I view that several factors come to play here. Some types of external
speakers driven direct from the transceiver can require significant amounts
of power due largely to the inefficiency of the speaker system. These, what
I describe as Hi-Fi systems, are intended to be driven from amps producing a
reasonable to high levels of power, amps that have a high value of
electrical damping, driven from low source impedance, and these are
fundamentally capable of producing SPL values approaching threshold of pain.
For these one needs "lots-a-watts" of audio power.
Most small communication type speakers on the other hand are designed to be
quite efficient at converting electrical energy to acoustic energy. They
also produce a sound source that is usually quite directional. The issues I
have with radios and their internal speakers, largely they are placed in a
metal box with little to no concern about acoustic properties of the
enclosure and are limited by physical space available in the box. To make
matters worse, they point UP or DOWN and if the front of the radio is
elevated, they basically fire into the overhead shelf and thus away from the
operator. In many cases the operator will need to advance the volume to
hear adequately and overcome local room noise.....computers, power amp fans,
air condition systems and other household disturbances.
>From my perspective, I find the type of speakers and enclosures, typical of
Motorola or GE mobile communications systems, work well on most
transceivers although many of these need actual replacement of the speaker
due to age or abuse. Some of these have drivers that are 3 ohm to 4 ohm
devices which do not generally work effectively with current transceiver amp
stages. Replacing these with 8 ohm drivers corrects the concern. These are
efficient, small, and allow to be pointed basically at the operators head.
These don't require a lot of audio watts to make a lot of sound.
Just my take on things.
73
Bob, K4TAX
----- Original Message -----
From: "Rick - DJ0IP / NJ0IP" <Rick@DJ0IP.de>
To: "'Discussion of Ten-Tec Equipment'" <tentec@contesting.com>
Sent: Thursday, May 17, 2012 8:09 AM
Subject: Re: [TenTec] Top receivers
> "The point to all of this, we rarely operate our radios at audio levels
> that
> approach their distortion limits. "
>
> Bob, I will dispute that point.
> Not in the case of Ten-Tec but in the case of some other radios.
> I will send you some data showing that (off line of course).
>
> The fact is, some of the radios are REALLY bad.
>
> 73
> Rick, DJ0IP
>
> -----Original Message-----
> From: tentec-bounces@contesting.com [mailto:tentec-bounces@contesting.com]
> On Behalf Of Bob McGraw - K4TAX
> Sent: Thursday, May 17, 2012 1:37 PM
> To: Discussion of Ten-Tec Equipment
> Subject: Re: [TenTec] Top receivers
>
> The rated output/distortion topic is, by most manufactures, a means or a
> method of expressing the performance of the receiver audio system.
> There's
> always three required ingredients being (a) rated power output expressed
> in
> watts, (b) THD or THD+n usually measured at rated output power and
> expressed
> as a percentage, and (c) load impedance expressed in ohms. And of course
> one could add frequency response, but for ham receivers it's really not
> that
> important. I don't ever recall anyone publishing the audio spec using the
> value specified at the level where any degree of signal clipping takes
> place. Oooh, that would be nasty.
>
> Home audio systems typically use much higher voltage output devices as the
> same for automotive systems that incorporate switching inverters to get
> the
> 12 VDC to values ranging from 39 to 75 volts. Thus with the higher
> voltage
> systems, more voltage swing with higher current values can be developed
> across a given load and hence more power output watts. This is, as I see
> it, one reason we find higher distortion and typically 2 to 3 watts of
> audio
> output on receivers as they must operate at a nominal 12VDC and in certain
> cases with limited values of current. This also invokes the reason, to
> some
> extent, we find the transmitter IMD numbers at less than desired values,
> although they meet the current FCC required specifications for spectral
> purity.
>
> Regardless if we like it or not, we ARE dealing largely with voice
> communication systems or systems that are intended to produce audio in the
> most sensitive area of human hearing. The old Bell Telephone system
> numbers
> of 300 Hz to 3000 Hz still prevails. That's a bandwidth of 2700 Hz.
> Agreed, any added distortion to the signal does or is likely to produce
> hearing fatigue. At this point one must then add the SPL value applied
> and
> the time duration figures to determine the figure of merit with that
> regard.
>
> If one desires a higher listening level than the ham receiver audio system
> produces, being some 2 to 2.5 watts into a 3" to 5" communication
> speaker,
> then as said in an earlier post, use the Line Output fed to your favorite
> high power audio amp and speaker system. Still the distortion figures may
> not greatly improve as different designs of product detectors along with
> AGC
> characteristics will add certain distortion artifacts to the recovered
> audio.
>
> The point to all of this, we rarely operate our radios at audio levels
> that
> approach their distortion limits. Of course the basic objective is not to
> have any peak distortion hence the need for the headroom, but in practice,
> the average audio level is much less than 1 watt into 8 ohms with an
> degree
> of an efficient speaker system.
>
> 73
> Bob, K4TAX
>
>
>
>
> ----- Original Message -----
> From: "Richards" <jruing@ameritech.net>
> To: <k9yc@arrl.net>; "Discussion of Ten-Tec Equipment"
> <tentec@contesting.com>
> Sent: Thursday, May 17, 2012 12:09 AM
> Subject: Re: [TenTec] Top receivers
>
>
>> On 5/16/2012 10:42 PM, Jim Brown wrote:
>>
>>> With some receivers it certainly does, especially those that are power
>>> or supply voltage limited. BUT -- I like to think that I know the
>>> difference between my ham rig and my home entertainment system.
>>
>>
>> I KNOW I know the difference, and kinda resent
>> the sarcastic implication... ;-)
>>
>>
>>
>>> FWIW, for ham radio at home, headphones have ALWAYS been my primary mode
>>> of operation. I use a loudspeaker only for casual listening.
>>
>>
>> ME TOO... in fact I am a huge headphone / headset
>> junkie. I am blessed in that my XYL does not whine
>> about me spending money on stuff... including another
>> headset. We both use the best wireless headphones
>> for listening to old time radios shows - the sound never
>> alters no matter where we roam throughout the place.
>> Makes raiding the fridge safe - we never miss any of
>> the show even though we leave the room.
>>
>> My preference on headsets is also related to the fact
>> the microphone is always a close talking type, which
>> stays put in the same place, no matter how far back
>> from the desk I lean, or whether I turn my head
>> from side to side, etc. A close-talking microphone
>> tends to be more noise rejecting (I don't like the
>> term noise cancelling... but that is another topic
>> for another day....)
>>
>>
>> Every
>>> radio I've ever owned has had quite adequate drive for headphones. On
>>> the other hand, a mobile radio, including a talkie, needs enough audio
>>> to get over ambient noise, and many of these rigs don't.
>>
>>> 10% distortion is a standard spec for industrial paging systems.
>>
>>
>> I suspect this tends to reinforce my point...
>> I think... ;-)
>>
>>
>>
>>> 10% distortion is a standard spec for industrial paging systems.
>> That's the distortion at the peak of the signal just below clip,
>> and is typical of many computer sound cards.
>>
>>
>> Geeze...are you sure about that ?
>>
>> I have been testing sound cards and microphones for
>> speech recognition companies since 1992... and no sound
>> card I ever used was rated at 10% THD.
>>
>> Typical specifications for cards in my machine might
>> look like this:
>>
>> Output THD+N at 1kHz (Front-out) : <0.0025 %(-92 dB)
>> Input THD+N at 1kHz : <0.0022 %(-93 dB)
>>
>>
>>
>> Even the venerable old Creative Soundblaster Audio PCI 16
>> had numbers like this back in the 1990s :
>>
>> Signal to Noise Ratio: 90 db
>> Total Harmonic Distortion @ 1 Vrms (10 KOhm load): 0.01%
>>
>>
>> I cannot address the rest of the post, as I am embarrassed
>> to admit I don't follow how it relates to the topic of ham
>> radio audio ... sorry.
>>
>>
>> ------------------------ K8JHR -----------------------
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>>
>
>
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