REW software for measurements (waterfall etc)

[JohnA]

Has anyone used this little beauty?

After spending some time with it, I have to say it is marvelous.

1. The software is FREE and works flawlessly from an XP laptop
2. The peripheral bits needed are likely to be found hanging about in an enthusiast's home - RCA cables, adaptors, RatShack meter.
3. It compensates easily for the dbmeter's response (supplied table), even for the soundcard's response (via a feedback RCA cable)
4. It freekin works!

I've done room sweeps while moving around certain pieces of furniture and the results are extremely interesting and totally repeatable.

If you have an XP laptop hanging around with a duplex soundcard (most qualify) it is definately worth a try!

How else would you know if the open/shut door affects room acoustics or what the effect of the curtains is? Even moving the pillows on the back of the sofa create very measurable combe effects.

 

[JonFo]

Hi John, well guess who here has used this as well

I've pretty much used all of them. And REW is actually one of the more elegant ones in terms of usability and cool UI.

The fact that it's multi-platform is a huge plus as well.

I fully agree that using a tool like this is highly instructional for the audio aficionado to learn just what objective impact making certain changes has.

As you note, even subtle things like moving furniture around a bit will have measurable impact.

One caution, don't do final EQ or speaker placement changes based solely on the measured response from the 'prime spot'. use that as a guideline, but always do a three or four more measurements within a 2 to 3' radius of the prime spot and use REW's averaging feature to look at the resulting average before making final decisions.

Also, I find REW to excel at low-frequency metrics and problem determination. Its high-frequency metrics are not quite as sophisticated as saw ETF (R+D) from Acoustisoft. Likewise, the impulse response metric in REW is nowhere near as clear as R+D's impulse, where it's easy to make time-domain correlations.
But it does have the coolest waterfall plots ever. And doing stacked plots is a great way to see before and after impacts.
Since most room induced problems are in the bass frequencies anyway, REW makes a great tool for placing your sub, tuning the crossovers and phase settings, etc.

Given the price, and low cost of accessories, it’s a must-have in my book.

I equate a system set up without the aid of a measurement rig to putting in a hook and hanging a picture on the wall in the dark without using a level. It might come out OK, but probably not.

 

[amey01]

I used this to configure my Behringer DSP1124P - excellent software!

 

[JohnA]

...I equate a system set up without the aid of a measurement rig to putting in a hook and hanging a picture on the wall in the dark without using a level. It might come out OK, but probably not.

good analogy

An interesting observation was the phase relationship between my 'small' sub (2x12" drivers 500w) and the big one (18" 1350w)
In their final locations, set up manually with CD test tones and the dbmeter they work best out of phase.
With REW this shows a 'hump' around 45Hz that cannot be smoothed out without tailing off below 30Hz.
By setting them in phase there is no hump and goes flat down to 15Hz.

The 'out of phase' setup sounds more dynamic and low (no wonder with a 4db hump!)
The 'in phase' setup sounds anaimic and gutless down low, even though REW reports it as flat. In effect the big sub amp works hard and yet you cannot hear or feel it.

Do I go by ear or REW?

 

[nsgarch]

Can I use an in-room PC instead of a laptop?

1. The software is FREE and works flawlessly from an XP laptop
2. The peripheral bits needed are likely to be found hanging about in an enthusiast's home - RCA cables, adaptors, RatShack meter.
3. It compensates easily for the dbmeter's response (supplied table), even for the soundcard's response (via a feedback RCA cable)

If you have an XP laptop hanging around with a duplex soundcard (most qualify) it is definately worth a try!.

John, do I have to have a laptop? I mean, I have a very powerful destop in my listening room, (for architectural CAD work) + an older analog RS SPL meter (which I find easier to read than the digital one) and 3 Nakmichi condenser mics which I can use with the Nak mixer (or not). Realtek HD motherboard sound card (should that be replaced? I seems sophisticated.) And the CPU is an AMD dual-core 64 processor@2204 Mhz., flat display etc., infared sensor (to eliminate mike cable runs?) So can I work with my PC system (and save the laptop money for a lapdance? )

If you say I can use my PC, are, their any additional hardware/audio cards, mods I'd still need?

Thanks alot.

Neil

 

[JohnA]

John, do I have to have a laptop? I mean, I have a very powerful destop in my listening room, an older analog RS SPL meter (which find easier to read than the digital one) and 3 Nakmichi condenser mics which I can use with the Nak mixer (or not). Realtek motherboard sound card should that be replaced? I seems sophisticated but and an AMD dual-core 64 processor@2204 Mhz., flat display etc., infared sensor (to eliminate mike cable runs?) So can I work with my PC system (and save the laptop money for a lapdance? )

If you say I can use my PC, are, their any additional hardware/audio cards, mods I'd still need?

Thanks alot.

Neil

Neil,

I mentioned 'laptop' because it is the most likely solution for the listening room (otherwise you end up with abnormally long RCA cables across rooms)
I also mentioned XP because I am not sure if it works with Vista (it is written in Java, but works really well)
The older analog DBmeter should be fine, if it has line output (they have a compensation table for that one as well)

Have a look at the site over there for the rest of requirements - remember that the RCA splitters stuck in the in/out of the soundcard should be STEREO.
Mark the Right and Left channels if they are not already marked (my splitter were not marked, I had to use a multimeter to identify R and L and a Stanley knife to mark them!

And off you go, 3 RCA cables is all you need - plus the 2->1 RCA splitter for your HiFi input (you will want both channels to be running during the sweep, using the mono signal)

:music::music:

 

[nsgarch]

Neil,

I mentioned 'laptop' because it is the most likely solution for the listening room (otherwise you end up with abnormally long RCA cables across rooms)
I also mentioned XP because I am not sure if it works with Vista (it is written in Java, but works really well)
The older analog DBmeter should be fine, if it has line output (they have a compensation table for that one as well)

Have a look at the site over there for the rest of requirements - remember that the RCA splitters stuck in the in/out of the soundcard should be STEREO.
Mark the Right and Left channels if they are not already marked (my splitter were not marked, I had to use a multimeter to identify R and L and a Stanley knife to mark them! And off you go, 3 RCA cables is all you need - plus the 2->1 RCA splitter for your HiFi input (you will want both channels to be running during the sweep, using the mono signal):music::music:

I 'll read the paper throughly. I guess I could use a IR wireless attached to my SPL? But either way, you need to split the SPL into L and R inputs to go into the sound card. Is that what you're saying?

Thanks

 

[JohnA]

Neil,

The SPLmeter has a line out which is connected to the 'R' of the card's input
The 'R' of the card's output goes to your preamp's spare input (an RCA splitter will make sure that both of your preamp's channels will be engaged)

The 'L' of the card's input is connected directly to the 'L' of the card's output.
This is a feedback loop that is used for the compensation inside the software (cancelling out the non-linearities of the soundcard)

It sounds more complicated than it really is.