# REW for active crossover measurement



## Jonas_h (Jan 7, 2009)

I have some semi-DIY speakers (LF enclosure + HF horn/compression driver) which I want to setup using REW. The way I would do it, was to measure each enclosure in a "infinite space" environment, to look at the response of each driver to follow a LR24 crossover slope. I have always used REW for measuring this on my subwoofers, but it looks like there is a limit in REW for doing this with higher frequencies? The crossover limits (bass limited and subwoofer mode) allows for 50hz and 150hz as max crossover which will not work for my use (800hz). I find this limitation very weird, as it would not require extra work in regards to the software to allow greater values.

Is there a way to use REW as I would like to? I would really like to use REW, as its filter calculations are exactly what I need.

I could generate the target curves myself, but I cannot seem to find the formula to calculate the Linkwitz Riley crossover. This solution would be just as fine.


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## SAC (Dec 3, 2009)

To be honest, I am not sure what the process is that you are referring to.

But yes, REW can be used to determine each driver's frequency and impulse or ETC response to determine timing for signal alignment purposes relative to a given reference/measurement point.

While this paper specifically addresses the alignment of a sub with a full range speaker, the basic concept is the same for all inter-driver alignments.

In the paper Charlie utilizes Easera, but the same functions are available in REW.


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## Jonas_h (Jan 7, 2009)

Sorry if I wasnt clear. My basic question is: How do I set the LR24 target curve for a 800hz crossover in REW?


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## EarlK (Jan 1, 2010)

Jonas_h

> You seem to be confusing EQing a full-range speaker ( which REW will nicely do by generating filters for specific EQs ) with having REW create ( an electronic ) filter set for crossover purposes ( which REW will not do ) .

> If you want a free program to help you design a really accurate passive crossover, then look at Jeff Bagby(s)' PCD software ( which runs onto of Excel ). 
> It has a steep learning curve ( for most ) but is worth it if you want to design accurate passive crossovers that also contain EQ ( notch-filters, etc. ) .
> Click the pic ;



PCD imports .frd and .zma files which you create using measurement software ( such as REW, HolmImpulse, ARTA ) .

:sn:


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## Wayne A. Pflughaupt (Apr 13, 2006)

Hey Jonas,

Not sure exactly what you’re trying to accomplish, but...


Jonas_h said:


> ... but it looks like there is a limit in REW for doing this with higher frequencies? The crossover limits (bass limited and subwoofer mode) allows for 50hz and 150hz as max crossover which will not work for my use (800hz). I find this limitation very weird, as it would not require extra work in regards to the software to allow greater values.
> 
> Is there a way to use REW as I would like to? I would really like to use REW, as its filter calculations are exactly what I need.


... you aren’t bound to the REW subwoofer settings. Just measure each enclosure *full range*. Of course, this will require a full range mic with a soundcard that has a mic pre amp, not just the RS meter. From the measurements you will be able to tell the upper and lower limits of each enclosure, and from that you can get an idea of an appropriate crossover frequency.

Regards,
Wayne


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## jtalden (Mar 12, 2009)

Jonas_h said:


> I have some semi-DIY speakers (LF enclosure + HF horn/compression driver) which I want to setup using REW. The way I would do it, was to measure each enclosure in a "infinite space" environment, to look at the response of each driver to follow a LR24 crossover slope. I have always used REW for measuring this on my subwoofers, but it looks like there is a limit in REW for doing this with higher frequencies? The crossover limits (bass limited and subwoofer mode) allows for 50hz and 150hz as max crossover which will not work for my use (800hz). I find this limitation very weird, as it would not require extra work in regards to the software to allow greater values.
> 
> Is there a way to use REW as I would like to? I would really like to use REW, as its filter calculations are exactly what I need.
> 
> I could generate the target curves myself, but I cannot seem to find the formula to calculate the Linkwitz Riley crossover. This solution would be just as fine.


Your methodology makes sense to me as one reasonable approach. [I’m just a hobbyist however so this may not be much comfort.] You intend to measure the individual drivers SPL responses with the active XO in place and EQ the SPL to follow the ideal LR-24 (aka LR-4) response curves for the 2 drivers. For the resulting combined response to work as intended it will also be necessary to properly adjust the time delay between the two drivers to align the phase at the XO. Assuming you also have that capability the combined response should be flat. [I surmised from my reading and experimentation that this is basically the approach that Audyssey follows.]

REW does not provide an 800 Hz HP or LP target response as you noted. I cannot help on that front, but I can help you work around it. You mentioned that you were having trouble finding the LR-4 response profiles to import into REW as house curves and that is where I can help. 

I setup a spreadsheet that provides the correct response for any XO freq you want. I then exported the responses to text files that can be imported onto REW as house curves and allow you use it as the target curve the EQ tab.

Attached are the 2 house curves and a chart showing the calculated responses from my spreadsheet. I can provide the spreadsheet also if needed.

View attachment LR-4 HP.txt


View attachment LR-4 LP.txt


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## Jonas_h (Jan 7, 2009)

That is exactly what I need! Thanks. If you could upload the spreadsheet too, it would be great.


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## jtalden (Mar 12, 2009)

Jonas_h said:


> That is exactly what I need! Thanks. If you could upload the spreadsheet too, it would be great.


Okay, I cleaned up my spreadsheet so it is friendly - I hope! 

View attachment Calc But-x and LR-2x SPL Responses.zip


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## robbo266317 (Sep 22, 2008)

I have used REW to measure speakers with an active crossover. I did a full range sweep of each driver with the crossover in place. I only turned on each amp individually to get each plot and "close mic'ed" the drivers. The results matched what I had expected from the design.
You can see the individual drivers crossover slopes on the left hand side.


 

Cheers,
Bill.


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## acoustat6 (Mar 7, 2008)

Hi Jonas, REW is perfect device for measuring crossover points. The best part of doing this is that you can adjust each driver for its own in room response. I have a 3 way system and you can see some of the results in this thread 

http://www.hometheatershack.com/forums/rew-forum/27565-my-new-room-response.html

Jtaldens target response for various crossover points looks perfect and I will use them also, thanks!:T

Bob
PHP143


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## rewjack (Aug 24, 2011)

jtalden said:


> Your methodology makes sense to me as one reasonable approach. [I’m just a hobbyist however so this may not be much comfort.] You intend to measure the individual drivers SPL responses with the active XO in place and EQ the SPL to follow the ideal LR-24 (aka LR-4) response curves for the 2 drivers. For the resulting combined response to work as intended it will also be necessary to properly adjust the time delay between the two drivers to align the phase at the XO. Assuming you also have that capability the combined response should be flat. [I surmised from my reading and experimentation that this is basically the approach that Audyssey follows.]
> 
> REW does not provide an 800 Hz HP or LP target response as you noted. I cannot help on that front, but I can help you work around it. You mentioned that you were having trouble finding the LR-4 response profiles to import into REW as house curves and that is where I can help.
> 
> ...


Well I have found here quite what I was looking for. Thank you.

I still have a question .
How can I save the target response from REW's EQ window into JRiver to use these Xovers curves as active XO files?
I would be able to send separate signals, up to 8 ch from JRiver to my 8 ch DAC.


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## jtalden (Mar 12, 2009)

I don't know anything about JRiver or HTPC setups, but probably someone else will jump in and help out.


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## ccclapp (Jan 28, 2012)

rewjack said:


> I still have a question .
> How can I save the target response from REW's EQ window into JRiver to use these Xovers curves as active XO files?
> I would be able to send separate signals, up to 8 ch from JRiver to my 8 ch DAC.


...These threads discuss this, but using the JRiver MC convolution option (and loopback feature) vs just EQ:

http://yabb.jriver.com/interact/index.php?topic=68828.0

http://yabb.jriver.com/interact/index.php?topic=70962.0

http://www.hometheatershack.com/for...ver-mc-adjusting-individual-speakers-how.html


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