inversion) of the crossover through this midrange region, and also due to the woofer/midrange's very imperfect contribution to the crossover because it is in non-pistonic breakup mode through this midrange crossover region. So there seems little point in attempting to optimize the system's temporal performance through this midrange crossover region. It is of dubious value to go for temporal accuracy by giving flat on-axis response precedence over the total power response into room, hence over flat tonal balance as perceived by human listeners, especially given that the choice has already been made to sacrifice temporal accuracy through the vital and sensitive midrange crossover region. In other words, tonal balance accuracy is all that's left to shoot for as a goal, after the phase rotation decision for the third order crossover has been made.
If Verity were simply to delete this flattening filter, then the tonal balance recession in the Tamino's midrange would not be as severe. If this flattening filter were deleted, it might be necessary to re-think the concept of the Tamino's third order crossover, since this flattening filter does act as one of the 3 poles in the woofer/midrange driver's rolloff. But an asymmetrical crossover network might work satisfactorily, as might a change to a fourth order crossover network concept (this would allow a sharper electrical corner for the woofer/midrange driver's low pass filter, without imposing the premature downward slope that the present gentler first order electrical filter does).
Room Placement --
Properly placing the Taminos in your listening room for best sound is more critical than it is for most other loudspeakers. The sonic rewards are greater if you can do it right, and the sonic penalties worse if you can't (or don't bother). So here's a guide to doing it right. This will also help you determine if the Tamino is the best choice for your room setup.
As noted, the Tamino's tweeter sound forthright, articulate, and direct. It is actually very accurate for the spectral range it covers on its own. But, as noted, the immediately adjacent midrange crossover region sounds recessed, shy, ghostly, and indirect. This contrast makes the Tamino's tweeter output seem aurally overly prominent in comparison, even though the tweeter output is in fact accurate.
But there's good news. Sonically, the tweeter's prominence can be effectively counterbalanced if you can get enough richness in the warmth region (100-300 Hz) out of the Tamino. If you don't get enough warmth out of the Tamino, then it will wind up sounding too lean and bright, because then the only forthright, direct, and prominent spectral region would be from the tweeter.
Now, the warmth you get out of the Tamino is largely a function of how you place it in your listening room, relative to nearby wall boundaries. The Tamino turns out to be especially sensitive to this placement, more so than most other loudspeakers, because of its design philosophy.
Most other loudspeakers are deliberately designed with an abundance of rich warmth, because it gives them more pleasingly musical tone and makes them sound larger. Likewise, many other loudspeakers are deliberately designed with a response hump, and/or with high Q, in the upper bass (say 50-100 Hz), to make them sound as though they had more lower bass output than they in fact do. These deliberate design tactics are doubly tempting for other loudspeakers because there's no engineering tradeoff penalty for bestowing rich warmth and rich upper bass, whereas there are many engineering tradeoff penalties for trying to give powerful lower bass to a loudspeaker.
-- The Warmth Hump
Every loudspeaker is affected in its warmth region by how close to your room walls you place it. That's because any nearby room boundary, such as a wall, reflects sound from the loudspeaker back to you. For simplicity here, consider just the wall of your room that's in back of a loudspeaker. The acoustic output from the loudspeaker (which is omnidirectional at these lower frequencies) will take some time to travel back to the wall, and will reflect off that wall on a return trip toward the loudspeaker location, and will then join up with the fresh, new output from the loudspeaker, as both the direct and the temporally delayed reflected outputs join forces on their way toward your ears.
At a certain frequency in the warmth region, the loudspeaker will be half an acoustic wavelength away from this wall. What does this mean? By the time the reflected acoustic energy (reflected from the wall) reaches the loudspeaker on its return trip, it will be perfectly in synch with the fresh new output from the loudspeaker, so the two acoustic signals will add as they join forces on their way to your ears. The result? You'll hear more energy at this frequency from this in-synch addition, thus richer warmth at this frequency from your loudspeaker. Assuming that your walls are completely reflective at this frequency, say 140 Hz, you'd hear double the output from your loudspeaker at this frequency, which translates into a 3 dB rise in the frequency response as you experience it.
What happens at other nearby frequencies? The speed of sound remains substantially the same, so the travel time from the loudspeaker to the reflective wall and back again (to the loudspeaker location) stays the same, so the temporal delay to follow the reflected path and get back to the loudspeaker location stays the same. But, at a different frequency, the loudspeaker's fresh new waveform is no longer perfectly in synch with the reflected waveform.
If the frequency is slightly lower (say 130 Hz), then the signal waveform coming out of the loudspeaker will take slightly longer to cycle, since it is cycling less frequently, i.e. cycling at a lower frequency (in both senses). So the fresh new signal waveform coming out of the loudspeaker won't yet have reached its positive peak when the previous positive peak, reflected back from the wall, arrives back at the loudspeaker location, to join up with the fresh new output from the loudspeaker. Thus, the two acoustic waveforms will still join up and add, but they won't add up to double the amount as they did at 140 Hz, because they are not completely in synch at 130 Hz, with one reaching its positive peak later than the other. This means that there is still some warmth rise at 130 Hz, but it is less than the peak rise of 3 dB at 140 Hz.
Similarly, at a slightly higher frequency (say 150 Hz), the signal cycles faster, in a shorter time, so the fresh new output from the loudspeaker is already past its positive peak by the time the reflected signal gets back from the wall to the loudspeaker location for the two acoustic signals to join up and add together. Again, because they are not perfectly in synch at 150 Hz, the two acoustic signals adding together do produce a rise in warmth, but it is less than a doubling, less than a 3 dB rise.
The loudspeaker's frequency response curve, as you hear it, will have a rise in the warmth region that looks like a broad mild hump, with this hump peaking at 140 Hz (at 3 dB or less), and skirts tapering down to both lower and higher adjacent frequencies in the warmth region.
The frequency, at which this broad, gentle hump in the warmth region has its peak, is determined by the distance you locate the loudspeaker from the wall. If you locate the loudspeaker closer to the wall, you obviously shorten the travel time that it takes the speed of sound to get from the loudspeaker to the reflecting wall and back again to the loudspeaker position. When you shorten the travel time, this clearly means that the positive peaks will synch together perfectly only for a signal frequency coming from the loudspeaker that has a quicker, shorter cycling time - i.e. a signal that is at a higher frequency. The simple consequence is that moving the loudspeaker closer to the reflecting wall raises the frequency of this hump in the warmth region.
When you choose to locate your loudspeaker a certain distance from the wall in back of it, you are thereby choosing the frequency in the warmth region where you'll hear this hump that boosts or enriches a portion of the warmth region. The same thing is true of the distance you choose to the side wall, or to a corner, since these add further boosts, at frequencies you determine by their distance from the loudspeaker location (the geometry of the reflected signal path is more complex here, but the basic principles are the same). And of course this same thing is also true of each and every one of the loudspeakers in your surround array.
Now, most other loudspeakers are deliberately designed to have sufficiently rich warmth without relying on this boost from nearby walls. Indeed, even the smallest mini-monitors, which are often used out in moderately free space up on stands (away from even the floor as a boosting reflective surface), are usually designed to have sufficiently rich warmth without needing a boost from nearby reflective surfaces.
This design feature gives you considerable flexibility in locating all those other loudspeakers within your listening room. Since they have sufficiently rich warmth at all frequencies, without needing any boost from a nearby wall, you are free to place them in a variety of room locations. You could, for example, place such a loudspeaker so that the gentle warmth hump it receives from the wall in back of it is at a frequency that sounds best to you. More likely, you would want to locate such a loudspeaker so that the frequency response notch from the back wall, an octave lower (see below), coincides with the heavy upper bass boom you probably get from the high Q of the woofer or the port, to cancel it out. Or, more likely still, you would want to locate such a loudspeaker so that the time delays of the reflected paths from the walls best enhance the spatial imaging. You have the freedom to pursue these other sonic goals because you don't have to worry about locating such a loudspeaker to get sufficient warmth boost from nearby walls.
But the Tamino is designed differently.
The Tamino is designed to depend on the boost it gets from nearby walls, in order to give it sufficient warmth. And getting sufficient warmth is particularly crucial if you want to get a musically natural overall tonal balance from the Tamino. As discussed above, the Tamino's inherent tonal balance puts the spectral regions covered by the tweeter (the upper midrange and trebles) into prominence, not because the tweeter is doing anything wrong, but rather because the tweeter is so accurately forthright, direct, and articulate, which is in great sonic contrast to the immediately midrange crossover region that sounds shy, recessed, indirect, and ghostly. This would give the Tamino an overall bright, lean tonal balance, unless we give the Tamino sufficiently rich warmth energy to counterbalance the tweeter's output.
The Tamino's lower frequency output is deliberately designed to exploit the boost from nearby reflective walls, in order to give it sufficiently rich warmth. In one sense this is a very enlightened design tactic. The Tamino is designed to work best in real rooms with real walls, not in some ivory tower free space. Unlike most other loudspeakers, the Tamino's warmth and bass is not rich, heavy, and boomy in free space. Indeed, the Tamino's bass design merits particular praise for its low Q (less boomy, better definition) bass. By utilizing the natural boost that nearby walls (and the floor) give to some lower frequencies, the Tamino can with this boost achieve a very natural overall tonal balance, with sufficiently rich warmth to counterbalance the forthright, direct tweeter output (the various colorations in the midrange crossover region still of course persist).
Moreover, just as with other loudspeakers, you can choose which warmth frequency to place that slight warmth boost at, by simply moving the Tamino closer to or farther from the wall in back of it. For example, if you choose to locate the Tamino 4 feet from the wall in back of it, the peak of the gently boosting warmth hump will be at 140 Hz. If you want to move this warmth boost higher in frequency, simply locate the Tamino closer than 4 feet to the wall in back of it, and if you want to move this warmth boost lower in frequency, simply locate the Tamino farther than 4 feet from the wall in back of it.
-- The Evil Dip
So far, so good. But, alas, the laws of physics also impose a problem upon these best laid plans of mice and men. Ther laws of physics dictate that the helpful, gentle 3 dB hump, whose help the Tamino needs, has an evil twin brother, also produced by reflection from the wall in back of the loudspeaker. This evil twin brother is a dip in frequency response, which takes place at a frequency half of the frequency (one octave down) that you have chosen for the hump by locating the loudspeaker closer to or farther from the wall in back of it.
To make matters worse, this evil twin brother dip does a lot more harm than the gentle hump does good. The good hump adds a gentle boost of up to 3 dB, but the evil dip can produce a severe cancellation notch that is many, many dB down. The gentle hump of 3 dB is achieved when two positive peaks of the acoustic waveform are in perfect synch, and add to twice the positive peak value, which is 3 dB up. But at half the frequency, the fresh new output from the loudspeaker is a full half cycle behind the reflection from the wall, when it arrives back at the loudspeaker location, so the fresh new output is at its negative peak value. The two acoustic signals still join forces and algebraically add, on their way to you the listener. When you add together a full negative peak to a full positive reflected peak, you get zero, zilch. And zilch is not just 3 dB down, but an infinite dB down (you still get some output at this frequency from other wall reflections, from other parts of the wall, but the basic point here is still valid, that the dip can be very severe, and is far greater than the gentle 3 dB boost one octave higher).
Because the evil dip is so much worse than the helpful hump, it is more important that, in choosing your loudspeaker's location relative to your room walls, you pay more attention to placing that evil dip at the least damaging frequency, rather than placing the gentle hump at the most helpful frequency. So our hopes, of optimally placing the Tamino's location to get the most helpful warmth boost for its overall tonal balance, are dashed, as we find ourselves instead having to worry more about locating the Tamino so that this severe dip does not cut into the Tamino's already precarious warmth region.
Note that with other loudspeakers, designed to have sufficiently rich warmth in open space free field conditions, we don't need any warmth boost, so we don't have to worry about needing to get warmth boost from a nearby wall at a particular frequency, and thus we can be quite flexible in placing that loudspeaker location relative to nearby walls. Likewise, since such loudspeakers already have rich warmth at all frequencies, it becomes less critical at which frequency we choose to put that severe warmth dip, again achieved by our choice of loudspeaker location relative to nearby walls.
However, with the Tamino, it does need that warmth boost, and, even more importantly, it can't stand to have the severe dip moved up into the warmth region. That would even further lessen the amount of warmth that the Tamino has, even below the amount of warmth it has in open space free field conditions, which is not sufficient, so that would make the Tamino sound too lean.
To test this out, we conducted research with the Tamino, deliberately varying its distance from the wall in back of it -- and thereby varying the frequencies, both of the beneficial warmth hump from wall reflection reinforcement and of the undesirable dip (one octave down) from wall reflection cancellation. Sure enough, as soon as we moved the Tamino to within 3 feet of that wall, the Tamino's sound became much too lean. At this 3 foot distance, the gentle warmth-enhancing hump would be at 200 Hz, which is fine, but the evil severe dip, one octave down, was at 100 Hz, and this was a high enough frequency to severely rob the Tamino of much needed warmth. On the other hand, when we moved the Tamino out to be 4 feet away from that wall, it sounded great, with nicely rich warmth counterbalancing its tweeter output. At this 4 foot distance, the gentle warmth-enhancing hump was at 140 Hz, which was even more helpful than 200 Hz for enhancing the Tamino's fullness. And, more importantly, the evil severe dip was moved down to 70 Hz, which is far enough below the warmth region so that this dip did not adversely cut into the Tamino's warmth output.
Thus, the Tamino's design, which deliberately depends on nearby walls for sufficient warmth, is a good idea in the abstract, since it does take account of real world room conditions, taking account of the warmth boost that nearby reflecting walls provide, and indeed depending on that boost. But, precisely because it does depend on that warmth boost, this aspect of the Tamino's design also makes it very critical of proper room placement relative to nearby walls.
And, as we confirmed in practice by research experiment, this also makes the Tamino super critical of room placement, not so much because you need to obtain the optimum frequency for the warmth boost, but rather because you need to avoid the wrong frequency for the warmth dip. Specifically, you need to place the Tamino far enough from the wall in back of it so that the severe dip is kept at a frequency below the warmth region, and this means a distance of 4 feet (or slightly greater). Note again that critical location is not such a problem for most other loudspeakers, since they already have a generous amount of warmth, and therefore are not hurt as severely by the evil severe dip, at whatever frequency you choose to place it via your choice of loudspeaker location.
In short, if you want to get sufficient warmth to hear a natural tonal balance from the Tamino, your placement choice is restricted to being 4 feet (or slightly greater) from the wall in back of it, in order to avoid that evil dip cutting into the warmth region. This 4 foot minimum distance requirement happens to be a good thing in some other sonic aspects. For example, in order to get the very best spatial imaging out of any good loudspeaker, and also to get the most transparent sound with the least muddying, it is helpful to have wall reflections of upper frequencies be time delayed so that they are within (or slightly beyond) the Haas window threshold of 10 to 15 milliseconds. Locating a loudspeaker at least 4 feet away from the wall in back of it means that the upper frequency reflections from that wall will be delayed at least 8 milliseconds, which is getting close to the optimum range. In contrast, locating a loudspeaker closer than 4 feet from that wall creates a delay of less than 8 milliseconds, which is significantly less than the optimum range for our ear/brain to perceive imaging cues, and which also muddies the sound because our ear/brain integrates sounds that are clumped together within a time window much less than the 10 millisecond delay (so our ear/brain would hear the transparent sounds from the loudspeaker itself muddied by the early reflections arriving sooner than 8 milliseconds, reflections which our ear/brain would confusedly try to integrate with the direct sound from the loudspeaker).
(Continued on page 101)