AudioCircle
Other Stuff => Archived Circles => General Archive => Topic started by: randog on 25 Oct 2004, 09:14 pm
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My Marchand will be here soon... however...
I'm curious if anyone knows of a 2-channel audiophile quality preamp with a built-in active crossover for bi-amping and/or implementation of subs.
IRD is planning one (The Audiophile), but the development is on hold.
Randog
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I asked the same question on another forum and got this:
http://www.clarityeq.com/dsp-product/PDC26P-Preamp.html
It was out of my price range, can't remember what the price was, just that it was more than I want to spend.
EDIT: The price of the above unit is $3,450.00
So I'm impatiently waiting for the audiophile from IRD
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I'd check with BESL (bamberglab.com). Phil is the MAN when it comes to active setups. He's a great guy who will not steer you wrong. Some day, I hope to own some of his speakers in an active setup.
J
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There is quite a lot of talk on the apogee forum (I frequent for the info) on active amping. Most of them are subscribers to using digital xo's and digital EQ's. Apparently the Behringer digital EQ's and digi xo's can be made to sound nice relatively easily by minor part swapping and dejittering. Also they highly recommend not using the internal vol control but instead using something like Davey's 6ch VCA control.
Davey send me a bunch of info on it and I am going to give it a shot for 2 channel first. Pretty cheap and not terribly difficult looking.
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Hmmm... I thought as much... the easy solutions are hard to find.
Good ol' Curt's ideas are good, we just gotta get him back in the lab to finish them! :wink:
I was also bugging Curt (as were a couple of others) to come out with a 6 channel preamp without processing to support 2-channel as well as multi channel music and HT. I'm completely baffled there's not one on the market (OK, there is, but it's an arm and a leg). He seemed very interested in that as well.
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My Marchand will be here soon... however...
I'm curious if anyone knows of a 2-channel audiophile quality preamp with a built-in active crossover for bi-amping and/or implementation of subs.
IRD is planning one (The Audiophile), but the development is on hold.
Randog
Randog,
Even tho' that good Aussie company DEQX have one, I don't necessarily think that combining your active crossover with your pre-amp is a good thing.
I run an active setup - I've built 3-way active crossovers for my Maggie IIIas. This means I can have a (mono) xover box and 3 monoblock amps sitting right behind each Maggie - with 3 very short speaker cables.
My stereo pre-amp, though, sits next to my sources - up the other end of the listening room.
Regards,
Andy
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I was also bugging Curt (as were a couple of others) to come out with a 6 channel preamp without processing to support 2-channel as well as multi channel music and HT. I'm completely baffled there's not one on the market.
this is a 5-channel preamp.. closest thing I've seen:
http://www.audiocircle.com/index.php?topic=11999&highlight=margules
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Randog,
Even tho' that good Aussie company DEQX have one, I don't necessarily think that combining your active crossover with your pre-amp is a good thing.
I run an active setup - I've built 3-way active crossovers for my Maggie IIIas. This means I can have a (mono) xover box and 3 monoblock amps sitting right behind each Maggie - with 3 very short speaker cables.
My stereo pre-amp, though, sits next to my sources - up the other end of the listening room.
Regards,
Andy
Hi Andy,
I'm not sure the difference here. You can still have short speaker cables by making your long run from the crossover to the amp. It's either that or from the preamp to the crossover in your case. So it's basically a wash, right?
Randog
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Hi Andy,
I'm not sure the difference here. You can still have short speaker cables by making your long run from the crossover to the amp. It's either that or from the preamp to the crossover in your case. So it's basically a wash, right?
Randog
Not quite, randog ... as after each 3-way mono crossover comes 3 ICs - 1 to each amp.
Regards,
Andy
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Hi Andy,
I'm not sure the difference here. You can still have short speaker cables by making your long run from the crossover to the amp. It's either that or from the preamp to the crossover in your case. So it's basically a wash, right?
Randog
Not quite, randog ... as after each 3-way mono crossover comes 3 ICs - 1 to each amp.
Regards,
Andy
i agree - i'd much rather have yust one long pair of ic's from the pre to the x-over, than a separate pair of ac's from the x-over to each amp...
but, randog, i am sure that if ya asked phil marchand, he'd be happy to custom make an x-over for ya w/a separate wolume pot that controls everything, as well as the low-pass/hi-pass controls. likely wouldn't add too much to the cost...
doug s.
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DEQX is a nice solution but $3500+! ouch! The Behringer XO + EQ + Davey 6ch Vol control plus some parts for minor mods is <$1500. Also, there are some that believe the later is better as well. Of course there is more IC's but also more flexibility.
I have been reading up a lot on active setups lately and there really seems to be two camps; those that don't believe in going active at all and those that believe in going full digital. There is actually far less in the active analog approach. Its seems that the critics of the active analog approach say that no off the shelf active analog xo is very good or flexible enough to get it right. Don't know if that is true or not but certainly you are quite a bit more limited than newer digital xos. However, there is also one more school of thought often overlooked. It is the camp that believes in implementing a passive line level crossover before the amp rather than after the amp. If you split the signal from the preamp into seperate duplicate signals (preferrably seperately driven like the two outputs on the Purist) then you can replicate the passive crossover of your speakers in the line level with correspondingly smaller caps and inductors.
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Josh, this is really interesting info.
What's the true definition of passive and active crossovers?
With the implementation of active crossovers for subwoofers you actually put the signal through 2 stages of crossover(ing), first the active, then the passive in your 2-way monitors. I assume this is less than ideal (and far from efficient).
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AFAIK I believe it means whether it uses passive or active components. I.e. if there is a power cord going to your xo it is active. ACI's line level filter is a passive line level xo, or atleast one side of one.
By the way, I am not suggesting that any of these camps are better than the others as I have no experience with trying any of them. However, I am leaning towards the digital xo or passive line level xo approach ATM for my own experimentation. The later is easier to integrate with analog sources and current analog components but I feel the digital approach has quite a few advantages at least on paper.
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That makes sense (doh).
You're too quick for me! You responded while I was adding the last sentence to my previous post. 8)
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Not quite, randog ... as after each 3-way mono crossover comes 3 ICs - 1 to each amp.
Regards,
Andy
Right... gotcha.
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I think if you are tinkering with your own speaker design then what might be useful (by the way this isn't my idea, but csero's) is buying a cheap analog pro xo on ebay and using that to experiment with slopes and points until you feel that you got what you want, then you can implement your passive xo and tweak it to its best potential. In this case you would implement the passive xo in the line level if that is what you wanted to do. Then you can flip the pro xo back on ebay again when your done with it, or keep it for future projects. I plan to pick one up for toying with.
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It is the camp that believes in implementing a passive line level crossover before the amp rather than after the amp. If you split the signal from the preamp into seperate duplicate signals (preferrably seperately driven like the two outputs on the Purist) then you can replicate the passive crossover of your speakers in the line level with correspondingly smaller caps and inductors.
This camp is intriguing... hadn't heard of this before. Are any of the better known crossover guru's working in this arena? Are there any successful products on the market? Does it need to be tailored specifically for the speakers (like typical passives are)? Again, this is pretty interesting...
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One thing I didn't mention is that I would still probably get a pro xo for experimenting even if I wanted to buy a Marchand xo. With Marchand it seems that either you have to buy their most flexible xo and lots of different cards for points, and sometimes you even have to prespecify the slope. I think it would be better to experiment with a more flexible xo first and when you are satisfied then order the marchand that best suits your needs.
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Randog,
(I hope I am not derailing this thread too much). Welbourne labs used a variation on a passive line level xo in their Reveille xo. Apparently they had an option for the high pass to be passive (most sensitive part) and then the low pass was an active xo. They must have felt this was the best compromise.
I briefly spoke with Occam about this idea and he was aware of it. I think he mentioned some source that taught how to implement a passive line level xo. Maybe we can get him to tell us what that source was, as I already forgot.
My hunch though is that preamps with seperate line drivers, like as in the Purist, are better suited to drive a passive line level xo. Maybe that is the reason for the hybrid by Welbourne, since most preamps don't do this.
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One thing I didn't mention is that I would still probably get a pro xo for experimenting even if I wanted to buy a Marchand xo. With Marchand it seems that either you have to buy their most flexible xo and lots of different cards for points, and sometimes you even have to prespecify the slope. I think it would be better to experiment with a more flexible xo first and when you are satisfied then order the marchand that best suits your needs.
you *can* get a wariable frequency x-over from marchand, but phil sez it's not quite as transparent as his units that require the plug-in modules.
http://marchandelec.com/xm6.html
(http://marchandelec.com/xm6.gif)
as the modules for the non-wariable frequency models are only ~$6 each, i think that would still be the way to go. replacing the modules takes only a couple minutes, even less if ya don't have the lid screwed down...
doug s.
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Agreed doug, that I would lean towards the non variable points. But slopes are not variable AFAIK. I think getting a cheap pro xo that is very flexible to experiment and then commit to a high end solution like marchand would be a better idea. Maybe an even better idea is to design the passive line level xo we were talking about, but that is not without it's downsides as well.
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This camp is intriguing... hadn't heard of this before. Are any of the better known crossover guru's working in this arena? Are there any successful products on the market? Does it need to be tailored specifically for the speakers (like typical passives are)? Again, this is pretty interesting...
No idea bout the first question. The later is of course, yes it needs to be tailored to each speaker in question, and for that matter each set of amps you intend to use. You can see why this is an often overlooked solution. It may in fact be one of the better solutions but it needs a lot of thought, care and planning to build the system up to work correctly in this case. This is not the sort of solution an audio dealer wants to promote because it won't allow for amp swapping every month when the new and greatest product comes out. Same with speakers etc. So not for the flavor of the month club at all. However, if you have committed to a pair of speakers indefinitely and want to take them to their best this may be a great way of doing so, I don't know for sure but it seems logical.
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Agreed doug, that I would lean towards the non variable points. But slopes are not variable AFAIK. I think getting a cheap pro xo that is very flexible to experiment and then commit to a high end solution like marchand would be a better idea. Maybe an even better idea is to design the passive line level xo we were talking about, but that is not without it's downsides as well.
personally, unless the speaker drivers in question have weird response characteristics that would require special notch filters, etc, that wouldn't be addressed w/standard x-overs, i would just stick with 24db/octave slopes. sharp cut-off & keeps the drivers in phase.
marchand also offers an interesting line-level passive x-over, but it looks like ya really would wanna know the slope before ordering; plug-n-play frequency changes don't seem to be part of the deal here. perhaps phil could install sockets for swapping out the caps-n-resistors...
http://marchandelec.com/xm46.html
(http://marchandelec.com/xm46b.jpg)
(http://marchandelec.com/xm46.jpg)
doug s.
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Well lets be fair, the 24db/octave slope keeps the signal in phase *only* near the xo point and not wideband. Meaning the 24db/octave slope has, to the best of my knowledge, a larger impact on overall wideband phase then say a 6db/octave slope. There are more schools of thought out there than just BC of VMPS that believe that anything above 12db/octave slope causes phase errors too great to provide seemless driver integration (outside of the xo point) and coherent sound. I am in no camp here just stating what I have learned. I would personally like to play it myself to form an opinion rather than just state what I have read somewhere.
Of course, if you use a digital xo then you don't have to worry about phase!
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Well lets be fair, the 24db/octave slope keeps the signal in phase *only* near the xo point and not wideband. Meaning the 24db/octave slope has, to the best of my knowledge, a larger impact on overall wideband phase then say a 6db/octave slope. There are more schools of thought out there than just BC of VMPS that believe that anything above 12db/octave slope causes phase errors too great to provide seemless driver integration (outside of the xo point) and coherent sound. I am in no camp here just stating ...
yes, i know - a *lot* of speaker designers (thiel among them), believe 6db slope x-overs are the only way to go. i believe that there's good stuff from *both* schools. i like thiel speakers a *lot*...
but, if *i* am gonna get into any diy-type stuff, then it's gonna be 24db/octave at the line level. anything else is way too much above my knowledge & abilities. and, i believe all the phase errors that brian (& jim thiel?) talk about are related to x-overs at the *passive* speaker level. i do not believe these are of as much concern when at the line level. even brian cheney uses active 24db/octave x-over in his top model, to cross his woofers over to his midrange panels.
http://www.vmpseurope.com/e/p-st3.htm
and, this is what he recommended to me, when i queried him about going active & bypassing the passive low-to-midrange x-over in the rm-40's...
doug s.
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You are probably right doug, that active xo probably is far less harmful to phase at steep slopes but AFAIK I think it still does have the impact still. I think I am going to try playing with a digital xo setup at some point in the near future, maybe not with my RM40's but probably with my own contraption.
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You are probably right doug, that active xo probably is far less harmful to phase at steep slopes but AFAIK I think it still does have the impact still. I think I am going to try playing with a digital xo setup at some point in the near future, maybe not with my RM40's but probably with my own contraption.
i'm not so sure the negative impact has to do w/active vs passive so much, as doing it at the line level vs doing it at the speaker level. (ie: before vs after the amps). which is why marchand has a special *passive* x-over to work at the line level, *before* the amps.
in any event, i would certainly be interested in your results w/your "contraption". :wink: someday i hope to do a line-source "contraption" of my own! :)
doug s.
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I just don't see how doing it line level instead of speaker level is going to get around the problem is all. You could be right but it doesn't seem obvious to me.
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I just don't see how doing it line level instead of speaker level is going to get around the problem is all. You could be right but it doesn't seem obvious to me.
to be honest, i am not sure myself, on a technical level. intuitively, it makes sense, as on the line level, it's only the amp that is seeing the change from a line-level x-over. distortion/efficiency-reduction levels are typically far lower here - look at typical frequency response, distortion levels & signal-to-noise ratios of active x-overs. this way, the speaker is only seeing a limited frequency from the amp, & its drive ability is not effected by capacitors, chokes, resistors, etc... it would be nice to get some feedback about this from experienced diy speaker builders or professionals...
doug s.
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I certainly am no expert. Rather consider me a blind monkey fiddling with crossovers to see if monkey music comes out of speakers. I can howerver report what I hear from an active triamping set up. I am using a Marchand XM 44 with RM 40s. You can check my 2-channel system for associated equipment. Sticking strictly with 4th order slope, I got the Larger sub to 80 H, two woofers between 50Hz and 600 Hz, and the ribbons (using the existing passive xover network between the panels and the FS tweeters) down to 200 Hz. What I get is a very clear sound. I just about have the tonal balance where i want it. I have tried all sorts of passive setups-- sigle wire, bi-wire and passive biamping with attenuator on the tubes. I get the best sound with active x-over with these speakers. With the pots on the speakers and line level control on the x-over I can balance the all important (for vocal representation) 200-700 Hz balance just right. FYI, Mega woofer rolls off at 100Hz and midbass woofer rolls off at 600Hz. Both see the same signal but there is a filter that limits its range for the megawoofer.
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so you allow significant overlap b/w the panels and the upper woofer? interesting. Is there any perceived cancelation?
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I tried the lowpass for the woofers at 200Hz as Brian recommended, but it sounded too bright and thin. The serial first order coil Brian uses slopes up to 600 Hz. So, I tried 200, 300, 400, 500, 600 and 700 (all 24dB) and settled on 600. I don't hear any cancelation. Rather the woofers add that woomp to the voices that makes Johnny Cash sound like Johnny Cash. It also provides that huskiness to Natalie Merchant and warmth to Norah Jones that makes them special. On operatic music, I hear the voices through the speakers just like what I hear in opera houses. All in all, the sound is clearer with active x-over and you have more options to get the right tonal balance.
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I tried the lowpass for the woofers at 200Hz as Brian recommended, but it sounded too bright and thin. The serial first order coil Brian uses slopes up to 600 Hz. So, I tried 200, 300, 400, 500, 600 and 700 (all 24dB) and settled on 600. I don't hear any cancelation. Rather the woofers add that woomp to the voices that makes Johnny Cash sound like Johnny Cash. It also provides that huskiness to Natalie Merchant and warmth to Norah Jones that makes them special. On operatic music, I hear the voices thro ...
is the passive between woofs & midranges disconnected, or still in the circuit? when i discussed going active w/brian for these speakers, he recommended disconnecting the passive x-over...
doug s.
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It's disconnected. Take the megawoofer out and the stuffing and you can see the coil. You just have to desolder one wire and resolder bypassing the coil. If you don't, the active crossover just won't kick in as it parellels the passive x-over.