Need Port Advice (not wine)

[SJ318]

Hello,
I have a self made 12" V30 speaker box. The wood is 1/2"or so, very hard & firm. It is a square - 15 across, tall, and deep. No baffle, rear loaded, no "damping" (if that's the word"). I read up on porting a cabinet and after reading three separate articles I came away more confused than when I started.
So I would like to port it, but the info talked about sound from the speaker canceling out sound coming out from the port due to "bad" placement. I was thinking of low front double hole ports 1 on each side and/or 1 bigger hole on the bottom to "spread out" the sound on the stage, so to speak. I'll pump about 15-20 watts out of it. Edit: The cab is on wheels, about 3" off the floor.
Would anyone tell me - most importantly, how to NOT cancel out sound and any advice about porting this type of cab as it is?
Thank you,
SJB

 

[SJ318]

Re: Need Port Advice

Re: Need Port Advice

OK,
How about any book recommendations? Nothing too involved. Already read 2 books on how to get a good guitar sound, one on just pedals, can't remember their names but they are industry standards, big coffee table size but soft cover with glossy pages.
SJB

 

[jeremy]

Re: Need Port Advice (not wine)

ported cabs arent all that common for guitars. what benefit are you trying to achieve? porting can help with low frequency response in small cabinets it commson in bass cabs but only a few companies, like thd, make ported guitar cabs.

 

[dystrust]

Re: Need Port Advice (not wine)

ported cabs arent all that common for guitars. what benefit are you trying to achieve? porting can help with low frequency response in small cabinets it commson in bass cabs but only a few companies, like thd, make ported guitar cabs.

There are a few more out there like the Mesa Thiele cabs and Bogner Cubes; my Ear Candy Buzz Bomb 2x12 is also ported. This is done to prevent the 'boxy' sound typical of smaller cabs; a microphone can't tell my Buzz Bomb isn't a 4x12 for example.

The reason the OP can't find a definitive guide is because there isn't one. The correct size and location for a port will depend on the internal volume of the cabinet, the cutoff frequency you're tuning for, AND the speaker used. I don't remember it's name, but there is free software available that can be used to calculate proper port position, shape, and dimensions. The fEARful line of bass cabinets were designed using that software, and the basic process is the same whether designing for guitar or bass.

 

[JOLLY]

Re: Need Port Advice (not wine)

lol....The thread title cracked me up.

 

[SJ318]

Re: Need Port Advice (not wine)

Well,
I want to port the cab so the sound is way more ambient. My idea is that if I port it on the bottom, the sound will go out in all directions, not just like a cannon ball for folks in front of me. also, don't want to port back as this usually drives the drummer nuts.
All I am worried abort is that undefined "mystery" about sound waves canceling each other out, which was pointed out in a book section about porting cabs, but it was too vague to understand- wait I'll go get it...ok, gone 1 minute-"Tone Manual" by Dave Hunter, and "Guitar Tone" by Gallagher (first person to make a watermelon joke breaks a string-Live!). Quote" Sound from the open back, blending with sound from the speaker can blend and cancel each other out, Hunter's book, p. 110-114, he prattles on about how both are bad and good, He should add a fix if he lays out a problem, make up your mind before writing it down. No explanation as to fix any of the problems he mentions with closed or open back cabs.
That is why I think bottom ports would not sail around the speaker box and create the so called out of phase he likes to sound so smart about. I am guessing, and would like a forum expert-there are many, to tell me if that is a good fix
Sorry that was so wordy and long, just wanna be specific, if anyone knows.
Thanks for chiming in,
SJB ps ask if you don't get the Gallagher joke.

 

[SJ318]

Re: Need Port Advice (not wine)

To Jolly-
I was gonna say (not port wine stains), but that sounded crude and personal, not to mention offensive and sooooooooo un-P.C.
SJB

 

[DrNewcenstein]

Re: Need Port Advice (not wine)

Port is left.

Find a square bowl (like the 1+ gallon Tupperware/Rubbermaid type) and put water in it. This is your speaker cabinet. Tap the front of the bowl and watch the ripples, noting where and how they bounce. These are your sound waves from the speaker.

Note the places where the ripples reflect and where they collide with each other. This should give you a rough idea of where to locate your ports.

 

[SJ318]

Re: Need Port Advice (not wine)

Dr. N.-
So where they ripple is where to port? Yes?
Sounds too good to be true, but I know you have been everywhere with guitars, making them, painting them, etc, which leads me to take what you say to the bank. I am always like J.Page in relation to the drummer. So please, If I may ask why port left, and I take it to mean as I look AT the speaker box, the port would then be on my right, and facing the crowd it would then be on my left.
Lastly, no love for my bottom port idea? I also assume on the front of the cab. Still can't sleep, burning up, hoping drugs to kick in in about 30 minutes. This sucks.
Thank You for answering,
Steven John Buffington.

 

[beaubrummels]

Re: Need Port Advice (not wine)

It's a sailing joke. Port left, starboard right. Nothing to do with where a port would go in a speaker cabinet.

dystrust's post matched my understanding. DrN's idea is interesting. I do not have first-hand cabinet builder expertise, only book knowledge on the topic. But I don't think you would want a port where the sound waves cross - I believe then you would just get turbulence in the port. I think you would want the port before the location where waves are about to cross, so that they could exit the cabinet smoothly and freely.

There's a trade off, with a port you'll get more bass response but lose detail and clarity. To make it more ambient, what about a passive radiator?

 

[DrNewcenstein]

Re: Need Port Advice (not wine)

Yeah, it's a sailing joke, sorry.

And like BB said, there's a point where the waves will hit the sides and change direction, and when they change direction they'll head for a crossing point. That's where you phase cancellation will happen. So, knocking a hole in the side will let enough of those waves pass out of the box that the remainder will have less phase cancellation when they collide.

Of course you also have to extrapolate the size of the Tupperware bowl to the cabinet's size.


Bottom porting isn't a bad idea, but I'd mod the bottom of the cabinet so the floor of it is hinged so you can let it down like a ramp of a cargo plane, which will also deflect the sound forward instead of straight down. The resulting delay in the sound coming from the bottom could serve to thicken the tone. Maybe, if you do it like halfway or further back.

 

[Edgecrusher]

Re: Need Port Advice (not wine)

I dont think it going to do what he wants it to. It wont really make the sound go in all directions. He will have ports sending out the frequency that its tuned to in that direction but it wont do that for all frequencies. If he wants more spread he needs more speakers than a 1x12. Particularly if its one the bottom if he isnt after increased bass response its not going to do what he thinks

 

[SJ318]

Re: Need Port Advice (not wine)

Edgecrusher-
Good point on all frequencies not going out a bottom port. Didn't know that. Don't care for more bass or not, just want some spread. Also band leader says NO to more than 1 speaker. No response needed on that. We all know what that is about. Had this conversation on another long thread recently. Seems like Dr. N. has a good point about a hinged piece of wood I could unlatch to drop the wood down or only open as far as I want.
B.Brummels-
What and where do you mean by "port before the location where waves are about to cross". Do you mean a FRONT port on the same plane - on the wood where the speaker hole is-on the front of the cab? Also what in the world is a is a "passive radiator" never heard the term in my whole life.
Dr. N. -
I take it you mean not the front, back, or bottom, but the actual sides. Just to be clear for me, I am in "what the h**l zone". You guys are beyond what I know. So for my "Boss", would side ports, 1 on each side, be good or even better if they are ported close to the bottom of the sides. He would hear them a little less.
Thanks guys for sharing knowledge,
Steven.

 

[Demanic]

Re: Need Port Advice

Re: Need Port Advice

A passive radiator is a diaphragm that moves in sympathy with the speaker, though it by itself is not driven directly by a powered voice coil.

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[Edgecrusher]

Re: Need Port Advice (not wine)

Edgecrusher-
Good point on all frequencies not going out a bottom port. Didn't know that. Don't care for more bass or not, just want some spread. Also band leader says NO to more than 1 speaker. No response needed on that. We all know what that is about. Had this conversation on another long thread recently. Seems like Dr. N. has a good point about a hinged piece of wood I could unlatch to drop the wood down or only open as far as I want.

Yeah you arent picking up what im putting down at all... Top, bottom, sides it doenst matter where you put the port it is only going to vibrate at the frequency you tune it to. The size of your box is going to severely limit your tuning options. If you want people to hear more 80hz that might be possible but it will only spread a narrow band of frequencies. It wont be like spreading all the sound but only a tiny portion of it.

The hinged flap is a terrible idea. You cannot properly tune it. Its the wrong shape... its not sealed... its beyond a terrible idea. The angled geometry of having a drop down flap ruins any tuning you try to do.

IF you want more bass a port might help you. If you want to spread ALL the frequencies of your sound a port is a dead end idea.

The box also NEEDS to be matched the speaker. Guitar speakers are almost always designed for free air.

 

[Demanic]

Re: Need Port Advice

Re: Need Port Advice

Almost sounds like you would be best off just converting it to an open back or half back cab.

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[Edgecrusher]

Re: Need Port Advice

Re: Need Port Advice

Almost sounds like you would be best off just converting it to an open back or half back cab.

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This is actually a good suggestion, a half back cab would let the sound be less directional.

 

[Demanic]

Re: Need Port Advice

Re: Need Port Advice

Found that out by playing around with my 1x12 convertible cab.

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[DrNewcenstein]

Re: Need Port Advice (not wine)

I'm not talking about a little round hole. I'm talking about a mail-slot 4" or more across, almost the full width of the cabinet from left to right (when facing the cone), with a hinged outer panel (not a flap, but a cabinet-sized panel) that deflects the sound coming out of the slot. If you simply open the existing sides/top/bottom, you'll definitely get more sound, but it's going to thin out drastically as it's all speaker, no cab.

Since you say it's 15" across, then I'd say make the slot 12" across, at least 4" wide, and about 3" from the rear of the cab. Do one for the top and the bottom, or on either side, but not one on top and the side. The outer panels would be the same dimensions as the cabinet: 15"x15".

 

[Artie]

Re: Need Port Advice (not wine)

Maybe just aim the speaker either up or down. There have been many speakers designed this way for omni-directional sound.