This one is the JMLab Deline 3.1.
It's a transmission line design with a rear terminating slot shaped opening.
The stock crossover reveals the usual budget parts that include iron core inductors and common electrical wire.
The frequency response stays within a reasonable range, but the little woofer has a lot of choppiness within its range. And the actual crossover point is quite high at 3kHz. I used to stock and distribute the Tc90Tdx tweeters used in these, and they are a pretty robust little tweeter that are capable of playing much lower. I even used that tweeter in the old Paradox-1 models that we released as our first production speakers.
The horizontal off axis looks pretty good. And moving off axis a little softens that big peak at 19kHz that is typical of these tweeters. For some people the peak can be a source of irritation. Many though simply can't hear it. It is up there pretty high and there is not a lot of music information up there.
The vertical off axis shows a little drop in the crossover region, but not too bad.
The spectral decay shows a few areas of stored energy. Some of it though looks a little better than it should as the peak in the top end of the tweeters range is pushing the whole graph down.
So let's move it up 5db.
The impedance is a bit high on the tweeter end of the curve and it also shows a cavity resonance issue at about 120Hz.
I later could see that the resonance was a result of very little damping internally. It had almost no damping behind the drivers.
One strip of some type of recycled fiber was it.
So let's see what we can do...
I couldn't make the overall response any smoother as the choppiness in the woofers response was just not something I could get away from. I was able to lower the crossover point down to 2kHz though. This passes off duty to the tweeter much sooner and allows for a lot more resolution and detail in the 2 to 3kHz range.
And the new horizontal off axis response looks very good.
And the vertical off axis is improved slightly with a little less of a drop in the crossover region. This also indicates that the speaker might benefit from a little tilting back.
The new spectral decay looks very similar to what it did before.
And here it is moved up 5db for a better look.
Here is where things really look better. This is the new impedance curve.
The resonance that was there before is now gone. This is thanks to lining the upper cabinet with some No Rez and adding a light amount of fiberglass insulation.
The addition of the No Rez will really clean up the bass response and lower vocals. Plus no more buzzing at 120Hz.
The new crossover steps up performance in a big way. But I had to mount them on two boards to get it all to fit into the old space.
Here are a few shots of it all mounted.
The quality of the wiring was also a big performance jump over what was in there.
Then I topped it off with replacing one of the sets of binding posts with tube connectors. This adds a level of clarity across the board, bass to treble. One set of the old binding posts was wiring in parallel to the tube connectors so that they can be compared (always fun) and so that any speaker cables, with any ends, could be used to play them.
Overall this was a fun project with excellent results. And the cost came in just under $600 on this pair for everything.
If any of you guys have speakers that could use an upgrade then send them to me and I'll work them into my schedule.
