Center speaker concept

[swirv]

I have been thinking about the center speaker to compliment my mains. I just want the opinion of the group on this concept.

The front mains are crossed over at 6500Hz (series). If I cross the center the same as the mains (ideal) then should I be concerned about comb effects from the two W4's? I tried to get the drivers as close as posible and the dimentions match that of the mains on its side and slightly longer. (7.5"Hx13.5"Wx7"D for 6.5L)

Here is a pic of the concept done in Photoshop....

[swirv]

There is a pic of one of the mains (finished prototype)

[navin]

dont see a problem except that you might want to cosss over lower. 3k would be nice.

[JOE DIRT®]

as Navin said 3000 HZ is ideal....speeech frequency is centred at around 3500 Hz and I take it thats why you want a centre speaker set up is for vocals ie: centre stage

[RAW]

cross it over at 3k
No lower.
The 28-847 or 847S has a fast drop off after 3K nevr mind the posted 600 FS.

Just my 2 cents

[swirv]

Hmm....

Why would I want to crossover at 3k when that is exactly where I dont want a crossover? If the vocal range is centered around that area, why not put the crossover point much higher. This was the idea for the mains. I chose the W4-656S so I could cross much higer. I was under the impression that you didn't want a crossover in the critical vocal range if you could help it. Most 6" drivers break up after 3k so you cross over at or near that, correct? If I'm totaly off base here please set me straight.

And if so would you sugest crossing over the mains at 3k as well?

They sound freakin great right now. Much to my suprize I might add. The crossover is as simple as it gets with no Zoble on the woofer and no pad on the tweet. Keep in mind this was my first serious atempt at HiFi speakers.

Al, what in your opinion is the best crossover point for the two drivers I'm using? I ask because you seem to be the authority on Tangband drivers. You've already been a great help. Thanks in advanced.

And.... just a thought.... but...

Most center content is lopped off at around 7k anyway right? So, do I even need the tweeter if the 656's go up to about 18k?

Chris

[SY]

Vocal fundamentals are nowhere near 3K. MUCH lower.

Six inchers vary quite a bit on breakup characteristics; I haven't used the Tangbands, so can't comment. But they're all six inches, which means that they're starting to get beamy by 3K. To avoid discontinuities in the polar pattern (the "dip and horns" seen in a waterfall display of FR curves versus horizontal angle), you need to cross over at 3K or lower and make that crossover pretty steep- 4th order will work well.

[JoeBob]

The W4s are, I do believe 4 inchers, which are in effect almost fullrange drivers (the ones I've tried, not sure which model swirvis using).

A high crossover point is good for the mains, but I'm not too sure about your center channel, for you are using two W4s, and if they produce the higher frequencies then lobing could occur.

I'm guessing that's the reasoning behind the lower crossover point. But the W4s I've used sounded much better with high crossover points.

[swirv]

Im using the W4-656S 4" Full range driver 65-18kHz. The reason I mention 6" drivers was refrence to the 3k crossover point. You cross 8's at 1k 6's at 3k in general. I crossed the 656's at 6.5k and they sound great.

JoeBob hit on what concerned me most. Lobing. Is it going to be that big an issue? Should I omit one of the W4's? (would make for an unatractive center) I know sound is more important than looks but...WAF?

At what freq am I going to start getting into trouble? These are just 4" speakers and they will be an inch apart.

And if I cross the center at 3k will itl not match the mains sonicly?

Thanks again for the info.

Chris

[JoeBob]

What order are you crossing these over at? If you're using a first order, the use of such a wideband driver is great for your mains, a high and low order crossover gives a great sound.

But for the center, if you've got a low order, then you can get nasties from the multiple drivers even if the xover point isn't excessively high.

What I would do if I were you would be to crossover at a higher frequency (if you've already worked out an xover that you like at 6.5k, use it again), but only do that on one driver. With the 2nd driver, use it to make a 2.5 way, have the 2nd W4 fill in the bass by having it's crossover frequency much lower than the other (obviously, don't just guess, measure and test until it sounds right).