Enough power for my speakers?

[rmihai]

Hi all,

I have a pair of Ellis speakers that are using a Dennis Murphy crossover and are rated 83db sensitivity and 8 ohms impedance , but can go as low as 6.3 ohms.

Is a 2 way design using Seas Excel W18.

My question:

Would you consider 30W Class A SS enough to power these speakers? (I have in mind a Pass Aleph 30).

I am NOT listening loud: around an average of 85db @ 7' (2m) distance.

[454Casull]

83dB - 6dB (2m distance) = 77dB

30W = 14.77dB

77+14.77 = 91.77dB

So if you want only 6.8dB of headroom, that's fine.

[rmihai]

Thank you very much.

Hmm - I don't really know if 6.8db of headroom will be enough. Can you give me a clue? This headroom is the same with the difference between peaks and average levels?

[forr]

HI,
Sensitivity 83 dB for 1 W should be in an anechoic room in a 4 Pi environment.
In real listening, there is "room gain". So for 1 W of amp output, you should get about the same level as in the anechoic room.

You say you do not listen loud with an average level of 85 dB.
What do yo mean ?
An average of 85 dB is quite loud and means peaks of 15-20 dB higher than this.
Or do you mean the average listening peaks ? In this cas, your average listening is about 70 dB (15 dB lower) which is a domestic standard.

I am trying to collect a many data as possible about listening levels of people at home in order to correctly dimension amp and loudpseaker needs.

~~~~~~~ Forr

§§§

[rmihai]

Forr,

thank you very much!!!

I am listening usualy @ levels that will reach MAXIMUM of 85-90db.

I would also expect ot get another 10db gain from the pre-amplifier (Pass X2.2).

Does this mean 30W will do it?

[mondaycurse]

it depends how much headroom you really want and when amp THD sets in. I think it wouldn't hurt to get a 60W amp, just to make sure you have around 10dB of headroom.
30 watts is enough if you don't mind the slightest bid more distortion, but with watts cheap these days, you might just want that extra headroom

[rjb]

Just a minor point.

The power output of the amp is not the same as gain.

So the gain of your preamp is not a factor with regard to output power, provided it is sufficient to fully drive the amplifier.

Typically most amp/preamp systems have more than enough gain to fully drive the amplifier, so you can ignore this.

As far as power output is concerned, it is difficult to give you a definite answer. The easy answer is to say buy as high a powered amp as you can afford.

In practical terms, I have found that a good (repeat good) 25 watt ss amp is sufficent in terms of shear volume to drive even rather inefficient 3-way transmission line speakers for most people. Even lower powered amps such as a JLH class A can be enough for many people.

However some SS amps, unlike valves, can react badly close to maximum power with some loads, and sound "strained". Some speakers can be particularly difficult through parts of their range. For this reason I would generally recommend a higher power ss amp, say 50 watts minimum or even higher, (assuming I don't know the amp and loudspeakers from personal experience), against say a 20 watt valve with its more gentle overload characteristics and bettter tolerance to high C or low R speaker loads.

If you read this forum, you will see some listeners are only using 2 watt SET amps even with speakers (generally full-range) of only modest efficiency. Others want powers in ecess of 500 watts.So it is not only a matter of desired listening level, but also involves the type of amp and the type of speaker load, and also the room, (hard surfaces or absorbent).

This probably does not help you, so I suggest you contact other owners of the amp you are considering, and see what their experiences are taking into account the speakers they are using.

[rmihai]

Thank you very much all of you for your answers. Definitely helped me beter understand.

I measured again and again the SPL.

The results: most of the time I listen between AVERAGES of 60-65db. In special cases when I really enjoyed the music I pump it up to 68db.

Allowing for 25db headroom (which should be more then enough), that means I will need a maximum of 93db.

From my calculations, a 30W amplifier will give me 94.3db @ the listening positions and that is just a bit over my target of 93db.

If I am not wrong, that means a 30W amplifier will work for my listening levels.

[forr]

Hi RMIHAI,

Some more calculations :

83 dB/m 1 W
86 dB 2 W
89 dB 4 W
92 dB 8 W
95 dB 16 W
98 dB 32 W

95 dB SPL is a maximum level for a 15th row at a classical concert.

With your listening level of 70 dB or even less, you have at least a dynamic range of +/- 25 dB :
70 dB + 25 dB = 95 dB, your 30 W amplifier is far from clipping.
70 dB - 25 dB = 45 dB, your room should have a ambient noise lower than that.

Dynamic range of 50 dB is rare (piano recording)
The average dynamic range is about 30 dB (+/- 15 dB) and a good one is 40 dB (+/- 20 dB).

In France some good FM stations can play music at such a dynamic range of 40 dB when direct broadcasting. The signal to noise of FM broacast is around 60 dB.

A funny remark : with an average listening level of 70 dB and a sensitivity of 83 dB/1W/1m, we can ealisy know the average electric power delivered to your stereo speakers :

83 dB 1 W
80 dB 0.5W
77 dB 0.25W
74 dB 0.125 W
71 dB 0.0625W
70 dB 0.05 W,

this is only 50 mW most of the time !

~~~~~~~~ Forr

§§§

[454Casull]

forr, I doubt the room boosts the SPL by 6dB all across the entire frequency range.