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Geert - Hybrid ESL
Geert - Hybrid ESL
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Old 23rd September 2008, 04:28 PM   #21
Too Tall is offline Too Tall  United States
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Originally posted by Calvin

I liked LSP-Cad up to the 5.xx build since it was very intuitive in handling and the results seemed reasonable. It didn´t use a Spice-based simulator though. So the structure of the possible filter circuitry was restricted to simple ones (oh, how did I miss the bridged T-filter ). I have no experience with the 6.xx build
“apart from a quick handling test where it failed. “
What does that mean?

Originally posted by Calvin
Looks a bit too complicated to me. And since I concentrate rather on active speakers and have to work with Spice-simulators anyway, a ´real´ simulator proggy like LT´s works just finer for me
If you are used to LspCAD 5.xx going to Version 6 is a change at the root level. But once you know where things are you can make ANYTHING!!!
Well if we look at the movie “Real Science” that may be beyond it.
V6 works like a mathcad worksheet, so you just drag the parts on and wire them in any order you like.

It also has provisions to insert all the common filters such as 4th order LR, etc, along with templates of notches etc.
It easily handles from passive and active analog to digital and any combination. Once built you can listen to the filter through the speaker without physically building the xover.

Originally posted by Calvin
You may have been lucky here, because normally this is not the path to Endor Typical ESL-resonances peak at 10-20dB above normal level. Even with a filter of fourth order the crossover-freq should be placed no less than 2 octaves off the resonance freq to keep artifacts within the freq-response small enough. Since it is most often desired to have a lower crossover-freq, the demand for a linearization of the peak occurs. Besides the capability to shape the combined filter response of a 2nd order HP + notch (symmetric) its often sufficient to use a asymmetric Notch only, thereby reducing component count, filter structure complexity, size and cost!
It all depends on the panel.
My panel is 15”x 45” overall. It was built by Innersound (Roger Sanders) during the first year or two he went commercial. At some point he changed the Mylar coating and took all his stock and sold it to the DIY market through a friend. My friends and I bought 10 panels. I have four.

The frequency response is flat to 2kHz and then drops 3dB/octave.
At my xover frequency of 400Hz if is down about 9dB from the 2kHz plateau.

The resonance peak is dead on at 90Hz and is very narrow (80Hz to 100Hz). The peak is 6dB down from 2kHz.

Starting from 400Hz the 4th order high pass knocks it down 48dB.
I do not find it to be a problem I need to address with a notch filter.

If you go an octave lower with a xover point of 200Hz then you need to integrate it into the design

The impedance peak for the 90Hz resonance peak is around 90-ohms. (This is the change in impedance, not the actual impedance.)
This is a pimple on an elephant compared to the huge and wide impedance peak of near 800-ohms centered at 200Hz.
If you hope to use a passive filter you must address this and at that frequency the cap and inductor for the series resonance filter is VERY expensive!

Originally posted by Calvin
Since You talk about a fourth order passive filter here -which is a cacade of two standard second order filters-, I´m not sure if You got the point I wanted to make. The point is, to look at different than standard filter-blocks to find something that suits the desired correction- and filter response better, preferably even with lower parts count. In the special case of an ESL this means the need to correct for the Fs-peak (which isn´t adressed -but just attenuated- by a simple HP).

Calvin [/B]
Since we are talking about part counts restrict this to passive xovers for this point.
It all depends on the speaker, but I often go for 4th order ACOUSTIC as a target.
I am not sure if I am getting through on this point.
To have a 4th order ACOUSTIC response out of a driver I may end up using a 3rd or even 2nd order ELECTRICAL filter. If the driver is already dropping 12dB/octave I only need add a 12dB/Octave ELECTRICAL filter to get my 4th order ACOUSTIC roll off.
If the drivers have a huge overlap at the xover it could go down to a 1st order ELECTRICAL and that has happened, especially with a low pass on the woofer.

As often happens there may be bumps and holes and the phase response is not steady
This is where using 4 elements or more comes into play AT THE START.

The biggest advantage of starting with more parts is the filter response can articulate into a snake instead of a flat line so it can knock down peaks and fill holes. (Mostly knock down peaks)

I primarily work on pro cabinets with compression horns. The response is almost always crooked as a snake so having the ability to follow those curves is key.

Also you can take down a horn driver that is 20db hotter than your woofer and a big bite out of a 2kHz to 5kHz peak (from a CD-Horn) by changing the filter rather than doing it all with an L-pad and notch filter. You can get into serious heat issues.
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Old 24th September 2008, 07:08 AM   #22
Calvin is offline Calvin  Germany
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If you are used to LspCAD 5.xx going to Version 6 is a change at the root level. But once you know where things are you can make ANYTHING!!!
Well, I doubt ´ANYTHING´ ;-) What about the active parts of an active filter? Generic OP-models or real Spice-models? Are other than OP-based active filters simulatable? Then I might even take a second look at the thingie ;-)
The change at the root level is exactly what I disliked and that made a quick and intuituive start impossible. If I need a tool I need a tool that works for me. If I have to read a manual to know which side of the hammer is the head and which is the grip, that hammer is of no use to me ;-)
Anyway, this is getting offtopic....and as long as one has to discuss about the ´semantics´ of filter naming, discussions about the ´top10 of proggies´ is obsolete -at least for me.

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