Hi there-
I'm building a drum room, 290cm H x 278cm W x 280cm L (just the size of the available space),
currently the walls are office-divider-type material ie cottom->foam->particleboard->space->particleboard->foam->cotton, bar one wall which is straight particleboard, while the ceiling is also divider material and the floor is flat concrete.
Noise from outside isn't so much an issue, and I actually Really like the current reflected sound of the room, except that there's simply Too Much reflection. So it's not an issue of taming any particular frequencies in this case (though that might become more important after treatment).
Three questions:
1. The concrete floor seems a bit too much reflection for drums - particularly overheads - I was thinking about constructing a floating floor of concrete->compressed fibreglass->wood supports->air gap of 8cm (I have room)->wood supports->plywood. All up this would subtract about 12cm from the room height, which in this case doesn't matter.
Would this construction help with ground reflection and reduction of room ambience?
2. I'm going to be putting 2 or 3 bass traps on the ceiling - would you recommend higher or lower freq traps in this case?
3. To further reduce overall reflection without changing the tone of the reflection significantly, what would be the best treatment for the walls? I'm open to all thoughts here.
Thanks in advance, and let me know if you need more information.
Cheers,
Matt
Questions regarding floating floor and wall construction
Originally posted at johnlsayers.com, topic 17360.
"1. The concrete floor seems a bit too much reflection for drums - particularly overheads - I was thinking about constructing a floating floor of concrete->compressed fibreglass->wood supports->air gap of 8cm (I have room)->wood supports->plywood."
You can use area rugs...you do not have to modify the entire area just to satisfy this issue.
In any event this floating floor stinks as an option, and here is why. Typically the air in an air space is made up of air and the included insulation. So if you have insulation, then you have air, which is in effect the decoupling mechanism of this assembly.
Now if you add wood supports, what does that do? And then you aid another air gap? And then yet again wood supports?
Why not just the compressed glass then cover that with 2 layers of plywood(dense) running one direction and the next layer running perpendicular to the first layer?
Wouldn't that be easier?
But, to be fair, not knowing what kind of sound issues you are up against, even the decoupled floor might not help at all.
If the structure is making a lot of noise then you have to attack that since making this decoupled floor only stops some of what is happening with the floor.
It does not even remotely change or offset the large glass windows, the hard reflective overhead.
And having basically cubicle partitions, well, there again, that is going to suck the sizzle right out of your sound, like if you installed carpet on the walls, same type of effect.
I guess in the end, I would go slow...area rugs, since all you are looking to address is the hard surface of the floor concrete.
by the way...this room you are referring to is almost cubed, if not in fact cubed...that means that all the dimensions (length AND width AND height) will reinforce one another making for a very boomy environment.
The 278cm W x 280cm are definitely the same number (converts to 109 inches and 110 inches respectively) and 290cm=114 inches...not much difference to even matter.
It's not the concrete surface, its the cube you are in that is making it so difficult to make music that matters.
Thanks, but I don't understand this comment. Area rugs will only ameliorate certain frequencies, and certainly will do nothing for bass reflection. Why do you recommend them over more resilient insulation?You can use area rugs...you do not have to modify the entire area just to satisfy this issue.
Thanks, I probably didn't describe this accurately. Mostly there will be no wood between the insulation and the airspace, the wood supports only cover maybe 1/8th of the horizontal layer. They are merely to create the air gap.Now if you add wood supports, what does that do? And then you aid another air gap? And then yet again wood supports?
My understanding (based on the bass traps I've built and schematics of those) was that having an air gap was preferable for bouncing/absorbing more frequencies - would you agree?Why not just the compressed glass then cover that with 2 layers of plywood(dense) running one direction and the next layer running perpendicular to the first layer?
No structural noise.If the structure is making a lot of noise then you have to attack that since making this decoupled floor only stops some of what is happening with the floor.
No glass windows or reflective overheads at this stage. Ceiling is same material as walls.It does not even remotely change or offset the large glass windows, the hard reflective overhead.
As noted I quite like the sound it's got, the foam on the partitions is nowhere near as thick as carpet, but I get your point. I failed to mention, one of the walls is straight particleboard rather than partitions (updating first post). But I can always add reflective surfaces if I need to. The issue I'm asking about - which I made clear in the OP - was simply reducing reflection across all frequencies.And having basically cubicle partitions, well, there again, that is going to suck the sizzle right out of your sound, like if you installed carpet on the walls, same type of effect.
Hi Matt. Welcome! :)
Could you be a bit more specific by what you mean with "there's simply Too Much reflection"? Do you really mean "reflection", or are you talking more about reverberation? Or resonance? Or is it modal issues? Would you classify it as "boomy" or "honky" or "tinny", or something like that?
As Brien already pointed out, your room is nearly a cube, so I strongly suspect that what you are hearing is related to modal behaviour. The Bonello diagram for your room is all over the place, and really ugly, so I'm not surprised that there are issues in there.
Concrete is actually a great surface, acoustically, for too many reasons to go into here. It's far more likely that your ceiling and walls are giving you problems. And if your overheads are sounding to "live", then like Brien said, a common solution is a large rug on the floor under the drum kit. Yes, that only really deals with highs, but that's usually what the issue is with overheads and floors. If you do that and still have problems, then it most likely isn't the floor that's causing it.1. The concrete floor seems a bit too much reflection for drums - particularly overheads
That sounds rather like a drum riser to me. Those are normally used to keep impact noise out of the the building structure bu isolating the kit from the floor. But it won't help much with resonance or reflections: plywood isn't much different than concrete in that respect, and you run the risk of creating yet another resonant cavity in the room, tuned to an unknown frequency and with an unknown Q.I was thinking about constructing a floating floor of concrete->compressed fibreglass->wood supports->air gap of 8cm (I have room)->wood supports->plywood.
Bass traps on the ceiling would not be effective. Bass traps normally go in the corners, where they are fare more effective. That's a small room, so it would be a good idea to put some traps in at least a few of the corners, but with care: if you already like the sound of the room, you run the risk of making it too dead by adding plain bass traps. You need to design them to keep the highs in the room, and only kill the bass.2. I'm going to be putting 2 or 3 bass traps on the ceiling - would you recommend higher or lower freq traps in this case?
Before deciding on that, I reckon your best bet would be to actually measure the room acoustics, with REW, and post the results here so we can see what is going on in there, and then figure out what to do about it: Most likely you'll need a good sized cloud above your kit (probably hard backed and angled), some absorption on a couple of walls, and perhaps a couple of slot walls at shallow angles on the other two, to help damp the modal issues and resonance a bit.3. To further reduce overall reflection without changing the tone of the reflection significantly, what would be the best treatment for the walls?
:shock: That's actually a pretty tall order! For some of the frequencies you can fit hundreds of wavelengths across the room between two walls, but at the other end, you can't even fit a tiny fraction of one single wavelength! Reducing "reflection" across the entire spectrum evenly, is pretty tough, and you don't have anywhere near enough wall area to do that: Some devices would have to be dozens of square meters, others relatively small. Different parts of the spectrum behave differently: high frequencies are very specular and highly directional, lows are highly diffuse and not at all directional Long waves wrap around small objects, mids diffract at the edges, highs just bounce off. It sounds to me like you might need maybe some polys or tubes to that mix of treatment I suggested. That might help too keep the room live while still treating the modes. Anyway, start by downloading REW if you don't already have it, then run the tests and post the results. - Stuart -The issue I'm asking about - which I made clear in the OP - was simply reducing reflection across all frequencies.
Hi, Well, reverberation is reflection, but no I'm not talking about specific frequency buildup, so yes. The current reflected sound is fine - neither honky tinny or boomy, but there's too much of it. I think that's sufficient. So the solution is to create more absorption. I have enough bass traps of various measurements (low, low-high, mid) to fit out the entire room, but I'd prefer to treat the walls directly or tack onto the existing structure and save the traps for the main rooms.Could you be a bit more specific by what you mean with "there's simply Too Much reflection"? Do you really mean "reflection", or are you talking more about reverberation?
Well, depending on what drum mic config you use. If you're using a glynn-johns or recorderman setup, which I tend to do, then the balance of lows in the overheads is critical. You may be right though, I don't really have enough experience setting these rooms up to judge.Concrete is actually a great surface, acoustically, for too many reasons to go into here. It's far more likely that your ceiling and walls are giving you problems. And if your overheads are sounding to "live", then like Brien said, a common solution is a large rug on the floor under the drum kit. Yes, that only really deals with highs, but that's usually what the issue is with overheads and floors. If you do that and still have problems, then it most likely isn't the floor that's causing it.1. The concrete floor seems a bit too much reflection for drums - particularly overheads
Gotcha. Okay I understand now. Still could be useful for the isolation purpose for me, but I will think about it.That sounds rather like a drum riser to me. Those are normally used to keep impact noise out of the the building structure bu isolating the kit from the floor. But it won't help much with resonance or reflections: plywood isn't much different than concrete in that respect, and you run the risk of creating yet another resonant cavity in the room, tuned to an unknown frequency and with an unknown Q.I was thinking about constructing a floating floor of concrete->compressed fibreglass->wood supports->air gap of 8cm (I have room)->wood supports->plywood.
Gotcha.Bass traps on the ceiling would not be effective. Bass traps normally go in the corners, where they are fare more effective. That's a small room, so it would be a good idea to put some traps in at least a few of the corners, but with care: if you already like the sound of the room, you run the risk of making it too dead by adding plain bass traps. You need to design them to keep the highs in the room, and only kill the bass.2. I'm going to be putting 2 or 3 bass traps on the ceiling - would you recommend higher or lower freq traps in this case?
Good ideas - but I thought you were against traps on the ceiling? Or are you differentiating between hanging traps and traps flat against the ceiling. Some angled semi-walls might be a good idea, so thanks-Most likely you'll need a good sized cloud above your kit (probably hard backed and angled), some absorption on a couple of walls, and perhaps a couple of slot walls at shallow angles on the other two, to help damp the modal issues and resonance a bit.
Yes I understand that, it was just a general question regarding best methods for broadband absorption in this particular environment.:shock: That's actually a pretty tall order! For some of the frequencies you can fit hundreds of wavelengths across the room between two walls,The issue I'm asking about - which I made clear in the OP - was simply reducing reflection across all frequencies.
[/quote] I don't actually get the point of that. As I said, I'm happy with the current reverberation freq balance. It's just a matter of reducing it - across as much of the spectrum as possible - to about half of what it currently is.Anyway, start by downloading REW if you don't already have it, then run the tests and post the results.
Actually, no it isn't, technically. Yes, people use the two terms interchangeably, but acoustically they are different. Saying reverb is the same as reflection is like saying running around the block is the same as a taking a single step... :)Well, reverberation is reflection,
If you use Recorderman (my personal favorite) then your overheads are pretty low to the kit anyway, so the kit itself is blocking the mic's view of the floor and therefore most of the high reflections, so that doesn't seem to be your problem. And you also don't have any phasing or timing issues on either lows or highs in the overheads, so what you are getting is mostly clean, direct drum sound without too much "room" anyway. So if you are getting too much room reverb in your overheads with Recorderman, then you really do have a major room issue!If you're using a glynn-johns or recorderman setup, which I tend to do, then the balance of lows in the overheads is critical.
A cloud is not a bass trap. I'm not against putting bass traps on the ceiling: It's just that it doesn't make much sense, acoustically, to put them on the ceiling if the corners are available. Why put it in 2-pi space if you can get the huge boost from pi or even 1/2-pi? More "bang for the buck", for free. But apart from that, I'm not talking about a bass trap: I'm talking about an angled, hard-backed ceiling cloud, which will do several things. The hard back will help (marginally) with any vertical room modes and flutter echo in the vertical plane, the angling re-directs and breaks up any standing waves that happen to involve the ceiling (axial, tangential or oblique modes that have the ceiling as one of their vertices), and the absorption damps those as well as damping first-order reflections coming back at your overheads from above. It won't do much at all for bass, since it isn't meant to be a bass trap, but will do wonders for the rest.but I thought you were against traps on the ceiling?
A bass trap flat against any surface is pretty ineffective anyway! (Unless its a membrane trap, in which case that would be the best place for it). Absorption works on the velocity component, which is zero at the wall surface, so absorption directly against the walls won't do much for normal incidence sound. That's why superchunks in corners are so effective: There's pretty much NO angle where sound can be normally incident to a flat surface behind it.Or are you differentiating between hanging traps and traps flat against the ceiling.
That IS the entire point of it! You don't even know what your room response looks like at present in the frequency domain or the time domain. Everything you know about the room is purely subjective, but acoustics is a science that deals with objective data. What you call "too reverberant" I might consider "too dead", or vice-versa, but REW will reveal exactly what it is, objectively. How can you design treatment to treat the room evenly across the spectrum and over time, when you don't even know what the room is doing? If you don't know, objectively, what the RT times are for each area of the spectrum, how can you treat the room as a whole to keep those in the same relationship? You also seem to be confusing frequency-domain with time-domain. Your issues in that room have very little to do with the actual basic frequency response of the room itself, and very much to do with how that changes over time as the standing waves release their energy, and the reverberation dies out. That's what a REW waterfall plot will reveal.I don't actually get the point of that. As I said, I'm happy with the current reverberation freq balance. It's just a matter of reducing it - across as much of the spectrum as possible - to about half of what it currently is.
In a room with those dimensions, you won't be able to do much at all for the part of the spectrum below 154 Hz, which is the Schroedinger frequency for your room. From 154 to 616 Hz, you stand a chance of at least affecting things to a certain extent, and above 616 Hz it should be relatively easy. But from 616 up is not where your real problem are anyway. Theoretically, you need something like 260 sabins of absorption in there to achieve ITU recommendations, but you don't want to go that far, and we have no idea how much you already have (not much!) so you need more like maybe 100 or so, and you need most of that to be installed in such a way as to not kill the highs and concentrate on the lows. Put maybe 20 of that in the cloud, 50 or 60 in the corner bass traps, and the rest on the walls, in patches. In fact, I'd put the rest all on one single wall, checkerboarded. I'd start on that basis, so how it goes, then decide on what more to do, (if any). A couple of photos of your room would help a lot to understand what you are dealing with. (And so would a REW analysis! Without REW, it's all just guess-work, based on subjective comments). - Stuart -It's just a matter of reducing it - across as much of the spectrum as possible - to about half of what it currently is.
Thanks Stuart, all good advice. Will get back to you once I have a REW plot, though it might be a while.
Cheers,
M
Well, great advice, a whole lot of hoops to go thru, and it is still a cubed room with little thanks at the end of the day.
What was it Everest stated, cubed rooms are anathema?
Well, we work with what we have.
Cheers,
Matt