B&C 21SW152 Ported Design Opinions - AVS Forum | Home Theater Discussions And Reviews
Forum Jump: 
 1Likes
  • 1 Post By notnyt
 
Thread Tools
post #1 of 14 Old 08-17-2017, 10:48 AM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
B&C 21SW152 Ported Design Opinions

Hey guys long time lurker, I was hoping I could get any opinions on a ported subwoofer I'm designing. This will be used heavily for music but also for movies and gaming.

I decided that response down to 25hz was the goal so a tuning of 27-28 hz was chosen.
Amplification will be a crown K2 so 2500 watts rms into 4 ohms.

Some basic specs:

Net volume: 9.03cuft (255.7L)
Port Area: 109.85 in^2 (708cm^2)
Port Length: 32" (81.28cm)
Tuning: 27.5hz
External Dimensions: 24x36x28in

I have attatched the CAD design, SPL and excursion in hornresp and port velocity from SUBSIM.

Hornresp sims have a 22hz subsonic applied and are 2pi with 100vrms

Hoping to get another opinion on the design because it looks good to me. It will constructed entirely in 18mm baltic birch.
Attached Thumbnails
Click image for larger version

Name:	21SW152 CAD Snapshot.png
Views:	76
Size:	1.10 MB
ID:	2269112   Click image for larger version

Name:	SPL.png
Views:	52
Size:	12.5 KB
ID:	2269124   Click image for larger version

Name:	Excursion.png
Views:	41
Size:	12.6 KB
ID:	2269126   Click image for larger version

Name:	Vent Velocity.png
Views:	38
Size:	85.8 KB
ID:	2269128  
BIGlep is offline  
Sponsored Links
Advertisement
 
post #2 of 14 Old 08-17-2017, 11:08 AM
AVS Forum Special Member
 
Samps's Avatar
 
Join Date: Feb 2014
Location: Pittsburgh, PA
Posts: 2,156
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 939 Post(s)
Liked: 529
Did you consider the Othorn? It's not much bigger.

You might want to add more bracing. The braces can be smaller but more of them. A single brace on a 24" wide panel with this level of spl seems underbraced.
Samps is offline  
post #3 of 14 Old 08-17-2017, 11:10 AM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
Another CAD shot showing the bracing
Attached Thumbnails
Click image for larger version

Name:	CAD1.png
Views:	52
Size:	1.18 MB
ID:	2269140  
BIGlep is offline  
 
post #4 of 14 Old 08-17-2017, 11:15 AM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
Quote:
Originally Posted by Samps View Post
Did you consider the Othorn? It's not much bigger.

You might want to add more bracing. The braces can be smaller but more of them. A single brace on a 24" wide panel with this level of spl seems underbraced.
I did consider it but I honestly don't have the confidence at this point to be able to hold the required tolerances with the tools I have on such a complex design. It's actually the eventual goal but I figured to start with ported.
BIGlep is offline  
post #5 of 14 Old 08-17-2017, 11:33 AM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
I added more bracing in this version do you think this would be sufficient
Attached Thumbnails
Click image for larger version

Name:	CAD-updated bracing.png
Views:	41
Size:	922.0 KB
ID:	2269154  
BIGlep is offline  
post #6 of 14 Old 08-17-2017, 11:45 AM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
OK I think I realise which part you were saying was underbraced. I shorted the port brace and added two pieces to support the rear panel.
Attached Thumbnails
Click image for larger version

Name:	CAD-updated bracing.png
Views:	44
Size:	1.10 MB
ID:	2269158  
BIGlep is offline  
post #7 of 14 Old 08-17-2017, 12:06 PM
AVS Forum Special Member
 
notnyt's Avatar
 
Join Date: Dec 2008
Location: Long Island, NY
Posts: 8,782
Mentioned: 217 Post(s)
Tagged: 0 Thread(s)
Quoted: 2791 Post(s)
Liked: 2578
Drop the tuning, you have a decent hump there. you can get away with a lower tune with that enclosure.
notnyt is offline  
post #8 of 14 Old 08-17-2017, 12:08 PM
AVS Forum Special Member
 
Samps's Avatar
 
Join Date: Feb 2014
Location: Pittsburgh, PA
Posts: 2,156
Mentioned: 30 Post(s)
Tagged: 0 Thread(s)
Quoted: 939 Post(s)
Liked: 529
Better, but the outside panel of the port is weak. Use two port dividers. The port size will shrink a bit but it will be stronger.
Samps is offline  
post #9 of 14 Old 08-17-2017, 03:13 PM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
I did what you said and the slightly reduced port length also meant I could shorten the port just enough to get rid of the second port piece. So the number of components actually dropped. I attached the new picture and hornresp stuff
Attached Thumbnails
Click image for larger version

Name:	CAD final bracing.png
Views:	46
Size:	1.41 MB
ID:	2269234   Click image for larger version

Name:	hornresp inputs.png
Views:	37
Size:	585.8 KB
ID:	2269236   Click image for larger version

Name:	hornresp out.png
Views:	47
Size:	187.9 KB
ID:	2269240  
BIGlep is offline  
post #10 of 14 Old 08-17-2017, 05:23 PM
AVS Forum Addicted Member
 
LTD02's Avatar
 
Join Date: Oct 2003
Posts: 20,553
Mentioned: 499 Post(s)
Tagged: 1 Thread(s)
Quoted: 2553 Post(s)
Liked: 2888
overall your plan seems fine and everything checks out. tuning may come in a hz lower or so.

Listen. It's All Good.
LTD02 is offline  
post #11 of 14 Old 08-17-2017, 05:35 PM
AVS Forum Special Member
 
notnyt's Avatar
 
Join Date: Dec 2008
Location: Long Island, NY
Posts: 8,782
Mentioned: 217 Post(s)
Tagged: 0 Thread(s)
Quoted: 2791 Post(s)
Liked: 2578
notnyt is offline  
post #12 of 14 Old 08-17-2017, 05:44 PM
AVS Forum Special Member
 
chrapladm's Avatar
 
Join Date: Mar 2010
Location: Adelaide, South Australia
Posts: 4,483
Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 945 Post(s)
Liked: 352
I would second the option of lowering the tuning. Or you can make the cabinet smaller and stay with the current tune.
chrapladm is offline  
post #13 of 14 Old 08-17-2017, 08:03 PM - Thread Starter
Newbie
 
Join Date: Aug 2016
Posts: 8
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 0
I might change the port back to an "L" to lower the tuning but as it is in terms of construction it should be really easy to build and is smaller than a lot of dual 18 bins. This driver seems to always have a tuning hump.
BIGlep is offline  
post #14 of 14 Old 08-19-2017, 12:29 AM
AVS Forum Special Member
 
chrapladm's Avatar
 
Join Date: Mar 2010
Location: Adelaide, South Australia
Posts: 4,483
Mentioned: 26 Post(s)
Tagged: 0 Thread(s)
Quoted: 945 Post(s)
Liked: 352
It may have a small hump but in your case you have a lot more volume than is needed for this high of a tune. Hence the large hump/spike. 200L looks good with a 22hz tune.
chrapladm is offline  
Sponsored Links
Advertisement
 
Reply DIY Speakers and Subs

Tags
21SW152 , ported , subwoofer

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