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

[naren2512]

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.

The plan given by Denny on his website only tells you about the dimensions of the panels to be cut and the thickness of mdf to be used for the enclosure.

When i contacted Denny he did suggest to use No Rez + pollyfill or Glass wool.

Since i did not order for No rez hence the need to hunt for a cheaper indian alternative for the same.

For the Glass wool and Pollyfill need to decide one between these two and also i have to try to know how to use it and how much etc. Some FMs have suggested glass wool is far superior then pollyfill while others have only used pollyfill and continue to do the same.. so you see why i am still confused

If anybody has used different type of damping sheets, i.e Bitumen sheets, car damping sheets suggested by Magma above or any other ones, then please can you share from your experience as to whether there was a noticeable difference between Bitumen sheets and other material used?

Also has anybody used Pollyfill and Glass wool both? if so please can you advise which one you found to be better, and how much difference did you find in the two, which one would you recommend?

Regards,
Naren

 

[quad]

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

Nice build.

It is better to use threaded inserts (D-type nuts) compared to T-nuts (tiger nuts).
T-Nuts may come loose later.

There is a lot of info on this on related threads on others forums. For ex -

Mounting drivers in mdf: Threaded inserts? Or just wood screws?

 

[anujmishra]

I bought bitumen sheets at the rate of 70 Rs per meter. It is 3 feet wide. Made layer of three sheets and stuck on wall with the help of silicon. But question is how to stick these sheets perfectly onto inner wall so that it will not come out.

This weekend I will try with heat gun. But after that also it is risky and there are chances that it may come down in due course of time. There is need to stick it in all direction.

Is it recommended to use wooden beads on top of it 1/2 inch wide just to make it firm?

 

[naren2512]

Hey Buddy,

Can you advise what kind of enclosure you used the bitumen sheets for? i.e is it a speaker enclosure or a sub? whether its sealed or ported one?

Also how many layers of bitumen sheet are usually recommended ? and just a thought - wouldn't sticking base layer first, letting it dry then adding second and doing the same for third, have helped better?

Also i have been told silicone sealent is for air proofing the joints, so guess Fevi Bond may help stick these sheets better?


Experts - Request more knowledgeable and experienced folks to chip in as well and suggest how to stick bitumen sheets, how many layers and where all it should be stuck


Regards,
Naren

I bought bitumen sheets at the rate of 70 Rs per meter. It is 3 feet wide. Made layer of three sheets and stuck on wall with the help of silicon. But question is how to stick these sheets perfectly onto inner wall so that it will not come out.

This weekend I will try with heat gun. But after that also it is risky and there are chances that it may come down in due course of time. There is need to stick it in all direction.

Is it recommended to use wooden beads on top of it 1/2 inch wide just to make it firm?

 

[anujmishra]

Hey Buddy,

Can you advise what kind of enclosure you used the bitumen sheets for? i.e is it a speaker enclosure or a sub? whether its sealed or ported one?

Also how many layers of bitumen sheet are usually recommended ? and just a thought - wouldn't sticking base layer first, letting it dry then adding second and doing the same for third, have helped better?

Also i have been told silicone sealent is for air proofing the joints, so guess Fevi Bond may help stick these sheets better?


Experts - Request more knowledgeable and experienced folks to chip in as well and suggest how to stick bitumen sheets, how many layers and where all it should be stuck


Regards,
Naren

Mine is ported on based on locally available Peerless Driver and Amp. Box size is almost 18X18X18.75 inches.

This build is same as of t.anthony's sub build thread. I have my thread too.

I sticked three layers of bitumen sheet and still is in temporary mode. I have to find fool-proof mechanism to stick on the all sides of wall with proper support. My experiments is also underway.

 

[sbg]

Mine is ported on based on locally available Peerless Driver and Amp. Box size is almost 18X18X18.75 inches.

This build is same as of t.anthony's sub build thread. I have my thread too.

I sticked three layers of bitumen sheet and still is in temporary mode. I have to find fool-proof mechanism to stick on the all sides of wall with proper support. My experiments is also underway.

Try liquid nails - these are available locally from Pedilite.

 

[naren2512]

Friends,

Here is the fruit of last four days... my sub enclosure is ready ... just need to damp it, put in polly fill / galss wool and mount the sub and amp .. which will be done on the week end..

All the sides are double layers rest all is same as per the standard sealed box design given on Denny's website.

Just the box weighs around 26 kgs, after putting in the amp and woofer final weight should be close to 41 kgs...



Regards,
Naren

 

[Rgn1]

Friends,

Here is the fruit of last four days... my sub enclosure is ready ... just need to damp it, put in polly fill / galss wool and mount the sub and amp .. which will be done on the week end..

All the sides are double layers rest all is same as per the standard sealed box design given on Denny's website.

Just the box weighs around 26 kgs, after putting in the amp and woofer final weight should be close to 41 kgs...



Regards,
Naren

Hi Naren, Had a couple of basic questions.

So did you use double layers for front and rear baffles as well or is it only for the sides, top and bottom?
Did you maintain the internal volume as per the single layer design? If so have you increased the size of front and rear baffles to include double layers of sides, top and bottom?
So will change in front and rear baffle sizes have any effect on the sound, or is only the internal volume that matters?
Did you use nails as well as Fevicol to attach the baffles and the braces or is it only Fevicol?
By the way did you use Fevicol or did you use some other adhesive?
Did you use clamps to aid in binding?
Have you decided on the finish ?

Yes I know it is not a couple of questions , but will much appreciate your inputs. Box is looking good by the way .

Thanks!

 

[naren2512]

Hey buddy,

Denny's plan for a standard sealed sub enclosure suggests doubling the front and back panels so I did that and in addition I doubled the sides, top and bottom and this required me to increase size of the outer front panle ( called front baffle A in plan) outer back panel ( called outper panel E in the plan) and the top / bottom but this did not change the internal volume of the sub hence i dont think there will be any adverse impact on the sub's performance infact it should make the sub more sturdy and stronger hence should better the performance also this was done after consulting one of our FM Flash who has some experience of this as he made his own sub all by himself, also i had consulted Denny and he had said its good to double the top/ bottom and sides.

The suggested glue to be used for sub builds was " PVA Glue" and Fevicol SH is PVA based so I used this one in addition i used very thin pressing nails of 1.25" ( but used as less of them as possible and made sure that they are inserted right in the middle of the mdf sheet and little away from the corners to ensure that the mdf board doesnt get torn off )

I did not use any clamps to aid in binding ( i dont even know what these are)

For the finish I am thinking of either using cherry red vineer or wood polish, i would prefer vinner more as it will match well with my PSB speakers.

Hope this helps, and incase if you have any questions do shoot


Regards,
Naren

Hi Naren, Had a couple of basic questions.

 

[baladevan]

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.

perhaps you can use glass plane for internal components since glass is always better to reduce resonance compared to wood or plywood

I have seen a build of a stereo sub (passive), the flat board and floor of the sub was made of glass and it has two 8 inch drives ( till date I have not auditioned such a fantastic sub )

 

[naren2512]

perhaps you can use glass plane for internal components since glass is always better to reduce resonance compared to wood or plywood

I have seen a build of a stereo sub (passive), the flat board and floor of the sub was made of glass and it has two 8 inch drives ( till date I have not auditioned such a fantastic sub )

Do you mean Glass wool when you say Glass or Glass panels?

 

[naren2512]

Friends,

The weekend is back !! so I am thinking of finishing off with my sub build over the week end, by damping and stuffing he polly fill/ Glass wool and mount the Amp and driver.

I had contacted Denny to know :

1) What all panels we need to apply the damping sheets on - On which he replied that we can apply the damping sheets on all the panels obviously on the internal sides just that we dont need to apply these sheets on the braces

2) What kind of stuffing we should used for the selaed sub, should it be polly fill or Galss wool - He said either is fine

3) How much of stuffing by pollyfill or Glasswool needs to be done for the sealed enclosure - On this he responded saying that we can have a thick layer of around 6" infront of the amp.

He also provided me with the below link of another forum, which has pictures uploaded by one of the DIYer, of how he has damped and stuffed the sealed sub enclosure with polly fill. ( however he had kept used seperate box for amp so that was one big difference)

The link is here - Servo sub cabinet

Now I urgently need some suggestions for followings to be able to complete my sub build this weekend with the help of fellow members here:

1) I went to see the Bitumen sheets in the market today, and they seemd to be little stiff / hard atlest they were not soft.. so what is the best adhesive that we can use to stick the bitumen sheets inside the enclosure? - one FM had suggested Fevi Bond to me, however after looking at the sheet it seems hard that fevibond will be able to hold the sheet closer to panles for long.. please can you all share your experiance and advise if Fevicol or anyother adhesive will be better ?

2) For stuffing the polly fill / Glass wool infront of the amp as suggested by Denny, It actually means putting a thick layer on top of the plate amp on the inner side, can there any problem as the Polly fill/ Glass wool will be in contact of the amp? can it damage the amp?

3) Is it advisible to just put in loose polly fill/ glass wool to make the 6" layer or should it the whole bunch of material be tied up with help of a thin thread or something so the the material doesnt spread inside the enclosure while playing the sub?

4) While applying the bitumen sheet on the insdie of the panel on which drive mounts and on the panel where amp mounts, is it ok to apply the bitumen sheet too close to Amp / Driver ? or should we keep some distance? do these equipments get too hot? and can bitumen melt if these equipments get hot?

Please can some experianced folks help me with above based on their knowledge and experiance?

Thank you very much for your help in advance and have a very happy week end ahead !!

Regards,
Naren

 

[naren2512]

Today being week end continued with the build, and bought 1 meter of Bitumen sheet and applied single layer of it on all the internal panels ( except the braces)

After an hour I Fit the amp in the enclosure, stuffed the enclosure with around half KG of lose Polly fill, filled it only in the area between First and Third braces i.e no polly fill between Woofer and first brace as well as between last brace and plate amp so as to get around 6" layer as suggested by Denny at the same time kept it little away from the Amp.
/
Not sure if i did it right way, if not then please do suggest if any changes needed.

Below is the pic showing the box with amp fitted and stuffed with polly fill :




There after mounted the drive and this is how the Sub looked :





Now need to play the sub for a few hours at least to be able to comment how it sounds... for this i am using china made cheap Red Yellow White colored RCA cable which my cousin had got with Rs 2000 DVD player 5 years ago.. so will it be ok to use this RCA cable to see how sub sounds or there is a huge difference between such cheap RCA cable and a Decent Sub RCA cable by likes of DACs?

Will I at least get a decent idea which this RCA cable as to what my sub is capable of?

Regards,
Naren

 

[Danny Richie]

Now I urgently need some suggestions for followings to be able to complete my sub build this weekend with the help of fellow members here:

1) I went to see the Bitumen sheets in the market today, and they seemd to be little stiff / hard atlest they were not soft.. so what is the best adhesive that we can use to stick the bitumen sheets inside the enclosure? - one FM had suggested Fevi Bond to me, however after looking at the sheet it seems hard that fevibond will be able to hold the sheet closer to panles for long.. please can you all share your experiance and advise if Fevicol or anyother adhesive will be better ?

2) For stuffing the polly fill / Glass wool infront of the amp as suggested by Denny, It actually means putting a thick layer on top of the plate amp on the inner side, can there any problem as the Polly fill/ Glass wool will be in contact of the amp? can it damage the amp?

3) Is it advisible to just put in loose polly fill/ glass wool to make the 6" layer or should it the whole bunch of material be tied up with help of a thin thread or something so the the material doesnt spread inside the enclosure while playing the sub?

4) While applying the bitumen sheet on the insdie of the panel on which drive mounts and on the panel where amp mounts, is it ok to apply the bitumen sheet too close to Amp / Driver ? or should we keep some distance? do these equipments get too hot? and can bitumen melt if these equipments get hot?

Please can some experianced folks help me with above based on their knowledge and experiance?

Thank you very much for your help in advance and have a very happy week end ahead !!

Regards,
Naren

I am pretty sure I have answered these questions via e-mail and via your phone call already, but will answer them again if it helps others.

1. The function of the bitumen sheets is mass-loading or deadening of the panels. There is no problem in using these to good effect. They can even be glued in with Silicone.

2. You can place the poly-fill or fiberglass insulation right up against the plate amp with no issues.

3. You can just cut an over-sized piece of fiberglass or poly-fill and place it in the back of the box against the inside of the amp. It will stay in place just fine. The movement of the woofer does not really move it around. there is really no air flow in the box, just changes in pressure.

4. You can put the Bitumen sheets on the walls near the woofer or amp if you want. It will have no ill effect on either, but have little benefit either. Both of those panels have had the majority of their centers removed. So there is little left to resonant.

I hope that helps.

 

[Danny Richie]

There are some good build pics here that shows the insides.

Servo sub cabinet

Where ever you see No Rez in there is where you want to lay in a packed layer of insulation. About an inch or two thick is plenty. Then a loose fill about 6" thick in the back of the box placed against the amp.

 

[captrajesh]

Hey Naren2512,

It's been a while since your last post. Looking forward to latest developments.

 

[Rgn1]

Hey Naren2512,

It's been a while since your last post. Looking forward to latest developments.

Hi Naren,

So how did it turnout? How was the Sub sounding?

By the way, how did you manage to stick the bitumen sheets to the wall? Glue? Heat? And did you counter-sink the Front baffle A to fit the woofer and by how much? And if possible could you please share the changed dimensions of the box with the double walls on all sides?

Thanks!

 

[Hari Iyer]

Hi Naren,
Was just a bit curious to know where is the vent of the sub-woofer? Just did not read the entire post to be honest. Or is it a sealed enclosure? If its a vented enclosure then as per my experience the enclosure is little over damped as per the image posted. The air pressure in the enclosure is important for a vented enclosure performance and you need to damp it not too heavily. There should be some scope for the air inside the enclosure to reach the vent else there will be pressure difference affecting its performance. As suggested by Danny, have all the panel walls damped by one layer of bitumen sheet and one additional sheet to the rare panel as the back panel will have the maximum pressure. Have the polyfill damping material only at the bottom of the enclosure so as to not obstruct the vent. Leave the rest of the enclosure empty. Sometimes vented enclsoure are fully damped (not stuffed) with loose polyfill (lower density) in case of 2 way BS and FS where the woofer is also used as a mid-range driver. This is mostly to damp the mid-range and not the low freq. Since you are using it as a subwoofer you may not require the heavy damping of the enclousre.

My two cents.

 

[captrajesh]

@Hari Iyer, the subwoofer cabinet is sealed if I'm not mistaken.

 

[naren2512]

Hey Rgn,

Sorry for late reply, i used Fevi bond to stick the bitumen sheets to the walls.

FYI - you must be careful while cutting the bitumen sheets in small pieces as its little bit hard so you may not be able to cut it using usual scissors.. for me my carpenter did this job of cutting and then sticking it to the insides of sub.

I dont remember the exact changed dimensions so will have to make rough calculation on paper to tell you those but since its has been while since you asked this so i am assuming you would have calculated it by now, if not let me know and i can help you with the calculations.

Regards,
Naren

Hi Naren,

So how did it turnout? How was the Sub sounding?

By the way, how did you manage to stick the bitumen sheets to the wall? Glue? Heat? And did you counter-sink the Front baffle A to fit the woofer and by how much? And if possible could you please share the changed dimensions of the box with the double walls on all sides?

Thanks!