[Hallicrafters] RE: PM-23 speaker specs II

[Ken Kaplan]

> Whoa there Ken.  I may be just a radio guy, but what do all those
> acronyms mean.  Care to spell out the whole word?
>
> K2WH

Sorry. You are right - I should have defined the terms.

Fs is the free air resonant frequency of the speaker (i.e. not in an enclosure or baffle 
board).

f1 and f2 are the frequencies above and below resonance where the impedance 
equals a specially calculated value (function of resonant impedance and DC 
resistance).

Qms is the mechanical Q of the speaker
Qes is the electrical Q of the speaker
Qts is total Q
Re is the DC resistance of the voice coil
Le is the inductance of the voice coil
Vas is the air volume whose equivalent compliance for the speaker is equal to the 
speakers compliance.

So, those number again for the PM-23 (including Vas) are:

Fs = 55 Hz
f1 = 49 Hz
f2 = 65 Hz
Qms = 7.37
Qes = .602
Qts = .557
Re = 3 ohms
Le = .375mH
Vas = 3.68 cu ft
Voice coil - 1"
Cone = very dry paper

Most of these specs only mean something to an audiophile (as opposed to 
audiophool) who wishes to design an optimal speaker system. It might also help if 
you are trying to find a replacement that is close as possible to the original. There are 
sources who provide these specs on speakers that they sell. It turns out that the PM-
23 box is hardly optimal but the engineering techniques were not available back then. 
Then again, we are not hooking them up to hi-fi systems anyway. Using appropriate 
audio engineering methods, one could design a speaker system optimal for 
shortwave. Most that I've seen are very compromised.

FWIW - there is a whole hobby field out there of audiophiles who enjoy designing 
and testing speaker systems much like hams who enjoy home brew. They use sound 
engineering methods to try to obtain optimum performance while keeping costs 
under control. They have something in common with we who like to align our 
receivers to a gnats ass and obtain an SWR of 1:1. I don't have to say anything 
about hams keeping costs under control, do I <g>?

Audiopools, however don't really understand the technology very well and tend to 
throw money on things to impress themselves and others of their like. Hey, I guess 
we should thank the phools as their buying power adds some good products to the 
market that we all can benefit from. I've seen plenty of the phools. I had to visit an 
opthomoligist to get my eyes fixed after they rolled up to much <g>. Seriously, being 
among audiophools is not a comfortable place for an engineer to be (probably for 
them either).

Pardon my verbosity. I could go on <g>

73 Ken kb7rgg