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Discussion Starter #41
Maybe easier to implement: allow some EQ parameters on the sweep generated from within REW. This will allow us to confirm the predicted EQ filters are indeed flattening out the response (and also measure ED-ed response in other locations).
 

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I'll get around to providing solutions in time, but this is a development team of one I'm afraid.
Thank you for your immense contributions, John! Chalk me up as another user who could definitely benefit from External Sweep functionality. :wave:
 

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I tried this 'a good while back' but couldn't get it to work. I do use the wdn driver when watching 3D films.

I am using an AES16e S/C in my HTPC. When running REW, I need to be able to feed the analogue REW signal from my USBPre1.5 back through the PC/AES to the processor using jRiver. 'It's so I can measure multiple sub's'.

I am not sure this is possible. I did wander if I could use 1 PC to take the measurements and another PC to play a REW sweep?
It is possible to; "use 1 PC to take the measurements and another PC to play a REW sweep". This is the process I have been using. So far as I am aware, I'm the only one routinely doing it this way.

It is comparatively common to use the routing features now available within the JRiver. There are also other utilities to address rerouting of the signal within one PC. I haven't done that way so cannot help in how to do that however. Apparently JRiver forums have discussed and supported this approach reasonably well though. I would guess that that forum is your best resource.

The basic process to use 2 PC's is likely even more difficult to setup. It is also more likely to be problematic in use than the JRiver option. When using 2 PCs, if the timing of the measurement process is wrong, then the low frequencies or high frequencies can be distorted. It takes some practice and experience to get the timing right.

The basic Process for using 2 PCs:
> Record the desired REW sweep in Audacity or similar program.
> Edit it as needed to contain say; 3.5s of silence before the sweep starts.
[I also added maybe 5s at the end, but I don't know if that is really needed. It just seem like a safe approach.]
> Save it in either wav or flac format being sure that it is the same sample rate as the original sweep.
> Play the file on one PC using any music server that shows the track timing as it plays.
[I use Foobar2000 over DLNA to my Pre/Pro since that is the remote music server I use for my music.]
> Play the sweep file and when the timing shows '3s' (0.5s before the sweep starts) start the measurement on other PC. If the LF or HF of the resulting measurement looks to be truncated or distorted then adjust the start timing of the measurement relative to the timing indicator as necessary. [In my setup I can select measure just after 3s displays on the music server.] In my case I find there is maybe 0.5s tolerance in the initiation of the measurement on the 2nd PC.

We need to be sure that REW settings on the PC used to capture the measurement are the same as those that were used to record the sweep. Any change to the start or stop frequency or sample rate will definitely corrupt the measurement.

This sounds easy, but I had a lot of problems getting the file setup correctly and learning how to get reliable measurements.

An example below from my setup shows the SPL of the internal sweep and the external (DLNA) sweep using Foobar with an active FIR phase correction filter. The SPL differences shown are trivial as there are no SPL filters in my situation. The Phase chart however shows the impact of the phase correction filter.

SPL.PNG

Phase.PNG

Again, using the JRiver routing capabilities is probably the better choice, but it is possible to see the impact of filters implemented within a music server using either method.
 

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Thanks jtalden. I think I shall wait for my REW 'guru' to take a look at this when his next round.

Looking at the jRiver 'loopback' option. I just cant see how you get the REW sweep to run through jRiver when it's going from my REW/preamp/processor
 

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Re: Feature Request: External sweep with REW

This is something I have been wanting to try, although I think I can just use the RTA and a pink noise track for my purposes.

The goal is to confirm if the output from my sources is flat. Specifically, I have a FLAC media player with an optical out. It has no input so I can't route the REW live signal into it. But I could make a pink noise WAV file and load that onto the player, and then run the optical cable into my sound card. I think the only caveat is I must use REW on a PC to access the optical input on my sound card, correct? I prefer the Mac version but don't recall seeing the optical input as an available option in Mac REW.


Sent from my iPhone using Tapatalk
 

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Looking at the jRiver 'loopback' option. I just cant see how you get the REW sweep to run through jRiver when it's going from my REW/preamp/processor
the jriver asio line in or WDM option means the signal chain is

REW -> jriver -> DAC

you don't go out to a prepro and then back into jriver (well you could if you really wanted to and had the appropriate hardware)
 

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Hi. Where could I get a sweep that runs from say 10 - 200 hz?
I will make you one later today, just take a minute. I assume you want 48k sample rate, 16 bit, -20 dB, and the standard 256k length? It has to match your REW settings precisely, or REW won't be able to make sense of it. I will make 2 sweeps, one for left and one for right. Do you want a third that goes to both left and right together, for subwoofer use?
 

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I will make you one later today, just take a minute. I assume you want 48k sample rate, 16 bit, -20 dB, and the standard 256k length? It has to match your REW settings precisely, or REW won't be able to make sense of it. I will make 2 sweeps, one for left and one for right. Do you want a third that goes to both left and right together, for subwoofer use?
Hi AudiocRaver. Many thanks for the offer, I really appreciate the help. However it appears I have 'finally' got REW running through jRiver now so I will not require the sweep.

cheers.

Will
 

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the jriver asio line in or WDM option means the signal chain is

REW -> jriver -> DAC

you don't go out to a prepro and then back into jriver (well you could if you really wanted to and had the appropriate hardware)

Matt. Is there a way I can also use the 'loopback as timing reference' through jRiver?
 

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Any progress implementing a convolver in REW?
I'm really curious to get at detailed analysis of my system with Audiolense XO corrections. I have done the pink noise/RTA test and it looks really promising, but it would have been very interesting to see a frequency sweep, waterfall, impulse response, excess group delay +++ I do not have a jriver license (trial period has expired) and don't want to spend 50$ for a single measurement:)
 

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Re: Feature Request: External sweep with REW

Doesn't audiolense let you measure with the filter in place?

Alternatively you could convolve the sweep with your filter offline and use this as the external measurement sweep.
 

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Audiolense only gives a simulated response, which is supposed to be quite good. I could do something like you suggest, do you think it would be possible to simply play a 20-20000Hz sweep through my SBT and at the same time do a measurement with REW? I guess there would be some timing issues, but that might be alright?
 

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Thanks a lot:) The latest beta version(7) of REW has implemented exactly what I needed. I can generate a testsweep with a time reference and store it on my music server. I can then play the file though my Squeezebox with the correction file installed in the Inquz convolver. The measure procedure waits for the time reference tone before it starts recording. It worked like a charm:)
 

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I am an "old hand" with REW but quite new with using JRiver as a player and active three way crossover. Using WDM as the device for REW works, but all my sweeps are choppy and the measurements "may be corrupted". I made a few trials of the WAV method described above, and it does work. In my case, I tell REW to output to an unconnected port so it's happy :) I have to manually start the sweep WAV in JRiver; it takes a bit of luck to get the timing right, but it will read a good sweep.
 
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