Active crossovers measurably better?

[Purité Audio]

ATC candidly will admit that active is a better solution but, it is the commercial imperative, dealers dont like actives.
It is the same reason why you need to have a ‘new’ company to make a speaker like the Kii/8C, can you see a traditional company making their entire range irrelevant at a stroke?
Keith

 

[Cosmik]

That's exactly what I did with my B&W 801Fs.
I have a description of the process and the graphs on my web site. https://sites.google.com/site/audiopages/
Unfortunately, it's not really possible to compare directly the before and after, as this compares 30 year old drivers and a 30 year old passive crossover, with 30 year old drivers, but new tweeters and a modern DSP-based crossover and equaliser.

It's probably more instructive to compare the original specification with my results, and the active version was clearly an improvement. The frequency response of the originals was +-2dB, still pretty good for a passive 'speakers, my version after equalisation was +-1dB. Harmonic Distortion was somewhat but not hugely better. Pair matching was closer, but again wasn't bad on the originals. Although the 801s were claimed to be mechanically time-aligned, using the DSP crossover, that could be improved, but again, not by much.

My conclusion is that a very good passive loudspeaker will be made better by going active, but not hugely so, whilst more modest passives will be much more improved.

When I was in the business, albeit over 30 years ago, I sold Meridian and John Bowers actives, much to the surprise of fellow dealers who wouldn't touch them. Their reasoning was that audiophiles liked to fiddle with cables, amplifiers etc, and would upgrade the cables, the amplifiers, do stupid things like passive biamping etc. All gave the dealer additional selling opportunities. Selling actives firstly made the sale a much bigger ticket item, so reducing the opportunities, and secondly, once sold that's it. No further upselling/upgrading.

I suspect that's behind ATC and PMCs continuing with passive versions of their loudspeakers, dealer pressure.
S.

Are you saying that those measurements are the sum total of the changes, Serge? Is it not possible that there are other factors (cone damping?) that don't show up in those measurements? Better behaviour with transients rather than just steady state waveforms? Phase shifts (the possibility of eliminating them with FIR filters)? Opportunities to better refine the crossover for ultimate uniformity of dispersion or reduction in intermodulation distortion? Stability of crossover versus power? Etc.?

 

[sergeauckland]

Are you saying that those measurements are the sum total of the changes, Serge? Is it not possible that there are other factors (cone damping?) that don't show up in those measurements? Better behaviour with transients rather than just steady state waveforms? Phase shifts (the possibility of eliminating them with FIR filters)? Opportunities to better refine the crossover for ultimate uniformity of dispersion or reduction in intermodulation distortion? Stability of crossover versus power? Etc.?

Indeed all those are factors, but as I've been convinced by active 'speakers since the early 1980s, I didn't need to measure more than I did, just to satisfy myself that what I had done was an improvement on the original.

S

 

[svart-hvitt]

But this would tell only half the story. Going active gives the designer more choice in the selection of drivers, and other aspects, so the difference should be more 'holistic' than just a straight swap for the passive crossover.

Here's a challenge: can you create a true multi-way speaker where you can switch between two completely different crossover setups (radically different frequencies, slopes) and hear no difference while playing music? With a DSP-based, driver-corrected, time aligned, linear phase three-way system, this demonstration is easily accomplished - in fact the final choice of crossover frequencies and slopes is almost arbitrary. The passive designer would be sweating over their version for months and could never achieve it: their version must always produce artefacts that are perhaps not obvious when static, but would be shown up with an instantaneous changeover.

@Cosmik ,

you wrote:

«Going active gives the designer more choice in the selection of drivers, and other aspects, so the difference should be more 'holistic' than just a straight swap for the passive crossover».

That seems to hit the nail on the head. Ilkka Rissanen of Genelec was recently asked if an analog version of The Ones (active DSP based 3-way coaxials) could be introduced at a lower cost. Ilkka answered thusly:

«I think the most important thing to notice is that we could not even make an identically performing analog version of the Ones. Digital signal processing is required there to have the performance and quality. It is an inherent part of the design and can't be dismissed or bypassed without serious consequences».
Source: https://www.gearslutz.com/board/showpost.php?p=13096139&postcount=272

In other words, a designer needs to make compromises when he designs a passive, analog speaker. These compromises means the designer makes deficient products when he markets an analog and an active DSP based version of the same speaker to survive in the marketplace.

I am a big believer in people who don’t make compromises, but aim for the best performance. In the end, I also think the best performers survive in a competitive landscape. Which, BTW, explains why so many producers pay the audiophile press to focus on everything but performance.

 

[dallasjustice]

I'm selling my JBL 4367 speakers which uses the same drivers and same waveguide technology as the active JBL M2. I hope to have a pair of JBL M2 setup in my room with FIR crossovers very soon. For now, I want to post a 1/12 per octave smoothed SPL and the Step response without using any DSP. This is just the raw speaker response using the passive crossovers. Later on, I'll post the same measurements from the same speaker/mic positions from the JBL M2 using FIR crossovers and driver time alignment. It should be an interesting comparison. All sweeps are calibrated to 83db in REW:

 

[March Audio]

Hi

What was the mic distance, I presume close as I see no roll off?

 

[RayDunzl]

I want to post...

If I may be so crass as to suggest:

Post the .mdat files (zip them and you can post them here, 2mb , max size).

And measure left/right/both from your listening position, please, if you don't already plan to. That's most interesting to me.

 

[dallasjustice]

Hi

What was the mic distance, I presume close as I see no roll off?

It’s about 9’. The mic is at listening position.

 

[dallasjustice]

If I may be so crass as to suggest:

Post the .mdat files (zip them and you can post them here, 2mb , max size).

And measure left/right/both from your listening position, please, if you don't already plan to. That's most interesting to me.

I can post the mdat files but I don’t want to post both speakers because my room is not perfectly symmetrical. So the response will vary a little because of slightly different reflections. I picked the speaker with the cleanest response. You can check phase and group delay if you want in the mdat files.

The only problem with the comparison is that the passive 4367 speaker crossovers EQ speaker response flat so I plan to digitally EQ the M2 to a flat response. I guess that may not be fair but the M2 speakers do require EQ like all loudspeakers.

 

[dallasjustice]

One notable thing about the 4367 is that you can see the difference in driver sensitivity below the crossover beginning at 800hz. I know there’s a pad which attempts normalize the D2 driver level to the midwoofer. But there’s still a little drop off below 800hz. I don’t anticipate the M2 will show the same issue as long as I set it up correctly.

 

[March Audio]

It’s about 9’. The mic is at listening position.

And there is no roll off???? What have I missed? They dont sound bright?

 

[stunta]

I'm selling my JBL 4367 speakers which uses the same drivers and same waveguide technology as the active JBL M2. I hope to have a pair of JBL M2 setup in my room with FIR crossovers very soon. For now, I want to post a 1/12 per octave smoothed SPL and the Step response without using any DSP. This is just the raw speaker response using the passive crossovers. Later on, I'll post the same measurements from the same speaker/mic positions from the JBL M2 using FIR crossovers and driver time alignment. It should be an interesting comparison. All sweeps are calibrated to 83db in REW:

View attachment 10301 View attachment 10302

Perfect! Thank you! Is there a guide (for dummies like me) on how to interpret these charts?

 

[dallasjustice]

And there is no roll off???? What have I missed? They dont sound bright?

This is not how I listen to them. I use DSP. I’m posting this because I just want to help address the OP’s question about the difference between active and passsive speakers.

My normal target curve has a nice downward tilt with a hinge at 1khz titling down to -4.5db to 20khz.

 

[RayDunzl]

I don’t want to post both speakers because my room is not perfectly symmetrical.

Neither is mine. But, in the end, I don't listen to one speaker.

(nor is my ear a microphone, but that's another story)

You can add a warning to not look at the measurement for both. Draw skulls and crossbones on the chart, or something.

 

[dallasjustice]

Neither is mine. But, in the end, I don't listen to one speaker.

I understand Ray. I remember what you said about measuring both speakers at the same time but I never really understood it.

 

[March Audio]

This is not how I listen to them. I use DSP. I’m posting this because I just want to help address the OP’s question about the difference between active and passsive speakers.

My normal target curve has a nice downward tilt with a hinge at 1khz titling down to -4.5db to 20khz.

Aahh that makes sense thanks. Im going to try and dig out my passive xo v dsp measurements.

 

[RayDunzl]

I remember what you said about measuring both speakers at the same time but I never really understood it.

In my room, the left and right traces at 50 Hz look reasonable.

But when both speakers play, the phase of the combination of the two waves are out of phase (around 50 Hz) and create a deep hole.

L/R/Both SPL

DON"T LOOK!

L/R Phase - around 180 degree difference = almost a null.

It's not so noticeable to the ear, but, there it is, right where I sit, nonetheless.

I haven't played with sub re-positioning yet.

 

[dallasjustice]

In my room, the left and right traces at 50 Hz look reasonable.

But when both speakers play, the phase of the combination of the two waves are out of phase (around 50 Hz) and create a deep hole.

L/R/Both SPL

DON"T LOOK!

View attachment 10304


L/R Phase - around 180 degree difference = almost a null.

View attachment 10305

It's not so noticeable to the ear, but, there it is, right where I sit, nonetheless.

I haven't played with sub re-positioning yet.

That makes sense to me. I understand. One mono sub and a crossover at 80hz would fix that problem.

 

[RayDunzl]

I have 4 cheap subs, two on each side.

The mains actually go lower.

I run them all down low as a reduction of distortion experiment. Three drivers on each side can run 9dB lower than a single for the same SPL.

My pending path-of-least-resistance experiment is to reverse two for a slightly lopsided dipole simulation.

 

[dallasjustice]

Perfect! Thank you! Is there a guide (for dummies like me) on how to interpret these charts?

The SPL sweep smoothed to 1/12 per octave is a good way to show the overall frequency balance of a speaker. It’s not the ultimate measurement but it’s a very helpful measurement to answer your question. It’s best to wait for me to overlay the active and passive measurements. Once you see that, I think it will be easy for you to get a feel for how they may sound different.

The other plot is a step response. It is probably the most useful time domain characterization of a loudspeaker. You can see there’s 2 spikes separated by about half a millisecond. That’s the tweeter followed by the midwoofer. The ideal step response should look like the one I posted above. In reality no speaker has this step response. But some active speakers come scary close. You can see that the JBL 4367 has a very good step response but not ideal. When I later overlay the M2, I think you’ll see how much better time domain is with a well designed active speaker.