Axiom Home Page Forums General Discussion Home Theater Is my hk powerful enough

Hi
I have been looking at the m80-500 system but dont realy know if my amp has enough punch to drive it.
I have a Harmon Kardon 445.
There suposed to handle 4 ohm but would it realy heat up? and would the speakers be very loud? mind you i dont need them to blow me out of the house though.
Any advice would be a great help.
Thanks.

All the speakers in the EP80/500 set are very senstitive so you need only 1w of power to obtain 95db (loud) at 3 feet.
So, depending on how far you will seated and the size of your room, your power requirements are going to change drammatically (you need twice the power to gain 3db).

For anyone to answer this question, you would need to provide the following answers:
1) Size of room
2) Seating position

You should not have any problems with the HK's driving m80's. Room size would help, as well as listening taste.

The sensitivity of the M80s are 95db @ 1 watt @ 1 meter but 1 watt @ 4 ohm is only 2V not 2.83. We have never have got a clear answer as to what the measurement is into the 4 ohm M80s.

Sorry, Rick. I don't understand what you mean.

They say one watt at one meter. If it is the standard 2.83v at 4 ohm it is not one watt. If they use one watt @ 4 ohm then it would be 2v. So how do they measure it, with 2v @ 4 ohm equaling 1 watt or the standard 2.83V which would be 2 watts?

I am taking Axiom on their printed specs and going with, it is 1 watt - 2V

Titan, welcome. It's highly probable that your 445 would drive the M80s as loudly as you want(or would be safe for your hearing), but just about any amplifier's maximum power capability can be exceeded if someone would use an extremely loud average listening level with program material that has a very wide dynamic range.

Rick, your discussion of the difference between the 1 watt and 2.83 volt measuring standards when a 4ohm load is involved is correct, of course, but as Jason mentioned I've assumed that since Axiom specifically said 1 watt that they meant that rather than 2.83 volts. You're right that the possible difference has apparently never been discussed.

I think that we need a "Sticky" with all the compatible m80/4 ohm receivers, so this question stops coming up and so that we don't have to search all the time for it.

It can be measured either way as long as the person making the measurement adjusts the sensitivity by 3db for the voltage (wattage) difference.

Rick,

I too understand that Axiom used a 1W signal.

I wonder if Axiom measures the M80s different than Soundstage. They (Soundstage) measured the M80s sensitivity: 89.5dB (averaged 300Hz-3kHz, 2.83V/1m)

It's the cables

Axiom specifies 91 in anechoic chamber, which is pretty close to the inferred 90db/1m of a 2m test with the 2001 version of M80 in an anechoic chamber.

http://www.soundstagemagazine.com/measurements/axiom_m80ti/

Soundstage used the standard 2.83V not 2v for their measurement of 90db @ 1m. If they were using 2v they would have measured 87db.

A watt is a measure of energy/second. A watt is a watt regardless of pressure of transmission (tension expressed in volts) or difficulty of transmission (resistance, expressed in Ohms). The amount of SPL is directly proportional to the amount of energy received by the speaker and its efficiency. The SPL level is SOLELY a function of transformed energy. Hence the measure of amplifier power in watts.

But 2.83V @ 4ohm is 2 watts not 1, 2v @ 4 ohm is equal to 1 watt. If Axiom states 1watt @ 1 meter are they using 2v to acomplish the 1 watt? There seems to be a big difference in they way the two came up with the rating.

No because 1 watt is 1 watt and the rating is 1 watt/ 1 meter REGARDLESS OF ANY OTHER CONSIDERATIONS.

Then how does Soundstage get arouund the same rating using 2.83V.

Because the rating is based on watts NOT VOLTS. You can measure sensitivity using a 1000Watts if you wish. Or even half a watt (sorry Tex, couldn't resist). All you have to do is translate the result, like they are already doing with 2 meters / 1 meter and adding 6db, to bring the result back to 1 WATT / 1 METER. Really hope this is clear now.

I think we need some equations here.

Brownies + chocolate frosting= happy stomach.

For all interested, see section 5.

http://www.hps4000.com/pages/digital/powering_up_for_digital.pdf

Ken, lets try the form of Ohm's Law relating power to voltage and resistance: P=V(squared)/R. So, 1(watt)=2.83 volts(squared)/8ohms. Any number of watts or volts can be used in the measurement as long as the result is stated in terms of the usual standard, equivalent to 1 watt.

ohms law is one of the very few things I actually remembered from my electric circuits class. Still haven't figured out why that class is required for civil engineers...?

On the fundamentals of engineering exam I could answer all of the ohms law problems and converting resistors in parralel and series into single eq. resistor easily

Anything that said AC and had a sine wave I guessed c!

Why did I have to take mechanics and dynamics (which I loved by the way)?

Rick, my cheap and dirty way of measuring sensitivity here at home is to inject a 50Hz signal into the M80 with a 2 Volt average value and then measure the SPL. Why 2 Volts? Because at 50Hz, the M80s impedance is bang on 4 Ohms according to the charts. 2V across 4 Ohms yields a power of 1 watt. (To verify that this is indeed the impedance I could measure the current but I haven't done that.)

Now as I'm writing this I'm thinking that perhaps 50Hz is not a great value for rooms like ours. I should probably use 500Hz or above to get away from room effects.

Anyway, an important point here is that Soundstage averaged the SPL from 300Hz to 3KHz. What frequencies did Axiom use? Maybe Axiom went down to 80Hz which is approximately the limit of anechoic chambers. Axiom did their tests anechoically; did Soundstage? Or did they do them semi-anechoically?

Right, got it.

I always thought the tests the were usually done with a 1khz signal?

Ok, though I didn't have a lot of coffee this moring I think the article from EFalardeau and Johns explanation clears things up. It isn't a matter of the numbers used as long as the end result equals 1w @ 1m and this can be done in a number of fashions.

Exactly. Coffee sounds like a good idea, actually. I think mine is ready! (BTW, it is now officially winter in Montreal; we are having our first snow storm... too bad I am running out of excuse to stay home with my speakers... kidding! I still have plenty of excuses).