How ports work! (Not just for bassists - guitarists this is key to the AVD system!)

[@kylebarton6498]

Steady on! Fun gig to design and build your own ideas.. I am building a 1x12 for my mesa 50 caliber head to look like if it was made by them at that time with the black fender grillcloth and such just.. the head’s too big for any of their cabs ;) I thought it would be the way to go to make the back panel boards be one square that fits in the groove like the baffle.. I must have $1000 in labor in it.. but the piece of plywood was free! 😂

[@jimpollard007]

I have also kept that exact copy of bass player magazine - and for the same article. It's gold. Thanks for the clear explanation.

[@TimpBizkit]

I saw Nexo did a slow motion video with a feather on a stick in the port, so you could see the in phase and out of phase regions.

[@BarefacedAudio]

I'll experiment with this, could work well!

[@cjbroz313]

If I'm understanding the explanation correctly, when the speaker and the port are in phase, when the speaker is pushing air out into the room, the air mass in the port is also pushing air out into the room. So the effect is like two pistons pushing air out at the same time. Thus creating sort of a rapid vacuum/pressure cycle within the cab. Then as the frequency drops, the speaker and port gradually go out of phase until at a significantly lower frequency, they are 180 degrees out of phase -- then as one pushes, the other pulls, resulting in somewhat even pressure within the cab and the room, thus not creating the low frequencies we were hoping to achieve. Did I get that right? I've always known that ports could help a cab design and that they could be tuned, but I never quite knew what that meant. Still foggy on how the resonant frequency can get the air to be pushed in & out simultaneously when in phase, but knowing that's what happens is a step up from where I was before.

[@jondoe6062]

As usual Alex, a clear explanation. Presumably, the diameter of the port's hole and the length of the plastic tube within the tube are all part of the tuning process, to optimise the port's effectiveness?

[@BarefacedAudio]

Yes, I shall elaborate on that in a future video!

[@amoontube]

This is my fave so far due to fabulous animation of props - can we have more random objects moving in and out of phase please? (will they phase?) . Perhaps Helmholtz resonant chambers used as tuned absorbers ?

[@SouthernxLord]

So question. Do you guys test all your amps if their ports are correctly working in phase before sending out?

[@BarefacedAudio]

That's not something which needs testing in final QC, it's part of the R&D process. So yes, they're tested when designed and then manufactured to meet those specs.

[@laurieharper1526]

Does that mean we ideally need a high pass filter on amplification which will cut or remove frequencies at the point where the driver and port movements become out of phase? If those very low frequencies contribute nothing to the output of the cab (and increase resonance/distortion components we don't want), it's wasting amplifier power attempting to send them to it.

[@BarefacedAudio]

Lots of amps have some kind of highpass filter or LF roll-off built in.

[@TimpBizkit]

I'm interested in this "hybrid resonator" stuff, wanting to know how it differs from a traditional ported box.

[@BarefacedAudio]

I’ll make a video about this at some point - in retrospect it was sufficiently innovative that I should have patented it!

[@PooNinja]

Love what you’re doing, keep it up 🤘🏽

[@joebasswizard]

Pretty decent explanation! We teach this in undergrad Physics, wrt open- and closed-tube resonance, etc. A question which always provokes disagreement: What difference does a rear- or front-firing port make? (Aside from the leakage explanation you gave here). Or for that matter, any other direction!

[@BarefacedAudio]

Good question with many wrong explanations so that definitely needs a video or two!

[@linguafranca86]

I'm guessing the cab itself has a resonance frequency, the lowest frequency it can produce due to it's size. And then you make a hole that will boost that lowest frequency and just below that it rolls off more quickly. And lastly, to extend the frequency range of the cab to even lower frequencies, you have the length of the plastic tube. Make it too short: it will only make the resonant frequency of the cab louder, Make it too long: it will enhance frequencies that are too weak to be enhanced to the same level of the rest of the frequencies. I may still be missing pieces of my understanding of it. What I don't understand is, how do you determine the size of the hole? I guess that's the next step, before you determine the length of the tube? Anyway, I will watch the rest of the series cause this is realy interesting.

[@fredericgenet1925]

ok, very clear, thank's. Follow up questions : - what make you choose the tuning (size) of the port over an other ? - If you tune the port to resonate at a certain frequency, won't it sound weaker when you don't play in that range ? thank's for all the instructive videos. ;-)

[@BarefacedAudio]

I address some of the first question in the next video (that went up today!) But the other question is a good one too - lots more to talk about in future videos!

[@Gyllbonus]

Is there a reason for no slant in your previous cabs? And also where is the best place for mic placement for live gigs . Does the tube port sound different from a rectangle port directly under the bottom of the cab kind of like bass cabs or will it distort guitar frequencies. Thnx I like your product and I especially like your old prototype w/ the slant.

[@BarefacedAudio]

Good questions, I shall address those in some future videos - but in short we found that once you've got the AVD improving audibility the benefits of the slant baffle become pretty insignificant.