[jeffreybehr]

Built with SonicCraft 6-1/2" drivers and 4 spare tweeters for Kindel PLS-A.  2nd tweeter is on the rear wired dipole.  PLENTY listenable but not much bass in the bottom 2 octaves.  Of course there's lots of work to do.

[JohninCR]

OB arrays, duct taped baffles, I love it.  Don't worry too much about big wings, you'll need a sub for HT anyway.  Use Linkwitz's spreadsheet to set your SPL vs extension target.  You may need some more tweeter efficiency to keep up with the main drivers unless you're biamping (then good power handling is necessary).  Once you get it dialed in, you'll love it.  IMHO nothing beats OB line arrays for HT, and they're quite unique for music too.

[jeffreybehr]

The first prototypes were wired* with the 65s (my designation for the Sonic Craft 6-1/2" bass/MR driver) driven full-range.  The tweeters were driven thru a 3uF cap that created a HP filter calculated to be c. 6.6KHz.  Jeff Glowacki of Sonic Craft (known hereafter as JG) had cautioned me that altho the driver has fairly clean treble, treble sounds better from a tweeter so be sure to use a low-pass filter no higher than 2800Hz.  I wired them full-range to hear what they sounded like, which is rather good.**  Tonite I wired a Solo-brand copper-foil inductor of 0.40mH in series with the 65s for a LP point of c. 3.5KHz, and I lowered the tweeters' crossover to c. 3.3KHz.  The system sounds a little smoother...less edgy...and has plenty of treble energy for me.

When I can get my sinewave generator running, I'll report a sensitivity number, but in rebalancing the multichannel system, I had to turn the other 4 channels up EIGHTEEN deciBels!!!!!   845-based SET here we come!   


* I wired the 8 4-Ohm drivers in series/parallel for an 8-Ohm load.
** I have stated many times that I'm sometimes more a tin-eared audiofool than a golden-eared audiofile, and quality of treble is one of my failings, in that I have a serious depression in my hearing in both ears from, generally, c. 2KHz thru c. 8KHz.  The drivers' measured response fall abruptly after c. 8KHz.  I imagine I simply can't hear much of the drivers' stated harshness in the treble.

[JohninCR]

Hi Jeffrey,

I never could get my 2 watt SET to work well with my arrays, apparently some problem with
reactance of having a large number of drivers.  I didn't really understand it, but it kind of
dampened my interest in pursuing arrays.

[jeffreybehr]

John, I'm sorry to read that your SET wouldn't work well with your line arrays; I sure hope mine do.  They’ll be 25-watt ASL AQ1006, 845-based amps.

I didn't have the correct-value inductor to use as an LP filter, so I unwound a Solo 12g. copper-foil to get to 0.4mH for a filterpoint of c. 3.3KHz.  Without any tweeter connected, the treble is a little smoother...duh!  Then we didn't have enough treble energy so I wired the tweets in parallel* and changed the cap value.  There's a few dB more now, but I think I'll disconnect the rear tweeter to get back to a load, 4 Ohms, that's a little closer to the 8 ohms of the rest of the system.  (Bill Kindel didn’t have this problem because he used SIXTEEN of these in the PLS-A.)



Two golden-eared friends, one my regular buddy who is indeed VERY golden-eared, came over last nite and LOVED the sound of the system.  They both said that, generally, the system sounded perhaps-better than ANY they've ever heard.  The comments during the evening made me VERY happy.  Frankly, we're all amazed that a system with $160 of drivers in it could sound as fabulous as it does.

The system definitely needs a better tweeter, and I'm torn between point-source and line-source.  The latter would be much more expensive, but maybe it'd sound better.  I'm considering the Fountek NEOCD2.0...http://www.fountek.net/products_neo_20.htm .  Its 98dB sensitivity, 7-Ohm impedance, and very smooth frequency response seem just right; many other ribbon tweeters don't have enough sensitivity.  I’d prefer not to spend many-hundred dollars on the tweeter system, but all who have heard the system say that the VERY-high sonic quality of the main system deserves the best tweeter I can find.  Comments?

Still wrestling with its lower-frequency balance.  Of course larger baffles increased the output in the lower-MR and bass, but now we have a little too much lower-MR energy...and I still want more bass!  I’ve thought of two solutions to this contradiction.  One is to make the wings slightly smaller to reduce the reinforcement of the lower-MR (and to make the system easier to get around!).  Then I’d add 2 more drivers to the bottom of the stack, wired in series and biamped thru my existing Dahlquist DQLP-1/Outlaw 777 system.  (I considered filtering them passively, but that LP-1 implored me to put it back to work.)  The LP-1 has continuously variable LP points and a bottom-octave-boost control, so it’s well suited for this purpose.  I believe using the same drivers will blend the sound of the bass system better.  Also, Jeff Glowacki wants to see the line array’s bottom driver at least a foot off the floor, and adding 2 bass drivers on the bottom will do it.

JG calls it speaker madness.  Indeed.

Constuctive comments much appreciated; as is obvious, I'm a novice at this.


* for a 2-Ohm load

[JeffB]

Are you saying each driver is $160 or is each driver $10?

[jeffreybehr]

Each of the Sonic Craft 6-1/2" drivers is $10; minimum order is one carton of 24 drivers for $240 plus shipping.  They have some special Torx-head screws you might want, too.  800/689-4434.



Am considering this http://www.partsexpress.com/pe/showdetl.cfm?&DID=7&Partnumber=275-085 Dayton mag-planar tweeter for only $32; anyone have experience with it?

Have changed some values--the 0.4mH choke wasn't doing much; replaced it with a 1.2mH and now it's rolling off some treble from the B/MR drivers with an FP of around 2.5K.  Removed the rear-facing tweeter and changed the HP FP to about 2.5K; sounds pretty good.

Will be cutting new front plates for TEN drivers this week.  The 2 lower drivers will be biamped* as bass-only drivers to try to get enough mid- and upperbass.  I'll be making the wings full-height this time--the short ones were what I had lying about--but shallower.

* I already have the filter and amp, so this is a 'gimmee'.

[JohninCR]

If you have extra sensitivity and a couple of big chokes around you might try
a choke on the top and bottom pair together.  Bass frequencies need longer
lines than higher frequencies, so it may help balance the nearfield/farfield
transition distance and also give you more balanced response like baffle step
compensation.

For a tweeter solution, I think you'll have to go with a horn tweeter to get
the efficiency and dispersion required.  Keep in mind that in the range that
the array operates as an array, its spl decreases by 3db per doubling of
distance vs a single tweeter point source decreasing by 6db per doubling
of distance.  That's a 6db difference at 4m (13ft or so).  This means that
when you use a single tweeter, you need it to be much more efficient than
the array to achieve balance.  Then use an Lpad to adjust to you listening
position.  A Fostex F17H at 98.5db might be enough if you pad the array
down with your wiring scheme and/or using some of the drivers for bass
as discussed above. Otherwise an economical solution I've use are $25 or so
per pair Pyle pro horn tweets for car audio (104db & 4ohms).  They have
efficiency and power handling to spare and you can easily tweak surprisingly
good sound out of them if you're on a budget.

BTW, how about a link for those sonic craft drivers at $10/ea?  It seems like
a bargain for cast baskets with plenty of breathing room for OB use.

[jeffreybehr]

John, thx.  I can now see my attempt to build an open-baffle system with line-source B/MR and point-source treble may not work well.  Maybe that's why Glowacki (JG) keeps recommending LS tweeters.

The Dayton is affordable enough to use 4 per channel for a 25" line-source.  I think I'd get around 100dB sensitivity from 4 wired series/parallel, for only $120 per channel.

Or if I wanted to go cheaply, I could try these...


Only 85 cents in hundreds.  http://www.apexjr.com/speakerstuff.html

That driver is not on SC's site; call JG at 940/689-9800 for details; the fone number to order is above.  It's a 4-Ohm driver that he designed for OB use and had custom-built 10 - 15 years ago when SC was building speakers.

[Bob in St. Louis]

My god man! That array is insane. 

Bob

[jeffreybehr]

My god man! That array is insane. 

Bob

Well, certainly, but whoever said audiofools were sane?

I'll bet it emits one hell of a wavefront!