Choosing the right head for Music Man 412B cabinet

[cir440]

Hey guys,

I just picked up a MM 412B cabinet. I want to find the right head to pair with this, but I'm not super sure about what it can handle. I did find a MM catalog from 1980 that lists the 412B as 8 ohms and 150W RMS (p.23/30). However, this other MM catalog from 1983 says the 412B is "power rated at 300 watts" (p.7/8).

How can both of these be true? I do see two input jacks on the back of the enclosure. Is it possible the jacks run parallel so you could run a head at 4 ohms and 300W into both jacks? Is that possible? I'm not well educated on this stuff, and I definitely don't want to guess wrong and end up frying an amp.

Thanks for your help here!

 

[abarson]

Both statements can be true if MM upgraded the speakers used between 1980 and 1983. It's important to find out what you have, as most of today's amps will easily overpower it. Even a minuscule Warwick Gnome is rated as 200 W at 4 ohms / 130 W at 8 ohms.

The cabinet has two jacks, one to use as an input and the other to parallel chain to another cabinet. If you have an amp that can drive 4 ohms, you could add a second 8 ohms cabinet. Never connect both jacks to an amp!

Note that the columns for lbs and kilos in the 1980 catalog are backwards: the 412B weighs 181 pounds. But if you got it home you already know that.

 

[Wasnex]

Another possibility is the earlier documents specifically uses the RMS power rating. It's possible the later document uses the Program power rating, which is 2X the RMS rating.

The RMS rating relates to how much power the voice coil can handle without overheating. At mid-range and higher frequencies the drivers can handle short peaks at 2X the RMS rating providing the long term power remains at or below the RMS rating.

With bass cabs you need to be more concerned with the mechanical power handling below 100hz. This relates to how much the driver is jumping around and it varies by cab design and frequency. Put the same driver in two different designs and the mechanical power handling will typically change.

Mechanical power handling is almost always less then RMS power handling. Sometimes it can be significantly less. This means even the 150W RMS rating may be a bit optimistic.

If you like really heavy lows and have a powerful amp, use discretion and restraint.