Pink noise generator

[blackbeast250]

Hi , further my posts yesterday , would it be possible for someone to explain simply(or provide internet resourses) how the procedure of eqing a sound system using pink noise is carried out , and how I could carry it out on a small system, also stuff I could do first like the best places to put speakers , and simple acoustic treatment , that I could bring with me.

thanks , also if anyone has any more ideas on my post about effects set up it would be appreciated. Regards , Robin. :wacko:

[Simon Lewis]

Robin,

 

Further to the recommendations made yesterday, I did note where you were based and reckoned that the cost of a trip for a training course was probably less than the cost of a PAA3. I thought that a course would be better value for money!

 

So, to answer your request:

 

 

>>>procedure of eqing a sound system using pink noise

 

Don't bother, unless you are using Smaart or a similar FFT based system. Doing it with an RTA will probably make your system sound foul. 31 band RTAs do not have sufficient resolution, and as I mentioned yesterday, they are time blind.

 

Furthermore, it really does help to know what can be eq'd and what can't. There's no point in boosting the graphic to try and fill in a "hole" where cancellation is taking place. This is why I'd suggest having some training on sound system setup and alignment is so worthwhile.

 

However, you could try the practice of 'ringing out'. It isn't perfect, it only really corrects for one microphone, at that microphone's position, but it's a start.

 

Soundcraft suggest:

Set all graphic EQ controls to centre (0).

Turn up amp volume until feedback is just beginning to ‘ring’.

Turn back the amp volume slightly to prevent accidental feedback.

Starting from the left, adjust the first graphic EQ frequency gain control to ‘max’: if the system doesn’t feedback, then this is not a problem frequency. Return this gain control to centre position. If the system feeds back, reduce the EQ gain by the same amount you boosted to get feedback.

Repeat this procedure for all graphic EQ frequencies. Caution: Ringing out can cause howl around which can damage speakers, so use care when adjusting levels.

 

I tend to cut only a few dB - introducing very deep cuts tells me that my system is probably has not too flat a frequency response. In fact, a well designed system will probably not need much in the way of equalisation.

 

>>>best places to put speakers

 

Determine the horn coverage pattern, and make sure that the audience is within the nominal coverage angle. Get the boxes to a reasonable height and angle down towards the audience to help avoid rear wall reflections.

 

>>>simple acoustic treatment

 

Try drapes for absorption in reverberant spaces. It's unlikely that you will be able to achieve true acoustic treatment that is specific to the venue and portable.

 

 

 

Buy some good books: these may not be the very latest versions, but a quick look on Amazon should help

 

Basic Live Sound Paul White MPG Books 1-86074-271-8

Live Sound Mixing (2nd ed) Duncan Fry Roztralia Productions 0-646-11235-X

Making Live Music John Peel Making Music 1-872601-70-7

Sound and Recording - An Introduction Rumsey & McCormick Focal Press 0-240-51487-4

Sound Reinforcement Handbook (Yamaha) Davis & Jones Hal Leonard / Yamaha 0-88188-900-8

 

 

HTH,

 

Simon

[blackbeast250]

Thanks Simon, will certainly get the books , and try some of your suggestions, all the best , Robin.

[Solstace]

Seeing Simon's port reminds me - I used to use a relatively unusual system EQ method.

 

Step 1 - find a mic with a relatively flat frequency response. At one time, the closest I could find to a mic with flat response in our collection was an AKG CK47.

 

Step 2 - set mic up somewhere in the middle of the venue, pointing towards the stage and patch in to a spare mixer channel - leave gain and faders at lowest settings

 

Step 3 - Bring amp controls to 0dB (neither attenuation nor gain), bring main mixer outs to 0dB, EQ's to 0dB (including gain)

 

Step 4 - route mic to main mix, bring fader to 0dB. Bring up gain slowly until feedback creeps up. Then back off a little to stop it.

 

Step 5 onward - as per Simon Lewis' suggestions (starting with the lowest EQ).

 

This would usually give me a reasonable approximation of what was going on in the venue, especially if I "idiot checked" by moving the mic onto the stage and repeating the process (with the freshly dialled-in EQ settings).

 

HINT: If you must use the mic+graphic, a condensor mic typically has a flatter frequency response than a dynamic mic and might give more "meaningful" results.

[blackbeast250]

Thanks Solstace, I will also try this method, however it surprises me that in this age of information that there isnt something that you can just plug into your system and have it automatically analyse the room and automatically set your eq for you , or maby there is ?? anybody ? The smaart system that simon mentioned , having looked it up on the net is a software , does it do this and is it easy to use and how much does it cost? any more suggestions much appreciated.

Happy easter to everyone and enjoy the weekend.

Robin

[Simon Lewis]

Smaart lists at $695 and costs about as much in £. Not sure what the € price is.

In addition to the software, you need a reasonable PC, a calibrated [omnidirectional] measurement mic, a small mixer and / or a USB preamp.

That allows you to get squiggly lines on the screen. To interpret them and make sure you are not measuring rubbish needs an understanding of what you are measuring. [broken record mode] Smaart do put on training courses, but they charge for them! [/broken record mode].

 

However, you can download a 30 day demo of Smaart, but you cannot save data. Go to Siasoft.

 

There are some devices that "automatically EQ the room", and JBL made a loudspeaker system that did this. AFAIK, it's been withdrawn from sale. The auto EQ devices are usually best left alone. However, you can try them out and let us know what you think...

 

The problem is like this....

 

Sound systems consist of a number of radiating sound sources which interact with each other and the acoustic environment. Depending upon their phase and amplitude relationship, sound waves from different sources may remain unaffected, add or cancel. This interaction will vary with frequency, temperature, humidity, source and receiver placement. An individual 2 way loudspeaker enclosure may exhibit poor directivity at crossover frequencies because of poor electroacoustic behaviour. Even a well behaved loudspeaker that is aimed at the rear wall may give rise to poor perceived frequency response to the listener who hears both the direct and the delayed, reflected sound.

 

Some of these events are non-equalisable, i.e. if acoustic cancellation is taking place (e.g. two adjacent loudspeakers with opposite polarity), then no amount of boosting a graphic will correct the problem - in fact it will make it sound worst.

So, to run an algorithm that attempts to correct this mixture of problems is usually doomed to failure.

 

The experts will typically ensure that the loudspeaker system itself is aligned correctly (i.e. multiple loudspeakers behaving if they originate from one virtual acoustic point source), then will attempt to minimise any unwanted acoustic interaction with the listening space. A knowledge of room modes, critical distance and critical frequency, and loudspeaker directivity will help here.

 

Hopefully, you'll appreciate that this is a vast, complex subject. I've been studying it for a few years, yet still consider myself to be something of a neophyte...

 

Simon

[blackbeast250]

Hi simon , I appreciate what you are saying , and I dont expect 100%, I just want to learn how to eq my own system , surley if I bougt what is deemed to be the appropriate kit , an engineer could teach me how to use it , ie go through a procedure with me that I carry out each time I set up the system , I am investing in a significant system and I want it to work to its optimum or as close as possible , I dont want to become an engineer I just want to be able to eq my own system fairly well , and am willing to pay an engineer to teach me how to do this , surley this is possible , all the best , Robin

[Bobbsy]

A couple of economy/alternative suggestions for you:

 

First off, for your EQ, get a Behringer DEQ2496. Whatever you thing of Behringer in general, this particular item is hard to beat, even at several times the cost, and has found it's way into some pretty high end systems. The thing about this EQ is...it has a built in RTA. Couple it with the Behringer ECM8000 measurement mic (which is dirt cheap but adequate) and you have a winning system. Check http://www.behringer.com/DEQ2496/index.cfm?lang=ENG for the DEQ.

 

Alternatively, check out the Allen and Heath downloadable RTA on their site at http://www.allen-heath.com/UK/ViewProductd...rch=RTA&I2=Find . No, it's not SMAART or anything like it, but there's a 14 day free trial and even if you buy it, it's under a tenner!

 

Bob

[PoppaDom]

2nd Vote for the A&H software.

 

SMART it isn't but cheap and an effective tool to have in the box it certainly is.

 

Good to quickly see what is going on in a venue; particularly if you find problematic frequencies with harsh harmonic related problems.

 

 

Poppadom

[dbuckley]

...unless you are using Smaart or a similar FFT based system. Doing it with an RTA will probably make your system sound foul. 31 band RTAs do not have sufficient resolution, and as I mentioned yesterday, they are time blind.

Whereas I agree that we can do better than RTA these days, until a few years back the only tool usd to "adjust" the PAs overall EQ was the 31 band graphic, aided and abetted by RTA. Not every PA prior to Smaart sounded "foul", some sounded fabulous, and conversely, I'm sure most folk have heard a line array somewhere that sounds just plain ugly, and you can bet your bottom dollar that it will have been helped along by Smaart.

 

The RTA and 31 band GEQ are just tools, and its how you use them that determines how foul or otherwise the rig ends up sounding.

[soundo26]

Thanks Solstace, I will also try this method, however it surprises me that in this age of information that there isnt something that you can just plug into your system and have it automatically analyse the room and automatically set your eq for you , or maby there is ?? anybody ? The smaart system that simon mentioned , having looked it up on the net is a software , does it do this and is it easy to use and how much does it cost? any more suggestions much appreciated.

Happy easter to everyone and enjoy the weekend.

Robin

 

There are!!!!!

 

You can get feedback destroyers / inhibitors which can automatically reduce feedback, watch out though these can adversely affect your eq if overused on the full-range mix.

 

You can also get a spectrum analyser, when used with a pink noise generator and decent reference mic can give you a good idea of what's happening with your acoustics. I have a software one which I use on my laptop with an external mic, not studio quality but good enough for general guidance. this has bands corresponding to the bands on a graphic EQ, when you put out pink noise into the room, it is "heard" by the mic and this registers on the analyser display,you can then see the more "lively" frequencies and you can turn them down if required. Please note that these should really be used only as a guideline, whenever I've set up a room with these things to their "ideal" levels the sound is not good to the ear because it is too flat & doesn't start sounding sweet until you add some EQ!!. (but at least you'll know which frequencies to watch out for) :)

[Simon Lewis]

The RTA and 31 band GEQ are just tools, and its how you use them that determines how foul or otherwise the rig ends up sounding.

 

Very true, and I woudn't disagree with you. However, the overwhelming tendency seems to be for people with an RTA and pink noise generator to try and make the response curve look flat. Then it starts sounding rather poor! I still see literature advising users to boost significant sections of the audio spectrum, when it appears to be comb filtering or some crossover anomaly that needs fixing first.

 

The fact that we have better tools and a better understanding of what is happening in the electroacoustic realm gives the impetus to aim higher...

 

Simon

[Bobbsy]

Simon is spot on. Getting a flat response with an RTA can never be more than a starting point.

 

Strange as it might sound (and my background is engineering) meters and displays are no substitute for your ears.

 

Bob

[Pete McCrea]

....... and I dont expect 100%, I just want to learn how to eq my own system , surley if I bougt what is deemed to be the appropriate kit , an engineer could teach me how to use it , ie go through a procedure with me that I carry out each time I set up the system ,.......I dont want to become an engineer I just want to be able to eq my own system fairly well , and am willing to pay an engineer to teach me how to do this , surley this is possible , all the best , Robin

 

If you're investing a significant sum in a System, then get some training to learn how the speaker placement affects sound, how phase cancellation works etc etc etc. This way you'll be able to step into a room, and KNOW where will be best to place the speakers, know which seats might loose 3k1 because the frequency is cancelling, and where 3k1 will be boosted. When you know how a room will work with and against you, you can then start to optimise where and how you use the system. Get these basics right and be onto a winner.

 

If it were me? It'd get a good graphic, and not bother with a RTA type tool. I'd then spend the money I saved on good training from the likes of Meyer or D&B where they explain accoustic theory etc, which is applicable to all kit, and then tell you how good theirs is... It might also be worth going back to basics of things like A Level Physics and the wave theory it teaches etc to help understand how waves interact.

 

That's my 2p's worth.....

[blackbeast250]

Thanks for all the information folks , the graphic I had intended getting is the klark teknik dn370, , I also take on board what little dj says about some training , however I feel that getting this training from a very experienced sound engineer may be more fruitful ,practical and to the point, but unfortunatly physics and maths were my two worst subjects at school, if anyone can suggest a person who would be willing to teach me the stuff I need to know and a specific method /procedure ie smaart or something like it , preferably someone in the rep of ireland or ni, please let me know , im sure whatever they charge will be well worth it, thanks , Robin.