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active crossover install

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Posted on October 12, 2016 at 06:44:50
tberd
Audiophile

Posts: 8
Location: Texas
Joined: June 16, 2005
 Went to help a buddy with his 3.6R's. He wanted to install his Bryston active crossover. Anyway we connected it up with top end cables. Later I thought something was way off. I didn't say anything, wanted to see if he thought the same. About 3 minutes later here it came. A dead stare at me like I stole his wallet LOL. I said what? He said why does it sound filtered now and congested? Like we put a blanket over the speakers? I said well all those connectors, cables and electronic molestation you added to the signal path possibly??. We ran with the stock Maggie x-over settings. Long story short we removed the active gear and cables. He said we got the good sound back. The coloration was gone now. So why......... Told him if he wanted Maggie magic to install a tube pre and SET amps.

tberd

 

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RE: active crossover install, posted on October 12, 2016 at 06:53:35
grantv
Manufacturer

Posts: 7724
Location: B.C.
Joined: January 15, 2002
 -Something hooked up wrong?
-Settings incorrect?
-Bad amp for the top end?
-Bad synergy of cables?
Could be a number of things. I generally agree to keep things simple, but adding an electronic xover to my 3.6's improved things by a decent margin.
Try different cables, settings, check connections and that all IC's are not faulty. What amp previous and what amps with bi-amping?

 

RE: active crossover install, posted on October 12, 2016 at 07:19:35
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 Can you give a more detailed description of the sound with the Bryston biamp beyond the "Blanket" sound? Is is a lack of treble, presence both, a lack of detail or transients - sounding overly "rounded"?

 

RE: active crossover install, posted on October 12, 2016 at 07:31:47
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 When you say you ran the Magnepan stock settings, did you follow Magnepan's recommendation for active biamping? If so, it will not sound right. You need to emulate the OEM which means a 4th order (L-R) LP at 280 hz (not 3rd order at 250 hz) and a 1st order HP at 200 Hz.
The next question is what amps? Are they the same, and, if not, were the gains matched?

Finally, the obvious, were the cables connected correctly and the correct jumpers removed. It's real easy to reverse polarity or even direct the low end to the mid-tweeter (trust me I have been there).

I would not blame the cables and connectors if they sounded good with a single amp setup.

Also, A SET amp probably is not the answer as Maggies just love muscle. I do agree that a tube preamp (with SS amps) seems to work well.



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

 

RE: active crossover install, posted on October 12, 2016 at 09:09:34
Davey
 "Electronic molestation." I like it. :)
One wonders why Bryston even produced an active crossover or why so many users seem to use it.

Dave.

 

RE: active crossover install, posted on October 12, 2016 at 09:09:47
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 No way it is the cables and connectors. As neolith said, check that you hooked it up correctly. Also check that the phaseing is the right way. As the bass level increases by about 1.5dB, that will probably be the first thing you notice.

 

RE: active crossover install, posted on October 12, 2016 at 10:22:56
play-mate
Audiophile

Posts: 948
Joined: November 21, 2008
 Hey tberd

Constructing a crossover (active or passive) is no trivial pursuit.
Itīs actually very challenging to get phase, impulse and amplitude of each of the drivers to work properly together.
-and in this regard, the Bryston crossover is simply to limited in itīs fixed 24dB/oct. setting.

There is good reason that the stock crossover is asymmetrical and that the mid-driver is inversed, and I must report that I had my best audible results in "close-to" factory settings.
Digital crossovers have often the (huge!) advantage that they can time-align the drivers (especially delaying the bass) and improve coherence.

I tried hundreds of settings on my former MG3.3Rīs via digital crossover, and I can testify, Iīll never ever have it again without proper measurement assistance.

If youīre not able to exclude analog or digital streaming playback, there is only customised active crossovers to help.

However : the sheer dynamics, increased focus and breathtaking glory that (well setup) active Maggies can produce, is worth the extra hazzle in getting a well-configured X-over.

Kind regards L.
Hysolid // Mytek Brooklyn // Spectron Musician III // Analysis Audio Omega

 

RE: Key... Active measurement Assistance..., posted on October 12, 2016 at 12:30:32
BigguyinATL
Manufacturer

Posts: 3475
Joined: April 10, 2002
 Even my "Simple MMG biamp project would have been a nightmare without measurement - a passive crossover often is also an equalization timing and phase adjustment. When you reconfigure a passive loudspeaker to active, you need to measure before and after - just like the manufacturer does when he develops the loudspeaker.

Many manufactures and designers start with an active EQ - and then implement something similar with the passive components.
"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

Clarification and explanation, posted on October 12, 2016 at 15:26:42
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 I want to expand on my comment about the Magnepan recommendation for active biamping.
Magnepan spends a good amount of time and effort to optimize the OEM crossover before committing to production. It is unlikely that an amateur audiophile, like myself, would improve on the design. Therefore the ideal active crossover should simulate as closely as possible the OEM XO.
OTOH, the recommendation for active biamping is a compromise brought about by the limited function of the active crossovers available at the time production of the speakers commences. Most commercial crossovers have limited flexiblity. In particular the Bryston 10B cannot produce a 4th order LR without modification of the unit by Bryston and almost as important the choice of crossover points in the region of interest is limited to 200 Hz (perfect for the HP filter) and 300 Hz (close but no cigar for the LP filter).
If you want to do it right, your friend has a few choices:
1) Send the unit back to Bryston for modification
2) DIY - cheap and not overly difficicult to do with modest soldering skills using modules from Rod Elliott
3) Marchand XM-44 - the appropriate modules can be readily supplied by Marchand (cost about $50 for the 4 required modules). About $1000 new and includes the modules.
4) miniDSP (others can comment on the best unit - cost is $200-500 depending on the unit). Very flexible.
5) First Watt B4 (I believe it can give you 275Hz which is close enough to 280 Hz) for about $1500.
#3 and #5 come up for resale from time to time.
Finally a disclosure: I do have a Marchand for sale on Audiogon so I will refrain from making any recommendation about the various choices. I have tried to be as objective as possible in my comments.



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

 

RE: active crossover install, posted on October 12, 2016 at 17:57:28
Norman M
 I have bi-amped a 3.6R using a Marchand XM-44-2 (with modules as per Magnepan's recommendations found in the speaker's user guide) and Magnepan's XO-1 (also set following Magnepan's instructions (both that in the speaker's and XO-1 instructions). I used Bryston amps; two 7B-STs and a 4B-SST. (I've done the same using a Tympani IV-A.) Truth be told, listening to most program material at reasonable levels there was very little (if any) difference to be heard no matter how I listened to those Maggies, (either in their usual stereo configuration or a bi-amped one). No "blankets", "coloration", "electronic molestation" or anything else of the kind. There must either have been some human error involved in the manner your system was wired/set-up, or a problem associated with the Bryston X-O. My bet is on the latter!

 

RE: active crossover install, posted on October 12, 2016 at 19:39:21
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 Haha if it was you who installed the Bryston and all the cables etc then, given your advice to him to buy a SET ... I would suspect you simply configured it all wrong. ;-))

I've been running my Maggies 3-way active for over 15 years and not a single listener has ever said they sound congested!

I presume you just replaced the external passive XO boxes with the Bryston? What amps did you use after Bryston - on the bass panels and on the mids & ribbons? Did you feed the LP output of the Bryston to the bass amp and the HP output to the mid+ribbon amp?

Andy

 

RE: active crossover install, posted on October 13, 2016 at 00:24:23
BDP24
Audiophile

Posts: 1070
Location: Vancouver, Washington
Joined: September 12, 2013
 The First Watt B4 is a better active x/o for use with Maggies than is the Bryston. The B4 offers 4th order-24dB/octave capability, and frequency settings in 25Hz increments (from 25Hz into the 1250Hz area). Marchand can make cards to even finer graduations, but they contain opamps (if that bothers you ;-).

 

RE: active crossover install, posted on October 13, 2016 at 07:36:16
Norman M
 "I've been running my Maggies 3-way active for over 15 years and not a single listener has ever said they sound congested!"

I ran a Maggie Tympani using an Audio Research Corporation (active, tubed) EC-2A X-O and ARC tubed amplifiers over *thirty* years ago c/o any problem.

 

RE: Key... Active measurement Assistance..., posted on October 13, 2016 at 08:51:11
Davey
 "Even my "Simple MMG biamp project would have been a nightmare without measurement - a passive crossover often is also an equalization timing and phase adjustment. When you reconfigure a passive loudspeaker to active, you need to measure before and after - just like the manufacturer does when he develops the loudspeaker."

Actually, you don't. In fact, it's better if you don't.
Passive to active conversion (assuming your intention is to leave the existing transfer functions intact) is a very simple approach, and requires no acoustic testing of any sort. Neo has provided much of the required conversions in his spreadsheet and I provided a 3.6 working example many years ago on this very forum. (In fact, it's in use successfully by a number of PA lurkers.)
http://www.integracoustics.com/MUG/MUG/tweaks/davey/mg3.6xo.htm

If your intention is to re-engineer and/or improve the existing design(s), you better know what the hell you are doing regards acoustic measurements. :)

Cheers,

Dave.

 

RE: Key... Active measurement Assistance..., posted on October 13, 2016 at 09:26:32
BigguyinATL
Manufacturer

Posts: 3475
Joined: April 10, 2002
 Well my experience is otherwise. even if you want to mimic the existig transfer function you have to measure whet the transfer funtions are (not just the component values, because the driver has to be measured as pare of the transfer function. Even level matching LF to HF is better done with measurements - or at the very least customized band limited pink noise signals and the ability to quickly compare levels. but even you mind is terrible at distiquishing tone difference as your memory gets biased. This requires more rigor tobe employed in your set up. You have to listen to the HF noise signal first and then climb the LF noise signal to match, the repeat with the LF Fixed and adjust the HF upward to match and see how the end results compare - they were different by a couple dB each time I tried it... Using measurements before and after is far easier, and you likely can spend less than you cable budget to rent a very high quality measurements device... See link - Full disclosure I work for B&K

Of course, the great advantage of a Active crossover is veer away from the manufacturers design and see if you can make it better! The mananufacture always applies some limitations in the crossover design - related to cost, physical layout of the transduser - and let listening room may also place some restrictions on the performance with the standard passive design. With my MMG's I tried steeper slopes and higher and lower crossover frequency. I ended up with a bit higher crossover (1100Hz) and 24dB/Oct slopes and added a EQ and HP filter to better integrate with my subwoofers.


"The hardest thing of all is to find a black cat in a dark room, especially if there is no cat" - Confucius

 

RE: Key... Active measurement Assistance..., posted on October 13, 2016 at 09:38:18
Davey
 If you read again, I said "requires no acoustic testing."
Electrical-only testing (at each transducers terminals) may be required, and it has the distinct advantage of not containing any of the pitfalls acoustic testing (or listening) might. It also incorporates all parasitic characteristics of the crossover components.

However, computer simulation will achieve nearly the same level of accuracy electrical testing will......assuming the components in the simulation are fairly good. Simulation of Magnepan transducer and crossovers are more straightforward in this aspect since the driver impedance's are essentially resistive. Neo's spreadsheet contains electrical transfer functions of Magnepan speakers he's never measured (either electrically or acoustically), yet I believe them to be very accurate depictions.

Cheers,

Dave.

 

The great advantage of a Active crossover is [to] veer away from the manufacturers design..., posted on October 13, 2016 at 11:29:58
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 Sorry, I couldn't disagree more (see my post below). Granted some manufacturers often make compromises in the design or, more likely, in the implementation (quality of parts). However it is just as easy to use a 17.3 mH inductor as a standard 18 mH inductor when ordering in quantity. Magnepan was not cutting costs when they used a 4th order LP filter for the 3.6 when all their previous designs used less costly (less parts) 1st, 2nd or 3rd order filters. They may have save money by using lower quality parts but I don't feel that they compromised the design. BTW when I measured the values of the caps and inductors in my 3.7i, they were spot on with the design - close tolerances suggests that corners were not cut.
Obviously I can't argue with you that your configuration for the MMG sounds better to you than the original design but this is proof of nothing. It's anecdotal and may, as you noted, be particular to your room acoustics and/or your preferences. The bottom line is that you have arrived at a happy solution and that is great but I would not generalize from that experience.
As far as measurements, as Davey notes, my spreadsheet is based solely on mathematics - no measurements and no verification. Using the appropriate math, a one-to-one translation of a speaker-level crossover to an ALLXO will produce the same electrical response and, assuming no modification to the actual drivers, will give the same fs. There are other benefits from active biamping but changing the fs and phase is not one of them.
That said, I do use acoustic measurements to help set up my speakers and I find it beneficial. But this is done to position speakers and tune the room, not to modify the crossover.



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

 

RE: active crossover install, posted on October 13, 2016 at 12:20:47
andyr
Manufacturer

Posts: 12548
Location: Melbourne
Joined: September 2, 2000
 So, Norman ... you would agree that the OP must've screwed up his active implementation, somehow?

I personally think he probably fed the LP output from the XO to his mids+tweeters and the HP output to his bass panels. ;-)) (Which would certainly sound very weird!)


Andy

 

RE: active crossover install, posted on October 14, 2016 at 07:41:58
Norman M
 I most definitely agree that the OP could have "screwed up". I indicated that in an earlier post when I wrote about the possibility of "human error" being involved or a fault in his Bryston X-O. Being considerate of his ability to correctly wire up his system, I wrote it likely that X-O was at fault.
Now that I think back to my earliest experience bi-amping a Tympani (using that ARC EC-2A X-O), it's more like 40 years since I did that. I recall concluding back then, 'what's the big fuss about bi-amping'? Nearly most of the time (or perhaps all of the time) I couldn't hear 'any day and night' difference between the ordinary vs bi-amped configuration. If a were put to a 'blind' test, considering the time required to re-wire the system any difference in its sound would have been gone.

 

IME dipoles do not respond well to typical symmetrical steep crossovers, posted on October 18, 2016 at 03:22:24
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 I'd suggest he tries a 1st order high pass and 3rd low pass for the bass.

These will blend in phase quite well, the high pass might even be possible as a passive line level filter on the back of the amp's input sockets.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: IME dipoles do not respond well to typical symmetrical steep crossovers, posted on October 18, 2016 at 03:42:34
Roger Gustavsson
Audiophile

Posts: 2054
Location: Huskvarna
Joined: February 12, 2010
 If going from a 4th order to a 3rd order low pass, should not the phasing of the woofers be changed?

 

Yes, of course that is implicit they should be connected to match the panel's connections, posted on October 18, 2016 at 13:37:00
Timbo in Oz
Audiophile

Posts: 23221
Location: Canberra - in the ACT - SE Australia
Joined: January 30, 2002
 That is implicit with odd order slopes.


Warmest

Tim Bailey

Skeptical Measurer & Audio Scrounger


 

RE: IME dipoles do not respond well to typical symmetrical steep crossovers, posted on October 18, 2016 at 17:17:57
neolith
Audiophile

Posts: 4842
Location: Virginia
Joined: February 21, 2002
Contributor
  Since: December 2, 2004
 The polarity needs to remain inverted - remember Magnepan did not mention changing the polarity with their recommendation.

Here is the OEM xo (LP 4th order @ 280 and HP 1st order @ 200):

and here is the Magnepan recommended xo for biamping (LP 3rd order @ 250 and HP 1st order @ 200):

In either case the filters need to be "phase aligned". The output curves are similar and I expect good success with either but the 4th order will be closer to the original voicing.




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

 

RE: IME dipoles do not respond well to typical symmetrical steep crossovers, posted on October 19, 2016 at 08:52:31
Satie
Audiophile

Posts: 5426
Joined: July 6, 2002
 The acoustic rolloff of the midrange is between 2nd and 3rd order so the combined XO is legit in either alignment. In my case, with a line of Neo8 the rolloff is rather clearly 2nd order so the 3rd order alignment has clear benefit. Besides which, the 3rd order Ashly XO I use for the bottom LP has more flexibility with its Q control so you have a family of roloffs at any freq you are trying. .

 

RE: active crossover install, posted on December 31, 2016 at 20:23:18
watts
Audiophile

Posts: 536
Location: B.C.
Joined: June 30, 2004
 No further responses? hmmm....

As someone else who went through with the active biamping route several years ago it was a tremendous amount of work, but is well worth it. It is not as easy as simply inserting a box and a couple of extra cables. I couldn't have done it without the help on this forum; thanks guys. My 3.6's are a dream.

 

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