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Total bass suck out at 40hz

So I'm a little slow, but it occured to me today to see if there were test tones recordings on Tidal of Qobuz. Yes there are. I have a radio shack SPL meter so I went to work playing them to see what I had in my room. I was shocked to find a total lack of audible bass at 40hz. At first I thought they must have made an error in the recording. Then I went to a different set of test tones and wow same thing. I never dreamed something like that would take place. I have read a lot of discussions about bass peaks and nulls and always thought it would just be slightly less in volume at the null, not completely gone. So Am I imagining this and if not what do I do to remedy it. I am apparently missing a lot of music and never knew it. I am currently listening to my freshly refinished Yamaha NS 1000m speakers(just put them in the system Wednesday after work) with a Modwright KWI 200 integrated amp and a Lumin streamer/dac. I also have stereo Rythmik  F12 subs. Thanks, Allen.
mizike

Showing 2 responses by mike_in_nc

mike_in_nc
1,124 posts
 
Regarding phase, there are a several ways to adjust. Here are the two I think are best. In each one, you run ONE speaker and its associated sub at a time:

1. Put a mic at the main listening position (MLP), run a sweep, and analyze with something like REW. Move the phase control to get the smoothest frequency response (FR) around the xover frequency. This is the most direct and reliable way, in my opinion.

2. Sit at MLP, having reversed speaker leads of the main to put it out of phase. Play a tone at the exact xover frequency. Adjust phase control to give the best null at that frequency. (Remember to put the speaker back into phase when done!) This is the best way when you don't have the measurement equipment for method 1.

Any phase adjustment depends on positions of main speaker, sub, and listener. If you move anything significantly, it will change, so needs to be redone.

Hope that helps.
mike_in_nc
1,124 posts
 
A 40 Hz null is typical of a room node, as noted. Here’s what worked in my room, where I use two subs and had a 43 Hz null. I moved the subs, measuring at each position. Putting furniture glides ("supersliders" under the feet helps with moving.) The position where the bass null was minimal put the subs behind the listener, near the rear corners.

I agree with others that a distributed bass array of at least 4 subs is a great solution, but I didn’t have room for that.

I also agree that asymmetrical positioning of the subs can help, but I wanted to keep them symmetrical and running in stereo.

The Allison effect (floor bounce cancellation) was mentioned; my impression is, it is typically higher in frequency (100-300 Hz).

SBIR suckout at 40 Hz might be a factor with speakers 7 ft from a boundary, more so for speakers 7 ft from several boundaries.

Oh, one other thing . . . do the subs have continuously variable phase controls, and have you adjusted them for smoothest FR? That can be an important step in many cases. As can be changing the xover frequency, especially if running the mains full range.

I hope that helps.
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