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post #1 of 23 Old 03-16-2017, 06:46 PM - Thread Starter
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Combining Two DIYSoundGroup Sub Enclosures to Make One Sub

Can I combine two 18" ported cubes from DIYSoundGroup to make a single large dual Sub? I was thinking of just gluing them together side by side and drilling a hole between them just small enough to pass speaker wire. Wire them in parallel and use a single Speakon connector to run em both. Is this a terrible idea. I'd prefer to have one box rather than two. I'd make my own but I already have the flat pack kits.

Thanks!

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post #2 of 23 Old 03-16-2017, 07:03 PM
 
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You can't smooth room response with dual subs that aren't spread well apart, and smoothing room response is the primary reason for having two or more subs.
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post #3 of 23 Old 03-16-2017, 07:06 PM - Thread Starter
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These are basically gonna be 18" Nearfield Mid-Bass modules. I'm putting PA460 drivers in em to get some more "slam" in the upper bass region. I already have an SI 18" in a Stonehenge enclosure for lower bass.
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post #4 of 23 Old 03-16-2017, 07:07 PM - Thread Starter
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I basically want to operate em to only increase SPL in the upper bass region. I'm pleased with my bass response in my main seating locations.
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post #5 of 23 Old 03-16-2017, 07:17 PM
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post #6 of 23 Old 03-16-2017, 07:36 PM - Thread Starter
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What do you recommend I seal the ~1/4" hole between the two boxes for the speaker wire with? PL Premium or some construction adhesive?
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post #7 of 23 Old 03-17-2017, 04:09 AM
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Why not just set them down right next to each other? Connecting them won't help any, and will only make them harder to move.
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post #8 of 23 Old 03-17-2017, 04:32 AM
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Quote:
Originally Posted by Samps View Post
Why not just set them down right next to each other? Connecting them won't help any, and will only make them harder to move.
This

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smoothing room response is the primary reason for having two or more subs.
Well if you're OCD it's not
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post #9 of 23 Old 03-17-2017, 06:46 AM - Thread Starter
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Why not just set them down right next to each other? Connecting them won't help any, and will only make them harder to move.


I suppose I could and then just make a Speakon Y-Connector, right?
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post #10 of 23 Old 03-17-2017, 07:41 AM
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You probably wouldn't want to glue the back vertical section of the port on because you might be tuning the box too low for the PA460's.

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post #11 of 23 Old 03-17-2017, 08:33 AM - Thread Starter
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You probably wouldn't want to glue the back vertical section of the port on because you might be tuning the box too low for the PA460's.


So you recommend leaving it off to shorten the port length? What will this raise the tune to roughly?
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post #12 of 23 Old 03-17-2017, 08:36 AM
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I'm not sure, you would have to model the PA460 and see what it should be tuned to. I've never tried fitting one of those in the Cube-18. The dimensions look close enough to work, but I have not tried it.

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post #13 of 23 Old 03-17-2017, 08:44 AM - Thread Starter
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I'm not sure, you would have to model the PA460 and see what it should be tuned to. I've never tried fitting one of those in the Cube-18. The dimensions look close enough to work, but I have not tried it.


Ok, thanks. The V.B.S.S. system uses the PA460 in a ported box to around a 20Hz or 31Hz tune (you can select by plugging ports) and people seem to be happy with them. I figured with your alls flat pack at around 19 Hz, it would work well.


The V.B.S.S. DIY subwoofer design thread


I'm a little new at this, but would I get more upper bass output if I tuned the box higher? I'm gonna have these two PA460 18" units bandpassed basically from 50-150 Hz. The 20-50 Hz region will be fulfilled by SI 18" in a Stonehenge enclosure. This will all be handled (hopefully) by a miniDSP 2x4 I ordered.


ETA: Looking at the output graphs in the thread I linked, it seems the output from 50 Hz + is the same regardless of the box tune they used.
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post #14 of 23 Old 03-17-2017, 09:16 AM
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I'm not an expert, but I think if you're only looking for output in the 50 - 150 Hz region, you'll do much better with a higher tune for the enclosure. Don't ported subs generally have the most output around tuning? It seems like you'd be giving up a lot if you're tuned to 19Hz, but I guess if the sims tell you it's the same, then it won't make much difference. Did you run a sim tuned to 50Hz? 60Hz? Just to see what happens...
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post #15 of 23 Old 03-17-2017, 09:22 AM - Thread Starter
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Originally Posted by OJ Bartley View Post
I'm not an expert, but I think if you're only looking for output in the 50 - 150 Hz region, you'll do much better with a higher tune for the enclosure. Don't ported subs generally have the most output around tuning? It seems like you'd be giving up a lot if you're tuned to 19Hz, but I guess if the sims tell you it's the same, then it won't make much difference. Did you run a sim tuned to 50Hz? 60Hz? Just to see what happens...


Nope, I don't even have the program. I've never ran a sim and tend to go off what people have already posted here. Although I'm not sure this particular combo has been done, I figured the V.B.S.S. build was close enough to give it a shot. I'm still hung up on some of the basics of sub design and am just getting started figuring this all out. I have a 18" Stonehenge build with an SI 18" I built a few years ago, but I just hooked it up, ran Audyssey and away I went. Now I'm getting more into it.


Attached is a pic of the frequency response for the V.B.S.S. in that thread (credit to mtg90) that was run using the box at 3 different tuning frequencies. The box is similar in size to the DIY SoundGroup 18" cube and the 20 Hz tune is pretty much what that box is so I figured they'd be real similar. Am I wrong? Also, this doesn't answer the question of if a 40-50 Hz would be better, either. When I get off work, I will try to teach myself WinISD or whatever program it is people use.

Real basic question here, would not using the rear wall of the port as Eric H suggested about raise the tune of the box since it is reducing the port length? Could this lead to chuffing/port noise since the port may now be too small? Or would not running sub 50 Hz frequencies to the sub negate this? Man, so many variables haha.
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post #16 of 23 Old 03-17-2017, 12:52 PM
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If you want Mid Bass above 40Hz you need to purchase a Mid Bass Module, aka MBM from Erich. The Flat Pack with the custom 12" driver made for Denovo by Eminence is an outstanding driver. This will provide more than ample Midbass from 40 on up and you can use your SIs in the sub 40s if that's the route you want to go. You don't need an 18" driver to do Midbass, the custom 12" is more efficient and designed for just this.

If I'm reading this post correctly that's my recommendation. I'd put the SIs in the cube or the Stonehenge both have same tune and net volume.

Enjoy! Oh our first world problems!....
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post #17 of 23 Old 03-17-2017, 02:51 PM
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Quote:
Originally Posted by M88@FL450 View Post
If you want Mid Bass above 40Hz you need to purchase a Mid Bass Module, aka MBM from Erich. The Flat Pack with the custom 12" driver made for Denovo by Eminence is an outstanding driver. This will provide more than ample Midbass from 40 on up and you can use your SIs in the sub 40s if that's the route you want to go. You don't need an 18" driver to do Midbass, the custom 12" is more efficient and designed for just this.

If I'm reading this post correctly that's my recommendation. I'd put the SIs in the cube or the Stonehenge both have same tune and net volume.

Enjoy! Oh our first world problems!....
What do you power the MBM with?
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post #18 of 23 Old 03-17-2017, 03:55 PM - Thread Starter
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Originally Posted by M88@FL450 View Post
If you want Mid Bass above 40Hz you need to purchase a Mid Bass Module, aka MBM from Erich. The Flat Pack with the custom 12" driver made for Denovo by Eminence is an outstanding driver. This will provide more than ample Midbass from 40 on up and you can use your SIs in the sub 40s if that's the route you want to go. You don't need an 18" driver to do Midbass, the custom 12" is more efficient and designed for just this.

If I'm reading this post correctly that's my recommendation. I'd put the SIs in the cube or the Stonehenge both have same tune and net volume.

Enjoy! Oh our first world problems!....
Several people on here have made MBMs with 18" drivers. Although my enclosures may need a little modification, I think these will work well. Plus I already have everything purchased. My room is 3500 cubic feet so I get no room gain and need some impact. I will power em both from a Crown XLS 2502 I already have. With a little help I think I can meet or exceed the MBMs. Hopefully

I appreciate the insight but if I order more crap my wife will kill me so these 18s we gotta figure out haha.
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post #19 of 23 Old 03-17-2017, 07:24 PM
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Quote:
Originally Posted by mikeTRON250LM View Post
Quote:
Originally Posted by M88@FL450 View Post
If you want Mid Bass above 40Hz you need to purchase a Mid Bass Module, aka MBM from Erich. The Flat Pack with the custom 12" driver made for Denovo by Eminence is an outstanding driver. This will provide more than ample Midbass from 40 on up and you can use your SIs in the sub 40s if that's the route you want to go. You don't need an 18" driver to do Midbass, the custom 12" is more efficient and designed for just this.

If I'm reading this post correctly that's my recommendation. I'd put the SIs in the cube or the Stonehenge both have same tune and net volume.

Enjoy! Oh our first world problems!....
What do you power the MBM with?
500 watts (real measured not exaggerated marketing claims) will bring these to XMAX in a 40ish tuned cab like the MBM DIY Flatpak.
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post #20 of 23 Old 03-17-2017, 11:25 PM
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Originally Posted by WVSubs View Post
Several people on here have made MBMs with 18" drivers. Although my enclosures may need a little modification, I think these will work well. Plus I already have everything purchased. My room is 3500 cubic feet so I get no room gain and need some impact. I will power em both from a Crown XLS 2502 I already have. With a little help I think I can meet or exceed the MBMs. Hopefully

I appreciate the insight but if I order more crap my wife will kill me so these 18s we gotta figure out haha.
The DIY Groups Mag 12 is 93dB sensitivity 12" with 9mm of Xmax, the PA460 is 97 dB sensitivity 18" with 6mm of Xmax.

I included a WINISD comparing the two. You would have to use twice as many Mag 12s($160) to beat the PA460($100) and also the Mag 12s would need2x as much power(Inuke 6000 $325) so it would end up costing you much more to go with Mag12s.
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post #21 of 23 Old 03-19-2017, 01:42 PM
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IMO your plan of putting the PA460s in a couple of Cube 18s sounds great.

If you can measure every dimension of the port on the CUBE 18, we could do some modeling for you (Height, Width, Length along Bottom, Length along Back wall).
As @Erich H said you could leave off the back section of the port to raise the tune. Eye-balling the dimensions (2x16x25 bottom, 2x16x15 back) this model does raise the the box tune slightly: 19Hz -> about 23.15Hz (according to WinISD). This does seem better for your purposes. But I think you can go even higher like 40-50Hz tune.

I tried the PA380 in various box sizes and with various tunes (some posts about this in my nearfield cabinet thread). Basically my conclusion is that changing the tune (35-75Hz) didn't affect the sound too much in 50-100Hz region and didn't change the Frequency response a whole lot. Obviously it did some, but not as much as I thought it would.

I'd say either way you'll have great output in 50-150Hz region. BUT I think if you can easily raise the tune of the box to 40-50Hz, I think you'll get better impact from them if your intention is to have nearfield MBM subs for 50-150Hz. (A lot of this is based on discussion in the MBM thread - better tactile response around port tune due to higher PSD Particle Velocity or whatever it is).

A 40Hz box tune is a nice curve in that box size with the PA460 (sorry can't post graphs right now). Assuming a 2x16 port HxW, you could bring the port length down to a total Length of only 5 or 6 inches to get a 40Hz tune in that 5.4 cu ft box. (all numbers subject to change with more details)

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post #22 of 23 Old 03-19-2017, 06:31 PM - Thread Starter
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IMO your plan of putting the PA460s in a couple of Cube 18s sounds great.

If you can measure every dimension of the port on the CUBE 18, we could do some modeling for you (Height, Width, Length along Bottom, Length along Back wall).
As @Erich H said you could leave off the back section of the port to raise the tune. Eye-balling the dimensions (2x16x25 bottom, 2x16x15 back) this model does raise the the box tune slightly: 19Hz -> about 23.15Hz (according to WinISD). This does seem better for your purposes. But I think you can go even higher like 40-50Hz tune.

I tried the PA380 in various box sizes and with various tunes (some posts about this in my nearfield cabinet thread). Basically my conclusion is that changing the tune (35-75Hz) didn't affect the sound too much in 50-100Hz region and didn't change the Frequency response a whole lot. Obviously it did some, but not as much as I thought it would.

I'd say either way you'll have great output in 50-150Hz region. BUT I think if you can easily raise the tune of the box to 40-50Hz, I think you'll get better impact from them if your intention is to have nearfield MBM subs for 50-150Hz. (A lot of this is based on discussion in the MBM thread - better tactile response around port tune due to higher PSD Particle Velocity or whatever it is).

A 40Hz box tune is a nice curve in that box size with the PA460 (sorry can't post graphs right now). Assuming a 2x16 port HxW, you could bring the port length down to a total Length of only 5 or 6 inches to get a 40Hz tune in that 5.4 cu ft box. (all numbers subject to change with more details)
Thanks so much! I actually installed WinISD and was playing around with it assuming a 18x2" port and figured I had to have It around 2 inches in length for a 40hz tune! I'll know more and post more when my boxes arrive this week. A problem I'm running into is that I'm doubling the cone excursion of the woofer at only like 400W of input power lol. How do I keep from damaging them if they're powered by my Crown XLS2502? Is that cone excursion chart very accurate? Run the gain on the amp down?
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post #23 of 23 Old 03-19-2017, 08:38 PM
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On a ported box like this you would run a High Pass Filter on the signal. Amps with DSP can do this or a standalone DSP.
The HPF would be set around the box tune 38-40Hz or something and would cut the signal below that point. That would limit excursion below 40Hz and keep the driver within operating range. You can apply a theoretical filter in WinISD to see how it affects cone excursion.

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