Okay, here is the update on the progress.
There will be no more ALpha LS kits sold through GR Research, but some can be purchased from Creative Sound Solutions in Canada.
The Alpha was the first and there can be no more first.
We are replacing the Alpha with two new models, the LS-6 and LS-9.
Driver selection involves all custom built units just for this application.
The new woofers are going to be a real gem. They are a new 6.5" woofer custom built just for use in line source applications.
They use the same polymer type frame used in our M-130 woofers. This is a non resonance design that allows surface mounting. It looks great. The motor structure includes Neo magnets too.
Impedance is 4 ohms to allow two grouping of eight drivers yielding 8 ohms and to closely match the tweeter output level. Minimum dip should be in the 6.8 ohm range. This also allows three groups of four drivers to be used (12 total per speaker !) that with added DCR of the network should yield about 6 ohms of impedance and a minimum of around 5.2. The network could make these figures slightly higher still.
For you guys that can crunch the numbers here are all the specs:
"Method: Fixed-Mmd (20.59 grams)"
"DCR mode: Fixed (3.11 ohms)"
"Area (Sd): 137.07 sq cm"
"Series resistance: 100.00 ohms"
"Stimulus level: 1.74 volts"
0.458 "RMSE-free Ohms"
32.225 "Fs Hz"
3.110 "Re Ohms"
16.715 "Res Ohms"
2.251 "Qms "
0.419 "Qes "
0.353 "Qts "
0.225 "L1 mH"
0.387 "L2 mH"
3.704 "R2 Ohms"
0.000 "RMSE-load Ohms"
29.940 "Vas(Sd) liters"
21.498 "Mms(Sd) grams"
1134.627 "Cms(Sd) æM/Newton"
5.686 "Bl(Sd) Tesla-M"
89.721 "SPLref(Sd) dB[8 ohms]"
And yes these were designed to play low. In a standard optimal ported enclosure a single unit will play to a -3db of 42.5Hz.
In the EBS type alignment that these will be loaded in, the roll off is more gradual and more extended. The network used on these is similar to a standard baffle step compensation circuit but it starts much lower in range. It pulls 3db of output from them and makes what was the -6db down point the new -3db down point, which is 30Hz. Model this and see for yourself. Each woofer will need .7cubic feet and a tuning frequency of 30Hz.
Now running a line of them adds low end extension due to the collective gain of the array. On the larger unit there should be about 6 to 8 hertz more extension. This will put the -3db down point in the mid to low 20's with the speed and quickness of a small driver.
Also, I'm not sure how you select your drivers, but the new Extremis 6.8 from Adire has caught my eye.
Feel free to run the numbers on those too. I have. Our new woofer plays just as low, but does not have the extreme X-max of the XBL^ motor technology. But then again using this many of them, X-max is a non-issue as they may never see output levels that would push them to even half their X-max.
Plus, with our woofer there is the lush natural sound of the treated paper, curvilinear shaped cone. It also has a really smooth response throughout its range.
Right now the woofers show a little bit of break-up above 4.5kHz. This is no big deal if only used with the new custom planar magnetic tweeters crossed in the 1kHz to 1.2kHz range. But I might also want to use these woofers with some of the true ribbons like the G3si which would require crossing in the 2kHz to 2.5kHz range. So I have them working on the upper end break-up to see if it can be minimized. I am looking for a flat response with no break-up into the 6kHz range. So the specs could still shift around slightly if needed to remedy this.
The new tweeters are being custom built by BG. They are a new 8 ohm Neo 8 PDR. DCR should be about 6.8 ohms. This will allow a grouping of six units wired as two groups of three giving about a 10 ohm load (maybe less with network), or wired as three groups of two for an impedance in the 4.5 ohm range. It just depends on the needed output level to match the woofers. For the larger unit using nine of these units, they will be wired as three groups of three to get right back to a 6.8 ohm load that could be slightly less with the network.
These new PDR versions will also have a wider horizontal off axis response and a more extended top end that previous Neo 8's.
Target price for the kits are $1,500. a pair for the LS-6 (6 Neo's and 8 woofers per side) and $2,000. a pair for the LS-9 (9 Neo's and 12 woofers per side). We'll see what the numbers come to in the end.
Due to delayed time involved in driver design I am guessing these to be ready by the end of April, sooner if I'm lucky. So hold on.
As for these questions:
Having never heard a line source speaker, I'm assuming they rival horn-loaded speakers for efficiency and dynamics.
Yes, and then some. Plus, the line sources have the advantage of lower distortion, and loses of only 3db per doubling of distance instead of 6db per doubling of distance from a horn loaded speaker.
Will you have matching surround designs available?
Clearly both models could be used as rear surrounds. Hopefully in a large room. However, I do have a few ideas for some smaller surrounds and a center using the same drivers and the addition of a Neo 3 PDR. I might even use my M-130 woofers in those applications to get them down to a more reasonable size.
First things first, just hang tight. Cool new stuff is on the way for 2005!
Anymore questions?
