Originally Posted by buckchester
I have a miniDSP 2x4 rev A. I have starting using AustinJerry’s tutorial on how time align two subs on one channel before room correction (thank you for this great tutorial, AustinJerry). I have a question about step 7 (Determining Gain Structure). I do not have a voltmeter and would prefer not to have to purchase one if it’s not absolutely necessary. I’m using a fairly standard AVR (Marantz SR5005), similar to what I assume most users on here with a miniDSP might use. I’ve looked in the manual and looked online, but haven’t been able to find out what the output voltage is for its SW pre-out. I contacted Marantz and they said it is about 5V. Will this cause a problem given the miniDSP I have has an input voltage of only 0.9V RMS? Does this mean it will be necessary for me to pick up a voltmeter and go through this step?
Sorry, I am a miniDSP noob for sure.
First of all, a voltmeter is not an absolute requirement, and there are fairly easy ways to validate your current configuration without using one.
Follow the instructions to output the REW 60Hz test signal to the sub channel with the AVR volume set to zero and the sub channel trims set to zero as well. The input and output level sliders on the 2x4 should be set to zero as well. While the test tone is playing, observe the output meters on the 2x4. If the level is extending into the Red area, then clipping is occurring. Using the AVR sub channel trim adjustment, gradually lower the trim until the 2x4 output meter no longer reaches the red zone. Make a note of the trim setting. If you lower the trim setting all the way to -12 and are still getting output into the red zone, then you have a more serious gain issue.
Next step is to run the Audyssey calibration. For the purposes of this exercise, you can run a single Audyssey measurement (the first measurement sets the speaker trims and delays) and complete the calibration so that the sub trim is set. Open the AVR menu and observe the trim level set by Audyssey. If the trim level is equal to or lower than the value you determined in the first step, then you have no gain issue. You can play your system at reference levels (which is very loud) without risk of clipping.
If, however, the Audyssey sub channel trim is higher than what you determined in step 1, then you must make adjustments using the master volume control--specifically you will not be able to set the master volume control to zero (reference) without risking clipping on the sub channel. Compensate as follows: if the trim level determined in the first step is -6, and the Audyssey trim is -3, then you should restrict playback master volume to -3.
Finally, you can leave your laptop connected and the 2x4 plug-in output meters displayed on the screen while you are playing content (a movie or music). Observe the output meters to verify that while playing content at normal levels, you are not seeing the output go into the red area. This should give you reasonable assurance that the gain setting for the 2x4 is appropriate. Of course, if what I have outlined doesn't work for you, report back here and we'll se what the next steps are. And Alan makes a good point--a voltmeter, if you end up needing one, is not a very costly investment.