Trapping sub bass

[djui5]

I e-mailed Ethan about this, but he'd rather me put it here so the whole world can be helped :)


I need to handle sub bass in my mix room. I'm talking about 75hz and below. There's some sierous cancellations going on down there. Whats the best way to go about trapping that kinda bass? I checked out Ethans bass traps on his site, but they seem to deal with 80hz and above. I know it's my room because I stuck a sub in here and it did nothing practically. It was a 12" JBL sub.

Here's a thread with some info about what I've done so far...

http://gearslutz.com/board/showthread.php?t=45920


Thanks for your help. BTW, I'm on a shoestring budget....I'd hire an acoustican if I could.

[stevep]

the Hangers work great if you can spare the space.........


you have seen my studio build thread and know the ceiling, speaker soffitt and rear wall are full of these things.



They really work, there cheep to build and for lower Freqs the larger the better.




steve

[djui5]

Steve!

How did you hang those? Also, how do they effect the high end?

[thethrillfactor]

Originally Posted by djui5

I e-mailed Ethan about this, but he'd rather me put it here so the whole world can be helped :)


I need to handle sub bass in my mix room. I'm talking about 75hz and below. There's some sierous cancellations going on down there. Whats the best way to go about trapping that kinda bass? I checked out Ethans bass traps on his site, but they seem to deal with 80hz and above. I know it's my room because I stuck a sub in here and it did nothing practically. It was a 12" JBL sub.

Here's a thread with some info about what I've done so far...

http://gearslutz.com/board/showthread.php?t=45920


Thanks for your help. BTW, I'm on a shoestring budget....I'd hire an acoustican if I could.

First of all how do you know there is a Null that deep?


Have you shot the room to make sure?


If you can't hear it it may be due to other reasons.

[djui5]

I pull up a sine wave, and it's good at 80hz, dips at 75 (to almost nothing), up again at 70'ish, and is down a shitload from there (50hz is nearly non-existent)...I can't hear an 808 kick in here at all... I play songs with deep bass (El Bebe Masoquista from fatboy slim), and there's nothing. I can hear it if I stand at the front wall (the wall behind the speakers), but that's the only place really. I brought in a sub, and it did almost nothing in the mix pos.


I haven't shot the room yet, the RTA from next door is off being repaired.

[thethrillfactor]

Originally Posted by djui5

I can hear it...that's how I know. I pull up a sine wave, and it's good at 80hz, dips at 75 (to almost nothing), up again at 70'ish, and is down a shitload from there (50hz is nearly non-existent)...I can't hear an 808 kick in here at all... I play songs with deep bass (El Bebe Masoquista from fatboy slim), and there's nothing. I can hear it if I stand at the front wall (the wall behind the speakers), but that's the only place really. I brought in a sub, and it did almost nothing in the mix pos.

Then check the speakers.


These are the Adams correct?

[djui5]

Originally Posted by thethrillfactor

Then check the speakers.

I have S3A's. I can see them moving. It's not the speakers.

[thethrillfactor]

Originally Posted by djui5

I have S3A's. I can see them moving. It's not the speakers.

The JBL sub is powered correct?


That means the leads go through the sub up to the Adams right?

[Andreas G]

In my little room I'm using a combination of Helmholtz Resonators and Panel Absorbers... here are some formulas.
For the Helmholtz you have to find out the exact frequency modems to use them effective, the Panel Absorbers are working a bit broader but you still should analyse your roomsituation correctly. If you are handy in calculation and woodworking you might do it yourself. I did the calculations and planning by myself, though I had help from a woodworker, it saved alot of money at the end.
good luck... Andreas

[Anderson]

Can be a tough pb to solve...

I had to design "dual membrane resonators" to treat those efficiently. They go down as low as 39Hz, but they're huge and very hard to build on a DIY basis. Both // membranes need to be tuned precisely and quite regularly (kinda like a drumset) especially if temperature in the room varies a lot. I usually place this type of resonator behind a more conventionnal diffusor with a classical bass trap included and tuned at the next octave, it makes the dual even more effective. I only built 4 pairs so far, all custom, all work like a charm.

On the pic you can see the kind of diffusor+bass trap that is placed in front of the Dual membrane resonator - when a flat model is required that is (this one is 120/122/30cm). The dual mem reso that is to be placed behind is 120/122/80cm!
Corner models are a bit easier to build actually. Still HUGE though. The one on the pic was custom designed for a mastering studio, it's still "raw", needs finishing...

When I get to build another dual (soon, maybe in June actually) I will post some pics of the whole thing so you can see how it's done inside & how it works, it's kind of hard to describe!

Cheers!

[djui5]

Originally Posted by thethrillfactor

The JBL sub is powered correct?


That means the leads go through the sub up to the Adams right?

I only hooked up the sub for 5 min's to see if it would help. Yes, when it was hooked up the Adams got their signal from the sub, but normally it goes from the DA-10 to the Adams

Normally it's just the Adams. With the sub, there was little difference.

The bass traps I built in the back of the room (big black thingees) helped a little, but it's still not right.

Thanks andreas. I'll check those out.

[thethrillfactor]

Originally Posted by djui5

I only hooked up the sub for 5 min's to see if it would help. Yes, when it was hooked up the Adams got their signal from the sub, but normally it goes from the DA-10 to the Adams

Normally it's just the Adams. With the sub, there was little difference.

The bass traps I built in the back of the room (big black thingees) helped a little, but it's still not right.

Thanks andreas. I'll check those out.

Try it without the Adams.


If you hear anything through the sub (provided there is any low freqs in the music) than you know its not the room.



Also do you hear any bass Freq's in the back corners?

[djui5]

Originally Posted by thethrillfactor

Try it without the Adams.


If you hear anything through the sub (provided there is any low freqs in the music) than you know its not the room.



Also do you hear any bass Freq's in the back corners?

I have some boxes in one corner (the corner where the window is), and there's a little bass there, but not much. The other corner there's no bass. When I lay on the floor behind the big black traps I can hear some low end, but it's not right..sounds funny. Also, up in the ceiling area there seems to be a little of it too.

I spoke with sb about this, and he gave me some really good ideas, but I wanted to see what kinda feedback I could get here also.

I've tried moving the adams back and forth from the wall behind them, but it didn't really change much at all. Only thing I haven't done is turn my whole mix area sideways. I'd rather not do that if I can help it.

The frustrating thing is that it dosen't seem to be a freq or 2...it's an entire drop off below 70hz, and a dip at 75.

[thethrillfactor]

Originally Posted by djui5

The frustrating thing is that it dosen't seem to be a freq or 2...it's an entire drop off below 70hz, and a dip at 75.

This is my point.


A room the size you got should be no problem when it comes to producing bass.



I would think you need a bigger sub actually to move the room.


An entire drop off makes me think of:


1) A HP filter switch that's been engaged by mistake on the ADAMS or DA-10


2) The Woofers are blown or there is a loose wire to the woofers inside and all you are hearing is the mid driver and tweeter.

[djui5]

I would be incined to think that also, but I can see the speaker moving..so I know it's working..I'm just not hearing it. Plus, I can hear the bass at the front wall...so they're producing the low end.

I played a beat lindell made...it's hillarious..speaker cones flying, but no bass....

[superburtm]

Originally Posted by djui5

I played a beat lindell made...it's hillarious..speaker cones flying, but no bass....

It could be freq's that are 80 and above causing your cones to dance.... And the spks aren't producing anything below that..for whatever reason as thrill suggests. hmm...

[thethrillfactor]

Originally Posted by djui5

I played a beat lindell made...it's hillarious..speaker cones flying, but no bass....

Means nada.


Are woofers moving in or out?


Could they be out of phase?


I would definitely suggest to try a different speaker and use an external player besides the DA-10.


Eliminate all variables and make it simple.

[djui5]

I'll burn a disk and take them next door. I know the mix room next door sounds good....

There's no hi-pass filters anywhere in the chain, none that I can switch on or off anyway.

When I play a sine wave at 50hz, I can see them moving, but they're not near as loud as they should be...same goes for 60 and 70hz.

It seems the dip at 75hz is gone now (I just ran a sine wave to see if the speakers moved at 60hz), since building the black things. Now it's just an overall dip below 80hz. I have no way of testing with a meter to see how much it dips, or what....

[stevep]

can you borrow some other speakers ? even some basic "home stereo" speakers to try.

You can see how i built the Hangers on the studio build thread.
start on page 5 in the middle of the page

Steve's new Recording Studio from the start



You can cover them with reflective material if you want to retain the highs. I covered them with 3"703 and cloth and it works great.

these hangers would fit perfect in your ceiling and if you trap the corners with 4" of 703 and built a 24" deep trap on your back wall filled with the hangers that would make a Huge difference.

Hangers do tend to work better at High SPLs,

they are super quick and easy to build

You can hang them with rope , chain, heavy wire or plumbers tape.



steve

[u b k]

take an hour or two, get some long xlr's, and just move those damn adams all around that room with a good ref recording playing, and have no regard for practical concerns such as 'mix position' or 'basic human esthetics'. just move them everywhere.

as you're doing this, move yourself around and listen to everything. make them really wide and sit twice as far back as you normally do. set them up catty-corner, set them up near the middle... go nuts, and listen to what's going on.

somewhere, somehow, you should find lots of places where the bass is deep, if uncontrolled. if you don't, the problem is not your room. i'm with thrill, a total dropoff sounds like something else is going on. even the tiniest rooms with the most horrendous nodes and nulls still have lots of audible energy sub-60, it's just untamed.

keep us posted. and the fact that a cone moves doesn't mean you'll hear it; just ask anyone who owns ns10's .


gregoire
del ubik

[DirkB]

Yeah, the fact that you don't hear serious bass built up in most of the corners is strange. Looking at your room, it's nicely spacious, but still small enough and with limited treatment, so there should be serious modal behaviour, resulting in bass build-p in the corners.

Interesting...

Good luck,
Dirk

[Anderson]

When you send test tones, try to send some with a second harmonic playing at the same time, it will help you detect if it's the room or a technical pb. It's hard to hear below 60Hz if there are no harmonic content at all (i.e. F-M curve, and the brain cannot "phase lock" at all below 80Hz). Usually the sub produces mechanical resonances that help in that matter, but the better the sub, the less mechanical interaction...

That is all very strange...

[Prahlad]

This might be a bit late now, sorry to do this to you, but i read a very interesting theory in a book by M. P. Stavrou (Mixing with your mind.com) Great book btw!! He suggests starting with an empty room an assistant and moving about the room at a fixed distcance (2-3 meters) . Dont worry this neednt neccesarily be your Adams, mobility is more important than quality. You should be able to hear significant differences in how the room interacts with the speaker and it should be possible to find a few locations where the soundstage created in your room feels and sounds better than other spots. Once youve found two in a suitable mix triangle you can continue setting up you gear as ussual. It might not look right but it should sound right or at least better...Will try this myself when i get home as im in Australia right now. Just thinking as you have sub bass issue you might need to do this with a larger speaker after all and i would think removing the accoustic treatment will let you hear more of the room until you decide on a spot...Hope its not to inconvenient, but i reckon its an option before ending up with 4 tonnes of MDF outside your front door......good luck with it, room is looking good,

[Ethan Winer]

> I e-mailed Ethan about this, but he'd rather me put it here so the whole world can be helped :) <

Right, when someone wants personalized service and consulting, I need to charge for that.

> Whats the best way to go about trapping that kinda bass? <

Big bass traps, and plenty of them.

Seriously, there's no cheap, easy, or small solution for treating really low frequencies. Once all of the corners are treated with rigid fiberglass bass traps, the next step is panel traps flat on the walls. The low-bass traps in my PLANS article are centered around 100 Hz, but you can alter them to go as low as needed. I also agree with the others that you should measure your room before going to the considerable effort to build custom traps. And that measuring should include modal ringing (waterfall plots), not just a simple RTA frequency response. Then you'll know much better which frequencies are the biggest problem.

--Ethan

[mtstudi@pacbell]

Must be a phase issue. That would be the first thing I would check.

www.bluethumbproductions.com

[Glenn Kuras]

Originally Posted by Ethan Winer

> I e-mailed Ethan about this, but he'd rather me put it here so the whole world can be helped :) <

Right, when someone wants personalized service and consulting, I need to charge for that.

> Whats the best way to go about trapping that kinda bass? <

Big bass traps, and plenty of them.

Seriously, there's no cheap, easy, or small solution for treating really low frequencies. Once all of the corners are treated with rigid fiberglass bass traps, the next step is panel traps flat on the walls. The low-bass traps in my PLANS article are centered around 100 Hz, but you can alter them to go as low as needed. I also agree with the others that you should measure your room before going to the considerable effort to build custom traps. And that measuring should include modal ringing (waterfall plots), not just a simple RTA frequency response. Then you'll know much better which frequencies are the biggest problem.

--Ethan

Totally agree with Ethan on this. Get yourself ETF software and test the room. It will slap you pretty quick what the problems are.

Glenn

[nosebleedaudio]

Modulate the frequency, a contant frequency is not a good indicator, also use one speaker and see if that changes anything.
Some times speaker position can also make a huge difference.
Make sure no 2 dimensions are the same, at least 1 foot between each one is a good starting point. IM referring to the speaker to floor, speaker to rear wall, speaker to side wall...

[djui5]

interesting.

I have no way to measure the room, and don't have a PC to run the software right now either (no laptop). They have an RTA next door, but like I said earlier it's off for repair.

Ethan,
How do you go about tuning your deep bass traps? By increasing the spacing between the insulation and the wall?

What if there was no back to it? If it was only a front panel, insulation, and no back? How would that effect the response?

I'll report back after I take my speakers next door to make sure they are working properly...would be a shame if something was wrong with them, but again, would be a great thing because it would save me $$ on building supplies

[jayfrigo]

In addition to other types, I've had good luck with perforated panel traps when tuned trapping is appropriate. However, measurements would indeed be necessary to know exactly where to tune it. However, an 8 inch cavity behind the panel filled with 4 inches of insulation will broaden the Q enough so that you can estimate a center frequency and have a decent margin of error. Everests Master Handbook of Acoustics has the info you'd need to figure hole size, spacing, and panel thickness, or you could use the Helmholtz equation and extrapolate out to make each effective "cell" behind each hole the appropriate volume. Of you could search for Mankovsky's writings. He did a boatload of work on the subject. It's an easy way to get deep bass absorption with only an 8 inch depth.

[camitchell]

.

I've been taking another look at the bass trap/difussor units you built and I just hate to bring it up..... but I'm not convinced they are working the way you might think they would.

If they are based on Ethan's plans, there are some sizable acoustical design deviations that I'm pretty sure would change the performance. It's hard to tell from a few pics though.

However, since your room is 27+ feet deep (if I remember correctly) that should be pretty favorable for at least some amount of bass response.

It will be interesting to find out if there are any issues with the monitoring signal chain.

Regardless, speaking from experience.... you'll hear much more difference once you start treating the back wall corners and ceiling as well.

Hang in there and good luck! I'm sure you'll get it sorted. What a nice size room to start with.

.