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
>

* 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
Duke: Traditional vent systems typically tune the vent at the same appr frequency that the woofer resonates at. This produces two smaller "humps" rather than one larger hump. Bandwidth is increased and overall bass sensitivity also climbs over a wider region.

By doing so, you've now got two resonant points, which are really nothing more than undamped oscillation from the driver and the vent. These are two points of oscillation that the amplifier can't load into or control ( due to impedance peaks ), producing twice the potential for music to excite them with the resultant increase in "slop" i.e. undamped / uncontrolled output. Couple this with the elevated output due to the increased sensitivity in this region and the "room gain" that naturally takes place and you can see why we've ended up where we are today with MOST vented designs.

The other alternative to tuning a vent is to let the woofer resonate where it wants to in that cabinet and then tune the vent for whatever frequency that you want to try and extend output to. While this does increase extension somewhat and produce a shallower roll-off ( with resultant improvements in transient response ), the lowest region isn't as efficient as the upper region. This "can" produce a more natural presentation IF properly implimented, BUT, you've still got the associated phase shifts, lack of damping below the vent tuning frequency and reduced power transfer / lack of control associated with higher impedance peaks that vents typically demonstrate. In plain English, we've still got plenty of side-effects / problems to deal with using such an approach, even though they aren't as prominent as the more conventional designs.

As far as various alignments offering a different set of trade-offs, I know this and you know this, but in order to educate and share with those less familiar with the subject, you have to start with a base-line that they may be familiar with. As you mentioned, this type of tuning is not commonly used. That is why i didn't base my descriptions / argument on this type of vented design i.e. it's not widely used. Having said that, there is one very well known ( but NOT widely respected by audiophiles ) manufacturer that advocates such designs. That manufacturer is Cerwin-Vega.

As a side note, Stewart Hegeman used a very unique approach when designing vented speakers that some might consider to be similar to the above. I can see how it could have quite a bit of merit if properly applied. There is only one "manufacturer" that i know of using such an approach and that is Don Morrison Audio. While i've never heard these speakers, they do seem to try and tackle quite a few important aspects of speaker design. Don has been working with this design over time and seems to be on the right track from a technical perspective. If interested, Don also makes a small two piece preamp that some rave about. I am NOT "endorsing" or recommending either of these products although i will say that Don seems to be more than technically competent. Having said that, his preamp should go lower in frequency response though : )

Other than that, i know that Richard Shahinian of Shahinian Acoustics has acknowledged that Stewart Hegeman was a primary influence on his designs. Given that Hegeman was also one of the first that i know of to use metal cones ( not just for tweeters ) in his speaker designs, i would have to say that his thinking was ahead of many others. The first speaker that i know that used actual "metal" in it ( but not the whole cone / piston area ) was the Ohm A. While this was a revolutionary design in itself, i could be wrong here and there might have been others using "metal" in their drivers prior to the first Walsh based design. Sean
>
I use to sell the Hegeman model one speaker...back in the early 70's....I think thats what it was called. It did have a metal cone woofer mounted at the top on an angle with the tweeter mounted separately above the woofer dust cap. The tweeter I believe was a Philips dome ..These speakers had the best bass of any in that store..Even at my young age then..I new there was something special going on, the bass was fast and tuneful..though easy to overdrive..these speakers were maybe less than $400 a pair..Tom
Sean, thank you for the kind words, but I think you are more than capable of taking care of things here. You prove yourself here on Audiogon on a day in - day out basis. You demonstrate knowledge, experience, curiosity, truth, and passion when it comes to audio. And, you probably know that that statement right there is the highest praise I can ever bestow on anyone here on Audiogon.

Incidentally, my initial impressions of the TL speakers I have right now are incredibly favorable. While "only" sporting an 8" woofer, the size of the cabinet is pretty large, and I am quite impressed with the bass response. In my room, it is probably as good as things can get. I think we sometimes lose sight of the fact that a room will support a certain level of low frequency response, and again, I believe these speakers are putting out as much as the room will allow.

The AtmaSpheres are having no trouble at all with these speakers. Despite the "conventional wisdom" that TL drops efficiency by about 3 db, these relatively unmuscular amps are driving them to very high sound pressure levels, with explosive dynamics, without any strain whatsoever. I now subscribe to the other theory, that a TL actully presents a kind load to an amplifier. OTL amps do not normally take a hold of a woofer's voice coil, but in this circumstance, I have no complaints. In fact, the sensitivity is quite close to my Coincidents, which are incredibly easy to drive. My Line Tunnel Fried A/6 are not as efficient as these.

I will nevertheless try other amplifiers just to see what more they coax out of these speakers.

Overall, I am now more convinced that TL bass is the best one can get. There is a unique rightness to it, in addition to the weight and thunder. However, I will say that the Coincident Troubass subs(with a larger woofer, in a good sized cabinet) that I have do not take a backseat to these speaker's low frequencies, and I wonder if the added complexity of a TL is required. Perhaps in a different room the superiority of this design would be allowed to come forward, if it is there.

So, in the end, I think that while the TL reigns supreme, one should see if the design merits a purchase for them.
Sean, I DID read Dickason a decade ago, and contributed to the design of a couple of vented 2 ways with two pro designers. We ended up with a VERY fast and tight 2 way with a 35Hz vent. Was supposed to be an OE for Roland Digital Pianos, but never got past the first 40 pair or so.
The bottom end alignment was done by an old student of Peter Walker, using a dandy Peerless $40 woofer. I don't remember the electrical particulars, but it was a very quick, non-bloated design that was VERY dynamic, and impressed the handful of dealers I demo'd it to on the East Coast. It was a bit lean in free-space, so had to revoice it (damp the tweeter), but with a bit of normal boundary support (atop a piano or nearer a front wall) it sounded great for a modest 2-way with $300/pr total manufacturing cost....
Duke, you're absolutely correct...building a fast, damped, efficient vented design isn't that hard, although you're correct, Sean, it isn't done often due to market motivations. And what's wrong with poor performance below 30-32 Hz? These, and other well-designed modest vented two and three-ways are for MUSIC, not helicopters and earthquakes! Your posts are voluminous and helpful in reciting the liturgy, but in so doing sometimes mask objectivity. We know what we hear...and how it measured.
Cheers.
Ernie said: "Your posts are voluminous and helpful in reciting the liturgy, but in so doing sometimes mask objectivity. We know what we hear...and how it measured."

I guess that this is why "audio" will remain subjective forever. I know what i hear and know what i like. I'm sure that everyone else does too. The fact that what constitutes "poor sound" to me typically measures as such while others enjoy that sound makes the purchase of gear a personal decision, regardless of the facts involved. Knowing this, that's why i've stated many times over "buy what you like as you are the only one listening to it".

As a side note, there is gear that i like / is enjoyable to listen to even though it is highly "flavoured". Then again, i also realize this and would never consider such a presentation to be "accurate". Such a system would probably be owned and operated by a "music lover" more-so than an "audiophile". I don't think that either "label" is derogatory, they just signify different goals and listening preferences.

My comments were aimed at those that are interested in the "high end" reproduction of musical recordings i.e. those that seek both accuracy with musicality. Musicality by itself has many enjoyable flavours, but is only half the picture. If that is what someone prefers, so be it. I'm not here to tell them that they are wrong, i'm simply posting observations, comparing data and sharing a point of view. The fact that various points of view end up in debate is nothing new and is part of human nature.

I think that many folks have found themselves in one camp or the other, not by their own doing or ears, but by misguided suggestions from the press and marketing hype. Introducing facts into the equation may initially confuse and upset them, but in the long run, i was trying to help them become more informed and capable of making better long term decisions. After all, the more that you know about a subject, the more likely you are to be happy with the choices you make. Sean
>