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Planning a TL sub

Hari Iyer

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This project was on my mind now for quite some time. The only deterrent was space in my living room. To get deep bass you need at least a 10" woofer and a largish box to do justice. Now this goes against me. But can i cramp something in a small space. Though its a challenge, i tried simulating some 10" paper cone drivers using LA, Basta and found only a ML TL can fit my bill. Under consideration were SB acooustics, Bolton, Peerless & Dayton 10" woofers. Hope this project will get the light of the day.
 
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elangoas

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The only deterrent was space in my living room. To get deep bass you need at least a 10" woofer and a largish box to do justice.
You know the "how of DIY speakers / stuff" since you have been a DIYer.. Sealed boxes require lesser dimensions than that of ported ones.. Since you said you are cramped on space, why not consider multiple smaller sealed box (shallow depth)..

Also external amplification will give you the advantage of placing the subs (treating it like a speaker) according to the room dimension (or) to your liberty of room space.. All this from my recent DIY experience..
 

blackscorpio

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You know the "how of DIY speakers / stuff" since you have been a DIYer.. Sealed boxes require lesser dimensions than that of ported ones.. Since you said you are cramped on space, why not consider multiple smaller sealed box (shallow depth)..

Also external amplification will give you the advantage of placing the subs (treating it like a speaker) according to the room dimension (or) to your liberty of room space.. All this from my recent DIY experience..
Sealed & external amplification... LOVE it. Sealed for musicality & External amplification for placement ease.
 

Hari Iyer

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Thanks elango & blackscorpio for your perspective.

TBH, I never did a sealed box simulation because of the rolloff concern. I am looking at this subwoofer primilarly to fill the bottom octave below 40 Hz. My current OB FS speakers clearly covers from 40 Hz till 20kHz+. What I am probably missing is below 40 Hz which is so very important for dynamics.

I discovered that the time tested humble Bass Reflex subwoofer fills the gap quite well and also has a smaller box that can manage to accommodate my cramped space (BTW I have kept all of this secret from my family members as of now).

The response is flat till 32 Hz and - 3dB response is 26Hz and -10dB is 19 Hz. This response will go well to fill the bottom octave which I am looking to address.

I have ordered the driver and plate amplifier today. Hope to complete this project in another one to two months time.
 

Hari Iyer

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As of now, vented design is now on the cards. I will not be stuffing the box at all. Since half of the back panel will be occupied by the plate amp, I shall lineup only bottom half of the back panel. Will line up the bottom and top panel. Side panel shall be lined only on the bottom side just half the box. Care need to be taken to not increase this above 170 grams total. Felt will be only 4 mm thick.
Anything more sucks out the LF energy as per simulation.
 

raghupb

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Thanks elango & blackscorpio for your perspective.

TBH, I never did a sealed box simulation because of the rolloff concern. I am looking at this subwoofer primilarly to fill the bottom octave below 40 Hz. My current OB FS speakers clearly covers from 40 Hz till 20kHz+. What I am probably missing is below 40 Hz which is so very important for dynamics.

I discovered that the time tested humble Bass Reflex subwoofer fills the gap quite well and also has a smaller box that can manage to accommodate my cramped space (BTW I have kept all of this secret from my family members as of now).

The response is flat till 32 Hz and - 3dB response is 26Hz and -10dB is 19 Hz. This response will go well to fill the bottom octave which I am looking to address.

I have ordered the driver and plate amplifier today. Hope to complete this project in another one to two months time.
What genre of music has instruments with their frequency in 20Hz - 40Hz.
I can think of only Tuba, Harp and Double Bass. Even these are usually tuned and played at higher frequencies.

Not that I am dissuading you from your passion; just a question.
Cheers,
Raghu
 

arj

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What genre of music has instruments with their frequency in 20Hz - 40Hz.
I can think of only Tuba, Harp and Double Bass. Even these are usually tuned and played at higher frequencies.

Not that I am dissuading you from your passion; just a question.
Cheers,
Raghu
Raghu, I guess while the fundamental frequency is how you mentioned everything will have a subharmonic in this range which makes the sound richer. Hence a 80hz instrument will also have a f/4 at 20Hz which is low in amplitude but gives the tonality to the instrument.

nice article here -https://en.wikipedia.org/wiki/Talk:Subharmonic

Hari, interested in your experiment..although from what i have garnered a sealed box gives you better control over the driver hence better musicality, unless you use a very powerful amp..
 

raghupb

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Hmmm...
Ok got it now. Thanks.
Cheers,
Raghu
 
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Hari Iyer

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What genre of music has instruments with their frequency in 20Hz - 40Hz.
I can think of only Tuba, Harp and Double Bass. Even these are usually tuned and played at higher frequencies.

Not that I am dissuading you from your passion; just a question.
Cheers,
Raghu
TBH, i dont know. But the extra thump in the bottom octave is what i am looking for with this project. Hope it delivers.
 

Hari Iyer

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Hari, interested in your experiment..although from what i have garnered a sealed box gives you better control over the driver hence better musicality, unless you use a very powerful amp..
Yes, a sealed enclosure has a better group delay and control, but the roll-off is of a bit concern. I did a quick simulation in winisd and got an F3 of just 48Hz. This defeats the purpose of the subwoofer for me as my OB anyway covers that range.
 

Hari Iyer

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some simulation images with LA for the vented enclosure. Volume is 89L tuned at 29Hz. Stuffing around 170 grams. port area 7 sq.inch, length 5.5 inch.
As you can see from the SPL image, the output from the driver is very less and most of the output is from the port.
 

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Naveenbnc

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I did a quick simulation in winisd and got an F3 of just 48Hz. This defeats the purpose of the subwoofer for me as my OB anyway covers that range.
Sir, this is not a suggestion, as I am not as knowledgeable as you are. This is sort of a question/opinion.
Of course in a pureist perspective, we can argue that music recordings or instruments won't go that low.
So there is not point in using a sub for music. I personally like deep bass for music even if it doesn't represent the original low end from the recording.

Even if your OB covers 48Hz, it may sound a lot different when the same freq, is produced by a sub.

For example, a freq range of 200Hz to 100Hz may sound a lot different to our ears, when it is produced by a 3" FR Vs a 15" bass driver.
Low end produced by different drivers/speakers sound different to our ears even if they play the same freq spectrum.

If my opinion is correct, building a sub makes sense even if your OB covers 48Hz. But seamless integration is a challenge to match the sound signature etc. (please correct me if I am wrong)
 

Hari Iyer

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Hi Naveenbnc,
Thanks for sharing your thoughts. Below is the simulated response of my OB speaker


If you notice, there is a gain of +4dB in the response from 100Hz onwards which continues till 20KHz. This gain gives me good presence and energy, but at the cost of low frequency loss. With the subwoofer i am trying to address this issue. I could have added a baffle step compensator to address this issue, but again that causes other issues with the overall phase of the speaker system. I tried one and did not enjoy with the BSC. So the only option to get the LF lift was to add a subwoofer for the range from 100Hz downwards. I will keep the LF cutover at 80Hz or below as i want the sub to disappear from the room.
 

Naveenbnc

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Understood Hari,

I hope you are getting Dayton Audio DC250-8 10". Looks like it may need minimum 3.5 Cu.Ft volume enclosure in case of bass reflex.
I don't know how to estimate TL any way. Pretty exciting....and wish you all the best !!! :):)
 

Hari Iyer

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Understood Hari,

I hope you are getting Dayton Audio DC250-8 10". Looks like it may need minimum 3.5 Cu.Ft volume enclosure in case of bass reflex.
I don't know how to estimate TL any way. Pretty exciting....and wish you all the best !!! :):)
Yes, 85 L should do, I am building with 89L.
 

keith_correa

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Sir, this is not a suggestion, as I am not as knowledgeable as you are. This is sort of a question/opinion.
Of course in a pureist perspective, we can argue that music recordings or instruments won't go that low.
So there is not point in using a sub for music. I personally like deep bass for music even if it doesn't represent the original low end from the recording.

Even if your OB covers 48Hz, it may sound a lot different when the same freq, is produced by a sub.

For example, a freq range of 200Hz to 100Hz may sound a lot different to our ears, when it is produced by a 3" FR Vs a 15" bass driver.
Low end produced by different drivers/speakers sound different to our ears even if they play the same freq spectrum.

If my opinion is correct, building a sub makes sense even if your OB covers 48Hz. But seamless integration is a challenge to match the sound signature etc. (please correct me if I am wrong)
I'm not "Sir" but you're absolutely correct!
 

Hari Iyer

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Seamless integration of sub from the mains is a nightmare experience. This is where the major challenge lies. I am hoping that as my OB covers welll till 40Hz, the bottom octave below 40Hz should be able to blend as those frequencies are more felt than heard. I myself am not a subwoofer fan and just trying my luck out here. Also my budget for doing this is trival so that i can sell them if its not suitable for my setup. Having said that, i also like to add, that my elder brother uses a TL sub built by me and it integrates quite well to my micro-TL speaker which he has connected to the DNM amplifier. I always listen to his setup whenever i visit him on the weekends.
 

raghupb

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Seamless integration of sub from the mains is a nightmare experience. This is where the major challenge lies. I am hoping that as my OB covers welll till 40Hz, the bottom octave below 40Hz should be able to blend as those frequencies are more felt than heard. I myself am not a subwoofer fan and just trying my luck out here. Also my budget for doing this is trival so that i can sell them if its not suitable for my setup. Having said that, i also like to add, that my elder brother uses a TL sub built by me and it integrates quite well to my micro-TL speaker which he has connected to the DNM amplifier. I always listen to his setup whenever i visit him on the weekends.
Unless you have an amp with some kind of bass management, integration will be trial and error before you get it right.
AVRs do have intelligence and help to an extent.
Cheers,
Raghu
 
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