Yamaha "Subwoofer trim" function ... what's it really do, Yamaha? ;) (2 Viewers)

[ChromeJob]

Just for fun... Mostly.

My RX-V775 manual defines the Subwoofer trim feature (under Options | Volume trim) as "Fine-adjusts the subwoofer volume." Pretty simple. Tweak your subwoofer gain (without going into Setup, Manual Setup, Level). Got it.

But the Yamaha product page for the RX-V675 (shares the same manual as the -775) lays this fancy pants info on us:

The Subwoofer Trim Control enhances the low frequencies by avoiding overlap with the front speaker output. This will result in a cleaner, more focused sound stage while providing a seamless frequency response. When subwoofer frequency overlap occurs in conventional systems, the overall sound is “pushed” toward the subwoofer. Subwoofer Trim Control takes care of this by separating the low subwoofer frequencies cleanly, thus stabilizing the front stage while providing a well-balanced enhanced bass sound. [emphasis added]

The Yamaha RX-V575 page says it too. The RX-V777? Yep. And the HTR-7065. Maybe the RX-A3040 page has more information? No, exact same blurb.

Woah. "Enhances the low frequencies by avoiding overlap with the front speaker output."[1] That sounds more like it's adjusting the roll-off of the frequencies around the bass management sub cross over freq (On Screen | Setup | Manual Setup | Configuration | Bass Cross Over).


But ... WTH, Yamaha. Which is it? Volume trim or super-sophisticated cross over adjustment to enhance sound stage goodness?

[1] I wish I had a dollar for every place that Yamaha surely uses the word enhance(s) in their marketing, technical support, documentation, employee lunch counter menus.

 

[Phil A]

Bass frequencies (for music) will sum in your room. Obviously much depends on the room, the speakers, the sub, the position of the speakers, the position of the sub, etc. So if your mains and sub are producing like frequencies one can get a bass bump. I have a one third octave RTA I use and in one room I have a music server with DSP room correction and measurement software and all I need is a $88 USB microphone from Parts Express. I have the RTA and probably at some point will pick up the microphone. There's also places like rivesaudio.com that sells a test disc for around $20 that's made to work with the Radio Shack analog SPL meter and compensate for the frequency that the SPL meter microphone operates over.

 

[Al.Anderson]

I don't know the answer, but here's my theory, the main/sub crossover is a slope, not a cliff, so when you set it to , say, 80 Hz, you are really getting some volume down another 10-15 Hz. If your sub and main are in the same location, that could artificially accent the bass. If the main and sub are in different parts of the room its not a problem as the bass diffuses more. So my guess is it either increases the slope of the roll-off, or just decreases the LFE gain in the main.

 

[ChromeJob]

I can attest to there being slopes for both main and sub, as I've felt/heard it during some test tones. I haven't sat and done tests with the trim changed, though. Not yet.