Overcoming Room Resonances

[milton10]

Hello everyone!

I have Heresies with a Sunfire Junior subwoofer for my system, and they work together beautifully at moderate levels. However, when I get volumes up to a moderately loud level, the room starts to take over - the bass becomes inordinatly muddy and not at all pleasant sounding.

The problem that I have stems from the fact that I live on the second floor of a restored 1925 building with original hardwood floors. Whenever I take a step I can hear the floor either squeek or feel it give a bit. I have a feeling that this is the culprit for the muddy bass response.

To combat this problem, I have the Sunfire sub on spikes, but the Heresies are on their standard risers. I have thought about spiking them as well, but wonder if I would be better off placing the speakers on something more solid and heavy - like the poured concrete "stepping stones" sold for gardens at Home Depot.

Does anyone know if this will work or have any other ideas to "tame my room down?" At any rate, whatever solutions you come up with have to have a high SAF or the idea will not fly with my other half (so no "put your speakers on cinderblocks" answers will work in my situation).

Thanks!

Milton

[DRBILL]

Milton,

This one is going to be a hard one to solve and the solution will not be related to the speakers. In my youth, I was a voicer and tonal finisher for Casavant Freres Limitee ---Canada's oldest and most respected builder of pipe organs. In one instance, we had installed a new instrument that had a 32' rank of pipes in the pedal. In the organ chamber, the pipes sounded properly. In the long nave of the church ---ABSOLUTELY NOTHING. The vast expanse of minimally braced wooden floor (with a church hall below) was acting like a diaphram and effectively cancelling the fundamental. It was the most expensive draft of air ever delivered!

Short of chnging to a better room, I think your options are minimal.

FR BILL+

[formica]

Well i think it's a little premature to assume the structure is the culprit to your muddy bass, which is normally caused by room resonances and not absorptions.

Have walls, floors and ceilings flexing is actually more desirable than rigid surfaces for acoustics (obviously excluding any possible creeks and cracking). The flexing walls will do several things including absorbing the lowest bass frequencies (acting like a bass trap) and make the room appear acoustically larger. Resilient furring used is to replicate this characteristic. Rigid rooms, like a concrete bunker, will reflect all sounds with very little absorption and sound horrid!

You may want to Ethan Winer's acoustic FAQ

Have you got a SPL meter and a test disk? It would be nice to see where your room peaks lie. What are your room's dimensions?

Have you tried experimenting with your sub placement? Most manuals recommend corner placement for a sub, as this will produce the greatest SPL... but the resulting frequency response is often much more peaky (ie: muddy) than placing it mid wall. You may want to look up some papers by Dr. Floyd Toole on speaker placement.

I'd also recommend moving this subject into the architectural forum... as there are quite a few similar threads there and you'll probably get more replies.

Later...

Rob

[WMcD]

For what is worth.

I owned a piano. The music world rested easy when I sold it. However, the buyer and a friend came to give it a test play. She was using a lot of force on the keys. The "room" problem was the old windows resonating in their sash tracks. This was solved by wedging a matchbook in the frame, sash intersection. (These are probably not the correct terms, but the windows were resonating.)

There is some share ware around which will turn your computer into a signal generator. You can feed the amp with continuous tones at frequencies which you type in. You will find real acoustic nodes and anti nodes arising from the dimensions of the room. However, you might also be able to determine whether doors, windows, bookshelves, floors, etc. are part of the problem.

Best,

Gil

[artto]

I think what has been said hits partially on your problem. Yes, low frequency room resonances (and cancellations) are primarily related to room size & proportions. The only way to really control this effectively is to properly size & proportion the room in the first place. The next best effective method is to treat the room acoustically. Ideally, both of these things need to be done. Proper acoustical treatment can actually make-up for SOME of the rooms deficiencies. Some the treatments are somewhat counter-intuitive. Such as trapping (absorbing) low frequencies where they tend to build-up (resonate) most, which is in the vertical & horizontal corners. Doing this will make the low end clearer, more detailed & seem even lower in extension, at the typical listening position, without being muddy sounding. The low frequency build-up in the room corners also typically causes cancellations at the listening position. Therefore reducing the resonances at the room corners, increases the bass in the more central areas of the room. It also increases the quality of the low end sound.

In your case where it sounds like the floors/ceiling (and possibly walls) may be somewhat weak due to their age & construction (building codes were different back then), you may have a situation where, when the music is played louder, it is enough to physically vibrate the room surfaces in such a way that essentially turns the room surfaces into a passive sound radiator. In building professional studios they go to great lengths to make the walls & floors as rigid as possible. For instance, the liberal use of stringers between floor & ceiling joists & wall studs is often done to stiffen up the surfaces to minimize vibration and resonances.

It would take quite a few of those garden stepping stones to add significant mass to absorb low frequency sound. And if your floors are already weak, Id be careful as to how much load you put on the floor unless you are sure it can support it (like a rehabbed warehouse). I like the spikes. They are not heavy. And they essentially achieve similar results through mass loading. I use 3 spikes where I can. This increases the effective mass loading even more.

Welcome to the Forum.

[Lone Palm]

Try The Heresys without the sub. I've never heard a system using a sub-woofer that didn't sound muddy and un-natural,even in a Klipsch dealership.

[prodj101]

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On 11/16/2003 7:24:51 AM Lone Palm wrote:

Try The Heresys without the sub. I've never heard a system using a sub-woofer that didn't sound muddy and un-natural,even in a Klipsch dealership.

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A subwoofer that has been calibrated properly will not sound muddy or un-natural. Many people seem to like to turn up the sub to un"neutral" levels rather than having it just fill in the lowest of bass.

[DRBILL]

I am going to be hard-headed about my original assesment. The muddy sound is coming from the second and third harmonic series out of balance from the absorption of the fundamental by your diaphram floor.

Lose the subwoofer. Enjoy the pure sound of your Heresys, light on the bass as they might be. That last octave doesn't occur in most music anyhow.

For one day I added a sub to my Klipschorns. I couldn't get it out of there quick enough.

Father Bill+

[DRBILL]

Sorry, I fogot to ask you. Are your speakers in the corner. If not, why not? This may solve everything.

FATHER BILL+

[WMcD]

Reading this again, I think Formica has a very good idea. Alter the placement of the sub.

At least it is a cheap experiment.

Best,

Gil