Time-Aligned Open Baffle Line Arrays....

[chops]

Right now I'm in the middle of working on my new subwoofer project. (a total of four Dayton 15DVCs in two sealed enclosures with 700 watts)

After I get done with that project, I want to play around with the idea of open baffle line arrays.

In fact, does anyone have some tips on where to buy small (4" and smaller) full range drivers cheap, other than Parts Express?

How about those Jordan drivers? Where do you buy them and are they inexpensive?

I have just started doing a little research on these designs and had a few questions...

1) Is it possible to get good sound from these without any special circuitry or equalization? (running 9 drivers per channel)

2) Since I would be using these on my main system, they would be crossed over at 80Hz, so is it possible to build OB LAs that extend down to at least a usable 80Hz without distorsion?

3) I know that by running multiple drivers you increase effeciency and power handling, so are these designs capable of playing loud for home theater use? (around 100-105dB, maybe 110dB MAX)

4) What about a center channel speaker? Is it possible to build one with the same drivers and have it timbre match the mains, sound natural and "full-bodied" and mounted horizontally?

5) About the center channel still... Since I have a 9' wide projector screen, could I build two smaller center channels and have them mounted above AND below the screen? Or even same size as the main channels? <-- (I prefer this choice - 9 drivers each)

6) About the side and rear surround channels... Using the same drivers still, could I use something like 5 drivers per surround channel in a line array, but in a small sealed enclosure since they would be mounted on the walls or ceiling, and still be a close timbre match to the rest of the system?

And a little info on my system. I have a Pioneer Elite VSX-54TX THX 7.1 receiver with that MCCA Enhanced circuitry which helps timbre match all the channels and provides 100 watts x 7.

Also, as I mentioned earlier, I am in the process of building a subwoofer system consisting of four Dayton 15DVC drivers in two 8 cu.ft. sealed enclosures which will be powered by a QSC RMX850 amp (700 watts per channel @ 2 ohms).

If I build these speakers, they will be replacing a full lineup of Definitive Technology speakers, including:

Def Tech BP10B - Mains
Def Tech C/L/R/ 2000 - Center
Def Tech BP1.2X - Side Surrounds

and Radio Shack Optimus PRO X77 - Back Surrounds

Many thanks in advance for any help!

[Scottmoose]

The Jordan's are in relative terms, very expensive. Because they are very good.

You might want to read Jim Griffin's Line Array White Paper: beware using full-range drivers in an array -you'll get a horrible lobing effect with increasing frequency, because the driver centres, which produce the treble, are too far apart. Also, the likelihood of a cheap[ish] 3" or 4" full-ranger motoring down to 80Hz on an open baffle is about zero squared. Most can't even do that in a vented or TL enclosure. The utterly wondeful Jordan JX92S, or the neat new 4" Bamboo Tangband might be able to do it with massive EQ, but the rest? No chance. Sorry. Box or nothing I'm afraid, and that's ignoring the lobing issues. Also, I reckon an array of 9 4" drivers is a little short, expecially given the fact that they'll need to be mounted as close as you can get them (i.e. surrounds physically touching).

1) OK, can you do it without EQ? Well, yes -if you ignore the lobing and mount them in a box enclosure that should be possible -depends on the driver. In your case, the Tangband's would seem favourite if you really, really want to go full-range. (I love full-rangers, but not in arrays)

2) See above -yes, it's possible to get that low, ignoring the other problems, but only a few 8" + full-rangers can do it. The F200a, Visation B200 etc spring to mind. You'd need a pretty wide baffle though due to the progressive accoustic cancellation as frequency decreases, unless you go for massive EQ

3) Oh yes. No worries there. Most good quality full ranges with decent excursion should be able to achieve that, above all in an array, which means that each driver has to work significantly less hard. Be careful of your hearing though anything over 85db in the long term will damage your hearing.

4) Horizontal array = Bad Idea, in my book due to the dispersion. Jim and some others who lurk arond here can explain that better than me. Just don't bother: phantom centre should handle that. Arrays have stunning stereo imaging and a very broad 'sweet area', not a small sweet spot. Since centre speakers are only there to improve dialogue imaging for off-axis views in home theatre, they've sorted that out at a stroke.

5) See above

6) See above notes about the practicality of small full-rangers on a dipole baffle going down to 80Hz.

I'm not trying to sound negative, but better I mention some of these point now so you can think about them and decide on the best way of avoiding or solving them than you potentially waste a lot of money -arrays aren't cheap!

If you want an array (and so you should!), I think you're going to have to go for a 2 way, and probably in a sealed enclosure to stand a decent chance of getting down to the 80Hz or so you specify. You might be able to scrape it with some 5" drivers on a dipole, but it'd need large side-wings. Here's one that I ran across a while ago, using full-rangers:
http://www.geocities.com/dmitrynizh/labaffles.htm However, insofar as I can see it has numerous issues: I don't like curved baffles as one of the primary benefits of an array -a broad 'sweet area' as Jim calls it, is instantly lost, and it ignores the savage lobing issues which will make for a very ragged response indeed. As such, I can't hand on heart recommend trying to repeat this design or something similar with different drivers.


Cheers
Scott

[chops]

Hi Scott! Thanks for the input so far.

Alright, so I scrap the idea of using full range drivers for the entire array...

1) What inexpensive mid-bass driver would you recommend, in a highly damped sealed enclosure, not OB? (the TANG BAND W4-992S 4" SHIELDED SUBWOOFER maybe, or do I need more midrange output than 2500Hz?) At 20 bucks a pop, that might be getting a little too pricey though.

2) Since I'd be using mid-basses, can I get away with using only 1 tweeter right in the middle of the array, or do I have to use an array of tweeters as well? (I prefer just one to keep cost down)

3) For the center channel, I actually have enough room under the screen where I could fit a vertical array of 4 or 6 mid-basses and a tweeter, and have it angled up a little towards my listening area. I've tried the phantom center before and it was lacking. Voices had a very dull, hollow sound to them. I didn't like it.

4) Since I'd be going with 2-way line arrays, I would need help on designing a simple crossover for the tweeter since I have never built crossovers before. I'm assuming I would just let the mid-basses roll off naturally, or no?

5) If done properly, do you think it's possible to beat the performance of my current loudspeakers all the way around, including volume output?

Thanks again! I'm sure I'll have lots more questions in the near future.

[sreten]

Originally posted by chops

5) If done properly, do you think it's possible to beat the performance of my current loudspeakers all the way around, including volume output?

Hi,

The volume output bit is the easy bit (with an array).

Doing it properly is the difficult (and relatively very expensive) bit.

There is no point in having an array with single tweeters,
the tonal balance will vary badly with listening distance.

The Def Tech speakers seem to be well designed and good quality.

The chances of an amateurs first and large project bettering them
all the way around in every department I would rate as near nil.

If your interested in open baffle line arrays I'd point you towards
Magneplanar's line of speakers, though they do need some serious
juice to drive them, as efficiency is relatively low.

Seems you can try a full front back and centre set up free* for 60 days.
(*edit : well money back guaranteed is more accurate)

/sreten.

[chops]

Nope, already had Maggies before. I'm pretty sure I can make these line arrays work if I put a little thought into them.

[chops]

Originally posted by sreten


There is no point in having an array with single tweeters,
the tonal balance will vary badly with listening distance.

/sreten.

So what could I go with to make this work? And what would the cost be roughly?

I'm not really looking to replace the Def Techs, unless the line arrays come out nice and really do sound as good as everyone says.

Do I really need to go with a huge array or can I get decent results with smaller ones? (5, 6, 7 feet tall)

Would these be any good? I was kind of looking at them earlier.

http://www.partsexpress.com/pe/showd...number=290-302

[Scottmoose]

And money. That's the catch.Because arrays aren't cheap. You can't do them properly cheaply, and if you did, they probably wouldn't be worth listening to. You need a decent outlay sadly to reap decent rewards. That's how it works in the DIY world -we can build spectacular setups, but usually, there isn't much of a cost saving -more a performance gain.

OK, as was noted above, there's little point in building an array with just one or two tweeters, aside from the possibility of upgrading to a full array in the near future, which you'd want to make very near indeed as soon as you heard it!

Right. Arrays. 2 way is best. I'd go for a larger mid-bass myself; a 5 - 5 1/2" would be a good compromise. There's quite a few good ones, here's a Tang Band that should do well:

http://www.partsexpress.com/pe/showd...number=264-850

I really, really wouldn't advise going for very cheap drivers. You'd just be landing yourself with a whole new set of compromises. Now, in an array, it's not a great idea to use normal dome tweeters. Not because they're bad, but because you need so many of the things it becomes very expensive, and also, most have very wide surrounds, which is the last thing an array needs. Ribbons is where you need to be. Here's the cheapest I know, and it's supposed to be very good too: http://www.partsexpress.com/pe/pshow...number=275-085

You'll need to cross over to them at around 2.5Khz, and roll the mid-basses off if they aren't doing it naturally -there are other people here who know more about crossovers than I do, who'll be able to help you with that. Overall, I'd use perhaps 9 or 10 mid-bass and however many tweeters will provide a similar line-length per enclosure. In this case, about 8. If you used these two drivers for example, you'd need to add some series resistance to the tweeter line to bring it's response down to match the TBs.

It's not cheap is it? Wish it were otherwise, believe me! If it was, I would have built a pair long ago!

Cheers
Scott

[chops]

Alright, how about a system that has a 10" or 12" driver for the mid-bass, then an OB mounted on top with something like 3 or 4 Tang Band full range drivers for the upper midrange and treble?

This would still be a 2-way design, but would I still get the open airiness with that kind of OB on the top end?

I want something that will be very nice with vocals but still be able to do home theater duty as well.

I'm just wanting a totally different design for the most part, but have it perform well also.

[chops]

Maybe even something like this... Kinda takes me back to my old Klipsch Cornwalls except simpler and smaller.





Would the Eminence Beta 12LTA be a good choice for this, along with a good tweeter of some sorts?

http://www.partsexpress.com/pe/pshow...09&ctab=2#Tabs

[Scottmoose]

Ah, you've been looking at the Single Driver Site! Good man! And yes indeed -exquisite music-making would not be very far off at all if you went with something like this. You're now very much on the right lines I think, given the limits on budget you refer to. Best option would likely be to simply opt for the Hammer Dynamics Super 12 kit as shown in your top picture. http://www.hammerdynamics.com/ as their drivers have a few worthwhile tweaks over the Eminence Beta-12LT, and John (he died, tragically, early in 2001) really knew what he was doing. If you wanted to stick with the standard Eminence drivers I'll be quite happy to run a MathCad simulation to see what would work best with them. I'll be back in a few minutes with some results. That's a heck of a sub BTW!

Cheers
Scott