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Old 1st October 2013, 03:54 AM   #331
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Quote:
Originally Posted by gootee View Post
Well that is turning out to be an odd one...Some change I made must have caused something pathological in my schematic.
Any luck tracking down the odd issue with your Triple EF output circuit?
Thanks again for posting the LTspice files for others to play with.

I started working with your Simple-Source file last night. I'd like to better understand the tweeter response differences when bi-wiring vs single wiring. Most result directly from the woofer current producing a voltage drop/increment in the single wire, but the differences at higher frequencies appear to include other effects as well. I also still need to wrap my head around the distortion effects you have been posting...

I noticed you started using the voltage applied to the drivers for comparisons as SY had suggested back in post#217. This reminded me that I was going to look up what the voltage across the motional impedance parts represented. This voltage(Vtweet in your LTspice models) is analogous to the voice coil or cone velocity. Multiplying this voltage by frequency to get cone acceleration and you would have an output signal proportional to the far field on-axis response of a perfectly ridged piston. As an example, I plotted the velocity and on-axis response for your tweeter with and without the crossover components.

Response is normalized to 0dB as shown for input voltage = 2*pi*Cmes*Revc
If more than one driver is used and you want to plot relative response levels between the drivers, you would need to include the effects of motor strength(BL) and cone area(Sd).
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File Type: jpg Twt_response_model.jpg (113.1 KB, 105 views)
File Type: jpg LS_model.jpg (43.9 KB, 105 views)
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Old 1st October 2013, 08:53 AM   #332
tinitus is offline tinitus  Europe
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btw, or another very simple way of looking at it
and far from this impressive scientific detective work

either it makes no difference, and as such pointless

or if it really made a difference then speaker function have been changed
not so wise, considering it was designed to work properly 'as is'

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Old 2nd October 2013, 03:12 AM   #333
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What???
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Old 3rd October 2013, 03:03 AM   #334
gootee is offline gootee  United States
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Quote:
Originally Posted by bolserst View Post
Any luck tracking down the odd issue with your Triple EF output circuit?
Thanks again for posting the LTspice files for others to play with.

I started working with your Simple-Source file last night. I'd like to better understand the tweeter response differences when bi-wiring vs single wiring. Most result directly from the woofer current producing a voltage drop/increment in the single wire, but the differences at higher frequencies appear to include other effects as well. I also still need to wrap my head around the distortion effects you have been posting...

I noticed you started using the voltage applied to the drivers for comparisons as SY had suggested back in post#217. This reminded me that I was going to look up what the voltage across the motional impedance parts represented. This voltage(Vtweet in your LTspice models) is analogous to the voice coil or cone velocity. Multiplying this voltage by frequency to get cone acceleration and you would have an output signal proportional to the far field on-axis response of a perfectly ridged piston. As an example, I plotted the velocity and on-axis response for your tweeter with and without the crossover components.

Response is normalized to 0dB as shown for input voltage = 2*pi*Cmes*Revc
If more than one driver is used and you want to plot relative response levels between the drivers, you would need to include the effects of motor strength(BL) and cone area(Sd).

I haven't had any time to go back and try to track down the problem with that simulation.

For the attached. I am not at all sure that I have correctly multiplied by frequency. I have not used Laplace voltage-controlled voltage sources very much, and never routinely.

Attached are some plots, and the schematic and LT-Spice .asc file that produced them. (Remove the .txt from the .asc file name, before running it with LT-Spice.)

Cheers,

Tom
Attached Images
File Type: jpg bw_x_s.jpg (436.0 KB, 70 views)
File Type: jpg bw_x_s_13ft.jpg (401.8 KB, 68 views)
File Type: jpg bw_x_s_schem.jpg (256.1 KB, 67 views)
Attached Files
File Type: txt BI-WIRING2f_no_amp_TIMES_FREQ_gives_acceleration.asc.txt (16.3 KB, 2 views)
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Old 3rd October 2013, 02:34 PM   #335
KSTR is offline KSTR  Germany
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Tom,
the distortion results from the file in post 312 look like simulator residual to me. Changing some options like ".opt numdgt=15" and decreasing tolerance settings yields all 4Z values (0.000x). That what is left is either the noise floor limit (when it doesn't change with sim time length) or L's and C's still settling from the very non-sinusoidal beginning of the test signal, then you simply have to wait longer until it dives down into the noise.
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Old 3rd October 2013, 03:45 PM   #336
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Quote:
Originally Posted by KSTR View Post
Tom,
the distortion results from the file in post 312 look like simulator residual to me. Changing some options like ".opt numdgt=15" and decreasing tolerance settings yields all 4Z values (0.000x). That what is left is either the noise floor limit (when it doesn't change with sim time length) or L's and C's still settling from the very non-sinusoidal beginning of the test signal, then you simply have to wait longer until it dives down into the noise.
aha.... like music.

The test design I mentioned awhile back allows for the use of a non steady state signal to notice the mono to biwire difference...just drive the amp with an ipod...and scope the diff.

jn
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Old 3rd October 2013, 06:19 PM   #337
KSTR is offline KSTR  Germany
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Er, I was just pointing out that THD/HD simulations of linear circuits -- besides questioning the usefulness of this in general -- in ppm territory are often plagued (dominated) by time constants that can be misleading (when you sim with real amplifier circuits rather than ideal sources). When you start a sine abruptly (rectangular window) we have a wide-band signal that needs to settle when passing through RLC networks. If you FFT a single period too early in time there will still be some settling tail polluting the result.

Last edited by KSTR; 3rd October 2013 at 06:26 PM. Reason: expanding the point
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Old 3rd October 2013, 06:25 PM   #338
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Originally Posted by KSTR View Post
Er, I was just pointing out that simulations in ppm territory are often plagued (dominated) by time constants that can be misleading. When you start a sine abruptly (rectangular window) we have a wide-band signal that needs to settle when passing through RLC networks.
Absolutely. You point out a good issue with simulation. I had this issue in 2005 when I also did the bi to mono sims that are being repeated here.

That's why the hardware test is so important.

Pano man, where are you?

jn
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Old 4th October 2013, 12:17 AM   #339
gootee is offline gootee  United States
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Yes, you are both right. I was pretty familiar with those kinds of THD artifacts and effects, back when I did a lot of simulating, and eventually realized it, in this case, and then almost mentioned it, except I have been extremely short of time for at least the last week.

So, jneutron, is my setup what you envisioned, so that it might be useful to pump some music through my simulation, or maybe something like square waves? I guess I would just need to add one more ideal difference amplifier, to see the difference between the outputs of the first two difference amplifiers? (Actually, I guess I was already doing that, with waveform arithmetic.)
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Last edited by gootee; 4th October 2013 at 12:21 AM.
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Old 4th October 2013, 03:53 AM   #340
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Quote:
Originally Posted by gootee View Post
For the attached. I am not at all sure that I have correctly multiplied by frequency. I have not used Laplace voltage-controlled voltage sources very much, and never routinely.
Huh...I'd never considered handling it that way, but looks to give the correct result.
I usually just use the expression editor to multiply by frequency as shown in attached plot.
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