Speaker Stand modification. Which looks better?

Gardenstater

I Dynamat Xtremed the right speaker's black iron support stanchion, which was previously filled with lead shot/sand and didn't like the appearance of the Dynamat so as an experiment I covered the stanchion, including the flanges. It just looks so weird to me, maybe because I'm used to the way it looked so open underneath (ha ha I know. Get a life). Also, maybe it's my imagination but the sound seems a little less open from the right speaker now! It's a work in progress. Other contemplated changes are to do a faux marble finish on the blocks, similar to what people do with cast in place kitchen countertops. Not sure my artists skills are up to the task.

PS: I know the room is not an ideal listening room especially with all the clutter.

mhardy6647

It;s a good thing that you put two photos in -- I swear I thought you'd taken the novel, innovative step of integrating a file cabinet into your loudspeaker stands.



As far as stands... well...

earlypolkfamilyportrait by Mark Hardy, on Flickr

PS Clutter is a viable and valuable environmental treatment. Breaks up standing waves.

Gardenstater

verb

I vote for the larger diameter pipe. Aesthetically more balanced, and you can mass load em with more fill.

msg

Yeah, I like it better, too.
What is that sleeve, anyway? PVC?

Are those concrete pavers? How did you build that samwich? And I presume there are fasteners going through them? How'd you do that? Masonry bit? Is there some kind of flange the fasteners attach to?

Like to hear more about this design.

What's your top plate? Might take a closer look at what the goal is as far as isolation or coupling goes. Mass is only part of the equation.

I think with bookshelf speakers, decoupled from the stand and stand coupled to the floor is a common plan.

(edited for mobile device keyboard fubarisms)

audioluvr

Looking good. I vote for the one on the right too. Looks cleaner. Need to paint the bottoms black though. Maybe with automotive bedliner?

Gardenstater

@audioluvr thanks for the input. I'm still getting used to the new look being so *chunky*. A friend suggested something similar but Flex Seal. Either way may even give them some more dampening. Not sure what the resonant frequency of my concrete blocks are. I know the higher the mass density the lower the resonant frequency and the more stiff, which factors in shape and size and material properties, the higher the frequency, or at least that's my current understanding.

Gardenstater

msg wrote: »

Yeah, I like it better, too.
What is that sleeve, anyway? PVC?

Are those concrete pavers? How did you build that samwich? And I presume there are fasteners going through them? How'd you do that? Masonry bit? Is there some kind of flange the fasteners attach to?

Like to hear more about this design.

What's your top plate? Might take a closer look at what the goal is as far as isolation or coupling goes. Mass is only part of the equation.

I think with bookshelf speakers, decoupled from the stand and stand coupled to the floor is a common plan.

(edited for mobile device keyboard fubarisms)

For now, the sleeve is a piece of dollar store posterboard secured to the pipe flanges and to itself with a seam in the rear using double sided .003" thick, urethane adhesive, polyester tape. The idea is just to hide the ugly Dynamat Xtreme I just applied to the outside of the pipe and I wanted to see if it would look cleaner and less industrial to hide the pipe and flanges.

My design goals were vibration isolation from the floor, but coupling, as minimally as possible, to the top concrete block which affords stability and mass. Pipe is hollow and filled with sand and lead shot, as small dia. as possible structurally, and secured to concrete block with flat head tapcon screws and epoxy bedding also. Between the two concrete blocks is a 16" Schrader Valve Bicycle Tube, very minimally inflated to have as low of a resonant frequency as possible to prevent vibration transmission as much as possible to and from the floor. Key feature is to drill a 3/16" hole in the center of the bottom block so as to not create another air chamber within the tube. When I did that it was one of those jaw dropping moments that you live for in audio, where the sound of my system COMPLETELY changed from drilling one little bitty hole (for the better). Bass became more tight and highs clearer even. Underneath the bottom concrete block there are hardened stainless steel thin plates epoxied to the bottom of the block, with roller ball assemblies under that and under the roller balls are DIY Viscoelstomeric Vibration Isolators created from Quad Max Caulk, chosen for it's softness. That's still under R&D because it turns out that with a material that soft, creep becomes an issue over time and I'm still figuring out what the proper load per sq in. should be.

I used to have my own DIY version of the shorty tilted Polk stands, filled with sand, but I wanted to get the tweeter/midrange up near ear height for a more realistic soundstage and this definitely made a vast improvement in listening enjoyment. I need to get the resonant frequency a little bit lower but there is very little vibration detectable even with your fingers touching the wooden floor which is over the basement ceiling joists so it ain't too far off from optimized and I have verified that with a vibration detecting app on my Android phone.

msg

So, coupling the speaker to the stand, and the stand decoupled from the floor?

Your results are intriguing, specifically after the addition of the inner tube. I would think that would be allowing for movement in the upper half of the stand, which would, in theory make for a measure of the opposite of the tightening effect you've described. I don't doubt you're hearing what you are, though.

I don't quite understand how you can inflate the tube, however minimally, and not create an air chamber. if the air in the tube "escapes" to a "tube protrusion hole" into the lower block, it seems like it would just be the same as tube-on-tube without any air in it at all - a rubber buffer between the blocks?

This tightening effect you've described - what are you comparing against? The setup with the tube placement previously, but without the 3/16 hole, or in comparison to prior to adding the tube altogether?

At any rate, interesting, and I applaud your experimentation and sharing you experience and observations.

Gardenstater

msg wrote: »

So, coupling the speaker to the stand, and the stand decoupled from the floor?

Your results are intriguing, specifically after the addition of the inner tube. I would think that would be allowing for movement in the upper half of the stand, which would, in theory make for a measure of the opposite of the tightening effect you've described. I don't doubt you're hearing what you are, though.

I don't quite understand how you can inflate the tube, however minimally, and not create an air chamber. if the air in the tube "escapes" to a "tube protrusion hole" into the lower block, it seems like it would just be the same as tube-on-tube without any air in it at all - a rubber buffer between the blocks?

This tightening effect you've described - what are you comparing against? The setup with the tube placement previously, but without the 3/16 hole, or in comparison to prior to adding the tube altogether?

At any rate, interesting, and I applaud your experimentation and sharing you experience and observations.

I put a dial indicator on the top of the speaker cabinet with a video camera on it and even blasting DSOTM there is no measureable movement. F=mA and the mass of the cones and voice coil/spiders is very small vs the mass of the speaker cabinet/baskets/magnets/stand/top concrete block, so the inertia in this situation is sufficient to prevent movement in my situation. Now with some powerful subwoofers the situation could change but that's something that has to be worked with and they are much lower to the blocks which helps.

Yes it is essentially a pneumatic spring between the blocks with the spring constant being lowered the less air that is in the tube. Eliminating the air trapped within the tube by putting a vent hole lowers the effective spring constant further because that would be just another pneumatic spring that you don't want, in parallel with and additive to the tube spring. The lower the spring constant the lower the resonant frequency, which is what you want to achieve.

The jaw dropping moment where the sound quality improved drastically.....tighter cleaner bass, more transparent clearer highs etc.. occurred simply by drilling a tiny hole in the bottom block to allow air to vent from within the tube, so tube was there before and after.

msg

Cool! You're really testing this stuff!

Did the tube have air in it before? Was there movement?

What I'm wondering is whether you'd have the same profound effect in just placing the innertube between without any air in it.

Sorry if I've missed this part, but did you ever run this setup block to blow without the innertube? Relying just on your roller ball assemblies and the DIY Vibration Isolators created from Quad Max Caulk?

Kex

Oddly, perhaps, I like the left version better, because for me, it puts the speaker more to the forefront visually. It’s not competing for attention. With the thicker tube, it makes the speaker share the podium, as it were.

Actually reminds me of my first speakers (big Cabasse bookshelf), which were on Spectral stands from Germany, with a steel tube and an all glass base. I’d include a link, but can’t find one handy right now.

JayCee

@Gardenstater, my .02 on the pipe...a diamater between the two. Not too big, not too small, but just right (LOL). Also think, regardless of method, making the cement black would look nice.

I've done a few things that go against the norm (experimented) and found while the accepted norms work in most situations, there are exceptions that work for my particular circumstances. I appreciate your willingness to question, try different things and report your findings. Lots of good advice on this forum but respectful dialog, firsthand experience and a willingness to think outside the box is fun. Nothing ventured, nothing gained.

Gardenstater

msg wrote: »

Cool! You're really testing this stuff!

Did the tube have air in it before? Was there movement?

What I'm wondering is whether you'd have the same profound effect in just placing the innertube between without any air in it.

Sorry if I've missed this part, but did you ever run this setup block to blow without the innertube? Relying just on your roller ball assemblies and the DIY Vibration Isolators created from Quad Max Caulk?

Yep the tube had the same amount of air before and after the hole was drilled through the bottom paver block. Well no *measurable or detectable* movement but I'm sure that there is movement on a micron scale, in order to absorb or prevent the transmission of vibration. After the hole was drilled you could more easily rock the whole speaker/stand assy by pushing on the top of the speaker, which is a lot of force relatively speaking, due to the lowered spring constant.

I think you would have some effect if you just put a tubular piece of neoprene rubber, which would just be a super thin viscoelastomeric isolator instead of an inner tube (pneumatic spring) but nowhere near the vibration transmission prevention and it would even have a resonant frequency which would cause a coloration or peak at that frequency, which is definitely not what I want. If you get the resonant frequency down in the single digit Hz area, that will very effectively prevent transmission of all audio frequencies to the floor, walls, other speaker, and audio equipment. The whole notion of low Hz outside vibrations getting into our systems from trains, cars, etc.. is a whole 'nother area which is a little more, shall we say debatable, but I think it's a real concern for some people in some locations, but is a lesser concern I think.

I initially started with no innertube sandwiched between the two patio blocks, just two 36 lb blocks, one on top of the other, with the polished hardened stainless steel plates and roller bearings and then the typical rubber/cork/rubber sandwich isolators. Then I went to the Quad Max isolators which was an incremental improvement but adding the inner tubes between the blocks and drilling the hole was the huge game changer.

I'm not advocating anyone else experiment with the Quad Max Caulk isolators because the jury is still out on whether or not it will ever be possible to eliminate the creep effect over time. I think that there is a maximum load that can be applied which will, but I am not sure yet and I don't want to encourage anyone to go into it without being aware of that.

Gardenstater

@JayCee I think so too lol, we'll see how it sits with me over the next week. $1 sheets of posterboard from the dollar store won't break the bank I wanted to try to entirely hide the pipe flange along with hideous Dynamat but.......maybe I'll make a collar that goes around the pipe top and bottom that is an intermediary dia. to secure the next $1 piece of posterboard in the next attempt.

msg

Gardenstater wrote: »

Yep the tube had the same amount of air before and after the hole was drilled through the bottom paver block. Well no *measurable or detectable* movement but I'm sure that there is movement on a micron scale, in order to absorb or prevent the transmission of vibration. After the hole was drilled you could more easily rock the whole speaker/stand assy by pushing on the top of the speaker, which is a lot of force relatively speaking, due to the lowered spring constant.

Wow, I'm really surprised you didn't notice the opposite here. I would have thought it would have been stiffer after drilling the hole for the tube escape - more like going from a squishy partially filled innertube, to rubber on rubber. Perhaps I'm thinking in exaggerated extremes.

Gardenstater wrote: »

I initially started with no innertube sandwiched between the two patio blocks, just two 36 lb blocks, one on top of the other, with the polished hardened stainless steel plates and roller bearings and then the typical rubber/cork/rubber sandwich isolators. Then I went to the Quad Max isolators which was an incremental improvement but adding the inner tubes between the blocks and drilling the hole was the huge game changer.

Good stuff.

Gardenstater

@msg the hole is in the center of the block and only allows air to not be trapped within the *inner dia* of the inner tube, ie. between the two blocks and the inner space where the air could be trapped, not the air that is inside the tube as in what you put in and take out through the schrader valve.

Faustin

Curious, are the stands/speakers tilted back a bit?

Gardenstater

Faustin wrote: »

Curious, are the stands/speakers tilted back a bit?

No I didn't make any attempt to time align the tweeter dome and the midrange cone. It would be very easy to tip it back though by placing shims under the front roller bearing or isolator. I have the height so that the midpoint between the center of the tweeter and midrange is right about at seated ear height.

On second though it would probably be better for stability to keep the plane of the innertube level and place a tapered shim between the top pipe stanchion flange and the speaker shelf. I'd first want to see if I can hear any difference by placing shims between the speaker and the front of the shelf first before going to all that trouble of making tapered pipe flange shims.

Gardenstater

Actually my ears height when seated is a few inches below the center of the tweeter and midrange so that helps a bit with the time alignment, since the tweeter is positive relative to the baffle and the midrange is sub baffle level

Gardenstater

Have them tipped back 3deg now, with the center of the midbass/tweeter at 42" from the floor. Like it better. Looks like I need to make some tapered shims now.

msg

Gardenstater wrote: »

@msg the hole is in the center of the block and only allows air to not be trapped within the *inner dia* of the inner tube, ie. between the two blocks and the inner space where the air could be trapped, not the air that is inside the tube as in what you put in and take out through the schrader valve.

OHHHH! I thought it was in a place the tube crossed over.
Dehr, the 3/16" spec didn't quite sink in. I see now.

Gardenstater

@msg sorry for confusion. I re-read what I wrote and it wasn't totally clear

Gardenstater

I actually calculate that, to time align the tweeter and midbass I should need 6.7 deg of tilt back, which is pretty extreme. That's for the listeners ear height at the same height as the avg height of the tweeter and midbass drivers, which is what mine is pretty much at. If you have a different relative listening height you have to take into account both that and the distance to the speakers, which gets more complicated. Haven't factored in the passive yet.

Gardenstater

Wow Polk really figured this stuff out. To time align the midbass to the Passive, at an equilateral sweet spot distance of 4ft (my speakers are close together unfortunately) and an ear height of 42in., which is about 7in. above the pair's center, you need................6.7deg of tilt back...Wow.

mhardy6647

Gardenstater wrote: »

Wow Polk really figured this stuff out... Wow.

That's what happens when one's diploma sez The Johns Hopkins University on it.

Gardenstater

After doing a little more re-calculation and analyzing the geometry of the drivers (truncated cones and spherical caps), I came up with a figure of 6deg (OK 6.04 lol), in order to time align the tweeter and midbass for a listening ear height that is midway between the tweeter and midbass, which in the case of my stands is 41-1/2" from the floor. Unfortunately, in a design like the 7Bs, it will always be a compromise between time alignment and on-axis listening. It is in some ways nicer to listen more on axis to the tweeter, and to a lesser extent the midbass.

I think an interesting experiment would be to space the midbass out from the speaker baffle by 0.54" to accomplish the time alignment w/o compromising on axis listening so much. An unintended consequence to that would be that the speaker baffle would block even more of the windows in the basket of the midbass driver, unless the baffle was given additional clearance at the windows by chamfering away some of the material. I may try this. A similar thing could be done for the Passive Radiator.

Gardenstater

Actually I should add that the dome tweeter (dia. 1.43in.) is the only driver that even comes close to being approximateable by a point source, but that's the assumption you have to make to *time align* the drivers by mere angle. It's actually better to model the drivers as a plane source but then you'd want to space the drivers properly relative to the baffle rather than tip them. When you tip the 7Bs (or just change your ear height/distance) to try to get a better time alignment on average, you will be listening to the midbass off axis, which invariably means, due to it's size, that you're gonna be getting time misalignment within that driver or across that driver if you will. It's a very noticeable effect so I think a compromise is in order.

Gardenstater

Trying an intermediate diameter on the left speaker stand, that still allows access to remove the flange screws so that I could experiment with different tapered shims for time alignment of drivers.

msg

Dude, you are a maniac!

Gardenstater

Ha! I have no comeback.