Ideas for installing P.A. system in Rescue station

[UFEMTFF]

I work at a rescue station that has two trucks running out of it. All units are paged and operate on VHF Hi-band, but the two trucks have different paging tones.

Currently, we carry around portables at all times to listen for calls. I wanted to set up a simple (and hopefully fairly cheap) PA system to be able to monitor for calls. I was wondering what my best options were.

I would like to have a total of 6 speakers:
- TV room
- Male Bathroom
- Female Bathroom
- Male Bunkroom
- Female Bunkroom
- Bay

I was looking on eBay at PA amplifiers, and saw one ranging from 20watt to 100 watt. How much power would I need?

Also, what would be the best radio connection. I could either buy a cheap scanner (<$30) and have it just set to scan our freq., or I was thinking about buying 2 minitor pager/charger sets and connect them. But, that would probably require reprograming of the pagers. Minitor IIs work great, but how easy are they to reprogram the freq. if I get them off eBay?

Thanks for any help or direction anyone can provide!

 

[Grog]

I'll just say if anyone needed to listen to one set of tones, you could pick up a two-tone decoding capable mobile, and just hook it up as a monitor. The maxtracs are really cheap some days.

Reprogramming the freqs and tones on a minitor II would not be the cheapest thing to do. The newer pagers are fully programmable, and a lot easier to reprogram. They just aren't like the older stuff.

 

[cellblock776]

Just a idea, try posting this to the forums over at Firehouse dot com- http://www.firehouse.com/ . I'm a member there, cellblock, and there are several regulars on the boards there who have workd in the fire/rescue service for years. They may have ideas or experiance using the exact type of system you are trying to figure out. They can give you first hand info about the types of systems they use/d and what works and what didn't.
Good Luck,
Steve

 

[UFEMTFF]

I'll just say if anyone needed to listen to one set of tones, you could pick up a two-tone decoding capable mobile, and just hook it up as a monitor. The maxtracs are really cheap some days.

How hard is it to hook up a mobile to a ac power source? Also, would it be able to decode two separate tone pairs?

 

[UFEMTFF]

Just a idea, try posting this to the forums over at Firehouse dot com- http://www.firehouse.com/ . I'm a member there, cellblock, and there are several regulars on the boards there who have workd in the fire/rescue service for years. They may have ideas or experiance using the exact type of system you are trying to figure out. They can give you first hand info about the types of systems they use/d and what works and what didn't.
Good Luck,
Steve

Thanks for the advice, I checked it out. Which specific forum should I make a post in, since I've never posted there before and there are a TON of forums?

 

[cellblock776]

Thanks for the advice, I checked it out. Which specific forum should I make a post in, since I've never posted there before and there are a TON of forums?

I'd post it on the main "Firefighters Forum" http://forums.firehouse.com/forumdisplay.php?f=286 , with the usual n00b preamble ie "Hi, I'm new and wasn't sure where to post this...blah blah blah.." It will get the most exposure there and if it belongs somewhere else the webteam (moderators) will move it.

 

[Grog]

Just hook it up to a 12v power suppluy. If you were not going to use it for transmitting, even a small 3 watt would be enough to run it for RX only.
This would be enough to just run it for RX....
http://www.radioshack.com/product/i...tId=2032056&kw=power+supply&parentPage=search

These are made for certain mobiles...
http://www.astroncorp.com/sps.shtml

These are just the basic power supplies, in many power levals......
http://www.astroncorp.com/linear.shtml

I'm not sure if you had it to scan two sets of tones, if iit would be reliable in decoding 100%.

If you think you'll want to go that route, you can ask on the batlabs forums. They know just about everything moto-wise
http://batboard.batlabs.com/

How hard is it to hook up a mobile to a ac power source? Also, would it be able to decode two separate tone pairs?

 

[KE7TJK]

I would suggest either a Plectron, or the Motorola tone activated receiver.

They both have external jacks for speakers, and I know the Motorola has a jack on the back that is for activating a buzzer, siren, or similar. When the tones hit, the monitor not only has a long tone, it also closes a set of contacts connected to that jack.

Ebay has them, and you might even contact one of the local F.D's to see if they have any surplus.

 

[UFEMTFF]

I would suggest either a Plectron, or the Motorola tone activated receiver.

They both have external jacks for speakers, and I know the Motorola has a jack on the back that is for activating a buzzer, siren, or similar. When the tones hit, the monitor not only has a long tone, it also closes a set of contacts connected to that jack.

Ebay has them, and you might even contact one of the local F.D's to see if they have any surplus.

Well, I worked in stations before, and I doubt we'll ever install a plecktron again. I liked the idea of amplified pager chargers hooked up to an amp because we can control the volume easily, as to not have a heart attack every time a call is received.

 

[Al42]

You're looking to feed 6 speakers with good volume - that's about 15 watts total, allowing for the volume control to be run at less than half. Get an amp that has 70 volt output, the speakers (and cases, mounting brackets, etc.) and a 70 volt transformer for each speaker with outputs at 1/4 watt, 1/2 watt, 1 watt and 2 watts, or something close to that. You can run a single line from the amp to one speaker, then to the next one, then to the next one, etc. Hang a transformer off the line at each speaker point and connect a speaker to the transformer. (The transformers come in various impedances - 8 ohms, 16 ohms, etc. Match the transformers to the speakers they'll be feeding - they don't all have to be the same. And the setting on each transformer doesn't have to be the same - you'll probably want lower volume in the bathrooms (echo off the tile) and the bunkrooms (or maybe more in the bunkrooms).

 

[ResQguy]

Get a Federal Signal Informer http://www.federalwarningsystems.com/products.php?prodid=25 and hook it to a Bogen or similar PA amplifier http://www.bogen.com/products/mixeramps/ .
If your department is going to rely on it, don't skimp on the parts.

 

[UFEMTFF]

You're looking to feed 6 speakers with good volume - that's about 15 watts total, allowing for the volume control to be run at less than half. Get an amp that has 70 volt output, the speakers (and cases, mounting brackets, etc.) and a 70 volt transformer for each speaker with outputs at 1/4 watt, 1/2 watt, 1 watt and 2 watts, or something close to that. You can run a single line from the amp to one speaker, then to the next one, then to the next one, etc. Hang a transformer off the line at each speaker point and connect a speaker to the transformer. (The transformers come in various impedances - 8 ohms, 16 ohms, etc. Match the transformers to the speakers they'll be feeding - they don't all have to be the same. And the setting on each transformer doesn't have to be the same - you'll probably want lower volume in the bathrooms (echo off the tile) and the bunkrooms (or maybe more in the bunkrooms).

Well here's an update. We got a Mobile Motorola unit programed to alert for either or both of our units.

Now, I have to get an amp and install the speakers - and that's where I'm fuzzy.

I plan on getting a Radio shack 20watt amp. I know it has outputs at differnt ohms as well as a 70 volt output. What do the transformers do exactly?

 

[UFEMTFF]

Actually, what I plan on install is something like this:
http://www.proacousticsusa.com/productdetail.php?pId=500

It looks like they come already with transformers attached. So I could just wire them in series and be set?

What if the volume is too loud in some rooms? What would I do then?

Finally, where is the best (cheapest) place to purchase these speakers?

 

[Audiodave1]

Hello,
Putting together a "70v" speaker system isn't that hard once you get the proper gear but audio can be a complicated world and good sound rarely happens by accident.

A 20w amplifier should be sufficient to power 6 speakers assuming you do not have any enviroments that are overly noisy.

What type of speakers, the most efficient type are horn type speakers which I would suggest going looking to Bogen for. (Good prices, reliable)
http://www.bogen.com/products/pdfs/hornspeakerpdfs/SPT5As.pdf

Look in the phone book under Audio/Video dealers for a Bogen dealer or Google it....or email me.

No transformers to buy, it's built in already and has selectable "Taps" which directs a specified amount of power to that device.

Home stereo type speakers are not nearly as efficient (That is, how much sound does it put out for a given input. A speaker with a sensitivity rating of 86dB is common for a typical stereo speaker, a speaker that produces 96dB is subjectivly twice as loud, 10dB more efficient for the same input power, the Bogen has a sensitivity of about 96dB)

Don't use home stereo speakers.

What does the transformer do and how do I know how mant watts to set it at?

In short, if you have an amplifier that is 20w RMS @ 70v then the SUM of the output taps on the 6 speakers cannot (Should not) exceed 20w when added together.
Quick example, I have 20w to work with, I tap 2 speakers at 5w, 4 speakers at 2.5w =20 watts.

For louder areas set the tap higher. There is a 3dB difference in output level between taps usually (3.75w to 7.5w is 3dB) but remember, the sum of all the speakers taps should not exceed the amplifier output power.

The tap is usually selectable with a screwdriver or via a screw terminal strip.

Wiring, use 16awg wire, preferable twisted cable.

I'm getting all technical, I know but I do this stuff all day for anything from churches to stadiums. It's all the same. How loud do you need it and how much background noise to you have to overcome. You likely don't have a meter to measure this but for intelligible sound, an announcement has to be 10-15dB louder than the background noise.

The above suggestion and examples may work for you and you may be able to do it yourself. If you are unsure of the setup get a qualified audio person to assist especially if it could mean the difference between hearing a page to your station and missing one due to a faulty or inadequet system installation.

In case your head isn't spinning enough here is another link that explains 70v systems.

http://qscaudio.com/support/library/guides/cxgide.pdf

Good Luck and don't hesitate to PM or email me if you want to talk need some assistance getting in touch with someone in your area that could help.

Than company I work for makes speakers for an application like this but are way overkill. (And $$$$)

Dave Howden
Director of Technical Services
Community Loudspeakers
www.loudspeakers.net

 

[Audiodave1]

Bummer,
6 of these just went for $13 ea on Ebay....

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5856094543&category=14973

After re-reading your original post the ceiling speaker you just posted may work for the TV room, bathroom, sleeping area etc but would likely not work well in the bay.

The bay want's a more efficient horn speaker for sure.

If one's too loud in a particular location you just set the tap to a lower wattage on that speaker. 2 w would may be loud enough for the bed/bath rooms. (Bastards don't give a sensitivity figure for the 8" speaker so I can't tell just how loud it will be at ear level but personally I would not jump at this device for that price anyway)

If you got the RS amp already (20w) then using 5 of these has consumed 10w, leaving you 10w for a horn speaker in the bay where you need it louder...likely.

Dave

 

[Al42]

So I could just wire them in series and be set?

You wire them in parallel.

 

[UFEMTFF]

Bummer,
6 of these just went for $13 ea on Ebay....

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=5856094543&category=14973

After re-reading your original post the ceiling speaker you just posted may work for the TV room, bathroom, sleeping area etc but would likely not work well in the bay.

The bay want's a more efficient horn speaker for sure.

If one's too loud in a particular location you just set the tap to a lower wattage on that speaker. 2 w would may be loud enough for the bed/bath rooms. (Bastards don't give a sensitivity figure for the 8" speaker so I can't tell just how loud it will be at ear level but personally I would not jump at this device for that price anyway)

If you got the RS amp already (20w) then using 5 of these has consumed 10w, leaving you 10w for a horn speaker in the bay where you need it louder...likely.

Dave

Thanks very much for all of your input, but now I have some more questions.

1. My boss wants all the prices spelled out. Where would be the best place to purchase 6 ceiling speakers and 1 "horn" speaker?

2. Would a 30amp PA be enough?

3. How hard of a job is it to have a speaker controled by a volume knob in the same room? The reason I ask is because my boss wants a speaker in his front office, that he can turn up and down independently of how loud we have ours in the station.

Thanks again for all of your help and info.

 

[Al42]

2. Would a 30amp PA be enough?

More than enough, unless you have a particularly large, noisy room to cover.

3. How hard of a job is it to have a speaker controled by a volume knob in the same room? The reason I ask is because my boss wants a speaker in his front office, that he can turn up and down independently of how loud we have ours in the station.

Look for an "L-Pad" control. You can drill a hole in the speaker enclosure and mount it right where he can get to the knob. There should be wiring instructions with it (although there are only 3 wires to connect).

 

[ffexpCP]

A minitor II is not programable. It requires crystals and tuning at a radio shop. Tones are set by these things called 'permacode active filters.' They are freq. specific, just like a crystal, but can be changed by anyone in just a few minuites. The minitor 3,4, and 5 are programable by a computer.

 

[KE7TJK]

Well, I worked in stations before, and I doubt we'll ever install a plecktron again. I liked the idea of amplified pager chargers hooked up to an amp because we can control the volume easily, as to not have a heart attack every time a call is received.

Both Plectron and the Motorola equvelent have volume control knobs. The Motorola we had in our old station was kept at about mid volume, and when the tones hit, it 'beeped' at max volume.The Monitor also had an internal relay, that when the tones hit, it closed the relay, activating a very loud buzzer we had plugged in to the relay terminals. This monitor previously was used to activate the siren mounted on the outside of the station. The monitor itself was kept at the alarm desk at the rear of the station, and we hooked up external speakers in each of the station rooms. The speakers we used were car stereo speakers mounted to the wall, and the office had a Motorola mobile speaker with a volume control knob installed in the case. No amp was required; it was plenty loud enough. In addition, everyone carried pagers on them, so if there was a call, the pagers and the station monitor 'beeped' in unison.

Just my two cents.

Good luck on whatever you do.