Keith aka Amfibius System
 

Hi all, by way of introduction I thought I would post a few things about my system. The whole system has been evolved around my speakers, a pair of Acapella High Violon 2001's. This is what the system looks like now:

http://www.pbase.com/amfibius/image/...8/original.jpg

http://www.pbase.com/amfibius/image/...7/original.jpg

http://www.pbase.com/amfibius/image/...9/original.jpg

And the current list of electronics:

Source
- Playback Designs MPS-5
- Micro-Seiki BL-99V, Micro-Seiki MA-505 Mk.2, Lyra Dorian, RCM Sensor Prelude

Amplification
- Cary SLP-05 preamp
- Cary CAD-211AE power amp
- SGR EL30S power amp
- Marchand XM44 active crossover

Speakers
- Acapella High Violon 2001
- JL Audio F110 subwoofers x2

The journey with the system has been rather long and involved. When I bought the speakers in 2007, I identified the bass as being a problem. It was slow, muddy, and sounded wrong compared to the rest of the system. On the other hand, the midrange and top end were exceptional - clear, precise, full of timbre, and incredibly dynamic. At the time, I thought that it would be relatively easy to fix the bass.

So out went my CAD-805AE 50W SET, and in came the 110W CAD-211AE's. For the loss of some midrange magic and transparency came much better bass control and even better dynamics, but it still did not sound right.

The next step was to buy a pair of JL Audio subwoofers, and use an active crossover to remove bass frequencies before the power amp. This has a number of theoretically positive effects - it reduces woofer cone excursion, therefore reducing break-up modes. The amplifier is free from working with bass frequencies, giving more apparent amplifier power. The subwoofer can be placed optimally to produce the most linear bass. All in all, I nearly achieved my aims of cleaning up the bass AND the midbass while giving a useful boost in dynamics as well.

But I was still not happy. The measurements indicated that everything was nice and flat with hardly any F/R anomalies. I could not see what was wrong, but I could hear it.

The next step was to buy a SGR EL30S power amp and a DEQX. The idea was to provide seperate amplification for the midrange/tweeter via the Cary, with the SGR solid state amp looking after the bass cabinet, with the DEQX working as a digital crossover, but also with the ability to provide room correction, speaker correction, group delay, etc.

Sadly, despite my best efforts I could not get the DEQX to sound good. There is something about redigitizing the sound which is horribly destructive for resolution and dynamics. It is without doubt a powerful development tool, but not something I could leave in my system long term.

I used the DEQX to simulate ideal crossover points, then ordered a Marchand XM-44 crossover. This was MUCH better - so much more transparent. But despite all this, the bass was still not right. So we decided to open up the speaker to have a look.

http://www.pbase.com/amfibius/image/...9/original.jpg

As you can see, there is an internal woofer mounted at 45 degrees, firing into the back of the external woofer which is mounted on a baffle (not shown). Strangely, the internal woofer comes off the binding posts FULL RANGE, while the external woofer goes through the crossover. The crossover appears to be a 1st order low pass with a couple of notch filters in place. This bizarre arrangement was responsible for muddying up the bass!

At least I could see where they had spent the money. The construction of the cabinet is incredible - double ply, then lined with lead, then stuffing material.

The obvious step would be to disconnect and remove the internal woofer, and bypass the crossover so that the bass cabinet is fully active. By this stage I had complete independent control over each driver in my system, so it was a simple matter of adjusting the crossover and taking new sims with the DEQX to get it to sound right. The system gained another useful step in resolution, but there was something that was still nagging me.

http://www.pbase.com/amfibius/image/...1/original.jpg

This is a shot of the backside of the external woofer. It is a SEAS CA 25 ACA, which you and I can buy as a replacement part for USD$70-80. Note the shallow voice coil, the stamped metal basket, and the generally flimsy construction. The Xmax can't be more than 10mm! Another bizarre design choice - why put such cheap woofers on a speaker that retails for USD$60k, especially when you have gone through the effort of building an incredibly solid cabinet for it?

Warning - speaker vandalism ahead!!

All the while, I have been receiving help from SGR Audio, a speaker design company in Melbourne. They advised me that I had reached a dead end (and didn't I know that!). The only thing left to do is ... replace the woofer. I then did what no other Violon owner would do. I ordered a custom built high efficiency woofer to replace the stock drivers on the Violon. It would have to be of the same diameter and bolt pattern to ensure trouble free installation.

Here are a few comparison shots of the old and new woofers:

http://www.pbase.com/amfibius/image/...5/original.jpg
http://www.pbase.com/amfibius/image/...3/original.jpg

Arse end of both woofers. Note that the new woofer has a much more substantial build. The basket is cast steel and powdercoated, and the motor structure is bigger and deeper. Also note the cooling vent for the motor unit.

http://www.pbase.com/amfibius/image/...8/original.jpg
http://www.pbase.com/amfibius/image/...1/original.jpg

Front end of both woofers. I have to say that the new woofer looks quite sexy, even if it is going to be covered up in the end!

You may also have noticed that the new woofer is physically deeper than the old woofer. We immediately ran into a problem with the speaker cabinet. It contains a brace that secures the rear of the woofer. In fact, the woofer was glued to the speaker cabinet! To get it off, we had to tap it out with a hammer. So we had to do this:

http://www.pbase.com/amfibius/image/...5/original.jpg

By this stage, my heart was truly in my mouth. The sun was starting to set, and it was taking a VERY long time to mod the box given all the unexpected snags we kept running up against - hidden steel reinforcements, nails, and so on.

We got all the work done and replaced the speakers. Turned it on, did a few sweeps, and changed the crossover settings. We were ready to listen.

HOLY CRAP it's good! If you can imagine the power of a 300W solid state amp driving a high efficiency 8 Ohm woofer, with 110W of triode power running a high efficiency horn and tweeter - there is no shortage of power reserve. The speakers can go loud, loud, loud and even louder without a hint of strain. The dynamics of this thing are astonishing. The new driver goes about its business with a certain lightness and nimbleness, as opposed to the old driver which sounded heavy and plodding by comparison.

So after 4 years of development and thousands of dollars, I have finally reached the end of the road for the bass cabinet. When I bought my speakers, I thought that a change of amp would fix it - but it turned out to be more involved than that.

I then started to wonder what the horn would sound like if I removed its crossover :) The overall efficiency of the system is 92dB/W/m. Obviously, the horn is much more efficient than this so it HAD to be padded down to match the efficiency of the woofer. It should be a fairly simple matter to get at the internal crossover network, snip off a few wires, and then connect it directly to the Cary power amp, right?

WRONG!!! We manhandled the incredibly heavy horns off the box and I proceeded to undo the screws. The horn would not come off, so I thought it might be bolted in from the back. I undid the rear screw, only to be greeted by the sight of SAND pouring out the cabinet and onto my pristine living room rug made from genuine New Zealand lamb wool!! I quickly plugged the hole with my finger and replaced the bung (not easy when you have 40kg of horn cabinet on your lap!). Turns out the horn is screwed into the cabinet AND glued on. A sharp twist of the horn got it off, and this is what we saw:

http://www.pbase.com/amfibius/image/...0/original.jpg

http://www.pbase.com/amfibius/image/...1/original.jpg

http://www.pbase.com/amfibius/image/135560632/large.jpg

A Dynaudio D-52H midrange driver, customized for Acapella! Finally, a decent driver. The Thiel-Small parameters are here. Compare the F/R curve supplied by Dynaudio with my own measurement of the midrange horn F/R here. Obviously it looks different because it has the crossover in place and it is horn loaded.

After we drained all the sand out, we finally managed to get a good look at the horn crossover. It was sitting at the back of the box, covered in sand:

http://www.pbase.com/amfibius/image/...3/original.jpg

As expected, there are a few resistors to drop the efficiency of the horn to match the woofers. Check out the construction of the box:

http://www.pbase.com/amfibius/image/...4/original.jpg

As my friend said, it's very German in design. Only a bloody German would build a box out of double ply, then line it with lead. And then think to himself "hmm, maybe it's not dead enough. Let's fill it with sand!!".

Getting the sand back in is a simple procedure of using the fill hole at the back, like this:

http://www.pbase.com/amfibius/image/...5/original.jpg

Right now, I have almost reached the end of the road. All the major modifications to the system have been completed. Things left to do:

- Subwoofer upgrade. The subs now sound slow compared to the rest of the system. Considering a Wilson-Benesch Torus, but it is a little bit too spendy. Might get a pair of custom built subs instead.
- Refine the crossover settings. Will be running more sweeps and more sims over the next few weeks. With the Marchand XM44 it is a simple matter of ordering plug-in cards. At some point, I will send the unit for upgrades to the op-amps.
- Don't need the 110W Cary's to drive the midrange horns any more, considering these are 98dB/W/m sensitivity. Ridiculously overpowered. Will probably welcome back the 50W Cary SET's into my system, or try the Einstein OTL.

Well, that is my journey. Hope you enjoyed reading.

Keith,

I had a Violin Mk IV in my possession for a while. That tweeter is really something but the bass was a little lacking. The ion tweeter and its potential for harming my son (who tried to stick stuff in whilst on) meant it couldn't stay :tears:

Love your setup though.

howie

Thanks Howie. What did you do with your Mk.IV Violons? Is the owner still on AA?

I maintain the Acapella mailing list and would like to get in touch with him :)

Great pics, and descriptions of your quest. :thumbsup:

Sorry went to a 2nd hand dealer. The previous owner was King Jerry, the Meridian Supremo, Leben Supremo and all round aficionado! (JSCC). We did a complete swap of gear from Hong Kong to Singapore. Jerry got my Meridian set up and I got his Acapella, Jeff Rowland and PS Audio set up. :yes:

howie

Hi Keith,

You got mail .... :D

And I am no "King Jerry" as Howie puts it ... maybe a hifi "dunce" more like it. :yes:

Enjoy the forum. A lot of nice guys around.

Cheers!

Amfibius, thanks for sharing the story and pics! :thumbsup: You don't give up easy, do you? :D I used to build my own speakers and crossovers back in the day but I wouldn't have the guts to rip into a $60k speaker like you did. I would have also given up and went with a two way speaker or horns and augmented them through an active crossover and a fast, musical sub like JL Audio. In fact I experimented with that setup much to my surprise and outstanding results. :yes:

Of course you now have a truly unique setup and sounds like you have just about reached nirvana. :thumbsup: