Advice needed! - How to run 12 small speakers from 1 amp using a splitter
in [Live Sound]
|
Prev: Advice needed! - How to run 12 small speakers from 1 amp usinga splitter
Next: Advice needed! - How to run 12 small speakers from 1 amp usinga splitter
From: Phil Allison on 26 Mar 2010 21:14 "liquidator" > "Phil Allison" >> "liquidator" >> >>> He's also wrong. all he needs to do is add transformers. Done it a >>> hundred times. >> >> ** Really ?? Not with domestic amps like Technics. >> >> Such amps are never intended to drive 70 volt line ( step up) >> transformers are very likely to be damaged by so doing. >> >> The issue is core saturation at low frequencies - hard to avoid >> completely and deadly on anything but the most rugged amplifiers. >> > > Interesting. Have done it dozens of times. Tend not to use Technics, and > do use quality transformers. > > What about a coupling capacitor or would that be a bad idea? ** An electro cap of about 1000uF ( a back to back pair is needed ) will at least eliminate any DC offset issues with the very low primary resistance of the line tranny - but adds the risk of creating a low frequency series resonance effects which can be even more deadly to the amp. > You are the one whose judgement I respect, perhapsI have just been lucky. ** You must have been extraordinarily lucky. It is reckless to connect a domestic or even most pro audio amp's output direct to a line voltage tranny - amp makers regularly warn against it. Generally, the amp requires modification and a network is placed between the amp and the tranny to limit current flow to a safe value if core saturation or overload occurs. QSC amps are particularly vulnerable to damage when used this way - seen 4 of them ( USA850s ) destroyed on the same day the install was done. ...... Phil
From: liquidator on 26 Mar 2010 21:32 "Phil Allison" <phil_a(a)tpg.com.au> wrote in message news:8154f5FdvrU1(a)mid.individual.net... > > "liquidator" >> "Phil Allison" >>> "liquidator" >>> >>>> He's also wrong. all he needs to do is add transformers. Done it a >>>> hundred times. >>> >>> ** Really ?? Not with domestic amps like Technics. >>> >>> Such amps are never intended to drive 70 volt line ( step up) >>> transformers are very likely to be damaged by so doing. >>> >>> The issue is core saturation at low frequencies - hard to avoid >>> completely and deadly on anything but the most rugged amplifiers. >>> >> >> Interesting. Have done it dozens of times. Tend not to use Technics, and >> do use quality transformers. >> >> What about a coupling capacitor or would that be a bad idea? > > ** An electro cap of about 1000uF ( a back to back pair is needed ) will > at least eliminate any DC offset issues with the very low primary > resistance of the line tranny - but adds the risk of creating a low > frequency series resonance effects which can be even more deadly to the > amp. > > >> You are the one whose judgement I respect, perhapsI have just been lucky. > > ** You must have been extraordinarily lucky. > > It is reckless to connect a domestic or even most pro audio amp's output > direct to a line voltage tranny - amp makers regularly warn against it. > Generally, the amp requires modification and a network is placed between > the amp and the tranny to limit current flow to a safe value if core > saturation or overload occurs. > > QSC amps are particularly vulnerable to damage when used this way - seen > 4 of them ( USA850s ) destroyed on the same day the install was done. > > > > ..... Phil > > I've seen USA series QSC's disintegrate in normal use. Never cared for that amp. Most of the time it was an MI grade system some bar owner bought and was stuck with. Towards the end I was specing the CX series QSC, the V models are optimized to drive lines without a transformer. That does change the wiring spec in Ohio though, if it is not transformer coupled wiring must be armored.
From: Phil Allison on 26 Mar 2010 21:35 "liquidator" > > I've seen USA series QSC's disintegrate in normal use. ** Really ?? The example I gave involved 4 brand new amps failing SIMULTANEOUSLY on the first day of use. > Never cared for that amp. ** Who cares what amps you are infatuated or not with ? ...... Phil
From: Scott Dorsey on 26 Mar 2010 21:35 liquidator <mikeh(a)mad.scientist.com> wrote: >"Phil Allison" <phil_a(a)tpg.com.au> wrote in message >news:8150qeFrjeU1(a)mid.individual.net... >> >> "liquidator" >> >>> He's also wrong. all he needs to do is add transformers. Done it a >>> hundred times. >> >> ** Really ?? Not with domestic amps like Technics. >> >> Such amps are never intended to drive 70 volt line ( step up) transformers >> are very likely to be damaged by so doing. >> >> The issue is core saturation at low frequencies - hard to avoid >> completely and deadly on anything but the most rugged amplifiers. > >Interesting. Have done it dozens of times. Tend not to use Technics, and do >use quality transformers. Wow. I had no idea Phil was still around! But yes, I have done it plenty of times, even using some pretty shoddy amps based on STK modules (like those Rane 1U power amps) and never had a problem. But I could see there being an issue with undersized output transformers if you aren't filtering the input of the amp. I have generally designed 70v systems for high quality audio to have a -3 dB point around 20 Hz, which requires pretty huge transformers. I strongly recommend the Tannoy transformers (which are actually made by some company in Canada for them) but the cheap Edcors aren't bad if you buy their "extended low frequency" series. For background music systems there's no need to have anything that extreme. >What about a coupling capacitor or would that be a bad idea? Bad idea if you put it after the amp, because the amp does not like driving capacitive loads. But put a filter before the amp so the amp never puts low frequencies into the system, and you'll be fine. Oh yes, and PLEASE use a fuse on the input to the step-up. This will save you some day when someone shorts out the wiring. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis."
From: Leon on 26 Mar 2010 21:36
On Fri, 26 Mar 2010 07:08:54 -0700 (PDT), wardy <conor2000(a)yahoo.co.uk> wrote: >Hi, > >Advice needed please from all you experts out there. > >I have a decent background in sound engineering and live mic/desk >setups, however I am no expert. I'm wondering what your "background" was... >I want to find the best way of installing a particular system in a >public venue. > >I am installing a Technics amp with normal Stereo output (+- L and +- >R) These things are usually about 100 watts, but are NOT rated for continuous use in professional venues... >I have to send the audio thru the amp to 12 separate speakers across a >sprawling venue. As Data used to say, "Insufficient information!" What kind of SPL do you require? >I have purchased a mono splitter and a stereo splitter. > >Firstly i tried the mono splitter so that each speaker would be mono. >I tried to convert this stereo output from the amp to mono by >combining the cables. firstly i tried to wire both the + outputs from >the amp into the + of 1 speaker cable and both the - into the - of >the cable. this however simply forced the amp to "click" off after a >few seconds of sound so i presume it wasnt happy with the level of >impedance of whatever. >So a mono splitter is out. NEVER parallel the output of an amplifier unless it's specified you can do so in the manual.... this can only work with a balanced mono input and matched gain anyway. >I am going to try the 6 way skytronic Stereo splitter next. >I am going to run 2 cables from the amp to the splitter (for L & R) >Then use the L and R channel from each of the 6 "rooms" on the >splitter as a separate L or R speaker on either side of the room thus >giving 12 speakers (6 L and 6 R). > >I havent set up a system where this many (12) speakers need to be run >by 1 amp before so need your input please so i can learn as much as i >can about running multiple speakers from 1 amp. You need to run the amp into a line transformer in reverse, and then feed each speaker off of another line transformer. I'd hate to do the math for this... Shutting off a speaker would unbalance the system, so you would need dummy loads if you want independant control. Not a big deal if you're talking 10 watt drops. Small transformers can be had for maybe $6 to $10 each... you would need bigger ones for the amp side, probably beyond your budget I'm afraid. I have a 45 watt transformer here and it cost $150. >Q - Does this sound like the best (and cheapest) solution? It sounds like a "Won't work at all" solution... >Q - Why did the amp click off when i was trying to join the stereo + >and - outputs to make one mono + cable and one mono - cable? The output stage of the amp is basically a transistor to positive, and another to negative, supply's... connecting one channel to the other with DIFFERENT audio signals (L and R) caused one channel to short out the other channels power, and vice-versa. Imagine two cars with their rear wheels connected by a tank track - now put the cars into different gears! What fun! >Q - anything you can teach me about wiring up Multiple speakers from 1 >amp using a speaker splitter from your own experience would be great. Your best bet is to connect the speakers in a parallel/series arrangement to maintain 8 ohms... and get dummy loads and DPDT switches to control them. I think you need to see someone about this... I'm not sure you can do it. Once you can understand all that has been said to you - then you can try! Good luck! |