Blu-Tack – Alternatives and speaker coupling / de-coupling

[WmAx]

Why don't you do it correctly. Use a dial indicator (affixed to the wall or any surface with a lot of mass) to the top portion of the speaker cabinet. Im sure doing the experiment in the proper fashon will yield similar results. I also did not measure woofer excursion, I played a random tone burst with frequency content from 20-20k. Power input was around 40W rms.

I sweeped several frequencies in the lower range. A dial indicator is not needed to see nearly 0.4mm(0.015") of an object, next to a ruler. You would have had to meet one of the conditions I set in the last reply, in order to meet that level of movement.

Why don't you do the calculation. Lets assume the cabinet does move 0.015". The amount of movement, needs converted to total energy the amp is wasting to move the enclosure. Assuming an 80lb cabinet, can you please run the numbers and tell me how much energy it takes to do this?

Uh-hu. Whatever.


-Chris

 

[MacManNM]

I sweeped several frequencies in the lower range. A dial indicator is not needed to see nearly 0.4mm(0.015") of an object, next to a ruler. You would have had to meet one of the conditions I set in the last reply, in order to meet that level of movement.

Not very scientific to say the least.

Uh-hu. Whatever.


-Chris

So I will assume you either won't or can't perform the calculation.

 

[WmAx]

Not very scientific to say the least.

Whatever you want to believe, man, go for it. You like to [1], don't you?

So I will assume you either won't or can't perform the calculation.

[1]Choose the answer that best fits your perception. Like always.

-Chris

 

[mtrycrafts]

The spikes are pretty much for a carpeted floor. They help prevent movement of the speaker (newtons third law of motion). This movement primarily occurs when playing the deepest/loudest bass notes, where the excursion of the woofer is the greatest.

Preventing the speaker from moving improves imaging, and will increase bass.

The bookshelves don't really need them because they really shouldn't be playing those deep bass notes, and usually the friction of the rubber feet on a hard surface is enough to keep them from moving.

HUH??? If your speakers move that much to affect imaging, at low frequencies to boot, get rid of that junk and get some real speakers. Too funny to take seriously.

 

[mtrycrafts]

There is no bass imaging. It improves midrange and high frequency, by the cabinets not moving around. Bass shakers are sub sonic. Off axis response can vary quite a bit, a few mrad of movement could change the imaging drastically.

Oh, good, you know this. But, back to the imaging, you really thinks imaging is affected by miniscule movements? I hope your head is locked in position then as you will move inches, without knowing it. LOL. Get better speakers. My boombox doesn't move at all.

 

[MacManNM]

HUH??? If your speakers move that much to affect imaging, at low frequencies to boot, get rid of that junk and get some real speakers. Too funny to take seriously.

Right, my McIntosh XR-16's are junk speakers. I didn't realize that. But thanks for the advise. I’ll take it under serious consideration.

 

[MacManNM]

Oh, good, you know this. But, back to the imaging, you really thinks imaging is affected by miniscule movements? I hope your head is locked in position then as you will move inches, without knowing it. LOL. Get better speakers. My boombox doesn't move at all.

Do you even know how much a m radian is? Or what it means for that matter? What about the radiation patterns of speakers? How about off axis response?

 

[mtrycrafts]

So I guess you are saying we could mount our speakers on ball bearings and it wouldn't make a difference?

Why cling to such flimsy parallels? Where is your car example, or your camera paradox?


Also any movement of the cabinet robs performance from the setup.

How so??? Please supply sme evidence, thanks.

How many watts does it take to move a 80 lb speaker cabinet 0.015" which is a little more realistic number than the one you came up with, since I just measured it.

And how many watts you need to move your head 1" or much more?
Please.

When the coefficient of friction is included this goes up. I didn't do that calculation because there are too many variables to mess with.

This alone is worth using spikes or coupling the cabinet to the floor.

Your assumptions. That is OK too.

 

[MacManNM]

So I guess you are saying we could mount our speakers on ball bearings and it wouldn't make a difference?

Why cling to such flimsy parallels? Where is your car example, or your camera paradox?


Also any movement of the cabinet robs performance from the setup.

How so??? Please supply sme evidence, thanks.

How many watts does it take to move a 80 lb speaker cabinet 0.015" which is a little more realistic number than the one you came up with, since I just measured it.

And how many watts you need to move your head 1" or much more?
Please.

When the coefficient of friction is included this goes up. I didn't do that calculation because there are too many variables to mess with.

This alone is worth using spikes or coupling the cabinet to the floor.

Your assumptions. That is OK too.

I did the math, I did the measurement. The measurement along with the rough calculation show an audible effect. If you care to do it also, then go ahead. This is what the numbers say. If you disagree please provide some data to back it up. Also, let it be known, this was done on carpet, not a hard floor with rubber feet,

 

[mtrycrafts]

Not very scientific to say the least.
So I will assume you either won't or can't perform the calculation.

Remember??? You are the one suggesting ball bearing, right? You didn't like his results, it seems. It didn't move. And even if it moved a 1/64" What is your claim with that amount of movement? What did you do with your head movements many magnitudes more???

 

[MacManNM]

Why cling to such flimsy parallels? Where is your car example, or your camera paradox?

I can give you the data from the camera if you wish. Paradox? Please use words correctly.

 

[WmAx]

I did the math, I did the measurement. The measurement along with the rough calculation show an audible effect. If you care to do it also, then go ahead. This is what the numbers say. If you disagree please provide some data to back it up. Also, let it be known, this was done on carpet, not a hard floor with rubber feet,

Ah, on carpet, and you did a 20-20k sweep, and you completely ignore my caution of effect of the coupling resonance frequency. You did specifically meet one of my stated qualifications[in the prior posts] to get such a measured movement. I specifically avoided such error[and I warned about it several times in the thread] in my test.

BTW, in your worst case scenario[with a severe undamped resonance of the coupling] of movement measurement, this[extreme] movement, does not even equal 1/4 of the wavelength of 20kHz. What, exactly, do you propose, that it's doing to high frequencies?

BTW, you should refer to Richard D. Pierce's newsgroup post on speaker coupling(R. Pierce is a veteran loudspeaker designer and consultant, outsourced by several corporations]:

http://groups-beta.google.com/group/rec.audio.high-end/browse_thread/thread/95cdc48153f2e0c8/a9a9946daa5b3e66?q=speaker+movement+suspended+in+air&rnum=2&hl=en#a9a9946daa5b3e66

-Chris

 

[MacManNM]

Remember??? You are the one suggesting ball bearing, right? You didn't like his results, it seems. It didn't move. And even if it moved a 1/64" What is your claim with that amount of movement? What did you do with your head movements many magnitudes more???

First off using a ruler and looking at something does not work. Ever hear of parallax error?

Second, the issue is the large amount of energy wasted in the movement of the cabinet.

Third, moving your head does not change the effective output of the speaker.

 

[WmAx]

First off using a ruler and looking at something does not work. Ever hear of parallax error?

1. The units are plenty big for me to see far under the distance you claim. 2. It was also videotaped with a tripod mounted camera with a macro lens attached, and this video inspected afterwards.

Second, the issue is the large amount of energy wasted in the movement of the cabinet.

The massive 2% loss of cone movement to produce bass, at that specific coupling frequency? Or the far under 1 percent loss at the other low frequencies?

-Chris

 

[MacManNM]

Ah, on carpet, and you did a 20-20k sweep, and you completely ignore my caution of effect of the coupling resonance frequency. You did specifically meet one of my stated qualifications[in the prior posts] to get such a measured movement. I specifically avoided such error[and I warned about it several times in the thread] in my test.

BTW, in your worst case scenario[with a severe undamped resonance of the coupling] of movement measurement, this[extreme] movement, does not even equal 1/4 of the wavelength of 20kHz. What, exactly, do you propose, that it's doing to high frequencies?

BTW, you should refer to Richard D. Pierce's newsgroup post on speaker coupling(R. Pierce is a veteran loudspeaker designer and consultant, outsourced by several corporations]:

http://groups-beta.google.com/group/rec.audio.high-end/browse_thread/thread/95cdc48153f2e0c8/a9a9946daa5b3e66?q=speaker+movement+suspended+in+air&rnum=2&hl=en#a9a9946daa5b3e66

-Chris

It wasn't a sweep it was a multi frequency burst tone produced by an Agilent arb.

I guess music doesn't have content from 20-20k, we can just put a notch filter on the resonances.

 

[MacManNM]

1. The units are plenty big for me to see far under the distance you claim. 2. It was also videotaped with a tripod mounted camera with a macro lens attached, and this video inspected afterwards.

Is it that hard to do it right?

The massive 2% loss of cone movement to produce bass, at that specific coupling frequency? Or the far under 1 percent loss at the other low frequencies?

-Chris

Again, I state do the calculation pick a random number for movement.

 

[WmAx]

It wasn't a sweep it was a multi frequency burst tone produced by an Agilent arb.

I guess music doesn't have content from 20-20k, we can just put a notch filter on the resonances.

You excited the coupling frequency with your multi frequency burst. A coupling frequency that would not be so underdampened, in a proper isolation platform, btw. So far as energy loss in this narrow band....it's miniscule...and it is easily reduced with a proper execution of an isolation system, that is properly dampened.

If I had[wrongly] targeted a coupling resonant frequency, I could have achieved a measured movement that is magnitudes higher, as well.

-Chris

 

[WmAx]

Is it that hard to do it right?

That hard to do what? It certainly was not hard to see small movement on the scale you claimed. But feel free to pretend it was, if you prefer.

-Chris

 

[MacManNM]

You excited the coupling frequency with your multi frequency burst. A coupling frequency that would not be so underdampened, in a proper isolation platform, btw. So far as energy loss in this narrow band....it's miniscule...and it is easily reduced with a proper execution of an isolation system, that is properly dampened.

If I had[wrongly] targeted a coupling resonant frequency, I could have achieved a measured movement that is magnitudes higher, as well.

-Chris

So your saying that your case is true as long as the content of the material doesn't have certian frequencies?

 

[WmAx]

So your saying that your case is true as long as the content of the material doesn't have certian frequencies?

If you have a severe underdamped coupling resonance, the motion will be larger, just as I specified in the first posts to this thread, and as specified in the Richard D. Pierce posts that I recently referenced. If you have this severe underdampened coupling resonance, it will be isolated to a narrow band, and be excited when the spectrum is stimulated by audio program that contains this frequency. The audiblity of such, requires that the movement be large enough to actually cause a frequency response anomoly(in the bass at this frequency), or that it be large enough to cause high frequencies to modulate their phase relationships, due to the surface moving a significant amount relative to their wavelengths.

-Chris