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new loudspeaker efficiency question


abpurdom

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Does anyone know what is the efficiency of New Advent (large) Loudspeakers? I'm trying to figure out whether to go tube amp or hybrid on a budget of $700 or so.

Any suggestions or thoughts

I answered this a few weeks ago in the AR Forum, on a question about the AR-303's sensitivity ("efficiency"). I'm not certain about the NLA's actual sens spec, but it's very likely to be in the 87-89 dB 1w/1m range, as were most sealed 'full-size' bookshelf speakers of that era.

What I said about the 3a/303 generally applies to the NLA as well. It may be of some value to you. The main things to consider are your listening preferences/habits/goals and the size of your room.

Remember also, that many people regard tube amps' more benign clipping characteristics to be a very favorable attribute, and that is one reason why it may seem as if you can 'push' a tube amp to listening levels louder than its somewhat modest power rating might suggest it capable of playing, compared to a harsher-clipping higher-powered SS amp. (Not all SS amps are harsh-clipping, however.)

My previous post:

100 watts per channel in a smallish room will drive the 303 just fine to any sane loudness level you want.

I have AR-3a’s in a small 11 x 13 room. First, consider that the sensitivity specification, as measured one meter on axis for a 1-watt input, will yield a figure of about 86dB for an AR-3a. That’s considered “inefficient.”

But 86dB is really a pretty healthy level, more than background listening. It may not be loud enough in a dealer showroom, but in your quiet listening room, you’d have to turn it down to answer the phone.

Now, you’ve got two speakers, so there’s some addition to the 86 SPL figure because of that. You are also about 8-10 feet away from the two speakers (and somewhat off axis, to boot), so there’s some reduction because of that (the inverse square law, which says that SPL reduces by -6 dB as the distance doubles). Throw in your room’s absorptive characteristics, any open walls that lead to the next room, etc, and what you’re left with is that the raw sensitivity figure for one speaker is a pretty decent number to work with as to how loud two speakers will sound from your listening position with a one-watt input. There are a LOT of variables, obviously, but 86dB for 1 watt for a pair of 3a’s from your listening chair is not a bad estimate. The 303 will be very similar, within a few dB.

Every doubling of power is another 3dB of loudness. So:

2 w = 89 dB

4 w = 92 dB

8 w = 95 dB

16 w = 98 dB

32 w = 101 dB

64 w = 104 dB

128 w = 107 dB

256 w = 110 dB

I’m not even sure how cleanly the 3a can play at or above 110dB, but any competent amp has enough juice to push the 3a or 303 to 95-100dB in a normal listening room. And that is very loud. As mentioned in previous posts, make sure you’re using a good amp that’s not apt to be driven into distortion. The 303 has a ferrofluid-cooled tweeter (the 3a did not), so the 303’s tweeter will be more tolerant of a little abuse here and there than the 3a’s tweeter.

Steve F.

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The AR303's sensitivity was measured at 84 dB per 2.83V and spec'd

at 85 dB/2.83V input which is 2W into 4 ohms, thus the 303 is

about 81dB/W per real Watts:

http://www.stereophile.com/content/acoustic-research-ar-303-loudspeaker-measurements

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=1487&view=findpost&p=57392

They require nearly four times the power indicated in your table.

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The AR303's sensitivity was measured at 84 dB per 2.83V and spec'd

at 85 dB/2.83V input which is 2W into 4 ohms, thus the 303 is

about 81dB/W per real Watts:

http://www.stereophile.com/content/acoustic-research-ar-303-loudspeaker-measurements

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=1487&view=findpost&p=57392

They require nearly four times the power indicated in your table.

I didn't have the actual 303 spec at hand when I did the calcs, but I think Julian Hirsch in the Stereo Review 3a/303 test report measured a little higher than Stereophile. No matter, what's relevant is that 'most' so-called full-sized AS bookshelf speakers of the 70's-80's are around 85-90 dB 1w/1m, and if that guess is about right for the NLA, then this info is reasonably useful. If the NLA is 82dB, then I've wasted a bit of everyone's time, I guess.

Steve F.

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