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Author Topic: 48db/Octave on Itech Crossovers  (Read 5661 times)

Justin Myers

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48db/Octave on Itech Crossovers
« on: April 21, 2011, 05:08:46 am »

Hello

I'm trying to find info on the use of 48db/octave slopes on crossovers.

I'm trying to set up a 3 way system using Itech HD and Itech amps.
So, Crown Itech HD amps on the Mid/Hi with FIR Brickwall filters as the overall extra latency is only 1ms. At the Mid/Sub crossover point the latency for FIR filters is too much so I thought using 48db/octave Linkwitz Riley filters.
Is the phase distortion for 48db/octave filters too much for practical use?

Thanks

Justin
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Ian Stuart

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Re: 48db/Octave on Itech Crossovers
« Reply #1 on: April 21, 2011, 06:53:36 am »

Hello

I'm trying to find info on the use of 48db/octave slopes on crossovers.

I'm trying to set up a 3 way system using Itech HD and Itech amps.
So, Crown Itech HD amps on the Mid/Hi with FIR Brickwall filters as the overall extra latency is only 1ms. At the Mid/Sub crossover point the latency for FIR filters is too much so I thought using 48db/octave Linkwitz Riley filters.
Is the phase distortion for 48db/octave filters too much for practical use?

Thanks

Justin

Generally speaking, yes it's too excessive.

Whilst I cannot speculate much on characteristics of the phase distortion you will be producing with that filter slope, I can't imagine it will be pretty. 

the Linkwitz Rielly filter is exceedingly popular and common but the 24db/Oct slope is generally the highest practical order slope and the furthest most engineers will go with their filters.

Also, never underestimate the destructive power of a 1ms delay.

Happy hunting!
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Bennett Prescott

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Re: 48db/Octave on Itech Crossovers
« Reply #2 on: April 21, 2011, 06:22:22 pm »

Justin,

Anything over 24dB/octave sounds like ass to me. Why use an overly steep crossover when it is going to make phase alignment off axis practically impossible, and rob you of otherwise usable power bandwidth between drivers? You can get significantly more performance out of a box using shallower filters.
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Justin Myers

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Re: 48db/Octave on Itech Crossovers
« Reply #3 on: April 21, 2011, 10:51:19 pm »

Thanks for your help Ian and Bennett.


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Uwe Riemer

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Re: 48db/Octave on Itech Crossovers
« Reply #4 on: April 22, 2011, 02:48:40 am »

Hello

I'm trying to find info on the use of 48db/octave slopes on crossovers.

I'm trying to set up a 3 way system using Itech HD and Itech amps.
So, Crown Itech HD amps on the Mid/Hi with FIR Brickwall filters as the overall extra latency is only 1ms. At the Mid/Sub crossover point the latency for FIR filters is too much so I thought using 48db/octave Linkwitz Riley filters.
Is the phase distortion for 48db/octave filters too much for practical use?

Thanks

Justin

Hi,

I tend to use steeper crossovers, if adjacent passbands are further separated in terms of wavelength to reduce overlap and therefore the area of missalignement

and Martyn Rowe told us recently, that he used 48dB crossovers on the MLA in an overlap mode

As you can see in general generalizations are wrong

Uwe

« Last Edit: April 22, 2011, 04:46:11 am by Uwe Riemer »
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Marsellus Fariss

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Re: 48db/Octave on Itech Crossovers
« Reply #5 on: April 22, 2011, 03:28:40 am »

Out of curiosity how much latency do you incur using FIR filters on the mid/sub?
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Justin Myers

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Re: 48db/Octave on Itech Crossovers
« Reply #6 on: April 22, 2011, 05:04:56 am »

Out of curiosity how much latency do you incur using FIR filters on the mid/sub?

Hi

Down to 250hz it is 3.67ms, Down to 125hz it is 7.33 ms. Below that it is 14ms.

Justin
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Justin Myers

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Re: 48db/Octave on Itech Crossovers
« Reply #7 on: April 22, 2011, 05:10:05 am »

Hi,

I tend to use steeper crossovers, if adjacent passbands are further separated in terms of wavelength to reduce overlap and therefore the area of missalignement

and Martyn Rowe told us recently, that he used 48dB crossovers on the MLA in an overlap mode

As you can see in general generalizations are wrong

Uwe

Hello
Haven't heard what Martin Rowe Said. I'll do a search.
Thanks
Justin
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ProSoundWeb Community

Re: 48db/Octave on Itech Crossovers
« Reply #7 on: April 22, 2011, 05:10:05 am »


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