1X12 cab dimensions for G1265

[amplifiednation]

I think you can probably formulate an equation to figure out the 'best size' mathematically, but I've found that through trial and error the ports I like best are approx 1/2 the cabinets overall width by about 1/3 the cabinets height (or shortest dimension)...this is with 1x12 cabinets. I just cloned a Two-Rock 2x12 last week and the port was almost as big as the entire back panel, and that cab sounded great!

The point of the oval port is to retain some lower frequencies that can be phase cancelled with a more open back design. I don't think you can really go wrong, but the right size will help with bass response. Your dimensions don't make sense to me, a 2x12 that is only 22x11?

This was interesting to read:

"The size of the oval port is were a lot of tone shaping comes into play. With a smaller size hole, a cabinet will behave more like a ported cab than an open back cab. Various openings raise or lower the frequency where the rear waves become out of phase with the front and attenuate sound. The right size can add bottom-end extension and smooth out the lower midrange. Both a small oval opening acting like a port and various size oval openings facilitating less phase-cancellation at a lower frequencies, can create more bottom-end. So, various openings create more low-end – just in different ways based on the size."

Credit: http://musicalilluminism.wordpress.com/ ... aker-cabs/

[merkaba22]

I think you can probably formulate an equation to figure out the 'best size' mathematically, but I've found that through trial and error the ports I like best are approx 1/2 the cabinets overall width by about 1/3 the cabinets height (or shortest dimension)...this is with 1x12 cabinets. I just cloned a Two-Rock 2x12 last week and the port was almost as big as the entire back panel, and that cab sounded great!

The point of the oval port is to retain some lower frequencies that can be phase cancelled with a more open back design. I don't think you can really go wrong, but the right size will help with bass response. Your dimensions don't make sense to me, a 2x12 that is only 22x11?

This was interesting to read:

"The size of the oval port is were a lot of tone shaping comes into play. With a smaller size hole, a cabinet will behave more like a ported cab than an open back cab. Various openings raise or lower the frequency where the rear waves become out of phase with the front and attenuate sound. The right size can add bottom-end extension and smooth out the lower midrange. Both a small oval opening acting like a port and various size oval openings facilitating less phase-cancellation at a lower frequencies, can create more bottom-end. So, various openings create more low-end – just in different ways based on the size."

Credit: http://musicalilluminism.wordpress.com/ ... aker-cabs/

Hey thanks for the quick reply ... "the bottom section has interior dimensions of 22w x 11h x 13d" -- so the oval port for this portion of the 2x12 would be 11 x 3.625 (or 7.375 x 5.5) -- does the 13" depth make a difference in this size that you can articulate?

[amplifiednation]

Hey thanks for the quick reply ... "the bottom section has interior dimensions of 22w x 11h x 13d" -- so the oval port for this portion of the 2x12 would be 11 x 3.625 (or 7.375 x 5.5) -- does the 13" depth make a difference in this size that you can articulate?

The calculations I estimate with usually I scale to the outside dimensions, which is usually an additional 1.5", and my cabs are usually taller...so the Taylor equation may not work.

Aesthetically you may want the port to look somewhat oval, and the softer angles are much easier to tolex.

I would go with 10x5 or something around there.

The 13" depth gives you additional box volume, which adds bass, so if anything you could do a bigger port and not lose as much of the lower third of frequencies.

I hope that helps

[merkaba22]

Hey thanks for the quick reply ... "the bottom section has interior dimensions of 22w x 11h x 13d" -- so the oval port for this portion of the 2x12 would be 11 x 3.625 (or 7.375 x 5.5) -- does the 13" depth make a difference in this size that you can articulate?

The calculations I estimate with usually I scale to the outside dimensions, which is usually an additional 1.5", and my cabs are usually taller...so the Taylor equation may not work.

Aesthetically you may want the port to look somewhat oval, and the softer angles are much easier to tolex.

I would go with 10x5 or something around there.

The 13" depth gives you additional box volume, which adds bass, so if anything you could do a bigger port and not lose as much of the lower third of frequencies.

I hope that helps

That helps a lot -- thanks again:)

[amplifiednation]

I'm glad I could help. Thx

[merkaba22]

Hey thanks for the quick reply ... "the bottom section has interior dimensions of 22w x 11h x 13d" -- so the oval port for this portion of the 2x12 would be 11 x 3.625 (or 7.375 x 5.5) -- does the 13" depth make a difference in this size that you can articulate?

The calculations I estimate with usually I scale to the outside dimensions, which is usually an additional 1.5", and my cabs are usually taller...so the Taylor equation may not work.

Aesthetically you may want the port to look somewhat oval, and the softer angles are much easier to tolex.

I would go with 10x5 or something around there.

The 13" depth gives you additional box volume, which adds bass, so if anything you could do a bigger port and not lose as much of the lower third of frequencies.

I hope that helps

Just in follow up, in this thread (https://tubeamparchive.com/viewtopic.ph ... light=oval) there is a Dumble combo 1x12 and the oval seems much larger in proportion to the calcs suggested -- when I did the layout, it looked more like a small version of the 2x12 cabs -- what cha think?

Thanks in advance:)

[amplifiednation]

Yeah I don't think it matters that much, those dimensions are from my own personal experience, not from the Dumble catalog. Remember, once you open the back the cabinet isn't as sensitive to changes. I just know with the dimensions I use my cabs sound awesome so I'm going to keep using them. I like the added punch of a smaller to medium oval port.

Also, I'm sure the ports for the combos is bigger to also allow more heat release/ventilation for the tubes.

What I find to be interesting is Dumbles placement of the port, I've noticed it placed lower on the back panel on several of the original Dumble cabs

[merkaba22]

Then there is this thread: https://tubeamparchive.com/viewtopic.ph ... light=oval

When I evaluate the 9x11.5 oval dimension offered for a 1x12, I get about 86 square inches for the port.

When I use the calc for the area of a 12" speaker using 10.5 cone size, I get about 86 square inches ... interesting.

When I use your suggestion on 5x10 I get about 44+ square inches -- about half ... maybe this works since its size that use as a whole number factor -- like harmonics .... hmmm:)

[merkaba22]

Yeah I don't think it matters that much, those dimensions are from my own personal experience, not from the Dumble catalog. Remember, once you open the back the cabinet isn't as sensitive to changes. I just know with the dimensions I use my cabs sound awesome so I'm going to keep using them. I like the added punch of a smaller to medium oval port.

Also, I'm sure the ports for the combos is bigger to also allow more heat release/ventilation for the tubes.

What I find to be interesting is Dumbles placement of the port, I've noticed it placed lower on the back panel on several of the original Dumble cabs

That's interesting -- how much lower? Is there a calc?