1) New bass ribbons. These have a different corrugation pattern than the last set and may be a bit thicker.
2) Clamps no longer MDF as per original but another material that costs quite a lot. Many times more than MDF. Was never too keen on MDF as a material for the clamps.
3) Clamps held to the chassis in a much more secure manner than previously.
I personally think this set up should be quite a bit better due to it being a much more solid setup. It wouldn't surprise me if volume capability is enhanced. In fact I am sure it will be, just not by a huge amount.
Anyway, you can't really see much apart from some black bits and some foil, so it's not giving away anything that can be regarded as confidential.
You can't underestimate the importance of making planars in as solid a manner as possible. This is another step in the right direction. Easy does it
They are just sitting there waiting for stuff to dry out before the top and bottom clamps are added. The MRT unit also needs to be put back on and a few other bits and bobs.
Looking forward to the results post break in.
This clamp material is also in Kim's Scintillas, for those that know of him. There may be a thread on them soon just not sure where.
The clamp material is made by the company my long deceased father used to work for, which I think is a really nice touch Jon and I where discussing what to use about a year back. It was actually a materials expert that recommended it.
The clamp upgrade has paid off. I had my family round this weekend, and we watched "The Dirt" on the 4K UST projector via Netflix - loud.
How I know that's not purist audiophile, but as my brother said "that really does sound very good". And he was right.
So essentially the speakers now sound better than they ever did by a good margin. I usually yawn a bit when I hear about upgrade XYZ improving people's systems as you never really know what the hell they are on about. You have to hear their system to know if it isn't bullshit. But whatever FWIW (not much LOL) according to me this is ace.
So what facilitates the improved bass definition? Probably the mass of the clamps and the fact that the material itself is "deader" than wood. And you can hear that easily. There's also far less sign of reaching the limitations of the bass panel when the volume is cranked up.
That said, there was an issue with the bonding of the aluminium to the Kapton. This was only really evident when playing certain material as it would excite this lack of bonding only when the amplitude at a certain frequency range became sufficient. Since we knew we had to replace the bass panels, I thought we had an opportunity to upgrade the bass panel clamps, and that is what initiated the investigation into using the material we did.
So there are two potential issues with Apogee buzz. Rotting foam on the clamp surrounds (not an issue here), and also separation of the foil from the Kapton. Or mylar in other designs.
I would strongly recommend anyone getting a refurbishment to use this material.
That said planars are a pain. Martin Logans (I went through multiple panel changes with mine) Apogees and others. They all need maintenance to keep them at top performance and always bear this in mind. If you have ears you will know when they start to drop in performance and just simple signal generator sweeps done slowly will easily isolate resonance faults with simple FR tests telling you how panel performance alters over time. Which happens in all panel designs using membranes I would bet.
Just sweep slowly and pay attention around the 300Hz mark especially. If it ever sounds impure at any frequency there is probably an issue though in certain areas nothing can be done. The ones you can do nowt about are very narrow band, though, and not worth worrying about.
Here is that plot from the ML website. I think I did it at 1/3 octave. So red was Interstella when delivered new, and green was the straight refurb you heard. Both in the same room in the same position.
So my bad crazily the LF response is actually up at 21 Hz so the +/- 0DB point will have been below 20Hz looking at that. Impressive.
That Scintilla thread doesn't appear to be forthcoming, so here's a pic. I think its good enough to do them justice. On Townshend stands. Note the fatter bottom lip that makes them look a lot better I think.
BTW after playing with PEQ for a long time I reworked the Interstella crossovers myself to kill the 3.2-4KHz peak using cheap components at first then using good stuff like Path Audio resistors, massive Jantzen inductors for the MRT etc etc. I modelled the lot using XSim first, then changed values using cheap components first for the best subjective result. Note the peak is common to both Duettas.
I found by notching it you get a subjective result that sounds a lot calmer and more enjoyable. It was noted in a review many years back as being an issue and I agree it is. So 2.2KHz to about 5KHz is now pretty flat. It changes the impedance a bit but in practise that is absolutely zero issue I found.