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Old 25th October 2002, 06:54 AM   #1
JDeV is offline JDeV  South Africa
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Question Speaker specs.

I am new to audio and hi-fi stuff but very interested. Can somebody please xplaine to me what the following stuff mean that is written on my speaker, and what must I look for on a speaker that will tell me if it is a good speaker or a bad speaker.
I got a set of Monitor Audio Silver3i speakers, with the following specs:
Sensitivity 88dB
Max SPL / Pair: 107dB
Power 100W RMS @ 8ohms

Please xplain.
Thanx alot
JDeV
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Old 25th October 2002, 12:59 PM   #2
claudio is offline claudio  Italy
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Hi,
just looking at spec is not sufficient to tell you the sound quality of a speaker or any audio equipment.
Talking of speakers, the spec gives you an idea of what ampli will better matchs that particular speaker, but listening to the various combinations is a must.
For example, your speaker sensitivity is 88 db, so you will not try to match it with a low power ampli, like a single ended tube amp.

sensitivity/efficiency :
A loudspeaker specification, usually given as the amount of output in dB for an amplifier output of 1w measured at 1m. Standard loudspeaker sensitivities range from 87dB to 90dB. High-efficiency designs, such as are required with low-powered triode amps, usually offer >93dB while horn-loaded speakers can achieve efficiencies >100dB. Double the amplifier power is required to achieve the same output from a 87dB-rated speaker as from a 90dB rated one. Shopping for higher-efficiency speakers minimizes the amplifier power required to drive them. This can save both money and improve the performance. Lower-powered amps from the same manufacturer often sound more refined than their more muscular siblings

For a glossary, take a look at this address: http://www.goodsound.com/glossary/0200.htm

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Old 25th October 2002, 06:36 PM   #3
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Although Mr Claudio is correct in all he says, sensitivity is usually quoted as 1 watt at 1m but sometimes that is replaced with 2.83v at 1m in the specs. This gives 1w into 8ohms but 2w into 4ohms so is used by some companies to artificially inflate their efficiency rating. Having typed that, Monitor Audio is a very respectable company and almost certainly wouldn't try this trick.

Also, doubling power into a speaker gives an extra 3dB of output but you need to pump in ten times the power to double the perceived volume.

Nice one,
David
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Old 26th October 2002, 12:46 AM   #4
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Quote:
Originally posted by daatkins
....sensitivity is usually quoted as 1 watt at 1m but sometimes that is replaced with 2.83v at 1m in the specs. This gives 1w into 8ohms but 2w into 4ohms so is used by some companies to artificially inflate their efficiency rating.
Hallelujah!! People are catching on!!

I once spent several minutes messaging to a cyber-friend with a college degree in Economics about the sensitivity rating. He finally "got it"-I think.

The sad part is, even good companies have begun to measure this way, because sleazy companies kind of forced them into it. Peerless, for instance, rates it's 4 ohm drivers by 2.83 volts.

It's bad enough that a 4 ohm driver will be unfairly rated 3 dB higher than it's 8 ohm counterpart by this method. Worse, as daatkins points out, now that we have 2 ohm drivers in the picture, it's getting ridiculous. A 2 ohm driver will be unfairly rated 6 dB higher if measured by the 2.83 volt method.
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Old 26th October 2002, 03:17 AM   #5
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Given that amps are constant voltage devices, what is wrong with the 2.83v method of rating?
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Old 26th October 2002, 05:24 AM   #6
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Quote:
Originally posted by Bill Fitzpatrick
Given that amps are constant voltage devices, what is wrong with the 2.83v method of rating?
It is misleading -- a useful spec should allow you to compare directly. People often just compare numbers. (Take computer MHz for instance, not many bother to tell you that a 1 MHz Pentium 3 is about the same as a 1.5 MHz Pentium 4 or a 600 MHz PowerPC G4)

Even if it is specified the reader has to do the conversion as KelticWizard has illustrated. Most won't even know it needs doing and even those that do will sometimes not.

And this is particularily a problem for tube amp users who have the same voltage output into the load (assuming the correct taps are used) and sometimes less (if the wrong taps are used).

dave
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Old 26th October 2002, 05:32 AM   #7
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I guess there isnt a serious problem...
Power amps are almost always described by their Watt rating and the 1W speaker rating fits well with this. My guess is that most people dont realize an amplifier has "volts in it"
On a related note the consumer electronics store down the street sells most of its amps with a power rating based on a 6-OHM load... Im just waiting for someone to buy one of their 100Wx5 amps and try to use it on a 88dBW 2-OHM sub. It wont even drown out my laughter
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Old 26th October 2002, 06:38 PM   #8
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The big problem is not that a 4 Ohm-speaker has a higher sensitivity than at 8Ohm dito for the same voltage but that the producers use different ways of specifying the speakers. Some say W and som some say V. What I think should be used is V because the impedance isn't constant but the voltage usually is.

SPL @ distance (usually 1m) @ voltage (usually 2.83V) is the best way by my opinion. Then we users could calculate the rest...

but that's just my opinion...
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Old 27th October 2002, 04:44 AM   #9
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A person buys a subwoofer plate amp rated at 100 watts rms into 4 ohms. He builds a subwoofer with a 4 ohm speaker rated at 91 dB @ 2.83 volts/1 Meter.

He quite naturally assumes he will be able to drive the speaker to an SPL of 111 dB. That is what the math would indicate.

Instead, it will top out at 108 dB.

Okay, that won't be enough to pronounce the project a failure, but still. If you have these ratings, they should be comparable.

And with 2 ohm speakers coming into vogue, the top would be 105 dB instead of 111 dB. That would certainly cause concern, I would think.
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Old 27th October 2002, 06:46 AM   #10
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Quote:
Originally posted by kelticwizard
A person buys a subwoofer plate amp rated at 100 watts rms into 4 ohms. He builds a subwoofer with a 4 ohm speaker rated at 91 dB @ 2.83 volts/1 Meter.

He quite naturally assumes he will be able to drive the speaker to an SPL of 111 dB. That is what the math would indicate.
Why would he assume that? And how could the math indicate it? Especially since you did in fact a correct calculation of the value!
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