Suspended floor and bass node...

[MadFloyd]

Hi all,

My system is on the main floor of my house - a suspended floor. I have an annoying node around 30hz that creates bass overhang that interferes with the 'groove' of music that has content in that frequency range. I don't know if this is at all related to the flex in the floor or not. My room is rather strange - while 24 feet long in some places, there are no parallel walls and the width at it's shortest (where the speakers are) is less than 13'. It is also not enclosed (half walls, entrances etc).

I'm asking because it is currently carpeted and I'm considering changing the carpet for hardwood floors (with area carpet strategically placed for 1st floor reflection). This would add some mass to the floor and I'm wondering if anyone knows what the potential effects of this might be - good or bad.

Thanks.

 

[DonH50]

Are you sure it is from the floor and not the room dimensions? Unfortunately analysis of odd shapes is challenging... To me a suspended floor is really suspended; either isolated by dampers like in a studio or noise/vibration-controlled room, or a suspended floor over a crawlspace like some computer server rooms that run air for cooling along with wiring looms under the floor. If it is just a normal house floor it could be the problem but I would look to room size, walls, ceiling height, etc. for the source of the peak.

Mass will generally reduce the vibration amplitude and raise the frequency. If you are redoing the floor, you could go to extra underlayment (like another layer) with glue between layers to provide a better seal and tighter coupling of the mass. Need to make sure the floor joists will support the extra mass, natch...

The wavelength of a 30 Hz signal is about (1127'/s / 30 Hz) = 37.6' and modes can occur at multiples of a quarter wavelength (about 9.4'). An extra subwoofer in such a situation can compensate for a peak but peaks, unlike nulls, are usually amenable to EQ unless something structural is being excited. Floor or wall flexure, etc.

Sorry, not much help... If you have REW or some other way to measure the frequency response you could do it at a fairly low level, below that which usually causes structural vibration of any consequence, and see if there is a resonant peak related to room dimensions. A friend or acoustician might be willing to do that for you.

HTH - Don

 

[BlueFox]

Ian, don’t know if the suspended floor is a problem or not, but my instinct says it doesn’t help. My house is on a concrete slab, the living room sits on it, and the bass is tight and controlled. Good luck.

 

[DaveC]

The floor is not likely causing a node but ime it's best to isolate speakers from floors, looks like you're doing that. If you're installing a new floor you could reinforce your current structure a bit though, especially where the speakers are. You can also add a sound deadening layer under the new wood floor as well.

I think for the 30 Hz node you're best off consulting a specialist who can figure out what's going on... as Don said odd shapes can be difficult to analyze vs a straight rectangular room.

 

[MadFloyd]

Thanks for the comments, much appreciated.

 

[bazelio]

I know someone who uses these:
http://www.townshendaudio.com/hi-fi...e-cinema-vibration-isolation-speaker-podiums/

He says his floorboards used to rattle before he started using them. Stillpoints didn't help but the Townshends he won't give up.

 

[sujay]

I have the same - townshend podium custom made for me for the speaker weight. I find them very stable, better than any feet and they provide excellent isolation.

 

[spiritofmusic]

I run my Zus w down firing subs onto an 1861 Victorian suspended timber floor, 50x35 overall span, w plenty of flex. We laid a new ply top, then vinyl.

Upon this, my Zus are now on Arya Audio RevOPods, onto 1" thick Panzerholz plinths, onto Symposium Acoustics Svelte platforms, thence to floor.

Taking my bass control issues and making them non issues.

 

[PeterA]

Ian, I think you may have installed lolli columns under a joist running below your massive speakers. If that is the case, and they are adjustable, you might want to tighten or loosen them, changing the resonant frequency of the floor in the process, and see if you can hear a difference. That is just a thought.

Changing from wall to wall carpet to a hard wood floor with an area rug will also change the acoustic of the room, but this is more about reflections and dampening or enlivening the higher frequencies. I agree with DaveC, it may be worth consulting an expert. You know you have a complex set of conditions with that room. Given the scope of your renovation, it may be worth the incremental consulting fee. The sonic improvement could be significant, but you really won't know until you talk to someone specifically about your set of conditions and then listen to the end result.

I wish I had your flexibility in my small historic room to make some significant changes.

 

[Kingsrule]

MPods on carpet is not ideal. Too much movement. Go back to original spikes or try the MPods w/spikes that PeterA is talking about. Also reinforcing the floor from the basement helps. U need to completely eliminate speaker movement before doing anything else.
I know u said MPods were an improvement but maybe not, at least regarding your bass observation. Your observation regarding pulling the pins on the MPods is exactly opposite of my experience (I'm on hardwood floor) ......

 

[PeterA]

Kingsrule, that is a very interesting comment about the MPods. Are you saying that there must still be some movement over carpet despite the massive 450 lbs distributed down to four footers spread out on outriggers?

Could you explain how you and Ian describe the effect of MPods in opposite ways? I think I missed these explanations. I'm curious because I am considering SPods for my Q3s. Thanks.

 

[MadFloyd]

MPods on carpet is not ideal. Too much movement. Go back to original spikes or try the MPods w/spikes that PeterA is talking about. Also reinforcing the floor from the basement helps. U need to completely eliminate speaker movement before doing anything else.
I know u said MPods were an improvement but maybe not, at least regarding your bass observation. Your observation regarding pulling the pins on the MPods is exactly opposite of my experience (I'm on hardwood floor) ......

I've never heard of MPods on spikes, but since I'll have hardwood floors soon I wouldn't spend $ on these anyhow.

If your experience pulling the pins on your MPods produced MORE bass I think that would be unusual; it's known to tighten up the bass - which it definitely does for me.

 

[MadFloyd]

The floor is not likely causing a node but ime it's best to isolate speakers from floors, looks like you're doing that. If you're installing a new floor you could reinforce your current structure a bit though, especially where the speakers are. You can also add a sound deadening layer under the new wood floor as well.

I think for the 30 Hz node you're best off consulting a specialist who can figure out what's going on... as Don said odd shapes can be difficult to analyze vs a straight rectangular room.

Can anyone recommend a specialist?

 

[Lagonda]

Can anyone recommend a specialist?

Dr.Freud maybe ?

 

[Kingsrule]

I didn't realize u already decided to do the hardwood floor...

 

[MadFloyd]

I didn't realize u already decided to do the hardwood floor...

Yep. Carpet is in bad shape and we're putting in hardwood in the kitchen so it just seemed like a good (aesthetic) solution.

 

[Kingsrule]

I've never heard of MPods on spikes, but since I'll have hardwood floors soon I wouldn't spend $ on these anyhow.

If your experience pulling the pins on your MPods produced MORE bass I think that would be unusual; it's known to tighten up the bass - which it definitely does for me.

I don't recall u saying pulling the pins tighten the bass...I guess I misunderstood what u said. Hard to understand MPods sitting on carpet and pad anyway

In any case the bass between the MProject and M6 is so different comparison of MPod effects would be tough to quantify.

 

[DaveC]

Can anyone recommend a specialist?

I'd check out Acoustic Frontiers and GIK.

 

[MadFloyd]

In any case the bass between the MProject and M6 is so different comparison of MPod effects would be tough to quantify.

How is the bass different between the two models? I've never heard anyone mention this before.