I need an Education...please

vintage52 · May 12th, 2008, 04:07 AM

Hi all

Could someone explain why a PA cabinet (it has a 12" and a 10" in it) is lined inside with a fabric resembling a lightweight carpet?

What's it for? What happens if I remove it?

Regards

Vintage52

garytelecastor · May 12th, 2008, 04:10 AM

I am just guessing here, because I am not a engineer, but I think the point of it is to absorb sound and add to the acoustic quality of the spkr cab. IMHO

vintage52 · May 12th, 2008, 05:52 PM

Thanks GaryT

Scott S · May 12th, 2008, 08:20 PM

The fiberglass breaks up the standing waves inside the cabinet, which keeps the buzz down and makes it act like a larger speaker cab.

vintage52 · May 12th, 2008, 11:07 PM

Thanks Scott

Teletale · May 13th, 2008, 01:05 AM

tt

vintage52 · May 13th, 2008, 01:36 AM

Quote:

Originally Posted by Teletale

The cab has a natural resonance... (a product of the dimensions and material by which it is constructed) a bit like a nice wine glass but not so nice. Play or sing a note equal-to, divisible-by, or divided-by that frequency and you get a standing wave a note perpetuated and aggravated by the fundamental.

The material is there not to add-to or enhance acoustic response but to kill it. so that you hear the voice/string/speaker... not the cab.
-TT

Does that mean that the average PA cab is not that acoustically nice - just there to pump out the sound running through it?

garytelecastor · May 13th, 2008, 01:59 AM

In sound reproduction the frequencies that are reproduced by the speakers do not just exit and move through the front. They are ubiquitous and they move in all directions. A source of "insulation" is added to the cabinet to help absorb these frequencies and help to deaden their effect on the cab and back bleed.
Try to think of the cabinet as ONE piece. It is not simply a conglomeration of separate components, really good designers try to design the cab to be spkr and cab as one unit and one instrument. But they really do want the majority of the reproduction coming out the front of the cab.
If you have ever had the chance to hear a system that is tri-amped, and you go up to the bass bins you will find that they are much less friendly to this than say the horns or the mids. The bass frequencies tend to lay along the floor and they are pervasive in nature. The horns or highs will be very unidirectional and tend to be very friendly to being pushed out the front of the cab. This all has to do with the physics of the wave and their speed of vibration, etc.
So the PA is really not just a "box" so to speak. It actually could be classified as another instrument.

Teletale · May 13th, 2008, 05:34 PM

tt

vintage52 · May 13th, 2008, 06:30 PM

A wealth of knowledge here. Appreciate you all taking the time to reply. Cheers

May 12th, 2008, 04:07 AM	#1 (permalink)
vintage52 Tele-Meister Join Date: May 2003 Location: Wellington, New Zealand Age: 40 Posts: 323	I need an Education...please Hi all Could someone explain why a PA cabinet (it has a 12" and a 10" in it) is lined inside with a fabric resembling a lightweight carpet? What's it for? What happens if I remove it? Regards Vintage52

May 12th, 2008, 04:10 AM	#2 (permalink)
garytelecastor Friend of Leo's Join Date: Sep 2006 Location: Minnesota Posts: 3,881 18 Photos	I am just guessing here, because I am not a engineer, but I think the point of it is to absorb sound and add to the acoustic quality of the spkr cab. IMHO __________________ éí 'aaníígÓÓ 'áhoot'é Would you mind holding this bag while we go through the custom shop????? Redd Volkaert is a Jedi Knight at one with the Force!!!

May 13th, 2008, 01:05 AM	#6 (permalink)
Teletale Voluntarily Removed Tele-Meister Join Date: Jan 2007 Location: USA Posts: 144	tt Last edited by Teletale; July 29th, 2008 at 12:53 AM.

May 13th, 2008, 01:59 AM	#8 (permalink)
garytelecastor Friend of Leo's Join Date: Sep 2006 Location: Minnesota Posts: 3,881 18 Photos	In sound reproduction the frequencies that are reproduced by the speakers do not just exit and move through the front. They are ubiquitous and they move in all directions. A source of "insulation" is added to the cabinet to help absorb these frequencies and help to deaden their effect on the cab and back bleed. Try to think of the cabinet as ONE piece. It is not simply a conglomeration of separate components, really good designers try to design the cab to be spkr and cab as one unit and one instrument. But they really do want the majority of the reproduction coming out the front of the cab. If you have ever had the chance to hear a system that is tri-amped, and you go up to the bass bins you will find that they are much less friendly to this than say the horns or the mids. The bass frequencies tend to lay along the floor and they are pervasive in nature. The horns or highs will be very unidirectional and tend to be very friendly to being pushed out the front of the cab. This all has to do with the physics of the wave and their speed of vibration, etc. So the PA is really not just a "box" so to speak. It actually could be classified as another instrument. __________________ éí 'aaníígÓÓ 'áhoot'é Would you mind holding this bag while we go through the custom shop????? Redd Volkaert is a Jedi Knight at one with the Force!!!

May 13th, 2008, 05:34 PM	#9 (permalink)
Teletale Voluntarily Removed Tele-Meister Join Date: Jan 2007 Location: USA Posts: 144	tt Last edited by Teletale; July 29th, 2008 at 12:52 AM.

May 12th, 2008, 05:52 PM	#3 (permalink)
vintage52 Tele-Meister Join Date: May 2003 Location: Wellington, New Zealand Age: 40 Posts: 323	Thanks GaryT

May 12th, 2008, 08:20 PM	#4 (permalink)
Scott S Tele-Afflicted Join Date: Dec 2005 Location: SW CR IA US NA PE Age: 28 Posts: 1,922	The fiberglass breaks up the standing waves inside the cabinet, which keeps the buzz down and makes it act like a larger speaker cab.

May 12th, 2008, 11:07 PM	#5 (permalink)
vintage52 Tele-Meister Join Date: May 2003 Location: Wellington, New Zealand Age: 40 Posts: 323	Thanks Scott

May 13th, 2008, 06:30 PM	#10 (permalink)
vintage52 Tele-Meister Join Date: May 2003 Location: Wellington, New Zealand Age: 40 Posts: 323	A wealth of knowledge here. Appreciate you all taking the time to reply. Cheers