Post by: Dennis Butterworth on June 16, 2008, 10:36:55 PM
Thanks again!
Post by: Ivan Beaver on June 17, 2008, 02:00:41 AM
Just add the wattages the loudspeakers are tapped at and make sure that the number does not exceed 90% of the rated power.
Be informed that the "ratings" on consumer gear are often VERY suspect, so you might want to only go to half of the rating for saftey sake.
Trying to do "stereo" in a ceiling speaker situation is pretty much a waste of time.
Go to Atlas sound and look up 70V systems for some good info.
Post by: Hal Bissinger/COMSYSTEC on June 17, 2008, 01:23:36 PM
I also STRONGLY advise that you throw that consumer stereo receiver away and purchase the correct amplifier that will have the constant voltage output and multiple inputs that you need. You DON'T want stereo anyway.
-Hal
Post by: Don Boone on June 17, 2008, 03:18:28 PM
Don
Post by: Dennis Butterworth on June 17, 2008, 03:49:36 PM
Post by: Craig Hauber on June 20, 2008, 03:37:20 PM
They have some in-ceiling speakers with or without backboxes as well as plastic surface mount stuff that looks like what most people are used to for home installs ("Dayton" branded, as well as Atlas and other premium brands) -and prices listed.
Excellent source for those 1-off jobs by people who normally don't do 70V for a living.
Post by: Hal Bissinger/COMSYSTEC on June 20, 2008, 08:48:21 PM
Probably just about OK for PA and voice. God help you if you want to use it for music- unless of course you like a 200Hz- 10Khz response.
-Hal
Post by: Karl P(eterson) on June 20, 2008, 09:44:07 PM
| Hal Bissinger/COMSYSTEC wrote on Fri, 20 June 2008 20:48 |
Probably just about OK for PA and voice. God help you if you want to use it for music- unless of course you like a 200Hz- 10Khz response. -Hal |
That'll be the -10 down-points for you sir
Karl P
Post by: Craig Hauber on June 22, 2008, 01:49:07 AM
http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber= 300-416
I ran them at 4 watt tap and they still had decent LF. I will be trying them on some larger applications soon. I found them to be a really good deal at only $35ea. Came out of my own pocket, but client's ecstatic, landed 4 more contracts for new-builds.
YMMV
Post by: Hal Bissinger/COMSYSTEC on June 23, 2008, 12:05:58 PM
-Hal
Post by: Christian Tepfer on August 15, 2008, 06:58:10 AM
Post by: Eric Madson on August 15, 2008, 10:16:34 AM
determine the rated output of your amp and find a relevant transformer at the following link.
http://www.eidusa.com/Electronics_Trans_Audio_117_119.htm
ex: 60watts/8 ohms= EID-119Y60
wire the amps output to the txfrms 8ohm-common taps. Wire the speaker output side to the 70v-common side. This will give you the correct voltage ratio for a 70v tap at each speaker. Each speaker requires a 70v/watt tap and the total wattage of all the speakers tapped cannot exceed 60 watts. The txfrmr is rated for 50-10k but I would try to High pass the audio so it sees nothing below 80hz. Transformers do not like low frequencies because they saturate and look like a short to the amp. Jensen also use to manufacture some good audio transformers but I cannot find any on the web.
Post by: Hal Bissinger/COMSYSTEC on August 15, 2008, 11:44:40 AM
Some consumer receivers can't tolerate a 70 volt transformer on it's outputs. Decades ago I remember a DIY install that used a JVC receiver from Circuit City driving a 70 line. The receivers would last about a month. After the third replacment Circuit City cried foul and the customer had to buy a proper TOA 70 volt amp.
-Hal
Post by: Eric Madson on August 15, 2008, 12:06:41 PM
If you have a "consumer" or "pro" piece that is only rated at 100w@8ohms then the max rail voltage is only about 28v. If you try to tap off multiple 70v speakers for a total of 100w you will load the amp down past its rating.
If you step the output voltage up to give you 70v at rated out you will have no issues.
I have done this countless times with no problems. The only issues I have had is cheaper transformers that don't like lower frequencies. If you high pass you should not saturate the transformer at higher power levels. Make sure you purchase a good quality Audio transformer.
Maybe Don can clarify
Post by: Don Boone on August 15, 2008, 02:08:42 PM
BTW 100 watts of 70 volt speakers would be a 50 ohm load. The JVC could have handled that load with no problem as long as the bass was turned down. The level would be pretty low though.
Don
Post by: Eric Madson on August 15, 2008, 02:32:39 PM
Yes, assuming the amplifier is capable of reaching 70v.
Post by: Hal Bissinger/COMSYSTEC on August 15, 2008, 08:48:13 PM
Well yes. A 100w amplifier with a 70 volt output will deliver 70 volts across a 50 ohm load or more. A 100w amplifier with an 8 ohm output connected to the proper transformer (8:50) should deliver the same 70 volts at 100 watts, again across a 50 ohm load or more. So the amplifier would not need to deliver 70 volts, but as you say only about 28 volts at 100 watts. This is actually the way most constant voltage amplifiers operate. They use a transformer to produce the 70.7 or 100 volt output but they are also designed for it.
If you have a "consumer" or "pro" piece that is only rated at 100w@8ohms then the max rail voltage is only about 28v. If you try to tap off multiple 70v speakers for a total of 100w you will load the amp down past its rating.
No, not true. You will be putting a 50 ohm load on that 8 ohm output. Of course you will only be supplying about 16 watts to all of your speakers. The amplifier and speakers will operate quite happily though, assuming that's what you want.
Keep in mind also that consumer gear is not held to the same testing standards as commercial gear. The output power of consumer amps is usually hype. So that instruction book wattage you think you are getting could be much less. If you hang a transformer off the output and use it to feed a constant voltage system based on that assumed power output you may very well wind up overloading it.
-Hal