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Old 6th November 2014, 06:51 PM   #1
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Default Is 5 Watts enough?

I was planning to pick up a Inspire EL84 amplifier to power my B&W 640i.
My room is relatively small but I like to listen to music pretty loud. I also watch movies with these. Right now they are hooked up to a cheap 20 watt tripath amplifier. The speakers are rated at 4 ohm nominal Impendance and 91db spl(2.83V 1m).
Would the 5 watt Inspire EL84 satisfy my needs?
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Old 6th November 2014, 07:03 PM   #2
Mooly is offline Mooly  United Kingdom
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Five watts can be louder than you think.

Try this to get an idea,
A Test. How much Voltage (power) do your speakers need?
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Old 6th November 2014, 07:06 PM   #3
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Quote:
Originally Posted by VolumexD View Post
...The speakers are rated at 4 ohm nominal Impendance and 91db spl(2.83V 1m).
Would the 5 watt Inspire EL84 satisfy my needs?
Your speaker specs is a bit odd. 2,83 V to 4 ohms is 2 watts.
Isn't the the sensitivity usually specified at 1 watt ?

5 watts produce 4 dB more sound pressure than 2 watts, i.e. 95 dB spl.
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Old 6th November 2014, 07:15 PM   #4
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I'm picking the speaker has a pretty vertiginous impedance curve that would decimate any hope of an EL84 amp providing reasonable drive.

Power may not be a problem - impedance match will be.
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Old 6th November 2014, 07:15 PM   #5
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Quote:
Originally Posted by artosalo View Post
Your speaker specs is a bit odd. 2,83 V to 4 ohms is 2 watts.
Isn't the the sensitivity usually specified at 1 watt ?

5 watts produce 4 dB more sound pressure than 2 watts, i.e. 95 dB spl.
Ripped right out of the B&W website. DM640i

46Hz – 20kHz ± 2dB on reference axis
91dB spl(2.83V 1m)
4 ohms
30W – 200W into 4 ohms on
undistorted speech and music
programme
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Old 6th November 2014, 07:23 PM   #6
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Quote:
Originally Posted by VolumexD View Post
I was planning to pick up a Inspire EL84 amplifier to power my B&W 640i.
My room is relatively small but I like to listen to music pretty loud. I also watch movies with these. Right now they are hooked up to a cheap 20 watt tripath amplifier. The speakers are rated at 4 ohm nominal Impendance and 91db spl(2.83V 1m).
Would the 5 watt Inspire EL84 satisfy my needs?

IMO/IME it is highly unlikely that a 5 WPC tube amp will prove satisfactory, when mated to the B&W speakers. The "true" sensitivity of the speakers is 88 dB., as 2.83 V. into 4 ohms is 2 W., not 1 W. Paul Joppa's 102 dB. rule suggests you need a minimum of 32 WPC.

I would not mate the B&W speakers to tubed power amplification, except for a Harman/Kardon Citation II, which (for a tube amp) has a gargantuan damping factor. The "Deuce" works very well with AR-3s and AR-9s, which (I suspect) have much in common with the B&Ws.
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Old 6th November 2014, 07:26 PM   #7
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Then the sensitivity of your speaker is 3 dB less than a 8 ohms speker with 91dB spl (at 2.83V 1m), but this may not be any problem.
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Old 6th November 2014, 08:05 PM   #8
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SE EL84 will give You 4-5 Wt with distortions. For Your 90 dB speakers is suitable PP EL84 /12 Wt/ or more cheep PP ECL /PCL/82 or 86 /8-10 Wt/, only two tubes per channel, instead 3 or 4 tubes per ch. in PP EL84. You can find the treads with schematics on the forum. I'd like advice You.
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Last edited by azazello; 6th November 2014 at 08:08 PM.
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Old 6th November 2014, 08:12 PM   #9
BigE is offline BigE  Canada
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I would not make that pairing. Is this a setup you already own or considering buying?
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Old 6th November 2014, 08:23 PM   #10
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PHILIPS H4F 74 A/01 / ECL82 / 6BM8
"En sa Fonction PP delivrant 10 Wt" - this schematic. You can add input poti 50-100kohm. PS is next schem.
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Last edited by azazello; 6th November 2014 at 08:26 PM.
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