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Has anyone had experiences good or bad with speaker isolation or isolation in general ?

hi
i have been enjoying buying and listening to hifi for some 35 years now and have seen many items come and go.I have also been interested in the audio cable discussions and i agree that cables do make a difference how much of a difference is a very individual, and a system dependent situation. There has been nothing that has got me so excited and improved the sound of my system that has ever made me want to really share it with fellow audiophiles until i started to try various isolation products.With so much choice from affordable to very expensive i found the hole subject very confusing and i did not know where to start. After trying lots of various products all shapes and sizes with very different results i decided to read reviews which is something i do not usually do to get some advise.I read a review on the Townshend audio seismic podiums they are isolation platforms that go under your speakers .This company is very famous for isolation ideas and have been around some 50 years based here in the UK they also had a factory in the USA back in the 1980s. I contacted Nick at Emporium hifi  and he agreed to install a pair for me so i could have a listen. My speakers are sound-lab dynastats which i use in quite a small room but with the adjustments give a nice sound. After installing the podiums we both sat down with jaws hitting the floor these podium things completely transformed the sound of my system to absolute perfection. After all this time trying various products under my equipment i have now isolated my speakers and the sound quality is exactly what i believe we all are chasing, my sound-labs are now transparent no more bass problems i have just got one big 3D sound stage the dynastats are now very open with deeper much better bass everything is perfect. I now believe isolating your loudspeakers is the first port of call i was so impressed by the Townshend audio seismic products i now sell them as i have never come across anything that has given my system such a great upgrade , the sound is the same as before but now its just so much better its playing deeper bass but tighter much more resolution and no boom , the midrange is so much more human sounding realistic and spacious with the top end so refined and perfect , is anyone using podiums and had the same experiences i would love to hear from you thank you john 
mains
kennythekey
593 posts
 
I have eliminated the oscillation with just the subs on and the arm down and stationary, but if I'm playing music through just the subs, I will get oscillation raising the sub amp volume.

i can play my whole system up to my normal listening levels and with my subs dialed in. The benefits of the subs are big and I have resolved my goal of adding fill-in, so my system sounds better than ever. If I do raise the sub amp volume past a certain level while playing music, the oscillation will kick in. So, I have effectively tamed the oscillation, but even though I don't hear it normally now, I wonder if it isn't affecting my sound in some less than obvious way? I also want to know what's causing it to begin with, as the mechanical feedback theory can be simply defeated by phase reversal.
Kenny
geoffkait's avatar
geoffkait
23,365 posts
 
Just to close the loop as it were lol for inner tube isolation, the reason this DIY technique doesn’t work all that well compared to other techniques IMHO is largely due to the incorrect assumption that isolation is supposed to be "floating on air" whereas real isolation is obtained by the physics of the mass-on-spring behavior of most isolation devices/techniques, where the resonant frequency of the isolation system is equal to the square root of the total spring rate divided by the total mass. The resonant frequency determines the frequency of vibration where the isolation begins. The equation for Fr shows the advantages of high mass and minimizing the number of springs as well as spring rate per spring. That’s how I got the resonant frequency of my Nimbus air spring platform down to about 0.5 Hz (hel-loo!)- my using high mass and a single air spring (!) of the correct geometry and spring rate. A single air spring also allows for much greater horizontal and rotational isolation in addition to vertical isolation.

For air systems, bladders, airsprings, inner tubes, there is what is called a design (based on pressure under the load) for which they behave as true springs. If the air bladders, whatever are not filled enough or filled too much their spring rates will be incorrect. In addition there is the issue of air leakage through the rubber fabric. A much better DIY isolation technique that avoids the pitfalls of inner tubes is bungee cord suspension, a technique that obviously has challenges of its own.

bdp24's avatar
bdp24
9,966 posts
 
Long ago I read that a spring isolation system should not be employed with a turntable already having a spring-type suspension, such as the original VPI HW-19, the Linn Sondek, the Oracle, Thorens, and all the other floating-suspension tables, all the way back to the Acoustic Research. That is because the springs in the turntable and the springs in the isolation platform interact with each other in a delirious fashion. Non-suspended turntable designs, such as current VPI’s, Regas, Well Tempereds, etc., of course have no such problem.
kennythekey
593 posts
 
bdp24 - It makes sense that doubling up on springs would create unstable results. Perhaps, like driving on a washboard surface?

My table is non-suspended and I installed the new spring based feet. I can tell you that my sound is smoother, the background is blacker, and bass is better. However, this did not really do anything for the lurking oscillation that I can reproduce from my subs. My last puzzle piece I will go after is my cartridge. When I get my loaner cartridge to test it may reveal something.
Kenny
geoffkait's avatar
geoffkait
23,365 posts
 
kennythekey
bdp24 - It makes sense that doubling up on springs would create unstable results. Perhaps, like driving on a washboard surface?

its not like driving on a washboard surface at all. It’s like driving down the road on two sets of shock absorbers that have the same spring rate. The ride would be chaotic and bumpy, but not bumpy like a washboard, bumpy like an aircraft going through heavy turbulence, a series of unpredictable lurches up and down.


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