705, high and mid freq

[loaf]

from what I've read, panels that use 705 are not useful for high and mid frequencies - they are more for bass frequencies - so for general flutter echo, high and mid frequencies I should use 703 - have I got this right?

[Glenn Kuras]

yes 703 will work a bit better, but there is not like 705 will not work. As far as the low end it does work a bit better then 703, but 703 is the best bang for the buck.

Glenn

[loaf]

thanks - I still wonder if maybe foam is better for the higher frequencies for tracking purposes - quite a few people seem to cover their fibreglass traps with foam don't they?

[avare]

Originally Posted by loaf

thanks - I still wonder if maybe foam is better for the higher frequencies for tracking purposes - quite a few people seem to cover their fibreglass traps with foam don't they?

No and no.

Andre

[loaf]

oh yes they do!

[666666]

Originally Posted by loaf

oh yes they do!

I never heard of anyone covering fiberglass traps with foam.

But ironically, I was actually thinking of doing this because I wish to wrap my fiberglass in thin plastic sheeting to seal in any potential odor / dust from the fiberglass, and I certainly do not want to have the plastic sheeting exposed to the room... because it sounds bad! (Yes, I tested it.) Even covering plastic sheeting with thin material might not be enough... so the next best thing I figured was to add a thin layer of foam over the plastic-wrapped fiberglass. Was just an idea anyway. Thin foam should, in my unscientific opinion, eat up whatever ultra high frequencies would have been reflected by the ultra thin plastic sheeting... and then all frequencies below will pass right through and be eaten up by the fiberglass. But if it wasn't for the plastic sheeting issue, I wouldn't see any reason to add foam in front of fiberglass. I never detected that such a practice was necessary... and I've never seen it done.

[Weasel9992]

Originally Posted by loaf

oh yes they do!

I'm not sure what the point of that would be...

Frank

[loaf]

I think the idea is to get a more broadband effect, presumably they feel the fibreglass is a bit too rigid to help with the higher frequencies for tracking acoustic instruments etc - I'm talking about people who track and mix in the same room

[Weasel9992]

Originally Posted by loaf

I think the idea is to get a more broadband effect, presumably they feel the fibreglass is a bit too rigid to help with the higher frequencies for tracking acoustic instruments etc - I'm talking about people who track and mix in the same room

I understand what you're saying, but rigid fiberglass of the right type works just fine for mids/highs. There's really no reason to use foam on top at all.

Frank

[loaf]

ok, I'll take your word for it - so if you've got a boxy, nasty sounding room I assume you'd have to have quite a few traps on the walls, not just covering the corners and the reflection points, to get a reasonable recording/mixing environment?

[Weasel9992]

Originally Posted by loaf

ok, I'll take your word for it - so if you've got a boxy, nasty sounding room I assume you'd have to have quite a few traps on the walls, not just covering the corners and the reflection points, to get a reasonable recording/mixing environment?

If you're starting off with a rough-sounding room, then yes...definitely. Depending on the size and real character of the room diffusion might come in handy as well.

Frank

[Ethan Winer]

There's one reason I can think of why someone would cover rigid fiberglass with foam, but the improvement would be small. All flat absorber panels are less effective for sound arriving at a shallow angle. So for the side-wall reflection points, covering rigid fiberglass with wedge shaped sculpted foam with the grooves running up and down will absorb more than a flat panel. But this is mostly theoretical, and in practice I haven't found that necessary. The RFZ Panels on the sides of my living room are made from 705, and imaging and clarity are outstanding. So I never felt that more absorption is needed.

Below is a graph comparing that side-wall with and without 705 rigid fiberglass. Yes, there's some ripple with the RFZ Panels in place, but I'm not convinced covering them with foam would help further because the source of that ripple is likely reflections from elsewhere in the room.

--Ethan

[Glenn Kuras]

There's one reason I can think of why someone would cover rigid fiberglass with foam, but the improvement would be small. All flat absorber panels are less effective for sound arriving at a shallow angle. So for the side-wall reflection points, covering rigid fiberglass with wedge shaped sculpted foam with the grooves running up and down will absorb more than a flat panel. But this is mostly theoretical, and in practice I haven't found that necessary. The RFZ Panels on the sides of my living room are made from 705, and imaging and clarity are outstanding. So I never felt that more absorption is needed.

I would agree but yes VERY theoretical IMO.

Glenn

[benevis66]

I thought you we all talking about polystyrene to begin with.Just posting to say i'm guilty of this , is it completely pointless? it still is a broadband absorber isn't it? basically the exterior layer just has a different density and pyramids,right?plus it looks good which id the most important part,RIGHT?

[loaf]

foam covering instead of fabric - that looks excellent

[Glenn Kuras]

Originally Posted by benevis66

I thought you we all talking about polystyrene to begin with.Just posting to say i'm guilty of this , is it completely pointless? it still is a broadband absorber isn't it? basically the exterior layer just has a different density and pyramids,right?plus it looks good which id the most important part,RIGHT?

I would say it is not "pointless", but covering it with fabric would have been just fine. Leave it you're in good shape.

Glenn

[loaf]

I dunno, I feel a bit sorry for foam - so neglected these days what with all this fibreglass - I think a fairer approach is to follow benevis66's example