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Re: How well does a 8x10" cab and a 1x15" cab go together?


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Posted by Milan on April 26, 2001 at 03:30:25:

In Reply to: Re: How well does a 8x10" cab and a 1x15" cab go together? posted by Jenny on April 26, 2001 at 00:34:56:

: Small language problems with me made my message unclear earlier. If you connect two (4 ohm) cabs parallel you do get 2 ohms but if you connect them 'the other way' in chain or in series or what ever it's called, then you should get 8 ohms, shouldn't you?
: The thing I'm worried about is when both cabs take equal amount of power from the amp, like you said. Won't the 1x15" cab break as the 8x10" cab can handle clearly a lot more power? So if I play at 400 watts, 200 of them will go for the 8x10" cab (no problem) and 200 watts to the 1x15" cab, which is clearly too much for it.
: I'm really bothered with this so please reply.

Hi Jenny,

There are a couple of variables at play in your situation. Yes, in theory, the power will be divided equally between the cabs if
they are wired in series(4ohms). You are faced with two possible problems, however.

First if the 15" cab is rated at a lowerwattage than the 8X10, given extreme circumstances(loud playing) you may indeed
blow it. This is a function of simple physics: 8 voice coils getting whacked with half the output of your amp, versus one voice
coil trying dissipate all that heat. The 8 voice coils in the 8X10 will more efficiently dissipate the power. Also, if you will be
using an ampeg style(sealed) cab in conjunction with a ported 15" cab, get a VERY high wattage 15" speaker. The ampeg design
acts as a physical high pass filter(8 sealed "boxes", also known as infinite baffles-each containing one speaker) which protects
those ten inch drivers from damaging excursions. A ported speaker will be subjected to greater excursions which can be
damaging.

The second problem may have to do with how your amp deals with the varying ohm load it is presented with. I'm no expert
here, but I understand that even an 8 ohm cab of a certain design(type of speakers, cab size, porting, etc) can drop as low
as 1 ohm at certain frequencies. Two different cabs, especially if they were not designed to be used together, can put
unexpected strains on the output stage of your amp. You didn't mention if your amp is tube or solid state. With a solid state
amp these varying ohm loads can result in weird damping(the amp won't "stop playing" when you do), wolf notes in the output,
or worse still, output stage clipping(guaranteed to waste voice coils). If you're using a tube amp the previously mentioned
problems can exist in addition to a very expensive one; you will got through output tubes like nobody's business. At something
like $50 for a good 6550(eight of them in a 400watt amp), you'll be retubing 4 times a year if you gig twice a week. Mesa/Boogie
is adamant about careful cab choice with their tube bass amp, the BASS 400+, and strongly recommend that matched cabs
be used in order to preserve tube life(this beast uses 12 5880 power tubes-yikes!).

So, choose carefully. You may consider getting a cab from the same manufacturer as the 8X10, one that will compliment your
current rig. Most manufacturers are pretty cool about emailing suggestions about what bits of their gear will work together best
If this isn't an option, move ahead slowly. When you first try the new setup, monitor your rig's performance, temperature, and tone.
If the speaker grills are removeable, look at the cones when you play. First one cab at a time, the both, looking for inconsistent coil
movement.

Oh yeah, be very careful when wiring up the cables to be sure the cabs end up in phase with each other. If they are out of phase,
adding a second cab will make the sound thinner, not bigger. This can cause you to crank the amp harder, increasing the likelihood
of blowing speakers....

Sorry to go on for so long, hope this helps.

Good luck & Aloha!

Milan


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