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Multi-Way Conventional loudspeakers with crossovers

Amount of hornloading in a Synergy horn
Amount of hornloading in a Synergy horn
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Old 3rd June 2019, 10:52 PM   #11
Cask05 is offline Cask05  United States
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I'm currently using 0.5 ms delay on the woofer channel with the BMS 4592ND and Danley-style crossover filters (i.e., "fractional order")--no phase shifts through the crossovers. My woofer ports are about 4.5" in front of the horn throat. Crossover frequencies come out to 600 Hz and 5720 Hz.

Chris
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File Type: jpg K-402-MEH with BMS 4592ND and Crites Woofers Spectrogram.jpg (177.7 KB, 239 views)

Last edited by Cask05; 3rd June 2019 at 11:04 PM.
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Old 3rd June 2019, 11:46 PM   #12
mark100 is offline mark100  United States
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Hi Chris, color me dumb, but i have the same lack of understanding about your design, that i did with Droco's..

Do you have a synergy with multiple drivers sharing the same horn, or do you have two different horns aligned together?
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Old 3rd June 2019, 11:57 PM   #13
Cask05 is offline Cask05  United States
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See A K-402-Based Full-Range Multiple-Entry Horn - Technical/Modifications - The Klipsch Audio Community

The crossover filters I'm using changed about a month ago. I switched to the BMS 4592ND about a year ago.

Chris
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Old 4th June 2019, 07:15 PM   #14
mark100 is offline mark100  United States
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Quote:
Originally Posted by Cask05 View Post
See A K-402-Based Full-Range Multiple-Entry Horn - Technical/Modifications - The Klipsch Audio Community

The crossover filters I'm using changed about a month ago. I switched to the BMS 4592ND about a year ago.

Chris
Thx Chris, Great build, super thread.


I'm more puzzled than ever now, though, about the 1/4 WL woofer port to horn apex distance.
.....particularly with regard to the acoustic path length of the bms coax drivers.

As mentioned to Droco, I measure a 11cm fight time from the 4594's face to acoustic origin. And estimating the 4592's path length is likely a bit longer.

Because the 4594 driver is 7.9cm (3.1") deep,
and the 4592 is 11.3cm (4.5") deep.

Both use the exact same mid and high diaphragms.....
So I'm left thinking the 4592's acoustic path has to be at least 4.5" from the mounting flange.

I saw your woofer ports are 4.5" in front of the horn throat. Is that 4.5" in front of the 4592's mounting flange? Seems like it has to be.

If so, is your full port-to-horn apex length is at least 9" (22cm) ?
Which according to the 1/4 WL rule would need a crossover down a little below 400Hz?

I must be missing something, since it's working well for you at 600Hz.
Like I said earlier, I haven't been at this synergy math for very long..
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Old 4th June 2019, 09:15 PM   #15
Cask05 is offline Cask05  United States
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A half millisecond delay equates to 6.8 inches (17.25 cm) of misalignment. Subtracting 4.5 inches distance to the beginning of the off-axis ports in the horn leaves 2.3 inches (5.8 cm) from the 4592's mounting flange to its acoustic center at 600 Hz (room temperature)--instead of the 4.5 inches path length to some feature inside the driver. I surmise that mechanical path length to an internal feature of the driver isn't an accurate predictor of acoustic center.

Chris
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Old 4th June 2019, 09:29 PM   #16
mark100 is offline mark100  United States
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Hi Chris, the 11cm measurement is a timed acoustic measurement from the 4594's mid section to the mounting flange, not simply a mechanical path length estimate. It seems to me it is a very real addition to the 1/4WL path length ???? You might want to measure your 4592....my bet is the path length will surprise you...it sure did me ! Had to triple check..

(The HF section has about 0.06ms less acoustical path depth.)

Last edited by mark100; 4th June 2019 at 09:36 PM.
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Old 4th June 2019, 10:39 PM   #17
diyuser2010 is offline diyuser2010
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AES E-Library >> Effects of Acoustic Center Position in Subwoofers

While this paper is pertaining to subwoofers, the same concept applies. The actual acoustic center position is not an arbitrary location ( like the voice coil ) or diaphragm. Only acoustic measurement along with a full duplex sound card will accurately reveal the acoustic center in the far field.

Surprisingly in the paper, all of the methods used ( BEM simulation, spreadsheet prediction, near field scanning of the transducer, and an actual 2 microphone measurement ) placed the acoustic center almost a foot in front of the cabinet.

This can lead to errors in loudspeaker polar measurements if the center of rotation is not the actual acoustic center.

Another good read:

AES E-Library >> On the Movement of a Horn's Acoustic Center
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Old 4th June 2019, 10:48 PM   #18
Cask05 is offline Cask05  United States
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Quote:
Originally Posted by mark100 View Post
Hi Chris, the 11cm measurement is a timed acoustic measurement from the 4594's mid section to the mounting flange, not simply a mechanical path length estimate.
At 600 Hz?

Consider the group delay measurement (total, min phase, excess phase). There is a 450 Ás excess GD growth from 600 Hz to 20 kHz:

Chris

Last edited by Cask05; 4th June 2019 at 10:55 PM.
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Old 4th June 2019, 11:04 PM   #19
Patrick Bateman is offline Patrick Bateman  United States
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Quote:
Originally Posted by diyuser2010 View Post
This can lead to errors in loudspeaker polar measurements if the center of rotation is not the actual acoustic center.
MIND BLOWN

Up until two years ago, I measured at a distance of one meter. I doubled that to two, because Bill Waslo mentioned that was better. (IIRC, he didn't explain WHY.)

soon, I noticed that the beamwidth of my measurements was wider, even with the same waveguide.

Your link explains that then.
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Old 4th June 2019, 11:13 PM   #20
Cask05 is offline Cask05  United States
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A plot of the 4592 high diaphragm, mid diaphragm, and total K-402-MEH phase response, with the phase response of a SH-50 plotted for reference:

BMS 4592ND on K-402-MEH Phase (Green=Mid Diaph., Blue=HiHi Diaph., Red=Total MEH, Orange=Danley .jpg

Chris
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