The smaller the box, the higher the ratio of the gross exterior to net interior volume.
13.5 x 50L gross boxes could fit in the volume of one Skhorn, a gain of 22.6dB over one cabinet, within 2.5 dB of it's output, assuming the output meets the simulation. Using higher power, higher excursion drivers and PRs could make a 2.5-6dB output gain possible using double to four times the power.
That said, far easier to move and set up one cabinet than 13.5, and the tiny boxes will cost a lot more (probably more than double) in drivers, passive radiators, amplifiers, cabling and hardware.
13.5 x 50L gross boxes could fit in the volume of one Skhorn, a gain of 22.6dB over one cabinet, within 2.5 dB of it's output, assuming the output meets the simulation. Using higher power, higher excursion drivers and PRs could make a 2.5-6dB output gain possible using double to four times the power.
That said, far easier to move and set up one cabinet than 13.5, and the tiny boxes will cost a lot more (probably more than double) in drivers, passive radiators, amplifiers, cabling and hardware.
Yes, SPL density is very expensive.
When I was planning for my next rig, I was contemplating the range of two to eight bass bins. The eight would certainly outdo the two, but the price (and time to build) it gets pretty bad. One should probably stop at four against one. 13 against one is a nightmare.
This is just a case of the audio nerdiness many of us have, to have that compact little powerhouse. There is something to it.
When I was planning for my next rig, I was contemplating the range of two to eight bass bins. The eight would certainly outdo the two, but the price (and time to build) it gets pretty bad. One should probably stop at four against one. 13 against one is a nightmare.
This is just a case of the audio nerdiness many of us have, to have that compact little powerhouse. There is something to it.
Yep, I'm still looking for that compact little powerhouse.
I made some loud noises in the back garden the other day. I put the measurement mic at 1m from the nearest part of each cabinet, and then used my old SPL meter to calibrate REW's levels. NB - while online reviews suggest the SPL meter is okay (ie, within a couple of dB of reality), I'd still recommend that the absolute SPL is taken with some degree of uncertainty.
The SPL graphs were measured at 2.83V (according to the Powersoft T602) and then at increasing power levels until the amplifier ran out of headroom. The amp was bridged for the 18XL1800.
NB - the T602 is rated for 1300/2500/3000w into 8/4/2ohm per channel. Bridged is 5000/6000w into 8/4ohm.
The three cabinets are:
Each SPL graph has the output at 2.83V, and then the last 10dB of output are in 2dB steps up to full power.
Notes from the measurements:
Finally, I spent a bit of time looking at this website: https://trace-book.org/
Where people upload their measurements of commercial cabinets. A lot of the 12" and 15" subwoofers have a frequency response that peaks around 60Hz. No wonder they're loud and "punchy". My 12" design trying to dig flat to 40Hz will obviously fall far behind in output. Perhaps it's time to re-evaluate my design goals.
Chris
I made some loud noises in the back garden the other day. I put the measurement mic at 1m from the nearest part of each cabinet, and then used my old SPL meter to calibrate REW's levels. NB - while online reviews suggest the SPL meter is okay (ie, within a couple of dB of reality), I'd still recommend that the absolute SPL is taken with some degree of uncertainty.
The SPL graphs were measured at 2.83V (according to the Powersoft T602) and then at increasing power levels until the amplifier ran out of headroom. The amp was bridged for the 18XL1800.
NB - the T602 is rated for 1300/2500/3000w into 8/4/2ohm per channel. Bridged is 5000/6000w into 8/4ohm.
The three cabinets are:
- The 12RS1066 + 2x PRs that's been documented so far
- The 18XL1800 in a sealed box which has its own thread running. As time goes on, I'm less and less convinced that these drivers in sealed boxes are useful in PA situations.
- A Void 12-600B in a 40Hz ported box. Looked like a fun driver, so I bought it off eBay and built it a cabinet a few years ago. It's not bad, all things considered, and does fine on its own for the smaller shows that I work on. This is the benchmark to beat.
Each SPL graph has the output at 2.83V, and then the last 10dB of output are in 2dB steps up to full power.
Notes from the measurements:
- All subs had a 150Hz 24dB/octave lowpass for the high-SPL measurements. It looks like I kept that for the 12RS1066, but the other two are full-range.
- The sealed 18" didn't have a highpass filter. The 12"s did. Both around 34Hz.
- The Void driver shows weirdly high sensitivity - around 3dB higher than the other two subs. I seem to have misplaced the T/S parameters that I've measured, but it might've been a 4ohm driver.
- The 18XL1800 compresses at the top of the range. The impedance is lower there, so I suspect the motor is struggling to deal with that much current.
- The Void 12" sub is showing serious distress at full power. The frequency response shows weird things happening, and harmonic distortion is very high.
- The 12RS1066+2PR is the cleanest of the bunch at full power, but even at 40Hz, it was the quietest.
- The 12RS1066 curves show driver forwards vs driver firing upwards (ie, putting all radiators a similar distance to the mic). When the driver is pointing upwards, the response is essentially flat from 40Hz upwards.
Finally, I spent a bit of time looking at this website: https://trace-book.org/
Where people upload their measurements of commercial cabinets. A lot of the 12" and 15" subwoofers have a frequency response that peaks around 60Hz. No wonder they're loud and "punchy". My 12" design trying to dig flat to 40Hz will obviously fall far behind in output. Perhaps it's time to re-evaluate my design goals.
Chris
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Internal volumes?
The three cabinets are:
The 12RS1066 + 2x PRs?
18XL1800 in a sealed box?
Void 12-600B in a 40Hz ported box?
The title of the thread is 120dB @ 40hz in 1ft3.
The three cabinets are:
The 12RS1066 + 2x PRs?
18XL1800 in a sealed box?
Void 12-600B in a 40Hz ported box?
The title of the thread is 120dB @ 40hz in 1ft3.
These cuts are clean for a testing box. Very nice job, sir. Even if you could use better HW, there is not much you can do to squeeze two more DB out of it. You´d basically need some excursion monster with 2-3kW rating and beastly amp and a third radiator. Not sure if it is wort the effort that point. It would be nearlya design with well over $1000 and as you mentioned then you do not have safery (cones coverage) solved, which will add on the box volume a lot. You had the data you need, only decision now is which reality to accept.
PA drivers need a lot more EQ down there in a sealed box and also run out of excursion. That´s where maybe LN16S400 could come in. But it is 16".
PA drivers need a lot more EQ down there in a sealed box and also run out of excursion. That´s where maybe LN16S400 could come in. But it is 16".
BP1,
The 12RS1066+2PR is 28L internal, once driver volumes have been subtracted. The Void 12" ported box is something like 50L, and the 18" is around 70L. Can't remember for sure - it's been a while since I built those, and changing my laptop has lost some of the old Hornresp records.
In terms of output density, it's still my best sub. As you've noted, though, it's not hitting 120dB@40Hz. Apologies.
Crash, thanks for the kind words. I think three PRs would be required to get everything out of the 12RS1066, but even so, it's only going to save the ~2dB of compression we're seeing at 40Hz with sine tones. Probably not an issue with real program material.
As you've noted, cone safety still hasn't been solved.
I suppose there are a few directions I can go from here.
Current inventory: 3x 18XL1800, 4x 12RS1066 (bought the set at a silly-cheap price), 1x Void 12".
I'd like to stick with the T602 amplifier. It's a good bit of kit which has performed well under circumstances where lesser amps would have been very unhappy.
Back to Hornresp for another round of sims.
Chris
The 12RS1066+2PR is 28L internal, once driver volumes have been subtracted. The Void 12" ported box is something like 50L, and the 18" is around 70L. Can't remember for sure - it's been a while since I built those, and changing my laptop has lost some of the old Hornresp records.
In terms of output density, it's still my best sub. As you've noted, though, it's not hitting 120dB@40Hz. Apologies.
Crash, thanks for the kind words. I think three PRs would be required to get everything out of the 12RS1066, but even so, it's only going to save the ~2dB of compression we're seeing at 40Hz with sine tones. Probably not an issue with real program material.
As you've noted, cone safety still hasn't been solved.
I suppose there are a few directions I can go from here.
Current inventory: 3x 18XL1800, 4x 12RS1066 (bought the set at a silly-cheap price), 1x Void 12".
I'd like to stick with the T602 amplifier. It's a good bit of kit which has performed well under circumstances where lesser amps would have been very unhappy.
Back to Hornresp for another round of sims.
Chris
Been there, called that. The speaker safety will take a lot of space. I would consider accepting some risk and just mounted some "anti bump" car audio style rods in front of these, otherwise you end up wit finding that bassreflex takes less space. 😀🤭
I think using the Bose layout in one of my previous posts would help with the safety aspect, with only a small increase in cabinet volume (approx 8L).
I might try building that layout next. The woodworking will be considerably more difficult than a simple cuboid, though.
Chris
I might try building that layout next. The woodworking will be considerably more difficult than a simple cuboid, though.
Chris