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Multi-Way Conventional loudspeakers with crossovers

Synergy horn for 135 dB+
Synergy horn for 135 dB+
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Old 30th March 2017, 04:06 PM   #11
Thijs666 is offline Thijs666  Netherlands
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Quote:
Originally Posted by nc535 View Post
HornResp is now up to version 40.30. You can simulate vented woofers as offset drivers on the horn without issue. You might not be able to do this when simulating it as a multiple entry horn but simulating woofers alone is not a problem
Damn, I must have been living under a rock or something. Totally missed that. Took a shot at it, but Iím not feeling confident I got it rightÖ

Click the image to open in full size.
(had to guess some T/S-parameters from the Beyma CP850Nd, so that's not accurate!)

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Click the image to open in full size.

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In factÖ Iím pretty sure I didnít get it correct :s.

I would be happier with something like this: (I hope I summed the vented OD horn correctly)

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Click the image to open in full size.

That would mean I would have to enlarge the vent holes from 39.10 cm2 to 120 cm2. So far for my simulation with WinISD .

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Originally Posted by nc535 View Post
You should take a look and see how closely your CD and woofers are time aligned. The best indication is probably the step response of the full range measurement but you should also look at an overlay of separate driver measurment IRs.

Jack
I tried letting my DCX2496 calculate the time alignment and it suggested to delay the CD by about 4 ms. I donít believe that would be correct. Below is the impulse response of the full system (from the second from last graph of my first post). Am I correct in reading a 20 microsecond delay on the woofer section?

Click the image to open in full size.
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Old 30th March 2017, 04:07 PM   #12
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by fluid View Post
How did you smooth the compression driver entrance it looks to be nicely done.
By hand .
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Old 30th March 2017, 04:10 PM   #13
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by weltersys View Post
Looks somewhat familiar...
Nice work!

Art
Thanks! And thank you for the Dixie cup idea
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Old 30th March 2017, 04:22 PM   #14
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by zettairyouiki View Post
Very nice! I was thinking about doing something almost exactly the same. I've got 4 12ndl76s and 2 Faital HF14ATs. My only concern is that the Faital CDs don't have enough low extension to meet the 12s at a reasonable point for a synergy design.
Thanks

That would be a concern indeed. I don't see a way to get those 12's playing any higher than you can see in the graphs above. They are literally up against the mounting plate of the CD. So you need a pretty beefy CD, hence I picked up the CP850 and I fear even this one isn't capable of keeping up. Distortion measurements will have to point that out.
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Old 30th March 2017, 04:34 PM   #15
nc535 is offline nc535
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120 sq cm is a pretty large hole but then they are large drivers. You might get a better answer if you simulate a shorter port length - equivalent to a thinner horn wall or frustrumizing the port. A shorter port should allow a smaller hole for the same velocity.

I should be the last one to give advice on time alignment since I struggled with it in my own design - but I might have learned something along the way. Using IIR DSP or passive filters, I believe you want the drivers aligned at the start of the IR. Using linear phase filters, you want the IR peaks aligned but if I recall correctly DCX does only IIRR filters. The IR peaks are easily determined. IR start can be fuzzy, especially if there is any pre-ringing, but you can judge start and then fine tune by trying to optimize the step - look for a sharp almost vertical initial rise followed by a ramp downwards to the right. What you have isn't bad; would look better zoomed in. Try small changes in delay and move in the direction that makes the initial rise of the step steeper.
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Old 30th March 2017, 05:17 PM   #16
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by nc535 View Post
120 sq cm is a pretty large hole but then they are large drivers. You might get a better answer if you simulate a shorter port length - equivalent to a thinner horn wall or frustrumizing the port. A shorter port should allow a smaller hole for the same velocity.
The measurements above are done with 4 vent holes of 65mm diameter.

3.25^2*pi = 33.18 cm2 ... *4=132.73 cm2; hmm, doh, I think I screwed up at least one hornresp sim by using only 33.10 for AP. But the sim for 33.18 measures up better to my measurements than the sim with 120 cm2

On the other hand, looking at Art's SyntTripPs, they also have quite generous vent holes...

Quote:
Originally Posted by nc535 View Post
I should be the last one to give advice on time alignment since I struggled with it in my own design - but I might have learned something along the way. Using IIR DSP or passive filters, I believe you want the drivers aligned at the start of the IR. Using linear phase filters, you want the IR peaks aligned but if I recall correctly DCX does only IIRR filters. The IR peaks are easily determined. IR start can be fuzzy, especially if there is any pre-ringing, but you can judge start and then fine tune by trying to optimize the step - look for a sharp almost vertical initial rise followed by a ramp downwards to the right. What you have isn't bad; would look better zoomed in. Try small changes in delay and move in the direction that makes the initial rise of the step steeper.
Zoomed in? REW doesn't let me zoom in any further on the time scale . For the record: I tried to estimate the delay between CD and woofers using my DCX2496, but that's the only thing I did with the DCX. All measurements are done with the passive crossover. So no DSP involved! That's what I'm aiming for.
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Old 30th March 2017, 05:23 PM   #17
nc535 is offline nc535
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Originally Posted by Thijs666 View Post
Zoomed in? REW doesn't let me zoom in any further on the time scale . For the record: I tried to estimate the delay between CD and woofers using my DCX2496, but that's the only thing I did with the DCX. All measurements are done with the passive crossover. So no DSP involved! That's what I'm aiming for.
Sure, REW will let you zoom in on an IR or IR overlay . Click on the "limits" button with the crossed double headed arrows and type in the time limits.
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Old 30th March 2017, 05:31 PM   #18
nc535 is offline nc535
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I admire anyone who can do a passive linear phase synergy xo even if I can't help thinking they have a masochistic streak

The art of passive XO synergy is choosing a port location that doesn't require any DSP or all pass filter delay for time alignment. So if this is just a proto build you should find the DSP delay you need for time alignment and then see if its within range of a port location change. I don't know if that can be done with a 12" woofer with the voice call so much further back from the horn wall than would be the case for the small mids usually used.
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Old 30th March 2017, 08:47 PM   #19
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by nc535 View Post
Sure, REW will let you zoom in on an IR or IR overlay . Click on the "limits" button with the crossed double headed arrows and type in the time limits.
It doesn't let me zoom in any further, even when I try like you said. It doesn't go under 1 ms for the full window. Maybe it's my measurement? Sweep length was 128k, the shortest REW allows.
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Old 30th March 2017, 09:16 PM   #20
Thijs666 is offline Thijs666  Netherlands
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Originally Posted by nc535 View Post
I admire anyone who can do a passive linear phase synergy xo even if I can't help thinking they have a masochistic streak

The art of passive XO synergy is choosing a port location that doesn't require any DSP or all pass filter delay for time alignment. So if this is just a proto build you should find the DSP delay you need for time alignment and then see if its within range of a port location change. I don't know if that can be done with a 12" woofer with the voice call so much further back from the horn wall than would be the case for the small mids usually used.
I still have to make that adapter for REW to be able to use a loopback as timing reference. I hope that will clear up the questions I have regarding the strange phase drop that occurs on axis around the xover point, but doesn't happen 10 cm off axis. Then, maybe I'll be able to determine the delay.

Also, the CD is behind a 2nd order filter, while the woofer has just a 1st order filter to attenuate the frequencies above the xover point (as you can see in the graphs, the woofer has quite some output up to 5 kHz. It's only about 10 dB down from the 200-Hz figure). The CD is also reverse connected. I could still go for a 3rd or 4th order filter on the CD...
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