Apogee Duetta Signature Rebuild

[JMAUSGP]

Thanks Justin, I ordered it or did I "Make it so"?

Judging by your posting times, you have given up on ever going to sleep again.

 

[Bernard]

Thanks Justin, I ordered it or did I "Make it so"?

Judging by your posting times, you have given up on ever going to sleep again.

Jim, er sorry, Joe, all posting times are Eastern, not local. I expect that Justin is not depriving hisself of his beauty sleep.

 

[Jimna]

Joe why are you answering for me in this conversation? or wait...who are you talking to again, Justin? Im confused.

 

[User211]

Jim, er sorry, Joe, all posting times are Eastern, not local. I expect that Justin is not depriving hisself of his beauty sleep.

Actually, Joe was dead right - a case of Insomnia (Faithless - now there's a good track). Pretty frequently, recently, I seem to wake up around 2:00 am and can't get back to sleep. So 30 mins - 1 hr or so on the PC usually sorts it. And I wake up knackered. Great

FWIW, my wife hates Pitch Black with an absolute vengeance. You either like that sort of stuff, or you don't. Seem to be some downloads here: Pitch Black Freebies

 

[User211]

Just had a chap round to listen to the Duettas, after hearing his MBL 116Fs a couple of weeks ago.

I forgot to take a picture, but he brought one of these round: Graaf 5050

The poor thing. It totally and utterly failed to drive the Apogees. Couldn't achieve realistic volume levels in anyway, shape or form. The sound went flat and lifeless. So while Duettas are reasonably sensitive for an Apogee, they still need way more than 50 Watts. This amp was fine driving the MBLs: MBL 116F. The difference in apparent driving power of my 211 monos over this amp was absurd, and overall experience with a multitude of amps on the Duettas now really does lead me to believe that they do indeed output as much as 170 Watts as the spec claims.

Did I like the MBLs? Yup I did. Are they better than Duetta Sigs? Nope, not in my book they aren't. Because Graz refurbed Duettas are just totally stunning

Speaking of which, I've just been offered an upgrade to the mid-range and treble ribbon. It's just become available as KLM5, and the only difference is the glue that bonds the aluminium to the Kapton backing. Apparently, it makes quite a difference in terms of overall resolution and dynamics - which I find hard to believe, but I've trusted these guys so far and it has 100% paid off. There's also a resistor upgrade to the crossover, using some non-audiophile grade resistors Graz stumbled on by accident. I'll probably get it done - will post a few pics of the ribbon swap out as they are worked on.

The MBL owner used to own some non-restored Apogee Calipers. When I asked him if he thought the Duettas were better, he just said they were massively better - in a totally different league. I think he liked them too.

 

[Bernard]

Justin,

What are the 211's rated at?

I looked at the Graaf link, to read this:

"But we don’t consider the 5050 to be "vintage", because our interpretation of the circuit utilises components and valves, such as the 6922, not used before in the audio field."

Excuse me, but isn't the 6922 ubiquitous in the audio field?

Thanks for your re port.

 

[User211]

Bernard - 211 mono spec. Might not look to powerful, but believe - they are! Probably related to the peak output capability where the 211s are driven into class A2.

Yup Graaf are delusional WRT the 6922. But I don't expect they Carey too much

 

[tonepub]

All the spec sheets I've seen on the 211 tube say it only has a maximum plate dissipation of 70 watts in class AB, and a few designers I've talked to say 50 watts max in single ended class a. So, your figures are probably a little optimistic. But if it works, it works.

 

[User211]

All the spec sheets I've seen on the 211 tube say it only has a maximum plate dissipation of 70 watts in class AB, and a few designers I've talked to say 50 watts max in single ended class a. So, your figures are probably a little optimistic. But if it works, it works.

We've been through that one before Jeff. In class A2 a 211 WILL output 100 Watts. There's 2 per mono, and the amps will reach 170 Watts, albeit on transients only.

Using a DB calculator, even at 80 Watts/86DB/4 Ohms, the Duetta will hit 100DB. Lots more power required to get the last 5 DB a Duetta can give, however. Don't forget there's no extreme impedance fluctuations to deal with unlike an ML panel.

Anyway, I've had the above ribbon/resistor upgrade done. Will report when it's had a lot more running in time.

 

[User211]

OK - two months and a little trouble later since the upgrade.

In short, the first thought, before the restorer left, was "great - bags more resolution". But we had only been listening to instrumental type stuff - no voices.

When I did so, I was literally quite shocked - too much sibilance and smear. Not just a little - really quite a lot! Not at all subtle. There was also some pretty odd colourations occuring in the upper mid. Not nice colourations - just plain odd and bizarre.

The speakers also sounded too bright. But this became extremely apparent with some material - which was presented with what seemed like incredible resolution - beyond ESL levels. I've not heard anything like it.

Dispersion was much improved with the sweet spot being much wider than before. Also, the actual behaviour of the ribbon visibly altered - the whole ribbon seemed to move and not curl much as per the earlier KLM2. Additionally the sound now had much more front to back extension and layering.

So there were some real advantages but some real disadvantages too. I started posting about the various aspects of the change on the Apogee forum. I even had Graz phone me direct from Australia - he was getting concerned with my obvious dissatisfaction about the less positive aspects of the sound. The Apogee forum thread I raised got deleted along with many others by accident, so it is not worth looking for it.

In short, I found myself really NOT enjoying the speakers as much as I had done before. The upper-mid colouration and the sibilance/brightness were really getting on my nerves. But the positive aspects were there too.

So I surmised - extra running in required. So I put the Duettas on 12-14 hours a day using a solid stater. The ribbons now have around 250-300 hours on them at a guess.

I had a friend round last weekend who owns MBLs as detailed above - and after this activity he was really positive about them for the reasons identified above - and the fact that for some bizarre reason, the odd upper mid colourations had all but disappeared. He stated I couldn't possibly go back to the older ribbons - which was what I was thinking too. However, we both knew they were still too bright.

The next day the restorer came and we changed one of the x-over inductors from 0.02mH to 0.06mH. Results? Absolute disaster. Sounded terrible. We then changed the inductor for another thicker gauge 0.06mH inductor. Result? Well - really extremely good. Sibilance back in check and sounding natural, and the brightness issue resolved too.

That two inductors can sound so different has been a real education to me. Though they are measurably different in terms of resistance. The one that is in there now is actually an original Apogee inductor.

The bottom line is I now have an excellent sounding pair of Duettas again. Better than before - without the loss of the positive aspects detailed above.

In short the performance bar of the Duetta Signature has been substantially raised by Graz's KLM5 ribbons and the new resistor packs, and I for one respect Graz enormously.

So we have something old, something new, something borrowed and something blue Well, that thought keeps me smiling at any rate.

I suppose what everyone wants to know is do they sound better than Martin Logan's better efforts? Well, let's just say they do sound pretty damned excellent and leave it at that!

 

[hirschmj]

How did those binding posts fit?

Well, I spent the better part of today re-arranging my listening room. So here are some in-situ pics. I hope you're not all sick to death of this thread, but I know we have some porn lovers around here, and some of these pics show ribbon close ups the like of which I have never seen on the web. So basically, some of them are worthwhile.

Rear view, MRTW three position switch removed entirely, CMC binding posts (not the Eichmann's mentioned earlier), and black stocking. Ice cubes trying to remove the pits left by the Ascent spikes!

How do the binding posts fit? I've got some Centaur Majors that I'm replacing the binding posts on and the first set I bought was too thick for the spades connectors inside, but too thin to fill the hole in the back plate. I'm thinking about ordering some CMC binding posts and I wonder if any special work was required to get them to fit properly?

Looks amazing by the way.

 

[User211]

Here's a pic of the other side of the mounting plate - pretty simple really. No special work required.

Hope that helps

 

[User211]

Hm... nearly a year since I said something on this thread. However, thing have been happening. A new spec for a better Apogee Duetta Signature has been drawn up, which is quite different to the original specification. Hopefully, it'll result it better performance yet.

First things first, though. What colour will these new Duettas be? A tough one, but using the magic of Photoshop on an old (and untidy) shot of my listening room, I have decided on this Accuphase type colour. I think it is quite smart, and blends well with the room.

I think they could do with a rename, to something related but different. I'm thinking either Apogee Duetta Interstella or Duetta Apastron, maybe. That's only for my personal pair, I should hasten to add, since the spec is unique. Any suggestions are welcome, and the name will be engraved on the back of the speaker.

I'll post some more, but here is a snap of the Photoshop messin' in the meantime (Descent long gone... to the chap who bought my Ascents).

 

[Bernard]

Justin, i think that the sound from a speaker that colour would be too bright

Im not crazy about that colour; you've done Mercedes Blue, now how about Ferrari Red. That colour looks more like Lada

As for the name: since the spec is specially for you, it should reflect something about you. Bristol is a port city, so how about "Duetta Porteño". It's a nice Spanish name (meaning from a port), and "Duetta" could well be Spanish too. Now where did I put the Stilton?

 

[User211]

Hm... Ferrari Red - nooooo. That'd be too close to a certain CLX forum members car. I wouldn't want to inflate his ego, not that he posts around here much these days anyway!

However, I have gone off the above colour. I'm thinking more Porsche now... will probably go with this:

 

[User211]

So why bother with another pair? Well, the intended spec should help give some insight into that.

1) Brand new front panels. These will be thicker and have a 45 degree odd aperature onto the bass and MRT sections as per the Accuphase coloured Duetta above. This was taken from a pic of recently restored Duettas done by Graz which also happened to need new front covers. I'm not sure of the internal spec for these, but they will be different to mine.

2) At present the covers can only be removed by removing the stands to access the two screws that allow release. The new covers won't require this - the fixing bolts (way more of them) will be elsewhere.

3) Covers will be attached via a damping mech that ensures no rattle.

4) Speaker frame will be braced by aluminium spars. These will stop any twist in the frame, and combined with the new stands will ensure the frame hardly moves at volume. This frame is substantial – we’re talking thick pieces of aluminium here, both vertically and horizontally. The magnet arrays will be attached to it.

5) Speaker stand bases will be elongated for better stability. Rear stand support will rise way up behind the speaker rather than the short support of the existing design. These stands will screw directly into the aluminium frame. This speaker is going to be incredibly rigid. It shouldn’t move even at high sound pressure levels and vibration from the front covers acting as passive radiators should be kept in check.

6) Speaker rears will be acrylic covered rather than the "sock" over the back on the frame.

7) X-overs will be external and contain uprated caps - ESA Clarity. It will interface to the back of the speakers via a single umbilical chord with a locking mech.

8) Selectable FR response – possibly by remote control but maybe not. This will be kind of akin to the original’s three way MRT ribbon switch.

9) Graz's latest MRT ribbon clamps. I also believe he has modified the bass panel foil cuts in some manner giving mildly improved performance.

10) Ribbons cut using Graz's new machine.

11) Other secret bit 'n' bobs.

We did consider using neodymium magnets to get the efficiency up. But working with so many very high power magnets is very difficult, and accidents can occur which require a couple of tonnes of force to correct. Whilst this would increase efficiency to the 93DB odd mark, horror stories from Graz’s efforts show that it is a difficult task to achieve. That and the cost (£4K for the magnets alone) and a worried UK restorer mean that we aren’t going to do it. I don’t believe the world will see many pairs of such planar magnetic speakers. To my knowledge very few have been made.

 

[User211]

Here's the plan for the stands. I have the plan for the internal aluminium bracing mech to but I'm not at liberty to post it. Whilst you may think that stand pciure shows it, I can assure you it doesn't - it is infact being done in a different manner.

The stands will be in brushed aluminium and are being made by a company that supplies parts for forumla one motor racing. They will extend further forward and back for better stability than the originals. The mass of each speaker should be about 10 Kg up on an already very heavy design. Not looking forward to getting them down the stairs TBH!

Also, here is the Duetta used in the pic above sitting in Graz's hall.

Oh BTW Bernard - good name suggestion! However, I'm not going to go with it.

 

[Ps68]

Justin, this looks great, right up my street! It looks like you have covered every possible detail. I can lend some ears for testing when done!

 

[Bernard]

Justin, is what you have described going to be the "standard" Graz speaker?

What do you plan to do with the old pair?

BTW, I'm glad you're still posting here!

 

[User211]

Paul - just been browsing your website & system pages. Looks like I missed your last system page post. If you're coming to the Bristol Hi-Fi Show you are welcome to come round here for a listen. Kill two birds with one stone, so to speak. OK it won't be with the new pair - but that doesn't matter too much - the pair I have are well worth hearing and should you like them they are probably available.

The last Logan owner to hear them simply stated "I do not like my speakers anymore". You have been warned!