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MGIIIa plus Sony active crossover TA-D88 / TA-D900

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Posted on May 4, 2015 at 11:34:43
ntom@dsl.pipex.com
Audiophile

Posts: 3
Location: Surrey
Joined: May 4, 2015
 just got my hands on a Sony active crossover.

I have 4 x Denon 4400a monoblocks that I currently use to bi-amp the Maggies using stock passive external crossover. I have spare 4 x 640 Crimson monoblocks.

Was hoping to use two of these these, in addition to the Denons to go active with my MGIIIa's.

The MGIIIa is a 3 way. In addition I use an Active REL Stadium sub for the lowest registers.

The Sony active crossover is up to 4 ways... which should work.

Will be using with either a Musical Fidelity pre, or more often my Marantz AV7005 series processor.

Does anyone else use this combo?

1. Anyone care to suggest crossover settings?
2. What would be good software to use to assist set-up?
3. Do i just remove all passive components & connect each power amp directly to a driver? Is this OK with the ribbon tweeter?
4. Which amps on which speaker components and why?

Thanks for any insight!

 

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RE: MGIIIa plus Sony active crossover TA-D88 / TA-D900, posted on May 4, 2015 at 12:30:59
MWE
Audiophile

Posts: 2202
Location: Burlington, NC
Joined: June 8, 2000
 Do you have a link to info re: the specifics of the Sony XO? Knowing its capabilities would be a good start. Software-based units are beyond my ken but many others here use them regularly.

Mark in NC
Mark in NC
"The thought that life could be better is woven indelibly into our hearts and our brains" -Paul Simon

 

RE: MGIIIa plus Sony active crossover TA-D88 / TA-D900, posted on May 4, 2015 at 18:28:18
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 I am not familiar with this XO unit but from what I could gather from a Google search, it provides 4th order Bessel filters at a few frequencies. Certainly you can hook up your MGIIIa's but I suspect the results are going to be less than stellar, not because of the quality of the unit but because it will not optimally match your IIIa's.



"Our head is round in order to allow our thoughts to change direction." Francis Picabia

 

RE: MGIIIa plus Sony active crossover TA-D88 / TA-D900, posted on May 4, 2015 at 20:55:38
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 I don't think you will have a problem using it with the MGIIIa despite having nothing to do with the original slopes of the original XO design.
For better clarity. I woud try to replace the midrange bandpass filter with a passive 1st order implemented with just two caps and a resistor and try to match it to the other drivers on the 4th order Bessel filters on the Sony XO.
Alternately, I would also consider just using the sony to do Sub Bass and the mid with the mid-tweeter done with a passive line level network at 1st order.

From my own experience with 4th order and 3rd order filters in the analog the phase shift in the midrange bandpass is too steep and has overtones out of phase with the fundamentals. Some people are not bothered by it in the least, others are sensitive to it. That is why I suggest using the Sony only as a filter for the drivers other than the midrange, or only as a high pass for the mid and tweeter signals, which can then be done at 1st order (or first and 2nd).

Davy (UK) posted an implementation somewhat similar to this hybrid active and passive line level XO. Search for his posts on that.

To answer your Qs
1. using the sony to do all the XOs I would suggest
sub to bass at 40-50hz
bass to mid at 500 hz
mid to Tweeter 2khz or 2.5khz if the tweeter ends up sounding strained (which it shouldn't

using a 1st order mid bandpass I would take it up to 700hz and 2.5 khz and play with the sony settings to match that. I would not promise that you will necessarily find a perfect match.

Using the sony only to do the mid via its HP section I would still do it at 500 hz and do the mid to tweeter XO at about 3 khz.

2. REW + calibrated measurement mic

3. I think you can do just that, and run wires from each driver to a set of new binding posts on the connector plate.

4 I would say that the two amps are spec'd rather closely so I would try both setups - use the Crimsons on the mid and tweeter or use the Denon 4400 on mids and tweeter - I probably would not mix the two amp designs on the mid and tweeter. But I think they are way overkill, particularly for the tweeter - which should do just fine with 25-50 watt @4 ohms amp. But should be capable of 2ohm loads.

While I like the 4400 I am entirely ignorant of what the Crimson amps sound like.

 

RE: MGIIIa plus Sony active crossover TA-D88 / TA-D900, posted on May 7, 2015 at 06:39:39
ntom@dsl.pipex.com
Audiophile

Posts: 3
Location: Surrey
Joined: May 4, 2015
 Thanks for the feedback.

The TA-D900 is very similar to the TA-D88B, for which there is a little more info around. I've got a link to the service manual somehere & will post when I find it again!!

Essentially it's up to 4-way design utilising steep 24dB/octave Bessel filters.

It has replaceable modules allowing a varying range of crossover points from 50Hz upwards.

Circuits all DC & dual mono design.

I've never used any analysis software so will take a look at REW.

 

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