volume question

[acoustat6]

Hello, When I started using REW I adjusted the volume on my preamp and computer to get as close to 75db as possible. I achieved 74db due to the fact that I have stepped attenuators and it was as close to 75db as I could get, no problem. I have not changed any settings since starting using REW so as to keep everthing the same as I was more interested in the changes in my extensive room treatment, and changes in seating and speaker placement.

My question is that I have decided to change crossover points and have noticed that when I change volume levels ( overall or adjusting the bass to main levels ) there is no change in my freq response db levels. I.E. I do a check and then change the volume level and I dont see the level change in the graph. The graph looks the same even though I reduced or increased the volume on my preamp by 10 db. Also I see that the REW SPL meter does not go above 75db and does not give consistent readings with the Radio Shack meter.

The graphs do change ( but not the level ) when I make even a small change in speaker or seating location.

What gives?

Bob

[brucek]

I have not changed any settings since starting using REW so as to keep everthing the same

Not necessary. just reset the levels to 75dB every time you use it. Any level changes in the overall response can be adjusted with the Add offset thumbwheel for comparisons.

Also I see that the REW SPL meter does not go above 75db

Not true. It can be set, and it will read any level you like.

and does not give consistent readings with the Radio Shack meter.

Not true. It will track whatever the radio Shack meter sends it. Certainly the RS meter is jumpy when offered pink noise, but the REW meter simply tracks.

What gives?

No idea - you're doing something wrong for sure..

brucek

[JohnM]

What input range are you using on the RS meter?

[acoustat6]

Hi John, Thanks for responding. I know that it is wrong.

I have rechecked the reference level and it is at 75db.

What I meant was, I had not made any changes to my system, ie: volume level changes, crossover etc.

The REW meter is reading up to 75db only and will not show a higher spl level even though the RS meter does set on 80db.

I did 3 tests the first calibrated to 75db and it is on the money at 75db. Then I dropped the volume level on my preamp by a significant amt and the reading traced the 75db line except for the lowest freq. I then raised the volume level on the preamp by a significant amt and the trace was the same as the 75db trace.

I put in my new crossover module, dropping my crossover point from 120hz to 85hz. I ran a test and then adjusted my subs level and got the same freq response on the same trace no matter if the subs volume was up 10 db or down 10 db. My RS meter and my ears verify the volume changes.

I am getting what looks like the "correct" freq response, its that my levels dont increase or decrease on my graph

Thanks,
Bob

[acoustat6]

Hello, I just did a test where I calibrated my REW with the RS meter to 75db. I then ran the pink noise generator and the results were the RSmeter and the REW meter showed 75db. I then increased the preamp volume as the volume increased the RS meter went up to match the increase in gain but the REW meter never went past 75db and it said clip. I must have something turned off or adjusted wrong? What could it be?
Thanks,
Bob

[brucek]

Did you re-run the Calibrate SPL routine in REW?

brucek

[JohnM]

You may have the input level too high into the soundcard so that the signal level is clipping heavily and simply can't read any higher. Bring up the VU Meters to see the levels on the input when you are doing the SPL calibration and when you are comparing the REW and external meters and make sure the input peak stays below 0dBFS. It would also help if you showed screenshots of one of your measurements and of the Scope tab after a measurement, it is hard to diagnose problems from descriptions alone. What input range are you using on the RS meter?

[acoustat6]

Hi Bruce, I have recalibrated the SPL, and I still get this.

John, I will do and check what you said. I am using 80db on my analog RS meter.

Bob

[acoustat6]

Hi, I fixed my problem, though I am not sure what I did to effect the change. A setting was though causing clipping before and it no no longer is.
Bob