Corner radius; countersunk tweeter; ballast

[ro9397]

Main speaker is two-way, will be actively high-pass X'd at 80 Hz (four subs employed ala Geddes/LeJeune), 170mm midbass/26mm soft dome, 2.2 kHz/1st order, 14.75" x 10" x 11.75" (HxWxD).

Three subject questions.

1. The midbass is not flush mounted. To minimize driver spacing for the 1st order XO, the MB is sited so that its mounting flange covers/shadows about a half-inch corner of the flush-mounted tweeter flange.

The MB flange is 5.5mm thick. Purely for cosmetics I am considering countersinking/flush mounting the MB. All else being equal (see above), flush mounting the MB would require the tweeter be cut 5.5mm BELOW the baffle. What if anything can prevent negative audible results from the resulting 5.5mm step between the baffle & the tweeter? (There appear to be NO audible advantage to countersinking the MB.)

2. The prototype enclosure corners are 1/4 round radius (the speaker being cloned had about 3/4 round radius). What is the minimum radius to avoid negatively impacting performance? The builder says 3/8 is the largest radius to maintain structural integrity as currently built. Would 3/8 round improve performance over the current 1/4 round?

3. The enclosure + drivers + XO are about 26 lbs. To minimze rocking & maximize audible performance, I'm considering adding 8+ lbs/1/4" thick steel plate below the base, for 34+ lbs total. The tweeter is below the MB; its flange would be only 2" from the steel ballast plate. To what extent if any might the proximity of the tweeter & steel plate negatively impact audio performance?

TIA!

[badman]

Originally posted by ro9397
Main speaker is two-way, will be actively high-pass X'd at 80 Hz (four subs employed ala Geddes/LeJeune), 170mm midbass/26mm soft dome, 2.2 kHz/1st order, 14.75" x 10" x 11.75" (HxWxD).

Three subject questions.

1. The midbass is not flush mounted. To minimize driver spacing for the 1st order XO, the MB is sited so that its mounting flange covers/shadows about a half-inch corner of the flush-mounted tweeter flange.

The MB flange is 5.5mm thick. Purely for cosmetics I am considering countersinking/flush mounting the MB. All else being equal (see above), flush mounting the MB would require the tweeter be cut 5.5mm BELOW the baffle. What if anything can prevent negative audible results from the resulting 5.5mm step between the baffle & the tweeter? (There appear to be NO audible advantage to countersinking the MB.)

2. The prototype enclosure corners are 1/4 round radius (the speaker being cloned had about 3/4 round radius). What is the minimum radius to avoid negatively impacting performance? The builder says 3/8 is the largest radius to maintain structural integrity as currently built. Would 3/8 round improve performance over the current 1/4 round?

3. The enclosure + drivers + XO are about 26 lbs. To minimze rocking & maximize audible performance, I'm considering adding 8+ lbs/1/4" thick steel plate below the base, for 34+ lbs total. The tweeter is below the MB; its flange would be only 2" from the steel ballast plate. To what extent if any might the proximity of the tweeter & steel plate negatively impact audio performance?

TIA!

1. How about a partial countersink? You can route through the tweeter flange to the appropo depth for the overlap, and keep the tweeter 'normally' flush mounted, while countersinking the MB a little.

2. Not much, but a little. Bigger is better, but moves the baffle step up in frequency a bit when you're talking about the diff between 1" and 1/4" roundovers. You can add material to the inside edges of the baffle/box to allow a bigger, 3/4" roundover, which would be a significant improvement.

3. You're fine. You can ground the steel plate if you like. Make sure it's well coupled to the wood, so it doesn't want to ring.