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Deusx3

Custom decoupling platform for my new RF-7II's

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I just got done making some homemade coupling/decoupling pads for my new Klipsch RF-7ii's. As I have slightly uneven and hollow tile floors over concrete (which has caused sonic issues with all of my floorstanders in the past), this is an upgrade I have been very curious about trying.

To start, I cut 1.5" thick granite plinths, then fitted natural cork feet and a thick layer of blue-tack to decouple the granite and from the floor. I then built new bases for the speakers out of 3/4" MDF, adding coupling spikes to all four corners.

My goal was not to isolate the speakers from the floor, but to strike a balance between coupling and decoupling, reducing or eliminating unwanted reverberations from the floor, while providing enough cabinet stability to reduce extraneous cabinet movement.

I tried to be as objective as possible (while still being completely lazy), so I did some before / during / after listening to a handful of tracks that I use for reference listening. No mics / spectrometers used, only my ears.

Upon first impression: improved mid range definition and tightness in the bass. When listening with only one speaker stand done, I noticed that the imaging pulled toward that speaker (without calling attention to the speaker itself). To be sure, I adjusted the MLP to account for the increased height of the stands, and noticed no difference in the sound. Especially at loud (over reference) volumes, I have noticed that certain tracks that we're previously harsh in my (very lively) room are much more tolerable, even for extended listening periods.

Overall, I am quite pleased with the results so far! Pictures attached for anyone interested.

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Neat experiment, you had to do something if the hollow floor was causing noise problems.

Try both speakers and if needed try a few other ideas, it sounds like it's working but you could always slip a little more of something to cushion between the granite and floor as a test. I would think the granite is a good enough base, the need may be to disconnect it from the floor.

 

Just guessing, but it would be easy to try, except for moving a heavy speaker. Good luck but it sounds like it's working.  

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Interesting design and execution of a concept.

 

Is your thinking the granite would absorb energy produced by the speaker enclosure?  If so, could a rubber mat of some kind used, then place the speaker with spikes on it?

https://www.lowes.com/pd/Gray-Anti-Fatigue-Mat-Common-4-ft-x-4-ft-Actual-49-21-in-x-49-21-in/3111467

874839002142.jpg

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8 hours ago, wvu80 said:

Interesting design and execution of a concept.

 

Is your thinking the granite would absorb energy produced by the speaker enclosure?  If so, could a rubber mat of some kind used, then place the speaker with spikes on it?

https://www.lowes.com/pd/Gray-Anti-Fatigue-Mat-Common-4-ft-x-4-ft-Actual-49-21-in-x-49-21-in/3111467

874839002142.jpg

If you try these pads, you should find out if you have a Harbor Freight near you.  You should be able to pick these up for closer to $7-8.  They also have an inexpensive rolled foam rubber mat for very cheap with is much firmer and could support the weight without too much compression.

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Creative!  Your floors look like some of mine.  Do you have loose tiles?  If not, how do your speakers cause a resonance in tiles, or a concrete slab of that mass?

 

Do you have area rugs?

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14 hours ago, dtel said:

Neat experiment, you had to do something if the hollow floor was causing noise problems.

Try both speakers and if needed try a few other ideas, it sounds like it's working but you could always slip a little more of something to cushion between the granite and floor as a test. I would think the granite is a good enough base, the need may be to disconnect it from the floor.

 

Just guessing, but it would be easy to try, except for moving a heavy speaker. Good luck but it sounds like it's working.  

I wanted to be careful not to over-dampen the sound, as I love the incredible detail of the horns. Using more cushion would promote less stability, so it's a  trade-off. Indeed a PAIN to move, but that's ok, as I've dialed them in pretty well as it is.

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5 hours ago, pzannucci said:

If you try these pads, you should find out if you have a Harbor Freight near you.  You should be able to pick these up for closer to $7-8.  They also have an inexpensive rolled foam rubber mat for very cheap with is much firmer and could support the weight without too much compression.

Compliant material decoupling is a funny thing. Even soft or squishy materials can tend to resonate under certain frequencies. In addition, the much softer materials like foam have less lateral stability compared with cork or blue-tack. If you wanted to totally isolate from the floor, sorbathane is your best bet-- just note that it will mute / over dampen the sound.

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44 minutes ago, John Albright said:

Creative!  Your floors look like some of mine.  Do you have loose tiles?  If not, how do your speakers cause a resonance in tiles, or a concrete slab of that mass?

 

Do you have area rugs?

 

No area rugs, and no loose tiles, per se. The actual mud (mortar) that was used to ahere the tile to the concrete is not 100% uniform. You can test this by rapping on the tile with a hard (plastic or wood)  object-- different sounds are produced depending on where on the tile you knock. In addition, the tile is a "natural" or rough finish, which means that it is not perfectly flat.

 

Imagining for a moment that the tile was perfectly flat, though, and had no mortar inconsistency, the concrete slab will still produce sonic interference. Sound waves actually travel through concrete very easily, and LF transients can not only produce unwanted vibrations in the structure of a house/building, but cause resonance in the speaker cabinet at certain frequencies (HF and LF).

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6 hours ago, pzannucci said:

If you try these pads, you should find out if you have a Harbor Freight near you.  You should be able to pick these up for closer to $7-8.  They also have an inexpensive rolled foam rubber mat for very cheap with is much firmer and could support the weight without too much compression.

Thanks for the heads up, I'll look for that.  I usually buy those pads 4 for $20 at Lowes and I cut those to fit and put a lot of speakers on them.

 

This is a good thread and I like what the OP is doing, it's just I don't always understand what is happening with pedestal materials, and why a certain material is desirable over another, in this case granite vs rubber mat, or even rubber feet.

 

I have also seen granite cut to fit and put on top of speakers with my same quandary, I'm not sure what the goal is of the extra weight and choice of material.

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4 hours ago, Deusx3 said:

 

Imagining for a moment that the tile was perfectly flat, though, and had no mortar inconsistency, the concrete slab will still produce sonic interference. Sound waves actually travel through concrete very easily, and LF transients can not only produce unwanted vibrations in the structure of a house/building, but cause resonance in the speaker cabinet at certain frequencies (HF and LF).

 

A steel supported concrete slab has a resonant frequency typically between 3 and 10 Hz.  Reinforced concrete would have to be similar if deflection criteria are met.  The typical slab-on-grade house floor (as is mine also) would be both stiffened and damped by the contact with the (crushed) stone on which the slab was poured.  You may well have room resonances, but they are unlikely to be connected to your floor system.

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5 hours ago, wvu80 said:

I have also seen granite cut to fit and put on top of speakers with my same quandary, I'm not sure what the goal is of the extra weight and choice of material.

 

With mine there was two goals.  

 

1.  When an enclosure is propped up with a thick carpet, basically thousands of long and extremely flexible fibers, at lower frequencies the entire enclosure can literally move back and forth.  Basic laws of physics, with every action there is a reaction.  An ultimax 18" sub has like a pound and a half of moving mass.  You can't move that much weight back and forth that fast at that much xmax without there being a reaction, it is easily observable when on carpet.  Granite kills this movement.  

 

2. The top of granite is typically polished to a mirror finish.  Most people think this is bad for home theater but actually it's awesome.  Basically the glow from the projector screen hits the granite then bounces up to the ceiling rather than illuminate the subs.  It's actually way better than most any other finish you could choose.  

 

Whether these advantages transfer to this situation is a different story but granite on top of subs under the screen is definitely awesome.  My 300 pounds of granite definitely stabilizes four ultimax 18's to where they are rock solid.  Literally.  

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