Rockwool distribution- corners vs walls?

[Nyiregyhazi]

Having been getting way too much boominess in my tiny room (with a 6ft grand piano taking up well over half of both the length and width of the room) I've bought a whole load of rock wool to start putting around. I've got four slabs of the 4 inch thickness at 45kg/m3. So far I've tried putting one slab in a duvet cover and propping it up on the corner which the piano goes in, from the lid to ceiling. I presume this would be my most important corner of all? Just one slab already seems to clean up the lowest octave plenty, although not so much the octave below middle C (which seemed the worst register in recordings).

Having read loads of different threads, I'm wondering now about the best distribution. To be honest, the room actually sounded fine to me from my playing position although the boom was severe when recording, even inside the piano lid. In a sense I don't necessarily want to make the room overly dead (full on dead clarity isn't the most satisfying thing for everyday practise), but just do what I can to avoid really ugly distortions. Anyway, the consensus seems to be that corners are the way to go for bass accumulations, but I've also read threads like this where they are just hung from walls.

https://www.gearslutz.com/board/bass-tr ... piano.html

I'm probably in a position now where anything I did would be significantly better than nothing, but I'd like to get some idea of where my main focus should be. The room is small enough that there's no way I can stack triangles up in corners, so I'm looking at either positioning four whole slabs, or potentially breaking them into something the size of a pillow or so- in which case I could take every upper and lower corner and potentially even double up to an 8 inch thickness. I've seen a lot of pictures where people just hang a slab in the middle of corner walls, but surely it's better to have a smaller slab in each three way corner, than a longer slab running in the middle of where the two walls meet? Either way, I couldn't run a single slab in the middle of the corner with the piano, as it's right against the wall, but I could go with a pillow sized amount in both upper and lower ends of the corner.

I've also got a hard tiled floor and was wondering both about putting one whole slab directly under the piano (vs leaving an old duvet underneath, at the moment) or whether I should also run big slabs on the wall in addition to/ instead of taking out all corners? As I say, I don't need to kill the reverb outright, so maybe I'm better off sticking to the corners but having some additional shaped foam elsewhere?

[Sam Spoons]

Any you put in will help improve the sound, corners mean the slabs are spaced off the wall an attenuate/absorb to lower frequencies. As you rightly say you don't want the room too dead so as many corners as it practical first (and they don't just need to be vertical corners, between the floor and wall and wall and ceiling where possible is effective too). Then, if you are listening/mixing on speakers setting some at the 'mirror points' is good, if it's just for playing/recording then the points where the first reflections of the piano come from are good, over the piano, on the wall facing etc help to tame flutter echoes and such like.

[Nyiregyhazi]

Thanks, yeah, it's largely for the recording. I'm not so worried about optimising the play back (as I listen on headphones for editing). I'll probably just start with the corners then and see if I need an extra slab for the wall opposite the lid.

Any thoughts on the walls adjacent to the piano? I know people say you shouldn't have the piano right against them, so I'm not sure if deadening around the piano is notably useful in relation to this problem, or if it's better to just concentrate on where the sound is pointed out from the lid?

[Sam Spoons]

The sound of the piano doesn't come only from under the raised the lid, the whole instrument radiates sound, but the open lid does give some directionality to the higher frequencies/overtones. Mic position and some sound absorbing around/behind the mics can help clean up the recorded sound. If you make the panels moveable initially you can experiment to find the best places before fixing them into place, a small room is always going to be a little bit 'suck it and see'.

[Hugh Robjohns]

Having read loads of different threads, I'm wondering now about the best distribution. To be honest, the room actually sounded fine to me from my playing position although the boom was severe when recording

You'll probably find that your head, when playing, happens to sit in a standing wave node so doesn't receive the bloated bass that occurs elsewhere in the room due to the standing waves. But the microphones end up in an antinode... Also, you ears/brain are much better at compensating for or ignoring uneven room responses, but mics can't.

This is a very common problem, though, especially in small rooms.

I'd start by putting your rockwool in the four room corners... but this kind of problem is notoriously difficult to treat well and considerable experimentation may be required. After the corners, it may be worth putting panels on the long wall opposite the piano, and possible on the ceiling.

Also, avoid placing too much absorption near (or under) the piano. It can quickly dull the sound.

H

[Nyiregyhazi]

Thanks for all the thoughts. I've made a total of 9 pillow sized lumps now, some in material but most of them still just in clingfilm. I haven't mounted any to the ceiling corners yet, but even just getting the floor corners is making a sizeable difference.

Any thoughts on the results here? I used the very cheap Neewer omni mikes inside the piano lid, with some editing with stereo butterfly to narrow the stereo image a little.

https://drive.google.com/file/d/1znVwmS ... p=drivesdk

https://drive.google.com/file/d/1YpUxdp ... p=drivesdk

The first is with a medium room fake reverb and the second the unedited dry results (which I hate but may be more useful to judge from) Please excuse the shoddy playing (complete with a stop, where my page turning pedal skills let me down).

I've never used EQ, but it's very clear at the start that the A flat below middle C has quite some boom to it. It particularly seems to be the octave or so below middle C that swells up in general. Do you think the sound is close enough now to do a little fine tuning via EQ, or should I concentrate more on the room first? I've got one large slab left still, so I'll probably figure out a way to mount it opposite the piano lid in future.

Also, here's a recording that I did before the rockwool and a brief clip of the same following treatment.

https://drive.google.com/file/d/1F2EtYY ... p=drivesdk

https://drive.google.com/file/d/1kpz5-Q ... p=drivesdk

It's come on a long way, but the remaining boom is still pretty annoying where it remains.

[Ariosto]

My quick listen made me think that I prefer the Mahler (last two recordings) which has no rock-wool treatment! However, even then the lower octaves are very muddy and dim so that is where the treatment needs to work. I'm afraid I did not like the sound at all where you had treated the room! But the use of the sustain pedal has a big bearing on the overall sound so maybe you should bear that in mind, although I'm not a pianist myself, so maybe I'm talking rubbish. In the room treatment examples I thought the mid and upper ranges sounded rather hard in texture, so maybe the top octaves in that treated acoustic are too dry?

[Nyiregyhazi]

Interesting. If anything I think it way be too little treble damping causing an overload. The room is tiny (probably about 9 foot by 9). At the moment most of the rockwool is in cellophane which should theoretically bounce the treble back rather than absorb much. I didn't hang a duvet in the wall for this, so I'll have to try it both ways and check.

The thing I've found is that it's usually easy to get a clear treble and much harder to get clarity on lower registers. For that reason I was miking much further away from the highest strings for a while, but finding the sound very murky. I think I may have overdone it in response to that and put the microphone a little too near the upper strings.

Are there any suggestions for good reverb plugins? My ideal is to get a clear sound in the room but then put some life back into it. I get what you mean about liking the original recording more, but I do find the boominess of the small room very annoying. It's still there at times in the treated recording but it's not swallowing so many details. With the stock audacity reverb it hits a point where things sound extremely fake, by the time I go past medium room settings. I think I'll have to see if I can find a better one, to put some more ambience back into a dryer source recording.

I'll try backing off a little with the treble Mike for now and check whether a duvet helps to take the edge off the treble.

[Drew Stephenson]

Are there any suggestions for good reverb plugins?

Have a shufti at this thread: https://www.soundonsound.com/forum/view ... 15&t=65465

[Nyiregyhazi]

Cheers, looks handy. Am I right in thinking that most paid plugins come with a free trial, by the way? I remember trying something before, where I was hoping for a kind of magic that didn't transpire and the trial was really helpful. I wouldn't want to spend big bucks on reverb but, while free is always nice, I'd happily drop a tenner or two for a notable step up (if I could check the result first).

[Drew Stephenson]

It really varies by manufacturer, the thing to do is (and this is just my personal approach with pretty much all plug-ins) try and figure out what kind of reverb you're after before you start disappearing down the rabbit hole of demos, trial versions and everything else. Otherwise you can spend a loooong time going round in circles and end up back where you started.

[Nyiregyhazi]

Are there any good threads on checking out the frequencies of a room, with a view to finding an EQ to try soften the remaining boomy frequencies? I've read a little about monitor microphones, as well as playing pink noise. At first I was thinking I couldn't really do this, seeing as I don't have a flat mike. But then it occurred to me that I'd be doing the EQ on recordings with the mikes I have rather than flat ones. So, presumably it's more useful to know the specific imbalance caused by the blend of the room and my mikes, rather than to get a flat mike and isolate the exact room imbalance? I think this makes sense, although I can't rule out a logical misstep.

[Drew Stephenson]

The logical misstep is that you're treating the room for play back as well as recording, so unless your speakers have exactly the same frequency response as your mic...
If you can find the response of your mic published somewhere you can use that as a rough guide though.
Say it's a fairly typical LDC with a broadly flat response from 50Hz to 17kHz other than a gentle presence boost in the upper mids, you can factor that boost back into your measurements fairly easily.
Chances are the areas you most need to be focusing on are lower down the range and, if your room is a typical average-size, untreated, domestic room, then you'll be seeing some big old variances in the lows and low-mids as the room modes dominate.
There was a good article on diy room treatment in last month's magazine. Worth £1 for the pdf if you haven't seen it.

[Nyiregyhazi]

Do you mean for general listening playback on speakers, or that speakers tend to imbalance the pink noise output plenty for themselves? I can use headphones for editing, so I'm not really concerned by getting a good room sound for playing back through speakers. If I do use a speaker, my priorities would just be about assessing my playing at that point, rather than to assess the sound quality.

I've already got a lot of rockwool around the room, so I'm not necessarily concerned about knowing the room's natural state. The idea now is simply to try to isolate which frequencies are still picking up the remaining boom on recordings and see whether I can fix what's left with EQ- to avoid having to add any further treatment.

Basically, I largely just need to know whether running a spectrum test through my normal mike (in the room as currently treated) would give me what I need to figure out a decent EQ adjustement on the recordings. I don't necessarily need to know how the room would be without a microphone bias- unless this screws up the previous goal.

[Drew Stephenson]

ah right, if you're just interested in the audio capture side of things that's a different ball game. The first thing to do is try different places in the room for the mic and the instrument (or source if you have a speaker you can move around for pink noise). You'll need to experiment really though.
Once you've got the sound as good as you can through instrument and mic positioning you'll probably find that EQing will be much less problematic and largely a matter of taste rather than correction. Though you might still find resonant frequencies that are distorting things heavily at the low end - these should be fairly easy to identify sonically and visually on the EQ display though.
Unless I'm still misunderstanding your challenge?

[miN2]

You can use REW to check the response of your room https://www.roomeqwizard.com/

You can buy something like this for measurement purposes (which is a steal for £28 in my view) https://www.amazon.co.uk/Behringer-ECM8 ... op?ie=UTF8

Then you can shift your treatment around and measure again to find out what each is doing in their current placement.

[Nyiregyhazi]

ah right, if you're just interested in the audio capture side of things that's a different ball game. The first thing to do is try different places in the room for the mic and the instrument (or source if you have a speaker you can move around for pink noise). You'll need to experiment really though.
Once you've got the sound as good as you can through instrument and mic positioning you'll probably find that EQing will be much less problematic and largely a matter of taste rather than correction. Though you might still find resonant frequencies that are distorting things heavily at the low end - these should be fairly easy to identify sonically and visually on the EQ display though.
Unless I'm still misunderstanding your challenge?

Yeah, it's a particularly small room, so I don't think I'll get much better than by miking pretty close. I put some audio samples earlier in the thread, with a couple before and after treatment.

I'm basically looking to get a head start on figuring out an EQ adjustment to catch the frequencies that are imbalanced in what I'm capturing so I can balance out the recordings (rather than looking to worry about whether a flatter mike would show a slightly different imbalance) Does that seem feasible from the source material?I don't want to cut the wide areas of bass down, so I'm hoping to try and catch a precise sense of what needs toning down on a more detailed graph. I tried a little with trial and error (I can tell that one or two specific notes have notable issues) but I think I'd probably waste a lot of time trying to do it all by ear, without a sense of where to look.

[Nyiregyhazi]

You can use REW to check the response of your room https://www.roomeqwizard.com/

You can buy something like this for measurement purposes (which is a steal for £28 in my view) https://www.amazon.co.uk/Behringer-ECM8 ... op?ie=UTF8

Then you can shift your treatment around and measure again to find out what each is doing in their current placement.

Thanks, does my theory make sense though- that I'd actually learn more from seeing the imbalance that results after going through the mikes I'll actually be using? It seems to me that I'd be better off bunging all the imbalances in together, than trying to isolate the room alone- given that my recordings will be involve both room and microphone imbalance combined. This makes the most sense to me in theory, although I may be overlooking something.

[miN2]

No, i don't think it makes sense if you're trying to control your room since if you want a reading of your room in an effort to tame it then you need the reading of the room. You don't actually need to measure the room, but you expressed an interest in knowing the frequencies of a room and REW gives you access to this sort of information.

If you don't like the sound of your mic then change it, don't try and acoustically treat your room to offset its tone.

[Nyiregyhazi]

No, i don't think it makes sense if you're trying to control your room since if you want a reading of your room in an effort to tame it then you need the reading of the room. You don't actually need to measure the room, but you expressed an interest in knowing the frequencies of a room and REW gives you access to this sort of information.

If you don't like the sound of your mic then change it, don't try and acoustically treat your room to offset its tone.

It's all with a view to improving recordings though. I didn't say I need to monitor the room in isolation, but that I need to be able to improve on the imbalances that are in the recording (regardless of how they divide up between room and microphone). I don't follow what the benefit would be of getting an isolated impression of the room, when the imbalances I'll be needing to fix on the recordings will be those of room plus mike combined. If I'm missing something I'm definitely interested in the explanation, but I'm not following any reason to separate these factors out, only to have to combine them once again. Surely the only effect of using a flat monitor mike is that I'll be taking something away, that I need to add back in to the consideration when balancing recordings made with a non-flat mike?

I didn't say anything about disliking the sound of the mike or that I'm trying to change the room instead of the mike. I've simply recognised that there are some remaining imbalances on the recording that likely need EQ. Having already put plenty of treatment in the room, I'm now looking for the quickest and most direct way to get a sense of which frequencies to aim the EQ at. I have no doubt that it's still chiefly a room issue, but I'm not seeing the reasoning for using a method which would factor out any contribution from the very same microphone that I'm going to be recording on anyway. Taking it's effect away and then having to put it back is surely not required?

[Sam Spoons]

A room will always have resonances at frequencies related to the rooms dimensions. These will cancel or reinforce themselves in different places in the room creating nodes and antinodes. In a small room they are inconveniently in the middle of the low end. The upshot of this is that in certain places in the room the bass will be boomy at a certain frequency and at others the same frequency will appear to be nonexistent. A neutral/flat frequency response "measurement mic" will allow you to find out where the frequency balance of your room is closest to the ideal and allow you to place your recording mics for the least coloured response. We usually use specific mics for a specific purpose because of the 'colour' so, when measuring the room you need a mic that doesn't add 'colour'.

[Hexspa]

Hey, N. Hope you're well. This is my first post in the SoS forum but I love sticking my nose in acoustics discussions. Here's my take:

From what I gather, and I haven't fully read the entire thread, you have a piano in a room and you want to use your rigid panels to improve the sound. Is that right? If so, you're best following a proven plan.

That plan is that you need a balance of modal and early reflection treatment. Luckily, the same absorbers you have do both jobs. It comes down to where you put them.

Yes, corners are great places to put panels and super chunks but they're not the only place. Corner treatments are modal-oriented. In other words, they help mitigate standing energy. No room that needs accurate bass reproduction is complete without some kind of corner treatment.

However, we've yet to cover early reflections and other modal issues. Since you're not using this space for studio-type critical listening, you can freely place panels - at least 4" thick - in an alternating pattern along your walls. Start behind the piano and work your way outwards.

By doing this, you'll minimize ringing and early reflections without making your room too dead. Any surface which is within 10' and between you and the piano that you could see yourself in were it a mirror needs a panel there. This will handle your early reflections.

As far as measuring, you just need to set up any studio monitor around where your piano is. Use Room EQ Wizard and with it you'll be able to see whether your SPL has flattened and how much your decay has been shortened. You can also take an impulse response measurement to see how you've minimized those as well.

Not sure how much I'll be posting here but, ultimately, you need to look at this holistically if you want the best results. To keep it simple, you can just start with your first reflection points - those mirror spots I mentioned - and work your way out from there. If you're still not satisfied, you can deploy corner and surface modal treatments and/or diffusion until you're content.

Thanks.

[Nyiregyhazi]

This doesn't deal with my question though--about why I wouldn't want to involve my microphone, so as to record the actual imbalances I'll be seeing on the recordings. I'm not using a flat mike on the recordings I've made, so why not involve the same mike at source? If there is a problem with doing it this way nobody has given any indication as to why it would not work. I get that you can measure the room as an independent variable, but my question is about why I would need to- when I can instead track the resultant imbalances in the same way they will show up on the recordings I'm making- allowing for effects of both microphone and room, rather than room only. It doesn't matter to me to separate them out as variables. I only need to know what the imbalance to my recordings will be.

If I isolate the room via a flat mike and then factor the actual mike in, the results are surely no different from just using that microphone to start with? Or am I missing something here? If so, nobody has clarified what. I get that there's another approach that isolates the room effects first, but I don't see what practical problems would be caused by directly measuring the (combined) imbalance that will show up on the actual mikes to be recorded on.

[Nyiregyhazi]

Hey, N. Hope you're well. This is my first post in the SoS forum but I love sticking my nose in acoustics discussions. Here's my take:

From what I gather, and I haven't fully read the entire thread, you have a piano in a room and you want to use your rigid panels to improve the sound. Is that right? If so, you're best following a proven plan.

That plan is that you need a balance of modal and early reflection treatment. Luckily, the same absorbers you have do both jobs. It comes down to where you put them.

Yes, corners are great places to put panels and super chunks but they're not the only place. Corner treatments are modal-oriented. In other words, they help mitigate standing energy. No room that needs accurate bass reproduction is complete without some kind of corner treatment.

However, we've yet to cover early reflections and other modal issues. Since you're not using this space for studio-type critical listening, you can freely place panels - at least 4" thick - in an alternating pattern along your walls. Start behind the piano and work your way outwards.

By doing this, you'll minimize ringing and early reflections without making your room too dead. Any surface which is within 10' and between you and the piano that you could see yourself in were it a mirror needs a panel there. This will handle your early reflections.

As far as measuring, you just need to set up any studio monitor around where your piano is. Use Room EQ Wizard and with it you'll be able to see whether your SPL has flattened and how much your decay has been shortened. You can also take an impulse response measurement to see how you've minimized those as well.

Not sure how much I'll be posting here but, ultimately, you need to look at this holistically if you want the best results. To keep it simple, you can just start with your first reflection points - those mirror spots I mentioned - and work your way out from there. If you're still not satisfied, you can deploy corner and surface modal treatments and/or diffusion until you're content.

Thanks.

Thanks, I've started with two pillow sized lumps in each corner, although I haven't yet found a way to attach to the ceiling corners. I've got one big slab left that I'll try for first reflections sometime opposite the lid. Would you go for one giant slab running across where the lid opens, or do you think I should break it up into three and space it out slightly?

[Drew Stephenson]

Given the fact that the room imbalances are likely to be much larger than any mic imbalance, certainly at low frequencies, the answer there is that you could use your mic and make some effective changes.
You might have an accurate measure of the mic frequency response but that's only part of the story. If it's a cardiod then you need to think about proximity effect, and the effect of off-axis reflections.
As you move further up the frequency range things get more complex, is this part of the spectrum overly bright because of the mic or the room? The treatment will be different depending on the cause; if it's the room you might need some diffusion, but if it's the mic you might just need to change the position.
Separation of the cause of the imbalances allows you to make an informed decision about any changes required. Where and how you position the mics will make a huge difference to how things sound, so if you understand your room properly you can use it to your advantage.
And that's before we get into using a different mic.