simple amp circuit for 48Ω speaker

[heuermh]

I found a few odd speakers at the junk store recently that I'd like to use in various contraptions and would like to include a simple amp circuit that uses the same 9V power adapter I use for my pedals.

I don't really understand impedance though.

I have ruby amp and smokey amp style circuits, but those are for 4, 8, or 16Ω speakers.  All of these old speakers are 48Ω.  Does it matter?  Any recommendations?

[Neil mcNasty]

If you connect 3 speaker rated 48 Ohm in parallel, you get 16 Ohms
If you have 6 of them in parallel you get 8 Ohm.
If you have resistors with a watt rating equal to the speaker wattage, you can use them in parallel to bring the total Ohm rating down to the desired value.

It is possible to connect speakers to an amp with different ohm ratings, as long as the speaker has the highest Ohm, meaning that an amp rated for 8 Ohm can handle a 16 Ohm speaker, but there will be a slight difference in sound compared to matched Ohm. (Sharper and more high end if I remember correctly)
Never connect a speaker with lower rating than the amp! Then you risk frying your output transformer!

[heuermh]

Thanks for the reply!

10W resistors have been a bit hard to find, I've found 47Ω resistors for the 48Ω speakers and 43Ω resistors for a 45Ω speaker.  Does it matter if the resistance is off a bit?

Guess now that I have the parts I could just try and see.

[motterpaul]

wow - that is weird. I googled 48-ohm speakers and got nothing. They might not be very efficient. What do they look like?

[heuermh]

The 45Ω one is a military air raid siren kind of thing, one 48Ω is in an enclosure that looks like it should be hanging in a 1930s junior high school auditorium, two are squat and rectangular like old car speakers, etc.

I don't expect any to sound very musical.  Which is kinda the point.