Sub-woofer for line array.

[jerryo]

I am looking at a few different ideas for some speaker designs, one of which is a line array using 8 x 4" fullrange ( per channel ) drivers. These drivers should be OK down to 150-120Hz so now I need to fill in the rest down to 20Hz. Space is tight, I do not need high volumes but accuracy is important. I was wondering whether it would be possible to build stereo subs using sealed enclosures to operate reasonably from 150-20Hz? Would the Peerless xls range be suitable? I am building quite a powerful pair of mono amps so would like to use these for both the line array and the subs if possible. Any thoughts would be very welcome. Cheers.

[Pikefish]

Here's the one problem with this proposal, comb filtering in the higher frequencies, having high frequency sources a little over 4" apart is bad some say, but I've never seen it measured. Commonly a shorter array of closely spaced tweeters is used beside the mids, but you want the fullrangers, maybe look in the Fullrange forum for a line array.

As far as the sub goes, yes that's totally do-able since you have the power, you might want to build in/buy a linkwitz transform if you're going sealed, and pick a Qts for what kind of stuff you'll mainly play. Those Peerless XLS subs are usually pretty good into the hundreds.

One big hurdle could be the difference in sensitivity of the subs and the large number of highs, but you could well match them up by wiring the fullrangers to have a higher total impedance, if there's 8 of them at 8ohm you can do 16ohm, whether that's enough is debatable, so then there's attenuation. A more elegant solution is bi-amping, since most of your power will go to the subs, and not so much electrical power is needed above there, but that can set fire to the ears of someone building an amp, so let's post some details for the fullrange drivers in mind and see how things go from there.

[jbell]

I agree on the 4" full range line array -- you won't like it. I've built some line arrays like this with some boston 4" full range drivers. At 4" you can 'barely' make 2.5k to meet up with the average tweeter. (I used #275-035 tweeters in mine)

Here's a good review using 2" full range, and he had big problems with comb filtering and high end drop off. You need a line of tweeters, if you are going to listen to music at all with this.

http://www.partsexpress.com/projects...oject=Kuze3201

[jerryo]

Hi jbell and Pikefish, thank you for your replies. I do have "some" understanding of some of the issues concerning "comb filtering" and the subsequent high frequency attenuation that it leads to. However I was thinking about a concave line array with a variable curvature (not by much) which would help with the "comb filtering". I always listen to music in one place so I should always be in the sweet spot. Also the driver arrangment would be 4-1-4, as in fullrange x4, tweeter, fullrange x4. I do like to listen to live music recordings and it is this that has put the idea of a line array to me. It would require quite a bit of work so if you guys think that it would not be worth the effort then I will take that advice and go in a different direction. Cheers, Jerry

[GM]

FWIW, I've experimented with 'focused' line arrays using car audio 6.5" co-ax drivers and the 'sweet spot' is extremely narrow, like near 'head in vice' narrow, but dialed in they do perform well. I found that a single tweeter bowl shaped array to mimic a huge point source driver was a much better choice overall with a rectangular one being an acceptable compromise. Note that the latter worked best overall with 4" x 10" high aspect ratio car audio drivers.

That said, none of them could compete with the overall presentation of a cheap driver clone of McIntosh's XR290, but doing it with high SQ drivers and the high power required for ~life-like dynamics was/is/will continue to be so far beyond my budget that DIY horns will remain the best compromise for me.

GM

[mayhem13]

If i understand you correctly, you will be implementing a tweeter in the center of the array? How would you match SPL with a single tweeter except for a compression driver......HMMM sounds interesting.
As to your question on the subs, i'm in the planning stages for a friend who has two Maggies of building 2 4x15 IBs in stereo from 120hz down directly behind the panels. Should be impressive to say the least. I guess you really want to build 2 Mid-Bass modules to offset the arrays natural roll-off and increase power handling. A stereo pair of OB xls in H-frames would probobly give excellent results down to 40hz or so.

[Quackhead]

*Ahem*.....
The Murphy Corner-Line-Array Home Page

[revboden]

about that sub question. the standard questions apply. how loud, how low, how much space to fill, budget, any WAF to consider.. the more info the better.

[MartinQ]

Originally Posted by Quackhead

*Ahem*.....

Wow ... that was a three year *Ahem*.