Tom Campbell
From:
Houston, Texas, USA
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Posted 8 Oct 2014 4:54 pm |
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I have a Peavey 112SX extension cabinet 23x19x11. I am installing a Peavey 12" Scorpion (8 ohm) speaker in it...and will drive it with a NV400 head.
The cabinet has the option to remove the back panel (i.e. open back) or use it as a closed back cabinet. If I leave it as a closed back cabinet, will it have a significant effect on the 12" Scorpion speaker? Or is this a case of needing to port the cabinet if I leave it closed back? |
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Steve Collins
From:
Alaska, USA
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Posted 8 Oct 2014 8:31 pm
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Depends on what you want. Generally speaking, open back cabs will be brighter sounding, accentuating the highs. They will be more omnidirectional, and sound pretty well-rounded, natural. Low end can be a bit attenuated and less defined.
Closed back cabs will be much more directional, not as much sound out the back and sides. They will have a greater emphasis on low end, and give the midrange an almost compressed sound.
Ported cabs can have the best of both worlds if they are done correctly, but the size, length, and placement of a port (or ports) must be engineered to exacting parameters for the port to work properly. A hole punched randomly in the cab just won't do.
Since you have a removable back try open and closed, see what works for your sound. |
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Godfrey Arthur
From:
3rd Rock
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Posted 12 Oct 2014 3:26 pm
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Ported speaker cabinets are calculated in conjunction with a specific speaker. Ports by themselves are not really that accurate, are done to achieve "better" bass response, read "a quick fix" to present the appearance of bass response. There then comes the issue of port noise and the fact that the port is creating a faux bass tone, not the speaker.
Taking a speaker designed for a certain environment and then expecting a specific performance in that other environment is hit and miss.
You must know your speaker's specs and where you plan to install that; cabinet, size, type.
Best to chose a speaker designed for the size/type cabinet you plan on using, your specific useful frequency range of your musical instrument and the amp head's wattage rather than arbitrarily installing just any speaker into that particular cab.
Open back, what happens there is a phase cancellation of lower frequencies as they wrap around the cabinet knocking each other out, front wave/rear wave cancellation, leaving the upper frequencies to "stand out" as it were.
A closed back, prevents the open back wave cancellation phenomenon, creates a compression effect, needs a larger wattage amp, while a ported or vented cabinet will get by with less. Think Ampeg SVT, a sealed 8x10 enclosure that uses a 300 watt head for bass, which is the industry standard live gig stage bass amp, producing a tight, low reaching controlled bass tone. And the speakers chosen for this type cab were meant to be in sealed cabinets.
A ported enclosure tends to be unruly creating overtones where you don't want them.
Trying to port your Peavey extension cab will need Thiele-Small calculations, the right port size, tube length if you end up using one, given a specific speaker, if you want to do a better job on your planned project.
You can find free speaker cab calculators online. The better specs you can find for your given speaker, the more accurately you can predict your end response using those calculators for your cabinet.
But you may find out your speaker does not lend itself, to just any cabinet type and may be a one-trick pony.
You may need to choose a path.
What is your priority?
Using that particular extension cab?
Or that particular speaker?
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