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Old 16th April 2011, 11:25 PM   #31
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Dear Bear, Charles,

Indeed, large speakers as Acoustat give an image that few other speakers can reproduce. The price to pay is the quality of the electronics and of the cables before the speakers...

I read carefully your post.
- I had similar conclusion : my sub is a 46cm (18'') JBL in a 90L bass reflex. Amp is an Carver PM1.5, and the filter is the DCX2496, low pass 85Hz / 48 db. I use a lot of equ, due to two strong resonnancy, one at 30Hz (Fs of the speaker) and the other around 80-90 Hz.

- What can be new for you is the way I choosed to Low-cut the acoustat. I'm using since a week a Kaneda-type filter (picture). Caps is 200 nanofarad, resistors are 2x4,7Kohm. This avoid to use the DCX for the filtering of the electrostats.

First I have been deceived with such passive filters between the preamp and amp (see previous posts), but I found BIG improvement when using high grade resistors and caps (Styroflex/Takman). The difference using Styroflex caps is really tremendous compared to FKP/MKP ones. Cost is ridiculous, so it's worth testing.

The result is a very important increase of power handling (about 5-6db) ! Also music pieces such as big operas or film music (eg Hanz Zimmer classics) gains significantly in musicality and articulation. I assume that this is due to that the amps and eletrostats are working in better condition, and that there is less cross influence between the sub and electrostats.

BUT, the low-middle area becomes very dry, less 'smoth' as when the electrostats are working alone... I keep the two options, 'with' for 'big' music and 'without' for more intimate parts.


Awaiting your comments,
Mathieu
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Last edited by Acoustannoy; 16th April 2011 at 11:28 PM. Reason: orthograph...
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Old 17th April 2011, 01:25 AM   #32
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Quote:
Originally Posted by Acoustannoy View Post
3- adding two steps to the tension elevator ladder. The power handling is
improved together with dynamics : see curve 2 in comparison with the original curve 1 : the impulse answer is noticably higher. But the sound is more 'projected' in the medium area. Measurement curve 2 seems to confirm this, with a less flat response in the medium area.
=> What is your opinion ?
I have ML SL3 which have empty space on the bias supply board for two more rungs on the HV ladder, so should I.....? How do I decide?
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Old 20th April 2011, 06:16 PM   #33
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No reply...

Acoustat are very robust engines, so I did not had any fear to increase the HT value. For ML, I cannot give any guess...
Have you look into others sites on the web ?

Mathieu
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Old 21st April 2011, 07:00 AM   #34
Calvin is online now Calvin  Germany
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Hi,

its no matter of robustness but a matter of when the voltage gradient either in air or in the insulator becomes large enough that lowlevel ionisation and eventually flashovers occur. If the voltage gradient stress in a material gets larger, the process of ageing quickens.
So most panels Bias is set to a value with a good reserve to flashover treshold.
The thick insulating PVC-layer and the distance of membrane to stator-surface of the Acoustats allows and asks for high bias-voltages, but it does have the same issues with regard to voltage-gradients, added the problems of higher voltages generally.

jauu
Calvin
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Old 21st April 2011, 08:30 AM   #35
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Hi,

its no matter of robustness but a matter of when the voltage gradient either in air or in the insulator becomes large enough that lowlevel ionisation and eventually flashovers occur. If the voltage gradient stress in a material gets larger, the process of ageing quickens. ....
What exactly gets aged? The membrane coating?
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Old 21st April 2011, 09:42 AM   #36
DaveG is offline DaveG  United States
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Hey all- jumping in late here, and moving back a bunch of posts...in regards to biamping - I actually tried it. Did not cost anything, luckily.
1+1's, Medallion, HK Citation V for the high, old pooged Hafler DH200 for the bottom. Used a 10K Alps as level adjuster to bring down the Hafler level, and had to put a 8 ohm, 50 watt resistor across the high pass input...there are caps there, no ground return. Well, it lasted about 20 minutes. The blend in the middle was, for lack of a better word, yucky. The Hafler sound character completely over shadowed the HK and created some kind of new muck. Not distortion, it did "work" correctly. I was of course hoping for tighter bass with the smooth tube upper mid/highs like regular biamping, as that is a real weak spot using an under powered tube amp. I guess I could think it was the choice of amps that failed, but I think it is more than that. Something about the blend of characteristics that clash and with the huge range overlap, it happens in the worst spot in the midrange.
my 2 nickels worth...
Dave
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Old 21st April 2011, 04:10 PM   #37
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Quote:
Originally Posted by Andersonix View Post
What exactly gets aged? The membrane coating?
Ionization in the gap will slowly eat away at most conductive coatings. Some coatings are more robust that others. I have also been told that the polarity of the bias supply has an effect on the speed with which the ionization attacks the coating. In general though, prolonged use above the ionization threshold will eventually result in loss of conductivity across the diaphragm.

Ionization in the gap also weakens the dielectric strength of the PVC insulation over time. The insulation on the Acoustat wires is a bit thicker than most commonly available hook up wire. But with prolonged exposure to ionization, even it will eventually develop localized weak points in the insulation and arc.

Note that both of these failure modes occur only after considerable exposure to ionization from operating above the ionization threshold on a regular basis. The occasional high SPL party session will not significantly reduce the life span of an Acoustat panel.
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Old 9th November 2011, 04:22 PM   #38
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Originally Posted by Acoustannoy View Post
Dear Andy,
Nice to meet you on DIY.
Years ago, I carefully gathered your previous articles on the audio circuit together with J.Stickland releases. Now I found here on DIY many good advises. DIY is really one of the best Audio websites in the world !

Acoustats are still among the best speakers I've at home, they stay in my living room and I listen to them almost every day. It took long time before I found the right amplifiers for a decent price.
Now they are droven by a pair of Electrocompaniet AW180. One day, I will certainly switch for McIntosh, but this can wait : I'm quite happy with the Norway's amps.

Here I come to my questions, dear AcoustatAnswerMan !
I obtained sustantial sound improvement by :
1- choice of the cables and earth grinding -the Acoustat are extremly sensitive to the wiring-

2- changing the type of the C2 caps wich are directly connected to the pannels :
=> I tried WIMA caps ang obtained a smooth precise sound, but I was warned by our DIYcolleagues that the caps I choosed are too low in max tension. So I switched back to the original yellow ones.

3- adding two steps to the tension elevator ladder. The power handling is
improved together with dynamics : see curve 2 in comparison with the original curve 1 : the impulse answer is noticably higher. But the sound is more 'projected' in the medium area. Measurement curve 2 seems to confirm this, with a less flat response in the medium area.
=> What is your opinion ?

4- Adding a subwoofer in the very low area.
- The Sub is made of a JBL 15inch speaker with a carver PM1.5 amp and Behringer active filter. Works great from 20 to 60hz. Response curve is N3. not very flat but low freq. measurement is almost impossible. This improved the power handling and stereo at high levels, and gives a deep and dynamic bass.
BUT... until today I could not find a good hi-pass filter for the acoustats.. I tried actives one but the result is very poor, the sound is not so rich andtransparent. Then I switched to a simple condensator between the preamp and the amp. The result is better sounding, but the slope is only 6db/oct, and still not as natural as without any filter (see curve 4, without -blue- and with -red - 20 Nanofarad Cap).

=> What would be a good way to low-cut the Acoustats at about 40-50Hz with a 12db/oct slope ?
- Passive filter seems to me a logical solution but i'm peharps wrong. Where can I find good caps ?
- I hurd about Kaneda 12db passive filters but I have not any experience in this.
- Or should I go in the direction of a classical 12dB passive filter between the amps and the Acoustat ? What is the impedance to consider at 60 hz ?

I hope I don't ask too many questions in the same time,
Regards,
Mathieu
The making of a special pair of all steel frame Acoustat 1+1s modified by Jocelyn Jeanson of Kingsbury Quebec Canada.

Flickr: mracoustat's Photostream
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Old 10th November 2011, 07:20 AM   #39
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Default 1+1 Biamp...

Tanks all for your answers...i maled J.JEanson, I will give you further details when modifications are performed.

About Biamp of the Acoustat (more generally the MK121), I'm even surprised that is it possible. The two transformers have a common connection, and looking at the circuit drawing, I've got the feeling that they interact somewhat on each other.

Are the two channels (mid and high) really independant ?

Mathieu
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