Testing stage filler - Sand, Fiberglass, or Nothing - Page 2 - AVS Forum | Home Theater Discussions And Reviews
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post #31 of 343 Old 10-26-2014, 01:22 PM
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I'm very interested in this topic because I don't fully see how it works with the modern multi-sub approaches. Once you have subs off the stage in columns or walls then haven't you lost most of the benefit?

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post #32 of 343 Old 10-26-2014, 01:29 PM
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Nope. All depends HOW you implement those column and wall subs.

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post #33 of 343 Old 10-27-2014, 07:11 AM
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I think the topic is interesting and I appreciate the effort being put into this.

One thing I might suggest would be to add an intermediate step between fiberglass and total sand fill to test an area of sand fill just under the sub(s) positions. Say a 2'x2' or 3'x3' area packed with sand just to isolate the subs, then leave the rest of the stage fiberglass. This might be effective in testing a "good enough" scenario for those of us that do not want to or do not have the ability to haul in two tons of sand.

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post #34 of 343 Old 10-27-2014, 08:08 AM
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Originally Posted by BllDo View Post
I think the topic is interesting and I appreciate the effort being put into this.

One thing I might suggest would be to add an intermediate step between fiberglass and total sand fill to test an area of sand fill just under the sub(s) positions. Say a 2'x2' or 3'x3' area packed with sand just to isolate the subs, then leave the rest of the stage fiberglass. This might be effective in testing a "good enough" scenario for those of us that do not want to or do not have the ability to haul in two tons of sand.
I was perusing the forum a few minutes ago and spotted this thread. It piqued my interest because I plan to add a few things to my HT space upstairs to make it more like.. well... an HT, instead of a big room with speakers and a screen as it currently feels.

I've been considering building a stage to add that missing something and my experience with car audio and tactile energy transfer was leading me toward doing pretty much what you've said. I don't want an open space to become a resonant chamber so filling it with something seems natural. Sand or even kitty litter... something with high density would go a long way toward stifling resonances. BUT, being on a second floor, I can't really add thousands of pounds of sand. Just doesn't seem like a good idea. So, I was thinking of adding sand directly under the subs and then filling the rest of the stage voids with fiberglass.

Definitely curious what some of the guys in this thread think about what you've said, and what I was considering. In my case, and I'm sure others' as well, having the room on a second floor really raises the concern of adding considerable mass to the room's riser/platforms.
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post #35 of 343 Old 10-27-2014, 02:28 PM
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Originally Posted by SierraMikeBravo View Post
Nope. All depends HOW you implement those column and wall subs.

How do you implement them to preserve the supposed benefit of the sand filled stage? Decoupling clips?

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post #36 of 343 Old 10-27-2014, 03:58 PM
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This thread is another case of "I'm taking my ball and going home" because someone is asking questions. That's the biggest downfall to new people reading this site. This could have been a very good and informative thread. Sad really.
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The TRUTH in your theater is determined by your EYES and EARS. Not how many specifications you can rattle off. Not in how much money your last piece of equipment cost. Not in your post count. The longer I'm here the better I understand why you all have to ask your wife for permission on what you're allowed to place in YOUR house.
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post #37 of 343 Old 10-27-2014, 04:31 PM
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Originally Posted by JeffHurt View Post
This thread is another case of "I'm taking my ball and going home" because someone is asking questions. That's the biggest downfall to new people reading this site. This could have been a very good and informative thread. Sad really.

"The TRUTH in your theater is determined by your EYES and EARS. Not how many specifications you can rattle off."
You have made 50 posts in 10 years, and I'm afraid I don't understand this last one. Unless I missed something I think granroth is going to forge on with his experiment.
Stick around a little while longer, though given your signature I'm not so sure you are looking for empirical data anyway.
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post #38 of 343 Old 10-27-2014, 05:05 PM
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No - his point is that the guys who make a living doing this, and have figured out "what matters" and "why" are a little bit, "you're going to have to take our word or it" about the whole thing. He's not wrong, but it's not that simple. If budget and space and modeling are all available, then sure, you do it the way that the pros do it, but for the DIYer, there are often compromises. Granroth is trying to figure out the value-added portion of the thing so that folks up can make informed decisions about the trade-offs.
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post #39 of 343 Old 10-27-2014, 05:09 PM
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Yes it would be useful to see some actual test information on the benefits of sand filled stages, especially given the financial and logistical challenges of the construction approach.
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post #40 of 343 Old 10-27-2014, 06:03 PM
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"S" fo science

Kudos to granroth, he's about the scientific method, bringing back the "S" to AVS!
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post #41 of 343 Old 10-28-2014, 06:14 PM
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Originally Posted by SierraMikeBravo View Post
Nope. All depends HOW you implement those column and wall subs.
So it's implementation detail - not a design detail. That would explain why my $6500 EG Signature Plans don't have any special mounting requirements for the other subs around the room.

The stage is part of the design. The shape, dimensions, framing, material layers, and the "empirically derived" quantity of sand required to get results are all there. But the other subs in the room look like they attach to the wall, nothing special.

Since this is just an implementation detail, can you share how it's done both for my benefit as a paying customer and for the greater AVS DIY community?

 

 

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post #42 of 343 Old 10-28-2014, 06:29 PM
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It would be difficult for me to comment on design plans that I have never reviewed or seen. I suggest you take that up with Dennis who is 'your room' designer. Every room is different.

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post #43 of 343 Old 10-28-2014, 10:34 PM - Thread Starter
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Kudos to granroth, he's about the scientific method, bringing back the "S" to AVS!
Woooaaahhh!! Let's slow down a bit there and not oversell this

I am absolutely going to provide some empirical tests with as rigid testing constraints and accuracy as I can muster. This will just be a data point, though. A true scientific test would have to involve more than one subwoofer; more than one stage design; and more than one room type. What if my results are only what they are because of the specific ratio of my specific subwoofer to the specific size and weight of my stage compared to the thickness and breadth of my concrete slab? We can't know until there is more testing done.

I would really love to see a series of tests like this done, by people with a variety of variables. What variables really matter? We'd need a bunch of data points to start seeing where the patterns are.

Really, though, I think HopefulFred absolutely nailed my motivation for this:

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No - his point is that the guys who make a living doing this, and have figured out "what matters" and "why" are a little bit, "you're going to have to take our word or it" about the whole thing. He's not wrong, but it's not that simple. If budget and space and modeling are all available, then sure, you do it the way that the pros do it, but for the DIYer, there are often compromises. Granroth is trying to figure out the value-added portion of the thing so that folks up can make informed decisions about the trade-offs.
Really, I can't say it better that that!

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It would be difficult for me to comment on design plans that I have never reviewed or seen. I suggest you take that up with Dennis who is 'your room' designer. Every room is different.
But more seriously, I'm not very convinced of this. I realize that I'm now standing here without a shred of real evidence disagreeing with a guy with years of experience on scores of theaters! Yeah... not very firm footing on my part.

Still, I've read through so so many build threads, including quite a few created using Erskine plans. What's notable to me is not how drastically different they are, but rather how remarkably similar they are.

I'll concede that there probably are subtle differences between the builds that I don't notice that really do make a difference in specific rooms with specific equipment (choices which also tend to be more similar than dissimilar, it seems). How noticeable are those differences, though? Do you need sensitive instruments to measure them? Maybe special auditory and visual training to see and hear them?
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post #44 of 343 Old 10-28-2014, 10:38 PM
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Originally Posted by granroth View Post
Woooaaahhh!! Let's slow down a bit there and not oversell this

I am absolutely going to provide some empirical tests with as rigid testing constraints and accuracy as I can muster. This will just be a data point, though. A true scientific test would have to involve more than one subwoofer; more than one stage design; and more than one room type. What if my results are only what they are because of the specific ratio of my specific subwoofer to the specific size and weight of my stage compared to the thickness and breadth of my concrete slab? We can't know until there is more testing done.

I would really love to see a series of tests like this done, by people with a variety of variables. What variables really matter? We'd need a bunch of data points to start seeing where the patterns are.

Really, though, I think HopefulFred absolutely nailed my motivation for this:



Really, I can't say it better that that!



But more seriously, I'm not very convinced of this. I realize that I'm now standing here without a shred of real evidence disagreeing with a guy with years of experience on scores of theaters! Yeah... not very firm footing on my part.

Still, I've read through so so many build threads, including quite a few created using Erskine plans. What's notable to me is not how drastically different they are, but rather how remarkably similar they are.

I'll concede that there probably are subtle differences between the builds that I don't notice that really do make a difference in specific rooms with specific equipment (choices which also tend to be more similar than dissimilar, it seems). How noticeable are those differences, though? Do you need sensitive instruments to measure them? Maybe special auditory and visual training to see and hear them?
You're free to disagree all you want. . Yes, of course there are similar approaches. Laws of physics don't change from one room to the next. If a solution is found that works, why would it be approached differently? Only one reason and that is because of the physical limitations of a room. Every designer is biased toward their OWN solutions to a problem. They often develop several solutions to deal with the physical limitation variables.

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post #45 of 343 Old 10-28-2014, 10:49 PM
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Every room is different.
So for the stage, you just over engineer it rather than taking the time to deal with all variables. But for every other wall in the HT, you develop a custom solution for those subs unique to each room?

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It would be difficult for me to comment on design plans that I have never reviewed or seen. I suggest you take that up with Dennis who is 'your room' designer.
We don't need to talk about my room. How about an example of a typical AVS room? Something you've designed in the past where plans showed Procella subs mounted on the wall. How were those subs mounted so as not to compromise the "greatly reduced or eliminated vibration transference" provided by the stage?

 

 

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post #46 of 343 Old 10-28-2014, 11:01 PM
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So for the stage, you just over engineer it rather than taking the time to deal with all variables. But for every other wall in the HT, you develop a custom solution for those subs unique to each room?



We don't need to talk about my room. How about an example of a typical AVS room? Something you've designed in the past where plans showed Procella subs mounted on the wall. How were those subs mounted so as not to compromise the "greatly reduced or eliminated vibration transference" provided by the stage?
How about using isolation clips to mount the sub? How about creating an isolation pad? Or, how about engineering it in such a way that the supporting sub is not even touching the floor or has minimal contact? Consider the fact that the supporting sub isn't as powerful in the low end as the main sub? Or another possibility is the fact you can adjust the volume of the supporting sub? Take your pick.

http://www.triadspeakers.com/cinemaplus.html

One possible solution, however not applicable in all rooms...or actually only two that I can think of, so I exceeded your asking requirement of one. The rest is up to the community to figure out. . Oh, and not necessarily unique to each room, but certainly not repeated in every room. I have implemented one, or many of the above mentioned methods in rooms plus one or two other methods that will remain my own, but I think I've given you a head start. I look forward to seeing what granroth comes up with.

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post #47 of 343 Old 10-29-2014, 07:01 PM
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Off topic and I just lost my whole carefully written post but the whole concept of using multiple different subs around the room ("balancing subs") is an interesting one to explore...maybe someone wants to start a new thread on it? I think the concept is flawed for many reasons.

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post #48 of 343 Old 10-29-2014, 07:39 PM
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You should start it. Im not too interested in participating, but I'd be interested in what you feel is flawed about it? I have calibrated dozens of rooms and all are very flat using this method. I'll inform Jim Harber and Adam Pelz of the thread when you start it ,and let them chime in with their two cents. It would be interesting.

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post #49 of 343 Old 10-29-2014, 08:05 PM - Thread Starter
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Off topic and I just lost my whole carefully written post but the whole concept of using multiple different subs around the room ("balancing subs") is an interesting one to explore...maybe someone wants to start a new thread on it? I think the concept is flawed for many reasons.
Start a thread and post your thoughts! I'll subscribe in an instant, because I'm now veeeery curious what your take on the subject is. Since the Harmon whitepaper, multiple subs has been a de facto standard. I'd love to hear arguments against it.
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post #50 of 343 Old 10-30-2014, 12:28 PM
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Start a thread and post your thoughts! I'll subscribe in an instant, because I'm now veeeery curious what your take on the subject is. Since the Harmon whitepaper, multiple subs has been a de facto standard. I'd love to hear arguments against it.
Tis not an argument against multi-subs, it is against multi-different subs, especially the balancing sub concept which seems to match very powerful stage located subs with very un-powerful side wall / back wall subs.

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post #51 of 343 Old 10-30-2014, 02:10 PM
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Post your argument.
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post #52 of 343 Old 11-01-2014, 11:54 AM - Thread Starter
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Hmm... so my thinking was that I would run a REW measurement sweep in various parts of the house. REW really wants to both generate and record the sweep during a measurement, though, which would be impossible when I'm outside of the room. That is, it can certainly record the sweep, but since I'm not going to have a cable going into the room, it can't generate the sound in the first place.

In my initial searches, I'm not finding a way to tell REW that I will generate the sound externally (maybe with AudioTools or another laptop running REW) and to only record the sweep. Is that possible?

I did try setting the output in REW to an AirPlay "speaker" and then hooking up an AirPlay compatible device to the receiver. That didn't work at all. Maybe AirPlay detects the difference between "noise" and "music"? Or maybe AirPlay just doesn't play low frequencies at all. Either way, it didn't work so that's not an option.

If REW can't be split, then my outside-room tests might have to be plain SPL tests.
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post #53 of 343 Old 11-01-2014, 12:46 PM
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What did you hope to learn from a sweep that you can't get from pink noise?

I think the answer there is nothing. The sweep allows the FFT to separate the time domain out, but temporal issues shouldn't be relavant here. We want the frequency response of the subs (anechoic) and we want the shape of the noise floor in adjacent areas - those two bits should get us transmission. For audible artifacts in the theater, we'll just need a series of carefully replicated sweeps.

What else?
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post #54 of 343 Old 11-01-2014, 02:03 PM
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The main test I would be concerned with would be tonal. If you can generate single frequency tones, you can walk around the house to see if specific elements are rattling or vibrating. That to me would mean more than any other measurement. Dennis eluded to that in his posts.

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post #55 of 343 Old 11-01-2014, 02:07 PM
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Shawn is probably right. That test is repeatable and does not depend on sensitive measurement equipment. The two tests I suggested are both problematic from that perspective.
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post #56 of 343 Old 11-01-2014, 05:46 PM - Thread Starter
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Okay, so I'm hoping to have repeatable tests that will capture the two prominent stated benefits of putting sand in a stage, relative to nothing or insulation. The first is to reduce the amount of vibrations to the rest of the house via the slab and the second is to increase the SPL for the sub itself (given identical levels for input).

The SPL increase should be straightforward to test by playing pink noise and run an RTA test in a bunch of locations. I'm expecting to set a benchmark with the sub on the floor and then see it decrease notably with an empty stage; maybe stay the same with insulation; and then go back to the same level as nothing when the stage is filled with sand. That is, I'd expect the on-floor and on-stage-with-sand numbers to be identical.

A typical REW measurement sweep would be interesting even in this aspect to see the differences in how the room reacts with the different fillers. I'd expect some resonant frequencies with nothing and to have them damped with insulation, for instance.

Testing the vibrational energy outside of the room is notably trickier. I did get a contact microphone but some tests done today showed that that's not going to give anything resembling workable results. Not a big surprise. Maybe hooking up an amp would help or maybe not. I don't have an amp, so that's not an option regardless.

Shawn's suggestion to run single frequencies is kind of why I was wanting to run a sweep. The key problem with single frequencies to figuring out which ones will make an impact. I did some exploratory testing today and discovered that it took very specific frequencies to trigger some kind of rattling. For instance, 54Hz (but not 53Hz or 55Hz) caused quite a few things I have hanging out in the theater (shop vac, tool chest, etc) to rattle, but did very little to the rest of the house. 35Hz caused some pictures on the wall in the hall to rattle, but not a lot in the theater. My thinking with doing a linear sweep is that it would hit all of the frequencies as it went. But maybe no?

Oh, some random news: I received word that my calibrated mic is shipping now and so I should get it sometime mid-next week. I'm going to take the entire week after that (Nov 10 - 14) off to build my stage, so that's when all the tests will be run.
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post #57 of 343 Old 11-01-2014, 05:53 PM
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Post your argument.

Definition of balancing subs: a strategy where small passive or limited output subs are placed in side walls, back wall or ceiling and used in conjunction with larger subs placed on the front wall or stage.


Balacing subs is not use of multiple matched subs. The extensive research conducted into the beneficial effects of multiple subs was based on the assumption of equal output.

My argument is this: The lower output balancing subs go into limiting (or severe distortion / overload if no limiters have been set up and you are using passive balancing subs with an amplifier) much earlier than the main subs. When the balancing subs go into limiting the room mode cancellation effects of having subs in different locations start to disappear.


I have nothing against the concept of band limiting balancing subs so they are only operating at frequencies where they can keep up with the output of the main subs. However the point at which balancing subs go into limiting is difficult to predict due to many factors - the SPL output of the sub being not just a simple result of ground plane output but also placement relative to room modes and relative to boundaries.


I am pretty sure that balancing subs are being used without attention to these matters as I have never seen it mentioned as something that must be carefully considered. I have not seen balancing subs being used with band limiting. I have also not seen any discussion of how limiting is setup during calibration by people who are using passive subs with amps. This also applies to DIY sub build efforts by the way.

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Last edited by Nyal Mellor; 11-01-2014 at 05:57 PM.
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post #58 of 343 Old 11-01-2014, 06:15 PM
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Originally Posted by Nyal Mellor View Post
Definition of balancing subs: a strategy where small passive or limited output subs are placed in side walls, back wall or ceiling and used in conjunction with larger subs placed on the front wall or stage.


Balacing subs is not use of multiple matched subs. The extensive research conducted into the beneficial effects of multiple subs was based on the assumption of equal output.

My argument is this: The lower output balancing subs go into limiting (or severe distortion / overload if no limiters have been set up and you are using passive balancing subs with an amplifier) much earlier than the main subs. When the balancing subs go into limiting the room mode cancellation effects of having subs in different locations start to disappear.


I have nothing against the concept of band limiting balancing subs so they are only operating at frequencies where they can keep up with the output of the main subs. However the point at which balancing subs go into limiting is difficult to predict due to many factors - the SPL output of the sub being not just a simple result of ground plane output but also placement relative to room modes and relative to boundaries.


I am pretty sure that balancing subs are being used without attention to these matters as I have never seen it mentioned as something that must be carefully considered. I have not seen balancing subs being used with band limiting. I have also not seen any discussion of how limiting is setup during calibration by people who are using passive subs with amps. This also applies to DIY sub build efforts by the way.
Good point Nyal! I agree!! But, thats what calibration is all about. And as far as other companies, well there wouldn't be much difference between us and them if we did everything the same. Each company has their own distict uniqueness. I can tell when I'm in an Erskine room or others and who designed it. We are all biased toward what we found which actually works, which includes equipment and placement. Why would you ever change a flavor or formula that works and works well? As far as calibration, that gets into a whole 'nother realm, one of which I haven't been too anxious to tackle in this forum due to its complex nature of every room is different.

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post #59 of 343 Old 11-01-2014, 06:22 PM
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Originally Posted by granroth View Post
Okay, so I'm hoping to have repeatable tests that will capture the two prominent stated benefits of putting sand in a stage, relative to nothing or insulation. The first is to reduce the amount of vibrations to the rest of the house via the slab and the second is to increase the SPL for the sub itself (given identical levels for input).

The SPL increase should be straightforward to test by playing pink noise and run an RTA test in a bunch of locations. I'm expecting to set a benchmark with the sub on the floor and then see it decrease notably with an empty stage; maybe stay the same with insulation; and then go back to the same level as nothing when the stage is filled with sand. That is, I'd expect the on-floor and on-stage-with-sand numbers to be identical.

A typical REW measurement sweep would be interesting even in this aspect to see the differences in how the room reacts with the different fillers. I'd expect some resonant frequencies with nothing and to have them damped with insulation, for instance.

Testing the vibrational energy outside of the room is notably trickier. I did get a contact microphone but some tests done today showed that that's not going to give anything resembling workable results. Not a big surprise. Maybe hooking up an amp would help or maybe not. I don't have an amp, so that's not an option regardless.

Shawn's suggestion to run single frequencies is kind of why I was wanting to run a sweep. The key problem with single frequencies to figuring out which ones will make an impact. I did some exploratory testing today and discovered that it took very specific frequencies to trigger some kind of rattling. For instance, 54Hz (but not 53Hz or 55Hz) caused quite a few things I have hanging out in the theater (shop vac, tool chest, etc) to rattle, but did very little to the rest of the house. 35Hz caused some pictures on the wall in the hall to rattle, but not a lot in the theater. My thinking with doing a linear sweep is that it would hit all of the frequencies as it went. But maybe no?

Oh, some random news: I received word that my calibrated mic is shipping now and so I should get it sometime mid-next week. I'm going to take the entire week after that (Nov 10 - 14) off to build my stage, so that's when all the tests will be run.
Keep going with the single frequencies. You're doing ok there. The sweep is too fast and yields no useful information. Do the single frequency test. Make notes at ever frequency. You can quantify it by the level of vibration. Walk around the entire house. See what is vibrating outside the room and see if that vibration is causing something audible to occur. SPL needs to remain the same for each test. Then, when you do the sand, do the exact same test. See if there was a noticeable difference in vibration from the first test. This test really doesn't need a measureable quantity. I know you want to for the science aspect, and you can run different tests. That's why it is important to really sit down, write a hypothesis, develop your test methods, and measure the results then report it. Not everything must have a numerical quantity. And yes, if something rattles at 53hz it may not rattle at 54 Hz, but it may rattle something FAR AWAY from the room. Just the way it is.

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Last edited by SierraMikeBravo; 11-01-2014 at 06:27 PM.
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post #60 of 343 Old 11-01-2014, 09:21 PM
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I am really interested to learn of your results, Granroth!

I am building a theater above my garage and sand in the stage is not an option for me. The rafters will simply not support it.

I am more interested in the audible differences inside the room with the various fillers. I am surprised there is no quantifiable data (white papers, etc.) on the stage filling options.
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