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Old 19th November 2007, 07:37 PM   #71
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Quote:
Originally posted by Variac
Nelson, don't you sometimes use a passive network before a power amp, and would that be one of the approaches here?
Yes, and maybe.

We have a pair of Orions (more specifically Wayne does) and
also a supply of SEAS drivers of all sorts. So we have the
materials at hand.

I have enough data to begin consolidating the circuits into a
more compact approximation of SL's circuitry, however it
chews up time, which is my most precious commodity. What I
think I'll do is to tackle it piece by piece.

The other temptation is simply to take the Orions and develop
a crossover set for it from scratch and see what I get.

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Old 19th November 2007, 08:45 PM   #72
Variac is offline Variac  United States
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Well, since you are the only one that seems to be tackling the issues means that you get to choose the issues that you tackle.

And the speed at which you do your tackling

Actually I'm in no hurry- I just think that this is interesting..
It is only my opinion, but I think it would be generally cool to tackle most (but not necessarily all) of the issues that Linkwitz did, just BECAUSE that's his approach and it helps answer the question as to how much better discrete opamps and amps would make it.. Leaving a few off is certainly kosher of course..since you are the tackler...
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Old 19th November 2007, 08:50 PM   #73
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Quote:
Originally posted by GRollins

Also, just out of curiosity, how many people out there actually own one of the Linkwitz designs? And of those, how many are seriously interested in modifying their speakers?

Grey

About a year an 1/2 ago, having designed the NaO speaker system and having been asked many times how the NaO compared to the Orion I took it upon myself to build a pair of Orion speakers based on the info presented on SL's site; i.e, the Orion challenge. However, my approach was to look at SL's posted transfer functions and then set about designing active circuits which emulated the resulting acoustic transfer functions directly, rather than in the piece-wise approach SL used. It was a simple matter to eliminated a number of the opamp stages (6 per channel) by combining and optimizing specific active blocks.
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Old 19th November 2007, 09:02 PM   #74
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Quote:
Originally posted by Variac


Leaving a few off is certainly kosher of course..since you are the tackler...


Whereas if the tackler were me, a different set of rules would apply...?

Grey
(who is chuckling at this turn of events)
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Old 19th November 2007, 09:03 PM   #75
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Default Op-amps for inductors

Am I correct in surmising that an op-amp must use considerable feedback to simulate an inductor? If so, you must have enough feedback at the highest frequency that the op-amp is expected to be effective. How much feedback is required: 10dB margin, 40dB margin? At what frequency: 2x the filter freq, 10x freq., higher?

The buffers clearly require less open loop gain.

This is one necessary starting point to define the specs required when you begin substituting discrete for IC op-amps.

Jeremy
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Old 19th November 2007, 09:05 PM   #76
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Quote:
Originally posted by john k...
About a year an 1/2 ago, having designed the NaO speaker system and having been asked many times how the NaO compared to the Orion I took it upon myself to build a pair of Orion speakers based on the info presented on SL's site; i.e, the Orion challenge. However, my approach was to look at SL's posted transfer functions and then set about designing active circuits which emulated the resulting acoustic transfer functions directly, rather than in the piece-wise approach SL used. It was a simple matter to eliminated a number of the opamp stages (6 per channel) by combining and optimizing specific active blocks.
You are teasing us twice:

First, you don't comment on the quality of the results, and
second, you hint at the possibility of saving us a lot of work.

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Old 19th November 2007, 09:17 PM   #77
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Since the block diagram is posted on the web site, it seems to be fair game to try to emulate the general functionality of the Linkwitz ASP. However, in order to build an "Orion," one must purchase the construction plans, with which one presumably gets the crossover frequencies, etc. for the ASP circuit. As a result, this project should never get specific enough to infringe on that information. Any filter component schematics ought only to give equations on how the R's and C's affect the blocks' function and not give actual values for R and C, although suggested ranges may be appropriate (i.e. Cmax = 10 uF, Rmin = 1k, etc.)

Just my 2cents.

Jeremy
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Old 19th November 2007, 09:28 PM   #78
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Quote:
Originally posted by kropf
However, in order to build an "Orion," one must purchase the construction plans, with which one presumably gets the crossover frequencies, etc. for the ASP circuit. As a result, this project should never get specific enough to infringe on that information. Any filter component schematics ought only to give equations on how the R's and C's affect the blocks' function and not give actual values for R and C, although suggested ranges may be appropriate (i.e. Cmax = 10 uF, Rmin = 1k, etc.)
Agreed, and a more specific effort should be preceded by a non-
ambiguous statment by SL. That said, those who have paid for
the information from SL would presumably be able to insert
the appropriate values.

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Old 19th November 2007, 10:27 PM   #79
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Sorry to teast but as the designer of a completive system I don't think it is rightly my position to post the modifications I made. There is some history here and I don't want to come off as implying that my mods are superior to the original. However I will say that loosing 6 active stages certainly didn't hurt.

Over time I did make some changes to make the system balance to make it more suitable to my taste. I added some warmth in the lower midrange because I though vocals lacked body. But that is not specifically associated to the ASP topology.

At the time I build the system the ASP block diagram and transfer function response posted on SL's site (or the version I have from SL's site) gave sufficient information in terms of the gain of each stage and filter corner frequencies of the HP/LP filters. There is some ambiguity for delays but with these are pretty easy to gleam form response measurements.

I also ultimately purchased the plans set/boards.

The Orion is certainly an excellent speaker but from its inception I have felt it was overly complex in its active circuits.
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Old 22nd November 2007, 08:07 AM   #80
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Quote:
Tosh wrote:
First off, the Orion system I heard about two years ago is the best loudspeaker I have ever heard. I listened for several hours with many of my own reference tracks and other difficult passages, sometimes at loud enough volumes for the woofers to hit their stops. The delicacy of the plentiful bass alone is something which must be experienced first hand. These were driven by six Hafler DH-220 (or 200?) amps, but I still think that the lack of ultimate clarity (or liquidity or darkness) behind the treble came from the op-amp maze.
At the time, I was using Hafler T1600 amps. If we bottomed out the woofers, I must have had the Adcom arc welder on them.

Quote:
These were not Orion+ which add an additional rear tweeter.
Now they're Orion++. Even better!

The Hafler amps have had their weaknesses exposed by another set of amps on loan from a friend. The system is significantly more free of distortion on peaks, flatter (a bit of midrange bloat is gone), and has more clarity. These problems (such as they were, for the "best loudspeaker [you] ever heard") would appear to be the Halfer's fault, not the ASP's. Still, if the ASP could be simplified, I would be game to try out a simpler design.

To Grey: Extolling the virtues of the soundstage of the LS3/5A while saying the Orions do nothing new with soundstage is like calling the soundstage of an FM broadcast the gold standard, while ignoring live concert hall performances. As remarkable and curious and enjoyable as the 3/5A is (which I have listened to extensively BTW, along with countless other speakers and even, gasp, live music once in a while!) it's not in the same universe as the Orion, and not just in terms of soundstage. Perhaps you need to get out and listen to an Orion?

The RFI-rejection input stage is an analog filter on the input to the next (opamp-based) shelving high pass. So there's nothing to be gained by dumping it. SL also parallels the feedback resistors with small caps so there's no gain for RFI.

For the sake of clarity, there are 21 opamps implementing the 25 blocks shown on the ASP diagram linked to earlier (or optionally 22 opamps and 26 blocks with the optional bass notch filter around U10A. The builder can configure this to deal with one room mode. I turned mine into a switchable BBC dip filter for listening to DG recordings.) The detail-oriented will notice that four of those blocks do not have opamp designators.

Nelson: It's hard for me to see what can be replaced or combined. The input RFI filter is passive, as are the 50HP1, 2HP1, and the -7.9db gain. I believe the four opamps comprising the delays for mid and tweeter must be implemented with two opamps each because of the delay magnitude and phase. (SL discusses this in the Phoenix design pages on his site -- I don't recall exactly the rationale for the splitting the delay between two opamps). I suppose the two (or optionally three) notch filters which use opamps as simulated inductors could be replaced by real inductors. The two +/- 2.5db gain stages are trick circuits for usability: they make each tick on a linear one turn pot correspond to 0.5db of gain. The other blocks are either necessary buffers, shelving filters, or 2nd order HP/LP filters. But heck, if you can realize the same transfer function with passive components in the feedback loop of a single opamp per driver, I'd give it a try!

I suppose JohnK could have gotten rid of six active stages by dumping the two +/- 2.5db adjustments, compressing the two delays from four to two opamps, and doing the notch filters passively. Perhaps he just dumped the 5k notch on the mids since this is way out of band for the driver anyways (crossover is around 1.5k).

- Eric
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