Guitar isolation panels

[SörenHjalmarsson]

You won't achieve any significant reduction in sound pressure level with porous absorbtion alone....

Read myth Nr 1 for more info: RBDG - Newsroom - Exposing Acoustical Myths


Cheers,

[the donal]

Originally Posted by SörenHjalmarsson

You won't achieve any significant reduction in sound pressure level with porous absorbtion alone....

Read myth Nr 1 for more info: RBDG - Newsroom - Exposing Acoustical Myths


Cheers,

Thanks for posting that. I think I need to get a good book on acoustics.

I guess I'd need something substantial to manage even just a few db from the amp.

[SörenHjalmarsson]

No problem! Yeah, attaining good sound isolation (between different rooms) isn't trivial.

The best would probably be to try and record with low levels, usually that yields better results anyway.... Most of Jimmy page's stuff with Led Zeppelin was recorded with 24 watt's of power hitting a 15 watt speaker, or a Supro 6L6 in which he had replaced the stock 2x10" configuration with a single 12", so that single speaker was really getting cranked.!

Cheers,

[the donal]

Originally Posted by SörenHjalmarsson

No problem! Yeah, attaining good sound isolation (even between different rooms) isn't trivial.

The best would probably be to try and record with low levels, usually that yields better results anyway.... Most of Jimmy page's stuff with Led Zeppelin was recorded with 24 watt's of power hitting a 15 watt speaker, or a Supro 6L6 in which he had replaced the stock 2x10" configuration with a single 12", so that single speaker was really getting cranked.!

Cheers,

Yeah. I'm recording with a 45 watt amp that's effing loud even with an attenuator..

[SörenHjalmarsson]

I might be wrong on the exacts there, it's been a long time since i read about Led Zeppelin (and there is alot of mystery around the whole 'Page guitar sound' thing). What is certain though, is that in order to achieve his BIG guitar sounds, Page used small, low wattage Valco speakers.... with clever mic'ing techniques.....

/Sören

[DanDan]

A recording client of mine has bought a BlackStar 1 Watt valve amp.
Great sound except for a little hum, which should be unnecessary in this millenium. They also have a 5 Watt.

In a thread here some time ago Ethan was claiming that PVB panels substantially block the room sound from the mic. This is contra much of the published wisdom which is generally similar to Soren's link.
So I tested the matter. (as it turned out of course Ethan was speaking as a result of his own tests.)
Unexpected results.
There was considerable blocking effect from a 4 inch panel.
Of course this was frequency dependent, but from memory extended usefully down to 1K or so. I will try to find the test and post here if I do.
I added a layer, then another, of clingfilm. No increase in HF blocking.
Again surprising to me.

So I expect a box of 4 inch 100KG would seriously dull the amp leakage and keep cymbals and such out of it. It would probably get very hot though!

DD

[Ethan Winer]

Originally Posted by DanDan

There was considerable blocking effect from a 4 inch panel.

Yes, the usual advice that "bass traps don't help sound isolation" applies to the very low frequencies that pass through walls and disturb the neighbors. But a reasonably thick absorber can attenuate most other frequencies quite a lot. The photos below show a very effective use of such panels around a guitar amp.

--Ethan





The Acoustic Treatment Experts

[Tone Grown]

I have very successfully reduced the amount of noise by baffling amps. I build a 4x5x4 ft baffled box with the amp inside. Same thickness baffles on the top too. The baffles are cloth on the front and mdf on the back. the thickness is Six inches of insulation.

Sent from my HTC PH39100 using Tapatalk

[SörenHjalmarsson]

If our OP's 'only' interest lies in reducing the level within the recording room, than that could be a different matter of course! Using GOBO's between preformers is quite effective....

Still i imagine that the traps needs to be effective way past 1kHz in order to achieve a significant attenuation!? Mr Winer?

The reason i'm saying that is because the electric guitar is almost entirely a midrange instrument, and i can't imagine that frequencies above 1kHz will create the most energy?

A standard tuned guitar can produce tones from 82Hz to 1kHz, and although it will have harmonics far beyond that, anything above 5kHz will drop dramatically due to the pickup's, circuitry and speakers of the amp. More than this, when recording guitars, we usually have the treble and presence knobs turned way down when recording, so as not to get a too harsh guitar sound. The amount of treble picked up by the amp microphone is usually more prominent than what we percieve it to be in the recording room. This could be because the dynamic microphones that we tend to use for this application (close to the speaker cone), more often than not, hava a slight lift in the frequency response in this region (sm57 has a lift between 2-12kHz, MD421 an even more prominent boost at ~1kHz) and the treble and presence knobs of the amp usually starts to attenuate at 1-4kHz and 3-7kHz respectively.... so that would explain why we usually turn down those knobs! Another reason might be that the human in the TR will be hearing room modes (and what not) that the close mic'ed sm57 wont be as bothered with.

Of course (as usual) this all depends on the amp, the room, the mic, the mic placement, the desired sound, etc., but this is my generalization of amp recording, take it for what it is! But to my mind, the BIG culprit when it comes to sound pressure level, WRT speaker amps, should be somewhere below 1kHz?


/Sören

[DanDan]

Found the thread for you Soren. You will probably be just as surprised as I was. i.e. Very.
absorption/reflection question
I used to believe the classic text book stuff, e.g. 3dB loss per METRE in fibre.
Tested, we find a one inch thick panel does 5dB at 500Hz and much more above.
I would imagine a four inch panel might achieve 4- 5dB at 125Hz and perhaps 8-10dB at 500Hz.
Numbers not to be taken literally, just illustrating how surprising the difference between the textbook and test can be.
Add the Fletcher Munson curves into the pot and you will see that 4 Inch panels are extremely useful in the recording room as well as the CR.

DD

[SörenHjalmarsson]

Originally Posted by DanDan

Found the thread for you Soren. You will probably be just as surprised as I was. i.e. Very.
absorption/reflection question

Yes, but i thought it must extend lower than 1K.... thanks for that DD!

Add the Fletcher Munson curves into the pot and you will see that 4 Inch panels are extremely useful in the recording room as well as the CR.

I was going to ad to my previous post that, even if the SPL meter doesn't show much of an improvement (because of the panels being effective only in the high ranges) the percieved difference from attenuating some HF could still be quite relieving for the ears.......

Isolation aside, what does it do for the recorded sound? Any difference?

/Sören

[localhost127]

Originally Posted by DanDan

F
I would imagine a four inch panel might achieve 4- 5dB at 125Hz and perhaps 8-10dB at 500Hz.

DD

are you ignoring diffraction?

[the donal]

This thread has bloomed a little- thanks for all the info.

My intention is simply to manage the level to a degree- mainly to minimise neighbour aggravation. I realise I'll not completely kill the noise. The other side of this, I suppose, is that once you wall in the amp, interaction with the guitar is somewhat compromised. But I guess in a single room home recording situation, there will always be compromises. I also need to build something that I can stow out of the way quite easily..

[SörenHjalmarsson]

Originally Posted by the donal

My intention is simply to manage the level to a degree- mainly to minimise neighbour aggravation.

Then i'm afraid that we are back to square one (my first post). Simple absorbtion won't help you to minimize sound propagation between you and your neighbours...

/Sören

[the donal]

Originally Posted by SörenHjalmarsson

Then i'm afraid that we are back to square one (my first post). Simple absorbtion won't help you to minimize sound propagation between you and your neighbours...

/Sören

But the impression I'm getting from a few threads is that some sort of isolation- like traps all the way around the amp could help attenuate some of the sound getting next door. I know that this won't help the guy downstairs much, but he's not so bothered- it's more the flat to the side of me (who clearly turn the telly up when I'm making a bit more noise. The guys above and below are pretty understanding and I'm clear that I will turn down if asked. It's more the peeps in the next building... (odd as this may sound..).

Happy to accept if I'm misunderstanding things... Acoustic treatment is a topic I haven't spent enough time on..

[SörenHjalmarsson]

Originally Posted by the donal

But the impression I'm getting from a few threads is that some sort of isolation- like traps all the way around the amp could help attenuate some of the sound getting next door.

In the threads you mention, did you see any firm data? Did they measure an objective improvement in STL (Sound Transmission Loss)? or was it merely a testimonial improvement? No matter how low the STC (Sound Transmission Class) of your building is, it won't be improved by a couple of absorbtive panels.... Those panels would have to be more in the way of something like the sealed isoboxes that are used to attenuate computer noise (but with the proper STL value of course).

Acoustic treatment is a topic I haven't spent enough time on..

Acoustics = What happens within a room
Sound Isolation = What happens between rooms

Here's the thing: The frequencies that pass through your building structure, will certainly pass through a 4" panel aswell. But even if such a panel would increase the STC of, say, your wall! Your STL will probably not change much anyway! Why? Because a chain is only as strong as it's weakest link and there is ALOT more to sound isolation than just how thick your walls are. You need to take into consideration both the structure itself, the coupling of the structure, seals, doors, windows, HVAC and ventilation, etc., etc., etc., Sound waves can travel in many ways and that's why everything in the system needs to be calculated so as to match (or exceed) the targeted STL goal.

Strange as it might seem, by adding alot of absorbtion to your room, you often make the noise outside of your room worse! Why? Because you absorb those frequencies which are percievable within your room, which then might cause you to raise your volume, and by so doing, the frequencies that pass through your walls won't seem worse to you, but they will seem worse for your neighbours!

More here: A Guide to Sound Isolation and Noise Control

/Sören

[the donal]

Cheers Sören- a lot of good points there.

D

[DanDan]

Soren, I remembered that the 1 Khz came from 50cm pyramid foam.
I wouldn't expect much of a change on the recorded sound of the amp.
The increased separation should be helpful if other instruments are being recording in the same room.
Some time a ago I recorded an 8 piece Bluegrass band in my 5x3M kitchen.
I put MiniTraps between them, and it worked out quite well.

are you ignoring diffraction?

Yes, that is why I used the term 'would imagine', and stated....

Numbers not to be taken literally, just illustrating how surprising the difference between the textbook and test can be.

Also, when an enclosure is involved, diffraction?

donal, how about a power soak?

A small extra point. Sound can travel extremely well through solids. In this case, particularly the lowest notes could travel through the floor.
A block of foam or such could eliminate that factor.

DD

[SörenHjalmarsson]

Originally Posted by the donal

Cheers Sören- a lot of good points there.

Originally Posted by DanDan

I wouldn't expect much of a change on the recorded sound of the amp.
The increased separation should be helpful if other instruments are being recording in the same room.

That reminds me.... The "isobox" (or iso booth) solution that i mentioned earlier, would seriously jeopardize the sonic quality of the recordings. I don't know what the panels would do, but until i can find out for myself i'll take DD's word for it!

[the donal]

I live in a conversion flat. Old Victorian buildings that are about as soundproof as a sock. I also have the chimney stack on 1 wall, between the neighbour and me- not ideal for soundproofing ( my Bro lives in the basement next door and can hear me quite clearly...).

I have a THD hot plate plugged into the amp. It's good and allows me to drive the amp more, but the setting on 16db-infinity really squishes the sound.