really provided sonic equivalence, all discrete designs would be gone in a heartbeat.
35 responses Add your response
phusis " Whether it makes sense or not is a matter decided by the ears, not theory, but of course: if what your ears tell you is in favor of a passive configuration - in a specific, singular component context, that is - then that’s what it is to you in that particular scenario." Yes but the comparison is not passive vs active w Class A discrete, but active Class A discrete vs digital + IC opamps. No doubt digital processing has the flexibility to provide complex transfer functions, frequency responses (and time delays) that no discrete component system could duplicate, but from a pure sonic purity perspective, they will never match that of discrete Class A designs, assuming you don't need the frequency response complexity. With the Voxativ and PAP bass drivers, their response is reasonably flat enough that just a simple 4rth order HP/LP XO will do, assuming the XO point is well chosen. Why are there very little discrete Class A XO products available today? They are expensive to build, large in size, and use components (ie the transistors) that are getting harder and harder to find, as well as expensive. A single matched pair JFet from Linear Systems now cost more than most IC opamps. The Toshiba parts are long out of production and only available from manufacturers (like Pass Labs) who horded these parts many years ago. But the fact that companies like Pass Labs, Bryston and Parasound still build their top of the line products with discrete components still attests to the sonic superiority of these designs. If a lower cost IC opamp |
@dhl93449 -- ... So that confirms that the active XO system has merit in principle, and the class A discrete designs in practice. Thanks for the follow-up, and good to learn that your active XO project has come through successfully. From my chair though it still goes with absolute conviction: less will do, even in excellent fashion. A pro digital cross-over from Xilica that friends of mine and I are using in our respective set-ups is a rock steady performer that has sonically lifted passive speaker systems (in theirs and others set-ups; my own speakers have been sans passive XO’s to begin with) into more transparent, tonally authentic and dynamic sounding dittos. Simply better in every perceivable aspect, period. I believe it’s an unfortunate, even dead wrong message to put there saying that only the über-best of the best active XO’s will do compared to passive iterations, especially compared to a limited range of digital XO alternatives and not least with reference to: ... it makes no sense to me to place an EQ/XO having IC opamps between a discrete component preamp and discrete component power amps. Whether it makes sense or not is a matter decided by the ears, not theory, but of course: if what your ears tell you is in favor of a passive configuration - in a specific, singular component context, that is - then that’s what it is to you in that particular scenario. Few have actually tested their own or to them well-known passive speakers as converted-into-active dittos, with the potential experience of actives coming predominantly from all-in-one packages that leave little insight to be exposed other than the choices made with those particular designs, rather than what merits conclusive or more fully formed statements into passive vs. actives. Active configurations hold great potential, also as a solution of separate components with all that entails into the free choice of amps, cables, DAC’s and digital XO’s at reasonable prices - somewhat cheaper even, despite the more amp channels needed, than a passive set-up. |
Well, I finally finished my discrete Class A XO project. I used my own design discrete op amps, based on an early Spectral design modified with Nelson Pass inspired JFet output stages (instead of MOSFET stages as originally used by Spectral). I am using 4rth order Linkwitz Riley filters for both HP and LP filters and the drivers integrate smoothly Took out the gyrators as I really did not need parametric EQ with the Voxative drivers (switched from the Horn). System is now sounding better than it's ever sounded. So that confirms that the active XO system has merit in principle, and the class A discrete designs in practice. |
phusis Its all a matter of degree. Whether an active XO system using IC op amps sounds better than a passive system with the best Mundorf or other high end caps, inductors, and resistors may be arguable. But it makes no sense to me to place an EQ/XO having IC opamps between a discrete component preamp and discrete component power amps. I actually tried that with a Phonic i7600 op-amp DSP between my Parasound JC2 and two JC1s when trying too chase down a frequency balance issue (and it was good for that), but the sound quality through that Phonic unit did not sound as clean and detailed and the system with a passive XO and the Phonic removed. I am probably in the camp leaning toward an active system, but will not compromise in using IC op amps vs discrete class A circuitry. Every time I have made a comparison of products with IC op amps vs discrete, discrete always wins hands down. I think both Nelson Pass and John Curl would agree with me (along with Bryston). So I am in the process of designing and building an all discrete 4rth order Linkwitz Riley LP/HP XO system for the PAP Horn1 speakers. It will also have discrete op-amp gyrators for a parametric EQ function. Expensive, time consuming, and rather large, but I think it will be worth it. |
I have successfully used the DriveRack dbx PA2 LMS (loudspeaker management system) with vintage gear and some modern speakers. It works quite well as an external xover for 2-way and 3-way speakers and is affordable. The only downside is that it requires some time and patience to setup and it looks like Pro gear (which it is) and not home audio gear. I mount it backwards in my audio rack and it's practically invisible. Audio Nirvana published a great article about restoring vintage Altec Lansing Model 14s and described how they used this box to overcome some fundamental design flaws of the 14s. I followed their recommendations and it works great. Here's a link: dbx DriveRack PA2: The Future of Audiophile Systems Although I don't find external EQ and xover to be necessary in most situations it has always improved the sound of whatever speakers/rooms I have used it. |
A second suggestion of the First Watt B4 (designed and built by Nelson Pass). The factory-built edition is no longer in production, and used examples rarely come up for sale, so be prepared to wait. A kit version is about to be made available, I believe. The B4 is a discrete design, no opamps, no ic’s. It listed for $1500, sold for about $1200. Really versatile: two channels of 1st/2nd/3rd/4th-order high and low-pass filters in 25Hz increments from 25Hz to 6375Hz, level controls for either the high-pass or the low-pass outputs, switchable. |
@dhl93449 Regarding the subject of active XOs, it is almost impossible to find one that is built without op amps. Bryston is the only company that comes to mind that produced HP and LP versions with discrete Class A circuitry, and I do not recall if these are still in current production. In any case they are not cheap, and if you need more than just a single XO point (two way system), the costs mount up fast. This stance is a quick way to discard active XO’s when in fact they could be beneficial to a passive solution - even with opamps and A/D to D/A conversion being introduced in the signal chain. What’s the bigger picture; do the comparison and forget for a while the drawbacks mentioned to hinder the fuller realization of an active XO, if they’d even be that relevant compared to the negatives of a passive config., and then see. My take with an XP-series Xilica XO is that it trumps excellent passive XO’s in the three set-ups I’ve heard so far - quite easily. The sound in all cases went from slightly diffuse/smeared and soft to more clear, refined, transparent and dynamic going from passive to active. |
Arguing about whether bridging is good or bad misses the point. Many base designs (such as those from Nelson Pass) are bridged inherently. They allow the use of lower power supply rail voltages and therefor reduce power consumption, particularly with Class A configurations. I don't think that a properly designed bridging configuration increases distortion any more than using fully balanced circuitry does. It is true that each amplifier that is bridged will see half the load impedance, and as such must be designed to drive that lower impedance. Regarding the subject of active XOs, it is almost impossible to find one that is built without op amps. Bryston is the only company that comes to mind that produced HP and LP versions with discrete Class A circuitry, and I do not recall if these are still in current production. In any case they are not cheap, and if you need more than just a single XO point (two way system), the costs mount up fast. For the poster who mentioned potential pitfalls of eliminating the factory passive XOs, almost all of these are removed by providing a dedicated amp/driver. Line levels are easy to match with gain controls on the amps, and most other impedance matching gymnastics are eliminated with a dedicated amp. The system is also much more efficient if the drivers have widely different sensitivities, because you do not have volume matching resistors wasting a lot of power. The passive components are a lot cheaper and you can use higher quality. For example, teflon film caps are almost impossible to get (or afford) as large values in a passive XO, but are affordable in an active design where they are a lot smaller in value. For more discussion on the advantages of dedicated amping, see Professor Linkwitz discussion on the matter. |
God idea. At best having to bridge an amp is poor planning. I think the best posts her on the subject of biamping are by mijostyn and avanti1960. If you are making your own speakers and want to approach the problem of a 2 or 3 way system that way there are certainly advantages. Bypassing the cross over network of a well designed speaker made by a reputable company is a mistake unless the speaker was designed for it. |
Look, George, this merry-go-round of ours leads nowhere, so let's just agree to disagree. |
Na, you already proved you can’t do that with this statement. Every one of us preferred the sound of the bridged configuration, with some describing the sound as now being "more hifi"The "can’t see the forest for the trees" was the technical aspect of what you know, and what happens to a stereo amp when it’s bridged, all you gain is watts EVERYTHING else takes a hit. Bridging makes what was maybe a good amp, almost a P.A. amp. |
@georgehifi -- Not in the least, still fact with Class-D's today.Sorry, Not in the least, still fact with bridged today.In general Bridged AmpsPros=It's always has been the same. You left out better slew rate in the 'pro' camp of bridging. In any case those "facts" offer a convenient way to make an all-encompassing statement saying bridged amps only offer more watts while taking a hit in the remaining areas. What has, truly, "always been the same" is that it depends; given a sufficiently "sound" amplifier design (those aren't difficult to come by) and a speaker load that isn't downright problematic or too low-impedance, bridging won't invite stability issues. Indeed: what's the relevance of the stated cons as they apply to actual sonics? Roughly 3x the power though gives you more headroom, ease and likely a lowering of perceived distortion, and if a better slew rate is anything to go by transient cleanness should see an uptick as well - all of which aren't too far removed from my listening impressions of bridged amp constellations. |
Not in the least, still fact with Class-D's today.Sorry, Not in the least, still fact with bridged today. In general Bridged Amps Pros=It's always has been the same. |
@georgehifi -- Some redundant info hereNot in the least, still fact with Class-D’s today. Class-D, you mean in bridged config. or stand-alone? My experience with Class-D is far from exhaustive, but what I’ve heard is noticeably different compared to a good Class-A design or even a ditto Class-A/B iteration. My as-is unwavering preference at least what concerns the central to upper mids on up is for this range to be handled by a Class-A design, but I find it less obvious from ~1kHz and down. Certainly I wouldn’t choose Class-A here for my active set-up, for a variety of reasons. @avanti1960 -- tread lightly when bypassing the crossovers of any quality loudspeaker. Oh, absolutely. It’s a potentially complicated process and steep learning curve, and I wouldn’t as much recommend this approach (i.e.: converting a passively filtered pair of quality speakers into actives) as a design that’s born sans passive cross-over to being with. This mostly boils down to DIY and the pro sector, with the latter having sometimes preset filter-options to implement. Either outset could be a challenge, but once you get a handle on the different filter aspects I’d wager the freedom of choice, on-the-fly filter settings changes and differentiated approach to amp topology (that’s possibly) as it applies to each driver - added to the bliss, as I see it, of avoiding a passive cross-over altogether - it becomes addictive and a rather obvious bye-bye to passive. |
tread lightly when bypassing the crossovers of any quality loudspeaker. they usually do a lot more than just filtering out low or high frequencies. the other highly critical functions may include: BSC baffle step compensation, reduces frequencies that are reflected off of the front baffle of the speaker. bypassing this can lead to more lower midrange energy and forwardness. Level matching. Voicing the relative level between the drivers. Bypassing this circuit will require re balancing the drivers. Crossover slope and phase. Bypassing this can lead to drivers out of phase and loss of imaging and coherence. altering the crossover frequencies can put drivers out of their comfort zone and lead to non linear response and higher distortion. Zoebel network. Bypassing this can alter the impedance and linearity of a driver. Notch filter. Bypassing this could lead to peaks and high distortion in the reponse of a given driver. |
@georgehifi -- In general Bridged AmpsPros= Some redundant info here, all of which is mentioned ad nauseam without either getting into specifics with regard to perceived impressions, nor putting the cons-info into perspective; what’s the relevance of claimed negative aspects for them to actually matter in-use, and would actual listening to bridged configurations ever be freed/independent from a preconceived, theory-laden approach? This is my main contention with "hifi:" what’s headroom is generally looked down at as being "overkill," and further relegated to the arena of PA as something more crude and less refined. In this case I can only say my impressions of listening to bridged amp constellations, cons be damned, have been positive - indeed favorable compared to their non-bridged state. The overall impression is, by and large, that of a more effortless, (a)live, open and refined presentation - qualities I for the life of me can only associate with what is intrinsically better. If the matter was solely about comparing impressions and others disagreed with me, I’d rest my case respecting the other party’s opinion. What gets to me is the "look at the spec’d cons, man - they speak for themselves"-gist, added to the conjecture that more watts are essentially about catering to the PA-segment. The only real negative of actual importance in my case would be that residual noise in bridged mode is amplified, and that matters with an active configuration of a 110dB sensitivity horn/driver combination. A lower gain setting would be necessitated here, but as is I’m perfectly happy with a 30 watts pure class A amplifier for this frequency region. What I would consider is buying a second Crown K2 for bridged mode with my horn subs (8 ohms) and/or EV bass section, but only because it would make what’s already very good even better - at any SPL. |
georgehifi In general Bridged AmpsYup, that’s my experience as well.I could never understand the appeal of bridged amps. If you need more power, I think the best thing to do is just buy a bigger amp. Bridging an amp is more of a "parlor trick" than a solution to anything. Of course there are always exceptions and everyone is welcome to their personal preference . |
@georgehifi -- Each and every one of us preferred the sound of the bridged configuration, with some describing the sound as now being "more hifi"This statement says it all. It says what? The people in attendance of said listening session, among them musicians, knows how to use the term "hifi" in its truer sense, and nothing about the statement excludes the traits you mention, on the contrary. A smoother, more refined top end could point to better transient response (i.e.: better slew rate), and a more lively and open sound is exactly that and could involve many other parameters; like more headroom, less restricted dynamic capabilities, better sound stage, etc. The traits in particular you do mention are very much a factor of the speakers as well, I should add, so it seems me you're bending the statement to have it suit your agenda. |
Sounds to me mostly like theoretically-based conjecture. Have you listened to bridged configurations to form an opinion this way?Yes, and if you search you’ll find all the info I’ve heard/measured and found on it. Like I said above , bridging amps makes what could be a good stereo amp, lean towards becoming a mono PA amp. As many parameters take a hit, not just the ones I’ve mentioned above. Each and every one of us preferred the sound of the bridged configuration, with some describing the sound as now being "more hifi"This statement says it all. A really good amp should sound big, tight and wash over you with dynamics and detail that don't sound like it's coming from any of the the speakers drivers, and have a sound stage you feel you can get up and walk into. |
jpahere, I hat to be a stick in the mud but B+W does a good job designing it's cross overs. In my experience you are going to wind up pulling out your hair trying to get the system to sound right. I think you are much better off with something like a 100watt/ch Class A amp, perhaps a lightly used Pass amp. Used JC 1's would also be a great choice and because the new JC1+ is out a lot of old JC1s should show up on the market soon. As a note to others considering this sort of approach dynamic speaker do not benefit much from bi amping and frequently wind up worse. You are much better off adding two subwoofers with both high and low pass filters. |
@georgehifi -- That’s because all you get is more wattage, everything else takes a hit, especially current drive into lower impedance’s and stability, distortions. It almost makes what was a good amp into a PA amp. Sounds to me mostly like theoretically-based conjecture. Have you listened to bridged configurations to form an opinion this way? At a friend’s place a few weeks ago I heard the latest bridged amp installment to come across my ears. My friend already had one Crown Studio Reference II in his set-up driving his main speakers, but then bought a second one for bridged duties. Once gain matching between the mains and subs had settled as well as some minor delay and PEQ tweaks, a bunch of us came over to listen (all of us were very familiar with the sound of his set-up with only one Ref. II). Each and every one of us preferred the sound of the bridged configuration, with some describing the sound as now being "more hifi" in the sense of it being even more refined and smooth in the top end, while being more open and lively overall. I agreed with this sentiment. My friend found that in bridged mode it (subjectively) didn’t sound as loud at elevated SPL’s, though clearly feeling the loudness on his body. There wasn’t necessarily anything "PA" about the sound with the two bridged Ref. II’s, but simply a more open, effortless, refined and lively presentation (sorry to reiterate) that accommodated every music musical genre we cared to throw at it. Which, btw., mirrors my impressions from the previous bridged amp constellations I’ve heard. |
Not my experience. Recently went all-active with my existing Xilica digital cross-over, and it’s a bliss.Each to his own, on that. To each their own, but bridging is seriously underrated in hifiThat’s because all you get is more wattage, everything else takes a hit, especially current drive into lower impedance’s and stability, distortions. It almost makes what was a good amp into a PA amp. |
Old thread - oh well, as poster @jaystereo said. @georgehifi -- Don’t go digital to me it only led to sterility no matter what I tried. And I lost the sound of my favorite dac for whatever rubbish dac is in the digital dsp/xovers ones. Not my experience. Recently went all-active with my existing Xilica digital cross-over, and it’s a bliss. Indeed, once clear what can be done with a quality digital cross-over (and the Xilica is that), even very early in the tuning process, there’s the strong sensation of not wanting to go back to a passive filter - like, ever. There are caveats, however; an amp channel is needed for every driver or drivers that are coupled in parallel, and in my case a 110dB sensitivity horn/driver combo can lead to a degree of background noise depending on the amp/filter used. Moreover, unless the filtering has been preset by the manufacturer (like Sanders Sound Systems) one will have to do this him- or herself, and to do this accurately measurements will have to be made, though only as a guideline; remember to let your ears be the final judge with every step taken, because measurements need to be interpreted in light of their specific implementation, and often what is measured isn’t the direct link to its audible "equivalent," so to speak. Although, audiophiles invest their time in many a thing when it comes to their stereo set-up, and I don’t see an active approach being an insurmountable task with care and attention to detail. Doing the filtering ahead of the amplification on the signal-side, and hereby letting each amp channel see its respective driver(s) directly without the interference of passive components, can have obvious advantages. To my ears passive filters invariably infuse some degree of softness or smear, whereas with a quality active configuration transient cleanness, clarity, resolution and dynamic prowess is enhanced. Actually I also find the overall presentation with active to be easier and smoother on the ear. Done right going active is the real and preferable deal, I’d say. Or what I would do with those speakers is to go horizontal Bi-amping with the apms you have as the B&W internal xovers are of very high quality and well sorted. I’ve tried bi-amping both horizontally and vertically, yet every time I’ve preferred bridged mode configuration with two identical amps, where possible (and where not I usually preferred vertical bi-amp config.). To each their own, but bridging is seriously underrated in hifi. |
jpahere Don’t go digital to me it only led to sterility no matter what I tried. And I lost the sound of my favorite dac for whatever rubbish dac is in the digital dsp/xovers ones. If you want the best analog domain xover that’s discrete and that doesn’t use opamps, get a Nelson Pass designed First Watt B4, probably have to find a used one Or what I would do with those speakers is to go horizontal Bi-amping with the apms you have as the B&W internal xovers are of very high quality and well sorted. Or with something like a nice Pass Labs Class-A XA30.5 (amp1) on the mids and highs and a cheap Class-D (amp2) on the bass https://www.av2day.com/wp-content/uploads/2014/05/biamp1.jpg Just put a $49 Schiit Sys passive on the input of louder amp to even out the gains, and drive all that from your preamp. Cheers George |
Unless you are bypassing the internal passive crossovers of the 804 you will not need an active crossover such as the Marchand. Typically there are two sets of binding posts on the back of the speakers that are strapped together for single amp use. One set goes to the internal high pass filter and the other set goes to the internal low pass filter. You biamp by separating the terminals from each other on the back and using two amplfiers that have the same gain or one of the amps will need to have variable output to control the gain. |
