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Discussion Starter · #1 · (Edited)
I am just trying my first measurements. When I check the level, it registers as -36dbs. I have the sound card going to my preamp, not my amp (in fear of blowing out a driver by a direct connection). The volume control on the preamp will not adjust the sound coming through the speakers. The RS SPL meter is measuring at 75dbs, so the sound coming out of the speakers is pretty loud. So, I'm wondering why the software says it is coming out too low?


Any suggestions would be greatly appreciated.

Thanks,
Nick
 

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When you did the soundcard calibration routine using a loopback cable, were the levels all correct when running the Check Levels routine?

brucek
 

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Discussion Starter · #3 ·
Hi Bruce,

I forgot to edit my question - I'm sorry. I had the cables in the mic feed rather than the line in and out feeds.

I think I have it calibrated now, but I'm not sure if I did the left channel version properly. When I take a measurement, it says it is okay to measure, but when I measure the dbs go above zero in the red. Is that okay?

Can you please tell me if there is a way to look at a number of measurements all on one graph?

Thank you,
Nick
 

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but I'm not sure if I did the left channel version properly.
If you're referring to using the "Use Left Channel as Reference" method, it's better to use the standard soundcard cal file method.

when I measure the dbs go above zero in the red. Is that okay?
No, then the signal will be clipping. Keep it to at least -3dB or lower.

please tell me if there is a way to look at a number of measurements all on one graph?
Yes, that's what the Measured tab is for. Select the checkboxes at the bottom of the Measured page for the plots you want on the graph at the same time.

brucek
 

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Discussion Starter · #5 ·
Bruce, now I have 6db headroom when I measure. The resulting graph now shows the freq response mostly under my target of 75dbs. Is that what it should look like? I need to figure out how to post a picture of the graph...

I'd like to work on positioning my speakers - is there a write-up on the site that talks about how to go about doing that?

Thank you for your help!
Nick
 

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now I have 6db headroom when I measure
That's good.

The resulting graph now shows the freq response mostly under my target of 75dbs. Is that what it should look like?
As long as you ran the Check Levels routine and then ran the Calibrate SPL routine before you measured, then sure, a lot of the signal can be below 75dBSPL. I'd have to see a graph to be more confident..

I need to figure out how to post a picture of the graph...
To save an REW graph click the Save icon in the lower left corner of the REW graph display and it's stored on your computer. It produces an 800 wide plot.
See here on how to post a graph.

I'd like to work on positioning my speakers - is there a write-up on the site that talks about how to go about doing that?
No, too many variables. You just have to ask questions about it.

brucek
 

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Discussion Starter · #8 ·
Bruce, attached is a sample measurement. Can you please tell me if I am on the right track? For speaker positioning, do I just do one speaker?

Thanks again.

test measurement.jpg
 

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Use a vertical axis of 45dB-105dB and a horizontal axis (in this case) of 20Hz-3KHz.

I suggest you did not run the Calibrate SPL routine after the Check Levels routine. THis why the level of the plot is below the 75dB target.

Do one speaker at a time and then test them both in concert to check for interaction.

brucek
 

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Discussion Starter · #10 · (Edited)
Use a vertical axis of 45dB-105dB and a horizontal axis (in this case) of 20Hz-3KHz.
Do you mean on the graph limits function?

Do you mean do calibrate one speaker at a time or run measurements one speaker at a time?

By the way, I had to lower the output volume due to the headroom being so low, and that is when the freq. response moved below the 75db line.
 

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Discussion Starter · #11 ·
Hi Bruce,

I re-calibrated and came up with a better chart. I did each speaker separately and then together (both with the 'right' box checked. Together the dbs went up too high so I notched it back down. Please let me know if you think I can proceed. I had an example of how to move speakers around and measure, but I can't find it now!

Here is the new chart at 1/24:
 

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Do you mean on the graph limits function?
Yes..... the new graph above is correct.

Do you mean do calibrate one speaker at a time or run measurements one speaker at a time?
Run measurements one speaker at a time. That way you can see which speaker (or both) that may have a peak or dip. Then run a measurement together to see if doing so causes some interaction that is good or bad.

Please let me know if you think I can proceed.
For sure. It looks fine..

brucek
 

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Discussion Starter · #13 ·
Bruce, the speakers have some big differences. By the way, I moved the woofers to the outside, so the readings are different than the prior graph. I don't think moving speakers around will change much. Subs would be helpful, but I wonder if it would be better to start over entirely knowing I need subs when I already have full range speakers...


right speaker - dark blue, left light blue.jpg
 

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Remember to set your vertical axis to 45dB-105dB.

A sub or subs that can be moved anywhere in the room while running the mains crossed at 60-80Hz is usually the best solution whether or not you have full range speakers. I have full range mains that are in the $11K range and I still run them as small because that's the way to get the best sound from your room.

brucek
 

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You might be surprised, Nick, at how much the freq resp graphs can change with speaker positioning. In your graph, the nulls around 53Hz and 130Hz look very much like nulls I have that I can associate with the location of my main speakers.

In playing with the position of my front speakers and my sub, I have uncovered a seldom mentioned advantage of raising the sub's crossover and limiting the main's woofer. My front left main is near the corner of the room. By moving it at least 4' from the corner, I was able to drop the null from the 1/4 wave reflection out of the corner to 72Hz. Then, by raising the sub crossover in the AVR to 80Hz, the effect of this reflection was minimized.

My guess is that, whichever speaker is your dark blue line, if you move it around in two dimensions, that will help you verify which surface reflection is associated with your null. Then you can determine if you want to do anything about it.

Have fun,
Bill
 

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Discussion Starter · #16 ·
Will do on the settings - I thought once you set it it stayed that way.

I'll give the speaker movement a try per Bill's suggestion (thanks, Bill). Meanwhile, I would very much appreciate input with regard to subs -- I assume the favored piece of equipment is the BFD.

I was thinking I would buy a mic and a preamp, but maybe the money would be better used on a pair of subs and the BFD. I have no real idea about the world of subs, so some direction to get started would be greatly appreciated!

Thanks again,
Nick
 

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Discussion Starter · #17 ·
Bill and Bruce, I thought you might be interested in seeing what happened when I moved my left speaker around in two dimensions and measured each movement. I'm still learning how to read the graphs, but the result of moving the speakers about 6" inches closer to each of the side and back walls made a huge difference in the sound sitting anywhere in the room. Now, I need to get some equipment to EQ the bass peaks and see how that sounds.d Meanwhile, I do have a number of nulls and wonder how one begins to deal with them?

Thank you for the help, it is really fun making the music sound so much better!
Nick
wo new spot 2.jpg

And here is the original measurement:

speaker placement - normal (woofers in).jpg
 
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