AccuPulse Rears

Thanks to Tom, one of my best friends and also one of the owners and director of Halwema, one of the largest woodwork and aluminum machinery suppliers in Belgium, I was able start this new project.

Now that my AccuPulse Front speakers where finished the need arose to build a matching pair of rear  speakers that would match the front speakers. 
Of course in order to have a compatible sound quality, and simply because there is no better alternative on the world, the choice for the mid/high unit was fixed in advance. It will again be the sublime Manger MSW. After finishing the AccuPulse and listening to them for an extensive period of time now and also having heard, thanks to the kindness of Sammy from one of the top high end shops in Belgium Alpha  , the world finest commercial speakers (like the Avalon Eidlon Diamond from which I think it is one of the best speaker in the world, or the Audio Physic Kronos which I do not like at all or the Dynaudio Evidence Master about which I am not thrilled either). I became even more convinced that the Manger MSW, when correctly used is a masterpiece but, as mentioned so often, one should permit oneself some listing time to dis-learn the errors the conventional speakers make and which most of us have been brainwashed to accepted as the right way to reproduce sound (But which of course in not true) and as everything in this world (especially divas as the MSW) it is not perfect and has it shortcomings too.


This website illustrates the different steps in the construction of these new speakers.

Ready, OK Here we go.

 

Spraying the glue 

As I wanted to make the new speakers also out of a sandwich consisting of three different layers.
13mm of Phenol Resin (HPL from Resopal) 16mm of MDF and on top a layer of 3mm called SSV from Wilsonart (it is the same stuff as Corian, an aluminum oxide filled acrylate). 
So we started of gluing whole boards of the the three composite layers together.
The special glue we used Sealbond (from Novation), which forms an viscous elastic thin layer between the boards, is sprayed on the boards. 

 

The sandwich in the press 

After Spraying the glue the HPL and MDF boards where put in the press where they where bounded with several tons of pressure.
After this the whole process was repeated to finish the three layer sandwich with a Corian layer.

 

Cutting the boards 

Once dried the sandwich boards where cut to the approximate size using a huge numeric panel saw.

 

Panel saw

Here you get an idea of what large means, and this is not even the biggest one.

 

Stack of precut panels

So now that we have our boards cut up we can start processing them on the CNC.
The stack you see here is for 2 pairs.

 

Making the inner cabinet parts

But first we have to make the smaller parts which will be used for the inner cabinet.
Here we are making a 30 degree edge for a panel that will be used as separation between the Manger and the woofer compartment.

 

The Altendorf panel saw

For this we used one of the best panel saws available in the world.
A numerically controlled Altendorf.

 

The Weeke CNC

So now we are ready to mil the precut parts on the Weeke CNC
As you can see we utilized not the smallest one available, not really build for the fainted one among us.

 

The Sleeves

First we milled the sleeves and the trapped contours of the panels.

 

The Speaker holes

Then we made the speaker wholes. Here we just catch'ed the CNC changing tools.
First it used a rough mill and it is now just changing to a fine one to finish off the job.

 

Finished front panels

This is the stack of the four finished front panels.
The center of the speaker holes is still attached by a very thin layer of HPL to the body of the front panel.

 

Removing the rest

This is a finished front panel. I was just removing what is left of the speaker hole.

 

Finished panels

Here is the stack of finished panels.

 

Trapped detail

You can see how the borders of the panels are trapped.
The wholes you see accept join rods which will assure perfect fit of the panels when assembled.

 

Test assembly

Time to see if everything fits as planned.
Therefore we assemble the whole cabinet but without any glue.
Seems we where lucky again this time.

 

Pressing the cabinet

Now for the real work. After glueing the parts. The cabinet is put in the corpus press.
To apply the glue is a job of its own. There are three different glue's used in the assembly.
First the MDF parts are glue'ed with normal white wood glue.
The HPL parts use a special two component glue Novabound 2, (from Novation),
The third glue used to bound the Corian parts and which is also a two component glue but this time acryl based.
As the two last mentioned two component glues have an open time of 15 minutes we had to rush like hell to finish before curing started.


Details of the speaker holes

Here you can see some detail of cut out for the Manger as well as for the Scan Speaks.
The reinforcements in the cabinet are also distinguishable.

So here are our two pairs

The cabinets are nearly finished. We have just milled a 45 degree angle on all the sides.
Now we just have to polish them, but we will postpone that task till we installed the lining in cabinet,
mounted the drivers and finished the measurements on the filter less mounted speakers.


Up in the air

We used a fork lift to place the speaker as far as possible from any (reflecting) surfaces,
this way our
maximum length sequence analysis would be valid to as low a frequency as possible.


The measurement microphone.

I use a Earthworks Measurement Microphone  with the DAAS32 system.


The master (Hmm?1) at work

To have as little influence from the computer noise as possible I placed the DAAS32 computer controlled measuring equipment
as far away as possible from the setup. Don't look at the cable spaghetti, I know i should have cleaned it up a little bit for the show.


The polishing specialist at work (what are brother in-laws good for)

Now the time comes to start polishing. We opted for a medium high gloss polish.
We started of with a 180 grain then continued with a 220, 320, 400, 800 and finally finished with a 1200 grain polishing paper.
This resulted in a very natural stone look.
In the bottom you can also see the inserts for the spikes.


The result after the 6 steps

It takes approximately 6 hours to polish one cabinet.


This is what it looks like once mounted


Looked at from the side you get a better idea of the polish


Here is a close up, I left the finished pictures in a relative high resolution
so sorry for you guys who are still using a conventional modem


And here you have them both, admit not bad for a couple of self made rear speakers.


 


The VP300D from Sitronik Industrie.

I wanted to make these speakers active but due to lack of time I decided to leave the job to a firm who specializes in speaker amplification and filters.
I used the high tech modules from SITRONIKINDUSTRIE.
Here you see their VP 300D which I used for the low end. I took the 750VA version, it delivers huge 350Watt in 4 Ohm.
The unit also has a digital filter which not only includes crossover function with selection of different slopes and cross over frequency,
but also has contains a set of extremely useful set of parametric equalizers to easily compensate for any deficiencies of the speaker and or listening room.
This unit is completely controllable using the standard included remote control and display and there is an even more
comfortable graphic windows application included which makes it even more fun to operate.
The engineers at Sitronik where so friendly to modified the upper limit of the crossover frequency from 200Hz to 500Hz.
This now makes this module also usable in active speaker and not only as a subwoofer amplifier.
I must admit that I was very astonished about the really professional build quality of all there modules.
So it is not very surprising that Sitronik also manufactures the electronics for the speaker of some some very renowned speaker companies.


Here a look on the digital filter (DSP and A/D D/A converters) of the VP300D


Here the VP102 which I used in bridge to drive the Manger MSW

Here you see their VP 102 which I used to drive the MSW.
The module can be used both as stereo or 2 channel amplifier delivering 2x90 Watt in 4 Ohm but I use it in bridged mode.
In the bridged mode It delivers 180 Watt in 8 Ohm.
There is a separate circuit board which handles both symmetric and asymmetric input
and also includes the possibility to configure some basic first or second order filter.
I am not using the filter on this unit.

Here a closer look on the amplifier electronics of the VP102.

As you can see the VP102 uses a couple of integrated circuits for the amplification.
This makes the whole circuit very compact.
Using such circuits may seem a little weird in a good quality amplifier but remember that even companies as Linn
use these kind of circuits in there famous and extremely expensive amplifier.

 

 

 

A prototype

Of course before we started with the real cabinets described above I made two prototypes on which I did measurements to verify my calculation and presumptions.
The internal volume for the woofers of the first prototype was a bit to small so I had to make a second one after correcting the dimensions,
Here you see the first prototype with the two Scan Speak 18W8531G00 mounted.

The Scan Speak 18W8531G00

 

 

Last Modified 07/06/2006

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