Acoustic Elegance

As you may have seen, I did the sound system for Nick Barnett's night club a few years back. Recently he contacted me about the recording studio he was building at his home. He wanted a very high end monitor, the likes of the Genelec 1037's but without the $25k a piece price tag, and something that would actually fit in the available space. As the system would be all active with full DSP, I contacted my friend Mark Seaton. Some of you may be familiar with him.

We came up with a plan for a high end monitor that would allow for monitoring at up to 120dB all the way down to the 10hz range. The system consists of a B&C 8" coaxial driver with 1.4" compression driver, a pair of TD10X's for the midbass, and pair of custom 15" drivers for the woofer section per side. As the room is small, and to keep things simple, all sealed enclosures are used. Power is supplied by a 3 channel SpeakerPower amplifier for the tops and a single channel amplifier for the subwoofer sections.

The first issue I faced was to come up with something unique for the cabinets. I didn't want just an average plain flat box in the wall. I had some 3" quarter rounds and decided to order more to use them for the cabinets. They would essentially round out of the wall 3" then. I wanted to do solid oak inserts to really set off the cabinets and stain to match the oak floor to tie everything together.

We decided to use pocket hole screws to attach the front baffle board to the mdf quarter rounds as they would pull the seams tight. It is very difficult to clamp a quarter round without the screws in place first. We then used the clamps to pull the inside edges tight.





Next we ripped, planed, jointed and glued up the solid oak for the inserts. Nothing too fancy here. Just needed a nice flat slab to cut on the CNC.



Next we started to make the amplifier housing section that would go above the subwoofers and below the main monitors. Again the same quarter rounds are used as this will look like a continual column going up the wall.



Here we were cutting the inner baffle layers and the inner plate for the actual mounting of the amplifiers. Also at the far end is a template we used to cutout the oval shaped recess in the front baffle for the solid oak insert. We couldn't just cut this shape on the CNC originally because there was too little material left at the edges of the piece. It had to be trimmed out after the front was attached to the quarter rounds.



Here we have glued up the sides and tops for the subwoofer cabinet. The angles cut at the top match to the back side of the quarter round and the front baffle.



This is a test fit of the baffle and quarter rounds onto the rest of the cabinet. Looks to fit well. Lets glue it up.





The subwoofer cabinet is together and so is the amplifier section. Here is a pic of the two of them stacked on top of each other as they will sit when mounted in the wall.



Now we can cutout the solid oak accents on the CNC. Using small passes and a downcut spiral bit gives a nice clean edge with no chipping.





Now the part that gets very tricky is the front baffle on the main speakers. The cabinet mounts to the section of the wall that is angled down by 22 degrees. The 8" coax also has to be mounted so that it is towed in by 13 degrees to be at a proper angle at the listening position. Lots of angles means lots of cutting small pieces without a full 3d drawing up front. First we glued up the two layers of the front baffle.



Then once they were glued up we had to cut them to match the correct angle for the 8" coax. We also had to cut the solid oak accent at the same place. Here you can see the initial drop in of the oak accent on the tops and also on the subwoofer cabinet.





That's all for this update. More pics to come as the tops are finished up today and we begin the finishing process.

John

Hi John,

Very nice work, congratulations ! You seems like a really good wood worker ! Much better than I am...

Did you put the new drivers on the wait for this ? Hehe ! Seriously, any news about them ?

BTW, if you have close-up pictures of the line arrays in the other thread, all of us would like to see them !

Here is a little more update on the project. One of the greatest difficulties in the tops was the angles. The wall angles down at 22 degrees from above the amplifier section. The 8" coax also has to be angled in at 13 degrees to be properly aimed at the listening position. Ah yes, angles are so fun. Not only are their angles, but they have to match up to the 3" round over to look right. That essentially creates 2 more angles for me to make on the baffle. To do so with MDF would take a great amount of time stacking and sanding pieces. The ideal situation is to do it with a two part pour foam. This isn't your typical "great stuff" in a can. It's the same foam used in boat hulls and mold making. We use a 5 lb foam. It sands and shapes well and is in general quite durable. It's also quite good for getting rid of any kind of resonance on the baffle board. Here you can see where the foam was poured and carved to get the basic shape we needed.



Then we need to add some strength. We cut some fiberglass matting to lay over the foam. We brush a layer of resin onto the foam and the adjacent MDF surfaces. Then lay the matting on top and brush another layer of resin to fully saturate the matting. The strength is in the matting though, not the resin, so no need to overdue the resin. We put it by an electric heater to help it kick over more quickly. The matting hanging over the edges is trimmed off later.



Then a little light sanding and it is ready for an application of MarGlass to fill in any large dips and to build up slightly in some places where it was needed. Some more sanding and it is ready for the body filler. We "frost the cake" and try to cover everything that needs to be covered as smoothy as possible to avoid major amounts of sanding. Remember our shape is already how we want it and we don't want to build up much.



Then we sand and sand and sand some more. Any smaller holes get another application of body filler mixed up with a different color hardener to we can more easily see what we need to sand.



After this we sand one more time and come back with one final application of a lightweight spot putty to fill in any small imperfections. A final sanding and it's ready for a primer coat.

That's all for now. More details to go up tomorrow.

John

After a little more sanding they were ready for an initial black coat to really see if there are any things that need to be cleaned up. We sprayed the first coat of duratex on everything.






You can see that this one need a little more shaping to be perfectly symmetrical above and below the coax. Back to a little more marglass application and try again.

John

Damn fine job so far, John. Can't wait for the finished product pics.

dave

I know I'm a bit nitpicking, but John you are not afraid of the unpredictable baffle diffraction and reflexion caused by your exotic baffle ?

Some people care alot about that and some others don't care at all, would like to know where you stand.

simon5 wrote:I know I'm a bit nitpicking, but John you are not afraid of the unpredictable baffle diffraction and reflexion caused by your exotic baffle ?

Some people care alot about that and some others don't care at all, would like to know where you stand.

The fact that we are using a coax really eliminates most of that issue. It controls the directivity of the compression driver, so there is not much diffraction issue from the baffle itself. This was the only way I could figure out how to get the angle and make it look decent as well as eliminating most of any diffraction issues.

John

I figured maybe some of you might want to see the drivers that are going in these. The 10" midbass are the Lambda TD10X's. These have the copper faraday ring, full sleeve covering the entire pole, and also the aluminum phase plug, chrome plated. Here is a link to all the old driver info. I'll copy the info over soon when I can format it nicely for the forum.

Lambda TD10X Parameters



The woofers are pretty close to the SBP15 from Lambda. They are slightly modified with a slightly longer coil and a little bit more mass, but very similar. I will put up some parameters for those shortly as well.

Lambda SBP15 Parameters



Mark should be coming up on Tuesday next week and we can get the DSP all setup and get these into the studio. I'll have more pics as everything is ready to get installed.

John

Nice work John ! Nice choice of drivers too !

I wish you good luck this time, I really hope it works for you this time. There's less competition in the market and we need you because you make quality stuff.

Mark Seaton arrived in GB today and the installation in Nick's studio has begun. The cabinets were finished with a textured Duratex black and a catalyzed polyurethane on the solid oak inserts. Both are quite durable and long lasting. The Duratex sands easily and is self priming, making finishing the MDF an easy process. Here are some pics of the empty cabinet with the oak inserts before driver installation.


This first one above is the top left monitor with the oak insert. This was a big pain in the butt to get all the angles correct for the coax to be aimed properly at the listening position. The oak took quite a bit of shaping and skill to be "bent" around the front angles.


This one is the subwoofer cabinet with oak insert. This was more straight forward. The holes are flared with a 1" x .5" gradual curve. The look is very smooth.

Then we put the drivers in. The 8" coax fits nicely in it's octagonal hole, aimed nicely at the listening position. The pair of TD10X's compliment nicely with their shiny phase plugs.



Then we layed everything out on the floor as it would be when installed in the wall. Mark brought the TEF with and began working on the crossover design, EQ, etc to get it setup before installation in the room. This is the whole right side on the floor looking from the bottom up. It looks pretty mean from this angle. These are not your typical everyday monitors.


Here is a closeup of the monitors. You can see the angles nicely in this one.


So after that, Mark stayed behind to work on the DSP on the one unit. Jason and I brought the other side to begin the installation at Nick's studio. Everything went nicely into the opening in the front wall of the studio. Cabinets were mounted in place and then the drivers were installed.





The final image here you can see the left side installed from just behind the seating position. More pictures to come tomorrow as the installation is finished.

John

Impressive as always John, looks like it involved a lot of hard work!

Very nice work and it looks like it's going to finish nicely.

I love the black contrasted with the oak.

Is that guy painting you?

The installation is nearing completion now. After a few minor setbacks working with the existing equipment in the room, we got things fired up and operational. Mark hooked up the TEF and began fine tuning the system in the room. I'll let him get on in the next day or so and post some details on the optimization of the system along with measurements. Here he is hard at work in the studio.



Here is a picture of the system fully optimized. I'll take one more from the listening position tomorrow. All in all, the system turned out incredible. The sound is just effortless throughout the entire bandwidth, all the way down to under 10hz in room. We'll find out in a few days when Nick returns how he feels about the system. I am sure he won't have any complaints.



John

just one final picture from the listening position, looking up slightly towards the monitors.



John

How does it fare having the left side crawling down the wall and the other one unloaded? Do you have any L/R bias from the wall?

What power amplifiers/processing are you using?

They look badass!

Is Nick a musician?

Chad