45 ohm speakers?

[Cagey]

I have a quite a few 45 ohm speakers laying around from the intercom system I took out. I want to build a couple of mini amps and at least try these speakers, but the ohms thing has me perplexed.

Using this formula, Resistance = (Speaker A x Speaker B) / (Speaker A + Speaker B) I looks like could get close to 8 ohms by putting a 9.7-9.8 ohm resistor (or combinations thereof) in parallel. Am I headed in the right direction? Thanks in advance for your help.

[defaced]

6 of them in parallel will get you to 7.5 ohms, which is close enough. Your approach of adding the 9.8 ohm resistor will get you there too, but if will need to be large enough in power rating to handle the entire output power of the amp and then some. Say you've got a 100 watt amp, you'd probably want a 150 to 200 watt resistor in there for safety.

[Alex R]

Four in parallel would give you something you could drive ok with an 8 or a 16 ohm output.

A resistor in parallel would eat up a proportion of your signal, especially if you are paralleling it with a larger impedance. Also because it is a fixed resistance not a varying impedance like a speaker it will possibly affect the sound.

[Alex R]

wow a simulpost

[Amp Kat]

Those are not very high wattage speakers so careful there. They are actually made for talk back applications as a microphone. I hook them up to 8 ohm loads all the time and they work fine. They would probably be more dynamic at the correct ohmage matchup but as I said they are not very powerfull and the frequency response is not very good either.

[Chuck H]

If you want to build low wattage amps with them you'll be starting from scratch, right? You could just use an OT that matches those speakers to the power tube/s correctly. The rub is that on those amps, when/if a speaker fails you will not be able to get a proper replacement for it, and so have to change out the OT to match a different speaker load.

Chuck

[Gtr_tech]

I assume these are 8" "paging" speakers. You could make a couple cabs with 3 in each (parallel) to get around 8 ohms using both cabs, or close to 16 using one. They prolly won't sound all that great tho....I bet they have small-ish coils and end up soundin' boxy.