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Old 18th February 2005, 04:43 PM   #231
SvErD is offline SvErD  Norway
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Quote:
Originally posted by tiroth
Ack! Too many accounts. Mail is off to you.

Thanks Tyler. I tried to reply, but my e-mail got bounced, seem like your storage is full.
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Old 18th February 2005, 05:04 PM   #232
tiroth is offline tiroth  United States
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You can just use my email link here, which is ttt -at- anidian -dot- com. Sorry.
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Old 18th February 2005, 10:27 PM   #233
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I think that I would like to place a volume pot on the input of my MOX active crossover boards. Would somebody like to recommend an impedance value for a pot?
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Old 23rd February 2005, 08:40 AM   #234
S.C is offline S.C  United States
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I have a quick question. Do I need all the parts soldered onto 4 seperate boards in order to achieve a 2.1 setting? And what other combination can I do with 4 boards?
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Old 22nd April 2005, 01:19 PM   #235
Bricolo is offline Bricolo  France
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Hi,

Can someone confirm is this is correct? I want to make standard filters, so for:

-1st order filter, I use Q=0.5
-2nd order filter (Linkwirt Riley) I also use Q=0.5
-3rd order filter (Butterworth) I use Q=1 for the first 2 poles, and Q=0.5 for the third pole
-4th order (Linkwitz Riley) I use Q=0.7 for both pair of poles

Right?
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Old 22nd April 2005, 03:01 PM   #236
AndrewT is offline AndrewT  Scotland
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Hi Bricolo,
I would like to give you a simple reply but because of my lack of knowledge it would come out kind of complicated.
So instead of directly answering your q
Bessel has a low Q about 0.5 or maybe a little higher.
Butterworth has Q=1/root2
The various HiQ allow sharp cut off out of band (avoid for speaker xover) but maybe notch for taming resonance.
Linkwitz Reilly is two cascaded Butterworth. So L-R must be even order of poles and overall Q = 0.5. I have seen reference to a 3 pole L-R but don't know how to achieve it.
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Old 22nd April 2005, 04:15 PM   #237
MBK is offline MBK  Singapore
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Hi Bricolo,

unless Jens jumps in and proces me wrong...

- for the LR filters, correct, and you set the frequencies to the actual cutoff frequency. Overall Q is 0.5 and at cutoff the response is 6 dB down.

- for the Butterworth overall Q must be 0.707, but you achieve this by a combination of both Q and different frequencies for the partial stages. At cutoff the response is 3 dB down. You chould get the Q and frequency scaling factors from a filter table. Somehow Q of 1 plus Q of 0.5 sound wrong to me.
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Old 22nd April 2005, 04:16 PM   #238
Bricolo is offline Bricolo  France
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Andrew

I know what overall Q I must obtain, my question was about the MOX's setup.

Bessel's Q is SQRT(3)/3 so 0.578
LR is 0.5 as you said. So 3rd order would be made of a 1st order and a 2nd order Butterworth (since overall Q= Q1*Q2 and that a 1st order has always Q=0.7)

But I don't see the need for a LR3, since it won't sum flat if you sum the high pass and the low pass together
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Old 22nd April 2005, 04:21 PM   #239
Bricolo is offline Bricolo  France
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Quote:
Originally posted by MBK
Hi Bricolo,

unless Jens jumps in and proces me wrong...

- for the LR filters, correct, and you set the frequencies to the actual cutoff frequency. Overall Q is 0.5 and at cutoff the response is 6 dB down.

- for the Butterworth overall Q must be 0.707, but you achieve this by a combination of both Q and different frequencies for the partial stages. At cutoff the response is 3 dB down. You chould get the Q and frequency scaling factors from a filter table. Somehow Q of 1 plus Q of 0.5 sound wrong to me.
A Butterworth filter has all it's poles at the same frequency, so there's no combination of frequencies.
Overall Q must be 0.707, yes. My tables gives 2 poles with Q=1, and a third pole at the same frequency. So, Q1=1 and Q2=0.707

But for a 1st order, the Q setting has no effect, 1st order is always Q=0.707. The Q setting on the mox only changes the gain for a 1st order, so I said 0.5 because this one gives an unity gain


I'm just not 100% sure about that so I asked for confirmation
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Old 22nd April 2005, 04:26 PM   #240
MBK is offline MBK  Singapore
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Bricolo,

Quote:
But for a 1st order, the Q setting has no effect, 1st order is always Q=0.707. The Q setting on the mox only changes the gain for a 1st order, so I said 0.5 because this one gives an unity gain
that's how I also understand it.

I couldn't remember that Butterworth frequency values, if the table says same f0 then it should be OK.
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