From: bill@bilver.uucp (Bill Vermillion)
Subject: Re: Speaker efficiencies (was:  Re: Amp/speakers cut out -- Why?)
Organization: W. J. Vermillion - Winter Park, FL
Date: Thu, 10 Sep 1992 14:39:16 GMT

In article <1992Sep9.174140.27581@mnemosyne.cs.du.edu> tlode@nyx.cs.du.edu (trygve lode) writes:

>In article <BuBG63.9uA@world.std.com> DPierce@world.std.com (Richard d Pierce) writes:

>>In article <1992Sep8.144559.5402@julian.uwo.ca> mjscott@valve.heart.rri.uwo.ca (Mike J. Scott) writes:

>>>	dB PLUS 990e 2-way speakers (Canadian brand)
>>>		- Power Handling max. 100w rms
>>>		- min. power 10w rms
>>>		- efficiency 98dB(avg. room)
>>		- freq. response 30H - 22kHz

Really nebulous ratings aren't they?   What's an average room.
And is the 98 db measured at their maximum power - I'd guess
that since they are playing so fast an loose as it is.

If you figure that 98db at 100w that brings the speakers into
the 85-90db for 1w @ 1 meter which is the normal way to rate
them.

>>There are a couple of anomolies with the specification. First, the sensitivity
>>is rated at "98 dB(avg. room)". If that's to be believed, it suggests that with
>>a 100 watt RMS power rating, the speaker is capable of producing 118 dB of
>>acoustical output. I think that you will find that this is far from the case.
>>118 dB is pretty godamm loud. A sensitivity of 98 dB directly translates into
>>an efficiency of 10%, damn near impossibly to achieve with direct-radiator (ie
>>normal-looking boxes and drivers) systems. 

Gee - my box looks normal, but big.   One 15" woofer, two ports on the
box, mid-range mounted on top of the box and the tweeter on top of
that.  Rated at 200w, but the tweeter is only good for 50w.   I don't
want to be within a block of it if it ever got near its maximum !

I get 103db with 1 watt at 1 meter.  But these are studio recording
monitors.   There are very few manufacturers that make efficient
speakers.   Off the top of my head I think of Klipsh and Cerwin-Vega
for two.   Mine are Fostex - big things - ugly - and 170 pounds each
(That is how much they weigh, not how much they cost - if Shane is
reading this:-) ).

>>sepcifications really mean -3 dB @ 30 Hz, and a sensitivity of 98 dB measured
>>1 meter from the loudspeaker with an input of 1 watt (equivalent to 2.83V if
>>it's an 8 ohm system).

But they didn't specify anything.  This really sounds like one of the
sleaze type specs.    Without specifying exactly I'd ignore tehir
specs.

>So, how fast and loose do manufacturers play with specs like this?  Are
>there tests out there that actually give the results given?

As far as they can get by with.    I remember when the power amp
ratings were skewed so badly that the FTC finally regulated the ads.

A reputable mfr would rate a stereo amp at 20/w/channel.   Then someone
less reputable would call it a 40 watt amp.  Then the next would
advertise the same power as an 80 watt music power, and the next would
call it 160 watts peak music power.

And the consumer would get raped as he would think the 160 advertised
amp was more powerful than one with two channels at 30/w channel.


-- 
Bill Vermillion - bill@bilver.oau.org  bill.vermillion@oau.org
                - bill@bilver.uucp 
                - ..!{peora|ge-dab|tous|tarpit}!bilver!bill

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