lab-12 6ohm 20hz ht sub design? - diyAudio
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Old 28th May 2015, 08:51 AM   #1
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Default lab-12 6ohm 20hz ht sub design?

Hi has anyone made a ht sub utilising the lab-12 6ohm version.

Was looking at replicating the bk monolith ht sub which is a ported design.

want it to drop to around 20hz.

have tried searching but most are tapped horn designs or very large enclosures.

Im prob looking at a sealed or ported design around 90-120l max.
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Old 28th May 2015, 09:06 AM   #2
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a ported design is likely to have a cabinet volume double that of a tapped horn or compact horn.
A sealed design capable of similar SPL is likely to have quadruple the volume of the horn types.

If we take the 600litre Danley 35Hz horn as the "standard", then one cannot get 20Hz into less than 300litres and still give adequate SPL.

If you want/need LF extension and adequate SPL, then one CANNOT expect small cabinet volume !
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Old 28th May 2015, 09:22 AM   #3
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sorry my bad...by large I meant tall enclosures.

I want to build something to sit next to my sofa. so something down/forward firing that will look like a side table of sorts.

I've been playing in win isd and I came up with a 90l enc that hit 20hz at -6db
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Last edited by avnewbee; 28th May 2015 at 09:28 AM.
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Old 28th May 2015, 10:12 AM   #4
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by avnewbee View Post
...........................

I want to build something to sit next to my sofa.................. I came up with a 90l enc that hit 20hz at -6db
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Originally Posted by AndrewT View Post
..................................If you want/need LF extension and adequate SPL, then one CANNOT expect small cabinet volume !
I really meant it.
you have three connected conditions
High/low efficiency
High/low LF extension
High/low box volume

You cannot get low LF extension and low box volume and high efficiency all from the same design.
You have to give up at least one.
eg give up high efficiency and target Low LF extension combined with low box volume results in a very low sensitivity speaker that needs a Linkwitz Transform and ENORMOUS power to achieve adequate SPL at LF..
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Old 28th May 2015, 10:28 AM   #5
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Hi Andrew I understand what you are saying. Do you have a suggestion for a design that can sit next my sofa but is not taller than say 70cm?

I am not after high spl and aslong I can power it via an affordable amp like the behringer inuke1000 then this project is worth considering.

Driver I can get for around 115. Amp for about 135. Cabinet no cost.

Basically im trying to replicate something similar to the bk monolith plus subs which retail for around 550. They use a lab-12 driver in a 95l enclosure tuned to 20hz
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Old 28th May 2015, 11:32 AM   #6
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Quote:
Originally Posted by AndrewT View Post
a ported design is likely to have a cabinet volume double that of a tapped horn or compact horn.
A sealed design capable of similar SPL is likely to have quadruple the volume of the horn types.

If we take the 600litre Danley 35Hz horn as the "standard", then one cannot get 20Hz into less than 300litres and still give adequate SPL.

If you want/need LF extension and adequate SPL, then one CANNOT expect small cabinet volume !
Ported designs are around half the volume of THs for the same cutoff, and ported loses ~6dB over the TH, both of them excursion limited.
Sealed designs can be very very small, so long as you've still got the power handling to EQ the low end back into shape.

"Adequate SPL" here might be 110dB. Given an 87dB@1w speaker and 200w, you're there.
The things you're talking about are for outdoor PA use, where we want to be able to do 110dB 100m back. Fine, you need 150dB at a metre. Easy to do, but simply not relevant to this thread.


avnewbee, you've correctly identified what you'd need to do to replicate the BK sub. I'd say its worth getting an NU3000DSP - with the extra power, you could later build a 2nd cabinet and run both off one amplifier. Having an amp with DSP is a good idea for this sort of thing. Remember you're going to need to put the amplifier in another room, or open it up and change the fan.
Download WinISD Pro/Alpha and play around with ported boxes. The biggest challenge will be to choose a port size that's a good compromise between chuffing at high volumes, and still fits inside the box.

Chris
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Old 28th May 2015, 11:45 AM   #7
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Originally Posted by chris661 View Post


avnewbee, you've correctly identified what you'd need to do to replicate the BK sub. I'd say its worth getting an NU3000DSP - with the extra power, you could later build a 2nd cabinet and run both off one amplifier. Having an amp with DSP is a good idea for this sort of thing. Remember you're going to need to put the amplifier in another room, or open it up and change the fan.
Download WinISD Pro/Alpha and play around with ported boxes. The biggest challenge will be to choose a port size that's a good compromise between chuffing at high volumes, and still fits inside the box.

Chris
Thanks Chris

Yes I've read about the fan mod and defo intend on that route as I cant put the amp in another room.

have been playing with winisd will see what effect the port sizes have...though when I selected 2 ports it didn't seem to have an effect on anything.
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Old 28th May 2015, 12:05 PM   #8
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You need to check the port velocity graph - that'll change with power input, tuning frequency, port area etc.
Selecting two ports ought to make WinISD recalculate the length of the port, in order to keep your tuning frequency the same.

Chris
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Old 28th May 2015, 12:50 PM   #9
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You need to check the port velocity graph - that'll change with power input, tuning frequency, port area etc.
Selecting two ports ought to make WinISD recalculate the length of the port, in order to keep your tuning frequency the same.

Chris
am I supposed to be looking for the largest diameter port or smaller. Win isd is automatically changing the port lengths and I notice that if I select a port with a smaller diameter it is shorter in length?

however I am only noticeing a change to the freq magnitude graph in winisd pro alpha and not the newer winisd beta
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Old 28th May 2015, 04:15 PM   #10
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Pro Alpha is the newest one. If you're only changing the diameter of the port, the vent speed should change, but the frequency response should not.

Smaller port = shorter length, and also more chuffing (losses at high volume).

Chris
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