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Author Topic: LAB problem ?  (Read 3624 times)

Bogdan Popescu

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LAB problem ?
« on: May 12, 2004, 03:38:48 pm »

Hi,

I am really concerned about what happened to my las gig a few days ago.
We where outside with 2 LAB's doing a small hip-hop event, just a 200 people thing. We installed first by putting the 2 LABs in front of the stage (10m long/1m high, solid concrete) approx 5m from another because not the whole stage was used. As we where testing around, i was not totally happy with my sub output, so i put them together in the middle. My surprise was that almost all of my low end was gone. I checked all the wires and cross (at 80Hz), faze etc, everything OK. I inverted the faze to one LAB and it was even worse.

5min after that, i was still clueless and the weather made a quick ending to my thinking, we had to carry everything inside and there we had a totally different box arrangement and everything was finally OK.

I used the LAB's stacked together before, same setup, same cables, etc. and everything was OK. Just this time i used A cheap amp (Tamp3600, 2x1600@4ohm)...which inside behaved OK

I am really concerned, because in 2months i will have to hard rock a festival for 1-2000 people and i have to use 2 per side.

Please give me some good ideas, i am really scared.
Bogdan
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Mike Pyle

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Re: LAB problem ?
« Reply #1 on: May 13, 2004, 04:44:41 am »

How far from the front of the stage to the subs? If they were not right against it, you may have been getting boundary cancellation between the solid stage and the sub cabinet placement.
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Marjan Milosevic

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Re: LAB problem ?
« Reply #2 on: May 13, 2004, 05:01:59 am »

Hi Bogdan,

I am seriously considering that T-amp 3600 (budget shit - you know) so please comment it.

I am doing partyes for no more than 500 people with two labs and the power 2x1600 at 4 ohms is just suitable.

They seems robust and solid build and heavy which is leading to conclusion that solid power suply is used (big trafo).

I realy doubt that the amp was the factor for your problem.

Please comment.

Regards
MarjanM

Bogdan Popescu

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Re: LAB problem ?
« Reply #3 on: May 14, 2004, 12:49:29 pm »

Hi,

I was hoping all you sound - guru's can give me a solution to this problem Very Happy ... well didn't had any chance to try this setup again, but i hope i will soon.

The sub's where placed 10cm from the stage in a straight angle, but i am telling you there was for sure a real huge cancelation, Is that possible just because of placement ? Is it maby possible that the 2 channels of the amp are not in phase or something ?

The T-amp 3600 delivers good power and is very punchy. Indeed it has a real big toroidal trafo and seems to work ok. The case is not as strong as it should for this kind of weight but you can live with it.
Didn't have any chance to test it in a HI-FI environment, i always do. Also time will tell if it was a good investment, but over the night it didn't get worm at all, i pushed it for a few times to red but only short, because i was worry-ed about the LAB's and also didn't have any backup.

Regards to all,
Bogdan

Conclusion: if it holds in time, certainly it is worth the money. Rolling Eyes  Rolling Eyes
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Marjan Milosevic

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Re: LAB problem ?
« Reply #4 on: May 15, 2004, 07:01:21 am »

Hi Bogdan,

Tahx for the reply for Tamp. I will see now how to get one from Germany.

So, about your problem...

Labs were 10cm from the solid concrete stage, plus 114,5 cm to the labs mouth total 124,5 cm, and that will cose serious boundary cancelation of the range between 50 - 60 Hz.
that is the range were all the punch is, so that is for sure the cose of the lack of bass.

In that kind of environmet I would have put them in front of the stage faced mouth to mouth on some 1,5m distance with improvised mouth extensiot (something like Brad Litz did for the home cinema).

Otoh I have never tried this I think it would work OK (some kind of corner loading).

Hope this helps,
Any coments from others?

Regards
MarjanM

raj

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Re: LAB problem ?
« Reply #5 on: May 16, 2004, 03:48:06 am »

Bass cancelation could take place if both speakers would be in reverse polarity of each other,but there is no chance of your connecting them wrong,you also say that you crosschecked the connections,there is a possibility that your amp was in bridge mode and your speakers connected in stereo ,like this the output from the amp would be +ve in one channel and -ve in the other,such a mistake can happen ,when you are in a hurry.
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RL

Bogdan Popescu

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Re: LAB problem ?
« Reply #6 on: May 16, 2004, 04:18:59 am »

Hi,

No the amp was not in bridge mode, because it deliveres 2x1600@4ohm, so each channel was on 1 LAB, polarity can not be wrong, i use the same cables for long time and i double checked them with a cable tester. Also as they where running with this huge cancellation, i reversed the polarity to one channel and it was worse.
I suspect Marjan could be wright. The only other thing i can think of is that the Tamp has some crazy phase mismatch between channels, but didn't hear of something similar before.
I never had the chance to work with solid concrete stage before so this was a surprise for me. It must be some cancellation, the stage is only 80cm high... i worked against solid concrete wall before with no prob at all.

Thanx,
Bogdan
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Marjan Milosevic

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Re: LAB problem ?
« Reply #7 on: May 16, 2004, 07:39:32 am »

Hi Bogdan,

You said that when you revesed one channel it was worse than before so I dont belive Tamp has reversed channels, and back indoor everything was fine.

Try that set up again if you can. Even on low power (if neighbors are problem) you will notice the diference.

Regards
MarjanM
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