Will F4 have enough power in this system?

[ro9397]

Room description: (H x W x D) 7.6 x 16.5 x 25.6, 3200cf, dedicated/treated but not over damped, symmetrical except for a small opening behind & to left of sweet spot. Rear of room slightly damped; only furniture is a large symmetrical sectional sofa. Components are centered on front wall (behind speakers) but hidden by Room Tunes.

Speaker: French ASA Pro Monitors, Dynaudio 7” & Esotec tweeter, rated 89 dB, seems like a moderate amplifier load, 1st-order xo

Speaker/listener relationship: Per George Cardas recommendations, standard equidistant triangle: 7’ between speakers/7’ speakers to listener in sweet spot

Gain: A state of the art preamp is employed w/ plenty of reserve gain.

A pair of powered subs are coming that will also serve as speaker stands; at that time the main speakers will be 1st-order high-pass crossed at about 90 Hz, minimizing main amp bass duty. Also ear level will be just below mid-point between 7” mid-bass & tweeter.

Wide-range large-scale symphonic work & rock will be played hopefully at or near live levels.

Will the F4 have enough power in reader's opinion?

Many thanks!

[h_a]

Since you didn't get any reply I give it a try:

First, you don't state minimum impedance of your speakers, so I assume 4 Ohms. The F4 delivers 50W at 4 Ohms.

89dB at 1W in 1m distance is not much, anyway if you're interested at live levels, let's assume 130dB in 1m. Your ears already ache a bit at that level, but you're sitting a bit away anyway. Sound pressure drops quadratically with distance, so choose your flavuor.

130dB are 41dB above 89dB, for every 6dB you need to double the power, so power multiplies by approx 2^7, which is about 128 Watts.

If you build the F4 as balanced monoblock, you get 100 W at 8 Ohms, maybe 200W at 4 Ohms.

So if I'm not completely mistaken, you probably can build balanced monoblocks and restrict yourself to 124dB and get what you want sitting in max 2m distance from the speakers.

However I don't have particular knowledge of the F4 and most probably I did severe mistakes in my estimation, so please don't take them as a definite answer.

Maybe somebody shows up and points my mistakes out, would be highly appreciated!

All the best, Hannes

[ssmith]

Originally posted by h_a
... and most probably I did severe mistakes in my estimation, so please don't take them as a definite answer.

Looks fine -- by the way, I really like
this online SPL calculator... saves doing all the maths...

[h_a]

Whoa, I get 116dB - that's way off.

If this calculator - nice toy by the way - is any right, I guess you can forget what you want, dear ro9397.

@ssmith: thanks for the link! Amazing little calculator ;-)

Cheers, Hannes

[ro9397]

I'm not too surprised w/ the replies; I knew one amp was too easy!

I've read that, for reasons forgotten, you don't actually net 3 dB per power doubling.

Yes speakers are rated 8-Ohm, minimum impedance is unknown but they don't seem to be too terrrible of a load, estimate about 4-Ohms minimum.

After getting my ears blown out at a live concert a few weeks ago (forgot to bring ear plugs) I will amend the SPL spec down at least several dB.

[Dr. ODD]

Sorry I dont think so

Nobody needs 130db at his listening room. Also the Speakers would explode at that level.


I calculate something around 102-103 db which is not bad, but I think there are different opinniens what normal listening levels are.

If it is at night, and you are living in a house whith many families, 100 db is pretty enough to get angry neigbours.

[h_a]

Nobody needs 130db at his listening room.

Hehe, he can't stand it any louder anyway ;-))

Cheers, Hannes

[MRupp]

for every 6dB you need to double the power,

Nope, for every 3dB of SPL you need to double the power ! Plus 6dB doubles the voltage, hence doubles the current also, hence .....

[h_a]

Ah I see! I've mixed things up. Thanks a lot for clarifying!

That would make then about 16kW for 130dB (89dB speakers). I do see now the point of high efficiency speakers in an PA-environment, ahem.

Cheers, Hannes

[Nelson Pass]

Originally posted by ro9397
Will the F4 have enough power in reader's opinion?

I think so - it would be for me.