What's Best for Lining Internal Subwoofer Walls? - Page 2 - AVS Forum
Forum Jump: 
Reply
 
Thread Tools
post #31 of 44 Old 10-11-2012, 12:52 PM
AVS Special Member
 
mjaudio's Avatar
 
Join Date: Nov 2002
Posts: 2,459
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 30
The reason to keep the covers on the pillows is the keep the polyfill from getting everywhere, especially around the driver. Because of that I normally just arrange them in there but do not staple or glue them which is normally not needed in a home environment were you hardly move the sub around. You want them in there snug but you don't want to compress them much and leave some space behind the subs vent.
saginawjuggalo likes this.

"Half the world is looking for Jesus, and the other half is looking for more bass..."
mjaudio is offline  
Sponsored Links
Advertisement
 
post #32 of 44 Old 10-11-2012, 12:54 PM
AVS Special Member
 
mastermaybe's Avatar
 
Join Date: Sep 2007
Posts: 7,114
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 22 Post(s)
Liked: 145
good deal, gracias.

James

Actual phone call (see pic to left):

 

Tech (responding to laughter): "I'm sorry sir, did I miss something?"

Me: "Yeah, a case of Diet Mountain Dew walking across my living room."

mastermaybe is online now  
post #33 of 44 Old 10-11-2012, 09:04 PM
AVS Special Member
 
Stereodude's Avatar
 
Join Date: Jan 2002
Location: Detroit Metro Area
Posts: 9,601
Mentioned: 2 Post(s)
Tagged: 0 Thread(s)
Quoted: 289 Post(s)
Liked: 377
Quote:
Originally Posted by mastermaybe View Post

does filling a subwoofer cabinet adversely/significantly affect internal volume.
Sound waves travel slower through the polyfill so it has the net effect of making the box seem bigger rather than taking away from the internal volume. The right amount of polyfill depends on the type of box and the box size. Sealed boxes continue to show gains from increased polyfill density well after the point increased polyfill becomes detrimental in a ported box.

In a small ~1.4ft^3 ported box of mine I found a relatively light amount of poly fill of ~8oz per ft^3 was the right amount. Additional polyfill did not lower the tuning point any more, but instead began to reduce the output of the port and the driver on the knee of the frequency response curve.

In a small ~1.4ft^3 sealed box up to 24oz per ft^3 was still showing gains though they were getting pretty small as I crammed in more and more polyfill.

Keep in mind this was loose polyfill, not a pillow.
Stereodude is online now  
post #34 of 44 Old 10-12-2012, 04:18 AM
AVS Special Member
 
NicksHitachi's Avatar
 
Join Date: Jul 2007
Location: Wilmington, NC
Posts: 3,444
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Liked: 90
Since the speed of sound is constant in air and doesnt speed up or slow down, the lining/stuffing produces gas/particle friction converting some of that energy into heat. The sound wave continues on at same speed but with less "pressure."

Don't waste time reading signatures.....
NicksHitachi is online now  
post #35 of 44 Old 10-12-2012, 05:36 AM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,211
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1173
Quote:
Originally Posted by Stereodude View Post

Sound waves travel slower through the polyfill so it has the net effect of making the box seem bigger rather than taking away from the internal volume.
The reduction in the speed of sound is cursory at best, and it does not make the box seem bigger. The higher coefficient of resistivity of damping materials, as compared to air, causes a lowering of the system Q, which in some ways emulates a larger box, but it does not duplicate it.
Quote:
the lining/stuffing produces gas/particle friction converting some of that energy into heat.
Said heat is a by-product of the Q lowering action, not the cause for the lowering of Q. It all boils down to system impedance, which changes with damping, and can be seen on impedance sweeps.
MemX likes this.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is offline  
post #36 of 44 Old 11-30-2013, 02:56 PM
AVS Special Member
 
mtbdudex's Avatar
 
Join Date: May 2007
Location: SE Michigan
Posts: 4,127
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 161
I'm building a 4 cu ft ported subwoofer, here is my Q2 from that thread post #5
http://www.avsforum.com/t/1502689/flat-pack-4-cu-ft-12-ultimax-sub-ported-box-build#post_24014680
Quote:
Q2: stuffing inside ported box. I want to just line the box with stuffing, right?
I seem to remember reading that somewhere here but can't find it just now.

I did a search, came across this thread, and for a cliff notes summary:
a) do I line the internal subwoofer walls with - open cell foam or OC703 (I have a lot of extra OC703) or ??
or
b) stuff the box with some polyfill
or
c) need to measure to truly know what to do

Based on best practices, what is consensus?
mtbdudex is offline  
post #37 of 44 Old 11-30-2013, 03:09 PM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,211
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1173
Quote:
Originally Posted by mtbdudex View Post

I'm building a 4 cu ft ported subwoofer...
a) do I line the internal subwoofer walls with - open cell foam or OC703 (I have a lot of extra OC703) or ??
or
b) stuff the box with some polyfill
or
c) need to measure to truly know what to do
Based on best practices, what is consensus?
With a ported sub you're primarily trying to damp internal midrange reflections that otherwise might reflect out the ports or reflect back to the cone. Midrange? Yes, their source being above-bandwidth content not filtered out by the crossover, and harmonics of in-bandwidth content created by the driver. A couple of inches of any of the usual materials will do. Type 700 has the advantage that it takes less of it to give the same result. You can use stuffing to lower the Q of a ported enclosure, but that's better accomplished via the duct length, and if you do so with stuffing there's a loss of low end sensitivity.
steve nn and mtbdudex like this.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is offline  
post #38 of 44 Old 12-01-2013, 09:58 PM
AVS Addicted Member
 
noah katz's Avatar
 
Join Date: Apr 1999
Location: Mountain View, CA USA
Posts: 20,278
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 29 Post(s)
Liked: 125
Quote:
Originally Posted by Bill Fitzmaurice View Post

You can use stuffing to lower the Q of a ported enclosure, but that's better accomplished via the duct length....

Port length primarily affects fB, no?

Effect on Q would depend on surface area to cross sectional area ratio due to configuration, i.e. round, slot, etc.

And said Q varies with drive level/port velocity.

Noah
noah katz is offline  
post #39 of 44 Old 12-07-2013, 05:07 PM
AVS Special Member
 
mtbdudex's Avatar
 
Join Date: May 2007
Location: SE Michigan
Posts: 4,127
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 161
Quote:
Originally Posted by Bill Fitzmaurice View Post

Quote:
Originally Posted by mtbdudex View Post

I'm building a 4 cu ft ported subwoofer...
a) do I line the internal subwoofer walls with - open cell foam or OC703 (I have a lot of extra OC703) or ??
or
b) stuff the box with some polyfill
or
c) need to measure to truly know what to do
Based on best practices, what is consensus?
With a ported sub you're primarily trying to damp internal midrange reflections that otherwise might reflect out the ports or reflect back to the cone. Midrange? Yes, their source being above-bandwidth content not filtered out by the crossover, and harmonics of in-bandwidth content created by the driver. A couple of inches of any of the usual materials will do. Type 700 has the advantage that it takes less of it to give the same result. You can use stuffing to lower the Q of a ported enclosure, but that's better accomplished via the duct length, and if you do so with stuffing there's a loss of low end sensitivity.

Thx Bill;

I've got two types of leftover material, lots of 2" thick OC703 and also 2" thick blended cotton and recycled paper based.
http://www.acoustimac.com/ecoinsul422/
spare%2520acoustic%2520material%25201.JPG . spare%2520acoustic%2520material%25202.JPG

I need to put the wall lined material before I put the top on, so just attach that on all the walls? ie all 6 sides?
I can use some adhesive glue.
I read it's best to have the back of the port un obstructed by the diameter of the port, so I will not have material directly reward of the ports.
Port%2520clearance%2520-%2520material.JPG . Port%2520clearance%2520-%2520material%2520top%2520detail.JPG
mtbdudex is offline  
post #40 of 44 Old 12-07-2013, 07:43 PM
AVS Special Member
 
Bill Fitzmaurice's Avatar
 
Join Date: Nov 2009
Location: New Hampshire
Posts: 9,211
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 1 Post(s)
Liked: 1173
Quote:
Originally Posted by mtbdudex View Post

I've got two types of leftover material, lots of 2" thick OC703 and also 2" thick blended cotton and recycled paper based.
Either should work OK, all five sides is best, you don't need to do the baffle.

Bill Fitzmaurice Loudspeaker Design

The Laws of Physics aren't swayed by opinion.
Bill Fitzmaurice is offline  
post #41 of 44 Old 12-08-2013, 07:08 PM
AVS Special Member
 
NicksHitachi's Avatar
 
Join Date: Jul 2007
Location: Wilmington, NC
Posts: 3,444
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Liked: 90
I used 2" OC703 in one of my sub builds and fastened with construction adhesive and green button roofing tacks...

Worked good. :-)

Don't waste time reading signatures.....
NicksHitachi is online now  
post #42 of 44 Old 12-13-2013, 03:26 AM
AVS Special Member
 
mtbdudex's Avatar
 
Join Date: May 2007
Location: SE Michigan
Posts: 4,127
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 161
I ended up using the 2" thick blended cotton and recycled paper based, as I had lot's of that stacked up in leftover triangle shapes.

cut pieces to fit, glue on back ........................................lining "done", top lining will be done after top is glued on
sub%2520lining-1.JPG . sub%2520lining-3.JPG
mtbdudex is offline  
post #43 of 44 Old 12-13-2013, 04:23 AM
AVS Special Member
 
NicksHitachi's Avatar
 
Join Date: Jul 2007
Location: Wilmington, NC
Posts: 3,444
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 23 Post(s)
Liked: 90
I spy a DIYSG ported 12 flatpack..... ;-)

What driver you using?

Don't waste time reading signatures.....
NicksHitachi is online now  
post #44 of 44 Old 12-13-2013, 05:10 AM
AVS Special Member
 
mtbdudex's Avatar
 
Join Date: May 2007
Location: SE Michigan
Posts: 4,127
Mentioned: 0 Post(s)
Tagged: 0 Thread(s)
Quoted: 9 Post(s)
Liked: 161
12" Dayton Ultimax driver, amp is iNuke3000 DSP, got the 3000 for future 2nd sub.
mtbdudex is offline  
Reply DIY Speakers and Subs

User Tag List

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