Will F4 have enough power in this system?

Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.
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!
 
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
 
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.
 
Sorry I dont think so

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

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.:devilr: :devilr: :devilr:
 
Re: Re: Will F4 have enough power in this system?

Nelson Pass said:


I think so - it would be for me.

:cool:

Thanks Mr. Pass!:D The F4 magic is if power is the only drawback you just get a second F4!

A small-value polarized cap will be series-soldered in the RCA plug at the load-end of the preamp output interconnnect. Intent is for a 1st-order high-pass 80-Hz xo for the main speakers (after the powered subs arrive). I'm open to better alternatives, less costly than buying an expensive active xo.
 
Nelson (or anyone else)
My speakers are rated 89 dB. But just for fun...

From S. Ebaen's wonderful 6moons/F4 review:
"As you drop below 87dB speaker sensitivity, you will want to consider 100-watt balanced monoblock operation, with a preamp capable of swinging 14 volts per balanced output and having a gain of 20dB+."

My preamp specs:
"Gain 21 dB (11x)...Maximum output on all outputs is 10 Volts RMS"

The following question has been put to the preamp designer. Is it correct that my preamp spec above probably means its balanced outputs have a maximum output of 10V positive/10V negative?

Is it correct that 10.5V maximum preamp output = 3 dB less gain than 14V?

The way I understand the relationship between gain & maximum voltage is...the preamp will add up to a maximum of 20 dB gain to the source. Exception: when any combination of source + preamp may otherwise combine for an output of __ V (the preamp's maximum output, or 10 V in my case), the preamp will have reached its maxium current capacity. In this case gain may be limited to some figure below 20 dB.

Kind of like when a power amp runs out of current. In the case of a power amp, it clips. In the case of the preamp above, will it also clip?

Inquiring minds want to know.
 
Status
This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.