Hi there, first post in subwoofers 
http://www.diyaudio.com/forums/showpost.php?p=373696&postcount=3
I'm looking at building two smallish efficient subs for home use, mainly music. I'm not a basshead, but I think the L18 boxes I'm building will not be able to take too much juice and was thinking of crossing them over at the low end. The Lab12 is locally available unlike the Dayton woofers (those cost over $350 after adding shipping and customs ), as are some of the JBL pro sub drivers.
I don't have very much power (LM4780 BPA, ~150-180 watts max) so I need efficiency over extension/xmax, though I'd like to hit about 25-30Hz in-room. I don't need it to be very loud either, just enough to take the load off the L18 woofers at the very bottom (<60Hz).
My boxes came out a bit different from sreten's calculations in the linked post - 3.5cuft (not small but not too big) with a single 4x3 port, tuned to 26Hz, -3dB at 26 Hz, 111 dB SPL with 180 watts and well within the driver's excursion limits. Room is 22x18x12 ft, and two of these will be used in a stereo configuration (budgets permitting).
Does this look good to go or am I missing something? I've never built a sub before, or even needed one so I'm not sure if this is the right way to go.
TIA for your help
http://www.diyaudio.com/forums/showpost.php?p=373696&postcount=3
I'm looking at building two smallish efficient subs for home use, mainly music. I'm not a basshead, but I think the L18 boxes I'm building will not be able to take too much juice and was thinking of crossing them over at the low end. The Lab12 is locally available unlike the Dayton woofers (those cost over $350 after adding shipping and customs
), as are some of the JBL pro sub drivers.I don't have very much power (LM4780 BPA, ~150-180 watts max) so I need efficiency over extension/xmax, though I'd like to hit about 25-30Hz in-room. I don't need it to be very loud either, just enough to take the load off the L18 woofers at the very bottom (<60Hz).
My boxes came out a bit different from sreten's calculations in the linked post - 3.5cuft (not small but not too big) with a single 4x3 port, tuned to 26Hz, -3dB at 26 Hz, 111 dB SPL with 180 watts and well within the driver's excursion limits. Room is 22x18x12 ft, and two of these will be used in a stereo configuration (budgets permitting).
Does this look good to go or am I missing something? I've never built a sub before, or even needed one so I'm not sure if this is the right way to go.
TIA for your help
Looks very good, congrats on that.
You could (if you wish) tune lower, and get a f3 of 23Hz, by tuning in the 22-23Hz region.
There are many designs on the Eminence site, the small version looks quite nice - small box, f3 of 40Hz.
Alternatively, a small, sealed box and a Linkwitz Transform circuit may do better, as a sealed box protects the driver from over-excursion below port tuning, and yu can choose how low you want it to go. I did that for my first sub, turned out well. Advice on that: don't try to make it go below 30Hz, the excursion will be huge, and not much music goes down there, but when it does, you'll get alot of nasty distortion...
Another idea - buy 2 of those drivers, make a small sealed box and use iso-brarik loading.
Whatever you go for, good luck with it.
Chris
You could (if you wish) tune lower, and get a f3 of 23Hz, by tuning in the 22-23Hz region.
There are many designs on the Eminence site, the small version looks quite nice - small box, f3 of 40Hz.
Alternatively, a small, sealed box and a Linkwitz Transform circuit may do better, as a sealed box protects the driver from over-excursion below port tuning, and yu can choose how low you want it to go. I did that for my first sub, turned out well. Advice on that: don't try to make it go below 30Hz, the excursion will be huge, and not much music goes down there, but when it does, you'll get alot of nasty distortion...
Another idea - buy 2 of those drivers, make a small sealed box and use iso-brarik loading.
Whatever you go for, good luck with it.
Chris
i have 2 lab12's in a 4th order bandpass. very small, very low & loud, very inefficient. 89.X dB is very inefficient.. but once driven with enough power the sound is incredible.
the lab12's are pretty unique. originally designed for a HUGE horn (LABhorn) with enormous SPL in low-end, but also perfect for cabinets not much bigger then the speaker itself.
if you want efficiency, i'm afraid you need to seek other speakers..
the lab12's are pretty unique. originally designed for a HUGE horn (LABhorn) with enormous SPL in low-end, but also perfect for cabinets not much bigger then the speaker itself.
if you want efficiency, i'm afraid you need to seek other speakers..
@chris, I was thinking of two drivers for sure. Somehow I'm losing SPL when I load the drivers with an isobaric enclosure. Any idea what's up with that?
@powerflux, I don't have many options in this country, unfortunately. The alternatives if shipped in from USA or Europe, will end up at $400 each. There are a few JBL pro drivers I can get my hands on, so if there are any recommendations in the $150 range (per driver) I'd be glad to take a look. I have only about 150 watts of power on tap though, so I'll need something more efficient than a 87dB Dayton.
As a guide, my main rig is a pair of 85dB/w spakers and an 80 watt amp, and I usually turn deaf after about 30 watts. I am assuming the 110 dB output per sub (with these drivers and amps) should be enough given this situation.
@powerflux, I don't have many options in this country, unfortunately. The alternatives if shipped in from USA or Europe, will end up at $400 each. There are a few JBL pro drivers I can get my hands on, so if there are any recommendations in the $150 range (per driver) I'd be glad to take a look. I have only about 150 watts of power on tap though, so I'll need something more efficient than a 87dB Dayton.
As a guide, my main rig is a pair of 85dB/w spakers and an 80 watt amp, and I usually turn deaf after about 30 watts. I am assuming the 110 dB output per sub (with these drivers and amps) should be enough given this situation.
Can you please share your design? I'd be interested to have a go. I have 2 of these drivers and would like to cover the low end to go with Fostex 168 Sigmas; enormous amp power is not a problem for me. Thanks.
let me search, it's on a scrap paper somewhere
the design was for PA, with the absolute minimum size possible in mind. this makes the cabinet very instable (0.5 litre too much in one chamber is disastrous). there are better designs (labhorn), but not smaller with the same response!this is the pre-final design:
-3dB points: 38Hz, 117Hz.
the response is near-flat between 50Hz-90Hz with 2dB gain wich gives 118dB SPL @ ~750W according to winisd - no problem for the drivers. i measured 116dB @ 300W, never had the chance to measure full-power but i expect 118 is possible.
the response is as you can tell absolutely PA.
and now the chambers: front 18L, rear 21L. pipe: 10CM dia, 20CM lenght.. so: very very very small. use good stuffing/padding or else the higher harmonics will ruin the sound.
the final design is somewhere on scrap paper, but it doesn't differ much from this one. i believe the rear chamber is a tad bigger.
i can't say the sub is musical, but the bass is very tight and controlled. did some open-air cinema last summer. if you want to go lower; a TL or horn is the way to go i think. but i don't know if that's a good match for the lab12.
to test the drivers i'd build one of the cabinets from the spec-sheet from eminence. they can't be bad if you add extra bracing
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That's the catch with isobaric, using 2 drivers to create a new single driver with halve the Vas, thus losing 3 dB efficiency compared to a single driver in a cabinet twice the size. You're also missing the coupling of using two drivers, in seperate enclosures. So using 2 drivers in a cabinet 4 times the size of the single isobaric enclosure means 6 dB higher sensitivity in the bass range.
Best regards Johan
Thanks - but wouldn't I get the same gain in output level if I use 2 separate boxes twice the size of the Isobaric box? I also was thinking two subs would be significantly easier to place than a single humongous one. I do get the fact about the net cancellation of forces within the box with opposed dirvers, though, just wondering which approach will work better.
Hi there, first post in subwoofers
http://www.diyaudio.com/forums/showpost.php?p=373696&postcount=3
I'm looking at building two smallish efficient subs for home use, mainly music. I'm not a basshead, but I think the L18 boxes I'm building will not be able to take too much juice and was thinking of crossing them over at the low end. The Lab12 is locally available unlike the Dayton woofers (those cost over $350 after adding shipping and customs
I don't have very much power (LM4780 BPA, ~150-180 watts max) so I need efficiency over extension/xmax, though I'd like to hit about 25-30Hz in-room. I don't need it to be very loud either, just enough to take the load off the L18 woofers at the very bottom (<60Hz).
My boxes came out a bit different from sreten's calculations in the linked post - 3.5cuft (not small but not too big) with a single 4x3 port, tuned to 26Hz, -3dB at 26 Hz, 111 dB SPL with 180 watts and well within the driver's excursion limits. Room is 22x18x12 ft, and two of these will be used in a stereo configuration (budgets permitting).
Does this look good to go or am I missing something? I've never built a sub before, or even needed one so I'm not sure if this is the right way to go.
TIA for your help
That is a big box, but given your limited power it will provide more sensitivity around Fb. I would consider a 20 or even 18 Hz tuning given the size of the box and Xmax capability of the driver. You'll get a more gradual rolloff that should match room gain with better power handling down low. Also, be sure to have enough port area to avoid compression due to turbulance. Multiple ports make sense here. This is the idea:
http://www.svsound.com/products-sub-box-pb13ultra.cfm
Yes to your most recent question, two boxes that allow you to position them more favorably with your mains.
Thanks, that's very reassuring
Re. ports, would you think a 4x3 square port will do the job? It's already pretty long this way, a bigger port will become bigger than the length of the box itself And wouldn't more ports also become pretty long? I seem to get 2-3x the length of a single a port when I add more (keeping port diameter the same, and I don't want to drop to 2 inch ports with a sub this big even given that I'm not pushing too much air)...
I suppose a downfiring port allows a slightly shorter length - in which case, how much of the floor volume should I lump with the port volume? Half? More? Less?
Re. ports, would you think a 4x3 square port will do the job? It's already pretty long this way, a bigger port will become bigger than the length of the box itself
And wouldn't more ports also become pretty long? I seem to get 2-3x the length of a single a port when I add more (keeping port diameter the same, and I don't want to drop to 2 inch ports with a sub this big even given that I'm not pushing too much air)...I suppose a downfiring port allows a slightly shorter length - in which case, how much of the floor volume should I lump with the port volume? Half? More? Less?
Lab12 surround.
The Lab12 has a foam surround. Eminence says that it's compressed from a large chunk of foam material. Foam typically rots in our hot humid climate . However they have not had any complaints. Does this version of foam really manage to stay without deterioration ? ( Bangalore isn't quite as hot or humid as other parts of the country !)
The Lab12 has a foam surround. Eminence says that it's compressed from a large chunk of foam material. Foam typically rots in our hot humid climate . However they have not had any complaints. Does this version of foam really manage to stay without deterioration ? ( Bangalore isn't quite as hot or humid as other parts of the country !)
I don't know about that. I have a set of four locally made woofers with foam surrounds, which had been in storage for the last five years (and are about seven years old). The storage conditions were abysmal - they were wrapped in newspaper and left in a very hot attic, and the humidity in Calcutta hits 95% at times.
They seem to be fine, with no cracks or other damage at all, and the woofers seem to be working just as well as they did when I put them away. I think foam rot may be long-term issue, like 15 years maybe. I have not yet encountered it myself.
They seem to be fine, with no cracks or other damage at all, and the woofers seem to be working just as well as they did when I put them away. I think foam rot may be long-term issue, like 15 years maybe. I have not yet encountered it myself.
Yes, all foam surrounds are not the same. I have seen some rot within 18 months ! Some do last very much longer. It's possible that the material used nowadays is also quite different or treated some way. But it always worries me. Rubber surrounds are much better here . At least they don't fall apart with time.
I built four Lab subs way back when the project was first started on PSW.
I don't recall how long it has been... maybe nine years. They still perform well after being stored pratically outdoors in Texas all this time.
They will be part of an outdoor festival rig next weekend.
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