Afternoon all,
I recently picked up a little chinese chimp valve amp and after hearing the limitations of the standard 6" speaker I've decided to follow in this guys foot steps and and put the amp to better use. I've ordered a Celestion G12M Greenback and am now trying to figure out what sort of enclosure to build. I was just planning on ripping off the external dimensions of a Fender blues deluxe or a Blues Junior but without heading into the local music store with my tape measure I don't know how big the port on the back is. does anyone have recommendations? I realize guitar amp enclosure design isn't an exact science but anything is going to sound better than the current 6" speaker.
Cheers guys.
I recently picked up a little chinese chimp valve amp and after hearing the limitations of the standard 6" speaker I've decided to follow in this guys foot steps and and put the amp to better use. I've ordered a Celestion G12M Greenback and am now trying to figure out what sort of enclosure to build. I was just planning on ripping off the external dimensions of a Fender blues deluxe or a Blues Junior but without heading into the local music store with my tape measure I don't know how big the port on the back is. does anyone have recommendations? I realize guitar amp enclosure design isn't an exact science but anything is going to sound better than the current 6" speaker.
Cheers guys.
Are you sure it is a ported back? I think greenbacks work with open back cabinets. Typically there are a couple slats across the back but maybe 50% of the back is open to the air.
I built a cabinet that has three cover across the back. two are fixed and glued in place. The third is removable and has a port in it. I get better bass with the port but the sound is some how filling the room better with the cover removed.
With guitar the lowest note on the open low E string is 81Hz. From a HiFi perspective that is not even "low". Guitars are mid range instruments so cabinet design hardly matters
But if you are undecided it is easy to make a removable cover so you can have it both ways
Cheers mate, when i say ported I had in my mind the large slot they typically have, which would be open back. So I'll start there and play around with different back panels if I don't like the sound 🙂
after a little bit of browsing, i see the Blues Deluxe has a slot port
imgur: the simple image sharer
imgur: the simple image sharer
The theory envolved with a "port" and a slot like that are different.
A true ported cab has a resonant frequency. When something like 1/3rd of the back is open is is just "open" and there is no resonant frequency.
The cabinet sides and any covering on the back is just to keep some the out of phase sound from the rear from mixing with the in-phase sound from the front. With an open back cab like that the room is part of the cabinet. For example set the cab on the floor or a stand or near a wall or further from the wall and the sound changes.
So don't think of a big open slot as just a "bigger port" it is not. It's different physics involved. With an open back the size of the opening is not critical and a lot of it is simply structural. You need to close off some of it to make it strong
Cheers mate, any suggestions for construction material? ply, glue and wood screws are my typical choices.
If you use plywood it must be the void free type. Not the standard construction gave stuff. The best is baltic birch. For something as small as a 1 x 12 cab I'd go with white pine. I like to use finger joints. Then a baffle made of 1/2" baltic birch
I have used 3/4" for many amps, but realized that was overkill for a guitar amp. The 1/2" is really fine for small guitar cabs.
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