Closing an open combo amp

[cwebb]

So I have a peavey ultra 112, it is open backed, I was wondering if getting some wood and closing the back would improve its sound quality a lot or if its not really worth the effort? also unrelated, but in the future I intend to swap out the stock sheffield 1230 for another speaker, the styles I play are metalcorish stuff and classic rock but I also play at church so I still need excellent cleans! I was thinking a v30 or something what are good speaker recoomendations?

 

[beaubrummels]

Re: Closing an open combo amp

You need to look up the Theile/Small parameters for your speaker before you do. Speakers are engineered to have a specific amount of airspace behind them. Closing off the cubic air behind a speaker and putting back pressure can negatively affect performance and frequency response.

In general, open back will have better bass response but lack detail in high end transients - because the speaker (magnet in the coil) is free to travel it's full distance uninhibited by back pressure of an enclosed cabinet. Closed cabinets will have tighter low frequencies and more detail but lack the really deep low end, because the dampening caused by the closed cabinet will shorten the settling time of the transducer (the magnet in the coil) making it better able to reproduce bright details, but you will sacrifice low end because the speaker will be prevented from exerting it's full throw to reproduce the bass.

v30 or Alnico Blues are capable of what you need, based on your description. If Celestion Alnico Blues are too expensive, there is a Weber equivalent that is very good.

 

[Dr. Vegetable]

Re: Closing an open combo amp

The other big difference you'll get if you seal the back of the cabinet is that the sound will be more directional. An open-back cab will be heard more evenly all around it, while a closed back cab will have more of a lobe out in front of it. Open back is good for letting the whole band hear you without monitors; closed back is better for projecting the sound in a particular direction.

 

[Rich_S]

Re: Closing an open combo amp

Closing off the back of a combo is going to cause heat problems. Also, most combo amps are designed to be compact, and their cabinets are smaller than what the "correct" design of a sealed-back cabinet would dictate.

If you want to experiment and hear the difference between open- and closed-back designs, you'd be better off installing a remote speaker jack (if you amp doesn't already have one) and then driving a different cabinet with your amp's "head".

 

[jeremy]

Re: Closing an open combo amp

alnico blues are nice speakers but only 15w

ultra 112 is tube, yes? if so do not close off the cabinet or you will cook your amp

 

[cwebb]

Re: Closing an open combo amp

yeah its tube, ok I wasn't sure if i could or couldnt, I know the 5150 combo had a closed back to give it more of the stack tone, I have experimented with it and my 4x12 and it changes the tone quite a bit even for a really cheap 4x12

 

[cwebb]

Re: Closing an open combo amp

Oh and as for outputs I have noticed most of peaveys combo amps are made like heads with a cab attached, as in the speakers aren't directly connected but they have 2 or more outputs and the speaker plugs into one of those with a 1/4" connector, so it has 2 outputs essentially its a head with an attached 1x12. Also being that it is a tube amp but it's not a stereo amp is it ok to use whatever output for running it with just one cab, or do I still have to only use the left? (it doesn't have any of them labeled it just has 2 outputs and an impedance selector between 4 8 and 16)