Batboard

I am starting an install in my trusty '00 Grand Cherokee which will consist of three mobiles in total. A spectra, a CDM and a dualband Yaesu.

For the challenge, being that this is a GC I thought up this brilliant idea that I am sure no one has ever thought of before! (big big wink), connecting all of the audio outputs into one single speaker, thus saving tons of space!

Now the idea may be absurd, but I am smarter then just twisting them all together and blowing all the sources (wink again), so what I was wondering is if this has ever been successfully tried before with some kind of mixer perhaps or something?

Using one speaker would make life MUCH easier!

Ben10001 wrote:I am starting an install in my trusty '00 Grand Cherokee which will consist of three mobiles in total. A spectra, a CDM and a dualband Yaesu.

For the challenge, being that this is a GC I thought up this brilliant idea that I am sure no one has ever thought of before! (big big wink), connecting all of the audio outputs into one single speaker, thus saving tons of space!

Now the idea may be absurd, but I am smarter then just twisting them all together and blowing all the sources (wink again), so what I was wondering is if this has ever been successfully tried before with some kind of mixer perhaps or something?

Using one speaker would make life MUCH easier!

DO NOT GROUND EITHER OF THE MOTOROLA SPEAKER WIRES. With that said, on most Motorola radios, there is a DC bias on both speaker wires. Grounding either of the wires will result in damaging the audio output of the radio. It is never a good idea to just connect multiple speaker output wires together. You might get away with it on multiple scanners, but be very careful if your trying to do this on a two way communications radio.

It would be well worth your time to obtain a service manual of each of the radios you intend to do this with and check out how the audio output stages are wired.

I have 6 radios in my truck and each of them have their own speaker. If you look around, there is always room under the seats, up behind the dash and so on. If needed, you might try obtaining smaller speakers to take up less room.

Jim

The right solution is a speaker combiner... Fleet Radio Products made some for several years, but then disappeared. They now show up on eBay...
http://www.ebay.com/itm/4-CHANNEL-AUDIO ... 416947ec3d

Not the seller, just a happy customer... I'm running 3 in my current truck. No, they're not cheap.

$225 for a spec-grade combiner is a good buy compared to the bother of setting up your own small mixer-amplifier, and it'll save you a lot of space. One other supplier you might wish to check out is Radio Design Labs (RDL)) which makes a ton of small audio system interface devices. The RDL website for some reason does not have the "Stick-On" devices that are used for this kind of situation, but I found them at another site, which is, http://www.fullcompass.com/category/Rad ... dules.html

tvsjr wrote:The right solution is a speaker combiner... Fleet Radio Products made some for several years, but then disappeared. They now show up on eBay...
http://www.ebay.com/itm/4-CHANNEL-AUDIO ... 416947ec3d

Not the seller, just a happy customer... I'm running 3 in my current truck. No, they're not cheap.

+1 for the Fleet Radio combiner (I run two.) The new manufacturer will sell direct if you don't want to deal with Ebay and Paypal: http://www.cmdcomm.com

Another suggestion:
1) Get some audio isolation transformers, such as this:
http://www.mouser.com/ProductDetail/Xic ... 2fC7J2U%3d
2) Connect secondary to radio.
3) Sum the primaries through one 10 kOhm resistor per transformer on one side, and wire the other side to a common point.
4) Connect one 100 Ohm resister from the summing node to the common point.
5) Feed into a cheap amp, such as this:
http://www.mcmelectronics.com/product/S ... -/50-10145
There! One speaker, many radios, each isolated.

Here's a simple and cheap method to use multi-radios with 1 speaker, but this method uses the vehicle's stereo speakers (I do not listen to THAT radio), so i simply disable the factory junk and run each radio to a different speaker, the main is feeding the dash left speaker, the secondary feeds the dash right speaker.
Rear speakers used for hammy things, same scenario, just a little higher audio level settings.

NOT high tech and certainly NOT for those that have that noise box running either, but I hate commercials and this helps me avoid them even better than ever!

Of course, every stereo system demands checking speaker impedances, so a caveat is implied.
Isolation transformers might need to be used, as resistors for summing lines, but usually not if running single radios, single speakers.
Always match impedances to your radios, and do NOT ground those 'Trac speaker outputs, or the CDMs, Etc...Check the schematics to see WHAT you can do with your radio's speaker output leads first!

There are also less expensive audio combiners on ebay.

http://www.ebay.com/itm/RDL-Stick-on-mo ... 2c680de58b

One thing to note with the RDL Stick-On combiners is that they don't have internal speaker-level amplifiers or per-channel level adjustment. And if you go shopping for an amplified speaker to use with one, do not get the Workman amplified speakers.. they are complete and total garbage.

Take four speakers, take two out of the boxes and mount them to the faces of the other two. Point both assembled pairs at each other so the exposed magnets are facing each other. Now take thick plastic and form a horn out of it to wrap around the now "block" of four speakers and put the audio waves toward the occupants of the vehicle...

SlimBob wrote:Take four speakers, take two out of the boxes and mount them to the faces of the other two. Point both assembled pairs at each other so the exposed magnets are facing each other. Now take thick plastic and form a horn out of it to wrap around the now "block" of four speakers and put the audio waves toward the occupants of the vehicle...

As an audio engineer, this makes me cringe......

Should work though for a 2-way. Not a whole lot of worry about coverage pattern and phase coherency here

That and less than 35dB S/N ratio in a car due to road, wind, and other noises...

Universal Radio carries a small speaker that is tradenamed "Altec" which is about 2X2X2 inches and has very good
communications quality audio. Due to the small size, these units can usually be fitted into very small spaces in the car
and you would not need to worry about any audio combining questions.