Subwoofer Calibration

James Hardiman

Mickey Wilson wrote:

I’m recently delving deep into the K system and studying the honor roll. I have 2 questions:

Thank you for signing my copy of Mastering Audio 3rd Edition a few years back and answering some questions of mine over the phone. Your book has helped tremendously over the years! 

I do have a question that has still been bugging me for a while and I keep revisiting it— I have two Yamaha HS5 monitors in stereo, and then the Yamaha HS8S subwoofer attached as well. I have calibrated each monitor to the EBU standards, but with your recommendation of 83db SPL per monitor @ -23 LUFS for each channel (using the EBU pink noise file).

EBU doesn’t talk about how to set a subwoofer. What should I set it to? I’ve read articles about setting it to the stereo SPL from the monitors so it will match, but I’m not sure. Most recently, I took a 40-80hz pink noise file from Blue Sky at -23 LUFS per channel to where it shows -20 LUFS in stereo just like the EBU pink noise file, then changed my subwoofer to match the stereo SPL of my monitors which came out to around 86db. 

I just want to make sure that my rendered audio files will have the right amount of bass translated to other systems and will replicate what it is that I’m hearing. I’m afraid that my exports will have less bass than what I hear in the studio, so I want to find out more about what the best way is to set this sub to where the gain adjustment will make sense with the EBU monitor calibration.

Thank you for the all the help Bob, I really appreciate it!

Best regards,
Mickey Wilson

Hi, Mickey.

Hope this helps,

First of all, an overall SPL measurement is not going to help you align your subwoofer. You should measure using a high quality FFT analyzer. Room EQ Wizard is “donation ware” and I highly recommend it. There is a learning curve, but everything worth doing requires some learning! There is an excellent help menu that will serve as a tutorial. And a forum as well. 

Secondly, I’m very sorry to tell you that a single subwoofer is always going to be a compromise. Because the electrical sum of two channels is not always going to match the acoustical sum of those independent channels. The best I can recommend is that you first align the left channel with the sub. Using Room EQ Wizard find the very best crossover point, slope, phase and distance compensation you can. Then repeat that for the right channel with the sub. Your bass response for each channel should be as flat as possible and mate with its respective main speaker as seamlessly as possible. Then measure the response with both channels playing in phase (mono playback) and see if the bass response goes up. It usually will. That error is what you have to live with because you only have a mono subwoofer. You can decide if you want to raise the bass a dB or so compared to your original per-channel measurement in order to favor mixes which have the bass in the center (which is most of them) but I would not go all the way. Perhaps a setting exactly in the middle between the per-channel-optimum and the mono optimum is the best compromise, especially if the difference is only a couple of dB, then your error will not be more than a dB and that should be excellent. 

Other than that I can best recommend you get two subwoofers!

Hope this helps,