Burned up my Walkabout?!

[ishouldbeking]

No, the tone per se is the same, but the 8 ohm speaker doesn't get an equal share of the power from the amp. Simple physics:

P(power in watts) = I^2(current in amps squared) x R(resistance in ohms)

Essentially, the lower the resistance the more current that is able to flow. This is why a 4 ohm load on the amplifier can produce more power than an 8 ohm load, and a 2 ohm more than 4, etc.

So pairing a 4 ohm 12" with 8 ohm 15", the character of the 12" will be dominant.

Right, I get the math. Perhaps the confusion is over the speakers I'd be using... in this case I've got a 12" combo and I'll be pairing it with an 8 ohm 12" extension cab. Same cab x 2, different power or no, i'm expecting there to be no issues with mismatching.

In the meantime I'll probably stack my 12" combo on top of my 8 ohm 15" Orange cab which I understand could be a little funky (but in all likelihood will sound fine), but it's merely a temp solution til the extension cab arrives.

 

[Colonel Monk]

Of course the 8 ohm has less volume in a stack of 4 ohm/8ohm cabinets! It's getting less wattage than the 4 ohm it's daisy chained to on account of its higher impedance.

That doesn't overthrow Lomo's point.

Lomo's point is that 300W through a single 4 ohm cabinet will have the same useable output as 185W through a 8 ohm cabinet.

My quote snippet wasn't directed at Lomo?

I was making sure that ishouldbeking understood that in fact that there is a volume imbalance between different cabs of different resistance and that, overall, will affect your sound in that the 8 ohm 15" won't be equally blended with a 4 ohm 12".

If all your cabs are 12" this would not be very noticible since the overall tone of the cabs is the same.

Like I said, I have done it before as well - and it worked fine. I was simply adding some volume and the 8 ohm cab was available - so I used it.

I would feel differently about my Scout rig because I want the fatness of the 15" to come thru.

It was kinda implied earlier in the thread that there is no difference between the 4 ohm and 8ohm speakers based on the concept of "usable volume" - if taken literally, then some people might buy an 8 ohm 15" and be dissappointed.

As to Lomo's original point, Yes I see what you're getting at, all variables being equal: Say you wanted to measure the SPL and analyze the sound waves for measureable distortion etc to determine the exact position on the master dial where an 8 ohm and 4 ohm combo hits max clean volume - Like at 4 ohms your max volume is say, noon on the dial and at 8 ohms it's 3 o'clock or whatever it might be....

But I would be really quite suprised if pushed to failure or maximum, whichever occurs first, that you could eek out as much SPL with an 8 as you can a 4. The numbers just don't work out. For the walkabout combo completely maxxed I'm guessing that both voice coils would fail 8 and 4 ohm before long.

 

[lomo]

But I would be really quite suprised if pushed to failure or maximum, whichever occurs first, that you could eek out as much SPL with an 8 as you can a 4. The numbers just don't work out. For the walkabout combo completely maxxed I'm guessing that both voice coils would fail 8 and 4 ohm before long.

I'm not sure what your driving at. For clarity, my point is that beyond the 175 watts the WA will push through a Scout 12, there is no further useful volume gain. Adding the additional 125 watts that become available with the 4 Ohm driver just means you have more power on tap to compress and distort. Apologies for repetition

 

[Colonel Monk]

I'm not sure what your driving at. For clarity, my point is that beyond the 175 watts the WA will push through a Scout 12, there is no further useful volume gain. Adding the additional 125 watts that become available with the 4 Ohm driver just means you have more power on tap to compress and distort. Apologies for repetition

Yes, it is getting repetitive...

What I'm driving at, is that you've made the statement that there is no difference between a 4 ohm Scout combo or an 8 ohm Scout combo based on the notion of what a single speaker can handle, aka usable volume.

You seem to be saying that it's 175 watts maximum, but that is in contradiction of the 300 watts Mesa has on their site for both 12" and 15" Scout cabinets.

So where did this 175 watts come from? Is it just because that's the max output at 8 ohms and you are able to dime the master with 8 ohms, or?

If the speakers blew at exactly 175W, wouldn't that be listed as the Scout Cab's max?

To some extent I think it's an opinion, which we are all entitled to.

I'm not saying I don't understand this concept of "usable volume", but I think your comparisons are your opinion, and thus less than absolutely factual.

If one were to resort to hard science (which is the only way an amplifier company can post the specs of their amps) and I was to input a 1Khz signal from a tone generator into the input of the amp (a common practice for measuring apples to apples amplifier output) and measured the SPL output of the speaker, there is just no way that the 8 ohm scout is as loud as a 4 ohm. Period. In the business, amp techs prefer to use a dummy load and just measure the power output - easier on your ears and neighbors, but I digress...

If you disagree let's just agree to disagree...