Holy Grail

[garys]

Ok all you speaker gurus, it's time to go after the holy grail...a low profile DIY center channel.
Low profile (4 to 5" total baffle width..or height in this case).
Power handling (80 to 120 rms).
6 to 8 ohm total (for the guys with cheap amps).
A xo to deal with all the BSC and other problems that come with lining up a bunch of small drivers in a row.
Maybe a tmmmmt or mmtmm, 3" or 4" drivers with a decent low end (70 to 90 Hz).
I've seen alot of great designs I would like to build, but they all seem to be very big (8 to 10" baffle width), and my SAF is to high for a center channel that tall.
Got any ideas ????

[Wolf]

...-193-8A drivers for 87dB/8 ohm nominal, and an Aura NS3-194-8E with notch filter for mid/tweeter @ 87dB/8ohm. I'd use the MM-M&T-MM. -193's from 500Hz on down in Passive Assist alignment of design Q 1.1 sealed and appropriate cap. 400Hz+ to -194 in 1-2 ltr sealed. If you want NS3-194 running lower, then 142Hz Fb ported/stuffed with 120uF cap. Excursion is better in ported alignment. Sound good? 20mm xmax on bass looks good to me!
SAF? We can BEAT it!
Wolf

[unknownuser]

> Ok all you speaker gurus, it's time to go
> after the holy grail...a low profile DIY
> center channel.
> Low profile (4 to 5" total baffle
> width..or height in this case).
> Power handling (80 to 120 rms).
> 6 to 8 ohm total (for the guys with cheap
> amps).

How about starting with the cost of center channel? I doubt that cheap amps/receivers can deliver 120 watts rms into 8 ohms.

> A xo to deal with all the BSC and other
> problems that come with lining up a bunch of
> small drivers in a row.
> Maybe a tmmmmt or mmtmm, 3" or 4"
> drivers with a decent low end (70 to 90 Hz).

Unless you're planning on a real line array, I don't think a crossover can correct multi-driver interference. But then again, I'm not all that familiar with the theory behind the line array.

> I've seen alot of great designs I would like
> to build, but they all seem to be very big
> (8 to 10" baffle width), and my SAF is
> to high for a center channel that tall.
> Got any ideas ????

Why not just have 3/4" tweeter on top of high efficiency 3" mid, and a single 5-1/4" mid woofer next to them; kind a like my old Yamaha bookshelf laid on its side.


(Originally posted by: kyle)

[shawn_a]

> SAF? We can BEAT it!

Ha. Easy to say for a guy who has some monster megalithic sub lurking in the back corner of the living room. The spouse unit is just very tolerant of your toys and your phone bill. LOL.

shawn

[thenoid]

Provided Link: theNoid's DIY Raffle


What size TV do you have? Is the center channel to go on top of it? Is there size restrictions as to the width and depth of the speaker or can it span as wide as the TV, just keep it 5" or under in height...right?

Big question...what's the budget? Assuming we are shooting for the holy grail here I see no reason to have a fincancial cap on the project...or was that just a gesture in joking?

Bigger question...what are your main speakers? Very important to try and match the center channel to the mains.

Noidster


________
INFANT PRILOSEC

[cjd]

> A xo to deal with all the BSC and other
> problems that come with lining up a bunch of
> small drivers in a row.

You're not going to avoid comb filtering unless you go with a TM in the middle (proposed by others already) or a wide-band (i.e. "full range") driver and then cover the lower frequencies with "woofers". I have a 4x4" driver line that runs up to ~3500Hz on the 4" and comb filtering IS a problem.

BSC can be interesting. Is this on a TV? In a bookshelf? Floating in mid-air? Exactly how MUCH BSC you may need is not necessarily a simple answer. Nor will the actual baffle diffraction be. So it'll have to be an averaged design, probably low BSC (assuming it'll be pretty close to a wall if not on a shelf or TV).

For the best bang for the buck, grab a good 3" driver that covers the top end well and round out the design with 2 or 4 4" drivers (how many depends on what impedance they are).

The drivers already mentioned would work great. You can also count the Hi-Vi offerings in this size range (B3S and not sure on the 4's off-hand), as well as Tang-Band. In fact, those new Bamboo T-B's look very promising indeed.

You could add a tweeter above a 3" driver (like that slick Dayton 3/4" dome for $4... excellent piece) if you wanted.

C

[Dirk]

I'm going to speak with a lot of absolutes. Feel free to disgree with me however you want.

Go with a 3-way.

Yes, threee way crossovers are more complex, but MTM, MMTMM, and the ubiquitous TMTMTMTTMQRF designs simply suck for center channels. They do. Unless you sit squarely in front of them (or use absurdly low XO points), they are horrible at clear vocalization. For those who do not watch movies alone, you NEED to have good off-axis response.

Now, if you've built one of the above systems and you think it sounds just fine that doesn't mean it's a sound design to go foisting upon others.

I am a strong believer in WT/MW designs for center channels. By crossing from the mid to the woofers down around 400hz, the woofer-to-woofer spacing is much shorter than the wavelength, so comb filtering is not an option and point-source localization is maintained.

What's the budget like? If low-profile is key, I'd recommend a small 3/4" tweeter (like the little "TM" series Audax neo or maybe the $4 dayton), a 3" driver (maybe one of the TB's with good extension or that aura), and a pair of whatever woofers you can wedge into the space provided. This allows a few different things:

1. Still only a few inches high, and close CTC spacing with the tweet and mid allow for a higher XO point.
2. Woofers near Xmax won't affect the midrange clarity.
3. By crossing near the BSC frequency, you can use the added efficiency of the two woofers to even out the bass responce without sapping more efficiency than is needed. Don't plan on a full 6db of sensitivity mismatch, though, as the TV and entertainment center do increase the effective baffle size (like placing near a wall does).

4. Aforementioned off-axis response.

Oh, and as a side note, if the center channel is above the TV, put the tweeter *below* the midrange.

That is all. Talk amongst yourselves.

[cjd]

> Go with a 3-way.

Why. 3" drivers with excellent top end are not exactly uncommon. Why add a tweeter? I mean, I very likely would consider it but it's by no means a requirement IMO.

Otherwise, your rant is really what I posted, except I may have avoided so much rant. :P

C

[Dirk]

> Why. 3" drivers with excellent top end
> are not exactly uncommon. Why add a
> tweeter? I mean, I very likely would
> consider it but it's by no means a
> requirement IMO.
> Otherwise, your rant is really what I
> posted, except I may have avoided so much
> rant. :P

No, I agree largely, but those 3" drivers with excellent high-frequency extention are still going to beam at high frequencies. They're still cones. Granted, clean midrange is what counts the most in a center channel design. but if there's room for a dedicated tweeter and the additional crossover complexity doesn't scare someone off, I'd still have to think it the "optimal" solution.

> C
D. ;-)

[unknownuser]

(Originally posted by: Brave Sir Robbin)

[kduggan]

[kduggan]

I have an Idea in my head using a 8" woofer in either a ported or band pass crossing over to a deasent 3 or 4 " driver pair at around 300-350 Hz and them to either a Silkie or RS single tweeter. I need a program to model bandpass enclosures that will show response up to 500 HZ or so.

[Wolf]

> Ha. Easy to say for a guy who has some
> monster megalithic sub lurking in the back
> corner of the living room. The spouse unit
> is just (very) tolerant of your toys and your
> phone bill. LOL.

> shawn

She knows about the bill.
Later,
Wolf

[shawn_a]

> She knows about the bill.
> Later,
> Wolf

For every project idea you have. Including late night brainstorming sessions via Ma Bell. Man how I love my cell phone plan....

shawn

[Wolf]

> For every project idea you have. Including
> late night brainstorming sessions via Ma
> Bell. Man how I love my cell phone plan....

> shawn

She just always says "No more speakers", and you obviously know how that turns out. She buys clothes/shoes pretty frequently too though.
even-steven.
Wolf