PA: Getting the most out of it??

[cheddatom]

For the last couple of years we've had a crappy Kustom 100W PA. It came as a deal, two crap 10" speakers, a crappy power amp and a free mic. We always struggled to get much level out of it, and it's always been a bit distorted and muffled. We have it turned up as much as possible before feedback kicks in.

Recently i've set up to record every practise, which means the mics now go to a mixer, and a line out from that goes into the PA. The mixer has a better EQ on it, and by cutting some frequencies I got a little more level out of the PA before it started to feedback.

More recently I bought a couple of Peavey PA speakers which are 12" and have tweeters. These sound a lot clearer, and it seems I could get more level out of them than the other speakers, but I can't turn it up because the point of feedback seems to remain at the same point. Also now that it sounds clearer it seems i'm getting some distortion from somewhere.

On the back of the PA it has two outputs for speakers that both say 8 Ohm. Both my good (peavey) and sh*t (kustom) speakers are 8Ohm, so, without re-wiring them, I think I can only run one set at a time?

At the moment I have the two speakers in between the two singers, at right angles to their mics, angled back to basically point at their ears.

Any tips?

[Happy Jack]

Bear in mind that, from your own description, you're well into turd-polishing territory here.

I don't understand your description of how you have the speakers angled. If you're set up for stage use, then the speakers should be pointing at the audience; if you're using them as monitors, then the speakers should be in front of the vocalist(s) and pointed at the back of the microphones.

If feedback really is the major issue, then buy a cheap feedback destroyer such as the Behringer 2496. I prefer the equivalent unit by Sabine, and the Peavey Feedback Ferret is good too, but the Behringer will do a job for you.

[cheddatom]

I don't have leads long enough to have the speakers facing back towards the singers at the moment, although that would help a bit I suppose.

Well, level is the major issue, and the only thing in the way of that (AFAIK) is feedback. Perhaps though I have some of my gain set wrong which is creating distortion which could make the whole system more susceptable (SP?!?) to feedback.

I've attached a pic to try and explain the set up.

[51m0n]

Assuming you can insert one into the output then what you need is a 31 band graphic or a good feedback destroyer (probably worth more than the rest of the PA).

Should be able to get over 6dB more out of it if you set up the graphic right. Which is 4 times louder....

[cheddatom]

I was considering that, but I have the parametric on the desk and it has a 7 band on the main output which i've been using. Do you think a big 31 band (thought they were 32?!) would make a big difference? I could put that on the line from the desk to the PA.

Perhaps the best solution would be to buy a fairly decent powered mixer with inserts for recording the vocals, but then I might still need the EQ.

[crez5150]

I think that before you go down the route of more outboard equipment you may want to address the amplifier. If you are going into a mixer and then into the Kustom amp.... no amount of outboard is going to give you greater output. I'd ditch the kustom amp/mixer and buy half decent power amp and use the mixer you already have.

You would see a noticeable difference

[cheddatom]

Well, yeh, that's what I was wondering really. "Is it just that the power amp is sh*t? " well apparently yes.

So cheap power amp solutions? And putting the two sets of speakers together would I think give me 4Ohms each side, so i'd want one that goes down to 4 Ohms..?

Ta for all the help guys

[51m0n]

It cant be the power amp. Thats daft, a bigger power amp will still feedback at the same point!

His volume issue is not that the amp is crapping out, its that he gets feedback before its loud enough.

If you buy a bigger power amp it will just feedback at the same volume. Net gain in volume = 0

You have to attenuate the problem frequencies (using a graphic).

Problem with a 7 band is its too wide band. Thus you knock out one band and then cant hear anything for a significant amount of frequencies either side.

Another thing you can do is buy mics with a more Cardioid response, of course you need to position them such that the off axis is where the PA cabs are.

[crez5150]

Dissagree.... plus he may have issues with gain staging if he's going through two mixers..... a 100w Kustom mixer amp will be fairly shoddy on the power front driving two of the peavey cabs. having a dedicated poweramp should afford him more power. yes he may have frequency issues but do away with the not so great set-up and have a simple signal into mixer into amp will be far less a complicated signal path.

May help also to look at mic and speaker placement

[Ian Savage]

[quote name='51m0n' post='863045' date='Jun 10 2010, 10:56 AM']Should be able to get over 6dB more out of it if you set up the graphic right. Which is 4 times louder....[/quote]


Ummmmm....what?

Trying to get vocals to compete with anything but a few acoustic instruments using a 100W Kustom amp is beyond turd-polishing, it's at the point of mounting turd on a plinth and giving it a Turner Prize. You could get a decent, 500W+ power amp for less than £100 secondhand (there was a Studiomaster 700D amp on eBay for a ton BIN for a couple of weeks not long back, 2x350W into 4 ohms, and I've not long picked up a 850W QSC for £115 delivered) - run the mixing desk into that, make sure you've got your gain staging right - oh, as a thought, are you still using cheap and sh*tty mics? 'Cos even a pair of Peavey PVis or something (twenty quid each if you shop around) will reject feedback better than cheap bundled crap, and if you can score a Sennheiser E385/840/845 for cheap secondhand, you're approaching professional level stuff.

[51m0n]

[quote name='cheddatom' post='862964' date='Jun 10 2010, 09:38 AM']...

Recently i've set up to record every practise, which means the mics now go to a mixer, and a line out from that goes into the PA. [b]The mixer has a better EQ on it, and by cutting some frequencies I got a little more level out of the PA before it started to feedback.[/b]

More recently I bought a couple of Peavey PA speakers which are 12" and have tweeters. These sound a lot clearer, and it seems I could get more level out of them than the other speakers, [b]but I can't turn it up because the point of feedback seems to remain at the same point[/b]. Also now that it sounds clearer it seems i'm getting some distortion from somewhere.

....[/quote]

I'd agree his entire setup defines the word shonky.

However his feedback is still going to be there if he swaps out the power for a seperate better quality amp and simplifies his signal chain, unless he either moves cabs, moves mics or gets some proper eq.

With proper eq (set up well) he will be able to get more volume before feedback, potentially significantly more volume, even with a crud underpowered amp. The quality will still be crap, but it will be louder and crap, which was the requirement. Although still probably not loud enough.

The question was 'how do I get the feedback to stop?', it may have been better if it had been 'is this a viable solution at all?'

It is as you say, a turd being badly polished, put on a plinth amongst a collection of other turds.

Or - not the way to go about it....

Oh and a huge +1 to the Senn E series mics, chuffing excellent for the dosh!

Edited June 10, 2010 by 51m0n

[cheddatom]

Sorry could I get an answer on this? Just to make sure...
[quote name='cheddatom' post='863143' date='Jun 10 2010, 12:09 PM']And putting the two sets of speakers together would I think give me 4Ohms each side, so i'd want one that goes down to 4 Ohms..?[/quote]

Because I am considering a poweramp, but I do tend to think i'll need to do something else to be able to use it to it's potential.

The mics i'm using are a 58beta and a 57. I have another 57 on the way, which is good 'cos this feeds back less, but I do prefer the tone of the 58beta.

I'll make some longer cables and put the cabs right infront of the singers, rather than at right angles to them. I'll also check my gain staging. I think maybe it's just too easy to overdrive the Kustom "line in", and I think i'm right in thinking that an overdriving signal path is much more likely to feed back as there's less dynamic range?

Maybe there's a poweramp with decent EQ built in? I know I saw a bass amp on here not long ago with a really big graphic EQ. The line in on that sort of this might do?

If you can't, tell i'm a cheap skate.

[Ian Savage]

[quote name='cheddatom' post='863238' date='Jun 10 2010, 01:42 PM']Sorry could I get an answer on this? Just to make sure...[/quote]


Yep, if all your speakers are eight ohm, daisy-chaining two together will give you a four ohm load.


[quote]I'll make some longer cables and put the cabs right infront of the singers, rather than at right angles to them. I'll also check my gain staging. I think maybe it's just too easy to overdrive the Kustom "line in", and I think i'm right in thinking that an overdriving signal path is much more likely to feed back as there's less dynamic range?[/quote]

Nail, head, hit. The Shures you're using are super-cardioid (Beta 58) and cardioid (SM57), which are subtlely different pickup patterns - the SM57 will (should!) feed back less with the speaker directly behind it, the Beta 58 will perform best in terms of feedback with a pair of wedge monitors, one slightly to each side.

You're right that feedback's more likely with less dynamic range (which is why most engineers won't compress vocals being fed to wedge monitors), and it's also more likely with greater high-frequency content, which is obviously introduced by overdriving/clipping the amp.

[cheddatom]

Thanks for all the help.

So over the weekend i'll make longer cables and re-position the monitors. I'll have a look at power amps next month

[JMT3781]

The overdrive may be caused by the power amp clipping, 100w doesn't really give you much headroom.