Crossover recommendation 411s & 802s??

[bfish]

Didn't GM post some info about the 411 in a ported box a ways back?...

Yeah he did, and I saved it. Originally posted by GM:

"10.34 ft^3 net/Fb = ~21-18 Hz (depending on boundary and/or room gain), 32"h x 25.5"w x 22"d, driver at extreme top, 5" dia x 6-11" long vent 4" up from the bottom (all dims i.d.). Line at least the top, one side and back with 1" acoustic fiberglass stuffing down to just above the vent, though of course you may want more density depending on how well constructed the cab is."

That's not much acreage for planting a 311-90 on, but it sounds like a good idea.

[Art J.]

I thought the 411 would self destruct out of a sealed box.
Controlled X-MAX? Am I incorrect?

[Old Guy]

I thought the 411 would self destruct out of a sealed box.

Not sure why you would think that....

Any speaker will perform in any box. The question is how well.

At the time Altec originally made the 411, the use of T/S parameters and modeling was in its infancy.

Today, with a computer, I can input a speaker parameters and literally have the program design the box. I can the make changes and predict at least somewhat, the results.


What happens is drivers become "displacement limited". In certain boxes, the driver is freer to travel. It will reach xMax much quicker than in another type enclosure. The amount of power required for the driver to reach xMax then becomes the speakers limit.

IE a 300 watt speaker may be "displacement limited" to 100 watts in a certain enclosure, and may handle the full 300 in another. The trick is the box and speaker are a complementary system...if the system produces adequate SPL without over excursion it is a usable design...we also have more sophisticated HP filters than the old days...

I've never actually modeled the 411. So for any deeper explanations consult GM...I am just trying to make a "speakers 101" level explanation. HTH.

[GM]

That's not much acreage for planting a 311-90 on, but it sounds like a good idea.

So I did, I'd forgotten it. 'Rick' wanted a 511/902/411 with more LF gain BW, so this vented variant is what I considered probably the best trade-off between size, BW, and SQ. Don't recall hearing back about it though.

Regardless, a better one overall IMO, though larger, ergo a physically better fit to a 311 or multi-cell is a one fold MLTL I designed for someone and Marty did a preliminary drawing for me to review, but by the time I got to it the interest had apparently vanished, so didn't bother to waste any more of our time on it. It's ~43.75" H x 31.5" W x 25.56" D (o.d.), so only a little bit larger than an 825/828, though of course these dims can be juggled a bit as long as it doesn't shorten the internal path-length too much.

Backed up against a wall, it sims a ~95 dB/m/20 Hz efficiency, so combined with the wide baffle it should have plenty of mid-bass 'punch' and adequate pipe organ symphony capability with good tonal balance once the 311 is shelved down/flattened with CD horn EQ.

GM

[Art J.]

[QUOTE=Old Guy;1780293]

What happens is drivers become "displacement limited". In certain boxes, the driver is freer to travel. It will reach xMax much quicker than in another type enclosure. The amount of power required for the driver to reach xMax then becomes the speakers limit.

Hi Old Guy. Thanks for the good reply.


You made a very important point.
Also I took issue with the Damping Factor. The cone wanted to swing
out of control before its capable power limit. (exceeding x-max). May be worse in another box.

Seemed like they would rather self destruct (bad play on words) unless carefully controlled
by all the external factors. With some awareness and power discipline, distortion could be kept low.
Maybe I'm just being too picky.

[GM]

Also I took issue with the Damping Factor. The cone wanted to swing
out of control before its capable power limit. (exceeding x-max). May be worse in another box.

Hence the need for at least a low Q tuning and preferably in an acoustically fairly large cab if vented. Still, at WFO, some room gain is typically required with all but the highest Xmax drivers to help out in the BW just above Fb if the vent system doesn't provide enough gain, so no good for ~half space loading well away from any walls/corners.

GM