Ellips-P

This is a passive crossover version of Ellips-A.

Listening tests initiated and burning in is in process. 32W and majority of Scan Speak woofers really need it, fortunately  the effect is noticeable quite soon, after 2-3days of burn in.

Basic concept was the same, there was not much I would like to improve or change.

- 12" woofer in closed cabinet. 32W T00 models very well in 70l closed cabinet, promising the low end extension F-10 at 20Hz. Measurements confirmed this number, and additionally, passive crossover interacts with woofer impedance in favorable way and create mild bump at 50Hz, around 1dB. 

- midrange driver 18WE Ellipticor. I have to say it was pleasure to see and hold this driver. Datasheet and 3rd party measurements promised perfect performance and my measurements confirmed that. Cone edge / surround treatment, rear side of the cone treated with the damping layer, cone pulp similar to 18WU Illuminator series, without cone slits,....that all likely contributed to excellent measured performance and the sound.

- T34B is modern state of the art tweeter and with waveguide it makes incredible result, both measurements and the sound. Paying attention to minimize diffractions is always good think and waveguide is very helpful in that. T34B shallow dome profile makes it suitable for waveguide loading, as well as barrow surround.

- And to remove any diffractions from the list of potential issues for good I designed the front baffle with quarter-ellipsis roundovers. One dimension was 50mm, same as the thickness of the baffle, the other dimension was 80mm as the ellipsis starts close to waveguide and 18WE. This is very effective and also good looking solution. In combination with WG it minimizes any diffractions to zero.

I wanted this loudspeaker to sound at least the same good as active version, and hopefully even better. Drivers, cabinets, basic concept were the same, so what else could make the difference, the impact? Yes yes, the crossover....

- crossover frequencies make the difference in the sound, it changes/defines the radiation pattern of the loudspeaker, it can make all components and design choices complement each other in a positive way and make them work in synergy, resulting in both exceptional sound and also technical performance.  So I decided to keep 250Hz and 1800Hz crossovers.

- crossover topology and slope orders. As in previous case regarding crossover frequencies, the crossover slopes were also clear and given, as 4th order LR worked so well in active version.

- crossover components quality. Hmm hmm this is quite often discussed matter. There were projects where the caps in tweeter crossover did not make much difference, so I decided to keep Jantzen Cross Caps or Standard Z-Caps. Though there were the projects where I clearly heard the difference in the favor of Superior caps, for example. One could fall into the trap of neverending capacitor testing, listening, analyzing the differences, and to be frank, also selfbias and vicious circle of adding different flavors to the tweeter or midrange character. In that matter I want to stay reasonable, and the foremost ensure technical qualities first. Crossover values fine tuning, longterm listening tests, good spinorama.... that is what makes real difference, and is fundamental and determining factors for the result . With the drivers of the level we have here and spinorama set looking so well the crossover components quality really counts. I am not a big fan of too fancy, too expensive, snake oil components, but I experienced the sonic differences between low cost caps and yet reasonably priced more expensive caps so I did not think twice about caps I wanted to use for this project. Jantzen Superiors are well balanced yet they do not cost the fortune and are clear step up in sound quality.

- resistors and their quality are another components that is in the way of the signal from the amplifier to speakers. Again based on experiences with previous projects I found out I prefer tweeter and midrange without series resistors in the path. Good resistors are expensive so it is good to avoid them in the design anyway. It has one downside....it is not that easy to design crossover without series damping resistors. Here I had 18WE 4ohm midrange with plenty of sensitivity, and I had to match it to 32W woofer sensitivity. So designing this crossover was not easy and I had to try different topologies.

Measurements

Measurements were done for 0 to -180deg in 5deg steps. Graphs show only 0-90deg for better readability. Measurements were taken in very large room => I used no gating, just 1/12 smoothing. I do the graphs with gating as well, but I prefer looking and working with measurement without gating (during crossover modelling I also look at gated measurements), just 1/12 smoothing, and placement of the speaker during measurement on ~2m stand, which normally provides good data with ~10ms gating. Mic distance was 1m, and measurement voltage 2.83V. SPL calibrated. 

32W woofer measurements

18WE midwoofer measurements

T34B tweeter measurements

Few thoughts on the measurements above:

- DI of the tweeter and the midrange between 1-2kHz is the same, this is ideal situation and demonstrates the advantages of the waveguide

- The peak in woofer response at ~800Hz needed to be suppressed with RLC on woofer crossover. The peak was little bit surprising, Scan Speak datasheet does not suggest any significant FR variations below 1kHz

- distortion measurements of all drivers are incredible. Thanks to Earthwors M30 it was possible to measure the performance of such a drivers. With standard mics, the results are highly effected by high noise floor/distortion of the mics themselves.

- woofer distortion measurement below 200Hz looks perfect, -60dB H3 at 50Hz, I like it

- mild dip at 500Hz in 18WE response look suspicious, though FR measurement from 30cm does not show the problem. This might be some reflection coming from FF 1m measurement.

Crossover modelling

Crossover points and crossover slopes follow active version as both were already proven by listening tests. Woofer-Midrange crossovers frequencies between 200-300Hz were tried, and 250Hz proved to be the right spot. 200Hz started to sound dissattached, like not well integrated 2way+sub. 300Hz Fc made an impression that the voices come from the floor. 250Hz sounds balanced, there are no negative effects in the sound. Phase tracking is perfect and basically all spinorama graphs look ideal, considering this is loudspeaker with non-coincident drivers. 

One of my main goals was related to the resistors in the crossover. I managed to come with version of the crossover that has no series resistors in Tweeter and Midrange sections.

Horizontal and Vertical polar maps are below.

Photos

Removing the grid from those Bliesmas and mounting them to WG take patience, steady hands and working slow, any distraction or work in hurry might not pay off.