Mass loading speakers

Discussion in 'Audio Hardware' started by Brian Gupton, Sep 3, 2016.

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  1. Brian Gupton

    Brian Gupton Forum Resident Thread Starter

    I've been chasing this same intermittent low end resonance / energy build-up issue for awhile, but this isn't really a post about that.

    Instead, it's a post about a pleasant discovery... mass loading my speakers made some dramatic improvements.

    I have always had my Shindo 604's sitting on plywood, which sat on my rug. This is how Shindo recommends they be used. After a recent speaker repositioning, I was noticing a lot more vibrations getting transferred to the floor that was causing a resonance (tho not necessarily THE resonance I was chasing).

    For the first time ever, I removed the plywood altogether and had the speakers sit directly on the rug. The vibrations lessened, but we're still there.

    I have a bunch of boxes of LP's sitting in an adjacent room, so I stacked 3 full boxes on the top of my speakers.

    Whoa! The improvement in sound was not subtle. Everything was more solid and focused.

    I did lose a lot of overall room energy when I removed the plywood (room doesn't feel as pressurized), but that could just mean that I need to reposition the speakers to better load the low end. Or maybe I will try putting the plywood back and then mass loading the speakers.

    Anyway, I know a lot of speakers aren't shaped in a way where mass loading like this will work, but thought I'd share as I've not seen this discussed much and it's free to try. Ugly, but free.

    Try it and report back. :)

  2. F1nut

    F1nut Forum Resident

    The Mars Hotel
    One word, spikes.
    chervokas likes this.
  3. Brian Gupton

    Brian Gupton Forum Resident Thread Starter

    I don't think that isolation/decoupling is the only thing going on here.

    The Shindo speakers for their size are quite light in weight. Seems like that combined with the materials used (plywood) in and of itself is going to create a cabinet prone to vibrations.

    Mass loading, in addition to coupling the speaker with the floor, seems to be helping create a more stable platform for the speakers to do their job.

    I know I'm not discovering something new here, but I was surprised at how much better this sounded.
  4. It looks like a tile & grout floor & my 1st thought was a parasitic transmission back into the cabinet, hence the recommendation for isolation first, then go for the tweaks. Best of luck with the fine tuning.
  5. Lester Best

    Lester Best Well-Known Member

    Bklyn NY
    You might try 2" closed cell foam cut to size. IMO, If you have sprung wooden floors, spikes are the wrong way to go.
  6. avanti1960

    avanti1960 Forum Resident

    Chicago metro, USA
    You may have stiffened the enclosure a little by adding the mass to the top surface but the biggest sonic effect you are hearing is because of the front surface area of the boxes acting as a much larger front baffle.
    The front surfaces of the boxes are reflecting the radiating frequencies of the drivers directly to your listening area. This will have a huge effect on the frequency response that reaches your ears. No wonder it sounds so different.
    The speaker's crossover was designed in part based on baffle size and surface area- baffle step compensation (BSC) to compensate for frequencies that reflect off of the baffle. The boxes have added a hefty increase to the baffle surface area and will increase the volume of the certain frequencies that are reflected- most likely it will affect frequencies above 500Hz or so that have a wavelength equal to or less than the width of the baffle.
    Frequencies below 500Hz will continue to radiate around the back of the enclosure because their wavelength is longer.

    BSC made simple (and why it may be important to you) – Audioblog »
    Kyhl, Brian Gupton and GuildX700 like this.
  7. F1nut

    F1nut Forum Resident

    The Mars Hotel
    He has carpet over tile (see photo above), so spikes are the right way to go and since the speakers are said to be a bit light the mass loading is a good idea as well.
  8. missan

    missan Forum Resident

    I agree with avanti1960, the most of the difference is most likely the different baffle response. A small part can be the more difficult acceleration of the larger mass. But You could like that more, of course. I would never use spikes, I have always seen spikes detrimental.
    Last edited: Sep 3, 2016
  9. blakep

    blakep Forum Resident

    Just my opinion, but using spikes or a solid cone type of footer for the speakers would depend (to me) on whether the tile floor is suspended or over a concrete slab.

    If the tile is on a concrete slab, I would consider spikes or a hard cone footer (some kind of harder rubber footer still might be best); if the tile is over a suspended floor I would definitely not spike.

    With a suspended floor I'd have (and have done exactly this) granite bases built and damp the underside (floor side) with some 3M automotive damping sheets or 1/8" neoprene sheet. Spikes or other footers (hard or soft) might not even be necessary once the speakers are situated on these bases but you could experiment with either.

    If you want to mass load the top of the speaker (which I've also done), I would do exactly the same thing and have some granite tops cut and damp the bottom with a lossy material like the automotive damping sheets or thin neoprene foam.

    If you have a concern about the damping material staining or discoloring the top of the speaker, simply cut an appropriate sized piece of wax paper and place that on top of the speaker before then placing the damped granite on top of the waxed paper.
    triple likes this.
  10. GuildX700

    GuildX700 Forum Resident

    One thing that has not been mentioned is the speaker's frequency response changes with that "wall" of additional height added to the top of the cabinets. With bass heavy source music playing move those boxes around on top of the cabs and you will find the bass response changes, sometimes very little, but then again sometimes quite dramatically.

    Oops, I just noticed post seven addresses this quite well. :righton:
  11. Gang-Twanger

    Gang-Twanger Forum Resident

    Interesting thread. I imagine a heavy driver like that in a fairly-light enclosure might cause some resonances, whether that's good or not (When I look at brands like Harbeth and their thin-walled enclosures, it kind of puts me back at square one in terms of that stuff). My main speakers don't seem to have that much in the way of resonances, as that was the company's #1 priority when it came to their designs. Resonances were their enemy. Each one of my W90's has a pair of 12" woofers, each one in it's own isolated, subdivided enclosure (In other words, the woofer section is subdivided into two sub-enclosures, one next to the other, not one on top of the other), and on the back of each woofer's sub-enclosure is a sand-filled rear panel, which eliminates backwaves and creates a stronger, less-resonant cabinet. And it really does work too. No backwave whatsoever. The mids and tweeters were free-air-mounted up top in their own isolated upper section of the cabinet in a horizontally-linear configuration, left to right, with the two 5" mids in the middle, which were flanked on either side by the two outside left and right tweeters. In other words, six drivers per cabinet in a dual 3-way design, kind of like somebody took a pair of 3-way, mirror-imaged speakers and glued them together. With that sort of design, I'm not sure that mass-loading each one on top of the cabinet will help, but they do have flat tops that can easily facilitate it, so I might just have to give it a try before I move at the end of the month. But like I said, that company took resonances and backwaves very, very-seriously, so it's hard to say what will happen.

    Wharfedale (who made my old W90's) had a model in the '50's and early '60's that had a sand-filled front baffle as well as two optional sand-filled rear panels. All that for a single 15" woofer. There was a mid and tweeter as well, but they were free-air-mounted in a separate, open-air unit that sat on top of the woofer enclosure. Perhaps the mid/tweeter box was the reason for so much isolation and resonance-control down below, or maybe they didn't have to worry about the tweeter and mid because they were free-air-mounted in a separate unit. Don't really know, but they sure cared an awful lot about eliminating vibrations/resonances.
  12. Bill Hart

    Bill Hart Forum Resident

    Gents (and ladies, if present): Isn't this speaker of Brian's intended to have a resonant cabinet? (I know that's contrary to modern speaker design practice, but that's my recollection without digging for information). If so, I think, Brian, you may be ready for a different speaker, rather than trying to defeat the original design objective. (I could be wrong about all of this, including that Brian is ready to move on). The 'baffle' comment by Avanti fascinated me- putting wings or extensions on speaker baffles was done in a various of ways, for a variety of reasons.
    Tullman likes this.
  13. Gang-Twanger

    Gang-Twanger Forum Resident

    That's what I was thinking, what with Harbeth and all those little BBC tupes. I don't understand the science of it, but people say it works (Isn't it some kind of thing where one vibration cancels out another somehow? I have no idea, honestly).

    But his drivers are an old Altec studio monitor kind of thing, rebuilt ones, I assume? Pretty-similar, I guess. Just 40 or 50 years ago, so I'm not sure if that's the philosophy behind those cabs. I'd love to know more about them though, and the drivers as well. I like the old 604-types.
    Last edited: Sep 4, 2016
  14. blakep

    blakep Forum Resident

    With tweaks I never get too hung up about them if they're reversible. While it's true that design philosophy obviously has a huge role in the sound from any component there are also so many other variables: listener's subjective preferences, room interactions, etc. that the original design philosophy may not have accounted for.

    Which may be one reason why audiophiles are on the endless merry-go-round with equipment. I figure if the tweak is reversible, go for it. It may bring you much more satisfaction than new speakers at the price of a couple of decent records. If not, you can always go back, and/or move on from there.

    In re-reading and looking at Brian's first post I see he lost the plywood before mass loading. I would definitely put the plywood back to check out the results from that. My speakers are very different from Brian's but I did experiment with baltic birch platforms beneath them at one point before using damped granite (cost me virtually nothing), which I much prefer. Not really a fan of spikes for speakers in any situation where there is a suspended floor-the interface between the actual speaker and the granite I'm using is a harder rubber footer-I found that to give the best overall sound quality based on my subjective preferences.
    Bill Hart likes this.
  15. Jtycho

    Jtycho Forum Resident

    I'm completely for anyone doing whatever they want to their system to get it to sound the way they want/hope it can sound. However I can't help but feel that at the price of these speakers, and your Garrard, you shouldn't have such problems. Mind you I'm not saying there's a flaw in any one component you have (expect the room, in which case almost all of our systems are flawed), but mass loading those Shindo's shouldn't be necessary. Have you had your room tested?
  16. hockman

    hockman Forum Resident

    I wouldn't put 3 heavy boxes of LPs on my expensive speakers. Madness of audiophilia!
    The Pinhead likes this.
  17. Manimal

    Manimal Forum Resident

    Southern US
    That's a cool wooden statue:)
  18. avanti1960

    avanti1960 Forum Resident

    Chicago metro, USA
    Very curious about how using spikes can hurt the sound? What would you recommend for dense carpet?
  19. mongo

    mongo Forum Resident

    This is why most speaker manufacturers haven't build cabinets like this for the last 50 years.
    Just sayin'
    TommyTunes likes this.
  20. missan

    missan Forum Resident

    The problem with spikes is that they can transfer feedback from floor vibrations. The best IMO is to use compliant feet with a very low resonance frequency, preferably lower then the lowest speaker res. Then vibrations are stopped from reaching the floor, and vice versa.
    blakep likes this.
  21. blakep

    blakep Forum Resident

    I agree, especially with any kind of suspended floor. If you can spike to a massive concrete slab that is potentially a different story.
  22. avanti1960

    avanti1960 Forum Resident

    Chicago metro, USA
    that's my setup. spikes through the dense carpet over basement concrete slab. i actually stand on the stand to push the spikes through the carpet and pad.
  23. missan

    missan Forum Resident

    Potentially yes, it will depend. Also concrete isn´t free from vibrations. All in all in most cases I see spikes as a detrimental design.
  24. TommyTunes

    TommyTunes Senior Member

    Given the number of issues you have had over the years, maybe its time to rethink the gear that you are using.
    Tullman likes this.
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