Charlie:

That's right.

Let's say you have a preamp/power amp chain that puts out, say 5 millivolts of noise constantly. Hang a direct radiator speaker on it that has a 90db efficiency for 1 watt input. It will produce that 5 millivolts of noise from upstream at a sound pressure level of "X". Hang a horn that has an efficiency of 106db for that same watt on it, and it will reproduce that same 5 millivolts of noise a whopping 16db louder.

This also explains why horns sound better with tube power amps. Any crossover distortion, or any other nasties such as the effect of large amounts of negative feedback from the power amp get amplified much more with horns. Tube amps run much 'richer' in class A/B than solid state ones, and also have much less global negative feedback. For my tweeter horns (1,200Hz and above) I've even gone the route of class "A" triode power; no crossover distrotion, and no negative feedback. Of course, you could also use a class "A" solid state power amp, but those are very, very difficult to come by.

[This message has been edited by soundhound (edited November 25, 2002).]

sh: You're completely right with the 'more high frequencies' with horns because of the directivity feature. (Apologies - had let that slip by). So the showing up of hiss could indeed be signicantly more with directional speakers.

As for your other 'horn' comments: 'exaggerated' horns can be pretty 'bad' - and most should be relegated to PA - a quality tweeter with a 'small' exponential horn built as an extension of the tweeter's own dome can produce very good - and high fidelity - sound.

You're quite right, but don't get stuck on the typical 'bias' against horns! As in all things in life, it is the _implementation_ that is the key. I've heard some pretty gastly direct radiators too. Compression drivers have some definate advantages over direct radiators. One obvious one over a horn in front of a cone or dome speaker is the phase cancellation that occurs due to the differing path lengths from the edges of the cone relative to the center of the cone as the sound travels out the mouth of the horn. Compression drivers get around this problem. I suggest you listen to a really well set up horn system before making sweeping judgements!



[This message has been edited by soundhound (edited November 25, 2002).]

PS

When I started to 'conflict' with the horn comments here - I was reacting to the 'efficiency' aspect of horns and got myself waylaid there.

I had forgotten about the directivity.

But maybe there was some good in my getting 'off-track' - it seems like there were more than a few here that thought of the efficiency characteristic of horns to be the reason for 'hiss sensitivity' - it was (is) instead the increased higher frequency response because of the wider dispersion due to the higher directivity-feature of 'horns.'

The use of the word 'directivity' in this connection is itself a bit of a paradox - because 'directivity' is the reason 'normal' speaker elements disperse high frequencies 'badly.' A horn that is exponentially curved (correctly) to allow frequencies to be widely dispersed at many angles is what is behind this - the horn is 'widening' the spectrum which would normally be restricted by the principle of directivity which says that the higher the frequency the more it will only be directed in a straight line from its point of emission.

Back to Fletcher and Munson's for a bite of steak (sans ketchup or 'steak sauce')!

Horns do disperse all of their energy in a controlled manner 'forward' more than a direct radiator. Direct radiators direct more energy 'into the room' before it hits your ears. Horns are the opposite, they direct more energy to your ears before it is dispersed into the room. This is a good argument in favor of a fully horn-loaded system, top to bottom; the dispersion pattern stays the same throughout the frequency spectrum. Horns are still subject to the 'beaming' problem as frequency increases, but less so than a direct radiator.

Horns are sort of like wearing headphones; since the sound is more direct-to-the-ear, more details can be heard. This is exactly why they make good monitor speakers.

[This message has been edited by soundhound (edited November 25, 2002).]

"Horns are sort of like wearing headphones; since the sound is more direct-to-the-ear, more details can be heard. This is
exactly why they make good monitor speakers."

Fine - but always remember as per Prof. Hayakawa -- horn 1 is not necessarily horn 2.

All horns are NOT good - some companies will use a 'horn' just as a moniker - often bringing what SHOULD be heard as catastrophic results. A good direct radiator can be MANY times more accurate (hi-fi) than a mediocre horn design.

[This message has been edited by John Padova (edited November 25, 2002).]

1) And the converse is ALSO true that a good horn is better than a mediocre direct radiator!

2) I have VERY good horns!

3) You don't seem to have much DIRECT experience with good horns, do you!!

"Horns are the opposite, they direct more energy to your ears before it
is dispersed into the room"

I have some doubts if this is indeed what is happening.

If you are positioned on direct axis from the emitting source the energy will just simply come directly to your ear - and reflections from walls, etc. will reach you later.

If you are off-axis by some 30-45 degrees - frequencies from a direct radiator will be reduced by some 40-50% (ballpark) - if a horn is used the reduction will be some 10-15% (ballpark) -- because the horn 'shape' has allowed the frequencies to be emitted from an angled surface - they will still obey the maximum energy at a 90 degree angle to the emitter - but the emitting surface will have moved away from the zero point because of the horn effect.

I believe it is this geometry working with the 90 degree principle that allows for the wider dispersion and is completely independent of sounds coming later from those waves that did not reach your ear directly.

That does NOT mean that the acoustics of the room and subsequent reflections and absorptions are not relevant to the quality of sound but the first and primary influence (assuming that the room acoustics are not TOTALLY horrific) is going to be a function of higher frequencies being emitted 'off-angle' thanks to a good horn.

[This message has been edited by John Padova (edited November 25, 2002).]

Horns do not direct energy 'off axis' as readily as a direct radiator, more is directed in the direction of the horn. The room absorption happens at a greater distance from a horn than for a direct radiator. That's why they are used in PA applications. Simply cupping your hands around your mouth will prove this!

[This message has been edited by soundhound (edited November 25, 2002).]

"You don't seem to have much DIRECT experience with good horns, do you!!"

++

VERY much with one we designed ourselves - some very BAD experience with others that were commercially available for mortal budgets

When using a horn adapted for a direct radiator it is INCREDIBLY critical to create an almost perfect continuum from the dome of the radiator to the surface of the horn. Failing to do so would seem to create a very nasty problem.

Anyhow - we should return this forum topic to those 'debating' how many millimeters away from a speaker will result in hiss from an Outlaw 950.

I, myself, am very rarely closer than 6 feet to a speaker so i guess from what i read here that I would NEVER have a problem with a 950 except to wonder if I indeed had turned it off after the movie was over