828 cabinets?

[rontec]

Attachment 1276I was just given a pair of home made cabs possibly clones of 828a? I have some 511b's with 808 8b's.
And I can also fit them with 821 woofers. I will probably try bi-amping.
My questions are, what is the difference in mounting the 511b's on top vs. inside the cabinets?
When the horns are mounted on top is the opening at the bottom blocked and sealed?
And finally, can the cabs be modified in anyway such as turning them into subs?
Just trying to figure out the best path to take with these monsters!
thx Ron
http://www.lansingheritage.org/image...-mi/page13.jpg

[bowtie427ss]

My questions are, what is the difference in mounting the 511b's on top vs. inside the cabinets?

IMO, top mounting as originally intended has 3 advantages over inside mounting the horn. a) the horn resides at a typically closer to ear level location. b) it gives the closest mounting proximity to the LF and HF sections getting as close as possible to a point source. c) the horn mounting rail/bracket doubles as a brace/stiffener for that otherwise unsupported horn panel.

When the horns are mounted on top is the opening at the bottom blocked and sealed?

There needs to be a port for the box to function properly in bass reflex mode(below ~100hz), port dimensions are a somewhat debated topic.

And finally, can the cabs be modified in anyway such as turning them into subs?

Some folks swear by closing up the bass reflex portion of the box, sealing it off from the midbass horn driver, and loading the bottom with JBL 2245 or similar. My brief listening experience with this setup was not nearly cinvincing enough for me to hack up a decent pair of cabinets regardless if they're DIY or factory. IMO, subs belong in their own box.

It's also my opinion that some useful LF reinforcement can be gained by bracing the larger panel areas and tightening the box up, it's rather flexible in stock form.

Just my .02...............................

[rontec]

Thanks bowtie427ss. Good info!
BTW, I meant to say 421 woofers in my original post.
If the 511's are mounted on top, the bass reflex port opening is approx. 9" x 28".
Would this be anywhere close to ideal?
thx again.

[Old Guy]

Was wondering if you meant 421 or 921...similar actually.

Port is way too big.

There are previous discussions here about the ports...maybe do a forum search...hopefully it will work...

Bowtie is spot on, tap on panels, if anything but a dull thud brace away.

[rontec]

Yeah - I thought it was too large of an opening for a tuned port.
I guess when the horn is mounted inside the cabinet the port opening size
will change again because internal volume has been changed with the volume of the horn.
I'll try a search of port openings for cabs. Thanks OG.