cheap DIY subwoofer

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KaffiMann

KaffiMann

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Vented box on this driver makes no sense.
Here is a sim for 90 liters sealed, I seriously doubt you will see numbers this good in a bass reflex, even if you double the budget for drivers.
 

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academia50

academia50

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GM

GM

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KaffiMann said:
Vented box on this driver makes no sense.
Here is a sim for 90 liters sealed, I seriously doubt you will see numbers this good in a bass reflex, even if you double the budget for drivers.
Click to expand...

Hmm, the pioneers learned that when the box compliance balanced out the driver's compliance and is tuned to Fs, it produced the most efficient system, so based on the driver's Vas, this Vb = 3.18 ft^3/1.44 = 2.2 ft^3 [~62.3 L], which according to HR makes audibly more output at the driver's rated 240 W peak power rating down to ~20 Hz, though combined with room/boundary gain it might be a different story.

Of course it's obviously more under-damped and could be even more so if the specs are way off as the GRS 8"ers are, but not uncommon for folks to boost a sub this much, which has more distortion than when done acoustically, so while it 'flies in the face' of T/S theory, it's not de facto an alignment that should be summarily dismissed out-of-hand.

If it doesn't sound good even after damping to 'taste', this is also the right size for sealed and sims inaudibly different to your 90 L, so can stuff or outright seal up the vent.

All that said, I prefer the 160 L MLTL tuned to ~20-25 Hz as a nice trade-off between size, power handling, LF extension and if it's not too late and enough budget, recommend a 250-300 W amp if there's no close by neighbors.

Another good option that falls more in line with T/S and/or excellent transient response centric folks is a simple Alpha TL pipe tuned to ~Fs/1.0 Qt = 30 Hz, though will be huge [~350 L] and may want the amp boost option.

GM
 

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KaffiMann

KaffiMann

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When I said "numbers this good" I presented many more graphs than only the depiction of SPL/freq. Perhaps it should have been pointed out directly the benefits of better numbers such as group delay, phase, and in addition to that: ease of build.

Not dismissing any alignment, but with the 90 liters sealed box he retains a modicum of fidelity, and avoids the fridge/half fridge sized boxes that apparently where too big.
 
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bottedumal

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Joined 2011
Hi Guys,

thanks for your advices.

I now regret I didn't get that amplifier with an according power supply, that would have gave me more power for cheap. But parts-express ships amazingly quickly!

Free Shipping TAS5630+OPA1632DR+TL072 Subwoofer 600W 4ohm Mono SUB Amplifier completed board+preamplifier stereo input-in Integrated Circuits from Electronic Components & Supplies on Aliexpress.com | Alibaba Group

So i'll go on with the 100w plate amplifier hoping that will be sufficient.

The idea is not to wake up neighbors, but to have sufficient bass to support my klipsh RB61 II watching movies and listening to some bassy music, in a room not that big.

I'm seeing MLTL seems a nice option, but I might go first testing as sealed, after reading KaffiMann articles, seems a good simple and yet efficient option. Just hope the power will be sufficient to have something decent

Thanks guys
 
morgot9999

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Hello bottedumal

Have you considered car audio equipment? For a small room it may be enough, and simpler to fit.
A 10 /12 inch 250W JBL, Pioneer or any other brand should be less than 100 USD, add a 2 channel amplifier in bridge (should be cheaper than a mono for the same power) matched to the speaker RMS power, build yourself the box in MDF (70-100 liters).
For power supply use a computer PSU or a 12-14V switching power supply. Noise from the fan may be an issue.
 
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bottedumal

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morgot9999 said:
Hello bottedumal

Have you considered car audio equipment? For a small room it may be enough, and simpler to fit.
A 10 /12 inch 250W JBL, Pioneer or any other brand should be less than 100 USD, add a 2 channel amplifier in bridge (should be cheaper than a mono for the same power) matched to the speaker RMS power, build yourself the box in MDF (70-100 liters).
For power supply use a computer PSU or a 12-14V switching power supply. Noise from the fan may be an issue.
Click to expand...

Hi morgot9999, I actually already bought the equipment. My questions was more what size exactly should be a 90L box (is the height/length/large ratio not important? I can make it the sizes I want ? I imagine not, but as I don't have internet home for now, I couldn't make research. I'm still waiting the speaker and amplifier from US, when it come here, I'll try to find the answer)
 
GM

GM

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bottedumal said:
I'm sorry guys, most of this is a bit like chinese for me.
Does this suggest I should make a 90L box too ?

Thanks :)
Click to expand...

Understood! Much of it is proofing/deriving/correcting the published specs as much as practical, though by no means does it mean they are accurate compared to actually measuring yours, just gives us a 'best guess' based on available information.

There's a couple of Hornresp sims based on these 'new' specs and if you read the 'comment' line it explains what it is with one stating it's a 193.5 L offset driver [OD] tapered pipe [T-QWP] and the other a 346.5 L variant with the other plots being a stuffing and XO design recommendation; so no, he's definitely not recommending it anymore than the rest of us are.

You of course have some very specific limitations, so we have given you what we believe are acceptable compromises for you to choose from, whereas he's providing the kind of info that applies to everybody that may [someday] be of use and for those interested, mini tutorials you'll probably never find in a book unless you write it or anywhere else on the net unless someone copy/pastes it.

GM
 
GM

GM

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Joined 2003
morgot9999 said:
Hello bottedumal

Have you considered car audio equipment?
Click to expand...

+1. Most of the DIY I did decades ago had to be cheap, easy to make, compact for small spaces, so the ideal components plus a lot of folks back then had HAM radio systems, so used its DC power supply to power car radios since they could get FM from the junkyard way cheaper than buying even a cheap HIFI receiver.

GM
 
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bottedumal

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Joined 2011
GM said:
Understood! Much of it is proofing/deriving/correcting the published specs as much as practical, though by no means does it mean they are accurate compared to actually measuring yours, just gives us a 'best guess' based on available information.

There's a couple of Hornresp sims based on these 'new' specs and if you read the 'comment' line it explains what it is with one stating it's a 193.5 L offset driver [OD] tapered pipe [T-QWP] and the other a 346.5 L variant with the other plots being a stuffing and XO design recommendation; so no, he's definitely not recommending it anymore than the rest of us are.

You of course have some very specific limitations, so we have given you what we believe are acceptable compromises for you to choose from, whereas he's providing the kind of info that applies to everybody that may [someday] be of use and for those interested, mini tutorials you'll probably never find in a book unless you write it or anywhere else on the net unless someone copy/pastes it.

GM
Click to expand...

still chinese for me ahahah. not sure which comment section you are refering to
 
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bottedumal

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GM said:
+1. Most of the DIY I did decades ago had to be cheap, easy to make, compact for small spaces, so the ideal components plus a lot of folks back then had HAM radio systems, so used its DC power supply to power car radios since they could get FM from the junkyard way cheaper than buying even a cheap HIFI receiver.

GM
Click to expand...

OK. I'll know it for next time. I really hesitated with a car amplifier from aliexpress which were wayyyy cheaper than what I bought, but I didn't know if it would drive well my sub. basically, what difference between a car amp and the plate amp i bought ? sound quality ? or not really any difference at all ?
 
GM

GM

Member
Joined 2003
No clue about modern [aftermarket] mobile audio electronics beyond one runs on battery DC and the other AC, though it seems reasonable that the plate amp for a given power will cost more due to its greater parts count/complexity and in theory at least, make the DC amp the superior performing one.

GM
 
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