Speaker debate: I stirred the mud first so I'll stir it some more. Slosh!
Typically speakers with large magnets are more efficient, i.e. possess
greater sensitivity, than ones with small magnets. This is contrary to one
message posted earlier that stated a speaker with a small magnet required
less power. A properly "tuned" enclosure will also enhance the efficiency
as well as smooth out the frequency response. While a speaker having a
resonance at say 700 Hz will sound great on CW, it will make the voice range
sound "honky". To the contrary. HiFi speakers, those having extended
frequency response typically beyond normal hearing limits, (most easily go
out to 30 to 40 KHz, however "ears" don't) are found to be fatiguing with
extended listening periods as used in communications applications. The high
frequency hiss, either from the electronics or band noise or both, tends to
mask lower frequency sounds and thus requires the "brain filter" to work
excessively to eliminate the unwanted noise. It is natural that higher
frequency sounds do mask the lower frequency sounds of the same level of
acoustic energy. It's just the way the ears work.
So where does all of this lead? A speaker with a high efficiency and
reasonable sensitivity can be driven to a good acoustic power level,
cleanly, with as little as 1 watt of audio. A smooth frequency response
down to say 150 to 200 Hz with a reasonable roll off below eliminates the
need for higher driving power plus gets rid of random thumps, humm and other
artifacts that are of little interest with voice or CW communications. At
the same time, having the upper end frequency response extending only to 5
or 6 KHz with a roll off of 6 to 8dB/octave will sound quite nice.
Finally, regarding an enclosure, metal cabinets rattle! Don't take it for
granted, thin plastic boxes rattle too. However, a structurally sound
fiberglass or polymer molded enclosure is light weight, tough, doesn't
rattle, and can be made to sound quite nice. I know, the EV's that I
installed in our church sound great. They are molded polymer boxes too.
73
Bob K4TAX
----- Original Message -----
From: "Bill Ames" <bames@aob.com>
To: <tentec@contesting.com>
Sent: Monday, January 21, 2002 12:30 PM
Subject: RE: [TenTec] Ten-Tec External Speaker
> I think that TT will provide a speaker that meets the interface
requirements
> for the Jupiter but I am concerned that it will not be as good as it could
> be because, I believe, you get better sound from speakers that are less
> efficient and require some power to get the best results. Since the J has
> limited audio output power it can not drive these less efficient speakers.
I
> do not see them adding any electronics to the new speakers, so, I am
> prepared to be somewhat disappointed...
>
> Bill Ames
> KB1LG
>
> -----Original Message-----
> From: tentec-admin@contesting.com [mailto:tentec-admin@contesting.com]On
> Behalf Of Bob KIrkland
> Sent: Monday, January 21, 2002 10:30 AM
> To: tentec@contesting.com
> Subject: [TenTec] Ten-Tec External Speaker
>
>
> The operations manual for the Jupiter specifies a 4 Ohm speaker should be
> used for external sound. As you know the audio output comes from a
> transistor amplifier. In this type of audio amplifier it is important to
> match the speaker impedance to the output impedance. If it is not
> matched,inefficiency and distortion can occur especially at high volume
> levels, and the amp has only 1 watt to begin with.
> Bob, w5pvr@gower.net
>
>
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