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post #31 of 41 Old 09-29-2013, 04:09 PM
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Generally, no insulation materials are used to line a port.

As I mentioned, enlarging the port area is beneficial. Many modeling programs set the design parameters on 2-5% of the speed of sound as the max vent velocity-I just try and decrease this as much as
I can for the given limitations of the overall cabinet size.

That said, it gets hard if you're trying to design a sub with a cutoff down in the low 20's, as ports get larger(much larger sometimes to be practical) the lower you go.

Best regards,

John
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post #32 of 41 Old 09-29-2013, 07:03 PM
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Quote:
Originally Posted by sleeptab View Post

Another question. I've seen some people on YouTube do slot ports and they put insulation type material inside stapled down. Should I do this? It would change my tuning, so is it worth it

General Rule Of Thumb (ROT): "Line Ported, Stuff Sealed". You should line the walls of the enclosure (not the ports). A good material to use is convoluted foam, such as a cheap foam mattress from Wally World. Simply cut to size and hot glue, spray adhesive, staple, whatever to the interior walls. Don't worry about small areas near the drivers on the baffle. Bracing is the most important as mentioned. 1" hardwood dowels work well and can be inserted after the enclosure is built. Try to brace every 8"-10", x, y, and z planes where possible. I also try to "conjoin" the dowels where they intersect if practical, all using PL Premium.

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post #33 of 41 Old 09-30-2013, 09:06 AM
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Quote:
Originally Posted by zhillsguy View Post

General Rule Of Thumb (ROT): "Line Ported, Stuff Sealed". You should line the walls of the enclosure (not the ports). A good material to use is convoluted foam, such as a cheap foam mattress from Wally World. Simply cut to size and hot glue, spray adhesive, staple, whatever to the interior walls. Don't worry about small areas near the drivers on the baffle. Bracing is the most important as mentioned. 1" hardwood dowels work well and can be inserted after the enclosure is built. Try to brace every 8"-10", x, y, and z planes where possible. I also try to "conjoin" the dowels where they intersect if practical, all using PL Premium.


I will disagree with the foam claim. Fiberglass does a better job. Typically the reasons for lining a vented enclosure are to help tame reflected frequencies inside the cabinet. The same would apply to a sealed design too.

You start looking at stuffing cabinets when they are undersized-insulation causes the cabinet to appear larger at some point(when the density of the insulation goes over a certain point).

Now, fiberglass is a PITA to work with, no denying it. Lately I've been using the recycled cotton/blue jean insulation from these folks:

http://www.bondedlogic.com/acoustical-products/ultratouch-plus

Works nicely, and is not hazardous.

Best regards,

John
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post #34 of 41 Old 09-30-2013, 09:13 PM
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Originally Posted by servojohn View Post

I will disagree with the foam claim. Fiberglass does a better job.

There are many threads about this subject....do your own research and draw your own conclusions. I tend to believe the folks that have professional experience and have tested many configurations for a number of years. I read in one thread that BFM recommended flat foam over convoluted, that makes sense (more foam content for a given area), either way (generally) open cell foam will have the same effect as fiberglass for lining. I believe the jury will remain out on this one.

https://www.google.com/search?q=foam+line+a+ported+subwoofer+site:techtalk.parts-express.com&biw=1344&bih=656
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post #35 of 41 Old 10-01-2013, 03:03 AM
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yes, lining the cabinet with r19 or r25 fiberglass would be advised to keep internal resonances to a minimum. keep it away from the port.

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post #36 of 41 Old 10-01-2013, 04:39 AM
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yes, lining the cabinet with r19 or r25 fiberglass would be advised to keep internal resonances to a minimum. keep it away from the port.

I've used regular pink or yellow insulation many, many times with very good results and still use it. For those that do not enjoy working with fiberglass I would recommend Roxul AFB mineral wool for curved cabinets as I just used in a recent build or Roxul Rockboard for side flat panels. They are available at AtsAcoustics.com. It is more expensive than fiberglass but is a very good alternative.
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post #37 of 41 Old 10-01-2013, 05:44 AM
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You may use wall insulation fiberglass, it will work, but it does not work nearly as well as rigid Type 700 fiberglass boards. I won't use insulation fiberglass, as it will fall apart, which can lead to problems down the road. As for other materials, foam, polyfill, etc, all work equally well in the right proportion. The main advantage to Type 700 is its very high index of resistivity, which means less of it is required to achieve the same level of damping. There are instances where that might be significant, but for all practical purposes a couple of inches of any of the usual materials will accomplish the task at hand.

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post #38 of 41 Old 10-01-2013, 05:59 AM
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"You may use wall insulation fiberglass, it will work, but it does not work nearly as well as rigid Type 700 fiberglass boards."

?

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post #39 of 41 Old 10-01-2013, 06:41 AM
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Quote:
Originally Posted by LTD02 View Post

"You may use wall insulation fiberglass, it will work, but it does not work nearly as well as rigid Type 700 fiberglass boards."

?

I wonder if the 703 would work?? http://www.buyinsulationproductstore.com/servlet/the-520/1%22-Owens-Corning-703/Detail HD has something like this I think, or maybe it's just foam thinking about it.

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post #40 of 41 Old 10-01-2013, 10:00 AM
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Quote:
Originally Posted by steve nn View Post

I wonder if the 703 would work??
Sure. Type 700 refers to the stiff board construction, it's available in many thicknesses, 703 is one.

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post #41 of 41 Old 10-04-2013, 05:55 PM
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Quote:
Originally Posted by zhillsguy View Post

I tend to believe the folks that have professional experience and have tested many configurations for a number of years.


The 700 series fiberglass as Bill F. points out, is an industry standard for a reason.

There are some very high quality acoustic foams out there. I'm a long time fan of Soundcoat brand.

We used to use a few different varieties of foam in various places inside the Servodrive subwoofers.

However, when it came to the smaller sealed subwoofers like the Contabass, fiberglass was king.

I've been at this for a little while. ;>)

Best regards,

John
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