Acoustic Elegance AV15-X Dual Driver Opposed

AngelEyes

Distinguished Member
After much deliberation of what to do with the two AE AV15-X Subwoofers Russell conned me into buying, I have decided upon a sealed twin opposed driver design. The closest comparable commercial example I have seen is the Seaton Submersive.

The main reason for going this route is to produce a relatively small cabinet that won't have one particularly large dimension as most most subs with both drivers on the same face tend to.

I am hoping having some distance between the bass radiators will give a more even response as hopefully each driver will tend to excite modes in different places relative to the listening position. Any cancellation of driver vibration this configuration produces will be an added bonus.

The sub will be powered by the ubiquitous Behringer EP2500 via Speakon connectors to a terminal in the centre of the bottom face of the sub. This should make rotation of the subwoofer a simpler affair and hide the ugly cable/terminals as much as possible.

I would like the finished design to match my Walnut XTZ 99.36 Floorstanding speakers, which is why I am hoping to build a subtle curve to the sides of the subwoofer and apply a Walnut veneer.




I have a few options here, either the probably more difficult route of curving the side panels round a form/internal braces to create a true curved cabinet or to add the curve detail to a rectangular prism cabinet as more of a cosmetic finish.

The former approach may have the added benefit of reducing cabinet resonance but the latter may also improve the rigidity of the construction depending on the exact method I opt for.

Due to the heavy bracing I am using and 22mm construction my internal volume is 124L which is a bit small for these drivers (Qtc .726) but I intend to experiment with stuffing to bring it down if required.

I am also looking at using a BFD to apply some EQ to boost the bottom end a little but we shall see if this is necessary once in room.

Hopefully the build will start tomorrow but I am going to be taking my time with this so don't expect much progress just yet :D

Adam
 
Adam,

Be good to see how you get on. Same design as mine but with smaller drivers. You should be getting a good result and probably better than the PB13. The seaton submersive is the most talked about commercial sub out there and the results speak for themselves.

Good luck mate. Also best of luck with the curved sides. Will look really nice.

At least you won't need a crane to move it about like me.

Personally from what I have read, the lower the qtc the boomier and flabbier the bass. Ive been told that a qtc of about 1 would give the better result. QTC's of about 0.5 is a no go, I wouldn't go that low. I am not an expert but the people who are designing my subs are and I trust them totally.

cheers

Graham
 
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IronGiant

Moderator
Why do you feel the need for so much bracing Adam? I would have thought a single central brace would have been enough. For curves Bendy MDF is fantastic stuff to play with and used properly makes very rigid structures :thumbsup:

Dave
 

AngelEyes

Distinguished Member
Why do you feel the need for so much bracing Adam? I would have thought a single central brace would have been enough. For curves Bendy MDF is fantastic stuff to play with and used properly makes very rigid structures :thumbsup:

Dave
Just plain old overengineering. The best sub I ever heard had a lot of bracing too, so I see no harm in following suit. If there is a negative reason for this amount of bracing (apart from internal volume) then I am all ears :)

Is bendy MDF that stuff with loads of cuts in it?

Adam
 

Member 639844

Former Advertiser
Are you talking about the AA SW12. I'm sure that only used single braces. Given that the brace is only there to stiffen up the cabinet sides I cant see the advantage of double braces outweighing the volume lost in the extra braces TBH, I doubt there is much to be gained at all by doubling the braces like that, and if you wanted that amount they would be more effective evenly spaced rather than together :smashin:

Looks like its going to be a beast though. If the curves arent going to be part of the structure, it might be worth looking at using plywood to form the curve, perhaps with some curved struts down the side of the cabinet with it all fixed together to improve the cabinet strength on the whole. Not sure how ply would fit in with the rest of the cabinet and the materials you'll be using.

EDIT: another thought for the sides, I wander if you could get a thick piece of timber/MDF, and get a local joinery workshop to form the curve/dome on their machinery for that perfect finish?
 
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IronGiant

Moderator
Just plain old overengineering. The best sub I ever heard had a lot of bracing too, so I see no harm in following suit. If there is a negative reason for this amount of bracing (apart from internal volume) then I am all ears :)

Is bendy MDF that stuff with loads of cuts in it?

Adam
I like the belt and braces approach :thumbsup: the only concern was the impact on the internal volume.

Bendy MDF is the cut stuff, you slather the cut side with glue, form your curve and when the glue dries it's a strong as a solid sheet. It comes in 6mm thick sheets so you'd probably need to build up 3 or 4 layers of it for your build. It's not that cheap so you might be better off using two sheets of 18mm (or 36mm MDF if it exists) and getting a curve machined on the outside.

Dave
 

Nimby

Distinguished Member
If you glue lots of cut out formers (like the ribs on an aeroplane wing) onto the sides of your basic box you could wrap and clamp thin plywood to them to follow the curve. Then glue on another layer of plywood on top and clamp again to give a solid surface. The curve would only be cosmetic, but attractive none-the less, once vertically veneered.

Or, your could fix temporary formers to the surface of the box and use a router to cut away the material in between the ribs to leave a solid curve in the MDF. This would produce mountains of sawdust but would be quite quick. Do not underestimate the thickness of board required to accept a deep curve over any reasonable length. If you have no experience of working with a router on MDF choose a windy day. Then do it outside wearing a mask and goggles so next door cops the "dust storm." ;)
 

AngelEyes

Distinguished Member
Hi Nimby,

Exactly the techniques I was considering :smashin: but SWMBO has thrown another spanner in the works after visiting Russ and I at work today.

Apparently she is now actually interested in how the sub will look and being an interior design expert (she watches Grand Designs) feels like adding her tuppence. :suicide:

I have no idea what it will look like next...

I am also considering buying pre-veneered MDF and biscuit jointing 45 degree angled cuts for a perfect crisp finish but will probably try a test box first.

Today, I learnt a lot without doing very much at all. :)

Adam
 

Nimby

Distinguished Member
Hi Nimby,

Exactly the techniques I was considering :smashin: but SWMBO has thrown another spanner in the works after visiting Russ and I at work today.

Apparently she is now actually interested in how the sub will look and being an interior design expert (she watches Grand Designs) feels like adding her tuppence. :suicide:

I have no idea what it will look like next...

I am also considering buying pre-veneered MDF and biscuit jointing 45 degree angled cuts for a perfect crisp finish but will probably try a test box first.

Today, I learnt a lot without doing very much at all. :)

Adam
Perhaps she would prefer the sub to look like a windmill, an aquarium or a Victorian water tank on stilts? Mine still prefers the woolly tower of power. (SVS cylinder for the dirty minded) ;)

If I was lumbered with having a huge, ugly box in the room I'd make it out of clear polycarbonate or have an expert glazier cover it in thick mirror glass with polished edges.

I'm only saying this to cause Graham confusion. The more options he has the harder it is to make a decision. :devil:
 
Nimby,

Your a funny guy! :devil: I have already decided to wood veneer mine. I am using a white oak peel and stick (as it comes in the perfect size with no joins) I bought a load of different varnishes over the weekend and have decided to use an antique pine with 2 coats and finish of with a french polish to give a nice shine. With the white oak and the antique pine it gives a good match to my RS6's and the french polish really makes it nice and shiny with a good protection.

As it's going to be a big box a gloss black finish would be overkill and look stupid so wood is the way to go and the peel and stick works perfectly. Really sticks and doesn't come off when set.

cheers

Graham
 

IronGiant

Moderator
Graham, could you link me to the peel and stick (I assume it's from Vale Veneers?)

Thanks,

Dave
 
Dave,

Here it is mate.

{ Vale Veneers } decorative veneers

I cut up 5 different pieces of wood, stuck the wood onto the mdf and even folded it over the edge across the 25mm width part and even though it cracked very very marginally, once sanded the edge was really smooth. I tried covering the flat side and then cut a 25mm strip to stick on the thin edge joining the flat face and once sanded you can really see a join. I will take some pictures tonight and upload them tomorrow for you.

Its alot less hassle that the iron on stuff and it sticks perfectly. When you put the french polish on top (about 5-6 coats) it builds up a nice shine to the wood.

cheers

Graham
 

m4rky_m4rk

Member
:clown:
Perhaps she would prefer the sub to look like a windmill, an aquarium or a Victorian water tank on stilts? Mine still prefers the woolly tower of power. (SVS cylinder for the dirty minded) ;)

If I was lumbered with having a huge, ugly box in the room I'd make it out of clear polycarbonate or have an expert glazier cover it in thick mirror glass with polished edges.

I'm only saying this to cause Graham confusion. The more options he has the harder it is to make a decision. :devil:

You missed one

Concrete Forms


It might make Graham sick but many have used them(really, check Google) for sub enclosures.... smaller ones than the pic of course.

You could also cover it with soft padding and leather... then it would be a poof :clown:
 
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Oh my God! not cylinders again. The nightmare has started again! :(

Please I beg you no cylinders!!!!

Mmm... let me think big ugly box..... big ugly cylinder.

I wonder which one.... decisions decisions decisions decisionsdecisions decisions decisions decisions....:D


Graham
 

m4rky_m4rk

Member
Oh my God! not cylinders again. The nightmare has started again! :(

Please I beg you no cylinders!!!!

Mmm... let me think big ugly box..... big ugly cylinder.

I wonder which one.... decisions decisions decisions decisionsdecisions decisions decisions decisions....:D


Graham
If was big and ugly enough a concrete tube could be disguised as Roman pillar or structural support for the ceiling......:)
 

IronGiant

Moderator
Thanks for the link graham :thumbsup:

Dave
 

AngelEyes

Distinguished Member
Ok, I have finally decided on a design. I am going to keep things fairly simply with the construction as this will be my first effort. I will use a combination of biscuit joints and possibly screws depending on whether I can borrow all the clamps I need. I prefer the idea of no screws for some reason :suicide:. Material will be 22mm MDF, adhesive 'Bond and Seal'.

I have gone for an internal volume of 124 Litres (including drivers & baffles) which gives a Qtc of 0.726. I plan to use either a BFD to EQ a small boost in around 20hz or use wadding to increase the volume to around 134 Litres giving a Qtc of around .707, or perhaps a combination of both.

My goal is to deliver the upper bass punch I seem to miss out on in my room at the expense of bottom end extension which I have in spades with my alcove location.

Obviously I don't know if I have my calculations correct but I am banking on going smaller as the safe option. I also want to keep this as compact as is reasonable. This still gives me subwoofer over 15% larger (total volume) than the Seaton Submersive.





If this design performs in-room, I will veneer and add solid wooden legs and a 'table-top' to help it fit in with our decor a bit more. However I will probably not bother with a driver cover (magnets will be placed beneath the veneer just in case!).

With luck I will start in earnest tomorrow. :)

Adam
 

Nimby

Distinguished Member
Adam

Do you really want a top and a bottom panel edges intruding onto the driver panel face(s)?

If you have the the top, bottom and sides between the front and back. Then you can have all the panels (except the baffles) cut with the same saw setting. I think this will improve your chances of a good, tight, perfectly square box.

As to long clamps/cramps. They are available in cheap and expensive grades. I bought the long cheap ones with red handles and had to straighten the bars even though I selected the best of the lot. An alternative is a tourniquet clamp using a twisted rope (or sling) and a stick. This may require panel edge protection to avoid ugly bites. When using clamps use a bit of scrap wood between the jaws and your clamps to avoid obvious dents.

This website is an inspiration: He's a clever bloke:

Construction at Subwoofer-Builder.com
 

AngelEyes

Distinguished Member
Do you really want a top and a bottom panel edges intruding onto the driver panel face(s)?
Good point :)

I knew there was a reason I posted here :D

Adam
 

AngelEyes

Distinguished Member
How is this?

 

Nimby

Distinguished Member
Good point :)

I knew there was a reason I posted here :D

Adam
It depends which panels you are going to see most of the time and how soon you intend to veneer. If only one side is visible and you go for cloth grilles then the front and back don't matter. If you want to see a naked baffle with a visible driver then build the box appropriately.

As an example I built my latest IB manifold with a full plane side because the box was too tall at 6'4" to ever see the top. I could also give it a simple "black ash" finish straight onto the plywood. More preparation of the visible surface would have helped but it's not remotely intended as domestic furniture.
 

IronGiant

Moderator
Have you abandoned the idea of 45 deg cuts on veneered board then Adam?

Nimby is spot on with his advice of having the panel join where it is least obvious.
 

AngelEyes

Distinguished Member
Have you abandoned the idea of 45 deg cuts on veneered board then Adam?

Nimby is spot on with his advice of having the panel join where it is least obvious.
Based on past experience, 45 degree joints opens me up to more measurement/cutting mistakes so I won't try it this time round. Really the 45 degree joints will only be necessary if I buy pre-veneered MDF. If I actually do put legs on this, the corner joints will all be hidden so it is not so critical.

It was a nice idea but I am too impatient now the drivers have arrived! :D

Adam
 
Adam,

I don't blame you mate. Sounds like alot of [email protected] and not needed especially if you are veneering.

cheers

Graham
 

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