Apogee Duetta Signature Crossover

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*I also posted this on the Apogee Accoustics Forum:

I am looking to change the crossover in my Duetta II's to a Signature crossover.
In researching the parts needed I came across two sites with the crossover schematics.
Unfortunately, the tweeter-mid schematics are different between these 2 sites.
First difference is the inductor at output. One lists it at 6.4mH the other at 4.3mH.
Second difference is in the jumpers for schematics. The jumper for the low position results in the same equivalent circuit but the normal and high positions are different. The components are the same.
Schematic one is located here:
http://www.apogeespeakers.com/projectstech/Duetta_Signature_crossover.pdf
Schematic two is located here:
http://www.integracoustics.com/MUG/MUG/tweaks/apogee/duetta_xo.jpg
So the big question is which one is correct?
 
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Bill,

I'm not sure I would trust either one. :) None of the various schematics for the different models were supplied by Apogee themselves. They were all drawn by users who looked at their own speakers and made an attempt. Users were confused my markings on coils, had no measurement equipment, etc, etc. So, various inaccuracies crept into the results. Sometimes they got it right, sometimes they got it wrong.

I suspect schematic two is probably closer to being correct, but without an actual speaker to look at I can't be sure.

If you need an accurate schematic for a set of Duetta 2's I could supply it......because that's what I have. :)

Cheers,

Dave.
 
Thanks Dave,

On the Apogee forum, Jon, (who if the forum admin and repairer), stated the first schematic was correct. He also stated that both schematics where drawn by him at different times and he might have made a mistake on the second at the time he did it. Jon also gave me a schematic for the Duetta II but it doesn't match what I have in my speakers.
Apogee Acoustics • View topic - Duetta Signature Crossover Schematics
So, what does it all mean? I guess Apogee changed things up a lot without notice.
My intent is to put in a better crossover by making one up using the signature schematic with quality parts, but right now I'm not sure what is correct. I believe the first schematic is what to use based on Jon's comments so unless I get better info that's what I'm going with.

All of this crossover changing was based on the information I have that the Duetta II is basically the same as the Signature but has a different crossover, no front 'lip', and better mounting feet. So, to get close or exact Signature sound I just need to change the crossover.

BTW If anyone's interested, I tightened up the tweeter/mid ribbon without too much trouble and the speakers sound much better. Everyone on the Apogee forum said not to do that, (or you couldn't do that), but what the hell, it works. Maybe not as good as original or replaced ribbons but I'm pretty happy with the result.


Bill
 
Thanks for the info...........got rit of my duetta sig...but its crossover was same as .Signature ..
Now have the 5th pr of Stages.... 2 pr on the Cantaur Minors............ i have owen sen the 90s............great speakers.......
Dont get rit of the stock caps or coils in your setup...i have tried lots of so called high end caps.....an all i got is a diff sound never better....just one mans o-pine.......
I always came back to the stock caps......Coils?
Jason like the sound of Loss coils........i like the sound.......... some dont....not saying dont make changes ...keep the old parts!

I have done some of the North Creek..crossover mods to my Stages....Zoble on the Bass panels......he feel with his crossover....the Stages sound better than the Duetta sig......he did his work with the Stages an Duetta side by side.........an he also work at Apogee in the 90s..
Have fun
 
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Bill,

No, the schematic Jon supplied for the Duetta II might not match your speakers. That's actually the schematic I supplied to the forum many years ago. :)
It's correct for my speakers which are SN 3862. It's a simplified version....which may have confused you? (The 60uf capacitor is actually 6 X 10uf capacitors, etc, etc.)

The Duetta Signature schematic is (conceptually) the same thing as the Duetta II except there's a shunting capacitor across the series LR circuit in the tweeter section. This shelves the tweeter response back up at the high end vice leaving it flat.

Cheers,

Dave.
 
Hi,

Found this old thread. Acquired Duetta Sig's in mint condition. Actually, the previous owners never used proper amplification, so the Sig's stays out of usage, I believe.

I have the active digital xo and want to replicate original passive characteristics. Anyone know stock electrical xo point and any other eq correction, if any?

I assume the slope is 12dB/oct.

Any suggestion for better xo setting is welcome. I have 6-24dB slope options, LR, Butt., or Bessel.

Thanks in advance
 
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Well, if you select a Linkwitz-Riley electrical crossover around 450Hz (2nd-order slopes) you'll be very close to the stock setup.

You also need a broad notch filter on the MRT circuit centered at about 7khz with a depth of about -6db. Or, you could leave the passive existing notch filter intact and just disable the rest of the crossover.

Very important: When you disable the high-pass filter section of the MRT, you now have a path for DC to the ribbons. Any steady-state DC offset and/or turn on/off thumps from your power amplifier will be felt directly by the ribbons.

Dave.
 
Davey, thanks for reply.

Curently, I am using 24LR at 350Hz and just want to compare with factory setting, close as possible.

Notch should be probably between 1 to 2 octaves, I will try several options, but 7KHz and -6dB are important data.

BTW, already have 200uF cap on MRT.

Best regards,
 
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Davey, thanks for reply.

Curently, I am using 24LR at 350Hz and just want to compare with factory setting, close as possible.

Notch should be probably between 1 to 2 octaves, I will try several options, but 7KHz and -6dB are important data.

BTW, already have 200uF cap on MRT.

Best regards,

Yeah, that's a large capacitor and will do very little to protect the MRT driver from turn on/off thumps from your amplifier. Best bet is to use an amplifier that doesn't generate any. :)

Be careful.

Dave.
 
hmmm 24LR at 350...

The MRT in these designs will be rolling off energy starting as high as about 1.2 Khz AND the woofer crossover slope is critical to filling in below that. A steep crossover down as low as 350 hz may not give best overal sound. In fact the original crossovers I believe were set up to give a shallow slope gradually increasing to about 12db/oct.

My own experaments with these designs have shown this crossover slope and point to be critical in going from good to great. steep filters can initially sound good in a way BUT in time they sound less convincing than a properly aligned shallower crossover.
 
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The wisdom of the approach is debatable, but I'm just relating what the actual stock design implemented by Apogee was.

The "6db increasing to 12db" was just marketing speak from Apogee at the time. The stock crossover filters are simple second-order slope but with a fairly low Q. < 0.5.

There are more aspects at work here than the ultimate sound and smooth crossover integration. Ribbon longevity was just one.

Dave.
 
The wisdom of the approach is debatable, but I'm just relating what the actual stock design implemented by Apogee was.

The "6db increasing to 12db" was just marketing speak from Apogee at the time. The stock crossover filters are simple second-order slope but with a fairly low Q. < 0.5.

There are more aspects at work here than the ultimate sound and smooth crossover integration. Ribbon longevity was just one.

Dave.

Yes understood. Especially ribbon lifespan.

It may be market fluff BUT my experience has shown that there can be quite a fine line in these designs between good and truly great with some playing around with this slope. And higher Q filters dint give me a good result.
As well getting MRT level with respect to woofer panel right can result in surprising improvements. I found this to be one of the easiest tweaks with big returns AND as little as 1/2 db can be audible. This means that different rooms, placement, etc can upset this balance. Also the traps profile and attenuation level will upset this as well.
 
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I'm not sure what your point is.
The Apogee designers understood the trade-offs regards the filter slopes, MRT relative level, ribbon longevity, etc, etc, 35 years ago. The choices they made turned out pretty good. :)
Since the speakers are no longer made and the guys who designed them are no longer with us, it seems pointless to second-guess the design choices.

Regards experimentation along these lines......some Apogee owners have been doing this for years.

Dave.
 
I'm not sure what your point is.
The Apogee designers understood the trade-offs regards the filter slopes, MRT relative level, ribbon longevity, etc, etc, 35 years ago. The choices they made turned out pretty good. :)
Since the speakers are no longer made and the guys who designed them are no longer with us, it seems pointless to second-guess the design choices.

Regards experimentation along these lines......some Apogee owners have been doing this for years.

Dave.

Im a bit confused by your response Davey.

I have developed ribbons. Have owned and dissected Apogees, have spent countless hours developing bass diaphragms, MRTs, tweeters.
The ops questions are specific to an area that I have spent a mountain of time on. I gave what I have learned to him to do with as he sees fit.

I in no way second guessed the original design , however as wonderful as they are, they can be "tuned" to each system and environment to be all they can be, AND whats great about these designs is how easily tunable they are. Simply giving my experience with their designs as well as many similar.
 
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Sorry for my ignorance, but I don't have a clue who you are.....what your education is.....what your resume' contains.....what commercial designs you've been responsible for....what ribbon speaker companies you've worked for, etc, etc.
You never sign your posts, but always seem to refer to "your experiments"......none of which I've ever seen here on DIYaudio.com. Maybe I've missed them??

Feel free to PM me and let me know who you are and elaborate on your ability to comment knowledgeably about Apogee speakers.

Dave.
 
Spend some time experimenting with Q value, based on Davey’s info about notch (7KHz, gain -6dB). Have the best result with Q value of 0,8 (1,8 octave).

Below is the graph of both MRT measured at MLP, high pass filter at 450Hz, slope 12LR. It is visible from the blue line-the response without any EQ, there is mild hump starting from 2KHz.

The red line is response with PEQ (7KHz, Q=0,8, gain -6dB).

I am using target curve, so the sloping trend after 2KHz nicely suit the bass panel response.

Sounds very fine, a bit “softer” than my usual settings and my taste, but I will give some time to adopt my ears to this.

Davey, thanks again for the info.


An externally hosted image should be here but it was not working when we last tested it.
 
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Q definitions vary a bit, but in LspCAD the Duetta Signature stock notch filter calculates as Q=0.6. So, you're probably pretty close.

But, as noted, Q implementation varies quite a bit depending upon the DSP platform you're using.

BTW, your image is not showing.

Dave.
 
I cannot open image eather

DAMIC, you mention "soft" with respect to the effect of your trap. It is as you say wise to let ears acclimate before making decision. This area if a bit hot can make things like strings sound great BUT can also be siblant. I have found that as little as 1/2-1 db here can take it from HiFi to hi class.

Also as you mentioned "soft". Another area to play that can have a rather large effect is the woofer crossover. IMO Apogee got it right with the slopes and point. Its likely technically correct in many ways. However I have found that you can easily tailor the sound from layed back with great depth , to more forward with at least a precieved increase in dynamics with quite small changes to woofer cross over and slope. Small changes here can make a rather large difference where changes in the MRT crossover will have much less effect.

In the end the drivers are so extended and well controlled that these changes can be auditioned without a mountain of other work to get everything aligned again.
 
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I cannot open image eather

Me too, now. Before sending the message everything was ok. I will try again.


Imgur: The magic of the Internet

Imgur: The magic of the Internet

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I use Imgur and do not have problems with other forums. Hope, this time, image will open.

As Davey said Q value of 0,8 is close to 0,6, of course I will try another setting with 0,6 as well.

Thanks,
 
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