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In Reply to: RE: XO-1 for MG IIIa's posted by wbeau@yahoo.com on December 17, 2014 at 20:29:09
It is not a very useful unit for biamping. You need a real crossover, the XO-1 is not. I have one. I think it is just a pair of potentiometers for setting the bass level. You need to provide a couple of capacitors to cut the midrange. The bass will be fullrange.
Follow Ups:
The bass is not exactly "full-range" since the existing low-pass network remains in place. I hope that's clear to everybody.
However, I don't disagree. The XO-1 is an ill-conceived product. On the ten steps to a successful bi-amp configuration, the XO-1 only gets you up the first step.
Dave.
Hogwash I say, hogwash. I have and have listened to my bi-amped IV-As using the XO-1 and a Marchand XM44-2 (using modules having the characteristics the Tympani-IVA manual suggests, after all I am comparing listening to a Maggie, so I follow whatever Magnepan tells me to do). IMO I get superior results using the XO-1. I don't know if it has any relevance to a comment in this thread as to the resultant sound, but one of the wires in the Maggie's IV-A external cross-over box is to be clipped when using the XO-1, and mine is. (Anyone wanting to buy the newest and perfect, immaculate and barely used XM44-2, PM me with your offer.)
Norman,When you utilize the XO-1, you don't band-limit the signal applied to the woofer amplifiers. One of the primary advantages of bi-amping is this bandwidth-limiting since it increases the effective power of your system. If only bandwidth-limiting one of the amplifiers, it's preferable to perform it on the high-frequency amplifier.....as is done with the XO-1, but it's still just a small step on the way to a proper bi-amp configuration with all of those benefits.
Comments like "hogwash" are meaningless and silly. I'm simply describing the system configuration created by the XO-1. Maybe you haven't realized it, but your XM44 unit (at least) has the potential to create a preferable system configuration. I'm not sure why you weren't satisfied with it, but it's not because of the engineering advantages it encompasses.
Bi-amping can be a tricky system configuration to exploit fully. I'm not sure most folks appreciate that fact.
The XO-1 requires you to use two amplifiers, yet hardly exploits the potential advantages that creates.Cheers,
Dave.
Edits: 12/20/14
While I appreciate your comment(s), I'm the original owner of a pair of T-IVAs, to which I've listened to for over 25 years. I'm merely reporting what my ears tell me, and I don't think anyone wanted the XM44-2 to offer an improvement any more than I did. In brief, it didn't and AFAIAC the XO-1 could well have been made of apple pie.
Well, you're extremely vague with your explanations.I would be interested to understand the reason(s) why it didn't work since you had the XM-44 outfitted per Magnepan's recommendations for the IVA's. There must be some explanation, but I gather you're no longer interested and it's water-under-the-bridge?
Cheers,
Dave.
Edits: 12/21/14
AFAIAC, there's no reason it has to be "water-under-the-bridge".
Firstly, it's no easy task (for me anyway, as I'm 79 years old but proud to say so) to have switched back and forth between the 2 XOs at least five times, each time confirming my last impressions.
Firstly five RCA plugs have to be pulled from the first XO and securely fitted to the other (easy). Then all the speaker wires have to be disconnected from the speaker. The wires from the Bass amplifiers are directly connected to the speaker's Bass panels, as are the wires to T/M panels from their amplifiers. I'm using one Bryston 4BSST to drive the Tympani's IV-A's T/M panels and two 'monoblock' Bryston 7BSTs for their Bass panels.
No for the easiest part (sitting on my behind and listening): Whereas the XO-1 offered smooth 'liquid' type sound, that arising from the Marchand is coarse and 'grainy', in short ugly sounding. Initially I thought this was a singular listening 'aberration' or perhaps the RCA jack/plug connections were dirty. At the end of the first cycle, using DeoxIT I cleaned all the RCA plugs and jacks from my pre-amp's output jacks (currently an Adcom GFP-565) as well as the input jacks/plugs for all three amps, not as if merely pulling and pushing in/out all the plugs wouln't have accomplished the same thing.
As if all this isn't enough I feel like using this opportunity for some venting. I've had a perfectly miserable time with my Marchand XM-44s. The first one dropped dead, out cold and bupkes signal from any output jack. Mr. Marchand easily verified that and replaced the unit. He attributed the fault to a "loose connection". No big deal, s**t happens my (foreign) car manufacturer built and replaced from scratch an entire vehicle because they couldn't find and fix a "CEL" situation in the first after three attempts, not to mention that billion dollar rockets both manned and not, blow-up into pieces shortly after being launched. (Even though a XM-44 is NOT 'rocket science'.) So, I'm now well into the way of using my second XM-44 and one if its channels drops out, dead. Sometimes I 'forced' it back to life, by pounding on one of its rear corners. After several months of this, back it also goes to Rochester, Phil can't or wasn't able to confirm this problem even after it had been with him for over three months. All during that interval I was listening and enjoying my speakers using the XO-1.
So I connected up my third XM-44-2 and IMO its sound is lousy (as compared to my XO-1). "Water-under-the-bridge": I wish the unit were under the water and under the bridge. (Isn't there a Talking Heads' song that goes something like that "...under water...", Once in a Lifetime"? It would be representative of my good fortune with this unit that after double-boxing it and driving to or back from UPS (or USPS) that I get involved in a head-on collision, while attempting to sell it off.
Interesting commentary. :) I'm not sure why you're commenting on foreign cars or malfunctioning rockets. None of that has any interest to me or relevance to this topic.Reliability and customer service issues aside, other than the "grainy" evaluation, I still don't see any objective explanation. Did your system change in tonal balance in some way as a result of different filtering curves? Did you observe/make any polarity changes relative to the stock crossover setup which might have caused suckouts? Where your relative power amp gains and possible polarity reversals understood? Some type of disparate power amp combination? Etc? Etc? Etc?
If the Marchand crossover was configured correctly with the exact slopes specified by Magnepan, you can hardly blame Phil for that issue. (The blame would fall on Magnepan for that.)
The "grain" issue might be something else, and indicative of a problem with the unit. Or maybe you're just highly sensitive to the "sound" of op-amps? That would be a legitimate issue, but not one (directly) related to the concept/implementation of bi-amping.
I'm genuinely interested in what went wrong with your experiment, but you're not helping me or anyone else out with your comments. Just labeling my comments "hogwash" and providing meaningless rhetoric does nothing to further the understanding of Magnepan users who might consider the bi-amping route.
Cheers,
Dave.
Edits: 12/21/14 12/21/14
These words coming from you, (putting it politely) are hogwash:
"The XO-1 is an ill-conceived product. On the ten steps to a successful bi-amp configuration, the XO-1 only gets you up the first step."
You believe it's ill-conceived, OTOH and thousands of others find it serves a purpose and enjoy it. Perhaps in your mind you think telling us it is ill-conceived is in someway useful. To my ears and in my system it does what it was designed to do. I assume you have in fact listened to a XO-1 in Tympani system and are not just blowing hot air?
2/2 malfunctioning Marchands, ha, ha ha.
Sure it does what it's designed to do......that's not the point.
Yes, the XO-1 is an ill-conceived (my opinion) product, and I already explained (technically) why I think so.And please don't play the ridiculous you-can't-comment-because-you-haven't-listened-to-my-system card. (That's insulting.)
Much of this type of thing can be evaluated from the engineering perspective without first-hand experience. First rate sports car designers/engineers don't have to lap the Nordschleife to perform their jobs effectively.Thousands? Are you sure about that?
Dave.
Edits: 12/21/14 12/21/14
I'm willing to bet you are amongst the denizens here who can hear the presence of a fuse-holder, but not an active XO. :-) :-) :-).
It's mind boggling, the need for specially endowed power cords, speaker wire, interconnect, etc. when a big electronic device seated right in the middle of the signal path goes unnoticed.
The beauty of the XO-1 is that it is silent, and having absolutely no sound of its own, any listener wouldn't be aware of its presence unless they looked for it.
OTOH the X44-2 (if it happens to be working, and unfortunately IME that's a big *IF*) causes the sound to become grainy and once being made aware of this characteristic becomes increasingly irritating, and makes me shut down my system down and replace it with my XO-1 before the next listening session.
(BTW, I included that bit concerning rockets and my car only to indicate tolerance for mechanical failure, up to a point anyway, two out of two malfunctioning electronic cross-overs is unacceptable even though nothing is perfect).
Have you ever posted a picture of your system to give us a frame of your reference?
"I'm willing to bet you are amongst the denizens here who can hear the presence of a fuse-holder, but not an active XO. :-) :-) :-)."
Now you're resorting to snide insults?
I'm just trying to help here and that's why I queried you about the specifics of your bi-amp system.
If you change your mind down the road and would be interested in a serious discussion of the issues you encountered, you know where to find me.
My goodness.
Dave.
There are two issues here, one is whether Magnepan's suggested electronic XO is as good a match to the speaker as the one they developed for speaker level. Second is the question of whether the direct link from the amps to the speakers simply revealed their sound characteristics and those of the GFP565 and other components without the kind "smoothing" effect of the speaker level XO parts.
From my own experience the magnepan suggested slopes and elbow frequencies are a compromise to allow the use of commercial XO's with set slopes. The actual slopes and elbow freq. of the stock XO can be copied into Marchand's cards and would be a better fit. It does involve some work to determine them, but between Neo and Davey or Marchand himself, it should be doable. Unfortunately I don't have the files for my own back calculation anymore since I did not back them up and the PC they were on is long gone.
Having had a Bryston amp (4B NRB) and having heard Adcom preamps with Apogee's Centaur line and Adcom 5800 series amps and NADs, I am going to suggest that the clarity of the Marchand (assuming it is not broken/malfunctioning) is just bringing out what I remember these components sounding like - though the SST versions are supposed to have fixed that thin top end of prior models. It is also possible that other components are the source of this.
I know that once I had the Marchand in, I had to drop the Bryston amp and take out all the cheap commercial interconnects (and some of the brighter DIY jobs I did) and upgrade them to better balanced ones, which I did with commercial ones from JPS and many DIY versions. Speaker cable too became more of an issue too. The CD player also became a weak link and had to be upgraded with a better DAC.
Experiments with other passive crossovers at line level that were more transparent than the Marchand confirmed that the Marchand was not the source of unnatural brightness or grain. It was inadequacies up the chain that were revealed by taking out the speaker level XO. Also power conditioning and better power cords can be helpful.
If you like, you can send me a blank or filled set of Marchand's frequency cards and I can swap his little panny film caps for "kinder" foil caps. I can also try to get the values recalculated closer to Magnepan's stock XO again and set that up for you to try. Since I went with PLLXO/hybrid permanently, I have sold off my Marchand XM44 3 way so can't test the cards at home anymore.
One of the better replies I've seen you type on here. Especially the part about relative differences between Magnepan recommended slopes (provided to Marchand) and the stock crossover curves. This is part of the info I was trying to get (without success) from Norman.As you might be aware, I advocated duplicating Magnepan stock crossover slopes with active, line-level versions many years ago on this forum. If you look in the "tweaks" section you'll see a couple of my designs from well over ten years ago.
I'm not saying that duplicating curves is necessarily preferable, but it does have one advantage, and that is that it establishes an apples-to-apples baseline comparison for relative differences in tonal balance when users transition to bi-amped systems. Anything else is apples-to-oranges and introduces other variables that can be misinterpreted or misunderstood by users when making evaluations.
This is a basic concept, and one which I'm surprised to say has flown over the head of many users on this forum.Happily, these relative differences can be easily measured and/or simulated. Neo has done a lot of this with his excellent spreadsheet......which I don't think a lot of people have REALLY looked at. :(
Knee-jerking rejections of bi-amp principles based on faulty conclusions is fairly widespread and mildly irritates me. Unfortunately, there's not much I can do about it because once an audiophiles mind is made up, it's made up. :)
Once again though, you're also doing a lot of speculation in your comments. I've given up hope of breaking you of that habit. :)
Cheers,
Dave.
Edits: 12/21/14
The speculations are more valuable since they give you a direction to try. There is no reason to avoid speculation and I still have hope that you develop the aptitude for it and participate. You have extensive knowledge and experience and you are not using it to the fullest by refraining from speculation.
I only tried the maggie slopes since something seemed off on all LR4 after trying out the new mids and measuring them I had a good idea of what they could do but the LR4 XO didn't do it. But the stock XO slopes, fc's were not useful for an equidistant positioning. I tried an all LR2 setup in equidistant positioning and 1st order mid bandpass and 2nd order elsewhere and also all 1st order, which did best in resolution for the equidistant positioning. The most uncanny precise imaging I have ever heard outside of a Beveridge ESL.
I have used Neo's spreadsheets a lot a couple of years back when Davy and I were trying to "re-engineer" the 3.3 and IIIa in small increments. He is back at it on and off.
There's a difference between speculation and guessing. I'm being somewhat charitable when I label your comments "speculation."
I do speculate occasionally, but I do it based on valid data points. Problems arise when you speculate from an invalid premise or assumption.
When someone suggests to me that I just accept the nonsense of Ric Schultz but just figure out a way to explain it, I know I'm dealing with someone who's grasping. That's where you have to be much more critical in your thinking. Just a suggestion.
Cheers,
Dave.
Yes, much guessing is going on and very often it is far less time consuming to just try it rather than research the issue and calculate (if possible) what would likely happen. And if the results are audible and an improvement then you can also drop the time for measurement and analysis.
We aren't here to establish the science, we are here for tweaking to get better audible results in our setups. If it seems to you like Brownian motion, that is fine.
I have no problem posing a WAG and have you pop up and go whack at it. It is a good thing over time.
Guessing is fine......as long as it's stated as such and not couched within another context.
The analogy to Brownian motion is silly. Your efforts are not random.....just misguided in many instances. In my opinion.
The "science" is well established, but the understanding of its application seems not well understood by many audiophiles. (I see examples of this all the time on this forum.)
Tweaking does not trump the "science" and engineering of these systems. In fact, the word "tweaking" should be struck from audiophile language everywhere. :) It's a horrible label that enables all sorts of misguided thinking to invade the decision making process.
Cheers,
Dave.
Here some pictures of the Magnepan XO-1. A plastic box with two potentiometers and six RCA-connectors. You will have to solder in two capacitors yourself.
http://www.forumbilder.se/DEV78/img-9403.jpg
http://www.forumbilder.se/DEV78/img-9404.jpg
http://www.forumbilder.se/DEV78/img-9404.jpg
http://www.forumbilder.se/DEV78/magnepan-xo-1-page-1.jpg
Edits: 12/22/14 12/22/14
In my ignorant opinion a problem with some of that of that is ultimately it's akin to dealing with small differences (if any at all) between two very large numbers. In science and practical matter's that's a no no. I've removed the Adcom GFP-565 from the signal path and drive the amps using a Adcom SLC-505 straight line controller, and more recently a Schiit passive pre-amp, Sound differences (if any) are miniscule or the result of one's imagination, or the precise position of your head when listening.
The over-all sound of the system remains the same, Adcom or not. Naturally one likes to tell themselves they are making a difference, and IMO particularly so in this hobby.
We are in pursuit of improvements and we gain experience and accumulate observations as we go along.
You are right that the signature of a Tympani loading the room is going to be the biggest factor (doesn't that make you happy..) and once you have enough power for it, which you do, and have separated the power drain on the bass from the power supplying the top then improvements in performance will be smaller in the move to line level active and will be mostly in clarity and more controlled bass.
Since your experience with the Marchand XO has been so bad I suggest you try this with a reputedly better sounding unit that is easier to adjust by the consumer. The First Watt B4 crossover. There is one on sale on audiogon by Reno hifi, a pass dealer.The filters are fully adjustable in close increments without soldering so you can reproduce the stock maggie XO at line level.
I am thinking that you are sensitive to coherence like Davy (UK) who gave up for a while on bi/multi amping and went with the stock XO and selected parts upgrades.
Yes, I forgot the passive crossover. I even have a manual for the XO-1... The main thing with going for bi-amping is to use an active crossover on the basses.
For the OP.....if you can't find one, you can build one pretty easily. There's nothing much to it.....it's just a series capacitor for the high-pass leg, and a potentiometer attenuator for the low-pass leg. Just a couple of bucks worth of parts.
Dave.
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