Active Filter Four for 4way mostly dipole

MethMan · 20th September 2006, 06:07 AM

I have made a filter proposal based on Active Filter Four for my 4way project. You can see it here .

Enclosure: H-frame for woofer 42 cm deep, 35cm wide. Midwoofer, mid and tweeter baffle 35 cm wide with a few cm foldback.

I see some possible problems.
1) Overall gain caused by high levels of dipole roll-off EQ together with low Q drivers and input buffer gain. I am scared of interstage clipping, overloading PA's inputs and DC level on filter outputs. Maybe it is not an issue, but it seems me a lot.
2) With tweeter's filter exception there are BP filters at the "beggining" of chain. Unfortunatelly I hasn't found a better topology.
3) I don't know if the additioning of All-pass filters is clever idea, because the delay falls with frequency and tweeter delay could become as a problem. Isn't a better idea to leave woofer - midwoofer XO unequalized? Circa 15 cm difference in at 100Hz is only 5% phase shift.

Can you tell me your opinions?

Rudolf · 20th September 2006, 08:58 AM

Methman,
I didn´t know that dipole design can be made that complex.

But I still don´t see the notch filter for the H baffle quarter wave resonance.

Why do you set a ShLPF 25-330Hz Dipole rolloff EQ, if you are low passing LR4 at 100Hz? So your woofer out 36 dB gain is much lower in reality - I guess about 14 dB less IMHO.

MethMan · 20th September 2006, 01:26 PM

Sorry it is not clearly visible - EQ2 (board1) stage is used for H-frame quaterwave resonance supression.

ShHPF I set this way: Fequal is around 140Hz for 42 cm H-frame and dipole gives 6dB gain above Fequal against monopole. That is why I've set dipole rolloff EQ to "twice" the Fequal to ensure flatness of the response in the xo region above 100Hz XO. Am I wrong?
When you take a look at Phoenix there is a 10-300LP in woofer's branch - this led me think as I'm thinking.

MethMan · 23rd September 2006, 02:48 PM

Hundreds of AFF boards sold and no one met those problems?

20th September 2006, 06:07 AM	#1
MethMan diyAudio Member Join Date: Jun 2004 Location: Praha	Active Filter Four for 4way mostly dipole I have made a filter proposal based on Active Filter Four for my 4way project. You can see it here . Enclosure: H-frame for woofer 42 cm deep, 35cm wide. Midwoofer, mid and tweeter baffle 35 cm wide with a few cm foldback. I see some possible problems. 1) Overall gain caused by high levels of dipole roll-off EQ together with low Q drivers and input buffer gain. I am scared of interstage clipping, overloading PA's inputs and DC level on filter outputs. Maybe it is not an issue, but it seems me a lot. 2) With tweeter's filter exception there are BP filters at the "beggining" of chain. Unfortunatelly I hasn't found a better topology. 3) I don't know if the additioning of All-pass filters is clever idea, because the delay falls with frequency and tweeter delay could become as a problem. Isn't a better idea to leave woofer - midwoofer XO unequalized? Circa 15 cm difference in at 100Hz is only 5% phase shift. Can you tell me your opinions?

20th September 2006, 08:58 AM	#2
Rudolf diyAudio Member Join Date: Mar 2003 Location: Germany	Methman, I didn´t know that dipole design can be made that complex. But I still don´t see the notch filter for the H baffle quarter wave resonance. Why do you set a ShLPF 25-330Hz Dipole rolloff EQ, if you are low passing LR4 at 100Hz? So your woofer out 36 dB gain is much lower in reality - I guess about 14 dB less IMHO. __________________ www.dipolplus.de

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20th September 2006, 01:26 PM	#3
MethMan diyAudio Member Join Date: Jun 2004 Location: Praha	Sorry it is not clearly visible - EQ2 (board1) stage is used for H-frame quaterwave resonance supression. ShHPF I set this way: Fequal is around 140Hz for 42 cm H-frame and dipole gives 6dB gain above Fequal against monopole. That is why I've set dipole rolloff EQ to "twice" the Fequal to ensure flatness of the response in the xo region above 100Hz XO. Am I wrong? When you take a look at Phoenix there is a 10-300LP in woofer's branch - this led me think as I'm thinking.

23rd September 2006, 02:48 PM	#4
MethMan diyAudio Member Join Date: Jun 2004 Location: Praha	Hundreds of AFF boards sold and no one met those problems?

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