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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
cdc
1,862 posts
 
So the conclusion to this post is that most people haven't been educated to the sound of high-end audio? The uneducated listener will look for big bass and how loud it plays? Probably true.
I may be a more educated listener now than 3 years ago when I got myself into this mess but I still miss the lack of bass, especially on drums.
Correct my mistakes here but I see bass as more than just frequency response. That is a steady state condition. In music apparent bass has attack, sustain, and decay.
I have not heard better bass than what an active speaker can do. My thought is the lack of **dynamic compression**. I think most amps clip and you aren't getting all the bass that is coming from the source in a passive speaker. A well-designed active amp/driver combination doesn't compress dynamically. So you get the sock-in the chest whump. This is not a steady state condition and is vital to perceived bass.
A slow decay can mask detail and make bass sound bloated. Can't a vented design use an overdamped design which will give the bigger bass of a vent while still keeping bass "tight" due to fast decay?
So I conclude that dynamic, uncompressed bass attack that is well damped/ controlled by the amp can give big bass that people desire without being bloated. Also the more air moved = more perceived bass. There is no inherent problem that multiple bass drivers = too much bass and if well designed would give less dynamic compression and be tighter than a single bass driver. Look at line arrays for example.
I heard JM Labs Alto Utopia recently and it had way better bass definition than my Nautilus. I would have sworn it must have been sealed from the way Sean described a seal design but JM Labs says it's vented. So vented designs can sound tight. But the downside was that it sounded very lean - the offset of getting cleaner bass.
Some questions I have:
1) Is it better to go with a sealed box and bass heavy electronics like Musical Fidelity 308?
2) If you put a speaker closer to the wall for more bass, would this make bass muddy the same as a vented design? It seem so to my ears.
3) First order bass rolloff is better than the 4th-order you get from a vented design? In an actual room bass will be boosted 3-6 dB/octave and a first order rolloff could give too much bass. Note how reviewers have a hard time setting up Theils. Fourth-order rolloff is much easier to set up
sean OP
6,231 posts
 
Cdc: While i personally believe it takes "big power" to do bass correctly with most "audiophile approved" type speakers, this is only a very small percentage of the big picture. None the less, i put my money where my mouth is and have 1000+ wpc driving my dual subs in my main system, 1200 wpc driving my HT mains with 1600 watts driving just the subs in that system, a dedicated amp rated at 100 wpc driving the subs in my bedroom system, 800 wpc driving the speakers in my office system, etc...

As you mentioned, dynamic compression, rise and fall times, ringing, phase shift, frequency response linearity, loading characteristics ( Z aka "impedance" at resonance, etc... are all other important factors. Given that vented designs typically have poorer rise and fall times with increased ringing, and vents introduce multiple phase shifts rather then the one that sealed designs offer, and typically have peaks at resonance whereas low Q sealed and stuffed designs don't, and vented designs typically have a higher impedance, which translates into less amplifier control and ability to load power than a low Q sealed design does, etc... Obviously, you can see where i'm going with this without me continuing any further.

As to your question about "playing with the damping of vent", this can be done. This is much the approach of a stuffed Transmission line and a Vario-Vent or "Aperiodic" design. Both offer many of the benefits found in sealed designs and may even surpass sealed designs in some areas. These are both somewhat "tricky" to design though. Some of the old Dynaco speakers were "Vario-Vents" and produced very good bass output AND definition for their size. That is, so long as you kept the spl range within reason.

As far as the JMLab's speakers go, i thought that the they sounded "barrel-chested". I think that much of this could be solved by adding damping material into the cabinet. The reason that it sounds like a "barrel" is that you literally have a large open wooden chamber resonating away. By adding damping material, you reduce both the excitation of the cabinet itself and absorb some of the energy that would otherwise be bouncing around in the cabinet causing a "bass echo" or "ringing".

In terms of "tighter bass" sounding "lean", that is a common thought. That's why i've stated that people are just TOO used to "bass slop". When they hear what tightly controlled bass with minimal overshoot and ringing sounds like, the articulation and definition is readily apparent but they still can't get used to NOT hearing all of the overhang. Most equate "bass slop" with "bass weight", which isn't quite the same thing.

As to your specific questions, here goes:

1) As to your comment about Musical Fidelity gear, most that i've heard sounds noticeably lean. Haven't heard all of their models though, so can't answer that specific part of the equation.

As far as i'm concerned, you shoot for speed and neutrality throughout the entire system. If you try to go with any other approach, you're back to "complimentary colourations".

2) Properly designed speakers are designed to work with specific room boundary effects taken into account. If a manufacturer doesn't provide basic suggestions as to where the speakers should be placed, chances are, the speakers are going to sound VERY different from room to room. Since obtaining neutral response in a consistent manner should be the goal of most "audiophiles", speaker design and placement become key factors in what we hear and total system performance.

Other than that, most designs already suffer from bloated bass as it is. Adding further low frequency reinforcement by placing the speakers closer to a corner, rear wall or both, etc.. will only make the presentation sound thicker and slower. With that in mind, some high-tech speakers with a lot of research put into them are designed to be placed up against the wall. If you pull them out from the wall, you'll have too lean of a presentation.

3) It is not so much the roll-off that makes a speaker hard to set-up, it the "Q" of the peak at resonance. Q covers both the amplitude and bandwidth at resonance. Speakers with a lower peak at resonance will be easier to place because the bass sounds less "one notey". Speakers with a narrower bandwidth peak will also be easier to place because they have less chance of exciting the various multiple nodes spread over a wider frequency range that exist in every room.

What the shallower roll-off of a sealed design offers is greater usable output below resonance. Once a vent is done, it drops like a rock. Anything below the point of resonance on a vented system unloads ( minimizes damping ) on both the vent and the driver. Excursion of the driver increases and the bass becomes quite muddied due to the uncontrolled extension. Better vented designs, like that of the Merlin's, use some type of high pass filtering to minimize these problems.

As far as Thiel's go, the placement problems with them may be two-fold. First of all, they use passive radiators. Passive's are slower than ports in terms of transient response. Slower response sounds muddier, making it harder to find a position in the room where the "mud" is reduced AND nodes aren't excited. Couple this with treble response that may require slightly different speaker positioning to work optimally and you've got yourself a lot of work ahead of you finding a good compromise between the two.

This is why i said that properly designed speakers will take into account room reinforcement. The designer should be able to give you an idea of where the speaker will work best in your room. While every room is a little different and may require some trial and error, those suggestions should get you pretty much in the ballpark. After all, they are familiar with the bass peaks, roll-off rate and can factor in room reinforcement from there. On top of that, they should have taken into account these factors when designing the rest of the speaker too, so the mid / treble radiation pattern should be designed to compliment optimum bass reproduction.

As i've mentioned before, very few speakers take all of this into account. If they did, you would be seeing a lot more "oddly" shaped speakers with acoustic treatment on the baffles. Reducing diffraction of the baffle itself is one thing, but taking into account room interaction with that baffle is one step ahead of most designs. Sean
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gregm
3,411 posts
 
Isn't it utopia (no pun) to expect full-range response from a commercial passive, dynamic speaker??

Ultimately, CAN there be such a thing as a passive, dynamic, FULL-range speaker within physical & electrical & COMMERCIAL reason???
Let's look at rule of the thumb parametres of a "good" speaker -- as we've discussed it 'till now.

Take good sealed box with a Fs say of 60 Hz (not bad!). Say we equalise it (we're making happy assumptions here, and considering an anechoic room) to reach 30Hz (i.e., we need to equalise ~12db/octave). Already, that one octave will require an extra 16x as many W to reach the same spl as the 60 (as in W=P^2/rho).
Now, the original 60 was quite impressive anyway, and probably required some equalisation in the first place (say, baffle step, etc) so there is some extra energy used there too. Say a 6db/octave loss from 120Hz -- so we need 4x the watts from 120 to 60.

In other words, for 1W at 120Hz, we'll use ~65W for our 30Hz. Looks OK? Think about 2W at 120 requiring ~130W for the 30Hz. And so on...

The results in W availability look staggering. Hardly atractive in a commercial product...

Or are my numbers wrong (which they could be:))?. Or does in-room compensation save the day -- by how much??? +2-3db?? Still, that doesn't save us from having to opt for Sean's kWatt amplification -- and Sean's only using that for his BASS drivers... other amps(s) drive the rest of the speaker...

No wonder some people in the past used Onken for the low bass... No wonder, bi-amping is in the air!
subaruguru
1,376 posts
 
The "thickening" in response when one tries to get more bass warmth by taking advantage of walls' reinforcement is more due to the automatic "revoicing" of the upper-bass/low-mids region due to the change from in frequency of the 2pi/4pi transition. MOST speakers sound muddy and congested when wall/floor mounted if they're designed to work in free space. It's interesting to note that the JM Labs and PSB surrounds seem to be their normal 2 way monitors stuffed into a different cabinet, without modification of the crossover, and hence these speakers sounded quite wrong when wall-mounted, yet very nice on stands. OTOH the Boston VR-MX surrounds, for example, sound very well balanced when wall-mounted, being voiced that way. Indeed some speakers do require some front wall support for proper bass response, but there's a pont where the boundary support frequency "lift" band goes up as the distance goes down, until when wall-mounted, the speaker usually sounds congested in the lower mids.
Sean, great post, but again, if a properly designed vented cabinet uses a nice low Fs, and the driver's happily within its excursion limits, what's wrong with a 24/dB drop below, let's say 30-40Hz? Of course "sealed" is easier to get right, but the total bass power response always requires a bigger cabinet.
gregm
3,411 posts
 
Ernie, I'm piping in here:
what's wrong with a 24/dB drop below, let's say 30-40Hz (...) if a properly designed vented cabinet uses a nice low Fs, and the driver's happily within its excursion limits

It doesn't sound impossible -- BUT:
Problem seems, it's not very easy to do and COSTLY. The cabinet would be very large (and/) OR, the "clarity" of the bass reproduction, as in how many bass "notes" actually come across, could (still) suffer...
More to the point the COST of the appropriate driver(s) could easily skyrocket the retail price of the speaker. Example: an average Lambda woofer (they have good /reasonably priced woofers) costs $~280ea; say the manufacturer buys these at $150/pair --

So? We've just added $1500 to the retail price of the speaker for an improvement which, while laudable for US here, is UNlikely to:
a) move opinion-"leaders" (i.e. reviewers)
b) be appreciated & impress many potential buyers, when the speaker is auditioned within the confines of a dealer's (or the buyer's) average listening room and the response anomalies most rooms produce in the bass

So, it's not likely to skyrocket sales... which is what manufacturers need in the first place (I'm not saying that's a bad thing:))
Cheers!
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