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Rockwool distribution- corners vs walls?

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Re: Rockwool distribution- corners vs walls?

Postby Sam Spoons » Tue May 07, 2019 8:54 pm

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'.
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Re: Rockwool distribution- corners vs walls?

Postby Hexspa » Tue May 07, 2019 11:28 pm

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.
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Re: Rockwool distribution- corners vs walls?

Postby Nyiregyhazi » Tue May 07, 2019 11:50 pm

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.
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Re: Rockwool distribution- corners vs walls?

Postby Nyiregyhazi » Wed May 08, 2019 12:11 am

Hexspa wrote: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?
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Re: Rockwool distribution- corners vs walls?

Postby blinddrew » Wed May 08, 2019 12:19 am

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. :)
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Re: Rockwool distribution- corners vs walls?

Postby Nyiregyhazi » Wed May 08, 2019 12:38 am

blinddrew wrote: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. :)

Okay, the thing I'm asking about is specifically in relation to editing the recordings I've been getting though, for now. I was basically fairly happy with the test recordings following treatment, aside from a few lower frequencies having some boominess. I basically just want to see how effective the results would be if I can isolate these and tone them down via EQ, rather than look to make any major changes to the room. I might investigate the treble more in future, but at the moment it's just the lower frequencies I want to work at.
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Re: Rockwool distribution- corners vs walls?

Postby blinddrew » Wed May 08, 2019 8:18 am

In which case go right ahead. Still worth using REW (or doing the maths) to make sure you're correctly identifying room modes, but at lower frequencies a lot of cardioid LDCs tend towards an omni pattern anyway. So your mic should put you in the ball park to sort your treatment - which will then make any corrective eq much easier.
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Re: Rockwool distribution- corners vs walls?

Postby Nyiregyhazi » Wed May 08, 2019 4:08 pm

blinddrew wrote:In which case go right ahead. Still worth using REW (or doing the maths) to make sure you're correctly identifying room modes, but at lower frequencies a lot of cardioid LDCs tend towards an omni pattern anyway. So your mic should put you in the ball park to sort your treatment - which will then make any corrective eq much easier.

Thanks, I'll try it out today and see how much I can clean things up after.
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