Glass Doors and Bass

[Muzykant]

Hi All,

I have been thinking about my dual SB-13 Ultras' lack of infrasonic bass lately. All the reviews I read suggest that they should have at least some output in that frequency range, but mine simply do not.

My room is just over 3000 square feet and has two large glass sliding doors into the backyard. Together with windows they take up about half of the back wall. The other day I was playing some subsonic test tones and went out to the backyard to see if I could hear anything. I was shocked when I looked at the glass. It was resonating violently, almost flapping. I ran back inside and reduced the volume.

My question is: could this movement of the glass be cancelling out the subsonic frequencies?

Thanks!

 

[Adam]

Hi. Question - have you run a frequency sweep and checked the SPL right near the subs? You shouldn't see any cancellation right up near the cones. If you can measure low frequency response up there, then you know something else is happening if you don't measure it at your listening position. I can't answer your question about the glass because I don't know at what frequency it resonates (which should be a function of the doors size, thickness, and number of panes).

 

[Muzykant]

Thanks for your reply, Adam. No, I have not checked the SPL in close proximity to the subs, but I expect there to be some. After all, it's a sealed design with a decent sized enclosure and the cone is fairly large and is moving quite a bit. No reason for them not to perform in that range.

Unfortunately, I can't check this right now. I know that it's not just my seating position that doesn't get bass below 17 Hz, but in the entire room it's nowhere to be found. But maybe if I put my ear next to the cones there will be signs of life.

I guess for now my question is theoretical - can this happen? Large glass surface moving out of phase and cancelling out subs' cone movements?

 

[WaynePflughaupt]

Seventeen Hz? Your expectations for the SB13 may be unrealistic. SVS only spec’s the sub down to 20 Hz to begin with. Their website shows a graph with response dropping about 12 db/octave below 30 Hz, indicating that the SB13 will get 20 Hz with cabin gain from the typical room. However, your room is 3000 sq. ft., which assuming an 8-ft. ceiling is 240,000 cu. ft. IOW, your room is probably so big it offers only minimal cabin gain, not enough to get 20 Hz, much less anything below that. Bottom line, if infrasonics are what you’re after, you should have gone with one of SVS’s ported options. Or in your room, maybe a couple of them.

Regards,
Wayne A. Pflughaupt

 

[its phillip]

http://www.data-bass.com/data?page=system&id=107&mset=119

2m GP outdoors a single SB13U can muster 92.6 dB at 16hz. I'm guessing you meant 3000 cu ft, not sq ft, so a pair in room should do much better. Try some different placement options If your room is actually 3000 sq ft, you'll need a lot more subwoofer than a pair of SB13s.

 

[Muzykant]

My bad, wrote it late last night. I meant 3000 cubic feet, 3100 to be exact. Sorry for the confusion.

 

[Adam]

My SB13-Ultra does quite well below 20Hz in a room about that size, at least down to 16Hz which is the lowest sine wave that I've measured. Here's a chart from my review of it. I also have a large (about 9' tall) double glass sliding door in that room and multiple large openings to other rooms. Like Philip mentioned, I'd also suggest playing around the location of the subs.

Btw, have you done measurements - or are you listening for subsonic frequencies? I'm not trying to be patronizing, but they are called subsonic because you can't hear them. I certainly couldn't hear the 16Hz tone, but the SPL meter picked it up very well.

 

[Muzykant]

I have not done the measurements as I don't have the omnidirectional microphone and software needed. I only have a digital (they don't sell analogue anymore) SPL meter. When I say there is no output below 17 Hz, I am talking about my ears not being able to detect the pressure. Back in the day I had Infinity Perfect 12 sub in a sealed enclosure in the trunk of my car, and I remember playing test tones well below 20 Hz. I could not hear the pitch anymore, but I sure felt the pressure on my ears. It had somewhat nauseating effect. Now I feel the same thing with my SB-2000 sub located in a 1600 cubic feet room - detectable down to 9 Hz in some spots. But it's just not the case with my Ultras.

I performed the bass crawl test some time ago, when I had only one Ultra. Current location felt like one of the best in the room. Only spot where I could detect the lowest subsonic bass was inside a closet. But I decided it would be a waste of a sub to put one there.

Anyway, at least one of you has glass doors and it does not seem to affect the performance. I guess, that's my answer.

 

[TLS Guy]

If you are seeing the glass move and hear the bass outside, then you glass doors are causing massive bass leakage. As far as bass in concerned they are an open door. I'm certain from your description your problem is bass leakage and not cancellation.

 

[djreef]

http://www.data-bass.com/data?page=system&id=107&mset=119

2m GP outdoors a single SB13U can muster 92.6 dB at 16hz. I'm guessing you meant 3000 cu ft, not sq ft, so a pair in room should do much better. Try some different placement options If your room is actually 3000 sq ft, you'll need a lot more subwoofer than a pair of SB13s.

I was thinking the same thing. He could fit my whole fricken house in that one room. That'd be sweet to have that much space to work with, tho.

DJ

 

[Muzykant]

LOL if I had that much room for home theater, I would probably have money for and get quad Captivators S2... for starters. That would be sweet!

Thanks for all of you who answered. I guess the next step would be to carry one of the Ultras upstairs and try it in a different room with my Prime towers.

 

[herbu]

I could not hear the pitch anymore, but I sure felt the pressure on my ears. It had somewhat nauseating effect.

And you're trying to replicate that in your living room?
Maybe a good way to get company to leave.

BTW, I have 2 ported subs in my room, (PB13U & FV15HP), with a big sliding glass door and lots of windows. I can see the windows and doors flexing, and feel the pressure in my chest. No problem.

 

[Muzykant]

Thanks, herbu. Do you mean to say that I should not be able to detect any air movement at all with my ears even with two subs playing with considerable excursion? I am not talking SPL, pressure in my chest or anything like that. I am talking detectable by ears.