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Room acoustics, lack of bass issue.

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Room acoustics, lack of bass issue.

Postby Damo303 » Wed Jul 11, 2012 10:47 am

ok so i've moved rented property and sadly my new studio room is showing signs of poor acoustics. In particular i've noticed the bass is lacking quite a bit of low frequency. I first noticed this when I fired up my TR-808 and if I set the kick drum decay to full I cant even hear the decay of the bass drum. There is no sub frequency whatsoever.

The room is 398cm x 364cm and the ceiling is about the same hight as the walls so pretty much a 'cube'. Not good.
All the walls are made of a timbre and plasterboard construction (No solid brick walls outside).
There is carpet on the floor.
I'm using KRK Rokit 6SEs which sit on acoustic foam isolation pads.

I've positioned the monitors at ear height, due to the size and dimensions of the room the listening sweet spot ends up being just shy of the centre of the room.

I've noticed that the low end sounds more prominent in the corners of the room (all though still not as bassy as I would expect my 808 to sound) but there is definitely more presence than in the centre of the room.

I've read loads of articles today and it seems that I should be introducing bass traps to the room but one thing thats puzzling me is that the walls aren't solid brick. So shouldn't this help, as the bass frequencies are passing through the walls rather than reflecting back to the sweet spot which you would expect to cause a drop in bass frequencies? So if thats the case i'm concerned that spending a large amount of cash on bass traps might not actually improve anything.

Can anyone offer any advice of other things I could try?
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Re: Room acoustics, lack of bass issue.

Postby The Korff » Wed Jul 11, 2012 10:56 am

In all likelihood your room is the problem, and bass traps are the answer... But it's always worth doing the Derp Test. Are your speakers in phase?

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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Wed Jul 11, 2012 11:01 am

Korff wrote:t's always worth doing the Derp Test. Are your speakers in phase?

Sorry not with you, whats the Derp test? how do I test if they are in phase?
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Re: Room acoustics, lack of bass issue.

Postby Hugh Robjohns » Wed Jul 11, 2012 11:14 am

Damo303 wrote:The room is 398cm x 364cm and the ceiling is about the same hight as the walls so pretty much a 'cube' ... the listening sweet spot ends up being just shy of the centre of the room ... I've noticed that the low end sounds more prominent in the corners of the room

Yep, yep, and yep! You have discovered the very unhelpful properties of a small cube room. There is no bass at the centre, which is where you inevitably end up having to sit.

I've read loads of articles today and it seems that I should be introducing bass traps to the room but one thing thats puzzling me is that the walls aren't solid brick. So shouldn't this help, as the bass frequencies are passing through the walls rather than reflecting back to the sweet spot which you would expect to cause a drop in bass frequencies? So if thats the case i'm concerned that spending a large amount of cash on bass traps might not actually improve anything.

Certainly stud walls will allow more extreme LF bass to pass through and absorb more than brick or clock walls would, but they will still reflect an awful lot of it back into the room, and that results in the cancellations that cause tha lack of bass you're experiencing.

Yes, extensive bass trapping is the obvious solution, to aborb the bass before it can be reflected back... but in a small-ish cube room like yours it is almost impossible to install sufficient trapping to make a worthwhile difference. By the time you've controlled the reflections fully you won't be able to get in the room anymore!

Having said that, every little helps, and you can make a useful improvement by installing traps in the vertical corners, and possibly across the wall-ceiling corners if you allowed to fit things to the walls. It will never be perfect, but you might be able to make it a bit better than it currently is.

Can anyone offer any advice of other things I could try?

Invest in some good quality headphones....

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Re: Room acoustics, lack of bass issue.

Postby The Korff » Wed Jul 11, 2012 11:19 am

Oh, sorry — I was being idiomatic, I just meant checking the obvious (but easy-to-overlook) problems.

I just re-read your post and you're using active monitors, so that's unlikely to be the case, but if there's anything in your monitoring chain (a monitor controller or mixer, maybe?) it's possible that the polarity of either the left or right channel has been inverted somewhere... Do you have a way of flipping the polarity of one channel relative to the other, or do you have any non-standard cables (eg. Pin 3 hot XLRs) in your setup?

The quickest way to check is just to invert one channel and listen. If the sound goes from being dreadful and slightly disorientating to good, then you've solved your problem. If it goes from sounding alright to awful, then it's not a polarity issue.

Like I said though, it's much, much more likely that you just need bass traps, and possibly to move your speakers around until the nulls in your room are less severe.

Cheers!

Chris
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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Wed Jul 11, 2012 11:29 am

thanks, I guess at this stage all I can do is move the speakers to different areas in the room and see if that helps. There is a cupboard and fireplace in the room so those objects may help the speakers in some areas.

Currently the monitors are facing the fireplace with the cupboard on my left side.

Can you recommend some cheap bass traps? The RealTraps stuff looks good but very expensive.
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Re: Room acoustics, lack of bass issue.

Postby Mike Stranks » Wed Jul 11, 2012 11:44 am

Damo303 wrote:Can you recommend some cheap bass traps? The RealTraps stuff looks good but very expensive.

What's your definition of "cheap"?
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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Wed Jul 11, 2012 11:55 am

CHEAP, I live in Australia, everything is expensive.

The Auralex stuff retails for $399 for 4 bass traps here. Thats pretty expensive for some foam panels and I wonder if some of the unbranded companies who make similar looking foam products do just as good a job?

The RealTraps panels seem to be about $500 a panel so i'm looking at $2000 for the bear minimum. Crazy prices.
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Re: Room acoustics, lack of bass issue.

Postby James Perrett » Wed Jul 11, 2012 2:43 pm

Damo303 wrote:
Can you recommend some cheap bass traps? The RealTraps stuff looks good but very expensive.

DIY is usually cheapest. Not sure what you can buy where you are but a bale of Rockwool, a few yards of Cara fabric and a few metres of wood will get you 3-4 traps for around 50 pounds in the UK.

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Re: Room acoustics, lack of bass issue.

Postby Hugh Robjohns » Wed Jul 11, 2012 4:00 pm

As James says, you'd be best advised to build the traps yourself. It isn't difficult.

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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Wed Jul 11, 2012 11:35 pm

ok i'll give it a go, would this be a good tutorial to follow, do these look adequate:

http://www.youtube.com/watch?v=iyYUpkpL0gw

or can you recommend a trusted tutorial/article to follow for building your own bass traps?
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Re: Room acoustics, lack of bass issue.

Postby Santarosa » Thu Jul 12, 2012 12:48 am

This is a good and easy way to make a DIY trap. I did a similar one. The one showed in the video would fit for corners. If you plan to make some traps for the walls as well you should make a deeper wood frame. The advise here is to have the same depth of air space as you have of absorbent material. So if you have 100 mm of rock wool you would want a frame of 100 mm. This way building a model based on that video will give you 100 mm of air gap between the absorber material (say 100 mm thick rock wool) and the wall.

I am almost finished with my DIY acoustic treatment. I'll then make some measurements and will post the results and impressions. I'm going to post some pictures too.

As Hugh said though, a good advise would be to buy a good pair of headphones. I have the HD 650 myself. There are a lot of threads about good headphones for mixing and also a fairly recent (2011 I think) SOS issue that cover the subject of headphones.

My advise would be to have different systems to check your mixes. Before making the acoustic treatment of my room I used the headphones most of the times and checked the mixes constantly in different systems, which are: my HD 650 headphones, a pair of HI-Fi speakers, a pair of AE22 studio monitors and a Auratone alike mono speaker. All of them sounded different and when I had a good balance between them all it was a sign I was approaching a good balanced mix.

Good luck with your acoustic challenge.

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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Thu Jul 12, 2012 8:50 am

Santarosa wrote:This is a good and easy way to make a DIY trap. I did a similar one. The one showed in the video would fit for corners. If you plan to make some traps for the walls as well you should make a deeper wood frame. The advise here is to have the same depth of air space as you have of absorbent material. So if you have 100 mm of rock wool you would want a frame of 100 mm. This way building a model based on that video will give you 100 mm of air gap between the absorber material (say 100 mm thick rock wool) and the wall.

Sorry just to be clear - are you saying that the wall panels should have an air gap and not the corner ones?
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Re: Room acoustics, lack of bass issue.

Postby sheggs » Thu Jul 12, 2012 9:11 am

With corner panels it would depend how you are making them. If you are building a panel and straddling the two walls into the corner then yes too an air gap.
If you are making superchunks then these work on the depth from the corner so you are better filling the gap with cheap fluffy insulation
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Re: Room acoustics, lack of bass issue.

Postby Hugh Robjohns » Thu Jul 12, 2012 9:20 am

Acoustic absorbers work by taking energy out of the sound wave, and most do that by slowing the moving air particles down by forcing them to weave their way through open-cell foam or between the fibres of mineral wool.

By definition, there is no air particle velocity close to the wall. There's lots of pressure, but no velocity. So putting absorbers like foam or mineral wool against the wall is a complete waste of resources. These absorbers are most effective where the air particle movement is at the greatest, which is a quarter wavelength from the wall.

Hence the effective compromise suggested above of spacing the absorber away from the wall by the same distance as its own thickness. This works extremely well for wall panels, but the same principle applies to corner bass traps, it's just that most designs don't bother becuase it's easier to fill the corner completely -- especially with foam designs which rely on the 'inner' foam for attachement and rigidity. If you're building a frame for rockwool, then leaving a gap behind works well.

PW and I took that approach in this Studio SOS, using the same basic wall panels for the corners too, although we also enhanced their capability for controlling low bass by adding a limp membrane in the gap.

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Re: Room acoustics, lack of bass issue.

Postby Damo303 » Thu Jul 12, 2012 11:41 pm

many thanks, i'll give these a go, they look ideal. Thanks. I'm also going to get some decent headphones - the HD650's seem to have good reviews so i'll go for those.
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