Scrappy Off Axis Response *PIC*

[curt_c]

Below are the measured response plots at 0, 15, and 30 degrees off axis. -Vertical in a 'normal' orientation, or Horizontal as a center channel.

Not as bad as I'd feared. (Note the expanded vertical scale.) While not ideal by any means, I'd say it would be tolerable as a center channel. The B3N's could be pushed together about a half an inch from the original design, and this would help some as well.

[nick29498141]

So you think putting some felt type material around the baffle would help to smooth things out, especially in the horizontal configuration?

I know this is a on-the-cheap project, so I'm thinking about some of my favorite "Cash Strapped" tweaks.

NK

[waynew]

> So you think putting some felt type material
> around the baffle would help to smooth
> things out, especially in the horizontal
> configuration?

> I know this is a on-the-cheap project, so
> I'm thinking about some of my favorite
> "Cash Strapped" tweaks.

> NK

Bear in mind that the vertical scale was expanded, so what looks really really ragged, is actually about normal for most speakers. No need for felt IMO.

[romanbednarek]

> Below are the measured response plots at 0,
> 15, and 30 degrees off axis. -Vertical in a
> 'normal' orientation, or Horizontal as a
> center channel.

> Not as bad as I'd feared. (Note the expanded
> vertical scale.) While not ideal by any
> means, I'd say it would be tolerable as a
> center channel. The B3N's could be pushed
> together about a half an inch from the
> original design, and this would help some as
> well.

I'm not familiar with the design but it seems to be a 2 way MTM. I've always felt that 2.5 way MTM designs were superior with off axis performance horizontally when mounted horizontally as a center channel because the issues with comb filtering are eliminated. In the end you basically just have a TM design on its side so all you are dealing with is the phase alignment between the tweeter and woofer. In either case (2 or 2.5 way) a lower crossover frequency improves the off axis performance.

[jims]

Curt,

I looked through the threads below, including your x-o posts, but I couldn't find anything on the cabinet size/design. Could you post it or point me to it?

Thanks!
Jim S.

[curt_c]

Nothing drawn up yet, but this should get you going:

(Sounds of tape measure going snick, snick, snick.)

The outside dimensions are 14"h x 6"w x 8"d. The tweeter center is 7" from the top/bottom and laterally offset .75". The woofer centers are each 4" in from the top/bottom and centered on the baffle. The panel thickness was .75" (the solid oak and cherry are optional) and the edges of the baffle had a .5" 45 degree bevel. No internal bracing was used nor IMO, is it required. The enclosure was sealed and lightly stuffed with polyfill.

Wayne or I will draw up something soon, and I'll post it on my site along with the rest of the info.

C

[curt_c]

I agree with all points. This was not originally intended to be a center channel, so I saw no reason for the additional complexity of the 2.5 way topology. However, since I've got all the data, perhaps I'll model it and see what improvements can be made.

I will point out that a 2.5 way CC will have non-symmetrical horizontal off axis response.

C

> I'm not familiar with the design but it
> seems to be a 2 way MTM. I've always felt
> that 2.5 way MTM designs were superior with
> off axis performance horizontally when
> mounted horizontally as a center channel
> because the issues with comb filtering are
> eliminated. In the end you basically just
> have a TM design on its side so all you are
> dealing with is the phase alignment between
> the tweeter and woofer. In either case (2 or
> 2.5 way) a lower crossover frequency
> improves the off axis performance.

[jims]

> Nothing drawn up yet, but this should get
> you going:

> (Sounds of tape measure going snick, snick,
> snick.)

> The outside dimensions are 14"h x
> 6"w x 8"d. The tweeter center is
> 7" from the top/bottom and laterally
> offset .75". The woofer centers are
> each 4" in from the top/bottom and
> centered on the baffle. The panel thickness
> was .75" (the solid oak and cherry are
> optional) and the edges of the baffle had a
> .5" 45 degree bevel. No internal
> bracing was used nor IMO, is it required.
> The enclosure was sealed and lightly stuffed
> with polyfill.

> Wayne or I will draw up something soon, and
> I'll post it on my site along with the rest
> of the info.

> C

Thanks! Looks nice.

Jim

[will_in_pc]

Any chance the buyout hivi (299-122) can be used in place of the b3n? My mother-in-law doesn't want a non-black cone :-/

> Nothing drawn up yet, but this should get
> you going:

> (Sounds of tape measure going snick, snick,
> snick.)

> The outside dimensions are 14"h x
> 6"w x 8"d. The tweeter center is
> 7" from the top/bottom and laterally
> offset .75". The woofer centers are
> each 4" in from the top/bottom and
> centered on the baffle. The panel thickness
> was .75" (the solid oak and cherry are
> optional) and the edges of the baffle had a
> .5" 45 degree bevel. No internal
> bracing was used nor IMO, is it required.
> The enclosure was sealed and lightly stuffed
> with polyfill.

> Wayne or I will draw up something soon, and
> I'll post it on my site along with the rest
> of the info.

> C