Quote Originally Posted by rogerh113 View Post
I am planning to inside mount the driver for aesthetic reasons, and assume that will not have any substantial impact.

The flared ports seem like a good solution compared to the straight..........

Have you an opinion on side vs front venting? I have heard that music/sound does come out of the vent, and should be directed into the room (recommending front venting). Also heard that various chuffing and breating sounds emanate from the vent, so the vents are better placed on the sides.
Well, at ~7.5 ft^3, it can start demonstrating a bit better than Altec's ~same net Vb cab and of course the room will help, so just a matter of finding the best overall tuning, which may not be the same for both speakers.


While in theory all driver cutouts should be chamfered when rear mounted and many on the backside when front mounted, it's obvious that most manufacturers, DIYers don't bother, but when it's a wide BW one, and especially if there's a coaxial tweeter, then it really should be; and not just a simple cosmetic roundover, but one that knocks it back at least 60 deg. relative to the baffle, then do the cosmetic blending of this waveguide [WG] 'mouth' [terminus] to the baffle and this radius should be at whatever the WG's flare frequency is.


In the scheme of things though, making a 30 deg cut relative to the baffle beginning at .707x the 60 deg's axial length is sufficient. Since even this only gets one a subjective improvement over just making it look smoothed over, virtually no one does it unless the baffle's quite thick.


In kind of short, doing just the 3/4" router bit round over to the cutout serves no useful purpose acoustically, just cosmetically as it still has a theoretically infinite number of the same eigenmodes back where this round 'wall' is still parallel, so at the least, knock it back 90 degs and smooth the outer edge for the cosmetics.


Note that these are included angles, so divide by 2 for bit angle.


How audible this is depends a lot on the person's hearing acuity, SPL, sound source, but me and some others liken it to 'lifting a [diaphanous] veil' from in front of the speaker, which in a way it actually is.


For max effect though, it requires seriously rounding over the cab's corners or at least sufficient foam/whatever to damp its much larger [stronger] eigenmodes and no doubt why Olson horizontally canted the baffle [vertically is less important due to our ears being on the sides of our head].


Note that my vent length suggestions are too short [will tune higher] for flared vents, so will need to take that into consideration.


Contrary to popular opinion, 'music' per se doesn't come out a vent, just its own pipe harmonics and a narrow gain bandwidth [BW] centered at its tuning [Fb] that falls in and out of phase, ergo when tuned down low, we want the vent to have a <0.05 vent mach [< ~17 m/s, though some claim <0.035% = ~12 m/s] to ensure a high acoustic impedance and no vent 'chuffing' from being overloaded. Done this way, the vent can be put anywhere on a typical BR, though with a MLTL it's a bit more critical for best overall performance.


In all cases though, one has to consider any local vertical boundary impact, so in most cases where there's a corner nearby [like < 3x the vent's effective diameter] and the cab/corner's toe'd in included angle is < ~9.5 deg, put them on the front; or if up against a wall, then lower rear corners of the cab to get some free vent corner loading.


GM