Cabinet damping material needed in Mumbai

[Kevano]

Cabinet damping material in Mumbai

Where can I get 8-10mm felt and 30mm polyester foam for cabinet damping. Going down the route suggested by Troels Gravesen - http://www.troelsgravesen.dk/cabinet-damping.htm

 

[sadik]

Cabinet damping material in Mumbai

Where can I get 8-10mm felt and 30mm polyester foam for cabinet damping. Going down the route suggested by Troels Gravesen - http://www.troelsgravesen.dk/cabinet-damping.htm

Dont know in Mumbai.. I was lucky to find the Felt locally

 

[Kevano]

Dont know in Mumbai.. I was lucky to find the Felt locally

Thanks Sadik. Hope some Mumbai FM is able to help.

 

[Hiten]

For most industrial, semi industrial, hardware stuff search ' Indiamart '.
Regards

 

[narcissus]

Thanks Sadik. Hope some Mumbai FM is able to help.

You'll get it on The street opposite JJ hospital.

 

[Kevano]

What is the ideal GSM of the felt for a sealed enclosure of internal dimensions - 214mm x 82mm x 132mm. Driver - Full range Faital Pro 3fe25 ?

 

[Sean de Silva]

You can also use polyfill as damping material for a speaker cabinet.

 

[Satyaki Banerjee]

Kamruddin Adamjee & Co​

135, Ebrahim, Ibrahim Rehmatullah Rd, Bhendi Bazaar, Mumbai, Maharashtra 400003

For all my speaker projects I have sourced felt from this shop in Mumbai. I have used felt of 12 - 18 mm thickness. I can post the GSM value over the weekend after digging through my notes.

 

[Kevano]

For all my speaker projects I have sourced felt from this shop in Mumbai. I have used felt of 12 - 18 mm thickness. I can post the GSM value over the weekend after digging through my notes.

Thanks Satyaki. Will await your reply.

I was under the impression that 8-10mm thickness is the std. But apart from the GSM of the felt how should one go about choosing the thickness?

So for a sealed enclosure of internal dimensions - 214mm x 82mm x 132mm with a single FR driver crossed at 250Hz what is the math for choosing the thickness and GSM of the felt?

 

[Satyaki Banerjee]

How to Use Sound-Damping Materials in DIY Loudspeakers

Article How Use Sound Damping Materials for Loudspeakers, with Sheeps Wool, Woollen Fibre Felts, BAF Wadding and Bitumastic Sheet. Shop QTA Systems

www.qtasystems.co.uk

You might find this article interesting.

 

[Hiten]

I was under the impression that 8-10mm thickness is the std. But apart from the GSM of the felt how should one go about choosing the thickness?

So for a sealed enclosure of internal dimensions - 214mm x 82mm x 132mm with a single FR driver crossed at 250Hz what is the math for choosing the thickness and GSM of the felt?

I guess it will require simulation software and measurements. Are you following any specific speaker design ?

 

[keith_correa]

So for a sealed enclosure of internal dimensions - 214mm x 82mm x 132mm with a single FR driver crossed at 250Hz what is the math for choosing the thickness and GSM of the felt?

Sealed boxes are usually stuffed generously. What software did you use for modeling the box for this driver? Didn't it have options to select/tune stuffing?

 

[Satyaki Banerjee]

An important consideration for sealed enclosure design is the Total Q of the speaker system that you are intending to achieve.

• Qtc of 0.5 : would give you superb transient response, a smooth roll off but low efficiency (over damped)
• Qtc of 0.707 : is generally a good target to keep, very good transients and relatively flat response and smooth cutoff
• Qtc higher than .707 would start affecting transient response

• Qtc = Qts * (Vas / Vc + 1)1/2
• Vc = Vas / [(Qtc / Qts)2 -1]
• fc = fs * (Vas / Vc +1)1/2
• f3 = { { (1/Qtc2 -2) + [(1/Qtc2 -2)2 + 4]1/2 } /2 }1/2 * fc

The felt lining is going to reduce the reflected waves generated by the back of the driver cone. You can consider lining the back wall of the enclosure with 12 mm felt of the lowest GSM you are able to get. You can use 10 mm for the side walls.

 

[Kevano]

What software did you use for modeling the box for this driver? Didn't it have an option to select/tune stuffing?

I used WinISD. I don't think this one has the stuffing option unless I've missed it. Could you recommend me the software that has this option please.

Are you following any specific speaker design ?

No, I'm not. Just building a sealed box with golden ratio internal dimension. I'm down sizing the box to 2.3lt with Qtc of 0.8+. The Fsc is 141 Hz and a HP of 250 Hz will be applied on the AVR. Choose to downsize the box because I'm crossing it with the sub at 250Hz and don't need the low end on the FR driver.

An important consideration for sealed enclosure design is the Total Q of the speaker system that you are intending to achieve.

• Qtc of 0.5 : would give you superb transient response, a smooth roll off but low efficiency (over damped)
• Qtc of 0.707 : is generally a good target to keep, very good transients and relatively flat response and smooth cutoff
• Qtc higher than .707 would start affecting transient response

I'm down sizing the box to 2.3lt with Qtc of 0.8+(WinISd calculated 11lt for Qtc of 0.7). The Fsc is 141 Hz and a HP of 250 Hz will be applied on the AVR. This driver comes in 4,8 and 16 ohm. I choose the 8 ohm to match it with the default 8 ohm impedance of the AVR.

But I've now realised the 4 ohm gives a box size of 1.8lt with Qtc of 0.7.

What is the better option, my current downsized box with 8ohm driver connected AVR with the default 8 ohm or a correct sized box connected to AVR with impedance option set to 4 ohms.

 

[Satyaki Banerjee]

Rule of thumb : 450 GM's of polyfill / cu ft will increase the effective volume of the enclosure by 25%. Compensate the volume depending on the amount of stuffing you intend to use to achieve the desired Qtc. It is fairly straightforward calculation. Thereafter you have to experiment and fine tune the speakers by extended listening.

I'm down sizing the box to 2.3lt with Qtc of 0.8+(WinISd calculated 11lt for Qtc of 0.7). The Fsc is 141 Hz and a HP of 250 Hz will be applied on the AVR. This driver comes in 4,8 and 16 ohm. I choose the 8 ohm to match it with the default 8 ohm impedance of the AVR.

But I've now realised the 4 ohm gives a box size of 1.8lt with Qtc of 0.7.

What is the better option, my current downsized box with 8ohm driver connected AVR with the default 8 ohm or a correct sized box connected to AVR with impedance option set to 4 ohms.

My personal choice in this case would be 8 ohms

 

[Kevano]

You can consider lining the back wall of the enclosure with 12 mm felt of the lowest GSM you are able to get. You can use 10 mm for the side walls.

I looked up indiamart. One dealer in Mumbai had wool felt from 50-1000GSM. Another had 1600 GSM mixed material felt 1600 upwards. The felt on Jansen that Troels Gravesen recommends is 1280GSM. Is there any rule of thumb for felt GSM for a sealed enclosure of 2.3lt?

Rule of thumb : 450 GM's of polyfill / cu ft will increase the effective volume of the enclosure by 25%. Compensate the volume depending on the amount of stuffing you intend to use to achieve the desired Qtc. It is fairly straightforward calculation. Thereafter you have to experiment and fine tune the speakers by extended listening.

So felt on the walls and stuff with polyfill, right?

 

[keith_correa]

I used WinISD. I don't think this one has the stuffing option unless I've missed it.

In WinISD: Box ->Advanced->Qa

And please read this too: https://drive.google.com/file/d/16j9rOXLL6uPSykyZ1OI9yk0QjQ-fZCXb/view?usp=drivesdk

 

[Satyaki Banerjee]

So felt on the walls and stuff with polyfill, right?

Yes.

 

[Kevano]

And please read this too: https://drive.google.com/file/d/16j9rOXLL6uPSykyZ1OI9yk0QjQ-fZCXb/view?usp=drivesdk

This is such an incredible article. Many many thanks Keith.

So for the benefit of everyone, the main take away from the article is that the acoustic energy dissipation ability of the humble Polyfill for all practical purposes is pretty much same as the more expensive counterparts like AcoustaStuff, Lambs wool, and recycled denim installation. This information is gold, at least for me.

 

[Chulbulee]

for DIY, a few decades earlier, anything cotton would work perfectly ... (even old, worn undergarments ).