Active Speakers Don't Sound Better

I think the active discussion has gone off the rails into detials that are NOT the main reasons for active. Here is my summary of reasons.

1) phase linearity (via line level adjustments in the crossover). Many designers think this is the key reason to do it, as adjusting phase of drivers is practically impossible with passive crossovers and very easy with active ones.

2) Calibration of each band via the ability to adjust individual driver levels to compensate for manufacturing differences in the drivers, which can vary 1/4 to 1/2dB at best and 2 or 3 dB at worst). This is not a subtle differnce because a 1/2dB down or up across the entire bandwidth of the driver is very audible. In tests here we’ve had sucess hearing a 1/4dB level change when applied across the entire midrange or tweeter. 1/2dB in EQ across a small part of the band or a group of frequencies is very difficult to hear for many.

3) No speaker level filltering, only line level filtering in analog or digital. FIltering as it applies to passive crossovers is far less precise and controllable and is not changeable with driver changes. Precise level calibration and filtering means you can make two identical speakers actually sound identical instead of slightly different. (this is the dirty secret of hi fi)

4) Freedom from driver temperature fluctuations, which can signficantly impact driver dynamic range and level. Called power compression and thermal compression as the system can be precisely calibrated to apply limiters to keep this from happening. The sonic penalty of a well designed limiter is far less than an overheated driver.

5) No massive losses of power or dampening factor though long runs of cable from amp to driver, compounded by the large amount of copper wire in low frequency inductors in passive crossovers. Active cable runs are very short.

6) Ability to provide sufficient dynamic power to a given set of drivers by "matching" the right size amp to the driver, rather than under or over power the entire system.

7) Lower cost/higher value for a given level of amp performance by avoiding expensive outboard amp chassis (excepting outboard active with multiple amplifiers). Cosmetics a large part of the manufacuring cost of all amplifiers.

Brad

Brad --

Ad 1. Definitely agree, although there are different ways to approach phase implementation. Usually we have a limited number of phase bands to go by that’re set and fixed around each driver section, meaning only one chosen value per band. Linear phase filters (FIR-filtration in the DSP domain) on the other hand have over 60,000 phase points over the frequency region and offer some unique possibilities here, although it’s also more processing heavy which in turn can have its drawbacks with an audible ghosting effect.

In any case phase correction has degrees of importance, not least with larger, horn-loaded speakers, and it’s one of the reasons why active config. pairs so well with this speaker segment. Another reason is being given the opportunity to use very steep filter slopes to more effectively and sensibly use horns within their bandwidth range, and thereby avoid off-band irregularities. This is also why many haven’t heard what horn-based speakers can really do when properly implemented actively. Passive filters simply fall short here.

Ad 2. I can also set gain in 0.25dB increments with my Xilica DSP, of course with each driver section, which is indeed audible and to the point even that we’d prefer having 0.1dB gain steps.

Ad 3. Precision with active filtering is a big plus, yes, and also comes in handy with notch placements, not to mention their q-value and gain factor. Another advantage with horn-based speakers.

Ad 4. The limiting factor here is that imposed by the drivers and the passive crossovers themselves; the latter when thermally challenged will lead to fluctuations in filter values, and this further exacerbates this issue of (the nature of) the lower precision found in passive filters. Active filters on line level will remain rock solid and totally impervious no matter the load. Where drivers are concerned the use of limiters aren’t needed when power handling is prodigious, aided not least by higher efficiency.

Ad 5. I’d question the significance of speaker cable runs no more than ~10 feet per channel with proper gauge, certainly as the only medium between the amps and drivers. Crossover coils, another matter, not least in conjunction with steep phase angles created by passive crossovers and its components on the whole. The purer impedance load with active is a vital factor in its advantage.

Ad 6. You can hardly over power the system. If a high power solution sounds great, it sounds great. I’ve used 30W class A power and 600W class A/B ditto with 111dB horns, and the latter, high power solution didn’t fall short - on the contrary. The "right size" amp, from my chair, is really about having (more than) enough power, and where plentiful - depending on the design - isn’t a disadvantage. With that out of the way it’s really about finding the right sounding amp, and using the same topology/design top to bottom is paramount to my ears - even into the subs region. Outboard active gives you more opportunities here.

Another, very important aspect with active configuration is having amp-driver independent bands, as well as using the different amps in limited frequency ranges. In a 3-way system like my own the top band, 600W amp is only fed with a ~620Hz on up signal (with 6th order filters); it cruises along with its direct-connected 111dB horn/compression driver section, and the distortion is at an absolute minimum - even at blasting levels. On the end of the scale a similar sub amp, also 600W, can blast along as much as it wants to (which likely never amounts to more than 10-20 watts, at most), and it won’t have any effect whatsoever on the 2 other amps with their driver sections used above. In a passive setup the typically single amp covers the entire frequency and driver range; what it does down low affects everything above.

Ad 7. Agree on the cosmetics part, but practically speaking many if not most active speakers suffer from overall amp quality compared to outboard solutions. Not everyone is at ATC level here. Yes, used actively the amps can more effectively reach their fuller performance envelope, but that doesn’t negate the impact of absolute amp quality.

DSP can help with poor design choices and it is easy simple affordable flexible. But it does have a sound quality. I would also say your sample size of 1 active build isn't enough to form a truly useful opinion. On active verses passive. I have built 100s of passives and dozens of actives and I don't think one is better than another they are tools to meet a design goal.

Eric, I agree with room treatments making much of the difference in what we hear, that said  the higher performance we reach for from speakers the more revealing of source.

@mbmi

Stuck in what way? The only thing that internal true active changes (like ATC, Genelec, etc)is a choice in power amps and a ton of speaker level wire (to the speaker and tons of hidden wire inside the passive crossover). Due to the increase in "color" created by all that wire between amp and driver, the amp is a smaller contributor that it should be in front of all that wire. Once all that wire is removed everything else is revealed in a new way. Suddenly preamps, turntables, stands, line level cables, CD players, etc are far more audible and changes in those components yields an even larger result that before. I have the definitive experience where transitioning from passive to active INCREASES the hobby in revealing more differences in everything else, not less!

Brad