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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => LAB Subwoofer Forum => Topic started by: Andrew Watts on November 15, 2019, 08:06:51 am

Title: Insulation for sub cabinets
Post by: Andrew Watts on November 15, 2019, 08:06:51 am
For those builders out there, what do you use for internal cabinet lining?
Title: Re: Insulation for sub cabinets
Post by: Scott Holtzman on November 15, 2019, 12:47:53 pm
For those builders out there, what do you use for internal cabinet lining?

A really nice tweed this time of year.
Title: Re: Insulation for sub cabinets
Post by: Art Welter on November 15, 2019, 01:51:47 pm
For those builders out there, what do you use for internal cabinet lining?
Generally, no insulation is used for ported sub cabinets, as it reduces output level.
"Full range" ported cabinets use insulation to reduce reflected upper out of phase frequencies output from the ports.
Sealed cabinets often use polyfill, though it requires more fill than fiberglass to achieve the same results. Fiberglass has fallen out of favor for health and "itch" reasons, though if properly secured, works quite well with no shedding.

Denim and hemp are also used (and tweed  ;) ) but being organic materials, can easily support mold growth so are generally not used for cabinets subject to moisture.
Title: Re: Insulation for sub cabinets
Post by: Andrew Watts on November 15, 2019, 07:08:18 pm
Generally, no insulation is used for ported sub cabinets, as it reduces output level.
"Full range" ported cabinets use insulation to reduce reflected upper out of phase frequencies output from the ports.
Sealed cabinets often use polyfill, though it requires more fill than fiberglass to achieve the same results. Fiberglass has fallen out of favor for health and "itch" reasons, though if properly secured, works quite well with no shedding.

Denim and hemp are also used (and tweed  ;) ) but being organic materials, can easily support mold growth so are generally not used for cabinets subject to moisture.

I had not heard that ported subs don't need insulation.  Most of the cabs I've had over the years have had some form.
Title: Re: Insulation for sub cabinets
Post by: Jim McKeveny on September 04, 2020, 10:10:06 am
I had not heard that ported subs don't need insulation.  Most of the cabs I've had over the years have had some form.

Operating at theoretical optimum a sub cabinet should not need filler. However, tolerances in driver parameters (production and over lifespan), tolerances in cabinet build, and the operating gradients of elevation, temp, and humidity, lead most manufacturers  to broaden the cabinet tuning peak with an amount of fill.
Title: Re: Insulation for sub cabinets
Post by: Steve Litscher on September 13, 2020, 03:03:32 pm
I've helped build hundreds of cabinets over the past few years for JTR, and he typically uses denim/cotton insulation, poly fill, and RockWool insulation. They each have their advantages and disadvantages. The RockWool is easy to cut, for example, but it sheds rather easily, so it's best suited for a sealed cabinet.

From what I've been able to research/find online, hemp insulation is highly mold resistant but does absorb water, so it may not be desirable. Although I'd argue that if your subs are absorbing that much water/moisture, there's likely going to be other issues to contend with.
Title: Re: Insulation for sub cabinets
Post by: Art Welter on September 14, 2020, 09:21:37 am
I've helped build hundreds of cabinets over the past few years for JTR, and he typically uses denim/cotton insulation, poly fill, and RockWool insulation.
Steve,

On the JTR subwoofers, the Captivator series, or Orbit Shifter, what (if any) insulation type, and what percentage fill is used?

Art
Title: Re: Insulation for sub cabinets
Post by: Steve Litscher on September 14, 2020, 10:52:37 am
Steve,

On the JTR subwoofers, the Captivator series, or Orbit Shifter, what (if any) insulation type, and what percentage fill is used?

Art

Yes to all of the above, and it really varies by each speaker. Typically though, there's some insulation on every major flat internal surface, glued and stapled.
Title: Re: Insulation for sub cabinets
Post by: Ivan Beaver on September 14, 2020, 11:30:13 am
When you start to think of the size of the wavelengths involved, vs the thickness of any insulation, you should quickly realize that that insulation does not do any good at the freq the cabinet will be operating at.

For higher freq, yes, it makes a difference, as Art said, for reducing the reflections from the walls of the cabinet through the ports and speaker cone and causing cancellations due to combfiltering.

Think of sound in terms of a size of the wavelength and dB, and then everything starts to change, at least as far as "does it make a difference".