Re: [ARSCLIST] Fwd: [ARSCLIST] Dynamic-frequency Range

["Steven C. Barr(x)" <stevenc@xxxxxxxxxxxxxx>]

----- Original Message ----- 
From: "Don Cox" <doncox@xxxxxxxxxxxxxx>
> On 25/10/06, Steven C. Barr(x) wrote:
> > ----- Original Message ----- 
> > From: "Don Cox" <doncox@xxxxxxxxxxxxxx>
> >> On 21/10/06, Steven C. Barr(x) wrote:
> >> 
> >> Well, I've always figured they (over)emphasized the bass simply to
> >> make sure that electric records sounded "better" than their acoustic
> >> predecessors, which had virtually no audible bass (perhaps if Edison
> >> had ever perfected his ultra-long recording horn...?).
> >> 
> >> I don't think extra length would help so much as a bigger diameter
> >> entrance, and as I said before a better shape, more like the ears of
> >> a bat-eared fox.
> >> 
> >> A straight-sided cone is not right.
> >> 
> > Good point. Victor's "Orthophonic" horn did have a calculated taper
> > to improve frequency response. However, as I recall one of the
> > figures on which that was based was the size of the "mouth"...
> > which is limited for reproducing horns, and in a practical
> > sense also limited by recording horns. I suspect that Edison
> > (as well as his associates) probably deduced wrongly that bass
> > response could be improved by lengthening the horn (or volume?)
> > but weren't aware that a corresponding increase in the mouth
> > dimension was also needed.
> 
> In the case of very low frequencies, it is probably better to forget
> about wavelengths and think in terms of a local variation in air
> pressure. To gather enough energy from a pressure increase to force a
> diaphragm (and stylus) to move, the more molecules you can enlist the
> better. 
> 
> Hence a large opening is desirable. I have doubts about an great increase in
> length being necessary.
> 
> Remember that quite low frequencies do move the human ear drum. We don't
> have to have enormous ears. The problem is that a wax cutter needs more
> energy coming in than the ear drum. It has more work to do.
> 
> > 
> > I would suppose that (at least in theory) if one had a few
> > hundred contiguous square miles of room and a vast amount
> > of material, it would be possible to construct a horn which
> > could pick up and record acoustically frequencies down to 15 Hz...
> > but a similarly-sized playing horn might be required to hear
> > the results?!
> 
> At the other end, it again depends on how many molecules you can shift.
> So in an acoustic player, where the diaphragm movement is limited, a big
> horn containing lots of air helps. Loudspeakers can manage with smaller
> sizes because they have a longer throw (especially the recently designed
> units with new magnet materials).
> 
> 
> Does this make sense? It is always hard to see what is really happening
> in real world physics.
> 
Yes...except for the fact that when horns become very large, the
wavelengths (and halves and quarters) become involved, in the 
sense of having resonances as well as cancellations and
reinforcements! The nominal speed of sound in "ordinary" air
is 1100 meters/second (IIRC)so that a 100 Hz sound wave has
a wavelength of 11 meters, or about 35 feet. I have no idea 
how dimensions of 1, 1/2 or 1/4 wavelength for horns would
affect their use in reproduction or recording, but I'm sure
it would...?

Steven C. Barr