Speaker install question

newalarm

Active Member
So I was hearing a sound like water running at the house, and struggling to figure out where it was coming from. Found it was white noise coming from Elk speakers.
 
I just realized i messed up and installed to many speakers in parallel.
 
I have
2 x 8ohms ELK 73s
3 x 32ohms ELK SP12Fs
Total ohms in parallel: 2.91ohms
 
A good way to wire these would be 2 -8ohms in series and 3 -32 ohms in parallel. This would give me 6.4ohms. This would make the 8ohm speakers not as loud.
 
Are my calcs correct?
 
Does anyone know if this would damage M1g to run at 2.91ohms?
 
Thanks.
 
 
 
6.4 Ohms is correct.  
 
Connecting too low an impedance could, in theory, damage the audio output transistor(s) that drive the speakers.  But if you're still getting sound, you should be ok.  2.9 Ohms isn't that much below the recommended 4-8 Ohms that I would expect it to quickly damage things.
 
Thanks RAL. It has been like that for a week or  so. When i get home, i will make the changes.  I think alarm went off once but was immediately disengaged. We don't use speakers except in alarm.
 
Does going under the 4ohms damage occur if they are just sitting idle or under load (with speakers going).
 
With too low an impedance, you are placing a larger load on the audio output transistors than they were designed for.  If you were to drive the speakers at high volume for too long a time, that could cause the transistors to overheat and burn out.  Since you're still getting sound output, it seems like everything is ok.
 
At low volume or idle, there should be no problem. 
 
Thanks for your help. It is confusing subject. But once i found the calculation it makes more sense.  It would be nice if ELK did a little calculator, but most must know this cold.
 
I plan on adding one 32ohm. but that should work. Essentially, you want to keep ohms between 4 and 8 right?
 
Is the white noise I hear from the speakers due to the low ohms?
 
Yes, you want to keep the total impedance between 4 and 8 Ohms.  Adding another 32 Ohm speaker should get you to 5.3 Ohms.
 
I'm not sure where the white noise is coming from.  That seems odd to me.  I don't think it has anything to do with the impedance being on the low side.  Maybe someone else has some thoughts on this. 
 
I think I recall another thread where some others said they had noise on Out2.  If I remember correctly, that had something to do with the output being supervised.
 
As for the white noise.....can output 1 be turned on by rules and left on? That may explain it, And I agree with RAL that the white noise is evidence that the amplifier is still working. And for out2 I think that I read somewhere that the hissing was when you use a self contained siren and the out2 is set to voltage you can hear the 12VDC hissing?
 
Newalarm - If you want to get your head around the importance of having the proper speaker impedance then search the net for ohm's law and read examples and definitions until you understand what it means. It states the relationship between voltage, resistance and current flow in any given electrical circuit. When any one variable of the three changes it affects the other two.
 
Current flows in a circuit based on the potential supply (voltage) and the resistance in the circuit (ohms). When the ohms (resistance to current flow) becomes lower and the voltage is fixed then the current will increase and at a point it will become too great and something in the circuit will fail.
 
RAL - did I get that right?
 
It was common in the good old days that we would put speakers in the doors of our cars. It was also common to run the speaker wires from the radio to the door speaker through the door jamb. Many radios were damaged when that exposed speaker wire in the door jamb was pinched and shorted to ground or the two wires shorted to each other causing the resistance (inpedance) in the speaker circuit to go to nearly zero. The end result was that the load became too great, the final audio amplifier stage blew a transistor and the speaker went silent.
 
Mike.
 
mikefamig... Good site. Well explained. If you go back to main website, he got much of the info from Toyota training manual or something.
 
The Elk amplifier turns off when not in use - that shouldn't be creating noise.  The other output is supervised and if using a siren it needs a resistor across the terminals as well but that's not applicable to indoor speakers.
 
You may find that it's too hard to balance the audio outputs for the two different speaker types - if that's the case you can tie in a TWA or Elk800 amplifier so you can put each set of speakers on its own amp with separate volume controls.  The TWA has the added benefit that rules can mute certain zones and each one has a volume control IIRC and it's a direct plugin to the M1 so that has some nice added benefits.
 
Here is a quick and dirty spreadsheet I created last year for speaker calcs.
It handles upto 4 parallel speaker sets, with each set containing upto 4 speakers in series.
Per the above example, 2 8's in series, in parallel with 3 32's.
 
speaker_calc_sample.JPG
 
remove the .pdf
View attachment speaker_calc.xls.pdf
 
I'd have to do the down and dirty calcs, but I'm thinking in my head that the 2 8's would be series (16 ohms) with 2 32's in parallel (16 ohms) then parallel those (8 ohms) and then I'd have to figure where to drop the 32 from there.
 
I rewired it last night. Seems fine. tested each speaker and they all work. Put the two 8ohm in series and the rest in parallel. Done.
 
Though the software did something weird; i hit the 'send and speak' button on a zone and it got stuck and kept repeating command over and over until the control kicked me off. Don't know why the XEP is so finicky. Sometimes it kicks me off repeatedly, other it stays connected for a long time. Not sure if this is related to shutting off control
 
Thanks all.
 
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