How to read cabinet specs?

[BlackhawkRise]

I've finally become good enough in my playing where I'm playing for crowds that my puny little AC10 can't keep up with the volume of the rest of the gang.

I'm trying out combo amps just to get a feel for how they respond. I like the Fender Bassman because it does a great guitar sound and a passable bass sound.

The first question I have is: what's the difference between open, closed, and ported backs?

Second: what's the difference between normal cabs and oversized cabs?

Third: What are the characteristics of 4x12, 2x12, 4x10, and 2x15 and which would be best for my playing of "mostly guitar, sometimes bass?"

 

[beaubrummels]

1. Open back have more bass response, but can be flabby/muddy on the low end. Closed back are tighter and more detailed and often have comparatively less low end. Ported cabinets are tuned to the frequencies needed to get the full range out of the speakers spec'd for the cabinet. That goes out the window if someone replaces the speakers with different ones with different Thiele Small parameters.
2. I don't know what you mean by 'normal' vs 'oversized' cabs. Cabs are always sized for the speakers they hold.
3. 4x12 is a line array, which is designed for clarity over distance. It's not louder, just clearer; the people at the back hear the same sound as the people at the front. It pushes four cubic feet of air, so that column of air and all the frequencies in it will survive a greater distance than a 1x12 only pushing one cubic foot of air, which tends to dissipate within the first 10-15 feet of the stage. 4x12, 2x12 and 1x12 generally all sound the same if they are all closed back and you are close mic'ing. 4x10s IME have a certain midrange "boxy" sound. I only played 15s once and I just remember it being flabby, muddy and unclear; no top end definition.

That's my experience, anyway.

 

[Rex_Rocker]

1. I don't know what you mean by 'normal' vs 'oversized' cabs. Cabs are always sized for the speakers they hold.

1. 
   1x12 and 2x12 cabs are all over the place. I wouln't say there is a clear standard with those, but I would say a "normal", or more like "standard" sized 4x12 is a cab around the size of a Marshall 1960. An oversized is something like a Mesa Recto, a Marshall TV, a Mills Afterburner, etc. Just something sized larger than the standard. And undersized, something like a Soldano, or a lower-end MG, AVT, or Valvestate cab.
   
   It depends greatly on what the construction of the cab is like, but broadly speaking, I'd say the larger you make a cab, the lower the low-end reaches, which I suppose is common knowledge. I'd argue it's not always "more", but rather, "deeper" and placed lower in the frequency spectrum. But I'd also say the high end also opens up as you increase the internal volume of a cab. Don't really know the physics behind it, but that's what my experience has been.

 

[GuitarStv]

This is the best explanation of how cabinet size, number of speakers, and open/closed back change the tone of a cab:

Worth a watch.

 

[jeremy]

this dude has way too much time on his hands, but it was interesting to see the results

 

[BlackhawkRise]

This is the best explanation of how cabinet size, number of speakers, and open/closed back change the tone of a cab:

Worth a watch.

thank you, this is exactly what I was looking for

 

[Sam SG]

Cabinet speakers fall into a couple categories. There are guitar players who just toss a speaker in a a box and listen to the results.
Then there are PA/HI FI type cabs. We're the box is built around the thieves small parameters of the speaker to obtain a flat freq response. Further the port volume is tuned to the speaker. The lower the box tuning the less efficiency of the speaker within the enclosure.
Either way as far volume the spec to look at is peak efficiency for the whole tuned cabinet. Which is the spec of burst wattage. Subtract 6db for continuous efficiency.
In guitar cabs you can look up the efficieeffi@1w 1m of each speaker then add 3db for every doubling of drivers. EI. 4X12 cab with greenbacks, efficiency is 97ea add 3db for 2nd driver then add 3db for 2 more drivers. There for 103db sensitivity @1w 1m
A G12H-30 is rated 100db 1w 1m add three for 2nd driver equals 103db....therefor a 2x12 with G12H-30 would be as loud as a 4x12 with greenbacks.
​​​​​For peak take that calculated sens and add 3db for every doubling of wattage up to the speakers rated wattage handling.
These sens specs are the reason you see a 400W JBL blow the snot out of a cheap speaker rated at 2400W....higher sensitivity and continous wattage vs low sensitivity and an advertised PEAK wattage.....in other words wattage means very little in terms of volune