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

[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.

Regards
-- 
Don Cox
doncox@xxxxxxxxxxxxxx