Active networks, are they better or worse than passive? Speaker level possible?

[Fast1]

With all the big talk of big dollar capacitors and such and eleaborate networks to get things "just right", I have to wonder if there is any down side to active systems? in my more modern mind, it certainly seems that an active Xover system would be a hands down winner in the ability to easily set drop points, slopes, etc. I guess there might not be any actives out there that can run speaker level output to avoid the need for byamping so maybe that is the plus for passives.

While on the subject, I did want to ask about byamping. Would you guys stick with the same brand or series of amp for low and high F amping or does it matter? I realize not NEAR as much power is needed on the HF side but quality is most important there... I run a Rotel RB1090 on my 7s right now and it would be sad to have to buy even more amps since that one can more than handle the 7s.

[Islander]

Downsides? Well, they cost more money and you need to find out the settings for yourself, unless some very knowledgeable engineer has worked them out for your particular speakers, as in the case of the Jubilee and JubScala speakers.

Running at line level is considered to be an advantage, since the amps are connected directly to the speakers' drivers, with no distortion-causing components in the way. If you go to the complication and expense of an active crossover, bi-amping really makes sense. If the active crossover also has built-in delay units, it allows you to time-align the drivers, something that's worthwhile, but not possible with passives.

As for HF versus LF power needs, it depends on where the crossover from low to high is set. In the case of the two speakers I mentioned, the crossover point is around 480Hz, meaning that the LF covers the lower 5 octaves of the audio range, while the HF covers the upper 5 octaves. That works out to equal power needs for both, which is why matching amps are usually recommended for that particular setup. It simplifies gain matching and gives consistent tone from bottom to top.

Also, when amps are only asked to reproduce part of the frequency range, distortion is reduced.

There's a chart somewhere that shows the how the LF:HF power ratio varies with the crossover point, but I don't see it in my bookmarks. As a general observation, when the point is set above 1000Hz, the required HF power is noticeably smaller, but the woofer and bass horn are not operating in their optimum range. As usual in engineering, everything is a trade-off.

[djk]

Duo-amp vs Bi-amp

• Posted by

djk(M) on September 20, 2003 at 12:30:27

In Reply to:
Biamping - I had no idea. posted by mikemalter
on September 18, 2003 at 22:14:48:

"Let us adopt the phrase 'duo-amping' to distinguish
bi-amp(using a frequency dividing network ahead of the amps)from the
practice of using two amps
with their inputs wyed together driving the speaker crossover
sections.The phrase 'vertical bi-amping' has low popularity and is too
similar.All it will take is a little concerted effort to eliminate the
confusion."

http://db.audioasylum.com/cgi/m.pl?forum=general&n=7542&highlight=duo-amping&r=&session=

"If you use an electronic crossover and bi-amp a speaker like a
Klipsch
Cornwall with a 50W amp on the bass and a 10W amp on the mid and hf it will
play as loud as a 400W amp through the passive crossover.

If you
'bi-amp' your Newform speakers
with a 250W
amp on the bass and a 160W amp on the hf without an elecronic crossover
it will play as loud as the 160W amp would play running both.

The 4:1 benefit for bi-amping is only there when the spectrum is divided
ahead of the power amps
and when the division point is near the mid point of the spectral
distribution of energy.On a voltage basis the division occurs around
250hz.This must be weighted by the peak to average ratio so that the
equal energy point for above and below the crossover is about 500hz.This
is also affected by the slope of the crossover.For the example of the Klipsch

Cornwall it has a 600hz crossover
point.If the drivers were the same efficency then 50W + 50W would = 200W
through the passive crossover.In reality the HF is 10dB more efficent
than the LF so we only need 50W + 5W to = 200W.If the HF remains
undistorted it will mask distortion from the LF amp driven slightly into
clipping.

This means that if we use a 10W HF amp with a 50W LF
amp it would take 400W to play the same level undistorted through the
passive crossover.

If you 'bi-amp' your Newform speakers without
an electronic
crossover each amp will be receiving full range signal and will clip
at the same point it did with only one amp hooked up to the speakers.It
does sound different to do this, but make no mistake, you will not be
getting the benefits of dividing the signal ahead of the amplifiers."

http://db.audioasylum.com/cgi/m.pl?forum=general&n=164118&highlight=cornwall+bi-amp+djk&r=&session=

[Chris A]

Would you guys stick with the same brand or series of amp for low and high F amping or does it matter?

I don't see any reason to stay with one amp type, other than it is more compact in the amp rack to use stereo amps to bi-amp your two-way speakers-one stereo amp per speaker (...see how I slipped that one in? [6]...)

In fact, it is the reason why you might want to invest in excellent-but-low-power amps for your hf while using something more forgiving (economically) for your low-efficiency woofers.

I realize not NEAR as much power is needed on the HF side but quality is most important there

Roger that. Note that it's been my experience that high quality pre-amps are usually cheaper to build than high quality (read: class "A" SS or tube) power amps.

I find that a lot of folks here ignore the effects of passive crossover component issues [Ohmic heating on device properties, heating of components inside the box, part stability over time (particularly, but not limited to caps), parasitic losses on the power amp(s), and weird net impedance loads that some power amps have trouble driving]. All that is simplified when using active multi-amping--you use one amp channel per driver with nothing in between.

Chris

[DrWho]

One advantage to using the same kind of amp for the LF and HF is that you won't have to compensate for gain or phase differences....but that's simply a matter of convenience. I only bring it up because it needs to be a consideration in the approach.

[Coytee]

One advantage to using the same kind of amp for the LF and HF is that you won't have to compensate for gain or phase differences....but that's simply a matter of convenience. I only bring it up because it needs to be a consideration in the approach.

You have me lost on the phase part however, if a monkey like me can adjust for the gain differences.... then I'd venture to say about any monkey could do it.

[Fast1]

Thanks guys! I notice a lot of you guys are running actives here. It was sort of a no brainer in car audio "not that long ago" when crossovers were not inegrated in the amps. I guess if I wait for a right deal on another RB1090, I would be all set as long as I get actives with gains for each channel.

I did want to ask if there are any actives that are in the form of PC cards so I could possibly integrate them into my HTPC??? I think we are getting real close over here to just creating our own preamp in the HTPC. We already have an HD audio section that gives a very flexible parametric, decoding, etc.

If there are no PC card types, do any of these function with software or just potetiometer adjusters? I DO have tuning software and mic/preamp, etc for testing. I presume i can just do swep testing of each component in the speaker to decide where to crossoer point and slope should be.

Can you build a compound slope in any of these actives? Ie, 12db for 1 octave, then 48db after that?

[mark1101]

If someone tests or is using a PC based speaker processor..........let's talk about it!!!!!

[Guest " "]

The last time I looked into this, KLIPSCH instructions for Bi-amping did not include by-passing the crossover componets. The crossover componets will protect your drivers from below cutoff thumps, and other amp noise misfortunes.

In terms of hype, all thats happining here is just a transfer of the tweak point. Some folks tweak crossover caps. Other folks tweak opamps and other internal componets within an active xover.

certianlly, the varible range xover provide flexibility......more buttons to play with....gauges to watch....etc....all of which can be "proven" with qualitative and quantatative mathamatics.

[DrWho]

In terms of hype, all thats happining here is just a transfer of the tweak point. Some folks tweak crossover caps. Other folks tweak opamps and other internal componets within an active xover.

I'm not sure I buy that...

The engineers at Klipsch use an active xover to voice the speaker, and then try their best to get a passive xover to approximate the response they get from the active.

The reason Klipsch would never encourage active xovers is because the technical skill required to do it properly is way beyond that of the average public. It's not cost-effective for Klipsch to take on the liability and customer service overhead to teach their customers how to do it right. But that said, there are custom high-end designs from Klipsch that come with active xover settings should you desire to puruse that path.

In the pro audio world, active xovers are the defacto standard for anything high-end and a lot of the low-end gear is moving towards active now too (since it's cheaper and offers more performance at the same time). It's just a matter of time until it becomes standard in the consumer market. Heck, Klipsch already has the CS-700 which has the active xover built into receiver.

[Chris A]

The reason Klipsch would never encourage active xovers is because the technical skill required to do it properly is way beyond that of the average public. It's not cost-effective for Klipsch to take on the liability and customer service overhead to teach their customers how to do it right.

I agree with the statement in principle but note that many people who have been associated with this forum do not qualify as "average public". My concern is that someone here might misunderstand the statement to mean "too hard for me" and nothing could be further from the truth, IMHO.

If speaker manufacturers started to sell their mid- and high-end speakers with outboard active crossovers (or recommending third-party units) in the consumer marketplace, then I think people would use them. I believe the real issue that stops most manufacturers is "...we've never done it that way before...", and a buying public that hasn't been educated on the advantages.

High-quality passive crossovers for high quality loudspeakers probably cost a lot more than matching-quality digital crossovers, and the digital crossovers are much more immune to drift over time.

Why don't most consumer manufacturers use balanced cables and XLR connectors (which are superior RCA cables) - is it only cost? I doubt it. Space constraints? Well, no, not really. "We've never done it that way before?" Probably, yes.

But that said, there are custom high-end designs from Klipsch that come with active xover settings should you desire to peruse that path.

I think many people on this forum miss this point - and they're not looking at the Klipsch Professional line of products.

Too bad - "there's no accounting for taste". []

Chris

[DrWho]

Why don't most consumer manufacturers use balanced cables and XLR connectors (which are superior RCA cables) - is it only cost? I doubt it. Space constraints? Well, no, not really. "We've never done it that way before?" Probably, yes.

I think cost and industry standards (precedent) have a big deal to do with it, but if I were going for the ultimate in high-fidelity, I would actually stick to single ended interconnects...

Btw, two XLR jacks and a cable with two XLR plugs (the minimum required for a single interconnect) is going to cost over 5x more than two RCA jacks and a cable with two RCA plugs. And that doesn't even include the tripling of opamps required for a balanced interconnect. So there's another 3x the cost factor in the circuitry too. I'd rather spend $3 on an opamp instead of using three $1 opamps... With a 10:1 cost model, and with the connections compromising about 10% of the product cost, you're talking an MSRP increasing by 10 times to the customer just to throw XLR's on there. So your $50 product becomes $500 unless you want to reduce your margins...or you cut the cost elsewhere....

[Chris A]

Well Mike - I guess that I don't know anything...

Chris

[djk]

I am another one not in favor of cheap balanced inputs, the sound quality can be quite poor.

I have run unbalanced line-level signals in excess of 100' with no problems.

An unbalanced line used with a transformer can be much quieter than 99% of balanced systems.

I think one reason PWK didn't like biamping is that back in the day, electronic crossovers had very poor opamps with very poor quality coupling capacitors, and the overall sound was very poor.