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Post by karatestu on Feb 6, 2022 12:27:35 GMT
I never took this very seriously until recently. I don't know why but after years of knowing about and reading people rave about Townshend isolation products I suddenly became interested in trying the concept out. Maybe it was a diy thread on thd Wam that finally got my arse into gear.
No disrespect to Max (RIP) but I would never consider paying so much especially as I had no idea if they would actually make any difference. The idea of speakers not being heavy and solid with rigid coupling to the floor was hard to swallow. It gets installed in your brain that speakers and driver baskets should not be allowed to move.
The diy efforts of people finally persuaded me to have a go at making something. Some had gone to the trouble and expense of calculating what springs they needed for the weight of their speaker and making a clone of the current Townshend offering. Being a tight arse I decided to give the inner tube and platform concept a go. I believe air isolation was the way Townshend designs started. People were still raving about the inner tube concept.
So I have tried it and it cost me nothing as I had two old inner tubes and wood for platforms already.
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Post by MartinT on Feb 6, 2022 12:51:07 GMT
I went along the same journey, Stu. I first dipped my feet with the washing machine feet recommendation between my tiled floor and the heavy Ushers. It worked well. Then I had the chance to have a set of Podiums custom made for the Ushers via David Brook of MCRU. I jumped at the chance. They work spectacularly well, with greatly improved and tighter bass clarity and better soundstaging. The speakers just swing gently, if prodded, at about 1Hz.
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Post by karatestu on Feb 6, 2022 13:18:17 GMT
Well Martin, I wasn't prepared for the gravity of the outcome of this experiment - it was a good job I was sat down  I can't quite believe the level of improvement in the music coming from my speakers. As you say Martin, bass is considerably tightened up. I have found improvement throughout the audio frequency range. I suspect some of that is down to the bass tightening up but I also found such things as Donald Byrd's trumpet really soaring like a bird and the speakers disappearing even further. Timing has improved and this was evident with Stewart Copeland's kick drum sounding faster (Iknow that is impossible). It is safe to say I am really blown away by the effect it has had and it cost me nothing but time and my jaw hitting the floor. |
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Post by petea on Feb 6, 2022 13:40:17 GMT
I use a lot of Townshend isolation products, including Podiums, and find they make huge improvements.
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Post by MikeMusic on Feb 6, 2022 13:58:36 GMT
The Townshend stands made my speakers complete
They were good but seemed to have something missing until placed on the stands
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Post by karatestu on Feb 6, 2022 14:32:28 GMT
I didn't realise there were so many Townshend users here. This is certainly a good place to talk about such things. I mean no disrespect to the brand it's just way above any budget I have for such things.
We have discussed such things on hfs and I have managed to spur three or four members to try the inner tube thing. Some were very suspicious of the idea and the engineers wanted to know why it should work.
In my case I suffer from suspended wooden floors ( joists and tongue and groove) in my living room at home and at work where I do 99% of my diy stuff. At the farm my system is in my old bedroom and is upstairs. When I used to go in the room below I could hear the bass much louder than the rest of the frequency range and distorted. My floor was clearly playing along with music. I did an experiment with my hand on the floor before and after. Before implementing the inner tubes the floor could be clearly felt vibrating, I could feel every bass note, kick drum, share drum.
After installing the tubes I could feel absolutely nothing in the floor. Going downstairs into the room below and now the bass was not distorted and was the same volume as everything else and seemed to be coming down the stairs rather than through the floor. So it works absolute wonders on my suspended wooden floor.
Some have expressed scepticism concerning any claimed improvement on a downstairs concrete floor. I can't comment on that as I have no solid floors to try it on. Some say it improves things even on solid floors.
If I may ask users here - what kind of floor do you use your speaker isolation on and what was the magnitude of improvement you witnessed ?
Thanks, Stu
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Post by MartinT on Feb 6, 2022 14:57:43 GMT
I think I've mentioned that my music room has a ceramic tiled floor on ground level (it's a converted double garage). Previously, I used washing machine feet but now I have the speakers on Townshend Podiums. The difference is startling and the Podiums most certainly do work on a solid floor.
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Post by MikeMusic on Feb 6, 2022 15:19:21 GMT
Speakers and system racks on carpet, underlay and concrete here
Value for money on Townshend stands is high
Mine were 2nd user, half price
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Post by John on Feb 6, 2022 15:57:30 GMT
Joists with plywood then carpet for my floor. The listening room is in a loft conversation
Bass drivers are suspended by wire as they can produce a lot of energy that the other drivers are best isolated from
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Post by John on Feb 6, 2022 15:59:51 GMT
I think I've mentioned that my music room has a ceramic tiled floor on ground level (it's a converted double garage). Previously, I used washing machine feet but now I have the speakers on Townshend Podiums. The difference is startling, and the Podiums most certainly do work on a solid floor. I heard Martin speakers before after fitting the podiums and vouch for the difference they make in his listening room |
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Post by karatestu on Feb 6, 2022 20:29:59 GMT
Thanks for answering my questions.
If using standmounts do you think the isolation would work better if between the stand and speaker rather than stand and floor ?
In my mind it would likely be better due to keeping vibration out of the stand.
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Post by MartinT on Feb 6, 2022 20:40:26 GMT
Always on the floor, I think. Treat the speaker and stand as a combination to be isolated.
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Post by karatestu on Feb 7, 2022 8:33:31 GMT
Always on the floor, I think. Treat the speaker and stand as a combination to be isolated. But don't stands release vibrational energy just like everything else ? And if so wouldn't it be better if they were taken out of the equation as it were? I often read about how different constructions of stands sound different which in part will be to do with how they react to vibration ? Thanks, Stu |
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Post by MartinT on Feb 7, 2022 9:26:57 GMT
I guess the only thing to do is try it both ways, which won't work for all solutions.
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Post by karatestu on Feb 7, 2022 19:17:43 GMT
Yeah, suck it and see it shall be.
Thinkng about isolating the drivers from their enclosures too. That's much easier with a mid bass which is mounted horizontally (firing up).
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Post by MartinT on Feb 7, 2022 20:29:50 GMT
You'll need to think about sealing the driver against the cabinet to prevent airflow through the gap, otherwise you'll lose the effect of the cabinet (and a lot of bass).
Perhaps thick draught excluder strip?
Roksan had a speaker with the tweeter hung on springs.
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Post by karatestu on Feb 8, 2022 6:00:25 GMT
Yes it must be sealed and that can be done with some rubber or other vibration isolation material. As long as the magnet weighs much more than the cone then spl is apparently reduced by something in the order of 0.2dB and the reduction is linear ie across the whole frequency range not just bass.
Here is a copy of a white paper I found. The graphs have not copied over but the text describes them quite well. I think it disproves a few myths and I am happy enough with it's findings to give the idea a go.
The Floating Baffle Loudspeaker
Introduction
The conventional moving coil loudspeaker drive unit comprises of a signal current carrying voice coil attached to a diaphragm and immersed in a magnetic field produced by a permanent magnet. Fluctuations in the current create a varying force that acts between the coil and the magnet to produce motion of the diaphragm. It is this diaphragm motion that results in the creation of the sound field.
Because the force acts between the voice coil and the magnet, the magnet will be forced to try to move backwards in opposition to the forward motion of the diaphragm. It is a commonly held belief that the only way that the diaphragm motion can be an exact facsimile of the signal current is if the magnet is held by a perfectly rigid body so as to remain motionless. This is obviously a theoretical ideal.
There is however an alternative ideal. If the magnet is suspended so as to allow totally free movement then its motion will be an exact facsimile of the diaphragm motion, simply reduced in magnitude by the ratio of the cone mass to the magnet mass. Clearly if the magnet mass is infinite, then its motion is zero and both ideals converge to give the same resultant diaphragm motion.
Now let us consider the consequences for these two alternative theories under real world, non-ideal conditions.
The Freely Suspended Magnet vs. The Clamped Magnet
With a conventional moving coil drive unit, the ratio of magnet mass to diaphragm mass is typically in the order of 100:1 and so if the magnet is allowed to move freely then it will do so with a magnitude 1/100th that of the diaphragm. The effect upon the diaphragm will be to reduce its motion by one part in 100, or 1%, but this will be constant for all frequencies and all levels. This is simply the equivalent of reducing the efficiency of the drive unit by 1% or approximately -0.1dB.
To test this assertion, the motion of the diaphragm and magnet of a fairly typical 5” drive unit was measured under two conditions by attaching a miniature accelerometer and measuring the frequency response. First, the magnet was clamped in contact with an extremely heavy inert slab to simulate the ideal of an immobile magnet. Secondly the drive unit was hung from a rigid frame on highly compliant rubber cords, to simulate as closely as possible the condition of totally free motion. The results of this experiment are shown in figure 1.
It can be seen that the cone acceleration is almost identical in the two cases. On an expanded scale there is indeed a difference in the order of 0.1dB to 0.2dB, though this is within experimental error for the repeatability of this experiment. The magnet acceleration is reduced in level by approximately 40dB, which is consistent with the known mass ratios for this driver. Clearly the motion of the magnet when rigidly clamped is close to zero and so is not visible within the scale shown.
Fig 1 Cone and magnet acceleration Black – cone motion with magnet clamped
Red - cone motion with magnet free
Blue - magnet motion, freely suspended
The shape of response of the magnet acceleration is also a very close match to the diaphragm acceleration up until approximately 300Hz, where the attachment of the accelerometer and the stiffness of the cone begin to affect the measurement accuracy. This is shown more clearly in fig 2
Fig 2 Ratio of magnet to diaphragm acceleration
Practical Considerations
For a real loudspeaker, the drive unit is neither rigidly held nor freely suspended. Conventionally the drive unit is attached to an enclosure in order to isolate the sound from the rear of the diaphragm and prevent it from combining destructively with the front, thus enhancing the low frequency response. The cabinet is typically constructed from wood composite panels. The cabinet is certainly not inert, and exhibits complex vibrational behaviour. The mechanical support for the magnet, attached to the enclosure via the chassis, should therefore also be expected to vibrate in a complex manner. To test this, the magnet acceleration can be measured whilst the drive unit is attached to the enclosure.
As a comparison, an alternative method of attachment has been studied. This consists of attaching the drive unit to a sub-baffle, which is in turn attached to the enclosure via rubberized isolating bushings similar in concept to those used to isolate engine vibration from the chassis of automobiles. This method of attachment is intended to mimic the behaviour of the freely suspended ideal over a broad range of frequencies.
Figure 3. shows the magnet acceleration for two conditions
1. Drive unit screwed to a typical cabinet
2. Drive unit mounted via isolated baffle
Fig 3 Magnet acceleration responses Black – cone motion
Red - magnet isolated from enclosure
Blue - magnet attached to enclosure
The magnet acceleration for the isolated baffle condition is much more uniform in its behaviour, and more closely approaches its theoretical ideal, than for the rigidly attached conventional approach. This is perhaps even more obvious when the time response of the magnet acceleration studied, as shown in figure 4.
Fig 4 Magnet acceleration impulse response
Red - magnet isolated from enclosure
Blue - magnet attached to enclosure
The time response of the rigidly attached system rings on for much longer and exhibits a much greater amplitude, due to the high Q nature of the mechanical resonant behaviour.
The fact that the magnet moves in a complex manner dictated by the properties of the enclosure, when rigidly attached to it, obviously imply that the enclosure panels are vibrating. They are therefore capable of radiating sound in much the same manner as the diaphragm. Because of the large radiating area they have the potential for contributing greatly to the overall sound output at frequencies where there is significant motion.
To determine their contribution, acceleration measurements were made in the center of the back and side panel, for both the isolated and non-isolated conditions.
The results in both frequency and time are shown in figures 5-8.
It is evident that the panel acceleration is significantly reduced in the case of the isolated mounting method, showing improvements greater than 20dB.
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Post by MartinT on Feb 8, 2022 15:10:45 GMT
One thing that's worth mulling over is this: I find the absolute best two isolation/damping products to be Townshend Podiums and Black Ravioli Pads/Big Pads.
What they have in common is a combination of isolation and damping. In this regard, they are more like a modern car's suspension on a different scale, rather than just cart springs or rubber blocks.
Of course, they are created with a different level of isolation and damping, suited to their purpose. The Podiums are designed to allow a speaker's weight to swing gently in the 1Hz region, well below the lowest expected replay frequency. Soft springing with some minimal damping. The Black Ravioli must have a higher resonant frequency (I don't know what) but appear to feature very high levels of damping, an inherent feature that becomes obvious the more you use them.
In both cases, the net effect is one of great clarity, tightness and focus to the sound while allowing the music to breath. Podiums allow large speakers to deliver deeper and tighter bass, which seems at first counter-intuitive. They are the opposite of spikes which I now abhor anywhere near my system - these are all about artificial edge enhancement to create a false sense of 'speed' and excitement. Black Ravioli appear to be just inert blocks very similar in appearance to sorbothane pucks, but with a different outcome. Quite why they are so effective is not at all obvious, but they do justify their elevated price.
I've never thought of these two products together before, but it occurred to me that their similarities are an explanation for why I've fallen on their use throughout my system.
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Post by MikeMusic on Feb 8, 2022 16:10:57 GMT
From memory Sorbothane was the least effective under kit, better than spikes or nothing
Latest Black Ravioli the best.
The Townshend stands I have still make me smile - bonkers and wonderful sound allowed because of them
I still have a test to do as I have my TAD E1s on Black Ravioli on Townshend stands.
Didn't test when I put the BRs under as I thought it was going to be tortuous at best but wasn't
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Post by karatestu on Feb 8, 2022 16:47:45 GMT
My latest brainwave is to mount the mid bass driver on an inner tube. As the driver doesn't weigh that much a heavy weight could be bonded to the back of the magnet and this would allow a bit higher pressure to be used in the tube to enable a very low Fs of the system.
Inner tubes don't come in the right size but my cycle coach friend tells me to just cut a bit out of the tube and re join it. It would be interesting to see if a driver with added mass would mould the tube to its shape under the weight. There are lots of things to consider here. The main thing here is my mid bass is up firing so this sort of meddling is quite easy. If there was enough mass then there is a good chance the tube would seal around the driver so no air leaks.
The racing tubes are very thin so they would not block the back wave from exiting the driver basket and their round shape would provide some chamfering. Externally I don't know how it would look and there is the valve to consider as well. If the baffle the tube sits on is made further down than the outside baffle then maybe all this can be hidden. This idea may fall flat on it's face but I think it is worthy of further thought.
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