Acoustics in a Large Club

[nixoblivion]

Im going to ask this already kinda knowing the answer, or where its going to lead!

How do you get good acoustics in a large club (200 guests)?
I work at a club once in a while that has quit bad acoustics. Ive told the owner a few times already that investing in acoustics would really help this place, but he and i know that under a few thousand there isnt much you can do and that money just isnt laying around!

Looking at the first picture i added you can see how the room looked without anything done. The yellow slope is after some adjustments.
First i changed the Subs xover from 100 to 80hz. I then made a few cuts and boosts on the EQ in the master insert!
And this is also the problem... I know its not good to EQ the signal to get the desired sound, but what other way is there in this case?

Looking at the next graph (2) shows the state at which the room is right now with all the adjustments (sub + graphic eq). This was measured in the middle of the room.
Graph 3 shows the measurement a few meters back, close to the back of the room. 4 Shows the FOH spot when standing and 5 shows the FOH spot while sitting.
The differences are huge... the bass region is just completly different.

I tried eqing a little to get a rather flat response for the middle of room, knowing this will make other places worse. But my guess is that most of the crowd will be forming in the middle... But this is the reason why the 66Hz mode is so strong in the back of the room (i boosted that by a few dB for the middle).

My other question would be, what about the high end drop? It looks really quite bad, but it sounds fine i guess. The EQ that i added in during the measurements had a high shelve (if you can say that for a graphic eq) at about 8khz -3db. Without this shelve its juft very bright and hurts a little after while (especially at higher volumes)

[nixoblivion]

Not gonna make a big difference (since the problems are too many and clear anyways), but i know people here love these :D

1. middle
2. back
3. foh

[tINY]

It's gonna change when the room fills up with people too....

Large rooms is one place that 1/6 octave noise makes sense as a way to measure. You may look into gated measurements as well.

For practical help - look at the dispersion (coverage angle) of the horns and try to keep the sound off of reflective surfaces. Also, a parametric equalizer is a powerful tool if you know how to use it (and walk the room a bit when the show is starting).




-tINY

[Dange]

Originally Posted by tINY

It's gonna change when the room fills up with people too....

A way round this is to design for minimal changes in amount of absorption between the venue being empty and full.

In a concert hall you install chairs that change minimally in absorption coefficient between being occupied or being empty, i.e. the person sitting in them changes the absorption performance a little as possible.
So the probable solution is more absorption, but at which frequency is the critical bit.

What's the current Reverberation Time in the venue across frequency bands? RT is applicable as we're now in large room acoustics, not small.

[nixoblivion]

Originally Posted by tINY

It's gonna change when the room fills up with people too....

Yes thats the problem though. For sound check you'll have a totally different sound.
Also we never know how many people will come. There have been concerts with 5-10 people and some with over 200 (not alowed in anymore).

Originally Posted by tINY

Large rooms is one place that 1/6 octave noise makes sense as a way to measure. You may look into gated measurements as well.

The first graph i posted is 1/3 Octave.
Can you please explain a bit more what you mean with gated measurements and how to do them?
Im guessing you mean changing the window in the IR? But to what?

Originally Posted by tINY

For practical help - look at the dispersion (coverage angle) of the horns and try to keep the sound off of reflective surfaces. Also, a parametric equalizer is a powerful tool if you know how to use it (and walk the room a bit when the show is starting).

Ive angeled the Pa down and into the room. Its very hard to get it exactly right since the owner chose to hang the PA on 3 metal wires... changing those lengths and especially moving the pa inwards is quite hard!

Originally Posted by Dange

What's the current Reverberation Time in the venue across frequency bands? RT is applicable as we're now in large room acoustics, not small.

I never know if I should trust the reverberation tool in Fuzzmeasure 2. But here it seems to look quite right (i guess its the big room! ;D)

[tINY]

Speaker Testing FuzzMeasure Analysis Info - VPA Wiki


Look at the impulse response section. You want to gate out the reverberation to get a good feel of the direct vs indirect spectrums. That will tell you where you need concentrate your treatments.

Looking at your gross reverb graph, I'd say you have a problem with bass. This is probably because the mid and high frequency are controlled dispersion and the subs are radiating everywhere.

This probably means you need thick absorbtion wherever the horns don't point. 2 feet of fluffy pink at the ceiling behind a suspended (t-bar) ceiling would be a possible option...



-tINY

[Ethan Winer]

Originally Posted by nixoblivion

I tried eqing a little to get a rather flat response for the middle of room, knowing this will make other places worse.

Is the problem frequency response or simply too much ambience? Usually large spaces need absorption rather than EQ, unless the speakers are also deficient in which case EQ could help. Looking at the RT60 graph you posted, which is the most relevant graph, it appears you need substantial absorption that is thick enough to work well down to bass frequencies.

--Ethan

________________
The Acoustic Treatment Experts

[avare]

Originally Posted by Ethan Winer

Is the problem frequency response or simply too much ambience? Usually large spaces need absorption rather than EQ, unless the speakers are also deficient in which case EQ could help. Looking at the RT60 graph you posted, which is the most relevant graph, it appears you need substantial absorption that is thick enough to work well down to bass frequencies.

+1. Adding to the above, clubs tend to have chairs, tables, etc which make detailed response curve analysis meaningless. Like Ethan wrote, low end absorption is about the best we can say without even having dimensions!

If you want to read about state of the art analysis of concert hall* acoustics for modern music, see the attached article.

Andre

* I had orignially incorrectly writtent hat the docuemtn was about club acosutics, which is wrong. Thanks Andre, the Portugese one, for catching that in post 10 in the thread.

[andrebrito]

Forget frequency response and waterfall charts in clubs, that is nonsense unless you are calibrating your PA system.. but for room acoustics measurements make RT 60 measurements third octave over the spectrum (63 or 125 to 8000 is enough) and use LONG excitation signals

Also bass control in a club is insane ! It is EXACTLY the opposite !! You DON'T reduce bass in a club, you take advantage of it. So for instance, speakers can actually go in corners to take advantage of more bass power... something you would NEVER do in a control room.

What more... you usually want the acoustical ceiling to be absorbent and part of the walls but you actually can go for perforated or slotted panels instead of typical broadband since people take a lof of absorption already.

I cannot say more unless I go in "consultancy mode" haha !

[andrebrito]

Andre, that article is related to concert halls , not for nightclubs ! :-)

[DanDan]

There is quite a difference between live and recorded music in terms of the behaviour of the sound system. With live music there are microphones which lead to assisted resonance. Some of this is room related, some is more to do with the backwash from the speakers and the acoustics of the stage and so on. So I would try those tests again with open mics from a an actual concert. Include the foldback.
You might get away with a few quick sweeps during the break in a concert.

The HF roll is quite normal in my experience.
Flat can be very hurtful.

DD

[SAC]

Use SysTune (look it up!)

and control by wire systems such as HiQNet or Cobranet

And CONTROL THE STAGE VOLUME!!!!!!


...but why do I get the feeling that we are going to get to listen to many tell us how to 'ring out' the system instead...

[avare]

Originally Posted by andrebrito

Andre, that article is related to concert halls , not for nightclubs ! :-)

Thanks Andre. I have edited the post, with attribution to you for catching the error.

The Canadian one,
Andre

[nixoblivion]

Thanks guys for all the great info,
Now i finally know what the reverberation tool is for!

The problem, as i have stated in my first post, is that i have little to no say in whats to be changed. It takes me ages to convice the owner to get little things like cheap monitors or compressors (we've got tons of behringer stuff lying around that i barely use!) Only when things break there is money to get new things! thats the way things work around here. Maybe in a few years things will change...
I doubt you can get good acoustic treatment (even self made) for under 1000€ in a club that size! Plus you always have the problem that it has to be tested and all (statics).
So my question is, is there any other way to improve the acoustics in this club? cheap tipps and tricks?

Its hard to say the dimensions since there is lots of change in the room size and all, but in general its 15.5m (L) x 6.55/5.63 m (W alcoves) x 3.65 (H, but slightly concave)

[PaulP]

Originally Posted by nixoblivion

I doubt you can get good acoustic treatment (even self made) for under 1000€ in a club that size! Plus you always have the problem that it has to be tested and all (statics). So my question is, is there any other way to improve the acoustics in this club? cheap tipps and tricks?

I fail to see how you could improve the acoustics without acoustic treatment. That's what treatment does, by definition.

[nixoblivion]

Yes it sounds paradox, but its things like PA positioning, sub placement and the sorts.

Also the question that is still open. How best to EQ (graphic) the bass region? Its very different throughout the room. Should i just leave it flat to not make things worse in some spots or should i choose say the middle of the room and try to get the best response?
What are your ideas?

[DanDan]

nix I can only repeat that everything will change with open mics.
Crank up the gain and you will quickly find which sliders on the graphic need to come down. Parametrics are even better.

If you have a Mac, try Labmeter by RustyKat, to identify the booming frequencies exactly.

You may be able to do something about the 66 or other anomalies by position changes. Play a sine at the problem frequency and walk about. Find the peaks and nulls. If you can put the subs in nulls it should help.
DD

[nixoblivion]

Hey Dan,
I reread your post. Yes what you say does make sense. But still i think that the main problem Frequencies will stay the same mainly because most mics on stage are dynamic and mostly capture the source! They have little bleed in most cases!
Also that would mean i would have to do this with every concert?? Mic Placement is never the same... it might be similar at times, but not always!

For instance i know for sure we have a big problem with the note G. It makes the whole room shake. That should be the 100Hz (or 50Hz, but thats less of a problem). Should i just take that off in the EQ?? But then in parts of the room it will sound very empty, right?

Also it is impossible to do a sweep during the concert. everyone will be deaf. I dont quite know how you would make that work!

[DanDan]

nix, unless you are using severe High Pass Filters on everything, bass resonance will find it's way into open mics. Remember Subs and Woofers are essentially omni. Furthermore at 66Hz the mics are omni too. I suggest you leave the mics out until the day after a gig, then crank the gain and observe the feedback booms.
Maybe during the break in a concert you could do a train of say 4 sweeps and sync average them. You might get a useable S/N. You also might get sued, so a long shot....
Labmeter is my favoured tool for this type of work. It gives exact frequencies, perfect for digital parametrics. I cannot bring myself to say Behringer Ultracurve.....
DD

[avare]

Originally Posted by DanDan

nix, unless you are using severe High Pass Filters on everything, bass resonance will find it's way into open mics. Remember Subs and Woofers are essentially omni. Furthermore at 66Hz the mics are omni too. I suggest you leave the mics out until the day after a gig, then crank the gain and observe the feedback booms.
Maybe during the break in a concert you could do a train of say 4 sweeps and sync average them. You might get a useable S/N. You also might get sued, so a long shot....
Labmeter is my favoured tool for this type of work. It gives exact frequencies, perfect for digital parametrics. I cannot bring myself to say XXXXXXXXXXX XXXXX XXXXX.....

+1

Andre

[andrebrito]

And being this a club you need anti-fire rating material, you should not and cannot place any type of material in that place

Anyway don't know where you are located but you can might get some melanime M1 foam and hung some panels in the ceiling of the disco if you need to attenuate the reverberation

[nixoblivion]

Yes Dan of course you are right. Im quite tired today and making lots of stupid errors. There will be low frequency bleed. The desk has no low cuts (woooot) so i use the low shelf a lot to take off the low end, but i guess there is still lots of bleeding.
So what you are saying is that i should have a standard set up on stage, crank everything (monitors as well) and then measure which frequencies peak?
Its going to be hard to do with no drums or such on stage, but i can try.
Should i not care about how it sounds like...only which frequencies feedback?

I still dont understand what you mean with the sweeps during a concert. i have no idea how i could get away with that. Just imagine there are 3-4 feedbacks during a show, how the audience already starts getting pissed! :D

Btw. I have a DBX graphic EQ (digital since it has some feedback destroyer stuff on it), so no worries about the behringer in the master!



andre, im not talking about a disco. Im working at a club with live music... In anyway, ive installed about 25 panels of acoustic foam. Its better than nothing and its saved me for sound checks where the highs were just killing!

[DanDan]

nix, can the sweeps thing, I was raving. Yes standard setup on stage, crank the front. This can be done with a condenser centre stage if you don't need the hassle of a real set up. The feedback usually starts at LF. Find two or three of these, you're done. Watch out for L R differences if the PA is stereo.
To go a bit further.
Speak, grunt, hum, into a 58 stage centre. Go through the vocal pitches. There will be strong honks worth hitting on the graphic. Something in the range. 400-800 typically.

DD

[tINY]

It looks like low frequency reverberation - or, more likely, strong modal ringing - is the issue here. This room isn't that big and by looking at the RT graph, I'd say that the walls are stone or concrete, not drywall.

Concave walls are not good either. There's only so much you can do if the owner doesn't value good sound enough to get some basic acoustic materials in there...

I have read of a method using 4 subs on front wall, 4 on the back wall and a delay to control these issues, but that'll probably cost more than a reasonable ceiling treatment.




-tINY

[nixoblivion]

Originally Posted by DanDan

nix, can the sweeps thing, I was raving. Yes standard setup on stage, crank the front. This can be done with a condenser centre stage if you don't need the hassle of a real set up. The feedback usually starts at LF. Find two or three of these, you're done. Watch out for L R differences if the PA is stereo.
To go a bit further.
Speak, grunt, hum, into a 58 stage centre. Go through the vocal pitches. There will be strong honks worth hitting on the graphic. Something in the range. 400-800 typically.

DD

Thanks Dan! I will try that! I always have a problem with how to proceed with graphic eqs... :D
But you are suggesting that i should only EQ out the feedbacking frequencies, right? The rest of the EQ should stay mostly flat?

Originally Posted by tINY

It looks like low frequency reverberation - or, more likely, strong modal ringing - is the issue here. This room isn't that big and by looking at the RT graph, I'd say that the walls are stone or concrete, not drywall.

Concave walls are not good either. There's only so much you can do if the owner doesn't value good sound enough to get some basic acoustic materials in there...

I have read of a method using 4 subs on front wall, 4 on the back wall and a delay to control these issues, but that'll probably cost more than a reasonable ceiling treatment.
-tINY

Yea im a little surprised by the measurments i posted. I could swear that the room is a lot bigger, at least thats how it feels. Maybe my measuring laser went crazy? But anywho, yes the walls are very thick, im guessing stone or so.
And i know the Concave isnt too good either. Im also guessing the alcoves on the one side of the room, that are aprox. 1m deep arent very good either.

The question is, how much would it cost to get an acoustical ceiling? Especially as andre suggested it would have to be fire proof and all. Not sure i can do that diy, or want to be liable for it!
Also, would a ceiling, being only a few cm thick, help that much at low frequencies?

[DanDan]

But you are suggesting that i should only EQ out the feedbacking frequencies, right? The rest of the EQ should stay mostly flat?

Yes, I cut only.

DD

[tINY]

Originally Posted by nixoblivion

The question is, how much would it cost to get an acoustical ceiling? Especially as andre suggested it would have to be fire proof and all. Not sure i can do that diy, or want to be liable for it!
Also, would a ceiling, being only a few cm thick, help that much at low frequencies?

Check with local contractors. What you are after is a suspended ceiling / plenum like office spaces get. Dropped about 50-75cm with 25cm of insulation above it would help a lot.

This also gives you room to run signal wires and electrical for lights (power usually requires conduit, but it's hidden now...).




-tINY