Omni-ish surrounds

[james_e5]

Working on some ideas for my surrounds. Either ND105-4 + ND20FB or SB TWD25. I was thinking of doing something along the lines of the look of Dan N's Duo's except I don't want to mount the tweeted over the woofer if I don't have to. I'd rather mount the tweeters below the woofer like so:



I can prototype and measure, but I want to make sure I'm not making any huge errors before I go through all of that trouble.

Thanks guys...
-j

[rone]

I don't really see a problem, reminiscent of a Shahinian design.
Have Fun! If you cut the slant from corner to corner instead of face to face, you might have room for a tweeter on it.
http://shahinianacoustics.com/Compass-Starter.htm

[james_e5]

Good call. I'll play with the model and see if I can get that to work.

-j

[arlis_1957@yahoo.com]

my guess is they will not measure well on axis. the good news is they dont have to. first and second reflections may do the trick quite well.

[spasticteapot]

Two things to consider:

1. Dispersion from small cone drivers is very wide. Cross over a 3-4" mid at 2khz to an ND28 or similar, and you're looking at pretty much 180 degrees up to the crossover point.

2. Wall-mounted speakers on shallow enclosures with mitered edges have very little baffle step. Aside from increasing efficiency, your crossover gets a lot simpler.

Alternately, you could build some Linkwitz Pluto style speakers. The Aurasound NSW2 isn't too expensive, and the ubiquitous DA175 certainly doesn't have any trouble crossing over at the required 1khz.

[fbov]

I built a passive Pluto clone. My measurements showed that a 5" driver (Silver Flute W14RC25-8) was only truly omni (0 degree = 90 degree) to ~1KHz, driving the need for a tweeter with a very low crossover freq. The NSW2 was the only inexpensive option I found that's small enough, but still crosses that low. (Putting the tweet below the driver gives you many more, and affordable choices.)

In stereo listening, the soundstage is wide and imaging is amazing, but at a cost of efficiency, transient response and frequency extension. It's an engineering tradeoff. I'm using them now as surrounds, and I don't hear any great advantage over a conventional designs in this application.

They really shine in stereo, pulled out into the room, spread wide and toed in so the tweets aim at the listener. Instruments localize well away from the speakers, but in a diffuse area, not at a point like my MTMs, but also without the grunt, sparkle and slam of the MTMs. Tradeoffs...

HAve fun,
Frank

[spasticteapot]

I built a passive Pluto clone. My measurements showed that a 5" driver (Silver Flute W14RC25-8) was only truly omni (0 degree = 90 degree) to ~1KHz, driving the need for a tweeter with a very low crossover freq. The NSW2 was the only inexpensive option I found that's small enough, but still crosses that low. (Putting the tweet below the driver gives you many more, and affordable choices.)
\

The only graphs I see on your thread are for the ND28. Or am I reading it wrong?

Also, have you considered adding a very small (ND16-sized) tweeter? It seems like the Pluto would work much better as a 3-way.

[james_e5]

I'm trying to keep these pretty small. Roughly 5"x5" footprint by no more than about 12" -13" tall. They're going to sit on top of our side tables on either side of the couch.

The couch is pushed up against the wall, so in-wall and on-wall were not recommended in a previous thread I had started.

I went with the nd105-4 and nd20fb because I have them on hand.

I also have these on the shelf:
Tweets
SB twd25
dq25
rs28a (though I doubt I'd use them in a surround)

Woofers
hivi b4n
hivi b3n
aura ns3

I would like to build something with drivers I already have, but wouldn't be opposed to buying more budget level drivers. I mean, you can never have enough of those right?

A single driver setup would also be an option, but I would prefer to use a tweet to fill in the highs.

-j

[fbov]

The only graphs I see on your thread are for the ND28. Or am I reading it wrong?

Also, have you considered adding a very small (ND16-sized) tweeter? It seems like the Pluto would work much better as a 3-way.

That's a HiVi T28; the NSW2-based design is post 3. This was my first design exercise, so there's more learning curve than how-to.

To the OP:
A 5x5x12" box is awfully small. Mine are floor-standers. Have you done any box modeling to see how the drivers react to the available space?

Have fun,
Frank

[james_e5]

That's a HiVi T28; the NSW2-based design is post 3. This was my first design exercise, so there's more learning curve than how-to.

To the OP:
A 5x5x12" box is awfully small. Mine are floor-standers. Have you done any box modeling to see how the drivers react to the available space?

Have fun,
Frank

Looking for an Fb = 80Hz as they are surrounds and I will be using a sub. The nd105 gets pretty close sealed with a passive assist cap. The hivi drivers will make it vented, but not sealed. Also, the DA115 will make it in a vented enclosure.

-j

[fbov]

Unless I'm missing something, you need 7.5l to achieve an 80Hz Fb, but I think you're actually thinking of F3, the -3dB point. That varies strongly with the driver, not the size of a sealed box, so you may well find a suitable combination.

Have fun,
Frank

[james_e5]

That could be true, Frank. I'm at work so I don't have unibox open to look at. I just want to get close to 80 Hz. I'm pretty sure I can get there using a 3" or 4" driver in around 3L.

I know wolfs dragon foal uses the M3N in 3.1 liters tuned to 72Hz. I'm looking to hit something similar to that using a small driver. In fact, the M3N may be worth a look as a single driver option in an omni configuration.

-j

[james_e5]

Question: How high up could a 4" mid cross over in a configuration like the GR Reasearch A/V-O kit? I know it was mentioned previously that the Pluto clone was crossing a 5" woofer around 1kHz.

Thanks
-j