Multiple Speakers

[bwhite]

Throughout my life I have often connected multiple speakers to my scanner simultaneously[in parallel] (via the external speaker or earphone jack) so that the broadcasts are available in other areas of the house and garage.
I've done this with RS, Regency, Bearcat/Uniden scanners and don't seem to have suffered any ill effects including degradation of the audio at relatively high volumes or a dead scanner.
I realize this is a bit late to be asking, but, since the scanners are more costly now I don't want to jeaporadize them if this is a no-no.
Does anyone have any thoughts on this ?
Thanx.

 

[MacombMonitor]

If you take two 8-ohm speakers, and parallel them, the impedance will drop to 4-ohms. You might get away with this, but more than two would be asking for trouble.

 

[bwhite]

Kinda what I thought too from things I'd heard over the years, there are and have been 3 on there for several years, there were 4.
Any idea what negative repercussions are thought to occur so I can be on the lookout?
Thanx

 

[Thunderbolt]

Kinda what I thought too from things I'd heard over the years, there are and have been 3 on there for several years, there were 4.
Any idea what negative repercussions are thought to occur so I can be on the lookout?
Thanx

The first thing I would look for is a lot of static when turning the volume knob, then along with: popping audio, which causes the volume level to drop, then "pop" again back to normal. Kind of like a short-circuit on the audio. Likewise, this can occur when moving the volume knob.

If I was you, I would connect as many speakers as you need in parallel, preferably an even number, then add resistors to the speakers to change their impedance, so the load at the scanner doesn't fall below 8 ohms.

73's

Ron

 

[kb2vxa]

Hi Brian and all,

Your best bet is a "constant impedance" distribution system. Run a two wire line from the speaker output point to point to whatever locations you choose and tap it at each location as if you were going to connect speakers in paralell. Use a line to voice coil transformer to feed each speaker, connect the "line" side to the line and the speaker to common and the appropriate wattage tap. I would think to use the lowest one since the total should never exceed the output capability of the amplifier, in this case usually 2.5 watts. If you want more volume, use a bigger amp. If your scanner has a recorder output use it alongside the local speaker which eliminates one not needed on the line. If all you have is an external speaker output use it and adjust the scanner's volume contol for usable, clean sound from the external amp.

Tech note:
A transistor is a current device, the more you load the output the more current it draws. This is why connecting less than a 4 ohm load is inadvisable, too much current and it goes into thermal runaway and poof, bye bye transistor. It doesn't care about a high impedance load or even an open circuit, the less current the better actually. You can drive a high impedance amplifier input with no trouble for the scanner or any other device with a transistor output. Driving the 70.7 volt (600 ohm) speaker line presents no problem as long as the wattage output isn't exceeded by drawing too many watts from it, that's where the transformer wattage taps come in. That's how it's done professionally with PA systems, stage sound reinforcement and even the juke box at your favorite diner or bar.

You want to drive your neighbors nuts? Use a 1,000W Crown amp and turn it up LOUD. "Jiggers! IT'S A RAID!!!" (;->)

 

[bwhite]

Looks like it'll probably be 2 or 3.
I hate to say it but it's been 30 years since high school electronics so there is no hope that I can recall how to do the calculation.
Can you advise how to calc the resistor value needed and will I be using one in each parallel branch?
Thanks.

 

[Andy128]

bryanwhite,

I too sought info on this topic. Definetly don't want to drop below 2 ohm and in most cases below 4. My solution was to do as kb2vxa suggested. Look for a 70 volt PA Amplifier on e-bay. Then run 18 gauge speaker wire to your furthest speaker ilocation in the house from the amplifier. You will need to buy 70 volt speakers that typically have multiple watt settings (2.5, 5, 10,15 or higher in some cases). When buying your speakers (around $20-$45 on e-bay) make sure you don't exceed the total wattage or your PA Amplifier. For example- you have a 100wat amplifier- you could buy ten -10 watt speakers or any combination of wattages not to exceed the 100 watt amplifier. You can also attach, as I did, a volume control at each speaker. These run around $10 to $15 bucks. Connect each speaker to the wire and then run that wire back to the main speaker wire and tap into it (radio shack has clips for this). Simple and works great.

To hook the scanner to the amplifier simply get a 1/8 mono cord with a RCA jack on one end or an adapter for the 1/8 jack and plug from scanner to amplifier.

It will run a couple of bucks but it is the only safe way to have multiple speakers from one device. If you buy a stereo amplifier you will still be limited as to how many speakers you wire together. Droping below 2ohms can seriously damage the amplifier and possibly the scanner.

Good luck.
Andy

 

[bwhite]

Wow, you guys have gotten way beyond me (take that as a compliment).
I'll try to digest this info when life gives me a pause.
Thanks for the replies.

 

[mgosdin]

I'd like to ask a quasi-related question. What's the best way to take the headphone output from my 3 scanners and combine them so that I can put a speaker outside and be able to hear them all in my back yard? I was thinking in terms of a mixer / pa amp type setup, is that a good idea?

Mark Gosdin

 

[pro92b]

I'd like to ask a quasi-related question. What's the best way to take the headphone output from my 3 scanners and combine them so that I can put a speaker outside and be able to hear them all in my back yard? I was thinking in terms of a mixer / pa amp type setup, is that a good idea?

Mark Gosdin

It depends on which three scanners you want to connect. Some do not have grounded audio output jacks. An isolation transformer would be needed in that case.

 

[Andy128]

Try-

three speaker wires (one from each scanner) to a three switch box which is connected to a speaker. Select A,B,C depending on which scanner you want to hear.

Andy

 

[Al42]

Look for a 70 volt PA Amplifier on e-bay. Then run 18 gauge speaker wire to your furthest speaker ilocation in the house from the amplifier. You will need to buy 70 volt speakers that typically have multiple watt settings (2.5, 5, 10,15 or higher in some cases). When buying your speakers (around $20-$45 on e-bay)

For that kind of money you can buy amplified speakers, hook the inputs in parallel and forget the PA amplifier and transformers. (Amplifier inputs are high-impedance, so you could probably hook a few dozen of them in parallel before you had any problem.)

 

[Andy128]

Al42-

Looked high and low- asked many people and no one ever suggested that. I am not that good with electronics but mechanically adapt- Could you explain how that works? For instance- Even in parallel the impedence drops, so how does it not affect the amplified speakers? I know the impedence is high, but not knowing the parameters or formula to calculate where my safe point is based on the wattage of speakers and such, makes me nervous. Anyway- If you could elaborate a bit further or pm me with the instructions I would be most appreciative.

Andy

 

[n0zed]

I think I would just pick up one of the little FM broadcast xmiters made to be used with a I-Pod or computer sound card and screw running wire everywhere , played with one for a while in the truck and scanner in quad is something else
just MNSHO
ghk

 

[pro92b]

The Radio Shack amplified speaker has an input impedance of 100 Ohms and is transformer isolated. Three locations and three scanners would require nine speakers if I understand Al's proposal. Each scanner would drive three speakers, a composite impedance of about 33 Ohms. Each speaker needs a 12 volt power supply. The only volume control in this system is at the scanner and all speakers would be the same loudness.

 

[bwhite]

This is all starting to sound like putting the baby monitor transmitter next to the scanner and the receiver on me would be much less of a head-banger.....

 

[kb2vxa]

Hi again,

Let's start with the simplest misconception.

"The first thing I would look for is a lot of static when turning the volume knob, then along with: popping audio, which causes the volume level to drop, then "pop" again back to normal. Kind of like a short-circuit on the audio. Likewise, this can occur when moving the volume knob."

That's a symptom of a dirty volume pot and has nothing to do with the subject at hand. If that's your problem a squirt of contact cleaner and a few twists of the knob to wipe it clean will make it good as new.

NOW HOLD ON THERE! You guys weren't paying attention and went way out in left field. I'm not about repeating myself so please reread what I wrote and save yourselves the confusion (again) and the expense of a "70.7 volt amplifier" of which there is no such thing.

"This is all starting to sound like putting the baby monitor transmitter next to the scanner and the receiver on me would be much less of a head-banger..... "

I'm beginning to agree with you, groan.

 

[bwhite]

I was good even to the point where someone said to add a resistor to each branch to bring the total resistnce/impediance back up to the 8 ohm range but I don't know the value of the resistors (or coils) to add.
Warren, I'm sure your advice is the best, but, you're beyond me without having my hand totally held.
(Thanks though).
I knew the part about static/popping was contactcleaner time.

 

[kb2vxa]

Hi Bryan and all,

Power is wasted in resistors and there is precious little afforded by the output amp in a scanner. If you want me to hold your hand I'll be glad to do so, e-mail warren@kb2vxa.net and I'll walk you through it. Hang around here long enough you'll end up like me, tap dancing in a mine field while juggling hand grenades.

While I haven't gotten over my sarcasm (give me time) I don't claim to be an expert or an engineer either. It's in the ham tradition to share knowlege and experience, it's called "elmering". I always offer what I have, returning the favor so to speak to those who have elmered me. Give me the chance and I'll pass along the experience I gained working for Runyon Music, distributors of those well known Rowe-EMI juke boxes.

 

[Al42]

Power is wasted in resistors and there is precious little afforded by the output amp in a scanner.

Think series/parallel when you help him, Warren. Do you remember the PopTronics Sweet 16 speaker?