sounding good

[Flash@TMB]

Teething problems

Well for the last 10 days I've averaged 4 hours sleep per night... OUCH!

On the Friday we had some issues with the sound, although nobody appears to have noticed. These digital desks operate a little differently and the line level was coming in at -18dB, that's way too low. On Saturday afternoon we removed the AD card and found some dip switches that set the input reference to +4dBV (that's pro level). Fuck knows what the other setting is for? Anyhow the signal then came in hovering around 0dB with is more like it, but with a danger of clipping, so we used the attenuators (a feature of digital desks) to bring this under control. Those of you who were there on Saturday night will have noticed that it sounded totally fuckin AWESOME!

On top of this the jukebox cratered on opening night, and has been unuseable since Thursday. We only had 4 comp albums cos we prefer real albums, and people were getting sick of hearing them repeated. I went to 1UP today and bought some new comps, but the all feature a decent quantity of fairly obscure stuff mixed with reasonably well know tracks so we can reuse them in the jukebox later on.

One of our bottle coolers also failed due to building work stew.

We were all pretty knackered by Sunday so I had to ask my sister to look after the bar, although I was there in body.

The jukebox should be fixed by Wed/Thurs - thank fuck!

Am going to post some photos in the gallery now.

[soundian]

Re: Teething problems

Originally posted by Flash@TMB:

Well for the last 10 days I've averaged 4 hours sleep per night... OUCH!

On the Friday we had some issues with the sound, although nobody appears to have noticed. These digital desks operate a little differently and the line level was coming in at -18dB, that's way too low. On Saturday afternoon we removed the AD card and found some dip switches that set the input reference to +4dBV (that's pro level). Fuck knows what the other setting is for? Anyhow the signal then came in hovering around 0dB with is more like it, but with a danger of clipping, so we used the attenuators (a feature of digital desks) to bring this under control. Those of you who were there on Saturday night will have noticed that it sounded totally fuckin AWESOME!

If you're in danger of clipping at 0dB then it must be measured in dBFS, not dBv/dBu. What you've done on the A/D card is tell it to expect a mic level signal, and then put a line level signal in. That's why you've had to attenuate it. If it's a global A/D setting that's the only way round it though. The other setting would be used if you had mostly line level signals to work with(samplers,keys,mixers etc).

Good job you noticed that before you tried to do a band. You're gain structure would've been, to use a technical term, fucked.

(Analogue desks have input attenuators too. They're normally called pads.)

[Flash@TMB]

So which is the best solution/

So which is the best solution?

A) Set the card to 24dB and have line signals coming in at -18dB? We can then use the attenuator to boost it, although the boost range is farily limited when compared with the attenuation range. I can't remember off-hand if the max boost is 3dBUs or 12dBUs.

OR

B) Set the card to 4dBV and have the signal coming is close to 0dB then attenuating it?

Please note that the raw signal does acutally clip on option B) but the attenuator brings it under control and it definately sounds better. There is no evidence of cliping on the output once the signal has been attenuated. We're currently attenuating it by 8dBUs.

I think the dip switches on the AD card are probably pads since the difference between settings is 20dBU.

Flash

[soundian]

Re: So which is the best solution/

Originally posted by Flash@TMB:

So which is the best solution?

A) Set the card to 24dB and have line signals coming in at -18dB? We can then use the attenuator to boost it, although the boost range is farily limited when compared with the attenuation range. I can't remember off-hand if the max boost is 3dBUs or 12dBUs.

OR

B) Set the card to 4dBV and have the signal coming is close to 0dB then attenuating it?

Please note that the raw signal does acutally clip on option B) but the attenuator brings it under control and it definately sounds better. There is no evidence of cliping on the output once the signal has been attenuated. We're currently attenuating it by 8dBUs.

I think the dip switches on the AD card are probably pads since the difference between settings is 20dBU.

Flash

A think you mean dBFS. This is different. 0dBFS is your max. Normally about -12dBFS is best. It gives you a good bit of headroom before digital clip but a good signal to noise ratio. I think it's about equivalent to 0dBu. If your coming in at -18 that's a little low but maybe your using unbalanced cables, that would give you a signal 6 dB less than optimum.

Leave the A/D card on +4 if it's global. You can pad line level signals with DI boxes if the desk doesn't give you enough attenuation.

[Flash@TMB]

Re: Re: So which is the best solution/

Originally posted by soundian:

A think you mean dBFS. This is different. 0dBFS is your max. Normally about -12dBFS is best. It gives you a good bit of headroom before digital clip but a good signal to noise ratio. I think it's about equivalent to 0dBu. If your coming in at -18 that's a little low but maybe your using unbalanced cables, that would give you a signal 6 dB less than optimum.

Leave the A/D card on +4 if it's global. You can pad line level signals with DI boxes if the desk doesn't give you enough attenuation.

Yes the CD player for example comes in on unbalanced leads. These are very high quality braided guitar leads that are 6m long.

So are you saying that it's OK if the raw signal is clipping, and just to bring it down using the attenuator? The attenuator can take it down by as much as -60, so there is plenty of flexibility there.

[soundian]

Re: Re: Re: So which is the best solution/

Originally posted by Flash@TMB:

Yes the CD player for example comes in on unbalanced leads. These are very high quality braided guitar leads that are 6m long.

So are you saying that it's OK if the raw signal is clipping, and just to bring it down using the attenuator? The attenuator can take it down by as much as -60, so there is plenty of flexibility there.

That explains the signal level then. Unbalanced cables only carry one signal, not two like balanced cables. If you put it through a DI box the signal should increase by about 6dB. It's not necessary though, just if your interested.

I would start with all the channels attenuated a bit, when it comes to line checking bands, your inputs might get quite a battering until you bring in some attenuation. Basically it's better to start low and bring it up.

[Flash@TMB]

OK I think we have this sorted. The whole desk seems to be referenced in DBFS. The green LEDS turn to yellow at -12 (something that happened at 0 on the old desk), the yellows turn to red at 0. Monitoring it more closely at peak the CD signal just enters the yellow section - I should mention that I put the dip switches on the AD card back to their original setting. Turning the system up full (not for the fainthearted) the 3db to clip light on both the desk at amps starts to flicker. We also adjusted the amps slightly.

Mics appear to work the same way. Hot Mangu stopped by after their practice and spent 6 hours helping us test things out. This was mostly 6 hours of "ONE TWO" pause twiddle "ONE TWO". Those guys have the patience of saints. The gain on the vocal mics with the input signal turned up to 0 was the giveaway. After err 5 hours and 50 minutes of fruitless EQing in a minefield of feedback we turned it down so that it just peaked in the yellow and everything started working.

What blew me away was that 30 people had showed up, and despite me suggesting that really they'd be better off drinking elsewhere they stayed till the end. It must have been torture. No let me rephrase that... IT WAS FUCKIN TORTURE.

Many thanks to Hot Mangu, we couldn't have done it without you.

Flash

[soundian]

Originally posted by Flash@TMB:

OK I think we have this sorted. The whole desk seems to be referenced in DBFS. The green LEDS turn to yellow at -12 (something that happened at 0 on the old desk), the yellows turn to red at 0. Monitoring it more closely at peak the CD signal just enters the yellow section - I should mention that I put the dip switches on the AD card back to their original setting. Turning the system up full (not for the fainthearted) the 3db to clip light on both the desk at amps starts to flicker. We also adjusted the amps slightly.

Mics appear to work the same way. Hot Mangu stopped by after their practice and spent 6 hours helping us test things out. This was mostly 6 hours of "ONE TWO" pause twiddle "ONE TWO". Those guys have the patience of saints. The gain on the vocal mics with the input signal turned up to 0 was the giveaway. After err 5 hours and 50 minutes of fruitless EQing in a minefield of feedback we turned it down so that it just peaked in the yellow and everything started working.

Woohoo, I was right.

All you've got to do now is get used to using -12 as your optimum level instead of 0, you normally get about 10-12 dB headroom on analog desks so it's not that different.

You really,really don't want to clip anything digi. Make sure things like vocals, especially when there's a shouter in the band, have enough compression/limiting on them and it should be plain sailing.(high threshhold, high ratio compression if you don't want to use a limiter)

And you spent nearly 6 hours getting your gain structure right. Tsk.

[Flash@TMB]

Originally posted by soundian:

Woohoo, I was right.

All you've got to do now is get used to using -12 as your optimum level instead of 0, you normally get about 10-12 dB headroom on analog desks so it's not that different.

You really,really don't want to clip anything digi. Make sure things like vocals, especially when there's a shouter in the band, have enough compression/limiting on them and it should be plain sailing.(high threshhold, high ratio compression if you don't want to use a limiter)

And you spent nearly 6 hours getting your gain structure right. Tsk.

OK - update time...

The position has changed. I put the AD card back to pro level +4dB, here's why. When set to the default of +24dB the peak input gain was, as discussed between -12dB and -18dB unattenuated depending on the CD player. With the channel faders set to 0dB and the sterio bus also cranked up to 0dB this produced an output of an identical level to the input gain ie. between -12dB and -18dB. What surprises me is that this originally surprised me... of course it would DOH!

Set to +4dB the peak input gain appears to clip, but no clipping effects were audible at any volume. On investigation attenuating the signal by 0.1dB caused a 3dB reduction on the meter. In other words anything hitting EXACTLY 0dB triggers the clip light. Modern CDs being so fuckin stupidly over compressed are hovering at EXACTLY 0dB for most of the time. They aren't actually clipping, it's just that the desk triggers the clip light on 0dB not 0.1dB. Now turing all faders right up results in 0dB on the stereo bus meter ALTHOUGH BY THAT POINT IT'S HARD TO CONCENTRATE ON THE METER FOR OBVIOUS REASONS... !!!

The point is that this is all consistent with the theory - phew!

So what I do now is just turn the channel faders up to 0dB then ride the stereo bus - this gives the best results sonically.

The mic gains are as Soundian suggested, only now I follow what he was driving at. The big problem I had was not realising how powerful the system was, and basing my understanding on the CD player operating at a -12dB peak input gain. The bottom line here is that I can turn the gain on the vocal mics up much higher than I prviously realised, producing a much better SNR, crank up the channel fader to 0dB, then just go light on the master bus... sorry I mean VERY light.

The problems we experienced with Hot Mangu were a combination of not enbough filters on the various mics, too much volume (it's very hard to judge volume when the system is so clear), and not enough compression on certain channels.

I have also properly fixed the sub-woofer issue using the internal crossover and a little EQ, freeing up a monitor channel in the process. The subwoofer issue was largely due to lack of filters on the cabinet mics, and not enough filter on the vocal mics. Having every wedge on it's own channel has further improved the feedback situation.

Mark Thomas has been an enourmous help again this week, and these improvements have followed on from his advice and input.

Now we are starting to get some seriously good sound. I am eagerly anticipating both the Wrecking Ball on Friday, and the AUBL Exposure night this Saturday. If you thought the sound was good before then prepared to be truely amazed.

Even the jukebox is sounding much better.

The Moorings with a reverb and delay on vocal... surely not... not... not... not.

[Flash@TMB]

More Tweaks

I used the open mic session yesterday as an opportunity for further refinement of the basic settings. Along the way I discovered a neat trick that the digital parametric EQ can do that analog would struggle with. The result is the ability to use much tighter filters and also better control the bottom end on the kick drum and floor tom.

This has produced a much tighter drum sound with far better separation between the kick and the floor tom as far less bleeding between those mics. The kick drum sound is now approaching what you'd expect in a studio where it's isolated. A similar technique was employed to tighten up the bass, although there wasn't so much wrong with it.

I also discovered the location of some more annoying mud on the guitar channels. This was eliminated using tighter filters. Similar changes were employed on the vocal channels, hats, overheads and snare to further reduce feedback and certain unwanted low end effects.

We're now pretty much at the sound that we were aiming for when we installed this system. I'm really looking forward to the next gig.

The digital parametric EQ is incredible, and producing a basic setup would be relatively straightforward having done it once. It is MUCH more complicated that analog, mainly because there is more scope for tweaking and less scope for colouration. I've discovered that with the old analog desk I was unwittingly using it's colouration to sweep cetain problems under the carpet. With digital WYSIWYH. It's this exposure to dealing with the full extent of the sound that took me by surprise and has resulted in a much longer bedding in period that I originally anticipated.

[EPICURUS]

Re: More Tweaks

Originally posted by Flash@TMB:

We're now pretty much at the sound that we were aiming for when we installed this system. I'm really looking forward to the next gig.

surely thats all you needed to say? the rest is bloody gobbledegook to most folk im sure. who cares?!

[Guest Bob Double Jack]

Re: Re: More Tweaks

Originally posted by EPICURUS:

surely thats all you needed to say? the rest is bloody gobbledegook to most folk im sure. who cares?!

That is funny.

[Flash@TMB]

Re: Re: More Tweaks

Originally posted by EPICURUS:

surely thats all you needed to say? the rest is bloody gobbledegook to most folk im sure. who cares?!

It is short sighted to assume, that out of the hundreds of people subscribing to a site called aberdeen-music, nobody has any interest in sound engineering.

Weirder still is that you keep reading and responding to my threads on this topic, albeit in a negative way. If you really like responding to boring technical stuff that you have trouble following, then this should be right up your street:

http://www.ytmag.com/cgi-bin/boards.cgi

[Cloud]

You're into antique tractors, Flash?

Well, I never

[Flash@TMB]

Originally posted by Cloud:

You're into antique tractors, Flash?

Well, I never

My idea of a good game of squash involves a bunch of neds in a confined space and me in a traction engine.

[Hog]

Re: Re: Re: More Tweaks

Originally posted by Flash@TMB:

It is short sighted to assume, that out of the hundreds of people subscribing to a site called aberdeen-music, nobody has any interest in sound engineering.

Weirder still is that you keep reading and responding to my threads on this topic, albeit in a negative way. If you really like responding to boring technical stuff that you have trouble following, then this should be right up your street:

http://www.ytmag.com/cgi-bin/boards.cgi

Thats what I though! Surely Flash is allowed to chat about music related issues on a music related website??(

[EPICURUS]

Re: Re: Re: More Tweaks

Originally posted by Flash@TMB:

If you really like responding to boring technical stuff that you have trouble following, then this should be right up your street:

http://www.ytmag.com/cgi-bin/boards.cgi

nah, your technical talk is still more boring than that!!

[Flash@TMB]

Well brace your masochistic little eyes for this lot then...

We've been having some problems with an ever changing selection of rogue frequencies in the bass and lower mid ranges. On Monday we carried out an accoustical analyses to find out what was causing them.

It was discovered that:

The bass bins were resonating through the floor. Different bass guitars were reasonating differently.

The face panel between the bins was acting as a second kick drum / bass resonator.

Both of those were resonating at 20-150Hz.

The face panels under the low mids were resonating between 160 and 350Hz.

We cured the 20-150Hz issues by ripping up part of the floor and placing the bass bins on 10mm accoustic mat layered with 10mm of neoprene. We then braced the centre panel to raise it's resonating frequency range and dampened it with accoustic matting.

There was not anough accoustic matting to deal with the face panels under the low mids, but I have ordered some more. We'll also brace these further so that they reasonate a little higher up.

This has tightened up the bottom end a lot. Listen to Duran Duran's Planet Earth on the jukebox to hear the difference. Prior to this treatment the bass on certain tracks was coming through far too loud.

The low mid reasonance is now more apparent but we'll deal with that real soon.

The quiet monitor has also been fixed... my fault, and I can remember this happening. I was adjusting the EQ on a tom tom, when MTA changed the active layer to master from the laptop - we didn't realise this would occur on the desk at the same time, so my tom tom suddenly became one of the monitors... and I wasn't paying enough attention and so wasn't sure what I'd twiddled. Ooops. So for 3 weeks the monitor has been quiet. Too quiet.

Once we get the resonance problems fixed we'll ring out the room again and maybe fire up the pink noise analyzer. I reckon all the wierd feedback issues will go away... not that they have been that apparent during the gigs as MTA has kept everything well under control. It's just makes our job a bit less fraught.

[Flash@TMB]

This worked beautifully. MTA and myself ran the spectrum analyser seven times and each time it came out showing the frequency response curve of our mic. In other words the spectrum is flat and the system is tonally perfect. The reason we ran it seven times was that MTA couldn't believe the result - not because it doesn't sound perfect, but because it's extremely impressive for a PA system to deliver a uniform frerquency response.

This Friday Nick Taylor and I are scheduled to install a second set of delay speakers (plus the corresponding amp) further back on the last ceiling beamto provide better downfill to the rear of the house. These speakers (and their amp) are exactly the same as the existing delay speakers so there should be no impact on the sonic performance. The existing delays will be angled down slightly more to provide better downfill to their immediate area.

The purpose of this is to reduce the overall volume required to drive sound clarity to the rear of house. This means that gigs will be at a lower volume but the sound should be much clearer at the back.

I've also raised the guitar cabs higher up, as this makes it easier for the players to hear their amp, and reduces the volume required to produce distortion, leaving the sound engineer with better control over the sound.

It's safe to say that we are now achieveing the sound that we were originally aiming for. I just didn't expect it to take this long to get there!

Phew. Signing off.

[MTA]

So the new delays going in today?? I cant wait to get out the studio and give them a go!

After all the acoustic treatment done It is the best sounding PA in Aberdeen no question...

See ya soon MTA...

[Tav]

I'm so glad I don't own/install/run a PA...seems like a lot of hard work and endless twiddling.

[MTA]

I'm so glad I don't own/install/run a PA...seems like a lot of hard work and endless twiddling.

Yes it is hard work. But when it all comes togeather it's worth the effort. not only for the engineer but the people who want to hear the music. looking forward to trying the new delay fills..

[Flash@TMB]

I'm so glad I don't own/install/run a PA...seems like a lot of hard work and endless twiddling.

We enjoy doing this. But yes it's a lot more work that setting up a HiFi LOL.

The good news is that the twiddling requirement is reduced over time. It's at the point now where it's going to be hard to spot any further improvements - we've reached the point of diminishing returns.

The difference between the sound we have now, and the sound that we had when Hot Mangu came down to help with the initial test is incredible. Back then, although on paper we had the best PA in town, it was easily the worst sounding. Now in my opinion it is by far the best sounding, and I'm sure most people that heard E106 on Saturday would agree.

Hot Mangu are back in under 2 weeks time, it will be interesting to compare the difference!

Here's my checklist for doing comparing PA systems / engineers:

1) Pick a competent band with a clear sound, and attend all their local gigs.

2) Can you here every single musical component clearly, and at the correct level? Every nuance should be distinct. The hardest parts to get right are the vocals, the bass, and the drumkit. You should hear every part of the drum kit.

In my opinion there is a tendancy for other rigs to sound very muddy and be dominated by the bottom end. With our rig you can hear and feel the bass but it doesn't overwhelm anything else, and has beautiful clarity.

3) How low can they go? The rig should sound the same at all volumes, only louder/quieter. The actual sound shouldn't change. Is the venue able to play recorded music through their rig at background volumes? If they aren't doing this then my guess is they can't (although I'm sure they'll have another excuse). We play the jukebox through our rig all day, every day. For an excellent demonstration select "Don't Let it Show" off the Pat Benatar CD, and listen carefully as the intro fades in. That track also has exceptionally good dynamics, so listen to the change in volume as the drums kick into the mix.

Badly produced CDs should sound no different, or perhaps even worse than normal. Good CDs should sound like the band are really there, and the effect can often be amazing on a good system.

4) How quietly can they do the actual gig? Volume is often used to cover up problems. I resorted to this during our early gigs until we had the system sorted out. If you have good clarity then you require less overall volume.

5) How loud can they go without any loss of clarity? No matter how loud they go everything should sound clear right up until the point you feel physical pain in your ears. Any loss of clarity is due to distortion from the rig and not your ears. With good rigs people often don't realise just how loud things are until they attempt to talk to someone.

6) If you close your eyes, or turn your back, can you clearly ascertain where everything is on stage? Can you tell if the drummer is left or right handed? This is simple for the sound engineer to do, but one of the first things to be sacrificed to cover up other problems.