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Can I use REW instead of an SPL ?

atr1981

Active Member
Hi Guys,

With reference to previous thread about upgrading sub. I want to test my responses first in the current room to see if my room might be causing me problems.

I have read the sticky on this but can't find the answer. Can I use REW as an SPL ? I don't have a seperate SPL meter to hand and can't get one for a month or so.

Thank you.
 

milesr3

Active Member
Roset3,

If you don't want to wait a month then you can get the ubiquitous RS SPL meter for under £20 delivered from e-bay (Item number: 120205558430). I ordered one yesterday, should be here tomorrow.

Also noticed that you are local to me (I'm in Felixstowe) so could potentially help out with the meter once I've finished with my own measurements.

Richard
 

atr1981

Active Member
Milesr3, thank you but my profile is a little confusing. My home is in Ipswich but i'm away at the moment with the RAF in Cyprus. Thank you very much for your kind offer though.
 

atr1981

Active Member
Ok, so RS SPL on way from UK to me in Cyprus.

Does anyone know if the RS SPL meter has a 3.5mm jack or a phono jack on the side ?

Thanks.
 

chrisgeary

Well-known Member
its a phono jack
 

atr1981

Active Member
I have managed to get some sort of SPL device working until my proper one turns up.

Here is my graph.

I have not got any way of changing it at the moment except using the notch filter.

I have done the same out of phase and it is exactly the same.

Any thoughts ?
 

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mattkhan

Distinguished Member
Thank you.

So I need a phono to 3.5mm for going into the PC and same coming from PC to my AV amp ?
yes

FWIW I use optical from PC to amp as it's in permanent residence connected that way, the only thing lost is the ability to compensate for response of the analogue output of the soundcard. I read once that someone measured their soundcard and found all the variation in the input stage, if true (and you calibrate your soundcard using the loopback method) then you're not even losing that.

Cheers
Matt
 

mattkhan

Distinguished Member
Any thoughts ?
I'm guessing you have no way of knowing the accuracy of the meter and it's rolling off around 30-40Hz hence exacerbating the rolloff of the sub about the same time making the falloff look much steeper then it really is.

OTOH if you have no idea of the accuracy of the meter then it could be completely all over the place :suicide:
 

atr1981

Active Member
mmm, thanks.

I'll look into a bit more. The input i'm using is the Denon mic that came with my amp.

I should have the RS SPL within a couple of weeks so will try and connect that but it will still be going through my PC.

Does anyone know how the notch filter can be used effectively ?

Thanks.
 

HiFiRuss71

Distinguished Member
Does anyone know how the notch filter can be used effectively ?
Yes, but as it's a rotary analogue control, it takes a bit of patience. It has controls to target the frequency of the offending peak, the depth of the cut (notch) and the width (bandwidth or Q) of the cut.

Set the frequency to say about 50Hz and then (using REW) set the deepest cut with the narrowest bandwidth. Move the frequency very progressively until you've targeted the middle of you biggest peak. Then, it's a case of trying to reduce the cut and broaden the bandwidth to achieve the most minimal and smoothest cut necassary to remove the offending peak. This could take a good solid hour of twiddling.

However, I wouldn't bother until the SPL meter arrives. Unless you can compensate for the mic/meters frequency response failings, it's impossible to say with any certainty what's really happening.

If it's of interest, I had a play with the same control on an SVS sub here. With patience, it was possible to get results that would have let me get away without my separate EQ altogether. If the SVS had been mine that is.:(

Russell
 

atr1981

Active Member
Thank you very much for the sound advice.

I believe I can still connect the SPL to the PC ?

Is that abetter way of doing it ?
 

gstott

Standard Member
Don' tmean to hijack - I have a sub on the way and have the RS SPL meter but only have a laptop. Any of you out there in the same position? Presuming I need an external soundcard? An extra lead or two?

Anyone any advice on setting this up?

Gareth
 

atr1981

Active Member
No problem, I think you might.

I believe the output from REW needs to be connected from a line out.

Home Theatre Shack has all the REW information you could ever want.
 

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