My GR SW-12-04 + A370PEQ Amp based Servo Sub Build

[naren2512]

Hi Friends,

I think most of know it that the GR research group reaped its fruits recently .. i,e we all got our kits some 10 days ago.. and it could all be possible mainly because of only one man.. Capt. Rajesh.. once again a Big Thank you to you on behalf of all the participant of the GR Group buy....

So I got my sub woofer kit (that contained two parts i.e Servo controlled sub SW-12-04 + Rythmic Servo Amp - A370PEQ ) and just started the sub build today as I have long week end

Since I am new to DIY thing and this being my first ( and probably last sub build ) I would request all the fellow members to guide me as much as you can, please give your inputs and suggestions also if you think i am going wrong anywhere then please pin point that and help me correct that step. I do not have any knowledge of how a good sub is built ( I have just learnt a little bit about what material to use etc with help of a few fellow members but still have some confusion around the same )

For the build I have bough below stuff so far :
1) Dennys GR servo sub kit - Cost $500 + shipping and customs
2) 19 MM ( it had 18mm written on it) Greenply 8*4 MDF sheet - costed Rs 1760
3) Fevicol SH - 2 Ltrs - cost Rs 320
4) GE Silicone Sealent - Rs 132
5) Need to find source for Bitumen sheets and Polly-fill / Glass wool

I have decided to build a Sealed cabinet with all the sides having double layer of mdf sandwitched together, the original standard sealed box plan suggested to double only the front and rear panels however I consulted Denny as well as our FM Flash and learnt that doubling rest of the panels make the enclosure even more sturdy and solid.. hence this decision. ( the standard sealed sub plan given by Denny is available at this link - http://www.gr-research.com/pdf/singleservo.pdf )


Obviously I don't have required skills so I have hired a carpenter who was known to me already, to carry out the cutting of the MDF and fixing the panels together etc.

We started the build in the evening today, and have been able to cut the mdf sheet in to 15 panels of the required size ( I will give more details of the sizes etc in next couple of days )

I need some help with next steps after putting the enclosure panels together, i.e for damping the cabinet etc.


My questions are :

1) I learnt from a few of our FMs that I should add bitumen sheets for damping, but when i went out in the market and visited quite a few hardware shops none of them seem to know what bitumen sheets are, please can some one guide me with below :

A > what kind of shops keep bitumen sheets
B> How much of it will be needed for a sealed sub of 1.5cubic feet?
C> and more important are bitumen sheets are called bitumen sheets or something else in the local market ?

2) I also learnt that in addition to bitumen sheets i should use Polly fill or Glass wool as its this kind of material makes the sealed subs work like bigger enclosures.
A> Please you guys help me know whether Polly fill is better or Glass wool? Is glass wool is known to create some health issues ?
B> How much of Glass wool or Polly fill should be used for 1.5 cubic feet sealed enclosure
C> How are we supposed to use this material inside the enclosure i.e do we need to stick this inside the enclosure i.e above the layer of bitumen sheet or only use on specific panels or just need to stuff the cabinet with it?


Friends please help me with above so that i can do most of my week end and complete as much of the build as possible by Monday.

Thank you all and hope to build a nice sub with your help


PS - I will add the pictures of the build in progress , in next couple of days

Regards,
Naren

 

[captrajesh]

My questions are :

1) I learnt from a few of our FMs that I should add bitumen sheets for damping, but when i went out in the market and visited quite a few hardware shops none of them seem to know what bitumen sheets are, please can some one guide me with below :

A > what kind of shops keep bitumen sheets
B> How much of it will be needed for a sealed sub of 1.5cubic feet?
C> and more important are bitumen sheets are called bitumen sheets or something else in the local market ?

2) I also learnt that in addition to bitumen sheets i should use Polly fill or Glass wool as its this kind of material makes the sealed subs work like bigger enclosures.
A> Please you guys help me know whether Polly fill is better or Glass wool? Is glass wool is known to create some health issues ?
B> How much of Glass wool or Polly fill should be used for 1.5 cubic feet sealed enclosure
C> How are we supposed to use this material inside the enclosure i.e do we need to stick this inside the enclosure i.e above the layer of bitumen sheet or only use on specific panels or just need to stuff the cabinet with it?

congrats on the build & wish you all the best.

I'm no expert but would like to contribute my 2 paisa. My AP speakers had a 2-3mm layer of black sheet (having texture and appearance of cheese slices) which had bitumen sheets. Since they are primarily used to minimize cabinet resonances, I think you can use Asbestos laden bitumen sheets that are used to cover leaky old roofs. These would be available in shops selling building material. calculate the requirement as per the dimensions given I the drawing. Only thing is, ensure that every bit of it is firmly affixed onto the cabinet walls.

Glass wool is used to minimize standing waves inside the cabinet and need to be stuck after affixing the bitumen layer, all around the cabinet, with an extra layer behind the driver.

Hope experts would chip in with more elaborate suggestions.

 

[magma]

you can also use dynamat or noisekill

very easy o use and performs well
one side is self adhesive too

avavilbe in most car audio shops

as for glass wool

 

[gobble]

I have decided to build a Sealed cabinet with all the sides having double layer of mdf sandwitched together, the original standard sealed box plan suggested to double only the front and rear panels however I consulted Denny as well as our FM Flash and learnt that doubling rest of the panels make the enclosure even more sturdy and solid.. hence this decision.

Good decision. I was researching for my 1st speaker build and I read and saw some charts and concluded that double layer should increase the decay of notes noticeably. Try and put some damping sheet in between the layers.

Is Dynamat or Noisekill suitable for sandwiching between two Ply's?

--G0bble

 

[naren2512]

Hey Capt.

Thanks for the prompt reply, I just looked at my balcony's aluminium roof / shed and it had some Tar like ( daambar as we call in hidi) sheet on it which reduces the noise of rain and also stops the water to leak in from the joints of the aluminum roof.

I took the pictures of the same, is this what we call as Bitumen sheet?

Regards,
Naren

congrats on the build & wish you all the best.

I'm no expert but would like to contribute my 2 paisa. My AP speakers had a 2-3mm layer of black sheet (having texture and appearance of cheese slices) which had bitumen sheets. Since they are primarily used to minimize cabinet resonances, I think you can use Asbestos laden bitumen sheets that are used to cover leaky old roofs. These would be available in shops selling building material. calculate the requirement as per the dimensions given I the drawing. Only thing is, ensure that every bit of it is firmly affixed onto the cabinet walls.

Glass wool is used to minimize standing waves inside the cabinet and need to be stuck after affixing the bitumen layer, all around the cabinet, with an extra layer behind the driver.

Hope experts would chip in with more elaborate suggestions.

 

[rjstyles]

you can also use dynamat or noisekill

Be ready to spend a fortune if you plan to use any of these brands. There is a better desi brand called dampmat. See here : DampMat - The Car Audio Damping Material | eBay
Better heat glueing properties and highly heat resistant,tested against dynamat.

A few of us already tried this for damping our cars. Seller is from punjab and is pretty well know in the automobile groups. Just another dude who went the extra mile with his research and gave us lesser mortals an affordable damping solution.

 

[naren2512]

Some of the WIP Pic


The GR SW-12-04 Woofer



Rythmic A370PEQ servo amp




DAY 1


My Carpenter made me wait for half day, and came by 6 pm only after multiple calls and we completed cutting all the panels in 3.5 hours







Next we marked circles and rectangles on the panels for front baffles, braces and back panel which were to be taken to market to get them cut from the market.



DAY 2

My brother and I took the front panles, back panles and braces to the market to get the circles and rectangles cut as per Denny's plan.

The guy from the market cutting the circular holes for the front baffle and braces and rectangular cut outs for the Amp, it took him total 1 hour do this all - He did a very good job all the panels were cut exactly as per the marking on the panel




Here is the final result after the cutting :

The back panels where the Amp will mount




The Braces and Front baffle B ( i,e inner baffle where the Woofer will mount )




These are remaining panels which comprise of 4 panels for 2 sides and 2 panels for top bottom each




Carpenter came by around 7pm and we worked till 11pm, the plan was glue and sandwitch all the 6 pairs of panles and keep them to dry for next 12-18 hours and after that fix them together to make the enclosure.

However when we were trying to put the panels together to see how the enclosure will look, he suggested not to sandwitch them first and then fix the double panels together and do it other way round, i.e to fix some panles together as a single layer ( i.e two sides, back and bottom panels and 3 braces) and after it dries completely, we will work on doubling the panles and I went ahead with his suggestion.

Below is the result of the 5 hours job (including the time spent for sanding the uneven panels ) !!





DAY 3

Most likely the carpenter wont come today as he is busy with work at a nearby site, Anyways its raining cats and dogs since morning in Mumbai so panels will get some additional time to dry



more to come ....

 

[spirovious]

Congrats Naren,all the best.

 

[naren2512]

I am not sure how can we sandwitch the damping sheet inbetween two panels of mdf or ply... ( mdf in my case) wont it reduce the strength of the enclosure?

Good decision. I was researching for my 1st speaker build and I read and saw some charts and concluded that double layer should increase the decay of notes noticeably. Try and put some damping sheet in between the layers.

Is Dynamat or Noisekill suitable for sandwiching between two Ply's?

--G0bble

 

[naren2512]

Thanks buddy

Congrats Naren,all the best.

 

[naren2512]

Hey buddy,

The ebay price is Rs 7,990 :sad: how many times better will it be as compared to bitumen sheets when it comes to dampening a sub woofer enclosure like mine?

Has anybody made comparison of this with bitumen sheets?

Be ready to spend a fortune if you plan to use any of these brands. There is a better desi brand called dampmat. See here : DampMat - The Car Audio Damping Material | eBay
Better heat glueing properties and highly heat resistant,tested against dynamat.

A few of us already tried this for damping our cars. Seller is from punjab and is pretty well know in the automobile groups. Just another dude who went the extra mile with his research and gave us lesser mortals an affordable damping solution.

 

[captrajesh]

Wait for Danny to respond. I pinged him to respond to this thread.

 

[GeorgeO]

Use threaded inserts to mount the driver on the baffle.

 

[Flash]

Hey Naren, the Journey so far is looking good.

The rule goes like this

Damp a Ported Enclosure and Stuff a Sealed one.

However. Damping it with Bitumen sheets or alternate materials such as wool felt, etc etc does have it advantages for a sealed cab as well.

Another probable material you can use for Damping is Acoustic Foam from the likes of Anutone etc etc.. This for me personally is the best option.

However considering the space taken by Acoustic Panels in the enclosure. You would have to recalculate the Internal volume of the cab and rework the dimensions.

 

[anm]

i have got the no rez sheets for my sub from Danny. will I be needing any damping and
/ or filling beyond that? Mine will be a sealed sub. Dual woofer makes walls larger and more prone to flexing

 

[captrajesh]

i have got the no rez sheets for my sub from Danny. will I be needing any damping and or filling beyond that? Mine will be a sealed sub. Dual woofer makes walls larger and more prone to flexing

AFAIK nothing else is required but you may ping Danny to confirm.

Here is a X-LS Encore build thread on the other forum where the maker has used alternative materials to the 'No Rez'

 

[naren2512]

Use threaded inserts to mount the driver on the baffle.

Had not thought of that, the woofer actually may have to be removed a few times and put back in until the finishing is done so wood screws may not be a good idea. Thanks for the alerting me on same

However will it be a good idea t ouse threaded inserts or T-nuts and threaded nuts? any suggestions what might the best way to mount the woofer? ( personally I have seen/used neither of the two and only saw them on google two mins ago )

Also should we plan something similar for the amp or normal wood screws will be fine?

Lastly how difficult is it to fix these exotic kind of screws in the mdf as compared to wood screws?

Regards,
Naren

 

[naren2512]

Thanks buddy,

I dont plan to make any changes to internal size/ volume suggested by Dennny, cant experiment on something this expensive!

I think I should use something relatively thing for damping, either bitumen sheets or something similar which is not too thick and in addition glass wool or polly fill which ever gets decided based on the suggestions from all the knowledgible folks here including you

Regards,
Naren

Hey Naren, the Journey so far is looking good.

The rule goes like this

Damp a Ported Enclosure and Stuff a Sealed one.

However. Damping it with Bitumen sheets or alternate materials such as wool felt, etc etc does have it advantages for a sealed cab as well.

Another probable material you can use for Damping is Acoustic Foam from the likes of Anutone etc etc.. This for me personally is the best option.

However considering the space taken by Acoustic Panels in the enclosure. You would have to recalculate the Internal volume of the cab and rework the dimensions.

 

[cmsajith]

glass wool / polyfill, is it included in the original design, if not, dont use it as it will change the response from the designed enclosure.

 

[doors666]

0.5 kg for 1 cuft is the approximate rule for sealed, half of that for ported.

The kind of a sturdy cabinet this is, i am surprised you need damping. I remember reading somewhere that the biggest problem with diyers is over engineering. i think it was from some one on the PE staff.:lol: