Mark IV help with Ampeg cab

[lagarto]

I've read all I can, yet still feel ignorant--I have an Ampeg cab with 2 jacks--says "stereo" on the back by the jacks , and each jack is rated @ 8 ohms. On my Mark IV combo, I have 2 - 4 ohm jacks and 1 -8 ohm jack. Question: to connect the Ampeg cab, what are my choices, and what would sound the best? Can I run one line from one cab jack (8 ohms) to one of the amp's 4 ohm jacks, and one line from the other 4 ohm amp jack to the 8 ohm cab jack? Or...can I / should I only run a line from the 8 ohm cab jack to the single 8 ohm on the amp (which leaves the other speaker unused I'm assuming). I would like to use both speakers at the same time, but in a smaller gig, only using one of the cab speakers would be nice too- but my main concern is connecting for both speakers...

 

[Russ]

I am assuming you plan on not using the combo speaker.

If you want to run the entire Ampeg cabinet using both 8 ohm jacks on it then be sure to plug them into both 4 ohm jacks on your chassis. This is what was told to me when speaking with Mesa about my MarkIV head. Do not plug anything else into the 8ohm jack on your chassis as you will create too low of an ohm load and ruin your amp.

If you only want to run one of the jacks on the Ampeg (two speakers), then plug into the 8 ohm jack on your chassis to match your ohms.

If you have an 8 ohm speaker in your combo (as you should), I would suggest using the speaker in your combo in a 4 ohm jack and one of the 8ohm jacks of the Ampeg cabinet. This configuration will allow you to aim that combo at yourself as a monitor and fire the 2x12 (of the 4x12) wherever else you want.

If you mismatch up you are ok but if you mismatch down you are in trouble. This said, if you have a 16 ohm cabinet feel free to plug into the 8 ohm socket. This will sound a little darker but wont hurt anything. Unfortunately as was explained to me you cannot run anything else if you are doing this though because you will present an odd ohm load that doesn't work for your amp. The other side of the coin is that if you hook up a single 4ohm cabinet you are also finished there. Any further connections would reduce your ohm load below the minimum and you will fry your amp.

Connecting your stereo sides of your Ampeg cabinet will not produce stereo in this sense but will act as a mono cabinet in a 4 ohm load. To truly take advantage of the stereo effect you would have to have a separate amp powering the other side of your signal to the other side of the cabinet. I would not suggest this either because stereo sharing a cabinet doesn't give you the stereo soundstage that you would expect from stereo sound. In order to take advantage of the stereo effect you would want to spread your speakers far apart to gain a real feeling of stereo. Just think of how far your stereo pan would go in the same cabinet vice across a stage. Stereo cabinets are nice if you share a cabinet with a second guitarist because you can get both setups going stereo. I prefer the mono cabinets though because you get phase cancellation and cross-over distortion at points with certain frequencies being played in the same cabinet unless you subdivide the cabinet inside.

 

[Russ]

I almost forgot, if you play the one side of the 4x12 as a 2x12 you will not see much volume difference than if you had played it as a 4x12 because you will get passive movement from your nonpowered 2x12 thus creating sound anyway. If it is a concern to play quieter playing 2 of 4 in your cabinet won't do a whole lot.

In addition to this, the only difference between 1x12-2x12-4x12 is the amount of air you move. It may sound fuller but if that 1x12 beams you then it will be just as loud as if it had been a 4x12 just not perceived as so.

Yeah a stupid doorman that isn't allowed to let you in with a 4x12 might buy the just playing 2x12 of the 4x12 but it is still going to be loud.

If you really get into the whole thing then you will find that the only difference between 50 and 100 watts is in the single digits of decibles granted the 50 is already close to 100 decibles anyway but you are getting a small percentage louder. The loudness is not doubled. For that matter you might be able to get away with a 30 watt amp or even a little 18 watt amp. If you think along these lines then it makes the manufacturers selling points look stupid. They market to a population that doesn't think along these lines. The biggest difference is headroom in amps not loudness. If you can get your amp to reach a louder point before losing clarity or if you want your amp to break up sooner is all that you should really be looking at. You can also play with your speakers like this too. Some will handle so much wattage and others will handle less. The more power your speaker will handle the more power you can put to it before it breaks up. This is what makes the greenbacks popular along with their voicing. They are 25 watts and begin to break up fast. The same can be said about the ev 200 watters out there on the other side of the coin. Those are clear without speaker breakup because there aren't many amps out there that can push them hard enough. They too have a distinct voicing.