8ohm speaker on 11ohm siren?

May 25, 2010
7,072
Tunkhannock, PA, USA
runesson said:
So I´ve run 100w 8ohm speakers on 100w sirens rated for 11ohm without problems (so far) ....

But a friend now argues that this may damage the siren!


Anybody got any experience with this?

Mixing impedenced will always damage either the speaker or the siren... It's just a matter of when...
 

runesson

Member
Aug 6, 2011
255
Northern Europe
So I sent sirennet.com an email requesting info on their new compact speaker: SIRENNET.COM - Sirennet Compact 100 Watt Speaker


They don´t mention the ohms on products on their website, but as this new speaker is very similar to other speakers on the market, that are labelled 8ohms, I thought I would check.


Here´s the answers I got:


_____


Sirennet: "all of our speakers are 8 ohm including the SNSP3"


Me: "The installation-manuals for both the SNSA1 and SNSA2 requires connection to 11ohm speakers! Not to mention that 11 ohm is the american and european industry standard. Does that mean you recomend connecting 8 ohm speakers to an 11 ohm siren?"


Sirennet: "I am sorry I did not write that correctly. Our SNSP100D is 11 OHM. So if a Siren recommends that, you should go with that"


Me: "So which siren can I use with the SNSP3?"


Phil @ sirennet: "We have sold many of the SNSA1 and SNSA2 with the SP3 speaker and no one has had any problems with it not working. ..... If you order it and there are any problems we can always exchange it or refund your card for you"


______


This is not to discredit sirennet or anything like that! I´ve heard nothing but positive about them, but I makes me curious!


I´ve had 8ohm speakers connected to 11ohm sirens before, but after reading here that it would damage the siren sooner or later, I stopped doing that. I guess when the installation-manual says to use 11ohms it´s wise to follow that requirement? ....or does it really matter?
 

psteele

Member
May 20, 2010
255
43.864776 -71.635851
runesson said:
I guess when the installation-manual says to use 11ohms it´s wise to follow that requirement? ....or does it really matter?

If you don't follow the requirement in the installation manual you run the risk of not having the siren covered by a warranty.
 

Solvarex

Member
Jun 2, 2010
561
Canada
Someone makes a siren speaker in an impedance other than 11 ohms? This is news to me. The only 8 ohm speakers I know of are for stereos and whatnot.
 
May 25, 2010
7,072
Tunkhannock, PA, USA
Solvarex said:
Someone makes a siren speaker in an impedance other than 11 ohms? This is news to me. The only 8 ohm speakers I know of are for stereos and whatnot.

8 Ohm speakers are usually made for home sound systems... Car speakers are usually 2-4 ohms...
 

acousticman

Member
Nov 5, 2011
27
US Salem,VA
If your siren is capable of driving two 11 ohm speakers in parallel (5 ohms), the you can connect a single 8 ohm speaker. Electrovoice made their original siren drivers in 8 ohms, not really sure why. I have not found why siren drivers


stuck to 11 ohms, a very odd impedance. A lot of European sirens drive a single 8 ohm speaker. Even stranger is the 2 ohm driver used in airborne sirens!
 

reduiyong

New Member
Feb 25, 2022
12
Essex
a 11 ohms speaker is actually about 4.3 ohms, I have tested many speakers including FS FS100 and whelen speaker; a chinese made 8 ohms speaker is really 8 ohms, which means it can only produce 1/2 of the amp power (11ohms 100w amp)
 

shues

Lifetime VIP Donor
May 21, 2010
10,276
NW Indiana
a 11 ohms speaker is actually about 4.3 ohms, I have tested many speakers including FS FS100 and whelen speaker; a chinese made 8 ohms speaker is really 8 ohms, which means it can only produce 1/2 of the amp power (11ohms 100w amp)

You seem confused on what that 11 ohm rating actually means. The late @Henry455 explained it best:

The confusion is the difference between RESISTANCE and IMPEDANCE. The speaker driver coil has a resistance of approx. 4 ohms and an impedance of 11 ohms Nominal, usually tested with a 1000 Hz tone. When dealing with speakers even though they are both measured in ohms they are not the same. To measure the driver resistance you can use a simple VOM, to measure the impedance you need different equipment including a tone generator. If you are measuring your drivers resistance at 11.4 and 9.5 ohms, something is wrong with the drivers.
 

reduiyong

New Member
Feb 25, 2022
12
Essex
You seem confused on what that 11 ohm rating actually means. The late @Henry455 explained it best:
That explains it, thanks! However I still dont quite understand why some brands' "11 ohms" speakers are not 4 ohms in resistance (eg. code3 C3500 speaker is about 5.5 ohms and feniex speaker is about 6.5 ohms), shouldnt their resistance be the same in order to perform the same 11 ohms impedance?
 

shues

Lifetime VIP Donor
May 21, 2010
10,276
NW Indiana
That explains it, thanks! However I still dont quite understand why some brands' "11 ohms" speakers are not 4 ohms in resistance (eg. code3 C3500 speaker is about 5.5 ohms and feniex speaker is about 6.5 ohms), shouldnt their resistance be the same in order to perform the same 11 ohms impedance?

Impedance has two components: resistance and reactance. Resistance comes from the magnet wire itself. Reactance comes from coiling that magnet wire and running alternating current through it.

Presuming that all of these speakers are actually designed for 11 ohms impedance, the differences in resistance that you have measured seem to suggest that each of the voice coils is made from differing gauges of magnet wire, coiled a differing number of times.
 
Last edited:

reduiyong

New Member
Feb 25, 2022
12
Essex
Impedance has two components: resistance and reactance. Resistance comes from the magnet wire itself. Reactance comes from coiling that magnet wire and running alternating current through it.

Presuming that all of these speakers are actually designed for 11 ohms impedance, the differences in resistance that you have measured seem to suggest that each of the voice coils is made from differing gauges of magnet wire, coiled a differing number of times.
That makes sense! however, wouldn't different resistance perform differently on the same siren amp? For example my HHS3200 may work best with one11 ohms in impedance and 4.3Ohms resistance speaker (due to the spec of whelen speakers ), and it makes the amp producing about 100W power max (connecting one speaker); but if I switch it to another 11 ohms speaker but lets say only 9.6 Ohms in resistance, wouldnt the 9.6 ohms speaker only produce less than half of the 100W power?

Or am I calculating it wrong?

I have just measured the actual current drawn from the same amp using different 11 ohms speakers that have different resistance; it seems that the less the resistance one speaker has, the more current will be drawn from the same amp, which produces more power; However I didnt notice huge differences on the current drawn between the code3 C3500 speaker and the FS FS100 speaker (5.5 ohms vs 4 ohms). In this case, although all siren amps require 11 ohms impendance speaker, why wouldnt any siren amps indicate the recommanded resistance on their specs? This really confuses me, thanks!
 

czolgista111

Member
Dec 27, 2021
66
Poland
If you have siren wthich need 11 Ohms you have to use 11Ohms speaker or higher. Polish ZURA`s use 8ohms speakers - Federal Signal use 11 ohms; One time I forgot and plugged the 8 Ohms speaker to the FS AS422 siren.. I just pushed horn.. and dead XDD but fortunately I repaired it. :p
 

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