Speaker Cabinet Vibration

So, I posted recently about reducing "room boom" and received some great advice about moving my listening position and adjusting speaker placement. Tried it, it helped greatly, and I'm much happier. One unexpected and significant improvement happened when I switched the left speaker to the right side position, and vise versa. (The speakers are some nicely restored KEF 104/2.) The left side always seemed louder (or at least to have more bass), and since it was near a corner I figured that was causing the problem. It also seemed like the soundstage was pulled towards the right for some reason.

Aside from working on treating my room acoustics, I've been reading up on isolation and vibration control. I downloaded a "vibration measurement" app for my phone (I know, very crude...not very accurate) and have been measuring everything. When I set it on top of my right speaker (the one not near a corner) the meter showed very minimal vibration. However, when I put it on the left speaker that was near the corner, it went crazy! So, I figured the corner placement must have something to do with it. Eventually I decided to switch the speakers to see if the corner positioning was causing all the vibration. When I did, the speaker that didn't show any vibration before didn't have any now that it was in the corner. The other speaker, the one that was earthquaking, was still vibrating at the same measured levels even though it was out of the corner area. What was totally unexpected was when I sat down to listen. The soundstage was now perfectly centered, the bass was more focused and clear, and it just sounded better.

So my question is: do I need to worry about controlling the speaker that is vibrating? I don't hear anything rattling around inside. I don't hear anything that is "off" when listening to it. I have tightened up the screws that mount the speaker housing to the cabinet. I have tightened up the binding post screws from the inside. I don't see any cracks or separation on the outside of the cabinet. Without ripping the cabinet apart to get inside, what could be causing the vibration? Both speakers are spiked, leveled, and are very solid. Can this vibration be audibly measured, since my ears can't distinguish anything? Would it sound even better if it wasn't vibrating? It doesn't seem like a big deal when listening, and I don't want to turn it into one out of sheer audio-paranoia.

Any help, advice, or suggestions are always welcomed and appreciated!

 

Speakers should not be louder than the other in a pair. If so, then something is electrically wrong. It could be a bad driver, connection, or crossover component if it comes from the speaker. Typically volume imbalances between channels are either caused by the hearing of the listener who has some hearing loss in one ear, whether temporary or more permanent, or by the amplifier. Many amplifiers have volume controls that have channel imbalance at their lower settings. Then there is room gain and speaker cabinet placement.

Cabinet vibration is a major concern of speaker makers on their better speakers. It is unusual to have one speaker of the same type and run make more noise that way than the other. Two common sources are driver to cabinet interface, and other accessories such as binding post cups, ports, and crossovers. You have already tightened the drivers. The other source of vibration is from the speaker cabinet to the floor. You might have that taken care of if the spikes are solidly placed on all four corners. So that leaves the crossover to the cabinet interface and the speaker bracing and the joints of the speaker cabinet panels themselves. The only fix for the cabinet panel joints is glue poured into / over it and letting it set-up overnight.

Maybe that info helps to track down the vibration. The level imbalance sounds odd unless it is from the amplifier and just misdiagnosed.
-Bill

 

You need to worry about 1 spkr being defective. Without using a mono signal, your approach is aimless.

 

After tightening all the screws, does the one speaker still show a lot more vibration? And if so, can you be a lot more specific about how you are doing this test? (Pictures!)

 

Thanks Bill. I appreciate your help. As I mentioned, with the speakers in their current positions, they both sound great and at equal volumes now. Maybe it was just my ears... The center image of the soundstage is in focus and at times, it's as if the speakers just disappear...that's never really happened to me before. Anyway, when I place my hand on top the speaker that's "vibrating," I can't really notice anything different than the other speaker. Thanks for the list of options, I'm sure they will prove useful.

 

After tightening things up, it's shows about the same amount of vibration as before on the meter app. As for the test...hmmm... Well, I was just curious about vibration and isolation of equipment and stuff because I need a new (bigger) equipment rack, so I wondered how I could tell if I had any vibration issues. I figured the phone app would be the quickest, cheapest way to get started. It's called "Vibration Meter" on the Google app store. It looks like a simple grid with an X plane and a Y plane. You place the phone on top of whatever you want to measure, and it gives you a read out of how things are vibrating in the X,Y, and Z planes. I don't think the free app lets you take screenshots or save anything. Also, I don't know how to take screen shots with my phone (I'm pretty stone age when it comes to phones)...I don't have another camera right now. I do agree, pictures are always helpful! I put the phone on one speaker, then the other, and compare. On every surface I have used it on, there is minimal vibration...except with the one speaker. As I mentioned, I can't hear it, or feel it...it's just that the meter says it's there. I know it's not the most accurate thing it the world, but it's obviously trying to tell me something. Anyway, the speaker is not dancing across my floor, so that's a good thing.

 

It's an audiophile poltergeist! If you rub the top of the speaker, maybe he will grant you three audio wishes ha ha

 

Without using the same mono signal for both, you are spinning your wheels. With your helter skelter methodology, you might as well try an exorcism.

 

When I owned lower and medium quality speakers, I improved the cabinets by installing internal bracing. Essentially it's pieces of dowel, glued across the mid-points of the cabinet sides. One (or two) front to back is the most important, with side-side also important. Top-bottom if you can do it. When I did it I removed the woofer (so top-bottom was not possible). If access is by removing the back panel, it could be braced by gluing a strip(s) of wood onto the inside front and inside back panels.

 

Thanks! Hmmmm....3 wishes? A blond, brunette, and redhead....on my couch enjoying some tasty tunes! A man can dream!!! Hahahahaha

 

Can you explain how to do the mono thing? I really have no idea. What will it help do? I'm just trying to figure out why one speaker is vibrating more than the other. I really don't have a methodology, obviously. Ha! Helter skelter would describe most of my adolescence and adulthood!

 

Thanks for your advice! There is some bracing in the middle of the cabinet, going side-to-side. I can see it through the port on the front...haven't got in there to really inspect anything, but it feels pretty solid.

 

With a mono signal both spkrs receive the SAME SIGNAL. This isn't true in stereo, making it much more difficult to analyze the problem. Does your amp have a mono switch? If so, use it.