# Please help with SDX15 build.



## SubNub (Mar 13, 2011)

Hello,

I'm looking for some help with what will be my first DIY sub.

My plan was to build something as capable if not more so than an svs pc13u without the cost involved in getting one shipped here (being the u.k), plus I thought it would be fun.

So I bought a few things to get the ball rolling; driver is an SDX15, amp is an EP 2500 also have a BFD 1124.

As this is mainly for HT, I guess I need to go the ported route, which, due to the volume required and restricted floor space, would need to be a sonosub.

So I am trying to decide on a good volume and tune, based on 600mm int tube and 152mm int port, but I am having a hard time understanding how to determine the correct values so as not to damage the driver (from unloading is it?) without requiring a filter (more cost).

I saw from an older thread that Mike P posted possible builds running on 1000w, one 240L with 20Hz tune and the other 350L at 15Hz.

I *never* watch at reference level (usually around -15db max) so do I even need to worry about bottoming?

I would love to go for a small sealed sub but things get more complicated for me with eq'ing and power limits.

Help would be much appreciated on this as the tubing is going to cost more than I had anticipated so I want to make sure it's right before hand.

Cheers.


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## SubNub (Mar 13, 2011)

The driver and amp arrived today so I would like to test it out, only I don't know where to start wiring a dvc driver never mind setting the ep2500.

From what I have read so far is; I can set the ep as a monoblock and then wire the sub in parallel to get the most output from the amp.

But 2.4kw is a little overkill no?

I'm scared of breaking stuff before I even start the build.


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## Moonfly (Aug 1, 2008)

Click on quick links and go down to tools. There you will find a driver wiring diagram that will show you how to wire up your driver.

Even if you mono the amp into the driver, your not supplying its total power continuously and how much power the driver gets is dependant on the use of the volume control. Chances are the driver will bottom before you put to much power in, which will tell you to turn it down, but this is somewhat dependant on the design. Its always better to have an overpowered amp running with ease than to have an underpowered amp really struggling, just be sensible with the volume control, thats all.

If you run your driver in free air to begin with, then be careful and run very low volumes to begin with. The only real reason to do this is to test the driver works, and if you want, to run it in a bit before it goes into its cabinet, otherwise you wont properly test your driver till your sub is built and up and running.

Ported will extract the most spl from your sub at lower frequencies, so if thats what your after, then that settles that, all we need to know is how big a sub can you build. A tune of 15hz is the generally accepted point at which you can run without a filter, but you may get away with that slightly higher if you dont run too loud. What tuning frequency is best will somewhat depend on the size of the sub itself, se we need to nail that one down first.


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## SubNub (Mar 13, 2011)

Thanks for the reply, and yes I simply want to make sure both the amp and driver work or it's back to square one.

As said I am sensible when it comes to the volume and have never heard any disturbing noise or distortion from my current sub.

I'm glad you mentioned size as I have another question relating to that; I know the driver needs enough room to breath in a downfirer, but is there a rule of thumb for the port too?

The reason I ask is that my room is a loft room with sloping ceilings going from 1.5m lowest to a 2.2m apex, so if I was to make the sub around 1.5m tall and place it close to a corner, would that pose any problems?

Cheers.


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## SubNub (Mar 13, 2011)

, I think there might be a problem with the amp. 
If I run it in normal two channel mode then it works fine on both, If I run it in bridged the clip light for channel one stays on and no output. :hissyfit: 
It also does some strange random lights after I hit the power off.

Ok after a quick google I found someone else having the same problem and switching the hpf off for channel two fixed it. Yay.


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## Zeitgeist (Apr 4, 2009)

So the amp and driver work and now you're back to a cabinet design?


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## RodK (Mar 30, 2011)

SubNub said:


> So I bought a few things to get the ball rolling; driver is an SDX15, amp is an EP 2500 also have a BFD 1124.
> 
> 
> I would love to go for a small sealed sub but things get more complicated for me with eq'ing and power limits.


You definitely have the power and the eq to go sealed if you want. I have an SDX15 coming my way and I am going to be building a 4 cu.ft sealed box for it. I am 50/50 ht/music though.


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## SubNub (Mar 13, 2011)

Zeitgeist said:


> So the amp and driver work and now you're back to a cabinet design?


Yep.

I'm no carpenter however so will be getting assistance in the construction aswell.

This should probably be in a "Not quite DIY, get clever people to tell you how it works, then get skilled people to help build it" section of the forum. 



RodK said:


> You definitely have the power and the eq to go sealed if you want. I have an SDX15 coming my way and I am going to be building a 4 cu.ft sealed box for it. I am 50/50 ht/music though.


The main reason I said I'd like to go sealed is that with a smaller enclosure it would leave me more choice for placement. However I also like that many recommend sealed for music and I listen to a lot.

I currently have a front firing bk monolith which if I put up front with the mains (Tannoy 636), sounds pretty nice for music, trouble is it for whatever reason doesn't dig low for ht and the only way I can feel the bass from ~20Hz is in it's current position behind.
The problem with it in then is; I can't get it to blend well at all unless I upmix to 5.1 (also have 636's as rears.) which isn't ideal.

So I usually just use the pure audio mode and thx mode for music and ht respectively, but I do miss the extension from using a sub with music as the mains aren't exactly full range.

"So just buy another monolith and stick it up front"

Well this I very nearly did, however in with this build I'm helping a m8 out by selling him the monolith as he wanted a ht sub with a budget of just £300.


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## SubNub (Mar 13, 2011)

Thanks for moving the thread, I can't believe I didn't see you have a CSS section.

I do still have many questions regarding the build, not all specific to the driver though, more sonosub in general.

I'm thinking of going with psp 6" port as it would be slightly cheaper to have it shipped here than my qoute for it out of sonotube.
Plus I don't have to worry about getting a donut made.

Any reason I shouldn't use a psp port and if not; can anyone tell me the wall thickness so I can punch it into sonosub.exe as it's not listed on their website.

Sonosub is telling me to fit damping material to the endcaps, what is the best material for this?

I was expecting the driver to come with a gasket of sorts to sandwich between it and the enclosure, is this not needed or do I need to buy/make one?

I'm thinking of using the long bolt through type binding posts, would there be any problems with fitting them to the driver endcap and what is best way to make sure they are sealed?

Are the endcaps just glued in?

I've looked at many builds but most just show periodic pictures without much of a description of what they have done.
For example the last two sdx15 sonosub builds I've looked at make it seem like they didn't bother with an inner flare from the pictures.

Again help is much appreciated and apologies for my lack of knowledge.


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## Mike P. (Apr 6, 2007)

What net volume and tuning frequency are you considering?


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## SubNub (Mar 13, 2011)

I think I've got this right, I'm currently looking at 320L effective with a 14.x tune, which keeps it nicely under my 1.5m height limit.
This would also mean that the psp kit + an additional jointing ring and tube section wouldn't require any cutting as it should be roughly 29" including flares.


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## Mike P. (Apr 6, 2007)

320 tuned to 14 or 15 hz works fine. Since you don't listen at reference levels the PSP 6" would be better then 6" sonotube as the PSP port has the flares. Port air speed won't be an issue unless you really push the sub.

Fiberglass insulation works well for damping the top end cap, it will need to be compressed to about 4 - 6" thick.

Use weatherstripping tape to seal the driver to the baffle. 

Silicone will seal the binding posts.

End caps are glued in, they must be tight fitting to begin with. The inside of the tube has a transparent release film that must first be peeled off, no glue will stick to it.


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## SubNub (Mar 13, 2011)

Thanks Mike P.
:T
I'm hoping to get it built within the next few weeks so will update this thread with my progress and any new questions that arise.


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## SubNub (Mar 13, 2011)

I'm beginning to think this was a really bad idea..... I've gone about it *&£! first. :dumbcrazy:

I should have found someone to do the woodworking and get qoutes before I started ordering stuff as what I had evisioned being around £700 build total is quickly turning into 1k.

I have already spent close to £600 on the bfd, driver, amp, port and fittings, the sonotube is going to be over £150 and I've just had some scary quotes back for the ply discs (min £250.)

This still leaves me a lot of work with chance of making mistakes with costly materials.
Not sure what to do now.

Ok flapping over.... :hissyfit:
I have found someone and had the discs made at a much better price.
Sono is coming on Friday and I've got some tall bun feet on order.


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## SubNub (Mar 13, 2011)

Ok I now have my sono in and carpeted and the discs are drilled, sanded and glued ready for priming/painting.

Just a couple of questions regarding damping;
I have seen in previous builds people lining the inside walls of the sono, Is this neccesary?
Same thing with the exterior of the port?

Can I use open cell foam on the top cap instead of loft insulation? (reason being I already have one or two large square tiles 50mm thick at peak).

I will make a new thread with pics and details of the build when it's built and I'm ready for some testing.


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## Mike P. (Apr 6, 2007)

How tall is the tube?


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## SubNub (Mar 13, 2011)

1.3m


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## Mike P. (Apr 6, 2007)

Lining the sides isn't necessary, packing in 4" to 6" at the top is to eliminate any resonance issues caused by the tube height. 

The inside of the tube has a transparent release film, it needs to be removed before you mount your end caps as glue will not stick to the film.


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## SubNub (Mar 13, 2011)

Thanks again Mike, 

so I should not use the open cell foam then?

As for the release film, mine had none, just bare card.


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## Mike P. (Apr 6, 2007)

Don't use foam, compressed fiberglass insulation is very effective.


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## SubNub (Mar 13, 2011)

Thankyou very much for all of your help.


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## Mike P. (Apr 6, 2007)

You're welcome.



> I will make a new thread with pics and details of the build when it's built and I'm ready for some testing.


Looking forward to it!

​


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## SubNub (Mar 13, 2011)

Hope you don't mind, but while I was waiting for a response regarding damping I had a little dig around the net and found this as a reply;

"a little dampening material at the top cap isn't going to help with a high SPL sound wave unless it can absorb a very substantial amount of acoustic energy. Then, if it can absorb lots of the sound wave, then the acoustic loading on the speaker will be significantly altered. One of the nasty little rules of enclosure dampening is that if the dampening can significantly reduce low frequency waves, then the load presented on the driver will appear to be a larger enclosure with a lower Q, which tends to make the sound looser, floppier, and less "tight" and "dynamic"."

He also states;
"I would attempt to keep any tube well under 42 inches long internally (the start of resonances at 80Hz and upward) to maintain a 100% pressure chamber performance for the enclosure". 
to help prevent; 
"uneven pressure bands to the tube sides going up and down the length. If you are going to ensure the crossover for this sub is always under 45Hz, or so, those length based resonances shouldn't be a problem."

and finally;
"to reduce weird transient response issue at the lowest frequencies, I recommend attempting to keep the length of any port under 2x of it's diameter. So, if you are using a single 6" port, keep the length under 12". If you have three 3" ports, that is the equivalent to single 5.25" diameter port, so keep the length under 10.5". And so on."

hmmm......


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## Mike P. (Apr 6, 2007)

I have no idea where you got that from, lets see some test results to verify the statements.


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## SubNub (Mar 13, 2011)

I wasn't trying to discredit your advice, just thought it odd that this guys views go against a lot of past builds.
It was from another forum posted last year.


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## Zeitgeist (Apr 4, 2009)

SubNub said:


> I wasn't trying to discredit your advice, just thought it odd that this guys views go against a lot of past builds.
> It was from another forum posted last year.


In my experience, you'll find advice for every single different damping option there is.

Everywhere from damping every sq in, no damping and damping with exotic materials.

The most common is what Mike P. mentioned..


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## SubNub (Mar 13, 2011)

Managed to grab a roll from Homebase for £3! Now I need to find some gaps to shove the rest in 

I have the sub built and running it in atm, sounding sweet so far :R

I currenty have an intelliplug which I use to power a 120mm PC fan when I turn the receiver (hotyo 876) on, is it safe for me to use this method for the ep2500 and bfd?

I have tried it and noticed nothing bad, just wanted to make sure I won't damage the amp or bfd by simply killing their supply.


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