Completed build, for inspiration..

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Finally, after many months of protracted building and finishing..

Anyway, now Im' finished, and I thought I'd give something back to the forum in the form of som images and descriptions, hopefully to inspire others! :)

I decided I wanted a system that could cover all 10 octaves, and decided to go with dual subwoofer/ two way "satelites" actively driven. Posted some other threads on the amp and x-over design...

I decided to go for the Dayton RS39HF 15" woofers:

Dayton Audio RSS390HF-4 15" Reference HF Subwoofer 4 Ohm 295-468

They are in my opinion very good value for money and had a very low Fs, meaning it should be possible to go deep even with a closed box.

I must say that the build quality of these woofers were in deed excellent.

I chose closed boxes as this would give better phase response, plus it would be simple to simulate and predict.

A volume of around 160L gave a simulation of a slightly highish Q, but with the etensive stuffing I employed, my qualified quess is that I ended op fairly close to 0,7 anyway. Simulations allso showed that variations in response were quite modest ovver a relatively wide range of volumes about the calculated ideal. So in other words, not a very critical design.

I decided to go for a wide and low profile, making the enclosures less dominant in the living room, more like furniture than big loudspeaker boxes. The dimensions should make it easy to "blend" them in as a natural horizontal extension of a low stereo/ TV console.

I decided to build them from 22mm MDF with a heavy bracing matrix inside.

I allso decided to place them on a foot made from a 22mm MDF panel slightly smaller than the bottom og the boxes. Yhis effectively hides any missalignments and unevenness that would otherwise become evident if flush. Between the foot and the box, I sandwiched a sheet of 12mm thick "Armaflex" a mushy and elastic sort of cloced cell foam used for HVAC insulation. this was allso slightly smaller than the foot for the same reasons described above.
In addition to being an aesthetic design feature, the sandwiched foam may allso act to decouple any vibrations from the boxes. This is of course theoretical as I have no means to simulate or measure this.

For finish, I went with Teak veneer.
I thought long and hard about how I would finish the veneer.
Laquer was out, I feel it often comes out as "something on top of the wood. Allso geting a gloss laquer finish to look good on such large surfaces is extremely difficult. A matt finish would of course elliminate the problem of imperfections being revealed by reflective highlights, but that is just to "dull".

I decided i wanted a polished wood apearance, something that would give a nice natural near-gloss shine and bring out the lustre of the wood.

I went for oil sanding followed by a wax-polish.

After ironing the veneer on and trimming it, I manually sanded the veneer down to a smooth 100 grit finish.

I then started oil- sanding with two rounds of 240, two rounds of 340, and then finally one round of 400.
This left me with a silj\ky smooth finish with the pores and grain of the wood very nicely filled in.

I used something called Owatrol "edel olje", or "Noble Oil" as it would translated directly, which is intended for hardwood/ exotic wood. EDEL OLJE - Høyglans ocerflate til alle typer av treverk

Probably quite simmilar to various teak oils etc...

The oil-sanding is not as messy as you would probably expect, just put some covering paper on the floor and off you go.

Thebonus with oil sanding, is that you can do it indoors in your living room without creating a sanding dust-disaster. This is a good thing if you, like me, don't have a proper workshop and live under a climate which does not allways lend it self well to extended outdoor activities..

For polishing I used "black bison wax" from Liberon
Wax finishes : Black Bison Paste Wax - liberon.fr

Initially, I considered bees wax, but the liberon wax contained Carnauba wax, something I anticipated would take me closer to the natural shine and luster I wanted. A good choice it turned out.

The front of the boxes was finished with the same foam material used for the sandwich foot, something that allowed the woofers to be "countersunk and gave a very nice and professional finish.

The sound is awesome. if there is low frequency information in a recording, these subwoofers will reproduce it. Completely confident and without straining, even at considerable SPL. Having said that, I haven't dared to crank things up yet, but impressions so far tells me I have reached the end of the road as far as low frequency reproduction goes.

If I may say so my self, the build and finishing came out very nice, and I dare say I've ended up with something resembling heavy expensive audio equipment rather than some half baked DIY projects.

Now for the pictures...
 

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Thanks firechief! :)

Not the best pictures though, just some random snapshots I took during the build..

Here's aother one, not so lucky with that flash-shot, but it presents a bit more detail.

Forgot to mention; Used those "punch in nuts" and umbraco bolts you get as a kit from Parts express. Took great care to get the bolt-circle done precicely. This was indispensable in order to facilitate a smooth assembly and good finish!
 

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Hi, ahd thanks for all the nice feedback, much appreciated! :)

Chris, I'm driving each subwoofer with a Crescendo Millennium MOSFET stage rated at about 120W in to four ohm's (the woofers are 4 ohm), x-ed over at 65Hz 24 dB/Oct electronically.

According to the simulations I made, that shoudlbe enough to give full linear cone excrursion down to 20 Hz and about 105dB output from each sub.

FE3T,

The foam used was Armaflex, a closed cell foam used for HVAC thermal and vibration insulation: Armacell - AF/Armaflex Europe

It is very "squooshy" and can be a bit tough to cut cleanly without roughing the edges. A stanley knofe with brand new blade and steel ruler guidance is recommended.

A word of warning though, just after I took the pictures, I discovered that the foam had started to tear just at the edge of the woofer chassis, apparently the "stretch" imposed on the foma when bolting the woofer down was a bit too much. To stop this from propagating further, I took the stanley knife arround the edge of the chassis to releave the foam with a clean cut to stop any further uncontrolled tearing. It stil looks OK unless you get close.
I might get some fresh armaflex and redo the job, this time cutting the foam around the chassis as I bolt the woofers back down flush with the foam face.


With regards to stuffing, I used 100% stuffing with glass-wool (Glava) Mineralull Bygg

A fairly "standard" glass-wool type for building insulation etc..
I filled all the "cells" of the bracing matrix with uncompressed glass wool, except for the front "compartment" just behind the woofer, which was lined with axustilux mat to prevent dust contamination of the woofer.

The stuffing strategy was based on various reading around I did that suggested that this degree of filling would give an effective box Q of my chosen box volume of arround 0.7. As mentioned, this woofer seemed to be fairly insensitive to absolute box size giving very modest variations if kept arround +/-20-30 L within theoretical optimum (un-stuffed).

The bracing added significantly to material cost and construction effort, just drilling those 140+ holes with a hole saw (Which kept clogging up with MDF dust) was a major undertaing all by it self, but was well worht the effort. these babies are DEAD! (Hmm.. that came out a bit wrong..)

Finally a picture of one box with stuffing:

Oh, and for goodness sake, do not omit to put the internal wiring in place before adding the stuffing and slamming on the lid!!!
 

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You're welcome! Concidering the huge ammount of help I've gotten from the forum on various projects, I'm just delighted to give something back and answer any questions I can! :)

I wasn't quite happy with the sound here the other day, it was alla bit murky and "lacking spark", so I used the tone controll of my pre-amp (50Hz shelving) and played around to I gort something I liked. Semmed a 3-4 dB reduction in bass level made a big difference. I then went on and decreased the level of each sub by 3dB.

I then threw up my measurement mick in the listening position and ran a sweep through both channels. The enclosed image shows the result, ungated measurement wiht 1/5th oct. smoothing.

Not to bad I dare say... Seems the dual sub set up goes a long way in smoothing out room modes at low frequencies...just as hoped for! :)
 

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