Amplifier Holes?

[nDR01d]

Hi all,
So in December last year I was the lucky recipient of a Marshall stack (2 4x12s and a 100W head). I have no problems with its sound but I do have a question regarding the 4 x 12 cabs. I've always thought that cabs needed air flow, but both of them are completely sealed in ie: have no ports. Is this a 'thing' now? Are Marshall skimping on labour costs by not cutting ports? Should I cut out some section/s of the back of the cabinets? Some thoughts here would be much appreciated. And to be clear, one is angled, the other is a straight cab and both are sealed in. Thanks in advance.

[wokkaboy]

good question Ndriod, I have a Marshall Suoperlead model 1960 cabinet and I don't think it has any air port holes, I will check over the weekend and get back to you.

[dave.king1]

As far as I am aware Marshall quad boxes have always been sealed, I know our guitarist Jeff's 200W Superlead was sealed back in the late 60s and the ones I have seen since have all been sealed.

[wokkaboy]

there must be a reason DK, maybe to keep the dust out of the cabinet but if dust settled on the speakers all you have to do it ark it up !

[DrNomis_44]

That's actually how Jim Marshall (who started the Marshall company in the early 60's) designed the first Marshall Quad Boxes, fully sealed, the only time you ever see speaker boxes with holes in them is when they are designed as Hi-Fi speakers, the hole in the Hi-Fi speaker is what's called a Bass Port, it is designed to extend the low-end of the speaker and flatten-out the response, there's actually a good reason for the Marshall Quad Box being sealed, well two reasons I can think of, it increases the power-handling of the speakers, and it also helps to project the sound out the front of the speaker, you also get that low-end resonance that fattens up the sound too.


Jim Marshall once explained that he put the angle on the speaker cab to make it look a lot more neater and also to beam the sound out to the back of the audience, thus enabling the guitarist to be easily heard.


On the other hand, you have amplifiers manufactured by Fender that have speakers mounted in cabinets with open backs, this produces a very different kind of sound compared to the Marshall sound.

[nDR01d]

That's actually how Jim Marshall (who started the Marshall company in the early 60's) designed the first Marshall Quad Boxes, fully sealed....

....On the other hand, you have amplifiers manufactured by Fender that have speakers mounted in cabinets with open backs, this produces a very different kind of sound compared to the Marshall sound.

Well I guess that "seals" it. Thanks for the mini history and science lesson Dr N. I also like the idea of not having to cut up the back of those beauties.

[dave.king1]

Tthe only time you ever see speaker boxes with holes in them is when they are designed as Hi-Fi speakers, the hole in the Hi-Fi speaker is what's called a Bass Port, it is designed to extend the low-end of the speaker and flatten-out the response

Not entirely true Doc there are plenty of ported boxes, particularly bass boxes ( Markbass & Hartke ) and I think you'll find very few Fender and Vox combos that aren't open backed, even their big bass bins were ported a lot of rich stuff comes off the back of the speaker. Just read the rest of your post

Roy Buchanan used to face his twin away towards the back of the stage in most instances, mic at the front and sound off the rear of the speakers radiating out to the band and audience.

The Marshall box is very directional and if you're off centre they are just loud but get right in front of a fully cranked one and it's like a wall fell on you.

[DrNomis_44]

Not entirely true Doc there are plenty of ported boxes, particularly bass boxes ( Markbass & Hartke ) and I think you'll find very few Fender and Vox combos that aren't open backed, even their big bass bins were ported a lot of rich stuff comes off the back of the speaker. Just read the rest of your post

Roy Buchanan used to face his twin away towards the back of the stage in most instances, mic at the front and sound off the rear of the speakers radiating out to the band and audience.

The Marshall box is very directional and if you're off centre they are just loud but get right in front of a fully cranked one and it's like a wall fell on you.

It's all good mate, I think there's a few factors working together which explain why Marshall amps are so loud, there's the directional beaming of the sound caused by the sealed back stopping the sound escaping, so it can only propagate from the front, there's also the harmonics generated by the Marshall amp when it gets pushed into overdrive, the interesting thing is that the human ear perceives the extra harmonics generated by the amp as a kind of loudness, what's even more interesting is that brass instruments, like the trumpet, Saxophone, Tuba, Trombone, etc, tend to behave in a similar way too, and as it just so happens, the human ear is very sensitive to midrange frequencies, and the human ear perceives midrange frequency harmonics as a feeling of loudness too, I think perhaps when Jim Marshall was working with Ken Bran and Dudley Craven to create what would become the first Marshall amps (the JTM 45s) he might have purposefully chosen to go with a closed back speaker design in order to create the sound that guitarists were describing to him, they wanted an amp that would be loud enough to be heard along with the drummer etc, the JTM45 was actually based on the Tweed Fender Bassman, which was originally intended as a bass amp for the Fender P-Bass, but, guitarists found that it made a great guitar amp.


And you are right too, I have seen a Hartke Bass amp where the speaker box actually did have Bass ports as well as a sealed back.

[stan]

A good basic article on speaker cabs:

http://www.guitarplayer.com/miscella...cabinets/14687

[Kick]

I think the topic title must be 'cabinet holes'