Some More Questions On ELS Design

[fperra]

Looks like the large panels have a resonance of about 52 hz and the small one about 130 hz. The Behrenger DCX2496 crossover should be able to filter out these peaks. The response from all the panels is so smooth that I think I'll be able to use a 6 dB/octave crossover slope and set the crossover to somewhere between 600 and 1000 hz. What do you think? The other option is to use the oil burner transformers and set the ctossover to 48 dB/Octave at about 400 Hz. I guess I'll have to experiment once the frames are built and they are moved to my theater room.

[geraldfryjr]

Those Graphs look real nice I just did some more measurments today as well,and I got some really flat lines by placing the microphone about 2 to 4 inches from the speakers and running them fairly loud.
This helped a lot reduce the effect of the room reflections.

The phase response was flat at 85 degrees across the bandwidth too !!!

This helps to show that the accuracy of them was quite spot on and this was with the little woofer as well.

I used REQ V5 for thes tests and I would post the graphs for you but it doesn't have a export graphics function so I have to find my Screen capture program to do this.
I have them saved so I can do this later.

Measuring at a distance will show you exactly were the cancellations start to occur.
For my little panel this was about 600hz.


Being the nature of the panels being both ESL's I think that 6db slope should be good or even 12db.
But 12db to 24db may be in order to help with the low frequency saturation limits of the high frequency step up transformers.

Also to limit the high's going into to the oile burners because those will have a lot of extra capacitance and the high frequency's will cause a very low impedance to the amplifier.
Those may need even a higher slope.

I haven't spent a lot of time with the digital crossover setup yet because I have to setup my other machine as a source as the VST wave player I have works okay but I don't have a very good selection of quality samples setup yet.

So,I have been back to using the filters on my mixer for now and I have it tuned flat with little effort and except for the extreme lows, the bass sound location disappears from the two drivers and work in unison incredibly well.
Using this method the crossover falls at 1100Hz at about a 6db slope.

Some how I lucked out and that is the way it turned out.

Although I really like the lower crossover point as well the little woofer box is not tuned properly and is quite boomy.
I had to seal the port and pull out about 6db of 80hz and add everything I had at (15db) at around 40hz and this really tightened up the bass.
The only thing I do to the ESL is use a 80hz highpass cut and adjust the 12khz shelving to suit the material I am listening to at the time as the panel itself has a very flat response.

Bass is bass and the kick drum and the rest of the toms and snare have a very natural and clean snap.
Listening to the Cult's "Wild Flower" and Kiss's "Strutter" as well as The Hollies "Long Cool Women" the drums sounded like the were right here live in this room with no coloration or boomyness.
Not bad for a little 5.25" woofer in a now sealed box.

Anyway Great Job!!!
I can't wait to hear some more of your results as your panels are exactly what I have been contemplating should I finally build a bigger set.

I had just recieved as a gift a pair of 10" X 49" preforated metal that I think I will cut in half to do a pair of smaller bass panels and then add a tweeter section to use nearfield in front of my mixer.
And I am stiil going to do the tweeter/midrange strips for my big speakers aswell as this little panel proves that its width is in the proper range to complement them.

Its high frequency dispersion is not overly narrow and in some case not even noticeable very much.

You will know more once you get them into position.
As with mine sitting in front of my computer monitors I sometimes get some peaks in the 3khz to 6khz as well as a hump at 9khz to 20khz.
It becomes fatiguing at times and I have to pull those out with a filter as well.

I have discovered that my system is capable of transient peaks of at least 105db or more!

I have found that this response changes when I either move the speaker or my measurement microphone around.
So it is not the speakers as I have confirmed that with today's measurements.


Cheers !!!


jer

[fperra]

Another question. I keep hearing that electrostatics have to be equalized because they have a rising response with frequency. Yet, the response for my speakers I is essentially flat. Am I doing something wrong in my measurements? They were measured with the mic about 1' away from the center of the panels.

[bolserst]

Originally Posted by fperra

Another question. I keep hearing that electrostatics have to be equalized because they have a rising response with frequency. Yet, the response for my speakers I is essentially flat. Am I doing something wrong in my measurements? They were measured with the mic about 1' away from the center of the panels.

The natural near field response of an ESL is flat. It is the far field response that is rising.
1 ft. would certainly be considered closer to near field than far field.
Try listening to some music and start standing 1 ft. from them and slowly start backing away. You will notice the sound getting leaner and brighter the further you back away. Or, if you have the capability to take windowed measurements, measure the response at 1ft, 2ft, 4ft, 8ft and see the trend as you move out of the near field and into the far field.

Also, adding resistance in series with the primaries of your transformers flattening the rising response starting at a frequency determined by the value of the series resistance and the panel capacitance. You didn't post a schematic, but from the pictures it looks like you might have added some series resistance.

This post provides some further information on what other things influence the flattening of the natural rising response of an ESL:
Current vs voltage drive ESL?

[chinsettawong]

Here is the measurement from my 1.2 X 0.25 meter panel. I measure it near field with the microphone only about 2-3 inches from the panel. I always let my ESL run full range.

I think it all depends on what kind of music you listen to. For me, I really prefer mine this way and I don't use a subwoofer or EQ.



Wachara C.

[geraldfryjr]

Yes,
The first picture is the nearfield response(red line) as I had already posted at about 2 inches from the diagphram using my large diagphram Peavy 520TN microphone.
The hump at 4Khz is an irregularity in the response of this particular microphone.
The only EQ used on this test was a 80Hz highpass low cut filter to keep the transformers from saturating and as well as the low end change in response of the signal level as shown by the black kine

The next two charts are done with a calibrated Dayton measurement microphone and the db scale on the left is calibrated to a brand new SPL meter as well.
These measurements were done at a distance of 1 meter.
The second chart is the raw data of the combined woofer and ESL.

The third chart shows the woofer and ESL responses separately and as well as combined.
The only EQ that was used on the ESL was a 80Hz highpass low cut filter and about 4.5db cut using the a highpass shelving EQ at 12Khz.
The EQ for the woofer was the same as previously mentioned.

You can see the rising response of the ESL panel in these charts and is the reason for the high frequency cut needed to flatten out the response curve.

After this EQing they sounded much better and the fatiguing that I had been experiencing earlier had ceased.
Although I don't mind the little bit of the brightness at times.

jer

[geraldfryjr]

Here is some great must read material,

Elektrostatic Loudspeakers

Enjoy !!!

jer )

[fperra]

The project is on hold for the time being as I'm waiting for my new Laguna tools slot mortise machine to be shipped.
Regarding one of my prior post concerning the use of oil burner transformers for the bass panels, do you think they could be made to work up to 500 hz using equalization in the electronic crossover? The bass these put out is much stronger than the torroids. Here is a repost of the frequency responce of the bass panels driven by the oil burners:

[bolserst]

Originally Posted by fperra

Regarding one of my prior post concerning the use of oil burner transformers for the bass panels, do you think they could be made to work up to 500 hz using equalization in the electronic crossover? The bass these put out is much stronger than the torroids.

Can you clarify what you mean by the bass is stronger with the oil burner transformers?
Is the overall level higher? (ie is the step-up ratio higher) or is it that the oil burner transformers have more output below 50Hz. Most likely the reason the output for the toriods falls off more quickly below 50Hz is related to their low primary inductance and the amount of resistance you have in series with them. Can you post the schematic for how you have the toroids wired up, including the series resistance?

In any case, the slope of the oil burner response is nice and smooth. I see no reason why you couldn't include a complementary shelving filter in the electronic crossover. However, this would result in reduced headroom in this frequency range.

[fperra]

The step up of the oil burners transformers (2 of them per channel) with the primaries wired in parallel and the secondaries in series, and a 1.2 ohm resistor in series with one of the primary legs is 167:1. The step up of the toroids (4 per channel) with the primaries in parallel and a .25 ohm resistor on each primary leg (8 resistors in all) and one 1.3 ohm resistor feeding four of the parallel .25 resistors, is about 150:1. Listening to both, the oil burners sound much better in the low bass than the toroids. And measurements of the frequency response seem to back this up. Here is the response of the toroids, which shows a steep drop off after resonance.