Cab Construction - rounded internal corners?

[plumberstrummer]

Hey community -

Feel free to point me to another thread if this is already covered somewhere. I am building a Bass Cab, and keep thinking that the inside edges of the cab should be rounded, only because when we do studio rooms, that is usually a good thing. I do know that it might make the volume calculations a little trickier, but I'm willing to figure it out.

I am also wondering why some of my calves like my Ampeg have all this stuffing inside of it… Is that helpful? It seems like it would make volume calculations a little shaged up, but maybe I'm missing something…

Hoping to get some wisdom here. Any insights are appreciated.. thanks y'all!

 

[agedhorse]

Makes zero difference, if you do the math you will quickly appreciate why (and why no manufacturer does it).

 

[tubedude]

The stuffing attenuates higher frequencies some,.but it also makes the effective.volume larger.
In a cab the main enemy to internal standing waves and resonamces is the parallel walls that make up the box.
If you can avoid these, and make the walls stiff, you'll have a superior box.
I.want a neutral speaker box for the shop, so I can have a reference for guitar amp builds. Seems easier than running an amp through every speaker cab and combo in the shop. It's for a neutral 12" guitar speaker , have it half built. Basically it's a vented box with no parallel walls, coated internally with textured rubberized paint, floated in foam inside a larger external box. Here's a few rough images of the design:

 

[plumberstrummer]

Makes zero difference, if you do the math you will quickly appreciate why (and why no manufacturer does it).

Thanks man! I wish I understood the reasoning, but I will trust you. What about this "no parallel walls" idea ^^ do you think there is anything to it? Again, I know that's applicable in studio design, but not sure if that's apples and plums.

Also, what is your take on stuffing the cab, or placing sound treatment on the walls - is there a reason for any of it? I understand tempering highs, that's ok, but beyond that… stuffing it?

 

[agedhorse]

Thanks man! I wish I understood the reasoning, but I will trust you. What about this "no parallel walls" idea ^^ do you think there is anything to it? Again, I know that's applicable in studio design, but not sure if that's apples and plums.

Also, what is your take on stuffing the cab, or placing sound treatment on the walls - is there a reason for any of it? I understand tempering highs, that's ok, but beyond that… stuffing it?

Acoustic treatment certainly affects the low mids on up, any differences in frequencies below <200 Hz are minimal.

In general, parallel surfaces aren't as much of an issue as many suggest. They are but one variable that contributes to the total performance. Since the box operates more under the pressure model, the reflections are mostly at mid frequencies and addressed by the acoustic treatment.

Note that it's possible to over-treat an enclosure too.

 

[JimChjones]

Note that it's possible to over-treat an enclosure too.

I wonder how that works. When i've overdone it the cab sounded dull and lifeless which is presumably treble being knocked out, but i wouldn't have thought it would affect what the face of the driver is pushing into the room, which to me sounds brightest from the centre of the cone. Or is it that some treble radiates from the port(s) and the damping kills that which is enough to make a difference? The more I learn about this stuff the more complicated it gets.

 

[agedhorse]

I wonder how that works. When i've overdone it the cab sounded dull and lifeless which is presumably treble being knocked out, but i wouldn't have thought it would affect what the face of the driver is pushing into the room, which to me sounds brightest from the centre of the cone. Or is it that some treble radiates from the port(s) and the damping kills that which is enough to make a difference? The more I learn about this stuff the more complicated it gets.

There are multiple reflective paths, including through the cone itself.

 

[plumberstrummer]

Since the box operates more under the pressure model, the reflections are mostly at mid frequencies and addressed by the acoustic treatment.

So, just to clarify - the focus should be on air tightness, venting, and volume. If I want to temper the highs (or you said mids?) I should treat the inside with an acoustic treatment (more treatment = less highs first and then less mids?) ~ However, parallel wall considerations, rounded corners inside, etc., do not matter like they do in recording rooms…

Am I close?

 

[Podgorny]

However, parallel wall considerations, rounded corners inside, etc., do not matter like they do in recording rooms…

Am I close?

Yes, except that rounded corners and non-parallel walls don't matter as much as people think in recording rooms either.

 

[agedhorse]

So, just to clarify - the focus should be on air tightness, venting, and volume. If I want to temper the highs (or you said mids?) I should treat the inside with an acoustic treatment (more treatment = less highs first and then less mids?) ~ However, parallel wall considerations, rounded corners inside, etc., do not matter like they do in recording rooms…

Am I close?

Close.

Reflections is a recording room (studio) involve much greater distances, and the issues being addressed are different.

I said mids because in most cabinets the highs are handled by a tweeter which is not impacted by the inside of the cabinet.