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Current Trends in multi thousand dollar speakers

Have any of you been paying attention to the current trends in larger multi-woofer speakers that cost multiple thousands of dollars? So that many of you can follow along, i'll use the Legacy Focus 20/20's at $6K, the Piega C8's at $15K and the Aerial 20T's at $23K as points of reference. All of these have been reviewed in Stereophile over the last few months. If you're not familiar with these, all of them are vertical dynamic designs using multiple woofers in vented cabinets.

If you look at the response of of these speakers, they all have very pronounced bass peaks with elevated low frequency plateau's taking place. Of these three, the Legacy's are by far the worst of the bunch. Not only do they diverge from neutrality the most ( +7 dB peak @ 100 Hz ), their elevated bass output or "low frequency plateau" levels out at 40 Hz and at 400 Hz. That is over 3+ octaves of "extra" output that wasn't on the recording. Above 400 Hz, the output levels off with very noticeable rippling slightly above that point in the midrange and multiple large peaks with a dip up in the treble response. Below 40 Hz, the output drops like a rock. The reason that the plateau levels out at 40 Hz is because of the associated sharp roll-off associated with vents below their point of resonance.

To sum things up, this speaker, which Paul Bolin raved about in Stereophile, is anything but "smooth" or "linear" in reproduction. As can be seen in the graphs, there is a very definite "boom & sizzle" type of response taking place here. As a side note, i found that the Legacy Signature III's showed a similar large bass peak centered at appr 100 - 110 Hz, so this would seem to be a consistent design attribute / "house sound" / "family voice" to Legacy speakers.

Moving onto the Piega's, their overall response looks to be measurably smoother than the Legacy's from the midrange on up. As far as bass goes, the Piega's peak occurs at an amplitude of +5 dB's and is centered at appr 85 Hz. Their "bass plateau" is quite wide, actually just as wide as that of the Legacy. Both show the same appr "elevated output" aka "bloat" from about 40 Hz to 400 Hz. Much like the Legacy's, the Piega shows the typical sharp roll-off below 40 Hz due to the output of the vent being out of phase with that of the undamped woofer. Even though both speakers show very similar plateau's and a similar F3 ( -3 dB point ), the Legacy's bass plateau has both a higher peak and a higher average.

Moving up to the $23K price range, we've got the Aerial 20T's. Similar to the Piega's, the Aerial's are reasonably smooth in response from the mids on up with a few low amplitude peaks and dips. Side by side comparisons though, it would appear that the Piega's are a little "flatter".

When it comes to low frequency performance, the Aerial's produced a +5 db peak centered at appr 60 Hz. Of the three speakers mentioned here, the amplitude of the peak is the same of the Piega's ( +5 dB's ), which is much lower ( 66% reduction ) than that of the +7 dB peak of the Legacy's. Even with this 66% reduction of the peak amplitude at resonance compared to the Legacy's, we are still talking about a divurgence of +5 dB's here!!!

As far as the "bass plateau" goes with the 20T's, this speaker is much more linear than either of the above. While the Aerial's also level out at appr 40 Hz and drop like a rock below that point, the upper end of the bass region is MUCH smoother. Whereas the others were contributing added output up to appr 400 Hz, the Aerial's are leveling out at appr 120 Hz or so. In effect, the Aerial's appear to offer the most controlled bass with the least amount of bass colouration. Then again, they are by far the most expensive also.


As far as low frequency extension is concerned, the Aerial's resonance peak is centered the lowest of the three i.e. 60 Hz for the Aerial's vs 85 Hz for the Piega's and 100 Hz for the Legacy. Even though the Aerial's have a resonance that is 25 Hz below that of the Piega's and 40% lower in frequency than the Legacy's, all of their -3 dB points are within a very few Hz of each other. While the graph's aren't completely legible, it appears that the F3 ( -3 dB point ) for all of these speakers are right about 34 - 38 Hz or so. How do such different designs achieve similar F3's? It has to do with the tuning of the vents and the amplitude of the peaks at resonance.

By creating a huge peak at resonance, it takes longer for the amplitude of the signal to fall off. As such, the Legacy's much larger peak at resonance allows it to achieve appr the same F3 on paper that the other designs worked harder to achieve. As such, were the Legacy's designed this way because they like the sound of massive bloat? Were they designed this way so that they could claim a lower F3? Could it be a combo of the two? We'll probably never know.

What does all of this add up to? Judged in comparison to each other and strictly talking about bass linearity, the Aerial looks the best on paper by far. Why just on paper? Because we have to factor in the added gain associated with in-room response. Our ears hear the entire presentation i.e. the speaker and how the speaker loads up / pressurizes & excites the room. As such, what looks the best on paper may not be what you like the most in your room. If you're room is properly set-up, the results on paper and the results in the room should pretty well jive. That is, at least as far as frequency response & linearity go. There are a LOT of other factors going on here though, not to mention personal preference.

What happens if the room isn't properly set up? Compared to anechoic responses, all speakers will have greater output / added extension when placed in an average listening room. While specific speaker placement comes into play in terms of the extension and amount of boost, most rooms will produce maximum ouput somewhere in the 50 - 80 Hz range. Obviously, this varies with the size and shape of the room.

The net effect is that these speakers are going to produce even MORE bass than what they already show in these graphs. Not only are we picking up low frequency output from what is called "room gain" ( "cabin gain" in a vehicle ) by pressurizing the room, we are also going to be exciting the resonances of the room too. All of this adds up to GOBS more "apparent bass". Add in the fact that this bass lacks speed and control* and you've got "bloated, ill-defined thump" running rampant.

Other than that, one has to wonder just how extended the bass response of these designs would be if they didn't have such HUGE peaks? After all, the higher the peak at resonance, the lower the -3 dB point of the speaker appears to be. Do we have to add "bloat" to get extension? How do you get around all of this and still keep good sound? That's easy but it is a completely different subject : )

What i want to know is, what do you folks think about this type of performance at these price levels? Is there anything that we can learn from this? Do we see a specific trend taking place here and in other parts of the audio market? Inquiring minds want to know : ) Sean
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* vented designs all suffer from a lack of transient response, increased ringing, over-shoot and phase problems. In this respect, a well designed port is typically "more linear" than a passive radiator.
sean
eldartford
4,262 posts
 
A few random thoughts:

Stereophile reviews of $20K-$30K loudspeakers are about as important to me as Flying magazine reviews of Learjets.

In my engineering work we consider the "baseline" design as "something from which to deviate". I think that flat frequency response is a similar situation. If the drivers/crossover/enclosure has a lot of peaks and dips in the response, it will be difficult to tune it to sound good.
So I would say that a speaker with flat response is a technically well-designed product, but perhaps has not been given that final step of artistic (non-technical) tuning.

As far as the high end goes, in my system I find that my MG1.6 sound good to my ears (which are vintage units) but I did install 1.5 ohm tweeter padding resistors (worth 3dB) so as to avoid frequent use of my tone control. I have no idea how "flat" the high end is.
With regard to the low frequency range, I have an elaborate (6 diver) subwoofer system, and an Audio Control Richter Scale 1/3 octave equalizer/analyser. I can make it flat down to near 20 Hz. It's an interesting technical tour-de-force, but music sounds better when I permit a substantial boost of the kind that Sean decries in his comment.

Spectral balance of music is highly subjective. Using classical as an example orchestration and conductor preference varies greatly. Does the performance highlight the cellos or the violins? Musical instruments themselves vary greatly. Different cellos sound different.
And then there is the recording engineer, twisting his dials to suit his subjective tastes. And when all this is said and done, I still have my tone controls to play with.

Other characteristics of loudspeaker are, I think, much more important. In very highly regarded speakers, I still hear too much IM distortion. Harmonic distortion is hard to distinguish from the music, which includes harmonics, but IM sticks out like a sore thumb. IM distortion is what makes a speaker sound like a speaker.

I have a fond memory of "full range" drivers, because when I began this hobby that was what almost everyone used. However, the way that a full range driver gets its HF ability is cone "breakup", where the center part of the cone is vibrating differently from the outer part. "Whizzer" cones take cone breakup to a greater extent.
Somehow the idea of all this uncontrolled vibration going on in the cone turns me off. Some full range drivers can sound pretty good, but this is an art, like building a violin, and characteristics of such a driver will change as the cone materials age. If you want to have "coherency" of HF and LF, I think that a coaxial driver is a better approach.
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drubin
3,275 posts
 
Is multi-woofer the culprit?
sean OP
6,231 posts
 
No, using multiple woofers is not the culprit. Poor design skills, using too small of a cabinet for the given drivers and not enough internal damping material inside the cabinets themselves are the culprits. Larger cabinets produce resonance at a lower frequency, hence offering more linear bass extension. Poor tuning of the ports / improper bass alignment is what produces the single huge peak. The very wide bass plateau's are caused by not using enough damping material inside the cabinet. Just further evidence that too many "manufacturers" are using "computer software" to design their products. They do this because they don't really know how to build & design a speaker on their own, let alone tweak the results that the computer program itself provided.

As a side note, most people think that vented designs should use physically smaller cabinets than sealed designs. That is exactly the opposite of the truth in most cases. The general public has been lead to believe this because many companies use vents in very small speakers. This was not to give more bass extension so much as it was to "fool you" into thinking the speaker had better bass. What they did is give you more apparent bass with higher sensitivity i.e. quantity over quality. The whole reason that Edgar Villchur and Henry Kloss designed the acoustic suspension speaker was that it offered the best bass response characteristics that one could achieve in a smaller box.

At the time that they were designing the Acoustic Suspension speaker, other designs used some type of vent or open baffle and the cabinet had to be HUGE to get any kind of deep bass out of it. Not only do acoustic suspension speakers provide better transient response, they also offer a slower roll-off below the point of resonance. As such, a vented design that resonates at 45 Hz will be -24 dB down at 22.5 Hz ( one octave ). A sealed design that resonates at 50 Hz ( vents always look more impressive on paper ) is only -12 dB down at 25 Hz. You tell me which speaker has better extension in the real world. Then factor in transient response, which sealed speakers do better. Now ask yourself why a manufacturer would want to use a vent and you'll figure it out soon enough. They are cheaper to build, cheaper to ship, offer more apparent bass and take less power to pressurize the room. The bottom line is more profit, more bass, more sales.

With such a situation, how can they lose? There is only one way that they could. So long as they keep the consumer in the dark and hope that they never become educated or learn how and what to listen for, they'll keep racking up sales by pushing garbage out the door. High profit garbage at that. Sean
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gregm
3,409 posts
 
Long -- sorry.
Holzhauer sez: "I ... have far more faith in a large group of people who are familiar with live music calling a system realistic sounding than I do a set of scientific measurements."
Agreed -- but I think you'd be VERY surprised at how CLOSELY measurements of speaker response can reflect the comments of this "large group of people".
Ever since I've been dabbling at diy & measuring speakers, I have been astounded at this.

Sean notes:
"Other than that, I'm all for products that are designed to work with their environment."
Problem is, which PARTICULAR environment -- i.e. speakers tuned to my present room will not sound as good in another room OR even my next room. So anechoic is the norm (for manufacturers who can AFFORD a dedicated anechoic room).
-------

On to contemporary, giga$$ passive speakers. I wonder if what Sean is asking for (i.e. good, accurate low end extension) is really possible in a commercial passive set-up?

First, I notice that the mid-to-high extension and response have been addressed quite well... at a cost, of course.

Many expensive speakers offer supersonic response, well into the 30kHz -- some (Kharma, etc) going up to 80kHz with the Thiel & partner hard ceramic (diamond) tweets.
Some (say, many British products) are tuned to a "BBC dip" of a few db towards the 3kHz point. This makes the sound more "pleasant" to the ear.
Many (very expensive) offerings have succeeded in offering a seamless response in the critical midrange -- even more than that (say 100 -- 10kHz)

However, I wonder of there are ANY passive speakers that can offer a bass response to match their upper extension. I really wonder whether it is POSSIBLE to do this WITHOUT a multi-amped set-up where the filter is BEHIND the amps. Eldatford, Sean, many others using this kind of set-up are a case in point.
I mean, imagine the SIZE of, say, a closed box q=0,7 speaker with f3 at ~25Hz and the amplification required to MOVE the thing!!
Worse, what's the market for this thing???

If you look at the Canadian NRC/Soundstage measurements here you will notice more of what Sean relates in his original post -- i.e. many (most) speakers rolling off as of ~60Hz.

Ultimately, I respectfully submit that:

1) choose the speakers by concentrating on timbre, tonality, (and ultimately phase) characteristics in the range down to ~60Hz MAX.

2) If you find that you need extra dbs in the low end spl, add another stereo speaker system (i.e. subwoofers) powered by another amp, for the last two octaves. Make those drivers 15" or better. Pray that the wife won't cringe!

Cheers
reb1208
518 posts
 
"What speakers measure flat"

If you are looking for full range sound with multiple woofers. Snell Acoustics makes one of the flatest measuring speakers ever made- as measured by Stereophile. The XA90ps with powered subs/parametric bass eq.
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