Has anyone used 1st order HP & LP filters together with different -3dB frequencies so that when the cross over point of the amplitudes meet they are -6dB down instead of 3dB.
If my mental calulations are correct the HP will be set for 600Hz and the LP set for 150Hz. The crossver point will be 300Hz@-6dB.
This will mean that different values of the caps and resisters (active XO) for the HP & LP will be used. This will mean some compromises but hopefully they wont be as bad as those of a higher order filter.
Has anyone tried this? and did it work or was it a disaster.
Kind regards
Primalsea
Dont settle for shampoo, Demand real poo!!
If my mental calulations are correct the HP will be set for 600Hz and the LP set for 150Hz. The crossver point will be 300Hz@-6dB.
This will mean that different values of the caps and resisters (active XO) for the HP & LP will be used. This will mean some compromises but hopefully they wont be as bad as those of a higher order filter.
Has anyone tried this? and did it work or was it a disaster.
Kind regards
Primalsea
Dont settle for shampoo, Demand real poo!!
Sorry I should have said.
As 1st order filters have a gentle roll off I'm concerned that they may not be suitable for my intended speakers as the attenuation outside the cross over point may not be enough. I dont want the drivers operating outside of their most linear frequency range. I understand this is the time old problem with 1st order filters.
However if the overlap frequency of the xo was -6dB down, like that of a Linkwitz-Riley filter there will be more attenuation of frequencies outside of the xo frequency. This, I hope will give some extra margin.
I foresee that there may be some issues with how the xo and drivers responses sum but not sure at the moment.
As 1st order filters have a gentle roll off I'm concerned that they may not be suitable for my intended speakers as the attenuation outside the cross over point may not be enough. I dont want the drivers operating outside of their most linear frequency range. I understand this is the time old problem with 1st order filters.
However if the overlap frequency of the xo was -6dB down, like that of a Linkwitz-Riley filter there will be more attenuation of frequencies outside of the xo frequency. This, I hope will give some extra margin.
I foresee that there may be some issues with how the xo and drivers responses sum but not sure at the moment.
Looking at the crossover alone you will end up with a dip in the FR.
Depending on the natural rolloff of the drivers you can make it work. Some Dynaudio speakers for instance use an acoustical 3rd order crossover, using 1st order filters with xover frequencies that are separated by more than one octave. One of the drivers used has to be connected with reverse polarity in this case.
Regards
Charles
Depending on the natural rolloff of the drivers you can make it work. Some Dynaudio speakers for instance use an acoustical 3rd order crossover, using 1st order filters with xover frequencies that are separated by more than one octave. One of the drivers used has to be connected with reverse polarity in this case.
Regards
Charles
I've read all sorts of reasons why 1st orders filters are best if your drivers can work with them they have become my filter of choice.
People say things like amplitude and phase response when summed are accurate duplicates of the original signal. Also square wave and transient response are best.
I current believe most of what I have read.
I have witnessed a LR 2nd order LP filter turn a distorted sine wave from my sig generator into quite a clean & tidy sine wave. I would hazard a guess that it would have more than a negligable effect on a music signal that a sine wave that constantly changes amplitude and frquency, a bit like the sine wave from my sig generator. As 1st order filters have the best square wave response I thought that if you can use then then you should.
People say things like amplitude and phase response when summed are accurate duplicates of the original signal. Also square wave and transient response are best.
I current believe most of what I have read.
I have witnessed a LR 2nd order LP filter turn a distorted sine wave from my sig generator into quite a clean & tidy sine wave. I would hazard a guess that it would have more than a negligable effect on a music signal that a sine wave that constantly changes amplitude and frquency, a bit like the sine wave from my sig generator. As 1st order filters have the best square wave response I thought that if you can use then then you should.
primalsea said:
Your understanding is correct- this IS one of the time-old problems with first order filters. Lobing is another. But if you do an early rolloff and you have to re-equalize to get back to a flat response, you've gained nothing as far as the driver is concerned.
First order filters actually work well in a very, very, very limited number of cases.
He wants to use it at a quite low crossover frequency, so lobing is of little concern (depending on driver -size and -placement).
Also a transient perfect (or phase accurate) crossover would have a 90 degrees phase-shift in the crossover area. But as said before.
What are the drivers you want to use it for ?
Regards
Charles
Also a transient perfect (or phase accurate) crossover would have a 90 degrees phase-shift in the crossover area. But as said before.
What are the drivers you want to use it for ?
Regards
Charles
ouch! I am too hoping to use 1st order filters.
my drivers are as et undecided but the top contenders are:
Fostex FX208N in ML-TL or bass reflex mated to a FF85K (or 2) in sealed or open baffle
OR
Jordan JX125 in a small TL mated to a JX 53 (or 2) open baffle
My limitations are:
cabinet must be small (bass cabinet 32"H x 10" W x 8" D), F3 of 40-45Hz, SPL of 95db at 2 m at 50Hz, and most important the speakers must be musical.
amplification will be:
SS 30W class A (see Indian Group amp Project on this forum) for bass and EL84 SE (if 1 fullrange is used and if the Fostex combo is chosen) or EL84 PP (if 2 fullranges are used forstex or jordan).
the reason of looking at 1st order is that the XO could then be PLLXO and there would be NO XO components between the drivers and amplifiers. Would such an application be suitable for 1st order?
(BTW the surround and center speakers would use Fostex F125K or Jordan JX92 with no XO at all)
my drivers are as et undecided but the top contenders are:
Fostex FX208N in ML-TL or bass reflex mated to a FF85K (or 2) in sealed or open baffle
OR
Jordan JX125 in a small TL mated to a JX 53 (or 2) open baffle
My limitations are:
cabinet must be small (bass cabinet 32"H x 10" W x 8" D), F3 of 40-45Hz, SPL of 95db at 2 m at 50Hz, and most important the speakers must be musical.
amplification will be:
SS 30W class A (see Indian Group amp Project on this forum) for bass and EL84 SE (if 1 fullrange is used and if the Fostex combo is chosen) or EL84 PP (if 2 fullranges are used forstex or jordan).
the reason of looking at 1st order is that the XO could then be PLLXO and there would be NO XO components between the drivers and amplifiers. Would such an application be suitable for 1st order?
(BTW the surround and center speakers would use Fostex F125K or Jordan JX92 with no XO at all)
phase_accurate said:I don't see any reason for doing so !
Not applicable to this ap, but Rune uses this technique to deal with baffle step in his Phase Linear TL
dave
BTW my proposed mid-hf amp
http://ptsoundlab.free.fr/sectubes/schemas/el84/classa20w/dppclassa20wel84.htm
http://ptsoundlab.free.fr/sectubes/schemas/el84/classa20w/dppclassa20wel84.htm
Someone asked about drivers, they are all Seas units
Tweeter 25TNF, Mid MP14RC, Woofer P25REXDD.
The enclosure has a volume of 100 L but this is adjustable.
I didnt realise that there would be a drop in the FR if the -3db points for each XO are offset by 2 octaves - 150Hz & 600Hz. I thought the FR would sum flat.
Tweeter 25TNF, Mid MP14RC, Woofer P25REXDD.
The enclosure has a volume of 100 L but this is adjustable.
I didnt realise that there would be a drop in the FR if the -3db points for each XO are offset by 2 octaves - 150Hz & 600Hz. I thought the FR would sum flat.
Only the x-over by itself will sum flat and only if the -3dB points are the same. Keep in mind that you have 90 degrees phase-shift and not 360 degrees as with LR crossovers and therefore it won't sum flat with -6dB.
For the mid you can get a 3rd order highpass function consisting of your 1st order RC highpass and the drivers natural in-box rolloff (2nd order). But this would still not be a transient-perfect crossover.
I am not familiar with this midrange so I don't know what it can take and if it is suitable for shallow rolloff at all. But there is for sure someone on this forum who knows.
If you want to have a transient perfect crossover then there are some possibilities but they won't be minimalistic in terms of component count.
Regards
Charles
Would the total responce of drivers & XO sum flat if I reverse the polarity of one of the drivers?? If this wont work for an offset of 2 octaves would it work for a greater offset. Would this counteract all the reasons why 1st order filter are liked so much if I did???
I'm not opposed to using higher order LR filters but I herd the LR 24dB/oct can make the system sound lifless. I realise this was a subjective opinion but it did come from more than one person.
I'm planning on making the active XO easily changeable from 1st order butterworth to LR 12 & 24db/oct to allow some experimentation anyway. But.. I can see that a standard 1st order XO might not work, but I have this current mind set of a longing to use one in one form or another.
I'm not opposed to using higher order LR filters but I herd the LR 24dB/oct can make the system sound lifless. I realise this was a subjective opinion but it did come from more than one person.
I'm planning on making the active XO easily changeable from 1st order butterworth to LR 12 & 24db/oct to allow some experimentation anyway. But.. I can see that a standard 1st order XO might not work, but I have this current mind set of a longing to use one in one form or another.
The greater the complexity of a passive crossover, the more resistance it will exhibit in the pass band, there's no way around that. Because of this resistance, you are robbing some of the amplifier power from the drivers, which gets dissipated in the crossover, and restricts the dynamic range.
I doubt a correctly designed active XO of higher order exhibits the same problem. It might be that you get problems with on axis and off axis response with different order crossovers though.
I doubt a correctly designed active XO of higher order exhibits the same problem. It might be that you get problems with on axis and off axis response with different order crossovers though.
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