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DIY trap for 50Hz problem room mode? Help please!

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DIY trap for 50Hz problem room mode? Help please!

Postby Domsmart » Fri May 04, 2012 12:02 pm

I was wondering if anybody could help...

I'm in the process of adapting the living room at the apartment I've just moved to, so that it's usable as a studio for my music production. Unfortunately it sounds terrible at the moment, by far the worst problem being a massively long boomy tail at 50Hz...with strong modes at 100 and 150.

This is caused by the fact that the "front" and "rear" of the studio/room are hard brick walls 11.5 ft apart, with the speakers firing right into the back wall. Unfortunately as this is my living room as well, I can't afford to lose too much space by putting thick traps on the rear wall...10-15cm would be the absolute maximum, and to compound matters the flat is rented and I can't go screwing things into the ceiling or wrecking the walls.

There is however some space to the left and right of the speakers where I could potentially put bigger traps.

Can anyone recommend the best way to damp these awful room modes? There's no way I could even begin to mix in the room at the moment and I need to do something about it pronto!

Help much appreciated
Dom
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby sheggs » Fri May 04, 2012 1:23 pm

Hi Dom,

With smaller rooms like yours the problem is normally the bass. What have you got in the corner of the room? Have you the space to put any bass trapping in there. I realise its your living room but you can either adapt or get some pre made very good corner traps that are not obtrusive and can be used a s part of the decor?
The corners are gonna be key to trating those lower frequencies. You will want to treat those immediate points around the speakers as well, some first reflection trapping there would help in that 100-150 hz range
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Martin Walker » Sat May 05, 2012 12:17 am

I agree with sheggs - the corners are your best bet, and you don’t have to screw things into the walls either. Many musicians simply push their floor-mounting corner traps into place, or prop smaller traps up against the corners on wooden legs to lift them off the floor.


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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Domsmart » Tue May 08, 2012 12:43 pm

Thanks for the replies...

I spoke to a mate who does studio builds, who recommended RW5 Rockwool. I'm going to put a few 100mm slabs of that on the rear wall and behind the speakers to tame the first reflections, and then build some large corner traps by sticking several slams together...hopefully that'll help...I'll report back with the results...
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Glenn Kuras » Tue May 08, 2012 8:05 pm

Domsmart wrote:Thanks for the replies...

I spoke to a mate who does studio builds, who recommended RW5 Rockwool. I'm going to put a few 100mm slabs of that on the rear wall and behind the speakers to tame the first reflections, and then build some large corner traps by sticking several slams together...hopefully that'll help...I'll report back with the results...

Putting 100mm is not really going to hit 50hz all that much. If you cover the whole wall it might help a bit but not cure it. You are much better off straddle the panels in the corner (I would actually fill the corner to hit 50hz) with thicker panels spaced off the wall (200mm) and or do something tuned.

BTW are you sure you know you are having the problems in that area? It might be best to test the room before moving forward. The following program is free for testing.
http://www.gikacoustics.com/video_rew_room_eq_wizard_tutorial.html
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Domsmart » Wed May 09, 2012 1:30 pm

Glenn Kuras wrote:
Domsmart wrote:Thanks for the replies...

I spoke to a mate who does studio builds, who recommended RW5 Rockwool. I'm going to put a few 100mm slabs of that on the rear wall and behind the speakers to tame the first reflections, and then build some large corner traps by sticking several slams together...hopefully that'll help...I'll report back with the results...

Putting 100mm is not really going to hit 50hz all that much. If you cover the whole wall it might help a bit but not cure it. You are much better off straddle the panels in the corner (I would actually fill the corner to hit 50hz) with thicker panels spaced off the wall (200mm) and or do something tuned.

BTW are you sure you know you are having the problems in that area? It might be best to test the room before moving forward. The following program is free for testing.
http://www.gikacoustics.com/video_rew_room_eq_wizard_tutorial.html

Thanks for that, the video is really helpful - I'll get one of those Mics and download that software and give it a go.

As for my assessment, I made it by playing tone sweeps as well as individual notes, and just listening to the results. Although much more low-tech, there is clearly a long and very resonant book at 50Hz - tones played at this frequency clearly linger for a long time, and the effect is very pronounced at this particular frequency. I suspected this was because of the parallel brick walls at the front and rear of the room, and doing the maths would indicate that this is indeed the case (they are 11.5ft apart which yields a mode of 50Hz).

I am aware that a 10cm absorber won't do much at this frequency, but unfortunately I can't afford to lose much more than this off the depth of the room because it also needs to function as a living room. I was hoping that such absorbers might at least damp the 100Hz and 150Hz modes and tame the ringy reflections at higher frequencies, and that I might be able to tame the sub bass a little by building some chunkier corner traps.

I was wondering however if it'd be a good idea to build a couple of plywood panel traps for the front wall behind the speakers...but I don't really know if this would work or where to start. would this be a good idea, and does anyone have a good design for such a trap?
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Martin Walker » Thu May 10, 2012 11:37 pm

Domsmart wrote:I was wondering however if it'd be a good idea to build a couple of plywood panel traps for the front wall behind the speakers...but I don't really know if this would work or where to start. would this be a good idea, and does anyone have a good design for such a trap?


Hi Dom!

I'd stick to broadband absorbers if I were you - simpler to implement, and in a small studio you can almost never have too much broadband absorption

Get traps straddling all the vertical and horizontal corners and you're far more likely to squash that 50Hz problem IMO than with plywood traps behind the loudspeakers


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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Domsmart » Thu May 17, 2012 12:26 pm

Thanks for the advice...so far I have constructed 3 panel traps from 100mm RW5 Rockwool with one more under construction for the front/rear parallel walls. These seemed to have killed the "ringyness" and some of the high bass hump. The next phase will be to add some deep bass trapping, however I'd appreciate some more advice on this...

Unfortunately as this is a living room, I am somewhat limited as to the amount of space I can take up with trapping. I could potentially fill the rear-left corner of the room with a "superchunk" from floor to ceiling, however putting such traps in the other corners is a no-go (well maybe at a push the front right corner, but definitely not the other two as they have a door/window respectively).

Would it be a waste of space/time/money just having a single superchunk, or would it still be useful? Assuming it is a good idea, is RW5 Rockwool a good material for such a trap? Also would a 60cm square corner trap work much better than a triangle of half the volume?

Whilst I would prefer broadband trapping, seeing as space is at such a premium here...I'm wondering whether panel traps or something similar might be a more effective use of space for taming the <100Hz region?...Can anybody point me to any good designs for such traps?

Any advice much appreciated!
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby sheggs » Thu May 17, 2012 2:51 pm

Have you had a chance to test the room yet to see where your problem areas you are left with are?

General rule with bass is that even one corner will help as opposed to having no bass trapping at all. Like Glenn said though you could also use panels to straddle the corners as an alternative but the square 'soffit' style corner trap will just be as effective as a triangle tra and bigger will help but definately worth measuring your room to see where you are
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Re: DIY trap for 50Hz problem room mode? Help please!

Postby Domsmart » Fri May 18, 2012 9:05 am

My measurement mic should be arriving today! I'll do some measurements and post...
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