REW Forum

**brucek** · **08-31-06, 07:40 AM**

Quote:

More just to see how room responce changes with volume

If you want to see this, then have a single set of filters and use REW to do a response at the different volume levels....

brucek

**eddthompson** · **08-31-06, 08:59 AM**

i havnt had the time run sweeps or to set the filters yet, ive got a new subwoofer on order so im being lazy.

my theory is at 75 db you need to kill a peak by 3db, at 90db, the peak is even larger, so it needs more cut

could be wrong though.

I got my bfd 1124 used for £50, no idea what that is in euros, about $90, total bargin for how much it improves the sound.

**brucek** · **08-31-06, 09:44 AM**

Quote:

my theory is at 75 db you need to kill a peak by 3db, at 90db, the peak is even larger, so it needs more cut

In reality likely not, but in perception it may indeed be so. The frequency response of hearing at low sound pressure levels drops off rapidly for both low and high frequencies. This weakness was the idea behind the "loudness" button you might see on some older receivers. Compensation today for such a response curve with respect to sound level could easily be ameliorated within a DSP, but I don't suspect that's being done too often.

brucek

**dimmie** · **09-06-06, 05:51 AM**

I'm gonna take first meassurements tonight, when setting the input volume and the measurement level, should I use the speakers or the sub to meassure?, as asked in the little dialogue box?...

dimitri

**brucek** · **09-06-06, 08:54 AM**

Quote:

should I use the speakers or the sub to meassure?,

SUB

**dimmie** · **09-06-06, 01:34 PM**

Well.....

I think I have the measurement level, input volume, spl calibrated and so far no problems.

I'm now tackling the soundcard calibration measurement, and the first part was ok, a pretty straight line with a roll off at the beginning and end. with a rimple at the end.

When I checked the calibration, I got the message that the highest level in the measurement is -21,7?.

And apparently that's too low....What is the smartest thing to do now?, I don't want to turn up the amp any further, as it is already at 0.

**brucek** · **09-06-06, 02:12 PM**

Quote:

When I checked the calibration.............

Are you referring to the checking of the soundcard calibration, in that it was successful before doing any more measurements?

If so, did you select a TAB other than the soundcard tab to do this as is specified in the Help files?

brucek

**dimmie** · **09-06-06, 02:26 PM**

Yes I did, when I made the soundcard calibration measurement all looked ok. After that the help file tells you to select the left channel and check if the calibration was succesfull. I then get the message that the highest level in the measurement was too low(-21.7).

I hope I'm being clear enough, in my questioning.

**dimmie** · **09-06-06, 02:35 PM**

The red line in the "left"graph is around the 67 db. point. Which means it's too low right?, My real question is: Shouldn't this red line be around 75 db.?. And What's the best way to get it there?. Which volume should be changed?.

thanks

**dimmie** · **09-06-06, 03:06 PM**

I've upped the soundcard volume a bit, and now the red line reads about 75 db. But the previous measurements have been made with the soundcard volume in the middle. Should I leave the soundcard volume as it is now?, and start from the beginning, or can I just continue to room response measurements?. I'm afraid that my measurements will be off now. Because I've changed the soundcard output volume.

EDIT; I've upped the measurement level to -12 db. which gives me a straight red line at 75 db. The soundcard output is back in the middle now. Iguess I'm ready to start measuring. just have to set the target level, right?.

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