Open back cabs

matt1973 · August 2014

When it comes to open back cabs, in your opinion, does size matter?

guitarfishbay · August 2014

Amount of drivers still would, and if the cab is semi open the back panel design and structure matters too IME. I've never owned a fully opened back cab to know about those though.

ICBM · August 2014

Yes. The back is never fully open, and the distance round the sides from the front of the speaker to the back also matters.

guitarfishbay · August 2014

True. What I mean by semi open is a top and bottom panel, what I mean by fully open is something like this which only has the amount of panel needed to mount the speaker jack. http://www.bazaar-world.com/uploads/amp/34/320131588560-2.jpg

ecc83 · August 2014

It was found very early on that you needed to block the motion of air pressure changes from the back to the front of the cone or else you got bugger all bass!

The ideal would be a baffle extending to infinity in the plane of the cone but a very good approximation was a speaker in a wall! Naturally some bright spark thought you could just put a speaker in a sealed box but you get nothing for nothing in this world and usually even less in audio! The result was a honky, resonant mess*. The open backed cabinet (as is every radio and telly!) was a fair compromise.

For guitar sound the speakers are big enough and we are unfussy enough that a (leaky!) closed box is accepted.

You would have thought someone would have done a thesis on rock guitar cabs but AFAIK they never have!

*Modern "IB" hi-fi speakers are a special case.

Dave.

Danny1969 · August 2014

Mine's bare minimum backed as I like to store beer and a mic stand in the back so need easy access. I don't even use a jackplate, the wire comes directly off the speaker to plug into my head. There's enough bass in it for me but I'm generally hi passed at 100hz anyway so any more bass wouldn't be used

ecc83 · August 2014

Danny1969 said:

Mine's bare minimum backed as I like to store beer and a mic stand in the back so need easy access. I don't even use a jackplate, the wire comes directly off the speaker to plug into my head. There's enough bass in it for me but I'm generally hi passed at 100hz anyway so any more bass wouldn't be used

Ooo! I hope you have secured the cable so that some drunk tripping on it does not rip the pigtails out of your cones!

Dave.

Danny1969 · August 2014

ecc83 said:

Danny1969 said:

Mine's bare minimum backed as I like to store beer and a mic stand in the back so need easy access. I don't even use a jackplate, the wire comes directly off the speaker to plug into my head. There's enough bass in it for me but I'm generally hi passed at 100hz anyway so any more bass wouldn't be used

Ooo! I hope you have secured the cable so that some drunk tripping on it does not rip the pigtails out of your cones!

Dave.

You can't trip on it Dave, it's exactly long enough to reach the head on top of it and no more

Dave_Mc · August 2014

Probably, but (in my limited experience) not as much as with closed-backs. I.e. I have a convertible which sounds a bit boxy (it's pretty small) with the back on it but sounds good with it off. Which is not to say it might not sound even better were it bigger, too.

matt1973 · August 2014

So I guess the open back is in essence a very large slotted port?

ecc83 · August 2014

matt1973 said:

So I guess the open back is in essence a very large slotted port?

Well I don't know you see, that's why it would be interesting for someone to do the experiments. The very limited work that I have seen suggests that ported cabs with 12" guitar speakers do not behave "classically". I suspect that a lot of this is because the very light cone (compared to a hi fi woofer) is not very soundproof and damps the resonance?

Danny....STILL think the cable should be secured! But then I am a bit anal about such things......

Dave.

bandmaster188 · August 2014

I went for this when I recently built this 15" speaker cab. Initially I wanted it to be closed back but I didn't like how it sounded. So I very un scientifically drilled some holes in the back. I don't really know if its given me a happy medium between open and closed back, but it sounds good and that was the goal. I built it down to a size that would be portable with no real consideration of space and air around the speaker (21"x 22") . To my ears it's almost like playing through a 4x12 but that could be a lot to do with the British voiced speaker. http://i1231.photobucket.com/albums/ee512/bandmaster188/imagejpg1_zps19982b01.jpg

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Open back cabs

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