8 Ohm Intruder Alarm Extension Speakers

[Alfie]

Afternoon all, first time here!

Here's one of those, probably common, intruder alarm extension speaker queries for you!

As a lover of almost anything old-ish, made by Scantronic, I decided to install my recently acquired Scantronic 9800 as a system for the house loft space, and eventually, the house in general (I've already fitted an old 9448 in the garage with pleasing results!). Now some of you may be jumping out of your seats after me saying "I've installed a Scantronic 9800" and will be shocked to know it is in an airing cupboard as well. Don't worry, it's very dry, and the hot water tank isn't really in there any more.

 

Now I ordered an Elmdene TS443-8, 20 Watt, 8 Ohm speaker for the system by mistake. I should have been more vigilant and bought he 16 Ohm variant, but I'm not going to hassle the wholesaler and try to return it; I'm going to make the best out of a bad mishap. It states on the front cover of the installation manual and user guide that the 9800 will accept 2 maximum 9040 16 ohm speakers or their equivalents. Now, since I'm only fitting one speaker it shouldn't matter if it is 16 or 8 Ohms, since all I'm doing is substituting 2 speakers of 16 Ohms for one of 8 Ohms, so in theory I'm just simulating the load of 2 speakers on the panel but with only one speaker, which is within panel limits I believe. Tested, sounds fine (and a whole lot cleaner sound than the Kinetic speaker I had before). All well and good, however I am running this by all of you as a failsafe measure so I don't kick myself in the shins and shout "you should have thought better and bought the right speaker" in future after breaking something, which I don't want to do.

 

It should be fine to put an external bell box on the system, since I'm only simulating 2 speakers on the system, again, I believe it's within panel limits, but I'd like to know, just in case, if I will need to do something to the panel to support it or something like that.

 

Many thanks in advance for your advice!

[sixwheeledbeast]

If it's 16 Ohm speaker driver it should be driving 16 Ohm.

Wiring of multiple speakers would depend on the wiring configuration.

Series - Zt = Za + Zb         Parallel - Zt = (Za * Zb) / (Za + Zb)

 

We don't know what's on the system to know how loaded the panel is. Most systems can take a speaker, a bellbox, a keypad and a hand full of PIR's from there PSU.

 

[Alfie]

27 minutes ago, sixwheeledbeast said:

If it's 16 Ohm speaker driver it should be driving 16 Ohm.

Wiring of multiple speakers would depend on the wiring configuration.

Series - Zt = Za + Zb         Parallel - Zt = (Za * Zb) / (Za + Zb)

 

We don't know what's on the system to know how loaded the panel is. Most systems can take a speaker, a bellbox, a keypad and a hand full of PIR's from there PSU.

 

As of now the panel has one Pyronix Colt PIR, one panic button, two Scantronic 9825 keypads and the one speaker. In future it will have one set of door contacts added onto it, and three other PIRs. I plan to add a Pyronix Deltabell Plus when I add the other detectors.

Edited August 16, 2017 by Alfie

[sixwheeledbeast]

59 minutes ago, Alfie said:

As of now the panel has one Pyronix Colt PIR, one panic button, two Scantronic 9825 keypads and the one speaker. In future it will have one set of door contacts added onto it, and three other PIRs. I plan to add a Pyronix Deltabell Plus when I add the other detectors.

 

So you need to calculate the total system current while in alarm to make sure you don't overload the panels power supply.

While doing this you would also calculate the systems standby current and work this out against your standby battery to make sure it's adequate for say 12 hours of power outage.

[Alfie]

4 minutes ago, sixwheeledbeast said:

 

So you need to calculate the total system current while in alarm to make sure you don't overload the panels power supply.

While doing this you would also calculate the systems standby current and work this out against your standby battery to make sure it's adequate for say 12 hours of power outage.

I've decided to perform the quick, yet expensive, fix for all this: order the correct speaker as a replacement. I ran a couple rough visual tests against my Kinetic 16 Ohm 12 watt extension speaker and the Elmdene speaker and it seems that both draw the same amount of juice as each other, and that is just through looking at the power LED on the keypad. Said LED dims by the same amount in alarm for both speakers. I also checked the amount of heat that was being given off from the transistor with heatsink on it and it, again generates the same amount of heat for both speakers. I am, however, sceptical that this is, by any means, fair and of anything to go by. Hopefully when the new speaker comes it should be at least good and I won't have to worry about overloading the panel as much as I have done.

[sixwheeledbeast]

1 hour ago, Alfie said:

 I ran a couple rough visual tests against my Kinetic 16 Ohm 12 watt extension speaker and the Elmdene speaker and it seems that both draw the same amount of juice as each other, and that is just through looking at the power LED on the keypad. Said LED dims by the same amount in alarm for both speakers. I also checked the amount of heat that was being given off from the transistor with heatsink on it and it, again generates the same amount of heat for both speakers.

 

A multimeter is the normal tool for testing these things.

Power LED dimming and temperature output is not going to indicate much change unless severely overloaded.

[Alfie]

1 minute ago, sixwheeledbeast said:

 

A multimeter is the normal tool for testing these things.

Power LED dimming and temperature output is not going to indicate much change unless severely overloaded.

Too bad mine is broken! Anyway I knew that what I was looking at would not actually help that much, if at all with my issue. However, new speaker ordered. I can always use the other speaker on something else.