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Author Topic: Getting New Amplifiers Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-08-2011 07:24 PM                     I just got back from Mercyhurst after an emergency call. There was a power failure. Some equipment needed to be rebooted (Media Matrix) and there was also an amplifier that died. We have everything working at a nominal level but one of the amps for the house system will need to be replaced. I am also asking for new, better amps for the cinema system. We are probably going to replace all the amps in both systems. That will total 6 or 7 amps for the house sound system plus the ones for the cinema system. We can just assume that there will be 6 amps to replace in the house system. (The 7th would be a spare.) The amps in the house system are 15 years old and they are on their last legs. We have been having problems with them. They are dying one by one. The amps in the house system are all Crest. The amps in the cinema system are all a mish-mash. There is a QSC USA-900 driving the L & R channel. (1 channel for each speaker.) The C channel is driven by a QSC 1000 watt amp. (Only 1 channel of the amp is used.) The subs are driven by a pair of Altec 500 watt amps. (1 amp for each speaker.) I am asking for all the amps to be QSC, house and cinema. What's the best way to set up the amps for the cinema system? As of right now, there are 3 speakers for the L/C/R and 2 for the subs. L/C/R speakers are all JBL 4675C full range / passive crossovers. (Inside the cabinet.) The subs are Rhenkus-Heinz 18 in. cabinets. 2 units. Here's what I'd like to do: Get 4 amps @ 1,000 watts each and bridge them. Use 1 amp for each channel. Operate them full range, using the crossovers in the cabinets. If, at a later date, I am able to get a crossover system and run the extra wire, I would like to take the amps out of bridge mode and use 1/2 of each amp for high frequency and the other for low frequency. Does this make sense? Or, do you have a better idea?  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 02-09-2011 06:37 AM                        Wow: who did this to you? QSC is certainly good enough, but the USA series is one of the most heinous amps ever made. . . . maybe worse than some of the Smarts. The Crests are not much better (no bottom.) Good plan. You may want to be sure that the amps have a crossover already, even though you aren't going to use it right away. Consider a 750 Hz frequency, rather than the m ore typical 500. You will not believe the difference in quality between the passive crossover and the active, no matter how good the passive is. Louis  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 02-09-2011 08:38 AM                     The USA amps were decent they were the series 2 amps such as the 1400 Sold lots of the USA and almost all are still in service unlike all the Ashleys and Haflers that seem to be going in the bin  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-09-2011 09:33 AM                       Got to agree with Gordon. The USA 900 is under the skin the same as the 1400. Plenty still running.  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-09-2011 09:33 AM                     Randy, If your end-game is to go to bi-amp then choose amps based on that scheme...to know the size, you need to provide the auditorium dimensions. The Passive crossovers in that speaker are not going to be able to take all of the power your amps will provide but that is okay, you'll not be driving them that high anyway. Be careful though...the 4675C is a 4-Ohm cabinet...when you bridge an amp into it, you will effectively be driving that amp into a 2-Ohm load...make sure your amp can deal with that well and that the distortion does not climb way up. With the 4675C, I prefer the 500Hz crossover point...it does better with dialog there. With the smaller 2380 horn, I would agree with Louis and say going to even 800Hz improves its usability. Out of curiosity...if you are buying everything for bi-amp...why not just do it from the get-go? What is the extra cost? The crossovers? Three channels worth is going to be under $500.00 in analog form so now you are down to mere cable differences...6 pesky little wires. -Steve  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-09-2011 09:44 AM                     I would really like to have the speakers bi-amped. That's the reason I'm shooting for a bridged, 1,000 watt amp, per channel. That way, if I can ever get the go-ahead it would be possible to split the amps back to dual channel operation and use one half for the high side and the other half for the low side. Like I said, all I would need is to have some extra wires run to the stage then add a crossover. I would leave space in the rack for the crossover so all I would need is to bolt it in and hook it up. I probably would not be able to get the QSC amps with integral crossover. We're probably going to get 10 or 12 of the same/similar model amp. Seven for the house system. Four for the cinema system and a spare. I heard a story about those USA-series amplifiers where the designers couldn't find a way to get all the noise out of the circuits so they designed a noise generator into the circuit and reverse-phased it to cancel out the noise. Is that really true?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-09-2011 12:57 PM                     quote: Steve Guttag .....Be careful though...the 4675C is a 4-Ohm cabinet...when you bridge an amp into it, you will effectively be driving that amp into a 2-Ohm load... Now how the hell do you come up with that? A 4-ohm speaker is a 4-ohm speaker, no matter what amp is driving it, bridged or not. As long as the amp is capable of driving a 4-ohm load in bridge mode, there is no problem. Take a 4-ohm resistor, drive it with an amp, connect it to a battery, or feed it 120,240,480 vac and it is still a 4-ohm load. (Other than frequency-dependent impedance changes.) Randy, the DCM series of amps would probably give you the best bang for the buck in your situation. Good power, excellent reliability, easy to add crossovers to later, and you can use a DCM series monitor for everything including the PA.  |  IP: Logged Jarret Chessell Master Film Handler Posts: 288 From: London, Ontario, Canada Registered: Jan 2009 posted 02-09-2011 02:42 PM                     I think what he means is that if you put a stereo amp into a bridged configuration, you're turning two amps into one, which also means that each amp is doing half the work. That would mean half the work of a 4 ohms is 2. I'd just use half of each amp until you go active and not explain your reasoning to whoever pays the bills  |  IP: Logged Steve Guttag We forgot the crackers Gromit!!! Posts: 12814 From: Annapolis, MD Registered: Dec 1999 posted 02-09-2011 04:11 PM                     Jarret is partially correct...each half is doing all of the work but as far as the amp is concerned, the load is 2-Ohms. Yes, Tony, the AMP, if its rated into 4-Ohms BRIDGED will be fine but if that amp has a 4-Ohm bridged rating will also have a 2-Ohm stereo rating...why? The amp channels are being loaded the same...you find the distortion ratings tend to follow in that too. Since USA 800 amps were brought up prior in discussion...there is an amp I would NOT run into a 4-Ohm load Bridged...I've tested the USA amps into 2-Ohm stereo and they REALLY over heat and their distortion figures go WAY up. I think there was a period where QSC gave them a 2-Ohm rating (stereo (4-Ohm mono) and it was with something like 1% distortion with 1KHz. For many amps, driving into that low impedance gets one more distortion but there are those, like the DCA that seem to have no problem whatsoever. In fact, the DCA1222 is fine down to 1.6-Ohms. (A little under published fact.) But seriously Tony...do you really think I don't know my way around amplifiers and electric circuits? -Steve  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-21-2011 06:16 PM                     Just got a message back from our dealer about the amps we need to replace. He is asking me what I think Ashly KLR Series. http://www.ashly.com/klrseriesamplifi.html Specifically, the KLR-2000. 2,000 w @ 4 Ω/Bridged -- 600 w @ 4Ω/Stereo It kinda' looks okay to me but I've never used Ashly before. What do you all think?  |  IP: Logged Tony Bandiera Jr Film God Posts: 3067 From: Moreland Idaho Registered: Apr 2004 posted 02-21-2011 07:43 PM                     Search Ashly amps here, Gordon has some info on them. EDIT: Here's post #3 in this thread: quote: Gordon McLeod The USA amps were decent they were the series 2 amps such as the 1400 Sold lots of the USA and almost all are still in service unlike all the Ashleys and Haflers that seem to be going in the bin I wouldn't use anything other than QSC DCM....for the price, you can't beat the reliability, energy efficiency and performance. Sounds like your dealer is pushing Ashly because he can get them cheap and charge a higher markup.  |  IP: Logged Sam D. Chavez Film God Posts: 2153 From: Martinez, CA USA Registered: Aug 2003 posted 02-21-2011 07:48 PM                       IMHO, it's too late for Ashly in cinema. They sell very few in our industry. Market share is almost zero.  |  IP: Logged Randy Stankey Film God Posts: 6539 From: Erie, Pennsylvania Registered: Jun 99 posted 02-21-2011 09:06 PM                     quote: Tony Bandiera Jr Sounds like your dealer is pushing Ashly because he can get them cheap and charge a higher markup. What else is new? He once told me that he convinced my boss to buy something just so he could get rid of it. You guys are saying pretty much what I thought. We'll buy the Ashlys for cheap but will end up buying new ones in a few years as they crap out. Right? I must have been a murderer in a previous life because there's no other explanation why I have to go through all this trouble just to buy a few freakin' amplifiers!  |  IP: Logged Louis Bornwasser Film God Posts: 4441 From: prospect ky usa Registered: Mar 2005 posted 02-21-2011 09:59 PM                        That is a model from Ashly that I have no information on. The older series (sold nearly 8000) are all still running well, fully supported and no problems. I do not know of any Ashlys in the dust bin. Typical 8 plex has 80 modules(40 amps). 3 bad in 16 years is not bad. I will agree that the 3db down at 100k will cause an inadequate installation to not function well. Louis  |  IP: Logged Sean McKinnon Phenomenal Film Handler Posts: 1712 From: Peabody Massachusetts Registered: Sep 2000 posted 02-22-2011 03:43 AM                        quote: Louis Bornwasser 3 bad in 16 years is not bad. I am not saying this in any way to knock Louis at all as I consider him one of the good guys in this industry but... When I was servicing national amusements locations for NCS it was more like 3 bad amps per location ina given amount of time. Now. mind you these were complexes that were open for years and not out of the box failures. Most of the failures were worn pots or built in crossover failure. I would go QSC (DCM series is very nice) just MHO.  |  IP: Logged

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