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Old 8th September 2006, 10:42 AM   #21
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Daveis:

I reread my post and after thinking it sounds like from the tone I'm trying to insult you or to be a jerk. I'm not, I just get passionate when people dismiss ideas or technologies because they are either inexpensive or aren't what traditionally falls into the catagory of "audiophile". Don't take it the wrong way, I didn't post it to insult you.
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Old 8th September 2006, 11:22 AM   #22
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As a casual observer of this thread it appears that there are several different issues being all mixed together and considered all at once. It may not be an all or nothing situation here.

For example the original idea was digital, active, line level crossovers with multiple power amps driving individual drivers. Now for someone into T-amps and computers this might be a very reasonable approach but the guy sitting there surrounded by SET amps, well, I think not. He might go for tube based passive-with-gain line level crossovers and drivers with naturally smooth response that do not require notch filtering. He would tend to use acoustic measures to deal with any remaining response shaping. Now the guy with a huge SS amp might feel better with power level crossovers.

So the issues would seem to be.

- Line v.s. power level crossover.
- Active v.s. passive (passive could be line or power level).
- Digital v.s. analog
- Cheap v.s. golden ear.
- Electronic v.s. acoustic.

Combination approaches might well be the best approach. My personal bent would be toward a single class A amp ( preferably SE tube ) per channel driving a wide range with low order passive power level crossover on a helper tweeter. Line level crossover (would consider either passive or active) driving a seperate sub woofer or two using a non-switching amp. I would however have no real objection to a seperate tweeter amp using line level analog crossover.

mike
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Old 8th September 2006, 11:42 AM   #23
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Quote:
Originally posted by m0tion
...But you don't need super "audiophile" crossover components to do it and there is absolutely no argument to be made what-so-ever that passive crossovers are TECHNICALLY superior to active crossovers. You can argue all day long that they subjectively sound better, but don't make the mistake that active crossovers don't have measurable technical superiority if designed correctly. Just ask Siegfried Linkwitz...
When I refer to passive crossovers, I mean power level, I don't consider passive line level crossovers viable - See Linkwitz for many reasons.

I think a point often missed by many active crossover experimenters is that the comparison must be made apples to apples - the transfer functions should be the same for the active and passive crossovers for a comparison to be valid.

Simply dialing in an active LR4 at the desired frequency is only slightly more valid than using the textbook formula to design a passive crossover (the active xo won't be affected by the drivers' impedance changes making it "slightly more valid").

A competently designed passive crossover can sound about as good as a competently designed active crossover, at the expense of a system efficiency and (slight) loss of amp control over the drivers. However, some systems make passive crossovers impractical, such as Linkwitz' Orion.

An advantage of the active approach is fairly easy incorporation of notches, peaking and shelving equalization as well as phase correction. Rare is the accurate driver that does not need some or all of these.

Of course this all can be accomplished passively, at the cost of further power loss in the crossover. Better crossover designers can incorporate shelving types of EQ (such as baffle step compensation) into the basic crossover without increasing parts count. See Zaph's ZD5 project for an example (although the phase alignment in the tweeter section adds a few parts)

Don't forget that arriving at your passive crossover with $300 in parts will probably have many parts leftover. If you're a serial builder, like many here, fine, you'll probably end up using them in another project. I have a hard time with "carrying inventory" although I have built up quite a stock of crossover parts over the years.

For prototyping I now have several adjustable analog active crossover boards (MOX) that can be daisy chained to achieve a variety of slopes. I'm also building modular EQs in their prototyping area. Pretty much nothing will get thrown away in development.

On the hiss front, I've often seen it said that the Behringer and dBx boxes need to be run pretty much at full signal to maximize their S/N, and attenuated afterwards. The only way to do this and have each section track accurately is with a stepped attenuator on each output. This way you'll attenuate any hiss along with the signal. I haven't felt a compelling need to do this with my analog crossovers yet.
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Old 8th September 2006, 12:20 PM   #24
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Before we too fixated on the hiss issue, let me try and calibrate how loud the hiss is in my system and what I have done to improve the situation.

At first I had the dBx inut sitting right on top of my amps and the noise level was significant, audible at my listening position when no music was playing. Since then I have done the following :

1. Moved the dBx out away form the other equipment.
2. Improved the "internal" speaker wiring and connections.

Both of these changes reduced the noise level. The hiss right now is not audible at my listening position and is low when I get very close to the speaker drivers. The speakers are extremely efficient. By low I mean less than the background noise on an average record (remember black disks with grooves) and less than the noise I once heard in a high end dealer's show room when he was demoing Chello (spelling?) electronics and B&W speakers. I would say it is on the same level as most reasonably priced commercial SS amps or maybe just slightly above. It is definitely lower then what I have heard from some tube amps.

I consider this good enough, not a limiting problem. I have not heard any other weird buzzing or other noises. There are other bigger fish to fry in terms of making my system perform better.
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Old 8th September 2006, 01:44 PM   #25
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Quote:
Originally posted by m0tion
Daveis:

DCX2496 != a dozen cheap opamps. Thats a Behringer CX3400.

DCX2496 = about 2 cheap ADCs, 6 cheap DACS, and a cheap Sharc DSP.

I take it you've listened to the DCX2496 in stock or semi-modified form and think that all the opamps it uses after the DAC actually sound good? They dont.

Over the years, the the one common thread I've discovered is the fewer opamps in the signal path the better. The only exception I have ever had to that was an M3 headphone amp using OPA627.
That design, BTW, is quite nice.

Another thing I've heard consistently, is that good passive components (eg. transformer, caps) often sound better than active circuits. examples, I/V conversion in a DAC.

The gain by going active versus passive is a poor engineering choice. Better to put your dollars into better speaker drivers, etc.

Since I cant hear much difference between passive or active(and I've tried both), why should I pay more? So my distortion analyzer or Praxis can tell me my speaker is .5% better? I call that poor engineering.

I hope that my expensive experiments might save someone else from going down a road that's only going to cost them money and not gain them much better sound.

Linkwitz may be a genious, but to say that his design choice is the only good engineering choice is silly. The best speakers I've heard all use passive crossovers.

If you are using chipamps then by all means try it. But I wouldnt go into a totally active speaker project thinking you need alot of high quality amps. You'll break your bank account and be unhappy in the end.

One nice benefit of active is that using expensive amps doesnt really help. I've almost found that a bunch of cheap Panasonic receivers sounds as good as Class-A SS amps for much less money.

The crossover for me is WHERE the mojo happens. It has to be first rate. The only thing more important is your selection of drivers and cabinet size/porting. If you dont get the crossover right you will hate your speakers.
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Old 8th September 2006, 02:13 PM   #26
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Engineering is all about trade-offs to reach a given set of goals. Everyone has different goals and values the trade-offs differently. I enjoy building amps, so have plenty. The cost of the amplifiers is not an issue for me. For those who must buy quality amps, cost is obviously an issue.

Apparently the great unwashed masses cannot hear the difference between a low bitrate MP3s and SACDs, so for them we're not going anywhere near the aspirations of the majority of us here. It's a matter of how far out we are willing to go on the cost/benefit curve and how we define the point of diminishing returns.

I will gladly eliminate opamps when possible, but if one of the design priorities happens to be board space, discrete buffers, gain stages and line drivers may not be a viable option. Certainly there are opamps that don't sound good, but there are also good sounding opamps and opamp implementations. Passive XO components, inductors in particular, are not without their issues, but seem to be a better option for you.

I think that we have pretty well established that to my ears the benefits of active crossovers outweigh the cost and to your ears they do not. You dislike equipment that others find acceptable. Fine, lets agree to disagree.

That's a big part of the fun of this hobby for me - finding out what makes an audible difference to me and what doesn't. I really didn't expect to hear a difference between my Leach amps and my A75s, but I did. Hmm, lets try something else now and see if I like it better.

BTW, for me crossover design is where the MOJO is, and is MORE important than box tuning and driver selection (assuming a basic quality level has been met).
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Old 8th September 2006, 03:06 PM   #27
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Quote:
I consider this good enough, not a limiting problem. I have not heard any other weird buzzing or other noises. There are other bigger fish to fry in terms of making my system perform better.
I urge you to see about averaged power response at listening position. That is a mighty fish to check out and its nothing to fix since you have the dbx already. What measurement system you use?
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Old 8th September 2006, 04:26 PM   #28
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I use LAUD 3.1 on an old 486 desktop computer with an Echo DSP sound card. I have had this system for a long time.
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Old 9th September 2006, 06:16 AM   #29
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The finest speaker system I have ever heard is a 4 way active system built by lenard audio. lenardaudio.com.au

Lenard only makes 4 way active systems since 1977 and horn loading is his favorite. He uses industrial style of components ie PA but his results are true audiofile . The Opal series are heaven and the Cinema System is the finest sounding cinema I have experienced (the Chauvel in Paddington, Sydney. Australia.)

Lenard has told me that active can and is the ideal, but to beware of poor quality active crossovers.
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Old 9th September 2006, 06:23 AM   #30
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I am finding it interesting the several references to this piece of equipment as non-audiophile, while many of the reviews (including the AudioXpress "mod" recently published, refer to it as a production/profressional quality piece of equipment. What is it about DCX2496 that would make any/some/all of you consider it not up to "audiophile" quality/standards? Thanks,

Terry



Quote:
Originally posted by BobEllis


When I refer to passive crossovers, I mean power level, I don't consider passive line level crossovers viable - See Linkwitz for many reasons.

I think a point often missed by many active crossover experimenters is that the comparison must be made apples to apples - the transfer functions should be the same for the active and passive crossovers for a comparison to be valid.

Simply dialing in an active LR4 at the desired frequency is only slightly more valid than using the textbook formula to design a passive crossover (the active xo won't be affected by the drivers' impedance changes making it "slightly more valid").

A competently designed passive crossover can sound about as good as a competently designed active crossover, at the expense of a system efficiency and (slight) loss of amp control over the drivers. However, some systems make passive crossovers impractical, such as Linkwitz' Orion.

An advantage of the active approach is fairly easy incorporation of notches, peaking and shelving equalization as well as phase correction. Rare is the accurate driver that does not need some or all of these.

Of course this all can be accomplished passively, at the cost of further power loss in the crossover. Better crossover designers can incorporate shelving types of EQ (such as baffle step compensation) into the basic crossover without increasing parts count. See Zaph's ZD5 project for an example (although the phase alignment in the tweeter section adds a few parts)

Don't forget that arriving at your passive crossover with $300 in parts will probably have many parts leftover. If you're a serial builder, like many here, fine, you'll probably end up using them in another project. I have a hard time with "carrying inventory" although I have built up quite a stock of crossover parts over the years.

For prototyping I now have several adjustable analog active crossover boards (MOX) that can be daisy chained to achieve a variety of slopes. I'm also building modular EQs in their prototyping area. Pretty much nothing will get thrown away in development.

On the hiss front, I've often seen it said that the Behringer and dBx boxes need to be run pretty much at full signal to maximize their S/N, and attenuated afterwards. The only way to do this and have each section track accurately is with a stepped attenuator on each output. This way you'll attenuate any hiss along with the signal. I haven't felt a compelling need to do this with my analog crossovers yet.
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