired Subwoofer

So a sealed sub wouldn't the Frequency response be limited in the low end?

 

[diyaudio]

Do you mean something like this? https://amzn.in/d/2WyQ32B - Jbl A1300Hi 1300W Wired Subwoofer

So a sealed sub wouldn't the Frequency response be limited in the low end?

Yes, same sub.
I recommended a sealed sub if its a first build and I recommended two subs to increase SPL and ease of room integration.
If one can get ported right its better and if one can get PR right one can make a smaller sub than ported which is even better

 

[dafreaking]

Yes, same sub.
I recommended a sealed sub if its a first build and I recommended two subs to increase SPL and ease of room integration.
If one can get ported right its better and if one can get PR right one can make a smaller sub than ported which is even better

But my question remains. Won't a sealed sub like this struggle at the low end?

 

[diyaudio]

But my question remains. Won't a sealed sub like this struggle at the low end?

It depends on how much SPL one wants and how big a room does one listen in, smaller the room, higher the SPL. Two 12" subs give more surface area than a single15", and 10mm Xmax of each driver provides lot of SPL

 

[arunvenkats]

Yes, same sub.
I recommended a sealed sub if its a first build and I recommended two subs to increase SPL and ease of room integration.
If one can get ported right its better and if one can get PR right one can make a smaller sub than ported which is even better

I cannot find any Thiele-Small (T/S) parameters for JBL A1300Hi. Looks like it is not public. How can we design the speaker box for sealer/ported?

Regards,
Arun

 

[diyaudio]

One can measure T/S with a cheap soundcard and simulate in Unibox/Winisd and find out that 12" drivers works well in 15" cube sealed and stuffed. I measure using LIMP on laptop and it works great.

One can also port it to 25Hz for which T/S params are not needed, box volume and Helmholtz resonance (aka box tuning frequency) dont depend on the driver, pls dont get me wrong, to see the frequency response T/S are indeed needed.

Also the simulated response is overshadowed by the room modes (peaks and dips) and the simulated response is lost, though this should not deter to DIY. In fact it is due to this that one needs dual subs and DIY really pays off.

Also, in measurement, we want to see peaks and dips, so the scale of graph must be kept less, with a high scale it give a false impression that response is closer to flat

 

[dafreaking]

Measure Thiele Small parameters using free software - Audio Judgement

Learn how to measure thiele small parameters, or just a speaker impedance measurement using your sound card. Software used: Room EQ Wizard.

audiojudgement.com

 

[morerajendra5678]

But my question remains. Won't a sealed sub like this struggle at the low end?

You can go in for subs with 18inch driver if you want end game result. You will find plans to built them in website of B&C speakers, Eminence and Beyma also. SB Audience have been used by few in my circle with great results.