# REW Questions



## HTB2015 (Nov 24, 2010)

My first venture with REW or any EQ for that matter. I have built the TriTrix L/C/R and an 8cuft 15" Dayton Ultimax Sub tuned to 16Hz. I've built these speakers for my brother-in-law and currently have them in my game room to "run them in / test them". 

I'd like to figure out how to perform the EQ on these speakers with my game room with the plan to be able to do it on my own when I get to my BILs house. 

Here is the current setup:

- TriTrix MTM L/C/R powered by Onkyo TX-SR608
-15" Dayton Ultimax 8cuft, 16Hz, powered by the iNuke1000DSP. 
- UMM-6 USB Microphone
- MacBook with OS 10.6

I've downloaded REW V5 and hooked up the computer to the Receiver via a 3.5mm jack. 

Questions:

1) is it ok to use a 3.5mm jack to hook up the computer and receiver?
2) when I try to calibrate the sound card I have to max the sound card output and receiver output to get it within 6dB. It's very loud!! I've tried adjusting the sweep level but it doesn't seem to help. 
3) do I need an SPL meter to calibrate the SPL meter in the program?

Thanks for any help!!


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## JohnM (Apr 11, 2006)

1) Yes
2) You shouldn't hear anything when calibrating the soundcard, the only connection is from the soundcard's output to the soundcard's input, but soundcdard calibration is not needed with a USB mic as you are not using the soundcard's input
3) Yes if you need to be precise, but it just sets the level on the graphs so it is also fine to set the test signal to a comfortable level and tell REW that is 75 dB

You will probably get warnings about low signal level as you need to use V5 on 10.6, V5 came before USB mics which have lower levels. You can ignore the warnings as long as the levels are above -45 dB FS or so.


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## HTB2015 (Nov 24, 2010)

Thanks JohnM

I will post some graphs soon


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## HTB2015 (Nov 24, 2010)

wow guys, this looks horrible. I'm posting it anyway. Not sure whats going on. 

I would have set the limits like I'm supposed to (45-105 and 15-200) but nothing shows up so I had change the limits.


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## Phillips (Aug 12, 2011)

HTB2015 said:


> wow guys, this looks horrible. I'm posting it anyway. Not sure whats going on.
> 
> I would have set the limits like I'm supposed to (45-105 and 15-200) but nothing shows up so I had change the limits.


You need to be measuring at 75db, you are measuring at 35.

Turn the amp up.

Is your REW SPL calibrated?

Was your sub on or is this just speaker/s only?


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## HTB2015 (Nov 24, 2010)

Phillips said:


> You need to be measuring at 75db, you are measuring at 35. Turn the amp up. Is your REW SPL calibrated? Was your sub on or is this just speaker/s only?


I checked my levels right before measurement and my SPL meter read 74-76dB.


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## HTB2015 (Nov 24, 2010)

Phillips said:


> You need to be measuring at 75db, you are measuring at 35. Turn the amp up. Is your REW SPL calibrated? Was your sub on or is this just speaker/s only?


Also forgot to mention. It is speakers and sub were on together.


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

Also, change the graph from LIN to LOG. There's a button that toggles between the two in the upper right corner of the screen.

Regards,
Wayne


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## HTB2015 (Nov 24, 2010)

Wayne A. Pflughaupt said:


> Also, change the graph from LIN to LOG. There's a button that toggles between the two in the upper right corner of the screen. Regards, Wayne


Thanks Wayne, I will do this before my next post.


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## Phillips (Aug 12, 2011)

Is the sub going?


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## HTB2015 (Nov 24, 2010)

Phillips said:


> Is the sub going?


Yes, sub is working. Sounds decent too. I will try and play with it tonight. Let me know if you have anymore suggestions.


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## HTB2015 (Nov 24, 2010)

Ok. I found out that the input device was my computers microphone....so I went to preferences and sound on my MAC and changed it over to the UMM-6. I thought this was definitely it but it wasn't! However I am getting some different looking graphs. I tried calibrating the SPL meter...My radio shack sound level meter in A weighting reads 75dB when the SPL meter on REW reads 24dB. 
Really confused here.:help:


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## HTB2015 (Nov 24, 2010)

So I've plugged the mic into my desktop PC this morning and it gets up to about 50dB with moderate level talking. I could move my Desktop to the game room where the speakers are but that would be a serious hassle. It just seems like there isn't good sensitivity with the microphone.


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## Phillips (Aug 12, 2011)

Read the SPL calibrating in REW manual, this will produce more accurate SPL readings

You have a mode at approx. 38hz, EQ can fix that nicely. Do you have EQ? 

Extension looks good.


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## HTB2015 (Nov 24, 2010)

Phillips said:


> Read the SPL calibrating in REW manual, this will produce more accurate SPL readings You have a mode at approx. 38hz, EQ can fix that nicely. Do you have EQ? Extension looks good.


I've read the manual but I will check it again. 

I have the iNuke1000DSP so I believe this could act as my EQ?


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## HTB2015 (Nov 24, 2010)

Alright! I think I may have something. Thanks Phillips for telling me to go back to the manual. How does this look?



Now for the EQ. I'm sure I'll have questions but I will refer to the manual first.:bigsmile:


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## HTB2015 (Nov 24, 2010)

Any help is appreciated. I feel like I'm getting way over my head.


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## HTB2015 (Nov 24, 2010)

I increased the flatness target to its max of 6 to reduce the number of filters.


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## JohnM (Apr 11, 2006)

You are using the wrong target shape for that measurement, the selected target shape is for a subwoofer alone (which is why it rolls off above 80 Hz) but the measurement looks like sub + main or perhaps just a main speaker as it seems to have very limited low frequency extension.

You may want to re-check the SPL calibration, hopefully you are not really measuring signals at 110 dB as that would be very bad for your ears, your equipment and your relationship with your neighbours!


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## HTB2015 (Nov 24, 2010)

JohnM said:


> You are using the wrong target shape for that measurement, the selected target shape is for a subwoofer alone (which is why it rolls off above 80 Hz) but the measurement looks like sub + main or perhaps just a main speaker as it seems to have very limited low frequency extension. You may want to re-check the SPL calibration, hopefully you are not really measuring signals at 110 dB as that would be very bad for your ears, your equipment and your relationship with your neighbours!


Yes it is sub and mains. It would be really helpful to see what good low extension looks like. Kind of depressing that you're saying it's limited. It's tuned to 16Hz, I've got the 1000W amp turned all the way up and almost max power from receiver. On C Weighting with my Radio shack meter it said 102db. The sweep only lasts a couple seconds so it's not bad. Although, my wife has complained!


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## JohnM (Apr 11, 2006)

There is no benefit from measuring at high volumes, quite the opposite. Turn the volume down on your receiver so that the SPL in the room is around 75 dB with the test signal playing.

The measurement in post 12 showed very good extension, still strong at 16 Hz, the measurement in post 16 shows poor extension, rolling off rapidly below 35 Hz. Looks like the sub was not on or the signal wasn't being sent to it, if compared with the earlier measurement, so something isn't right.

Were the measurements made with the mic at the same position?

I suggest you try using REW's Pink PN test signal and looking at the response on the RTA with these settings:

 

Make sure the sub and main speaker are both playing and check the effect of the sub's phase/polarity switch to make sure it is set correctly.


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## HTB2015 (Nov 24, 2010)

Thanks for the help JohnM! I'm out of town til next week but will do this as soon as I get back.


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## HTB2015 (Nov 24, 2010)

This time I moved the listening position back about 3 feet. I've been trying to keep it as consistent as possible. I thought I would post the pictures of my steps. When I check levels before taking measurement it says I'm too low. Also, my iNuke by itself is about 64dB from the fan noise.


Checking Levels in Preferences: You can see how it doesn't meet the Out.


Calibrating SPL meter. I am using C weighting which at 75dB sounds very soft.


Pink PN Test Signal and I have no idea what any of this means.


Mains + Sub


Sub Only


All


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## JohnM (Apr 11, 2006)

You can ignore the "input too low" messages, REW V5 pre-dates the USB mics which are now commonly used.

The RTA plot with Pink PN is showing you the same thing as a measurement does (see how the shape of the response on the RTA window you captured is the same as the sub only measurement?) but you need to select _RTA 1/48 Octave_ in the control panel, not Spectrum (per the control settings I showed above). Deselect the THD button on the RTA window, it is only meaningful when showing the results from sine wave test tones. 

The advantage of the RTA window and Pink PN is you can move the mic somewhere else and see the response plot update immediately to show the response in the new position. Handy for picking a good listening position or, if you can position the sub where your head would be (not necessarily easy ) you can move the mic about to find the best position for the sub.


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## HTB2015 (Nov 24, 2010)

JohnM said:


> You can ignore the "input too low" messages, REW V5 pre-dates the USB mics which are now commonly used.
> 
> The RTA plot with Pink PN is showing you the same thing as a measurement does (see how the shape of the response on the RTA window you captured is the same as the sub only measurement?) but you need to select _RTA 1/48 Octave_ in the control panel, not Spectrum (per the control settings I showed above). Deselect the THD button on the RTA window, it is only meaningful when showing the results from sine wave test tones.
> 
> The advantage of the RTA window and Pink PN is you can move the mic somewhere else and see the response plot update immediately to show the response in the new position. Handy for picking a good listening position or, if you can position the sub where your head would be (not necessarily easy ) you can move the mic about to find the best position for the sub.


Life has been busy but I'm planning on installing everything at my brother in laws superbowl weekend. I feel like I have a good idea of how to at least get started.

JohnM, thanks for the tip about RTA and Pink PN and moving the mic around for best listening position. I will definitely use that. The only thing I don't really know how to do is the EQ. Or how to fix a "mode" with EQ. I will take many measurements and send the final measurements when its all done. Thanks for all help!!


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