Latest opinion on using pink insulation for 2x15s?

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phmosele

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Joined 2012
#1
Hi everyone

I have posted asking for advice on a 2x15 ported box of about 600 watts and about 36x24x18 external size covering about 50-150Hz range. I was wondering what the consensus was on using regular ole Home Depot pink insulation in something like this please?

How much (if any) should I use please? A few inches of thickness tacked to the walls? A loose fill of 9-inch thick batts maybe? What should I do about the keeping the port area unobstructed? Enquiring minds need to know!🙂

This is probably a less serious question, but I was also thinking about standing waves. I would imagine they can be a real problem when the power cranks up, but I suppose the pressures inside the box are what makes air come out of the ports. Physics and acoustics were never my strong suit. But it ocurred to me that one way to break up standing waves would be to fasten randomly angled surfaces inside. That would bounce the air around the box no doubt; it could also make things sound dreadful. I don't know if JBL and EAW fix randomly angled surfaces inside their 2000-watt boxes. I suspect not. But what if they ain't as smart as me?

Thanks very much
Phil
 
#2
Looking at the constructions ( assemblies ) of various boxes I see many reinforcing panels
with holes that keep the walls of the box from vibrating; I think that those panels inside
( something also called matrix, from B&W) keep from standing waves also.
They are used mostly in tower style enclosures, that's why I say this.
Usually the boxes for frequencies under 100 Hz, subwoofer range, don't need any filling/stuffing because they aren't seen by the waves, the box itself is so little respect to the lenght of the waves involved. Going upper in frequency....150 Hz is already mid-bass...well,just keep the panels firm !
 
#3
Hi
Thanks for your reply.
It would seem from your reply that I would not have a problem if this were a sub box of, say, under 100Hz, but are you suggesting the frequencies from 100 to 150Hz could be problematic requiring some Pink treatment please?

I am crossing over into a pair of Celestion-loaded EV 3-ways on poles, and I didn't really see the point of asking them to bang harder at a lower crossover point than around 150 if they are going to be 6 feet off the floor.

I was going to give the 2x15 more bracing, but you think I should still use some Pink for the area betweeen 100 - 150Hz please?
Thanks
Phil
 
#5
mid-bass resonance

turbodawg said:
I'm building a pair of portable PA subs right now, I will not be stuffing them as I want maximum output from the port. If there is a HF resonance I will notch EQ it out.
Click to expand...

Hi
I am assuming your "subs" to be in the region 30-sub-100Hz? I use the term "bass boxes" for mine as I want them to cover no lower than 50Hz and because of the nature of the setup with the mids and my application, I don't really see that I gain anything by not crossing over until into the mid-bass at around 250.
What you said about resonance and eq interests me because I'd thought that "resonance" was a property of poorly braced walls while the Pink was to do with absorbing standing waves. Of course, everything has a natural resonant frequency, but I was wondering a couple of things:

What do you hear when resonant frequencies are present? It probably isn't hard to notch them out given the limited number of sliders that cover the bandwidth once you identify you have a problem.

As I will be using these well above subs frequencies, should I put in any Pink? I don't want to obstruct the ports, so I guess I would be limited to tacking a few inches to the back and sides only. But I don't want to do what I don't have to do, of course.
Thanks for your interest
Phil
 
#6
phmosele said:
Hi
I am assuming your "subs" to be in the region 30-sub-100Hz? I use the term "bass boxes" for mine as I want them to cover no lower than 50Hz and because of the nature of the setup with the mids and my application, I don't really see that I gain anything by not crossing over until into the mid-bass at around 250.
What you said about resonance and eq interests me because I'd thought that "resonance" was a property of poorly braced walls while the Pink was to do with absorbing standing waves. Of course, everything has a natural resonant frequency, but I was wondering a couple of things:

What do you hear when resonant frequencies are present? It probably isn't hard to notch them out given the limited number of sliders that cover the bandwidth once you identify you have a problem.

As I will be using these well above subs frequencies, should I put in any Pink? I don't want to obstruct the ports, so I guess I would be limited to tacking a few inches to the back and sides only. But I don't want to do what I don't have to do, of course.
Thanks for your interest
Phil
Click to expand...

I'm using the term correctly in refering to the air resonating in the cab producing a response peak.

My "bass bins" will be crossed over with an f3 around 120-150 hz with a corresponding cut in the mains. Since I am not stuffing I might have a response peak(s) in the midbass which I will EQ out.

The design is well braced and will be internally coated with damping material, and should have minimal panel resonances.

Sure, there will be some higher frequency sound coming from the port, delayed and out of phase, but I feel that the tradeoff with more low frequency port output is preferable. I may try just a small amount of stuffing though.

My tops will be doing very little bass and will get lots of stuffing.
 
#9
DigitalJunkie said:
I'd probably start with a lining of it on the interior walls of the cabinet,and see how that works. It should help tame some internal reflections in the box,etc.

Then if ya like,try it with the box lightly stuffed. It's not hard to remove if you don't like it. (Assuming you can still remove the driver to gain access inside)
Click to expand...

Yes, I'll still have access inside
Thanks
Phil
 
#12
Stay off "pink" - unless you like wearing a mask and gloves while using it or fixing the gear. Don't stuff the box if you want the port to do what it is spec'd to do with your simulation. At anything above 100Hz or so, I'd want substantial absorption on the walls to absorb as much internal reflected energy as possible, if you want maximum sonic wonderfulness.

There are a variety of materials that are low cost and are nicely absorptive at the frequencies of interest, and they don't make you itch or mess with your lungs...

_-_-bear
 
#13
bear said:
Stay off "pink" - unless you like wearing a mask and gloves while using it or fixing the gear. Don't stuff the box if you want the port to do what it is spec'd to do with your simulation. At anything above 100Hz or so, I'd want substantial absorption on the walls to absorb as much internal reflected energy as possible, if you want maximum sonic wonderfulness.

There are a variety of materials that are low cost and are nicely absorptive at the frequencies of interest, and they don't make you itch or mess with your lungs...

_-_-bear
Click to expand...


I did some reading on this, regular fiberglass is definitely a bad idea in a ported speaker....lol.
 
#14
bear said:
Stay off "pink" - unless you like wearing a mask and gloves while using it or fixing the gear. Don't stuff the box if you want the port to do what it is spec'd to do with your simulation. At anything above 100Hz or so, I'd want substantial absorption on the walls to absorb as much internal reflected energy as possible, if you want maximum sonic wonderfulness.

There are a variety of materials that are low cost and are nicely absorptive at the frequencies of interest, and they don't make you itch or mess with your lungs...
Click to expand...

I was going to go with a coating of the roofing tar at least. But I would like to take these 2x15s fairly high into the midrange. They aren't serious subs and were never meant to be, and from the various different threads I've started it seems that opinion is that I can take them as high as I care to, except that more and more mid frequencies will start coming out of the ports, and not in a good way. Of course, I have used commercial full-range 2x15s that go all the way up until a horn kicks in around 3K, and I haven't necessarily heard nasty stuff coming out of their ports.

You can weigh in with at what frequency the ports become problematic if you care to. But let's just say 500Hz... and even that is arbitrary. What sort of materials would be better than reg'lar Pink at the higher frequencies please? Don't include Dynamat or Acoustastuf (it's to expensive).
I don't really have a problem handling Pink (or yellow) if that works.
Thanks
Phil
 
#15
consider any matted material that is not hard.

a cocoa fiber door mat would actually be good at mid and high freqs... but they shed and are not so cheap.

now you have a clue or two... commonly available materials are quite available and suitable, IF you know how to use them... 😀

_-_-bear
 
#19
Since giving up on using pink fibreglass insulation on the grounds that it is bad for peoples health, and also can damage a speaker voice coil as the glass fibre is abrasive. I now use polyester fibre as used inside bedding duvets. This is maybe not quite as effective but certainly dampens out upper frequency resonances.
 
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