| To Biamp or not to Biamp, that is the question??????? - Click HERE for Original Thread |
| Apogee |
Hello all,
Advice needed...
I'm about to start building my Alephs (possibly XA's but haven't decided yet). This weekend, I was thinking through the design and the idea came about to build a pair of stereo amps rather than a pair of large monoblocks... Essentially instead of a pair of 1.2's, I'm considering a pair of stereo 2's...
Yes, the heat - but I believe I've got that handled... Water-cooled is the current direction...
So my question is which is the better solution sonically? Biamp using a very high quality active crossover or a pair of large monoblocks biwired to the speakers???? I've always figured that eliminating the passive crossover components in the speakers would be a good idea but so far the electronic crossovers that I've heard have a far worse signature... I've tried most of the crossovers that are available and have currently settled on a pair of Bryston 10B L/R's as the best option that I have found from a sonic standpoint... They are fully discrete, balanced and 24 db/octave using very high quality components. Unfortunately, I can still hear them so I keep going back to the no active crossover option... The next attempt is to try high quality passive components between the amp and the preamp matched to the input impedance of the amp...
System presently consists of Apogee Studio Grands, Threshold Ta-300 (converted to a SA 3.9), Melos SHA Gold preamp, Pioneer DVL-91 Laserdisc player as CD transport and California Audio Labs Alpha 24/96 tube DAC, and lastly Goertz MI2 speaker wire and with home made interconnects using Canary star-quad wire.
Yes Nelson, I would love to try one of your new crossovers but it will take a while... :)
So, if you were considering building a new pair of monoblocks and the cost of implementing them as a pair if stereo amps vs. monoblocks wasn't the primary issue, what would you do????
Lastly, the Apogee's resolve to an extent that I can easily hear an interconnect change so please keep this in mind when thinking of adding another component to the signal chain...
Thoughts????
Thanks very much!
Steve
PS - Just so you also know the upgrade plan - amps first, preamp (Aleph P or X), new TT with Pearl or Ono, then new CD player and/or DAC... |
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| Peter Daniel |
I think that biamping is a better way to go. That's what I'm doing in my system. I'm using an active crossover at 100 Hz for subwoofers (from Threshold). I would never use active crossover for mids. In my setup I have open baffle Triangle midranges and they roll-off naturaly around 120Hz, 6dB/octave. So for quite a long time I was not using any crossover for midrange drivers. Just recently I placed 0.022uF cap in series with the input of my amp and I think that the sound is slightly better, it feels like midrange breathes more easily.
The active crossover in the mids/highs section will always have its signature so it's better to be avoided. My system has such resolution that I can easily hear the reversing of the cables, not to mention taking top covers off. That's why I also don't use a preamp.
I would build 2 stereo amps and tried to build active crossovers around front stage of the amps. One channel would be for subs, the other for mids and highs. |
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| Nelson Pass |
For guys like us, biamping is the minimum.
All the other usual arguments aside,
I like ultra-efficient drivers, and you can realistically
get 98-105 dB from upper bass all the way to 50 KHz
without much effort, but the woofer, even with a 100 dB
rating, will not deliver until higher frequencies. If you
want to play this way, you must biamp to mate the
bass with the rest of it.
Of course, I am currently quint-amping :) |
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| audionut |
Harry...
What making the "active crossover" out of passive components such as inductors resistor's and capacitors. This is what I have done, and I think sounds pretty good.
Also, any ideas on how you would build the filter into the front end of an Aleph 3 amp.
Thanx |
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| Peter Daniel |
In the following thread http://www.diyaudio.com/forums/show...98&pagenumber=2 is the schemtic of my current crossover. As you see ea. filter consists of caps and resistors at the input and feedback of ea. discreet op amp. If you are going to use your Alephs permanently as low pass and high pass amps you could probably build those type of filters around the input differencials. Maybe Mr. Pass could share some opinions?
I am minimalist kind of builder but in that case I might even go into tri-amping.;) |
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| Nelson Pass |
My experience from doing tons of these is partly distilled
into the xvr1 manual, but here are a couple of salient
point:
1) You will have to fool around with every value of the
filter parts to get what you want. This takes a lot of time
and taste, and often you end up very far from where you
started.
2) Driver makers often have a very different taste and agenda
than you do, so don't take their recommendations too seriously.
3) Same for textbook crossover designs.
4) A lot of the time you can use single pole (6 dB/oct) for
all the drivers except the woofers. There you will often
find yourself with 12 or 18 dB/oct.
5) I have never ended up using 24 dB/oct or higher slopes.
Just never liked the sound, don't know why. |
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| Apogee |
Thanks Nelson, we were typing at the same time...
Thanks to all for their comments thus far... Please keep them coming!
I wanted to clarify how the amps would be used...
My Apogees have a tweeter/midrange and a bass ribbon. You can see them here if you're interested...
http://208.51.252.167/studiogrand.htm
The passive crossover from tweet/mid to woofer panel is at ~ 1K starting at 6db and progressing to 12db. What I was considering is using one channel from each of the proposed chassis for the tweet/mid and one channel for the woofer panel - both wired directly to the ribbons... I will then use another crossover point and amp to drive the subs... 3 channels per speaker (tri-amped)...
The line of thinking was that perhaps it would sound better if I bypassed the passive crossovers and drove the ribbons directly with a dedicated channel for each... My assumption being that there would be a benefit because the drivers wouldn't be interacting with each other electrically...
Yes, I realize that this is a lot of power for the tweeter ribbons. I simply wanted to make certain that I had plenty of power for the woofers while at the same time having the same sonic signature from the amps between the tweet/mid and the woofer panels...
So, the dilemma is what is the best solution at this 1 k crossover point since it's smack in the midrange??? Do I just build a pair of monoblocks and biwire or do I attempt to build/find a really really good active crossover????? Which is better in these freqs since I really have no choice - active or passive???
Thoughts....
Thanks,
Steve |
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| GRollins |
I don't know that a vote is the best way to resolve this, but at any rate, I say: biamp.
As folks are no doubt tired of hearing, I'm in a gradual process of rehabilitating my system after years of being mothballed. All well and good, but I also try to have music along the way, even if it's not quite the quality that I'm aiming for in the long run. My first step in the process was to bring out the Magneplanars and put a single amp (Threshold S-500) on them.
Yuk!
I know there are people who claim that you can't remember sound (in which case, how do they recognize their mother's voice, but I digress...), but I <i>knew</i> my system had sounded better than that previously. Lots better. So I scrambled madly for parts and slapped together a crude active crossover. Presto! Serious steps forward in sound quality. Not up to what my system had been capable of in its prime, but a fantastic leap forward.
I've made it up to quad amp territory, now. I still lag behind the glory days in some ways, but have finally managed to exceed the old benchmarks in others. Progress is painfully slow, but I'm getting further along.
It's difficult to beat a simple follower with a cap for simplicity and clean sound.
Don't use opamps; many commercial crossovers do, with predictable effects on the sound quality. Discrete is the only way to go.
Grey |
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| roddyama |
I've been tri-ampping off and on for years depending on the number of working amplifiers on hand. I can't say I have the "golden ears" I may have once had before I worked in the bottling plant of the Stroh Brewery, but I can hear the improvement from a single amp to bi-amp to tri-amp. The improvment comes in all aspects of the sound. The 3 areas that are the most dramatic are the detail, and the depth, but most of all dynamics. Somehow, when you direct couple the driver to the amp, all the compression vanishes.
Rodd Yamashita |
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| macka |
Steve,
Sorry I'm a bit slow to pick up on this thread.
I've done a fair bit with active crossovers, both in pro sound and hi fi and I think is more about an evolution of your system rather than a revolution (active crossovers).
So here's my vote:
1. Your situation is interesting but I am curious about the 3 ohm load, this will need hefty amounts of class A bias for the benefits of Class A to be fully realised?
Perhaps Mr Pass and offer you advice on this matter.
2. Its probably fair to say that your 1.0K crossover is of good quality given the resolution your are getting and would be quite senstive any any amplitude variations with other crossover types (in other words if it ain't broke, don't fix it).
So to replace this with an active device would be subjectively quite difficult to improve on over the passive crossover.
(assuming you use Class A power)
3. I expect if you used a big enough Aleph then an active crossover for the 1K crossover would be not justified and there would be little gain from load sharing as 80% of the power is being taken by the mid/bass panel and being Class A, there can't be much harmonic distortion reaching the tweeter ribbons.
4. As to the sub crossover , this can be an absolute jungle and a bastard to get right.
A minimalise approach to the hi pass filter for the bass/mid panels will fair better than any active filter for purist taste.
Assuming you have a reasonable low drive impediance from your pre amp, just use a nice series capacitor/shunt resistor network for 6 db slope here and the panels will continue to roll of naturally being bi polar.
5. An A/B amp with plenty oh headroom for the subs should suffice and you can then tinker with the low pass network for best integration with the panels.
In a nut shell, built your Aleph 1st, then see what happens, you'll be surprised at the improvement.
PS Nelson has a great article on crossovers which you will find useful.
best regards
macka |
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| Peter Daniel |
| quote: | Originally posted by GRollins
I know there are people who claim that you can't remember sound (in which case, how do they recognize their mother's voice, but I digress...), but I <i>knew</i> my system had sounded better than that previously. Lots better.
Grey |
Those people might be right, might be not. I usually don't do A/B tests because they are boring and not consistant. However when everything is right in your system you just know it.
I've been playing that game for some time recently and that feeling (about right setup) comes and goes, depending on changes you do.
But when everything locks in place, even the bad recordings sound good, there is magic in the air, you discover every album again, each instrument and sound exists in its own 3-dimentional space and suddenly you realise that everything they write about in Stereophile is true. But what's important, you don't get tired listening and you feel good about the time you wasted to achieve it. Isn't DIY all about it?;)
It's kind a like adjusting VTA. Usually, there is only one "perfect" position. I decide it to right about it, because just today I achieved that bloody state,.... after a week of tweaking.:cool:;) |
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| Apogee |
Thanks all for the responses!
Ok - Biamping will be the direction so one more question if I may...
I have possibly found a source for some nice heatsinks so I may not have to go water cooled after all...
If I plan on total dissipation of 600w per chassis (one chassis per side with two channels per chassis) should I go for a lower output wattage with higher biasing or higher output wattage with the bias reduced a bit???
I'm thinking that I can either put a pair of Volksamp 60's with the bias turned up, or perhaps set the rail voltages for approximately 80 watts and use lower bias...
I know typically that things sound better with higher bias but I'm not sure how the two stage Aleph will handle the low impedance loads that the ribbons create (currently 3 ohms). I've only heard the Os and it wasn't through my speakers.
Is there a preference or performance gain either way when driving low impedance loads?
Thanks again for all of your opinions/comments!
Steve |
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| Nelson Pass |
High bias does a good job of curing the problems
driving low impedances. I think it will work fine. |
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| FullThrottleRic |
| quote: | | Of course, I am currently quint-amping :) |
:eek: :eek: :eek: :eek: :eek:
Is it just me?!
I'd really like to see some pics of NP's system :cool: |
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| GRollins |
If you're saying that the Apogees are 3 ohms, you're going to need to jack up the bias a bit or face current limiting. The Volksamp versions of the Aleph circuit had even lower bias than the equivalent Pass Labs models, so proportionately they will require even more boost on the current. Heat sinks will need to be larger in consequence.
Your circumstances aren't all that different from what I'm facing in biasing an Aleph-X for the Magneplanar ribbon tweeters (about 2.5 ohms). Although I posted the Aleph-X showing 15V rails, mine will be more along the lines of 12V, possibly even less, with the bias current about 50% higher. If I decide to go with an Aleph-X for the Bohlender-Graebener RD-75s (about 5.5 ohms), I won't have to go with such high bias, although the rails will need to be higher. All in good time...got other things on my plate at the moment.
As for pictures of Nelson's system, I imagine that they would need a time stamp, as the pictures would be obsolete within a few weeks.
Grey |
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| PedroPO |
Hey Guys!
Need some help pls.
I have two amps, one SOZ and one Audio Note Kit One.
I am tring to biamp using SOZ for the low frequencies and the AN for the High ones.
I connect the amps with separate wires to the terminal of the speakers (infinity delta 50) and use the speaker crossover.
From what understand you build your own crossovers. Are the ones in your speakers not good enough for you or you speakers do not have separate inputs (or do you build your own speakers and crosovers? ;-)
Another issue is how to calibrate both amps to deliver the same "amount" of sound.
I use my ear, but can't we use a microphone, a sinusoidal constant sound and a voltmeter to find the correct adjustment?
Thanks,
Pedro Oliveira |
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| Peter Daniel |
The whole idea of biamping is to use crossover before the amps. That way ea. amp is working in it own frequency range. The system is far less subject to intermodulation distortion effects and you can achive increase in dynamic range which is about twice that of conventional passive system. Additional, there is direct and intimate coupling between the amplifier and the loudspeaker driver that is not possible with a passive system. This allows control of the loudspeaker driver by the full damping factor avalable from the amplifier.
I always use test disc and a mike/meter to adjust the system. |
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| GRollins |
Why not try the SOZ for the high frequencies and the Audio Note for the low frequencies?
Grey |
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| Bill Fitzpatrick |
Lest anyone forget.
You can't have a 1st order slope on a satellite speaker, for example, if the crossover frequency is meant to be somewhere around the F3 of the satellite. The low frequency roll-off of the satellite has its own order - 2nd order for sealed and 4th order for vented. Adding a 1st order transfer function simply results in a 3rd or 5th order.
Even if the crossover frequency is 2 x F3 of the satellite, it still won't happen.
All this talk of first order crossovers in a bi-amping situation needs to be squelched.
In my experience, the best thing to do with a sealed satellite is to use a 2nd order high pass filter whose F3 matches the F3 of the satellite. Then use a 4th order low pass for the woofer where F3 is -6db. You wind up with the classical LR filter. |
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| PedroPO |
| quote: | Originally posted by HPotter
The whole idea of biamping is to use crossover before the amps. |
Thanks, do you remove the speaker crossover and connect the amp directly to the driver?
PedroPO |
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| PedroPO |
| quote: | Originally posted by GRollins
Why not try the SOZ for the high frequencies and the Audio Note for the low frequencies?
Grey |
Well, I believe that the Audio Note is better (very indeed) than the SOZ in the midrange and High frequencies, and the SOZ is much better in the low frequencies.
I think that valve amps are not very good in bass, but are great in midrange.
PedroPO |
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| roddyama |
Hi Bill,
| quote: | | You can't have a 1st order slope on a satellite speaker,... |
With all due respect, I would have to disagree with this statement. I have found, after years of listening to my system, that a 1st order high pass rolloff works the best for me. I have dual JBL LE10A's in a sealed box for the mid-bass. They have an f3 in the box of about 65Hz and I have an active 1st order high pass filter at 100Hz. The active lowpass for the subs rolloff at 18db/octave at 80Hz. This arrangment works great.
| quote: | | Even if the crossover frequency is 2 x F3 of the satellite, it still won't happen. |
I'm don't think I understand this statement. What is it that "...won't happen"?
Rodd Yamashita |
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| Peter Daniel |
Pedro,
You disconnect speaker's crossover and connect amps directly to the drivers. Then you use active or passive filters before the amps (but not the ones you removed from loudspeakers, of course);) |
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| Nelson Pass |
As soon as I can get my kids to clean their stuff off the
floor, I'll take a picture.
Probably some time next year. :) |
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| Nickolas K. |
Steve,
I thing an Apogee loudspeaker is the worst thing for a power amplifier.
I remember when i bought my Divas in 1990 i was using a pair of Rowland Model 7's. What a wonderful sound for the first 30 minutes! After that the amps collapsed. There was nothing wrong with them. They just couldn't drive the Divas at full power in a 70sqm living room.
So i sold the Rowlands and built 4 monoblocks based on the design of the ML2 but with a healthy 120W@8ohm and capable of driving <1ohm (each amp has a 3KVA transformer, 20x10kuf Sprague 36DE electrolytics, Semikron SKKD 46/08 semipacks, 16 pairs of MJ15003-MJ15004 and weighs about 70 Kgrs). The results in passive biamp mode were beyond imagination. I don't know about the sound of Grands or Studio Grands but i think the Divas are among the best full range bipolars ever made.
In 1995 i bought my first video projector and then i realized i needed subwoofers to avoid tearing apart the bass ribbons of the Divas.
I started listening to various high-end active subs of the 15-18-inch variety but the results were disappointing when listening to music.
I decided to build my own. After a brief search i bought a pair of JBL 2235 soft suspension 15-inch drivers. I use them in 100lt vented enclosures tuned at 30Hz and the balance between LF power and transient attack sounds perfect.
I built one more pair of amps (the same 70 kgrs beasts) to drive them and an active crossover with tubes (active 18db/oct for the low pass and passive 6db/oct for the high pass). It has 2 Alps Black Beauty pots for continuous frequency setting of both filters and a Sfernice metal film pot for LF level attenuation (the JBL's are at least 10db more sensitive than the Divas).
The sound of the combination has to be heard to be believed.
Everything is there in full glory, cannon shots in Verdi's Othello, organ pedals in Saint Saens' organ symphony, contrabasses in Dvorak's 8th symphony, Donner's thunder in Wagner's Rheingold etc.
I think you should do the same with the Studio Grands.
Use a good 2-way active crossover and drive the woofers with a separate pair of amps. For the ribbons go for passive biamping.
Good luck.
Nick |
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| Bill Fitzpatrick |
| quote: | Originally posted by roddyama
Hi Bill,
With all due respect, I would have to disagree with this statement. I have found, after years of listening to my system, that a 1st order high pass rolloff works the best for me. I have dual JBL LE10A's in a sealed box for the mid-bass. They have an f3 in the box of about 65Hz and I have an active 1st order high pass filter at 100Hz. The active lowpass for the subs rolloff at 18db/octave at 80Hz. This arrangment works great.
I'm don't think I understand this statement. What is it that "...won't happen"?
Rodd Yamashita |
You may have ADDED a 1st order, 100Hz high pass filter to your LE10 but the fact remains that somewhere around 65Hz the system is starting to roll off the low frequencies at a rate of 18db/o.
You may be satisfied with what you have but I'll bet if you did it right you would even be happier.
By "it still won't happen", I mean that it won't be right. |
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| Peter Daniel |
| quote: | Originally posted by Bill Fitzpatrick
You may have ADDED a 1st order, 100Hz high pass filter to your LE10 but the fact remains that somewhere around 65Hz the system is starting to roll off the low frequencies at a rate of 18db/o.
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Disregarding the speakers, the amp is probably quite happy without all those low frequencies to amplify.;) |
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| Bill Fitzpatrick |
Exactly. That is why an electronic crossover providing a 2nd order high pass at the sealed satellites F3 and a 4th order lowpass at the same frequency is such a good deal.
The same summed response of a LR 4th order network is now happening acoustically. I don't know what else anyone could ask for. It baffles me that this whole question has not previously been laid to rest. From a theoretical standpoint this is pretty much of a no brainer. The hard part is when someone pipes up and speaks on the evils of op-amps. To this I say, "do it discretely" if you wish.
Bury this debate and move on. |
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| roddyama |
Hi Bill,
I believe you're taking a rather idealistic view of this issue.
That is to say it is certainly possible to achive a true 4th order LR high pass roll off by summing the response of the active filter and freq response of the driver(s) in the bass region, if you have control over most of the system parameters. That is what a good product engineer might shoot for in designing a sat/sub type system. But the average DIY'er usually has to live with what they have to work with. Even if you start from the point of driver selection and crafting your own boxes, there's no guarantee your going achive the perfect B2 alignment or Qt of .707 or .5 or what ever the original goal may have been. Chances are very good that the results will be different then the original goal if your goal was a mathematical ideal.
There are other, practical factors that must be considered as a DIY'er. Factor like what are your available active xover frequencies? You might not get within 15% of your satelites f3. What are the available filter alignments? How good of a woodworker are you? How far are the finished sats from the original concept? That is just scratching the surface of the number of obsticles an average DIY'er will face on just this issue, not to mention the other 1001 other issue they'll have to contend with. But therein lies the beauty of being a DIY'er
I've been working the same tri-amp system for 25 years. There are only a few components left from my original system. But I've had a Heathkit electronic xover from the start. It allows me selectable xover frequencies and slopes from 1st to 3rd order in the high and lowpass sections. Through 4 different livingrooms, 2 different sub drivers, and 3 different mid-bass configurations, the system always sounded the best with a 1st order highpass and a 3rd order lowpass with a sligh gap in their xover frequencies.
I currently use a Bryston 4BST for the LE10A's. I would rather try to optimize the mid-bass speakers transient response then worry about a little (very little) IM distortion in a mid-bass amp like the Bryston.
There is no single "best way", particularly in the DIY realm. The debate is half the fun.
To keep from being to far off topic, I'm building an Aleph 3/5 for my horns above 1200Hz. I should probably build a Zen, but it hurts to think about the electric bills.
Rodd Yamashita |
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| Bill Fitzpatrick |
But real DIYers DO have control over the system parameters and they don't need to work with what they have. What they ought to do is get what they need. I assume that were not talking here about someone trying to get a system together with a mid range they picked up at a flea market.
As far as the low frequency driver in a SEALED satellite system is concerned all you have do is pick a driver (plenty of recommendations over in the speaker forum), stick it in a box that gives you a Q of .7, find the resonance peak and there you have F3 within 2%. You don't overly rely on published parameters because they vary. You run your own impedance curve and derive the values. OK, so that part's nailed down and it's very, very simple.
Can't run an impedance curve because you lack the equipment? Not to worry, the money you can save by building your own electonic crossover will more than pay for a AC Millivolt meter and audio oscillator which are plentiful on ebay.
And, because this entire forum is DIY based, you hunker down and build your own crossover. A single op-amp, a few caps and resistors (power supply taken for granted) makes a 2nd order high pass filter. Two more op amps, more resistors and caps and you have a 4th order low pass filter. You don't need a multi-section pot to vary the frequency because the frequency is already selected. We're talking $35 worth of parts here. And you don't have to even run a curve because the formulas are very accurate. Add a buffer or two and some way to vary the low freqency output. Construct this on a perf board or a PC board and there you have it. Like I say, it's a no brainer.
To get this far you don't need to be a good woodworker, the room is not an issue and the woofer is not an issue.
I disagree about the debate being half the fun. It's a waste of time. The pleasure comes from doing it right, saving a ton of money and listening to the results.
As to your system. With the info you provided it's clear you have not actually tried my recommendation. |
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| roddyama |
I work for a German company, so I'm very familiar with the opinion that there is only one solution to a given problem and only a single ridgid path to that solution. I don't agree with it, but I do agree with the right to be of that opinion. Although, it does take the fun out of the debate.
Rodd Yamashita |
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| promitheus |
I think the best way is biamping but only with active crossover. You have a lot of playing room and it doesnt cost nothing to swap resistors in and out. To do that with a passive crossover you need a fortune.
Plus its very hard to change Q or phase with passives.
I want to work up slowly to making an Aleph3 for my tweeters after finishing my Aleph5 but to do so I need an active crossover. I really want to see the passdiy crossover but its taking so long.
sigh.......
Maybe someone knows when its coming out......? |
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| PedroPO |
Light my path pls..
Do you guys buy or build your crossovers?
Active or Passive?
I'm trying to biamp, but the only thing I have is the 2 amps, preamp, speakers and source.
After reading this thread I FOUND that you shouldn't use the crossover in the speakers...(':D')
Guess we are allways learning..
Pedro Oliveira |
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| promitheus |
When you bi amp you can use also the crossovers in your speakers.
With biamping you can feed each speaker with its own crossover. That also works but I dont see the advantage of it if you dont use active crossovers before the amps. Of course in this case you donīt use the crossovers in the speakers. |
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| AudioFreak |
| Yes there are minor advantages in bi wiring but bi (or more) amping provides huge advantages if done correctly. |
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| PedroPO |
AudioFreak & promitheus:
Can you be more specific?
What do you use in your system?
Don't be shy to tell me... ;-)
Pedro Oliveira |
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| macka |
Rod and Bill,
I understand exactly where you are coming from with respect to diy crossovers and parameters.
In the commercial version of my system, a now obsolete JBL Pro monitor 2245, the crossover can be rigged for either active or passive operation from the 1st crossover point of 280 herts.
Prior to obtaining the JBL schematic for the crsoover I spent an eternity scewing arround trying to optimise the woofer/mid crossover for 2nd order passive operation until I realised my values were way out by 40 % because I was not aware of the effect of various interactions with the drivers and crossover values.
The point is active operation makes this easier.
I also had to re tune the boxes also to vented 9 cu ft with JBL the 2245 18" woofers tuned to 28hz for an F3 of 32 Hzwith a total Qts' of about 0.285, which takes into account the box losses and DCR of the crossover chokes which are about 5.4mh.
I would like to see a decent active crossover (ie J fet design) but until then I 'm sticking with the passive.
Since this pic I have replaced the mid cone with a JBL 2212 10 Mid driver which weighs 15 lb.
regards
macka |
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| Apogee |
Just wanted to thank everyone who took the time to help answer my questions!!!!
You've given me enough feedback/information that I'm going to take the biamp plunge...
Thanks again, |
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| roddyama |
Steve, Pedro,
Since you're both new to the multi-amp system scene, here a suggestion for you to think about.
You can routinely find Rane electronic xovers on eBay. If you stick with the Rane AC22 (2way stereo) or AC23 (3way stereo), you can win the bidding anywhere from $100 to $200 depending on condition, etc. The Rane xover has a wealth of adjustments. It has adjustments for separate hi and lo xover points, slopes, and level. It even has an adjustable time delay for fixing speaker offsets.
You can pick one up and setup your system and then decide whether you want to build one from a kit, or from scratch, or wait for Mr. Pass' new xover. You might decide to go back to a passive. Whatever you decide, when your done with the Rane, you sell it on eBay (maybe for a profit), or you can keep it for your next project. There was even an article in the Audio Xpress on how to spruce up the sound of an AC22 to us in you main system.
Whatever you decide to do, enjoy
Rodd Yamashita |
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| PedroPO |
Rodd Yamashita:
Thanks!
This is the thing I like in this forums.
Everybody needs help and heverybody helps!
':D'
Pedro Oliveira |
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| GRollins |
For what it's worth, I started an active crossover thread (yes, using JFETs...2N5457s, but no reason you couldn't use something else, including bipolars or MOSFETs) in the Everything Else forum a while back. There's more to do, but there's enough there to start someone who's thinking in that direction.
I'll get more posted in there one of these years...
Grey |
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| timo |
Rodd.
Can you tell us which issue of Audio Xpress had the article on the Rane AC22?
This is exactly what I have and I would be very interested in more information on improving it's performance.
For general info to those who might persue this x-over, the AC22
is a stereo, 2 way unit and comes with the delay feature wired for the LOW channels but it can be converted to the HIGH channels. I suspect most of us on this thread would be using it that way instead of how it comes from the factory.
There are clear instructions in the manual on how to do the delay conversion.
Thanks, Timo |
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| Peter Daniel |
| quote: | Originally posted by macka
I would like to see a decent active crossover (ie J fet design) but until then I 'm sticking with the passive.
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If you are looking for a good active crossover why not try this one: http://www.diyaudio.com/forums/show...98&pagenumber=2
It comes from Nelson Pass and, if not considering elaborate adjustments and variety of presettings, the whole idea is pretty close to his current model. You could prabably still improve it by changing semiconductors for better ones. I can only assume that it beats in all aspects. |
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| Nelson Pass |
The nice thing about the PCX was that all the resistors
were the same value, so you could pop in those 8
resistor chips (Digikey) into a socket and get a clean
18 dB/oct filter.
It got great reviews, particularly from Dick Olsher in
Stereophile.
The gain stages worked fine, as they only had a 6 dB
gain figure, and you can easily sub them with (ugh)
op amps. |
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| Bill Fitzpatrick |
A lot of people don't seem to like op-amps.
I was wondering if anyone would object to an op-amp in the low pass section and discretes in the high pass. |
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| roddyama |
Hi Timo,
I had to go to the non-active reading section of my porcelain library, but I found it. It is the December 2001 edition.
Mr. Pass, Bill,
I remember a preamp from the 70's, the Apt preamp by Thomas Holman. It was op-amps through-and-through. I know the switches and pots could have been better quality, but the sound was one of the most neutral sounding preamps around at the time. The price was right as well.
Just a thought.
Rodd Yamashita |
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| Nelson Pass |
I seem to recall that the Apt was a discreet, if not
particularly remarkable, circuit. Probably Holman's
best work.
I don't want to get off on a rant here but
I'll tell you what I don't like about op amps:
1) Huge open loop gain figures that I don't need at all
2) Marginal stability at low gain figures
3) Not designed for audio, no matter what they say
4) This is DIY. I view op amps the same way I look
at a can of soup or a fast-food burger
5) You can actually build your own op amps pretty
easily, and often more cheaply
:p |
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| mlloyd1 |
I have the APT owner's manual - complete with detailed schematic (nobody does THAT anymore!). Alas, it's at home so I'll post more tonight.
It used op amps (TL07x) which were good for their day. The RIAA stage was discrete. Also used a emitter follower with current sink load as a buffer for the volume control. The volume control was a feedback design that had low input impedance. TL07x are notorious for not liking to drive even moderately low impedance loads.
I actually duplicated some of the circuitry for my earlier preamps. Worked quite well and sounded very nice, especially with better performing parts.
Some of the audio magazines and electronics trade journals of the day had some great articles about the design Holman gear. Some things were very usual - I can't recall seeing any other amp that used the Baker Clamps approach to keep the voltage gain transistors from saturating (to keep the rails from sticking - a big problem with some of the "high slew rate" designs from that time period).
| quote: | Originally posted by roddyama
Hi Timo,
I had to go to the non-active reading section of my porcelain library, but I found it. It is the December 2001 edition.
Mr. Pass, Bill,
I remember a preamp from the 70's, the Apt preamp by Thomas Holman. It was op-amps through-and-through. I know the switches and pots could have been better quality, but the sound was one of the most neutral sounding preamps around at the time. The price was right as well.
Just a thought.
Rodd Yamashita |
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| JensRasmussen |
:) well I believe that is the right way to go if U have a 4 way system.
I use a 3 way active cross over and therefore 6 amps
At the moment I'm making a new subwoofer amp. Just ordered heatsinks for them. 7 kg each !! :D
________________
Power to the people ! |
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| Nelson Pass |
Apt was around for quite a while after Holman split, and
in fact one of my ex sales manglers went to work for them.
I can't help but think the TL074's were a later innovation.
Also, I meant the circuit was discrete, and who knows if
it was discreet. :)
BTW, I always rather liked the TL074 and its brothers.
For op amps they were remarkably simple and had nice
FET inputs driving a single ended bipolar and complementary
followers. And they sounded pretty decent. |
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| roddyama |
I had to have a relay replaced in my Apt preamp in '87 and I know that Holman went to Advent sometime in the early 80's; so there was a time that Apt Corp. continued on without Holman.
The op-amp he used most was the TL072CP. "Through-and-through" might have been a bit strong. This op-amp is used on all the inputs except in the phono circuit. It is used as a buffer in most of the control circuits and output circuits.
The point being that even though a lot of people don't care for op-amps, it appears that, done right, they can sound very good.
Rodd Yamashita |
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| Brett |
| quote: | Originally posted by Bill Fitzpatrick
A lot of people don't seem to like op-amps.
I was wondering if anyone would object to an op-amp in the low pass section and discretes in the high pass. |
Bill,
Thats basically what I have designed for my system. It's 4 way, triamped crossed at 120, 500, 6500(passive) with tube amps for the top two and SS on the bottom. I chose opamps because I found they're hard to detect there and because I need to EQ the bottom of the horns flat. Easier and cheaper with ops. If I'm bored next year I might re-do it all discrete. I have tons of gain spare so it might be easiest to do a discrete buffer followed by a passive shaping network before the bass PA.
The 120 HPF and 500 are passive before the poweramps; 6dB is enough here as the horns start to roll off out of band quickly anyway.
Cheers |
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| macka |
On the subject of opamps,
A while ago in Audio Electronics there was a good series of articles on building a mixer using either various chips or discrete buffers/gain stages using a Borbley fet/bjt circuit. (1995)
The article refers to various performance aspects of chips and sights noise and offset voltage/current important in some applications pending what you are doing.
There is also the issue of drive current for chips and it is possible to extend class A operation by biasing the output stage with a simple current source or transistor.
The chips referred to were the TL072, Ne5532, OPA 604
From what I recall the fet/jfet types has low offsets (which maybe important in crossovers) but were some what noisier than the bi polar counterparts and the discrete opamps had the best of both worlds and sounded great.(Borbley)
The article also has excellent coverage of balanced operation, power supplies design and component selection.
If you are interested I could dig it out and arrange copies!
BTW Borbley has a couple of nice downloads in Jfet applications if you are interested in discrete opamps and has a crossover board and article for a preamp/crossover if you are interested.
best regards
macka
;) |
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| Brett |
| quote: | Originally posted by macka
If you are interested I could dig it out and arrange copies!
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Yes please. |
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| ergo |
Nelson, a quick question here.
At passdiy site under coming attractions is a project
"The High/Low Pass, the first word in electronic crossovers"
Can you please give us some peeks into this project :)
Especially
*When will you estimate (very roughly) it to be available?
*Is there going to be some sort of kit available (pcb etc)?
*******
I'm also planning to try biamping in the future. Your DIY project could form the basis...
Regards
Ergo |
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| Nelson Pass |
1) I don't know. I have a few other projects to complete
first, but it has a strong commitment because I love
multi-amplification, or at least I like selling more amps. ;)
2) There will at least be a pcb. |
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| nar |
| So that is why we like so much going to the local electronic store to buy some big power donuts he he he;) |
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| Nelson Pass |
| Out here the power donuts are Krispy Kremes. |
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| nar |
| Sorry Nelson can you explain the trick my english is not so good I'm afraid...!!!! |
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| GRollins |
Krispy Kreme makes what are (in my not-so-humble opinion) the best doughnuts in the world. Period.
Yes, I'm prejudiced. Not only are they more tasty than the law allows, but they got their start in North Carolina not far from where I was born. Even if I hadn't been eating the things at every opportunity since the day I was born, I'd still have to root for the home team.
For those who don't know what a doughnut is, it's a small O-shaped piece of fried bread coated with sugar. Anyone who tries to tell you that a doughnut is made like a small cake (e.g. Dunkin' Donuts and their ilk) covered with confectioner's sugar is seriously deluded. The only known cure for this malady is to get them to a Krispy Kreme and drop one in their mouth.
Religions have started over less...
www.krispykreme.com
Grey |
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| nar |
;) Thanks Gray that is clear now,but donuts are far from audio stuff...By donut I meant the BIG TOROIDS you can't eat without beeing sick...way too heavy!!!
These are the hearts of DIYaudio projects :p without 'em no power
regards |
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| GRollins |
Without Krispy Kreme doughnuts, the builders themselves run out of power...
Grey |
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| PedroPO |
Gray:
What is your favorite food that powers you in the big caps division?
Budweiser? |
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| Nelson Pass |
| Foster's has bigger cans ;) |
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| paulb |
I'll put Moosehead beer and Tim Horton's donuts against any other alcohol-sugary snack combination anytime. I haven't tasted Krispy Kremes but I hear they're having trouble making inroads into Canada. Tim Horton's are just too good.
Back on track: I've just figured out the schematic of the biamping crossover used in the Advent Powered Loudspeaker. Quad RC4136 op-amp, tons of passives, lots of gain padding in various places. I'm debating whether to replace the entire thing or possibly just update the opamp.
The circuitry is confusing enough that I'm going to measure the crossover frequencies.
If anyone has more info on these things (specifically crossover frequency and characteristics) I'd love to hear about it. |
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| GRollins |
Beer= Affligem Trippel in 750ml bottle (w/cork, naturally), or any number of barley wines.
Prior to the local religious zealots going on a rampage, you could get it here. Now, I have to import mine from Virginia, which is a long trip, indeed.
Paul,
Being a lunatic fringe kind of guy, I'd say go discrete, but opamps would be easier if the pinout is the same. Just keep an eye on whatever EQ they engineered into the thing.
Grey
P.S.: Moosehead? Egad, Paul, you and I are going to have to have a serious drinking session one of these days...even if we have to meet in Virginia to do it. Incidentally, Grimbergen makes a pretty good Trippel, too, and their Double ain't bad (for that matter, the Affligem Double is good, also). |
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| planet10 |
| quote: | Originally posted by paulb
Tim Horton's are just too good. |
Yuck -- we got Tim Horton's out here and i won't eat their donuts, Thrifty's are way better. As to beer -- i'm allergic.
The passive Advents XO at about 2.4k, and i believe the active ones were the same. If i were you i'd just start over, the amps in the Powered Advents have a great tendency to lose their smoke. When we were selling these new, they were breaking all the time. Each of the 2 pair we had broke more than once.
dave |
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| paulb |
Thanks, Dave, my calculations from the components gave me either 2.5K or 1K, so I'll assume the former.
I knew about the smoke problem, I'm yanking the amps and replacing them. If I find the right heatsinks, I think I can get 2 Class A channels in each.
Thrifty's? Isn't that a blue jeans store?
Grey: hope to take you up on that sometime. Except Nebraska would be more like halfway between us. |
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| planet10 |
| quote: | Originally posted by paulb
Thrifty's? Isn't that a blue jeans store? |
Yes that too. the Thriftys i speak of is a local chain of (very good) grocery stores -- includes Alex Campbell Premium meats -- imported from Alberta of course.
dave |
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| GRollins |
Paul,
Dunno what the laws are in Nebraska...hopefully not as restrictive as the ones here. It's a possibility. It'd be difficult to drag my system out there--you'll have to bring yours.
Have you considered discrete opamps on daughterboards as replacements for the native opamps?
Grey |
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