Yamamoto speakers, rounding of ports?

[oface1]

I have a question on the rounding off of the edges of the ports and speaker edges on these speakers.

Do they serve a purpose, or are they just designed that way for aesthetic reasons?

Thanks,

-chris

[gortnipper]

It is my (novice) understanding that flaring the vent makes it effectively slightly longer and reduces port noise.

An interesting article I read the other day - Ported systems:

David

[GM]

I have a question on the rounding off of the edges of the ports and speaker edges on these speakers.

Do they serve a purpose, or are they just designed that way for aesthetic reasons?

For speaker edges, the radius AFAIK needs to be ~1 WL of the baffle's eigenmode to be acoustically audible. For instance, a 30" wide baffle will have an eigenmode of around 160 Hz, or a ~13.5" radius, so there's only enough flat baffle space left for a 3" driver with both corners rounded.

Some argue that you make the cab's minimum width based on the driver's width, or around 300 Hz for a 16" frame, making for a ~7.2" radius/~30.4" wide baffle, but I'm not convinced. Never having done any serious testing or seen other than Olson's work that I've never seen validated with more accurate test gear either, I can't make any dogmatic pronouncement one way or the other.

Regardless, unless the round over extends back > ~232 deg (if I did the math right) there's still some stiction to the side walls that will in theory cause some anomalies in the response. Then there's the backside shape to consider for minimizing the cab's impact on the rarefaction wave..........

WRT flaring vents, flaring reduces the vent's effective acoustic length and not surprisingly the flare needs to be similarly acoustically large for best results with the point being to reduce the vent's air speed at resonance. The trade-off though is that the larger the flare, the longer the vent required for a given Fb, just like a horn. Note that the flare calculation is the one that some folks use as the argument for the alternate baffle round over calculation with the only difference being how the eigenmode is calculated since the vent has a hard boundary reflection whereas the baffle has lossy acoustic boundaries that make it effectively wider/longer.

GM

[gortnipper]

Oh man, that will take more thought than a couple glasses of wine allows... :-)

[klausesser]

Hi GM!

I realized that rounding the vent?s corners makes the more sense the smaller the opening is. Depending on tunnel-lengths an aditional rounding of the inner opening?s corners might help also.

But that cannot be globalized - depends on the actual parameters.

best, Klaus

[GM]

Greets!

WRT flaring, useful reduction in vent speed only occurs if both ends of the vent are flared and due to the relative size of the flaring required, the internal flare should be flanged also.

Bottom line, it's normally mostly cosmetic in realistic sizes just as Troels Gravesen measured and if there's audible vent noise ('chuffing'), then it's easily cured by using Olson's? 'click' test described in Badmaiff's/Davis's book.

GM

[oface1]

Thanks GM


-chris