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Quad 63 (and later) Delay Line Inductors
Quad 63 (and later) Delay Line Inductors
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Old 3rd June 2021, 10:23 PM   #371
Hans Polak is online now Hans Polak  Netherlands
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Thank you Steve.
I’ll try to implement that tomorrow.

Hans
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Old 4th June 2021, 10:11 AM   #372
Hans Polak is online now Hans Polak  Netherlands
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Here are the results for 1) Rpar=300K, K=0.3 and K=0.1 and 2) Rpar=2Meg, K=0.3 and K=0.1.

First image shows Jan's Bode diagram in Brown and on top of that 1) in Green and 2) in Purple.
Ripples at HF are now clearly visible as a prove that Rpar = 300K is too low when having added the coupling between the coils.

Second image shows the FR with my original live recording in Cyan, with on top 1) in Red and 2) in Blue.

Hans
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File Type: png Bode Rpar 2M +K 0.3 + K 0.1.png (66.8 KB, 128 views)
File Type: jpg Rpar 2M+K 0.3+K 0.1.jpg (455.1 KB, 120 views)
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Old 4th June 2021, 10:46 AM   #373
jan.didden is offline jan.didden  Europe
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That's indeed a big step forward, thanks Hans!

Jan
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Old 4th June 2021, 01:44 PM   #374
orjan is online now orjan  Sweden
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I have to admit that I haven't read the whole thread but I think the transformers leakage inductance has not been included in the sims.

/örjan
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Old 5th June 2021, 07:04 AM   #375
Hans Polak is online now Hans Polak  Netherlands
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Are you asking or telling?

Hans
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Old 6th June 2021, 08:50 AM   #376
jan.didden is offline jan.didden  Europe
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Did some more work today towards the direct drive amp, to equalize the response to match the original speaker. Ordered a miniDSP 2x4DH as a front end, because: 1) both analog and digital inputs for experimentation, 2) provides inverted outputs to drive both panels of a speaker in opposite phase, 3) rich menu of filters and EQ.
The nice thing is that it allows calculation of filter coefficients in REW and then download those into the miniDSP.

Step 1: take the xformer freq response and manipulate the data to 1) normalize at 0dBV @ 100Hz; EQ for the probe droop; invert it so that any filtering can be done by decreasing level to avoid unintended overload.
The resulting curve, loaded in REW is attachment 1. This is the inverted shape of what I posted earlier.

Step 2: setup REW to turn this into a flat response, normalized at 100Hz, using 8 FIR filters. The result is attachment 2. The response is flat within +/-0.2dB except at the top. I probably will roll that top of with an additional filter.

Finally, the filter settings as they need to be downloaded to the miniDSP as biquad coefficients.

All in all, not a bad result for a Sunday mornings work ;-)

Jan

PS example: 1st filter coefficients set:
biquad1,
b0=0.9974735606763722,
b1=-1.9724031392342314,
b2=0.9755301654455323,
a1=1.9724031392342314,
a2=-0.9730037261219044,
Attached Images
File Type: png reg invert norm eq xformer in rew.PNG (62.4 KB, 85 views)
File Type: png reg invert norm eq xformer & target in rew.PNG (72.8 KB, 77 views)
File Type: png filter coefficients.PNG (29.7 KB, 76 views)

Last edited by jan.didden; 6th June 2021 at 09:18 AM.
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Old 6th June 2021, 03:18 PM   #377
Hans Polak is online now Hans Polak  Netherlands
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Hi Jan,
Great result.
Have you planned to record the sound on axis with a microphone ?
That would be the final prove of the pudding.

Hans
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Old 6th June 2021, 04:52 PM   #378
jan.didden is offline jan.didden  Europe
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Hi Hans, yes I might do that. But so far I only have one channel working. I want to get a second one running so I can drive the speaker properly. Many parts and PCBs on the way ;-)

Jan
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Old 6th June 2021, 07:50 PM   #379
bolserst is offline bolserst  United States
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Quad 63 (and later) Delay Line Inductors
Quote:
Originally Posted by jan.didden View Post
...Step 1: take the xformer freq response and manipulate the data to 1) normalize at 0dBV @ 100Hz; EQ for the probe droop; invert it so that any filtering can be done by decreasing level to avoid unintended overload.
The resulting curve, loaded in REW is attachment 1. This is the inverted shape of what I posted earlier.
Comparing with your earlier data from Post #350, this curve doesn't match either the pre or post probe droop compensation. Any idea what the difference is?

The miniDSP 2x4HD is a great tool to work with.
It also has FIR capability if Bi-quads get too cumbersome.
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File Type: png EQcurve_compare.png (137.0 KB, 22 views)
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Old 6th June 2021, 08:58 PM   #380
jan.didden is offline jan.didden  Europe
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Yes there seems to be a difference. In this case, I applied the probe EQ after the measurement rather than to the source level, I have to see if that has introduced an error.
Anyway I was quite preoccupied with the whole procedure so I may have overlooked something. I will need to go through the whole thing again in detail, now I have figured out the process.

If you think about it, the tools and software we now have available to us, even not being professionals, were unheard of a couple of decades ago. And then realize that Peter Walker designed this speaker without them. Amazing.

Jan
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