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.
The fact that transmission lines are hard to execute well doesn't mean it can't be done. Indeed, it's being done right now by several manufacturers. And having built more bad transmission lines than you can shake a stick at, even an amateur like myself has learned a few tricks.

I've had fairly low-Q sealed enclosures and transmission lines side-by-side using the same drivers (KEF B-110 woofers, Dynaudio D28 tweeter), and even an amateur-built TL was (in the opinion of classmates who participated in informal blind listening tests) considerably more realistic sounding.

Regarding "pressure relief" enclosures, yes Sean I was talking about vario-vented (and homemade resistive vented) enclosures. I didn't use the term "aperiodic", as that term can also be correctly applied to a Qtc = .5 sealed box, and I didn't want to confuse things.

If excellent power transfer in the bass region (as indicated by a very smooth impedance curve, especially around system resonance) is a high priority, and if the only advantage of the sealed box is extreme ease of design, then why not consider the transmission line, or for that matter its ultra-simple cousin the pressure-relief box? They have much better power transfer - and by implication better linearity - in the bass region than a sealed box does, if indeed the impedance curve is an accurate predictor.

Not trying to be confrontational Sean; just tossing my favorite enclosure into the ring against yours....


Ernie: I am well aware that there are exceptions to the generalizations that i've made. From what i have seen and heard, they do exist. They just aren't commonly found or available due to going against the grain of the marketing hype that currently exists. Dealers don't want to carry products that don't sell and these products don't sell because the average consumer hasn't been educated or know what to listen for or how to listen for it.

For this, i blame the audio industry and the press. They are responsible for the "trick bag" that the "high end" audio industry has worked itself into. Due to their marketing games and the profit margins generated from under-designed products, the average consumer can't tell the difference from a "salon" speaker to a Best Buy speaker. That's because they all demonstrate severe forms of non-linearity. The only differences that they can tell is if one is louder than the others and if it produces more bass. I also forgot that they know how to look at the price tag, which has them scratching their heads and asking why they should spend THAT much more without getting measurably superior performance.

Duke: Given proper design, a TL will always be larger than a sealed design. To most people, size counts. Regardless of how many advancements have been made in TL design, they are infinitely more difficult to design / build / manufacture than an equivalent sealed design. Since manufacturers and DIYer's are less apt to venture into such waters, i've tried promoting a design concept that is both simple and cost effective to work with and produce while offering excellent sonic performance.

As i've mentioned before, i don't consider the simple sealed box to be the ultimate in design. I do consider it to be the best bang for the buck with the least skill and knowledge required. As Mr Dartford stated, the less potential to screw things up ( i.e. the simpler that you keep them ), the more likely you are to achieve a higher percentage of success.

Once one has achieved a high level of succcess through following sound ( as in "proper" ) design & engineering practices, refining the basic design and striving for the highest levels of performance enters into the world of diminishing returns. The last few percentile of measurable performance tends to cost more than what it would cost to build another system of similar stature.

As such, i would rather see folks get 80% - 90% of the performance out of their systems at a reasonable cost than to see them pay exhorbitant amounts for much reduced performance. The fact that many end up doing the latter rather than the former due to being fooled by advertising and marketing trends makes it harder to recruit civilians and keep this industry strong. It is difficult to justify added ( let alone exhorbitant ) expenses when the ends don't justify the means.

As with any type of system or project, should one choose to seek a higher level of performance than covering the basics with good design principles and proper implimentation, they should bring their wallets and valium with them. It is a steep slope that will have one stepping into uncharted territory. That is, as far as most audiophiles and even most "pro's" are concerned.

As such, getting past the marketing hype and high prices is only a small portion of why i promote sealed designs as heavily as i do. The fact that they have the potential to perform in both a measurably and sonically superior level compared to 95% of the designs out there while taking up less physical space could only be considered a benefit.

Either way, people can buy / build / spend their money on whatever it is they like. As i've said before, there's no sense in catering to someone else's preferences. As i've also said before, those that are interested in achieving optimum results without spending maximum cash need to educate themselves on the subjects. The more that an individual knows, the less likely that someone else ( me included ) is to steer them in the wrong direction. Sean
Time has shown the difficulty in designing a good Transmission Line. Also, as the name has a certain magic to it, some have claimed their designs to be TL, when in fact, they are not. I think the problem is that it requires a unique personality to achieve the goal. One with intelligence, creativity, self confidence, and the right balance of objectivism and subjectivism.

The key to building a TL is experimentation, and the ability to do so. A "test mule" must be constructed, which allows access to the inside of the cabinet, in order to try different materials and varying amounts of said material. Two important things to first get right are the line itself and the driver to be used in the line. The driver's Q must be capable of matching the line, as line damping can accommodate some variation, yet only to a point.

In terms of line damping, this can be likened to the style of cooking or sauce one implements. We know we are eating beef - the TL, and that it will fried, then finished in the oven - the driver. However, the implementation of which can vary a lot - that is the damping.

I have found often that lines are overdamped, which phenomenally lessens the amount of bass the speaker will produce and makes me wonder why a TL was the choice in the first place. A TL that makes no bass is not worth the trouble in the first place. Hopefully, the cabinet has the abilty for the designer to get in there and alter the stuffing.

A TL isn't something that one will get right on their first, or even third attempt, and that is probably a reason they haven't achieved more market share. While it can be said that complexity and cost are big factors, and I do agree, we audiophiles have proven we are willing to pay the freight when it comes to expensive gear.