Tri-Amping ADW Duetta with active Crossover - foolish?

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A splendid morning good people of this here forum! (I'm on vacation. Can you hear it? I can hear it. :D)

For the last eight years or so I have owned a pair of Duetta speakers by ADW, featuring three Eton chassis, and by and large I am pretty happy with them. Possibly I have been reading on the internet too much .. but since I have a few amplifiers kicking around, I started thinking about tri-amping the speakers. I was adverse to the thought of a digital crossover, but since my room is less than ideal I guess the advantages of easy room correction far outweigh the drawbacks (that is: my prejudices).

I believe an active crossover to be more ideal than the passive ones in the speakers, after what I have read. My plan was to employ my NAD C372 Solid State Amp for bass and two Mingda MC34-B for mid and high range respectively. I toyed with the idea of triode strapping the one for the tweeter - or both.

After some reading I zeroed in on a Xilica XP or XD 4080, the main difference being that the XD is capable of FIR filtering and costs about twice as much. Here now are my questions:

1. An audio engineer friend suggested that mixing amps was a horrible idea; he said that this could cause the acoustic crossover point to shift due to unlinearity. Is my plan foolish?
2. Whether or not FIR filters for the crossovers were a very good idea or superfluous, the sources wildely disagreed. Do you have any promters as to whether it is a good idea to spend the extra money?
3. Are there any devices better suited to my needs that do not involve an extra PC?

Thank you and best regards :)
 
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So this is essentially speaker building, which requires measurement and analysis and crossover design. Doing it digitally makes things faster, and less expensive, but the complexity is still there.

Do you know how to make a good 2-way crossover at all? In any domain? That's one area to learn about before spending money.

Next, you might just like to add EQ, and leave the existing crossover alone. Start there. If you can't make it sound good then, going active and ripping out the existing crossover will be a mess. :)

Also, never forget the value of room treatment. Bass traps make EQ possible below 200 Hz.

Best,

E
 
So I just took a look at the Duetta. Here's my suggestion:

Use a hybrid approach with a 2-channel DSP amplifier (see Madisound, miniDSP or Hypex).

Rip out the woofer to mid portion of the crossover and leave the mid to tweeter section alone.

Use the DSP as your woofer to mid crossover, and add EQ only to the woofer portion.

Focus on the woofer / mid integration (level, crossover slopes, delay) and try to avoid using global EQ. Add EQ only to the woofer portion. If you have to use global EQ you probably messed up the crossover.

Best,

E
 
Do you know how to make a good 2-way crossover at all? In any domain? That's one area to learn about before spending money.

Next, you might just like to add EQ, and leave the existing crossover alone. Start there. If you can't make it sound good then, going active and ripping out the existing crossover will be a mess. :)

Also, never forget the value of room treatment. Bass traps make EQ possible below 200 Hz.
Good evening, thanks for the input.
Why is this more like speaker building? Because of the different amps? Is it much easier if you use the same kind of amp?

I can make passive crossovers. I don't know about the "good" part though .. It seems to me there is more than a little experience in choosing the right topology and components. I'm not sure what analoge electronics has to do with it, since this digital stuff seems to be a rather different game. Except for the measuring of course, which kind of had to happen one way or another.

Optimizing the very much not ideal room is sadly mostly out of the question. It is hearing-, dining- and living-room and as such not entirely my domain. ;) It is simply something I cannot change and will not be able to change for some years to come.
 
Sorry, let me be a little more clear.

By integration I meant driver to driver integration. We can ignore the impedance issues of passive crossovers which affect component selection, but we cannot ignore the frequency response, slope, phase and physical delays inherent in multi-way speaker design.

In passive and active crossovers, the final response of each driver is electro-acoustical. That is, the output is the additive results of the driver response itself, where it is located in 3 dimensional space, as well as the electrical signal it receives.

So, when you have two drivers each with their own filter section associated with it, you are attempting to seamlessly merge all of this together.

To do this well you must be able to measure each driver, and simulate the final result.

What DSP does very nicely is it keeps you away from buying a bunch of caps and coils and resistors, as well as soldering or physical part replacement. It also lets you increase the delay to achieve better crossover matching.

But this is not trivial. It is not "set high pass to 12 dB per octave at 2,500 Hz" simple.
 
I triamp my Dali 18 mk2 with a 3way analogue active xover. It was very easy to ajust levels by ears. Took some time though. First i ajusted roughly and then very small adjustments during a couple of weeks. Sound is so much better than with the pasive x-over. I dont know if the improvement are as dramatic for most speakers, since mine are pretty old- and so the components of the x-over off coarse
 
Hi,

Much have been written in German forums about the Duettas. From my point of view there's really an issue with the lower passive crossover. Due to the simple filter the woofer shows a classic single note response and the midrange driver gets easily overdriven by 50 Hz signals. With an active crossover both problems do disappear completely and the performance of the speaker should improve significantly.

Hence going active isn't foolish at all. If you keep the passive crossover in the tops (as eriksquires proposed in post #3) a simple 2x2 channel DSP is all you need. Using different power amps is allowed, choose whatever sounds best. :)
 
1. An audio engineer friend suggested that mixing amps was a horrible idea; he said that this could cause the acoustic crossover point to shift due to unlinearity. Is my plan foolish?
2. Whether or not FIR filters for the crossovers were a very good idea or superfluous, the sources wildely disagreed. Do you have any promters as to whether it is a good idea to spend the extra money?
3. Are there any devices better suited to my needs that do not involve an extra PC?

1. Not correct, I have class D up to 350Hz and AB on mid and highs, works great. You have to take care on amp's gain (measurement necessary).

2.FIR filters works very good on mid and high freq., I would go to xo with FIR.

3.I can recommend similar, Dynacord DSP600.
 
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Hi,

http://www.diyaudio.com/forums/multi-way/286310-active-crossover-benefits-6.html#post4604828

The whole thread is interesting to read and some may recognise themself. ;)

Your friend sound engineer is plain wrong about the tube amp changing freq.

About FIR . I ve heard Xilica, did prefer the Lake but this is not budget minded. My use of fir is for filtering duty only and my own unit doesn t allow to load your own template so room acoustic treatments is not allowed with this particular hardware. I can t remember if Xilica is an open system (if you can upload your own kind of filters). If it is you could do some acousical correction too if it is like mine you ll need an other box for that. Like the DIRAC live from minidsp for example.

BUT don t expect this kind of treatment to solve a bad acoustic behavior! You ll need some passive treatment ( read acoustical treatment like bass trap and such) if you plan to do so. The fir come last and are the cherry on the cake, NOT THE CAKE! ;)
 
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