Large midrange for OB??? Scott G ?

[MBK]

Sooo... I have since gotten around to fire up my new 15ND930 and even to put them in the cabinet. The whole setup is functional, tweaks will come later. I raised the x-o point to 320 Hz (to the 6.5" mid).

Comments on the 15ND930:

- very light

- amazing looks and feel. The build quality... my goodness. Most drivers don't look half as good from the front as this one does from the back. Extremely open basket, the magnet structure is practically a sieve with all that venting. The diaphragm is coated with a sticky compound which is water repellent, this one is not so cute looking (rather like tarmac). Double roll cloth surrounds. Chrome plated spring loaded terminals. I'll do some closeups in studio fashion when I have the time...

- very quiet at LF. In fact I heard air noise and was disappointed. Then I realized I was blocking the rear vent - I had just let it rest on the floor for a first listen and this is a no-no. In the proper cabinet mounting, there is hardly any noise and LF performance is very clean. This in spite of the fact that you can use the vent air motion as a fan at 10 Hz or so and near full excursion... Xmax linear is 6.5 mm and Xmax total is 17 mm, one-way.

- SQ: I tried a 100 Hz crossover and now a 320 Hz , both LR4, to the 6.5" mid. Even with the lower x-o, and more so with the higher one, the midrange has substantially improved in clarity. I attribute this to the lower harmonics contributed by the 15ND930 as compared to the previous woofers (older Vifa 10" car models), and also to the lighter burden of the mid now. I was surprised at this, because even intelligibility, and detail at much higher frequencies than the 15" is used for, has improved substantially (sunjectively at least). I wonder if there might be a residue of higher order distortion added as well contributing to this, but preliminary distortion plots show nothing of the sort.

- Measurements: no real good ones yet. Below is a simple distortion sweep, woofers in shallow U-fram OB, volume set to 100 dB at 200 Hz reference, *at the listening position in-room (ca. 3 m) (!!!)*. Measurement *at cone*, I did not measure the actual dB at the cone, I assume 110-115 dB. Below 50 Hz the figure is embellished by the low Q rolloff, which loses some 12-15 dB from 100 to 20 Hz. Still, a respectable dB output and considering this, quite impressive HD figures. I have to repeat this to check for possible mistakes, around 1% THD at 50-ish Hz at this output level is really remarkable.

[MBK]

And here the corresponding FR, measured at cone. This is a worst case measurement, I have a rather bulky frame as childproofing in front of it, it was close to the rear wall etc, so some of the 300Hz+ wiggles are likely due to these factors.

[MaVo]

Seeing your pleasure with the 18Sound drivers i want to share mine.

I recently cast away my eminence kappa 15lf and replaced them with 18Sound 12ND610 drivers. I run them in open baffles from 50hz to 500hz and i absolutely love the sound. its very clear and precise, much better than the eminence speakers. it fits the sound of the Fostex FE208EZ, which play the rest of the music signal. i tried various crossover points (using a software crossover) ranging from 100-500 hz and they all sound nice. nothing to complain with the new drivers :-)

Right now, i want to build some fronthorns for them and see what changes compared to the dipole setup.

[MBK]

Great to hear, and yes, "precise" is what came most to my mind in describing the sound.

18Sound has a great lineup, there is something for almost any application there, I could have bought various models and gotten ideas for all sorts of approaches. The ones PaulW bought are also very interesting...

My local dealer delivered to my house (for free) btw, and mentioned in passing that he also sells RCF drivers, while handing me the catalogue... yet another technology loaded high quality lineup.

Interesting that you use a bass driver below a Fostex 208. I think it's clearly the way to go as well, with these light and low xmax fullrangers, but so many try to force those into bass territory...

[MaVo]

I designed a setup where the Fostex plays fullrange without 18Sound woofer. I made it for listening to "lighter" music such as jazz and folk (because i listen to alot of electronic music else). comparing these two, the main differences are

- more headroom with woofer (i really dont like seeing my fostex's membranes vibrating)

- lower bass with the woofer, since i can equalize it a bit more.

(well, those two are obvious :P )

I expected to hear problems around the crossover point - the eminence had some - but the drivers are better than my ears, they match quite well. So the single driver setup is not much in use.

I really wonder how a 2" compression driver in a wooden tractrix horn would sound along with the 12ND610 (perhaps also in horns) - 18Sound have 2" drivers that look really tasty on paper.

[Paul W]

Glad to hear the 18Sound drivers are working for everyone. The 10NDA520s are running (and sound fine) but for now my actual focus is on tweeters and waveguides...midrange to follow.

MBK...what signal does Audio Tester use to excite drivers?

[MBK]

MaVo,

yes I also wonder about the 2" compression drivers. So far I am quite happy with the current setup, I can't justify it, through absence of a problem ;-)

Paul,

Audiotester has quite a range, but I mainly use MLS 12th order, to go easy on ears and tweeters and keep room effects low. Downside is low resolution this way, about 5 Hz, and averaging is a must or I get lost in the forest of peaks and dips. I don't window because I sometimes get artefacts that look real enough to waste time on them before finding out...

Other signals, sine, triangle, sine burst (but not windowed, so I can't use Linkwitz style bursts), Dirac, white and pink noise, dual tone. No MLS LF pre-emphasis though, so again this works against LF S/N ratio, and no custom burst. You can use any signal and look at it in RTA of course, but that doesn't work for bursts. What I like is the slope tool, draw a line on the graph and you see the slope, and the level tool, both implemented very intuitively. Curves can be selected/deselected, and graphs saved as bmp or data as text.

It also has distortion sweeps, RTA, waterfall, and T/S capability.
Overall for 35 Euros shareware license it is good, it does not have some goodies, and has some rough edges that could be optimized in a perfect world, but is uncomplicated for the basics. All other software I tried I found either expensive, or complicated in terms of clicks/measurement needed.

Audiotester

[MBK]

So I finally got around to do some pictures of the 15ND930. The Basket has to be seen to be believed - if they made the basket even more open than it already is, all that's left would be just an engineering abstraction... (translation: I don't think a basket can get any more open than this)

[MBK]

The backplate has so many vents (the spider too of course) that it is literally just a couple of sieves. When playing at rather high SPL's the exhausts really do produce hot air, I was surprised at that because I thought in domestic environments and SPL's this would never happen. Now I know where the power compression in poorly vented systems comes from.

[MBK]

Detail.

BTW Paul when you said the bass from your woofers has onoccasion caused you to look up from your redaing I thought this was a figure of speech. Now I know this actually happens...

I am still, and more and more, astounded by the effect these woofers have had on my system. It must be a combination of easing the task for the midrange because I cross them much higher than the old woofers, and the engineering, and the high efficiency, and the high BL, and the high Sd, and the lower doppler distortion, and possibly lower IMD. In any case, both mids and upper mids/highs have improved more by adding a sub-300 Hz woofer, than rather drastic changes I did before to the mid and tweeter.