Getting 20Hz - 20kHz right. - Page 2 - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
Reply
 
Thread Tools
post #31 of 39 Old 04-20-2011, 07:19 PM - Thread Starter
Advanced Member
 
04FLHRCI's Avatar
 
Join Date: Dec 2005
Posts: 777
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 12
Hi coctostan,

Ok, let's base our simulation on 4 21SW152s.

The foot print we have to work with shall be 24" W x 28" D. Height is flexible, but for managability would like to keep < 72".

I know nothing of the PPSL alignment you're presenting here; I assume this is "Push Pull Slot Loaded".

I'm going to step away for a bit and enlist the aid of Google for some exposure here.

Regards,

Larry

Quote:
Originally Posted by coctostan View Post

The 21SW152 will do the best because it will have far more displacement than the other two.

If you give me some general footprint dimensions I can make a quick sketchup model to see if a PPSL will work.

04FLHRCI is offline  
Sponsored Links
Advertisement
 
post #32 of 39 Old 04-20-2011, 07:26 PM
AVS Forum Special Member
 
coctostan's Avatar
 
Join Date: Oct 2005
Location: Indy
Posts: 1,957
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 144
Quote:
Originally Posted by 04FLHRCI View Post

Hi coctostan,

Ok, let's base our simulation on 4 21SW152s.

The foot print we have to work with shall be 24" W x 28" D. Height is flexible, but for managability would like to keep < 72".

I know nothing of the PPSL alignment you're presenting here; I assume this is "Push Pull Slot Loaded".

I'm going to step away for a bit and enlist the aid of Google for some exposure here.

Regards,

Larry

Thread with some links: https://www.avsforum.com/avs-vb/showthread.php?t=1301337

It isn't something vital, but if you are trying for the best, I think it is relatively low hanging fruit.

Your footprint definitely allows for enough space. It is a matter of how you want them tuned. It will model the same as any other vented or sealed enclosure. Except there is an upper rolloff due to the low pass acoustic filter. That won't affect your modeling.

I'll have to look at it tomorrow.
coctostan is offline  
post #33 of 39 Old 04-20-2011, 07:46 PM - Thread Starter
Advanced Member
 
04FLHRCI's Avatar
 
Join Date: Dec 2005
Posts: 777
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 12
Is this what you're thinking? See post #14.

http://www.diyaudio.com/forums/subwo...-loaded-2.html

Would a design be feasable to increase the width and reduce the height to utilize the PPSL cabinet as a stand for the SH50?

Quote:
Originally Posted by coctostan View Post

Thread with some links: https://www.avsforum.com/avs-vb/showthread.php?t=1301337

It isn't something vital, but if you are trying for the best, I think it is relatively low hanging fruit.

Your footprint definitely allows for enough space. It is a matter of how you want them tuned. It will model the same as any other vented or sealed enclosure. Except there is an upper rolloff due to the low pass acoustic filter. That won't affect your modeling.

I'll have to look at it tomorrow.

04FLHRCI is offline  
Sponsored Links
Advertisement
 
post #34 of 39 Old 04-20-2011, 07:56 PM - Thread Starter
Advanced Member
 
04FLHRCI's Avatar
 
Join Date: Dec 2005
Posts: 777
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 12
I've previously looked at a ported implementation for the 21SW152, but the port area required was crazy. Will the same challenge exist in a PPSL design?

I needed a large enclosure merely to accommodate the porting. The model I ended up with was:
1 21SW152
15 cubes
18Hz tune
2 8" ports x 48" long
04FLHRCI is offline  
post #35 of 39 Old 04-21-2011, 09:13 AM
AVS Forum Special Member
 
coctostan's Avatar
 
Join Date: Oct 2005
Location: Indy
Posts: 1,957
Mentioned: 3 Post(s)
Tagged: 0 Thread(s)
Quoted: 7 Post(s)
Liked: 144
The PPSL works just like a regular ported or sealed enclosure except for how the drivers are mounted which gives you the acoustic low pass and distortion cancellation.

I would probably go with about 10 cu ft per 21SW152 and a 10" dia 22" long port for a ~19hz tuning (or dual 2.5"x15" slot ports above and below the manifold). You will give up a little output around tuning to the larger box, but I think it will be more than adequate, especially with 4 drivers. It is already going to be a very large box. The slot manifold will waste about 3 cu ft. So an ~24cu ft box for a dual 21SW152. This could be done in your 24x28x72 space. It would be a big and heavy cab, but the sound quality would be off the charts.

Another possibility would be dual 21SW152s in ~13cu ft total with 4 AE 15" PRs. My models show a tuning around 17hz. You lose about 4-5db at 20hz, but will play a little lower and is much smaller. The PRs are $65ea and would be mounted on the sides opposing each other. The response is somewhere between the 20cu ft ported from above and a 15cuft sealed. It is about 4-5db stronger than a similar sized sealed box until about 17hz and eventually the sealed passes it by around 14hz. The PR box could probably be made into a SH50 stand.

With a little EQ tweaking either of these will work great. The PR version eliminates the backwave leakage, port resonance and port compression effects. It also allows you to add weight to the PR and adjust the tuning down to the 13-14hz range. The PR box is limited to the excursion of the PRs and the ported box is limited to the point where port noise becomes a factor. A bigger port could be used but that pushes the port resonance lower.

Either way, in half space, the dual 21 4 15" PR is capable of ~116db at 20hz and the dual 21 ported is doing ~120db at 20hz. Both with 625w per driver. A single EP2500 for both boxes with 2 drivers parallel per channel would work, but more is better. The EP2500 would clip before the subs run out of steam, but your ears and house would like cry uncle before the EP2500. If I had to guess, you would need more than 500-1000w total for reference levels to 20hz.

Two of these boxes would provide enough SPL to 20hz for a small commercial theater. You could also substitute the TD18H and only lose 1-2db at the same power. There are two disadvantages to that. First, the TD18's will move more to achieve the same SPL. Second, the lower displacement TD18's won't work as well in sealed boxes if you want to try that route. The advantage to the TD18 is that it is likely the best SQ 18 on the planet.

Don't forget you will need a HP filter. A balanced MiniDSP would work great.

If this sounds interesting I can mock up a PPSL enclosure in sketchup.
coctostan is offline  
post #36 of 39 Old 04-21-2011, 09:39 AM - Thread Starter
Advanced Member
 
04FLHRCI's Avatar
 
Join Date: Dec 2005
Posts: 777
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 12
coctostan,

Lot of great thought put into this response; don't put pencil to paper yet, as I'd like to mull it over for a bit.

Larry
04FLHRCI is offline  
post #37 of 39 Old 04-21-2011, 11:03 AM
AVS Forum Special Member
 
Ricci's Avatar
 
Join Date: Mar 2007
Location: Louisville KY
Posts: 5,478
Mentioned: 166 Post(s)
Tagged: 0 Thread(s)
Quoted: 373 Post(s)
Liked: 881
If you are going to use the 21sw152 ported I would suggest tuning it not lower than about 23-25hz. I would not go over 10cu ft with it and stay closer to 8 or 9. A 10" flared port is adequate. My build was roughly 9.5 cu ft tuned to 25hz. It is a monster in this type of configuration. It was supposed to be tuned a little higher at about 28hz. If you baffle the port and leave it with less than a port diameter from the nearest wall you can scrub some of the length off of what is calculated as needed to hit a certain tune. This is how i ended up at 25hz with my ported pair. Make no mistake it can do well but t will never be a ULF engine like the 30mm xmax 18's and 21's. IMHO trying to port it down into the 15-20hz range is wasting some of its potential and forcing it into a role it is not as good at. Sealed you can run that low or lower by default but you will need a lot of eq to bring the low end up. At about 20mm excursion it is done being useful due to distortion and noise. It isn't in danger of bottoming though.
Ricci is offline  
post #38 of 39 Old 04-22-2011, 12:23 AM
Senior Member
 
Antripodean's Avatar
 
Join Date: Apr 2009
Location: The Antripodes (OZ)
Posts: 332
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 3 Post(s)
Liked: 12
Larry,
FWIW I'm using the TD18H+ each side under my Unity Horns and really enjoying them. However, I am using them from 40 to 300Hz. With an SH50 you can get down to 50Hz so there's not a lot of space for a pro sub at these freqencies. Under 40Hz I have a choice of MaelX 18s, pair of PB12 band pass cabs in series and a Peavey Low Rider 18 band pass. The latter two get down to 25Hz and that's great for music. I have ~6dB of gain thru the DCX on the sub channel. I mute the sub channel occasionally just to gauge the difference. Without the lower octave the bass is definitely weak! For movies I can engage the MaelX 18s to dig really low. If I only had to cover 50Hz down I would just use the MaelX 18s in 8 cu ft sealed cabs. You can keep it simple as long as you have enough power to really get the MaelX 18s singing

explore the music
Antripodean is offline  
post #39 of 39 Old 04-22-2011, 09:57 AM - Thread Starter
Advanced Member
 
04FLHRCI's Avatar
 
Join Date: Dec 2005
Posts: 777
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 4 Post(s)
Liked: 12
Good Points, another configuration I'm considering is HPF the SH50 @100Hz, run a pair pro subs like the JBL 4645c from 40Hz - 100Hz, and then run a pair of LMS 5400 for 10Hz - 40Hz.

edit - or HPF the SH50 @80Hz and implement multiple sealed LMS5400 or 21SW152; probably the simplest route, but I was really wanting to hear the JBL 2242H driver. I'll probably order a driver next week and start designing cabinets...

Quote:
Originally Posted by Antripodean View Post

Larry,
FWIW I'm using the TD18H+ each side under my Unity Horns and really enjoying them. However, I am using them from 40 to 300Hz. With an SH50 you can get down to 50Hz so there's not a lot of space for a pro sub at these freqencies. Under 40Hz I have a choice of MaelX 18s, pair of PB12 band pass cabs in series and a Peavey Low Rider 18 band pass. The latter two get down to 25Hz and that's great for music. I have ~6dB of gain thru the DCX on the sub channel. I mute the sub channel occasionally just to gauge the difference. Without the lower octave the bass is definitely weak! For movies I can engage the MaelX 18s to dig really low. If I only had to cover 50Hz down I would just use the MaelX 18s in 8 cu ft sealed cabs. You can keep it simple as long as you have enough power to really get the MaelX 18s singing

04FLHRCI is offline  
Sponsored Links
Advertisement
 
Reply DIY Speakers and Subs

Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page


Forum Jump: 

Posting Rules  
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off