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Multi-Way Conventional loudspeakers with crossovers

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Old 25th September 2018, 08:51 PM   #111
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Quote:
Originally Posted by KaffiMann View Post
I am fine with 2nd order bessel Mid/Tweet (Ref Rane if needed), Feel free to go crazy with (not too hard please, they can ring a bit) elliptical filters on Woofer/Mid. Just my 2c.

Paul!
Is it possible to move the port to the top of the enclosure? It really helps clean up the woofer response! Ref post 107. :-)
If you mean on the top panel and not on top of the front panel, it is ok.
Placing on top I should choose a rectangular port at the backside of the top panel.
Not on the top of the front panel, because it is an interruption of the tweeter baffle.
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Old 25th September 2018, 08:54 PM   #112
mbrennwa is offline mbrennwa  Switzerland
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Originally Posted by Paul Vancluysen View Post
I looked to this filter proposal. I think it is not possible to realize it with the 3 inch midrange.
Well, it is possible. I have done it with good results. See the link I included in my earlier post.[/QUOTE]

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Because of the low and high frequency fall of that driver with associated phase shift, especially at the low frequency side. Same remark for the low frequency part of the tweeter.
Not sure what you mean here.

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Originally Posted by Paul Vancluysen View Post
Which makes it difficult to realize a design which is fitting on targets.
"Something" can be made with these drivers for such concept, but not conform filter standards.

In general, first order filtering for tweeter and midrange affects the vertical polar diagram a lot. But ok, if it sounds good, what shall I say...
Question: what is more important -- polar diagram or time coherency?
I clearly prefer time coherent behaviour. Higher order filters separate single sounds into two sounds, which is confusing to my ears. For example, if you feed an impulse to to a first-order x-over, the result is still one impulse. With higher order filters, you'll get two impulses (one followed by the other).
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Old 25th September 2018, 09:12 PM   #113
freddi is offline freddi  United States
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for US drivers, I'd like to emulate the old Cerwin-Vega S-1 approach with 6th order assisted reflex. S1's EQ box had noticeable hiss. IIRC a Hafler DH200 would not drive it to xmax on the music of its time. Woofer qts should probably not be much above 0.31


http://i.imgur.com/Dkg8mPd.jpg
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Old 25th September 2018, 09:40 PM   #114
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Originally Posted by mbrennwa View Post
Well, it is possible. I have done it with good results. See the link I included in my earlier post.
Question: what is more important -- polar diagram or time coherency?
I clearly prefer time coherent behaviour. Higher order filters separate single sounds into two sounds, which is confusing to my ears. For example, if you feed an impulse to to a first-order x-over, the result is still one impulse. With higher order filters, you'll get two impulses (one followed by the other).
That is only valid for a perfect acoustical first order system.

The problem is that the drivers are too much different from each other in their overlap range to realize a good first order filtering and to realize the first order behavior.
How can you keep the phase difference 90 degrees between the drivers by adding a filter, if there is already a large phase difference between the unfiltered drivers.
Look in attach to the phase of the unfiltered tweeter and midrange. This phase difference is even worse taken the acoustical offsets between the drivers into account.

And in general for a first order system, moving in the vertical direction one driver gets delay to the other which affects the filter sum and also the timing a lot, in a very wide frequency range for a first order filter.

I don't find SPL curves in the link to show the first order filtering?
Attached Images
File Type: jpg SPL and phase of tweeter and midrange.JPG (149.9 KB, 240 views)

Last edited by Paul Vancluysen; 25th September 2018 at 09:51 PM.
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Old 26th September 2018, 07:04 AM   #115
KaffiMann is offline KaffiMann  Norway
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Quote:
Originally Posted by Paul Vancluysen View Post
If you mean on the top panel and not on top of the front panel, it is ok.
Placing on top I should choose a rectangular port at the backside of the top panel.
Not on the top of the front panel, because it is an interruption of the tweeter baffle.
Yes, I was afraid of that... Having the port on the back will also have negative effects on the performance.

I have to go to my "think box" for a bit to ponder this issue.
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Old 26th September 2018, 09:00 AM   #116
mbrennwa is offline mbrennwa  Switzerland
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Quote:
Originally Posted by Paul Vancluysen View Post
That is only valid for a perfect acoustical first order system.

The problem is that the drivers are too much different from each other in their overlap range to realize a good first order filtering and to realize the first order behavior.
I see you point -- however, it did work very well for my ATC-mid + Scan-tweeter system. I am currently on the go and I don't have the measurements with me. I will have to check next week when I am back.

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Originally Posted by Paul Vancluysen View Post
And in general for a first order system, moving in the vertical direction one driver gets delay to the other which affects the filter sum and also the timing a lot, in a very wide frequency range for a first order filter.
Yes. The question is where to put the compromise: good vertical lobing or good time-domain beahaviour. I prefer to get things right in the time domain.
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Old 26th September 2018, 10:09 AM   #117
KaffiMann is offline KaffiMann  Norway
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Why is it better to have the port far away? Would it be even better to have it on the rear?
It's not nessecerily "having the port far away" as much as: the current layout cause some resonances that might disturb the transition to the mid (especially so with "slack" filters, hard filters again cause other issues...), and make the xo process much harder than it needs to be.

Having the port on the rear will cause other issues at resonant frequency, as well as wastefully inducing room modes.

Edit:
Regarding filters: I really think a well implemented 2nd order Bessel topology will work nicely mid/tweet, please give it a try.

Edit2:
I may have a solution to the port issue, will look into it later tonight.

Edit3:
Will the tweeter vc be placed "back" a little when using a waveguide, so it is aligned with the mid vc?
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Last edited by KaffiMann; 26th September 2018 at 10:23 AM.
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Old 26th September 2018, 11:57 AM   #118
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Originally Posted by mbrennwa View Post
I see you point -- however, it did work very well for my ATC-mid + Scan-tweeter system. I am currently on the go and I don't have the measurements with me. I will have to check next week when I am back.
In the mean time I did find your design report in a link in the link.

At first look the ATC and the Scanspeak tweeter SPL have same slope in a wider frequency range, so the phase difference of the unfiltered drivers will be less.
But I see you have to set the tweeter in opposite phase also.

I don't wanna say that it is all bad and that the sound will not be ok, but it is not conform a first order filter.

I will do a trial again with the current concept.
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Old 26th September 2018, 12:29 PM   #119
Paul Vancluysen is offline Paul Vancluysen  Belgium
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I have made an LR4 filter 500 - 2500 Hz already to check some behavior, it is almost perfect on LR4 target.

The max SPL of this speaker concept is 112.5 dB at 1m above 40 Hz. So this is at maximum excursion of the woofer above 40Hz. Then the voltage on the speaker has to be 34 Vrms.
Below 40 Hz the excusion becomes higher (plot of it later).

At maximum SPL the maximum excursion of the midrange is 0.52 mm peak at 400 Hz. That is 50 % of its maximum linear excursion.

And at maximum SPL the maximum excursion of the tweeter is 116 um peak at 2500 Hz. That is 50 % of its maximum linear excursion.

A negative point of this LR4 filter at this time is a minimum impedance dip of only 3 Ohm at 38 Hz. I am afraid a serial resistance has to be placed with the first coil of the woofer filter, by using an air coil. Then I can get 4 Ohm as minimum impedance. What is the requirement concerning this minimum impedance value?
I expect that all filter concepts will have this problem.

In attach already some plots of SPL, SPL with targets, phase, power, impedance vs. Freq and schematic.
I had to make a comromise for the most flat SPL on axis and the most flat power vs. Freq.

Later more plots vs frequency of excursion, required amplifier power, off axis responses,... and more comments.

This LR4 filter is especially designed for a first check of the speaker behavior.
Later on we can make all kinds of filter concepts, maybe also with the final concept of drivers and cabinet.
Also digital filtering is an option. At this time I can design for miniDSP and Hypex platforms. And calculate biquad coefficients for orhers also.
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Old 26th September 2018, 02:15 PM   #120
mbrennwa is offline mbrennwa  Switzerland
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Will the tweeter vc be placed "back" a little when using a waveguide, so it is aligned with the mid vc?
Yes, a waveguide would introduce some set back of the tweeter. However, I am not sure which part of the drivers should be aligned. Voice coil, where it meets the dome/cone? The top of the dome? I guess this would need measurements to determine the acousic centres of the drivers.
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