extension cabs

[LITTLEWING]

Hey chaps,

I have a Peavey 300 bass combo and would like to run an extension cab from it. It says to use another 4 ohm cab but I have access to an 8 ohm 1 x 15".

Can I use it without any ill effects to the Peavey? I'm probably wrong but I think it will be 6 ohms ( 4 + 8 divided by two ).

I run it at present with the master on full and only about 4 on the pre-gain so it won't be working too hard.

[Mr. Foxen]

Thats not how to do impedance (not ohmage, although it is measured in ohms) calculations, [url="http://wiki.basschat.co.uk/info:amps:impedance_and_wattage"]Bottom half of wiki[/url]

You end up with about 2.67 ohms, if you connect an 8 and a 4 in paralell (the usual way) adding in paralell will only decrease the impedance no matter how high an impedance you are adding.

At a guess, the amp has a 8 ohm speaker in it, and a second 8ohm would give you the 4 it is happy with, that's usual.

[LITTLEWING]

[quote name='Mr. Foxen' post='658513' date='Nov 18 2009, 08:27 PM']Thats not how to do impedance (not ohmage, although it is measured in ohms) calculations, [url="http://wiki.basschat.co.uk/info:amps:impedance_and_wattage"]Bottom half of wiki[/url]

You end up with about 2.67 ohms, if you connect an 8 and a 4 in paralell (the usual way) adding in paralell will only decrease the impedance no matter how high an impedance you are adding.

At a guess, the amp has a 8 ohm speaker in it, and a second 8ohm would give you the 4 it is happy with, that's usual.[/quote]

Ah, okay, my bad!

The combo is loaded with a 4ohm Black Widow. Will this still be okay with an 8 ohm in parallel?

[Wil]

Providing the amp can safely handle a load as low as 2ohms (some Peaveys certainly can do this) then it will be fine - bear in mind the 4ohm internal speaker will draw more current and hence be louder than the 8ohm cab when they're both hooked up though.