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Multi-Way Conventional loudspeakers with crossovers

Freq measurements and Hypex Filter Design adjustments
Freq measurements and Hypex Filter Design adjustments
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Old 9th July 2019, 12:59 PM   #51
CharlieLaub is offline CharlieLaub  United States
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The measurements of the drivers (each operating alone) look fine.

The measurement of the "system" has some problems:
Click the image to open in full size.

The main problem with this measurement is that the resolution is too poor (300Hz or so) to really make out much of anything below 500Hz. In fact, you should ignore all the data below about 500Hz - it has nothing to do with reality and is in fact WRONG, despite the fact that your measuring program spits out some numbers for these frequencies. I explained this before.

Around 500Hz I would make a GUESS that the woofer and midrange are out of phase, and that the woofer level is too high, but the confidence I can assign to that is *maybe*.

I would try to reverse the phase of the woofer, drop the level by about 5dB, and take another "system" measurement. When you do that, use the same mic position that you used so far for the system measurement to do a measurement. Then try to place the mic on the floor (tip of mic touching the floor) at least 1.5m away and take another measurement. This will remove the "floor bounce" from the measurement, but you will be off axis. See if you can use a longer gated window with the floor measurement.

If you cannot get any better resolution on the "system" measurement there are some other ways to try and get better info but they are much more complicated and will involve a modeling program.
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Old 9th July 2019, 02:18 PM   #52
Steve2111 is offline Steve2111
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Default Freq measurements and Hypex Filter Design adjustments

Hi
I agree with wht you say about this "system" measurement, but I was only going to use it as tweeter measurement above 2KHz.
I also thought polarity should be changed between Woofer and Mid (because of the dip) although I was super careful with the wiring to get all the negs, negs and pos, pos.
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Old 10th July 2019, 07:37 AM   #53
YSDR is offline YSDR  Europe
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Quote:
Originally Posted by Steve2111 View Post
Hi
I agree with wht you say about this "system" measurement, but I was only going to use it as tweeter measurement above 2KHz.
I also thought polarity should be changed between Woofer and Mid (because of the dip) although I was super careful with the wiring to get all the negs, negs and pos, pos.
If you just flip the polarity of one driver in blind, it's possible to create an even larger dip in the response. First, one need to identify what causes the dip.

For example if the mid-driver have a natural 2nd order roll-off as we can see from the measurements, then a 4th order high-pass is applied, we get a 6th order roll-off. And if the woofer has a proper 4th order roll-off with the low-pass applied, then you have a roll-off mismatch and a dip in the response with good chance and no polarity flip can repair this problem.

That's why I suggest beginners to fatten the response first and then use the desired filter if we talking about a DSP based crossover. So that way you can be sure that the acoustical curves will follow tha applied crossover topology and you can easily experiment with other crossover frequencies and curves in the future.

Last edited by YSDR; 10th July 2019 at 07:47 AM.
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Old 10th July 2019, 07:55 AM   #54
YSDR is offline YSDR  Europe
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ATC uses a 4th order roll-off around 380Hz with their dome mid because this driver is strongly excursion limited in the low-end. So i don't suggest any lower crossover than this.
So don't overdo the response flattening to 20Hz. One octave from the crossover point is usually enough.
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Old 10th July 2019, 02:52 PM   #55
Steve2111 is offline Steve2111
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I will try the reverse polarity first to see what happens. 500hz crossover is in the middle of the overlap of woofer and mid. The woofer (without xover) slopes down well above 500 and Mid (without xover) slopes down well below the 500
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Old 21st July 2019, 07:12 PM   #56
Steve2111 is offline Steve2111
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Default Freq measurements and Hypex Filter Design adjustments

i would appreciate suggestions as to what filters to use (in Hypex Filter Designer) to flatten the freq response.

Image of Woofer24smoothLR4LR4: In this nearfield measurement, no xover is applied (although it is marked as red vertical line) and other drivers are muted.
Zone 1, how flatten from approx 60Hz to 20Hz?
Use Shelf or Asym Shelf and how apply/configure?
Zone 2 worth flattening?

Image of Mid24smoothLR4: This is nearfield midrange, rest muted. No crossovers applied though bandpass marked in red @ 500Hz & 2KHz.
Zone 3 worth flattening?

Image of Farfield: Farfield of course. Reliable down to 300Hz? No speaker muted. LR4 crossovers applied @ 500Hz & 2KHz.
Mainly for tweeter assessment.
Zone 5 from 10K or 12K, can this be levelled? What filter use?
Zone 4 I presume Boost/Cut @ approx 3.5KHz but don't know what Q?
Zone 6, Dip between Mid and Woofer. CharlieL suggests change woofer polarity as could be out of phase and freqs cancelled. If polarity change fixes dip, fine. If dip increases it's something else. Could be natural down slope of both drivers at xover freq. Deniberi recommended flattening responses before applying xovers. CharlieL suggests reducing the gain on the woofer. I will do that when I have applied all the other filters.
If I master that lot, will deal with PHASE.
Attached Images
File Type: jpg Woofer24smoothLR4LR4.jpg (464.1 KB, 138 views)
File Type: jpg Mid24smoothLR4.jpg (455.3 KB, 132 views)
File Type: jpg Farfield.jpg (685.6 KB, 131 views)
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Old 21st July 2019, 07:56 PM   #57
YSDR is offline YSDR  Europe
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Ok, i suggested the response flattening but something may not clear.

1. Leave the woofer's low-end response alone until you measure the farfield response at the listening spot.

2. The flattening is important in the pass-band and at least 1 octave below and above from the crossover points for LR4 slopes.

3. What Q you need is dictated by the driver response anomalies. Q is the working frequency width of a filter. You need experiment here, try different Q-s for best response. For example: a sharp change in the driver response needs a higher Q filter to counteract.

Last edited by YSDR; 21st July 2019 at 07:58 PM.
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Old 21st July 2019, 08:48 PM   #58
CharlieLaub is offline CharlieLaub  United States
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Quote:
Originally Posted by denibeni View Post
Ok, i suggested the response flattening but something may not clear.

1. Leave the woofer's low-end response alone until you measure the farfield response at the listening spot.
He can't do that. The speakers have been built into a wall and the room is not large. The farfield response is contaminated by reflections off of room surfaces below about 350-500Hz, and that is also the resolution for the rest of the audio spectrum for any far-field measurements.

The only solution is to use a near-field measurement on the woofer and assume that, because the speaker is built into the wall, there is no baffle step. At least I feel that would be a good first order approximation that one could make in this situation.
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Old 21st July 2019, 08:55 PM   #59
YSDR is offline YSDR  Europe
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Quote:
Originally Posted by CharlieLaub View Post
He can't do that. The speakers have been built into a wall and the room is not large. The farfield response is contaminated by reflections off of room surfaces below about 350-500Hz, and that is also the resolution for the rest of the audio spectrum for any far-field measurements.

The only solution is to use a near-field measurement on the woofer and assume that, because the speaker is built into the wall, there is no baffle step. At least I feel that would be a good first order approximation that one could make in this situation.
I mean non-gated farfield response. How you want to tame room modes with a gated response?
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Old 21st July 2019, 09:16 PM   #60
YSDR is offline YSDR  Europe
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Woofers mounted in the wall means significant room gain to the low-end response if the room is not exceptionally large. Baffle step loss os not playing here ofc.
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