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Any opinions on ported speaker cabs vs. non-ported speaker cabs? I just built a couple of 1x12 speaker cabs to go along with my Marshall 9005 power amp and I have have wondering about porting the cabs or not.

Here's what Celestion has to say on the subject:

<i>"Guitar speakers are not recommended for use in ported cabinets (as the increase in cone excursion below the tuning frequency can cause the thin paper edge of the cone to tear)."</i>

OTOH, I have heard people talk about their ported cabs that sound "less boxy", etc., etc. Would a ported cab sound better with particle board construction than otherwise?

Any opinions on any of this?

EDIT: Add to that "to stuff or not stuff". I have heard arguments for both? Anyone have some experiences they'd like to share on the matter?

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PJM

http://www.diyguitarist.com

I like the sound of the semi-open back cab with Alnico speakers. But I also have 4X12 Marshall closed and have heard Bogner ported.
I think the choice of speaker is most important anyway, then make the cab around it. FWIW, Open backs outsell closed backs significantly.

Not sure if Clestion includes open back in their discussion, but, they are in a way, ported. If you tune the port to a low frequency, you could risk the driver at loud volumes I guess. But you don't have much need to get into those low frequencies with a standard guitar, do you? You're not playing bass, right?

For a robust cab, I'd always go with Ply. I don't think there is much, if any tonal differance with 'good' particle board.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

That's my feelings, too. The thing with my speakers (Celestion G12S-50) is that the resonant frequency (Fs) is around 88Hz, so with the speaker by itself in a cab sounds a little lacking in bass dept. That's why I'm thinking that porting the cab may help to improve that. I'm not looking for thunderous bass, just a little more bass. (BTW, I'm mainly a guitar player, and that's what I'd by using the cabs for) They do work together better in a 2x12 configuration (more bass), but I have them in seperate cabs for use in a stereo rig. It's not like I am real unhappy with the way that they sound, I just think there is some room for improvement.

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PJM

http://www.diyguitarist.com

You could make a new split back. 1/3 open and see if that helps at all. If you ported, you would have to design the port for the vol & res frequency for that Celestion G12S-50. I don't know this speaker, but if Celestion says it should be in a closed box, then it must be loose compared to open back speakers. I guess you could get into some problems overdriving it.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

Well, maybe. The Celestion site basically frowns on using any of their speakers in a ported cab. I don't think it would be a problem since I wouldn't be driving them that hard. A 1/3 open back is an interesting idea though.

EDIT: BTW, these speakers are from the very early 90s, and they do sound really good. I pulled them out of a ADA 2x12 1/4 stack cab.

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PJM

http://www.diyguitarist.com

Well, I went with the port idea. I found a way to add "a port" to my existing speaker cabs. Instead of one 4" round port, I went with two right triangles with the equivalent cross sectional area of a 4" round port below the speaker. This way, they fit in the space that I have to work with. It definitely improved the bottom end in this case. I made the ports out of 1/4" plywood and beveled the edges and glued them together and to the speaker baffle with some TightBond wood glue. Check it out:







The ports mesure 3.5"x3.5"x 5"x3" deep. So far, the shape of the ports haven't been the cause of any problems.

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PJM

http://www.diyguitarist.com

That's an interesting concept, Paul. Did you experiment with the depth of the triangles or just pick a length that looked good? If you just cut the ports without the extensions do you think would it change the sound much?

A friend wants me to build him a 2 X 12 cab with 2 Vintage 30's. Any opinions on closed back versus open or partial? I'd rather do a closed back and I like the idea of the ports.

Moid

No, I didn't experiment with the length of the ports. The two triangular ports have the same combined equivalent cross sectional area and length of a 4" round port, which would tune the cab at approx. 55Hz. I don't think just a hole would do the trick, though. The port has to also have a certain depth to it as well...

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PJM

http://www.diyguitarist.com

Yes there is a formula for determining the 'volume' of the port. It takes into account the tuning you want, the resonant freq of the speaker, cab volume, otherspeaker parameters etc. I can dig it up for anyone who wants it.

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Stephen
Web: www.trinityamps.com. Facebook: facebook.com/trinityamps. Twitter: @trinityamps

An idividual that I trust at another forum I frequent helped me out with my port sizing. The hard part about designing cabs and ports is that you don't usually ever get the full specs on a guitar speaker, so you either have to take a guess at some things, or measure the speaker parameters yourself.

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PJM

http://www.diyguitarist.com

Stephen,
Could you please send me that info on the formula. Thanks

Moid