EIA sensitivity?

gogofast

Addicted Member
i've read some spec sheets that has EIA sensitivity ratings of speakers. i also heard someone saying that you add 50db to EIA sensitivity in order to convert it to db/1w/1m.

is this correct?

i have a EV SP15b that i'm trying to use in a low powered tube guitar amp. if the above conversion is correct, it has 100db sensitivity, and i'm comfortable with that.

also, is 30 - 15000 hz enough freq. coverage to be used as guitar amp speaker?

thanks for any input!
 
The old EIA (AKA RETMA) standard was 1mw/30 feet. A common ROT conversion is +49dB.

A guitar's fundamentals range from 82 to around 880Hz (high end depends on fretboard length). 40Hz to 4kHz will allow 2 harmonics and one subharmonic, and let it sound like a guitar.

Just 'cause a rating says 30-15kHz doesn't mean much though. The box affects the low end and the driver's size affects the high. By ~1kHz a 15" will be beaming, so off-axis response is lost. That's why most guitar speakers are 10s & 12s.

All the rules are out the window for guitar speakers though, 'cause how it sounds to you is all that matters (you'll never hear those words from me RE HIFI :D). Stick it in a cardboard box and try it out.
 
The old EIA (AKA RETMA) standard was 1mw/30 feet. A common ROT conversion is +49dB.

A guitar's fundamentals range from 82 to around 880Hz (high end depends on fretboard length). 40Hz to 4kHz will allow 2 harmonics and one subharmonic, and let it sound like a guitar.

Just 'cause a rating says 30-15kHz doesn't mean much though. The box affects the low end and the driver's size affects the high. By ~1kHz a 15" will be beaming, so off-axis response is lost. That's why most guitar speakers are 10s & 12s.

All the rules are out the window for guitar speakers though, 'cause how it sounds to you is all that matters (you'll never hear those words from me RE HIFI :D). Stick it in a cardboard box and try it out.

thanks for the info!
i just have too many junks lying around my garage - i thought i'd build something useful with whatever i have. :thmbsp:
 
You're welcome.

Yeah, I'm a 'run whatcha brung' kinda guy too. Look what I did to Granny's old suitcase;

suitcase%201.jpg


suitcase%202.jpg
 
You're welcome.

Yeah, I'm a 'run whatcha brung' kinda guy too. Look what I did to Granny's old suitcase;

suitcase%201.jpg


suitcase%202.jpg

niiiiiice!

that's really cool. i'm thinking about building something similar with either akai R2R mono blocks or magnavox console amp in a beat up rickenbacker cab. i got a left over leather from plycraft re-upholstering and hope to use it for the cab. it sure is nice to use crap and create something useful. :thmbsp:
 
...it sure is nice to use crap and create something useful. :thmbsp:

Way better than using something useful and creating crap...:D

An old RTR mono would likely be more of a 'drop-in' MI amp than a console model, particularly one with mic inputs. Good luck! :thmbsp:
 
yeah, i just restored and modded two mono blocks and they sound surprisingly good even as hi-fi use - even before any recap. specially, these power trannies don't even get hot after 8 straight hours of listening today. very nice.
 
bfishn, I like it !!! What tubes and circuit are you runnin' there? The metal envelopes look like some 6SQ7 tubes I have but I suspect they three are 6SC7s. And the power tubes look like maybe 6K6 although I would expect maybe 6V6s?

I like the insulation spare tube holder too, very creative. Haven't seen that before but maybe I don't get around too many guitar rigs. Dowel and tubing extensions are neat too. Certainly some ideas I can take away from this.

Oh, to keep something here OT, where does one locate EIA/RETMA effeciency numbers?

-Buck
 
bfishn, I like it !!! What tubes and circuit are you runnin' there? The metal envelopes look like some 6SQ7 tubes I have but I suspect they three are 6SC7s. And the power tubes look like maybe 6K6 although I would expect maybe 6V6s?

I like the insulation spare tube holder too, very creative. Haven't seen that before but maybe I don't get around too many guitar rigs. Dowel and tubing extensions are neat too. Certainly some ideas I can take away from this.

Oh, to keep something here OT, where does one locate EIA/RETMA effeciency numbers?

-Buck

In place are 6SC7s and 6V6s as you guessed, but I can swap in the 6L6s (by also swapping the 5Y3 for a 5U4) at will. The circuit is Fender 5E3 with a custom dual channel front end. The chassis was born with 7V Loctals, so the original PT is pushing 7.5V to the 6.3V filaments which has a nice effect. :yes: The 4th control adds variable R to the feedback loop, which doesn't affect the 8" Wurly speakers too much, but has a big effect on some external cabs. With the 6V6s, it's pure brown Tweed, the 6L6s make it sound Black (and louder than stink).

An unplanned bonus, when closed up, the speakers are almost touching the tubes. Microphonics abound, making excellent sustain.

I think the tube holders and control extensions are original, a product of Missouri farmboy make-do. I'm actually kinda proud of the u-joint extensions (1/4" dowel & fuel hose), and they work quite well.

You can find EIA ratings in old sheets, mainly EV.
 
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