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Jus Lukin
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When I had my old Trace rig I had port mutes (I think thats what Trace Elliot called them) which were cylindrical pieces of foam about 6" long that you could pop into the ports if you wanted. I used to pop them in for a folk act that I did some work with at the time. It warmed up the mids a little and it sounded really nice with my old fretless P.

Ports are designed to increase the air pressure at the front or back of the cab depending where they are placed. Rear ported gives you more low end and front ported gives you a flatter result. Some may argue that front ported cabs give a bit more volume, but I can only notice the difference when I am stood a few feet away from the cab. Any further than that and it doesn't make a huge amount of difference to me.

Closed cabs obviously don't throw out the air inside when the speakers are moving so all of the air pressure happens internally and the acoustic property of the cab becomes part of the tone and sonic effect.

Sealing the ports on a cab is perfectly fine and shouldn't cause aggro with the drivers. I have never had a problem doing so myself with Trace cabs. Speakers do not work in a vacuum, so don't worry about the air pressure causing damage. I have never heard of an amp manufacturer that has designed a speaker for use for a closed cab. They might be voiced differently, but not designed specifically because of the difference in air pressure.

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[quote name='shizznit' timestamp='1356187766' post='1907760']
Ports are designed to increase the air pressure at the front or back of the cab depending where they are placed. Rear ported gives you more low end and front ported gives you a flatter result. Some may argue that front ported cabs give a bit more volume, but I can only notice the difference when I am stood a few feet away from the cab. Any further than that and it doesn't make a huge amount of difference to me.
[/quote]

This isn't how it works. Port placement makes no odds unless you push them against a wall or the back of the cone shows through. There are a resonant device, and reinforce the low end loading the driver, and the low end is not directional.

Plugging ports lowers the tuning of the cab, you don't have to plug them all to mimic the response of a sealed cab, just drop the tuning to below audible. The Barefaced vintage has this option for that purpose.

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[quote name='Mr. Foxen' timestamp='1356196039' post='1907866']


This isn't how it works. Port placement makes no odds unless you push them against a wall or the back of the cone shows through. There are a resonant device, and reinforce the low end loading the driver, and the low end is not directional.

Plugging ports lowers the tuning of the cab, you don't have to plug them all to mimic the response of a sealed cab, just drop the tuning to below audible. The Barefaced vintage has this option for that purpose.
[/quote]


+1

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Hi Andy,

you are right about some speakers being designed to work in ported cabs and others in sealed cabs, you'd generally look for a more compliant suspension and a lower resonant frequency for a driver in a sealed cab. In a lot of commercial instrument cabs though you find a lot of 'general purpose' drivers which wil work OK in either cab. I have no idea what Markbass use.

In all probability the drivers may be just working at less than their optimum as far as the bottom two octaves are concerned and you aren't going to damage them at all. They will in all probability bi in too big a cab to be ideal sealed cabinets and your speakers will be overdamped, a techie term that just means they will start to roll off an octave'ish higher than they do in a sealed cab and then peter out slowly at 6dB/octave as opposed to what they do now, a bit like (but not identical to) turning the bass down a couple of notches.

You've nothing to lose by stuffing the ports full of Christmas socks and trying it but a proper airtight seal would be better if you decide you like the sound. It can work well in a boomy room.

Have fun

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[quote name='Mr. Foxen' timestamp='1356196039' post='1907866']The Barefaced vintage has this option for that purpose.
[/quote]

I've always fancied having a play around with this... there are three (what appear to be) equal sized ports in the front - what effect might I get if I block one or more of them?

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