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- This topic has 8 replies, 2 voices, and was last updated 10 years, 12 months ago by GnLguy.
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April 1, 2013 at 3:43 pm #4722
I have a B&K discrete power amp that is 150 wpc that was part of my stereo system in years gone by. I hate to sell it because being built with MOSFET transistors on the output, it has somewhat of a tube tone quality. Very clear and transparent as the audiophiles would say. B&K was one of those companies built good products but lost out due their management – or so I’ve read.
Wondering if any knows if the output of a computer onboard audio is high enough to use the PC as a preamp? I want to sell the remainder of the stereo system but if I can use the PC to drive the power amp, I have some nice JBL bookshelf speakers that I bought for $5 at a rummage sale – it would be a good setup for a monitoring system that one could use to really jam with.
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April 1, 2013 at 4:29 pm #10360
Hi Keith
If you plan on using the headphone output you will get lots of level, maybe too much. Keep all your levels low to try it, don’t want to damage those speakers. Keep your eye out for a preamp at those yard sales, will give you some more control and some EQ as well. If your sound card has outputs (RCA?) you should be fine.
Gordo
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April 1, 2013 at 6:10 pm #10362
@ChordGuy wrote:
Hi Keith
If you plan on using the headphone output you will get lots of level, maybe too much. Keep all your levels low to try it, don’t want to damage those speakers. Keep your eye out for a preamp at those yard sales, will give you some more control and some EQ as well. If your sound card has outputs (RCA?) you should be fine.
Gordo
Hey Gordo
Thanks for the input. To use the PC sound card, I would have to buy a special cable to go from 1/8″ phone plug to 2 – RCA jacks. Parts Express is here in the Dayton area and they always have a good selection of cables
I have a Carver preamp that will be on the auction block soon because I kinda want to stream line some my equipment to free up some space in my guitar room
And yes, I know what you mean about speaker damage. I was surprised when I found the specs on those speaker and they are rated @ 100 watts continuous. Another good thing is that the sensitivity was high, something like 92db @ 1 watt so it takes very little to drive them. -
April 1, 2013 at 7:27 pm #10363
Hi
I’m a big JBL fan. Post the model number if you can. 92 db is not really that sensitive but thats good. Usually sensitivity is a tradeoff for fidelity. Electrostatic speakers are notorious for their inefficiency but sound very good.
Pro audio speakers are often chosen for their efficency, folded horn bass bins are very common but limit the range of the speaker alot.
Speaker power ratings can be decieving. Best to have a amp whose output exceeds speaker handling. This ensures a clean unclipped signal which is hard on speakers.
There are 3 ways speakers are rated
RMS This is really the best to go by, gives the most accurate level of power handling
Peak RMS This is temporary levels and is typically twice the RMS
Continuous This is what manufacturers use for advertising 🙂 Usually 3 times RMS. This is how much Heat the
speaker can disperse before meltdown.
You should have plenty of clean headroom with your amp and I would’t worry about clipping.
If you play pre-recorded heavy metal or rap music, which is heavily compressed music, at very high levels you may have a problem, LOL
The only problem may be the age of the speakers. Paper cones can get brittle with age and “the surround” (The outer edge that is attached to the basket) can somtimes tear.
The only other caution is that if you plan on singing while you have the speakers up you may want the levels higher than you think thay are. While speaking or singing your ears are less sensitve, this is why you can’t listen and speak at the same time, so don’t rely on them for monitoring.Gordo
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April 1, 2013 at 9:04 pm #10364
I chose this amp carefully when I bought it. It has 2 db of clean headroom which would give me approx 250 watts of clean power on the peaks. Trust me – if its too loud, you’re too old – no worry about running it into clipping
The whole premise of Carver audio was high powered amps that produced extremely clean power. Bob Carver was constantly preaching that it wasn’t high power that blew speaker drivers, it was amps that power amps being pushed into clipping, pumping ‘dirty’ power, square wave clipping into speakers that blew speakers. The smallest amp that I remember Carver selling was a 200 watt amp that was built into a cube shaped enclosure that weighed less than 5 pounds.
I can’t remember the sensitivity of the JBL speakers for certain so I’ll have to look that up again. When I said that they were fairly sensitive, I was referencing various speakers in my mind like McIntosh, that were power mongers, requiring 20-25 watts minimum to get them moving. Seems some of those were rated at 82 or 84 db @ 1 watt.
I looked at the cones and foam surround when I bought them and so far they are good. Foam kits are cheap enough on Ebay and easy to install if that does happens.
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April 2, 2013 at 12:34 am #10365
Back again
The relationship of power to output or volume is not linear. A 92db at 1 watt will need 2 watts to get 95db.
4 watts to get 98, 8 = 101, 16 = 104, 32 = 104, 64 = 107, 128 = 110, 256 to get 113 db.
Double the power for each 3db gain. Doubling speakers has similar gains.
The human ear hears a 10bd gain as aprox. twice as loud. I have done front of house sound for heavy metal acts at levels exceding 110db. Pain threshold for most is about 112 to 115db range. These were systems in the 30 to 50 thousand watt range. Prolonged exposure to levels over 90db can cause pemanent hearing damage.How silly does it get, here a link for Grateful Dead’s “Wall Of Sound” 75 ton’s and over 90 300 watt amps.
http://dozin.com/wallofsound/index.html
A search for this will yield real photos
A friend of mine “The Bear” , Owsley Stanley was responsable for this. (he is more well known for somthing else though, google his name)
A 20hz. sound wave is aprox. 30 feet high so thats the reason the PA is that tall.
For today humor
Three retired musicians were sitting around talking
The first says “Windy isin’t it”
The second says “no, I think it’s Thursday”
The third says “so am I, lets get another beer”Thus concludes Gordo’s live audio 101, thank you for your time.
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April 2, 2013 at 1:27 am #10366
@ChordGuy wrote:
Back again
The relationship of power to output or volume is not linear. A 92db at 1 watt will need 2 watts to get 95db.
4 watts to get 98, 8 = 101, 16 = 104, 32 = 104, 64 = 107, 128 = 110, 256 to get 113 db.
Double the power for each 3db gain. Doubling speakers has similar gains.
The human ear hears a 10bd gain as aprox. twice as loud. I have done front of house sound for heavy metal acts at levels exceding 110db. Pain threshold for most is about 112 to 115db range. These were systems in the 30 to 50 thousand watt range. Prolonged exposure to levels over 90db can cause pemanent hearing damage.How silly does it get, here a link for Grateful Dead’s “Wall Of Sound” 75 ton’s and over 90 300 watt amps.
http://dozin.com/wallofsound/index.html
A search for this will yield real photos
A friend of mine “The Bear” , Owsley Stanley was responsable for this. (he is more well known for somthing else though, google his name)
A 20hz. sound wave is aprox. 30 feet high so thats the reason the PA is that tall.
For today humor
Three retired musicians were sitting around talking
The first says “Windy isin’t it”
The second says “no, I think it’s Thursday”
The third says “so am I, lets get another beer”Thus concludes Gordo’s live audio 101, thank you for your time.
And Gordo
You should submit this to Audiophile Magazine – Gordo’s Simple Science of Sound. Has a nice ring to it.
I appreciate your input, took me back a few years and brought some of the high end systems to mind that I listened to at one time
Dalquist is/was another brand of speaker that was power hungry as well. Speakers were huge and need a ton of power to run. The DQ-10 reqd 60 watts minimum to operate but that is typical of electrostatic speakers.
http://www.hifiengine.com/library/dahlquist/dq-10.shtmlWhat does a speaker look like that that weighs 320 lbs and has a shipping weight of 380? 74.5″ tall?
Check this out
http://www.legacyaudio.com/products/view/helix/Here is the owner’s manual, looks like this comes with a 750 watt sub amp in each speaker
http://www.legacyaudio.com/images/uploads/manuals/Helix_Manual_1.pdfOf course, prices aren’t posted but the model just below this one sold for $12.500 a pair while they were posting prices
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April 2, 2013 at 10:02 pm #10372
Did FOH (front of house) for a few Yvonne Elliman shows in the late seventys with Electrostatic front end.
These were soft seaters (theaters) and her shows are very subdued or would not have been possible due to the volume limitations of tthe speakers. Very HI FI sound though.
Yvonne is most well known for “Jesus Christ Superstar” fame but sang backup on lots of other artist songs.
Remarkable voice, you brought back some good memories. She was better live than any recordings I have heard of her. Here’s a samplehttp://www.youtube.com/watch?v=qkrXvjrc5TY
with Eric Clapton
http://www.youtube.com/watch?v=n-wvfsGV1sE
An interesting point about those Legacy speakers. The manual shows a setup for them, positioned in corners of a room. All that research and money and the worst thing you can do with a speaker is put it in a corner.
Cup your hands in front of your mouth like you were calling to someone a distance away. Projects the sound very well but does nothing for the sound quality.Gordo
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April 2, 2013 at 10:26 pm #10373
Yvonne Elliman – remember her well for singing backup for EC. I remember some of the tunes from the late 70s that Eric gave her some of the spotlight.
Marcy Levy was another great backup singer that worked with Clapton as well.
And then there was Maria Muldaur. Great talent, her song Midnite At The Oasis didn’t showcase her talent as her ‘unknown’ song on her albums.
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