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Do You Have A Target Response You Aim For?
My reason for asking is simply shear curiosity; this is not a troll 
. I ask because it seems like I always end up with a tweeter level a couple dB down from the mid; I don't aim for that (or try to target that response), it's just the way it [usually] works out. To be honest, I don't have a target response, I try to put the drivers where they sound ok to me, but it usually ends up this way. I had someone say I might reconsider my xover when he saw my response, he mentioned he always aims for "flat".
IMO (and I know everyone's ears are different)... whenever I make the response flat (as opposed to the tweeter being a dB or 2 down), the piano sounds too much like a harp, and the upper range of vocals can have too much "sizzle".
Just curious, if you guys don't mind sharing... what do you typically end up with? And do you begin with that goal in mind?
. I ask because it seems like I always end up with a tweeter level a couple dB down from the mid; I don't aim for that (or try to target that response), it's just the way it [usually] works out. To be honest, I don't have a target response, I try to put the drivers where they sound ok to me, but it usually ends up this way. I had someone say I might reconsider my xover when he saw my response, he mentioned he always aims for "flat".IMO (and I know everyone's ears are different)... whenever I make the response flat (as opposed to the tweeter being a dB or 2 down), the piano sounds too much like a harp, and the upper range of vocals can have too much "sizzle".
Just curious, if you guys don't mind sharing... what do you typically end up with? And do you begin with that goal in mind?
Comments
For a 3way, it is pretty flat. This could be for a number of reasons. The last few that I've done had fairly low crossover points and that contributed quite a bit.
I don't, however, like a bump in the 100 -350 Hz range. Everything sounds muddy if I get that range wrong. That is where it gets tough to passively cross the woofer low in a 3 way with higher slopes. 2nd order accoustic almost always is the best sounding to me.
On larger speakers, I tend to try and flatten things out a bit on the bottom end - if a design has legitimate bass below 50Hz, I find a peak in the response in a speaker like that ends up sounding a little too thick for me - that is dependent on a number of other factors, though. The Taiga are flat anechoic to below 40Hz, and have an F3 of 33Hz. In my room, I can get very useful output to well below 30Hz, which is outside my range of hearing these days. When I listen side by side with a smaller speaker that may only extend to 45Hz or 50Hz F3 but have a peak engineered in - the bass is much better in Taiga. While fundamental content in music or even a lot of movies will rarely go below 40 or 50Hz - there are a lot of harmonics happening way down low and the bass (IMHO) sounds much more natural if the speaker is capable of reproducing those harmonics.
Any speakers with an F3 higher than 65-80Hz generally sounds pretty lifeless to me absent a subwoofer helping out. They can be fun, but in an attempt to fatten up the tonality on these little guys - we sometimes add boost in the form of a peaky tune or other methods. I find small designs like that sound way better tuned flat and a subwoofer added into the mix. They end up too "wooden", boomy, one-notey otherwise.
Seems contradictory to my live sound tuning - but since I, as the soundguy, am creating the sound from scratch I control the overall spectrum such that nothing really goes missing despite a relatively high cutoff frequency (I usually high pass the subs around 45Hz) and the 3-4db peak I add to the kick and bass around that 60-80Hz region. Of course, I also EQ the FOH to as flat as possible and EQ the individual instruments to add that "flavor".
When the drivers allow it (and it is easier with drivers lacking significant breakup and using lower order slopes), I target a gentle downward spectral tile across most speakers I design. Sometimes as little as 1db between the bass peak and the upper range of my hearing - in some cases as much as 3db. I prefer to maintain a smooth response, meaning I don't just drop the tweeter 3db - think a ramp rather than a step.
The BBC dip may have originally been conceived of as a passive EQ for nearfield monitors - but as has been noticed by many designers over the years, it is also an excellent method of compensating for off-axis bloom in LR designs. I have found 4th order LR designs without this dip to generally be too forward, and the way designers fill that dip in adds considerably to the tweeter strain. A lot of designers will unintentionally create a bass boost on the bottom end of the tweeter to flatten things out on-axis, and depending on other factors such as diffraction control and directivity that isn't in and of itself a bad thing - but it is demanding a lot more excursion from a very small driver in a region of the spectrum that we are sensitive to. These days, I will almost always leave a natural BBC dip in place. Things just sound better to me that way.
In simulators it is easy to get carried away throwing components at the tweeter to create that boost and flatten things out and get a pretty reverse null and all those things that those who engage in pure simulations will obsess over very often resulting in disappointing sound. It is easy to blame insertion losses - but it is my considered opinion many of those disappointing results are from straining tweeters. You can see this effect in many posted simulations - look at tweeter transfer functions, the boost is obvious on many of them.
I don't know if I have "a sound" or not, most of my speakers seem to sound different to me. Sometimes it is deliberate, sometimes it is the result of other factors that I do not want to attempt to control such as distortion within a driver passband. There are ways to minimize that, however - such as the extra padding I used on the midrange driver of my stand mount Realistic 3-way, for example. This is getting out of "measurable target response", and into "what does the subjectively correct tonality" measure like, however. I think common complaints of brightness can largely be attributed to the excess tweeter strain in many LR networks as well as not paying attention to odd-order distortion. Some say it doesn't matter below a certain point - and they may be right (to a certain point) - but non-linear distortion definitely adds to the sonic signature and should be treated the same as linear distortion. That is to say, if you are using a midrange that, at best, offers -45db 3rd order distortion across the passband and a woofer and a tweeter that are -55db 3rd order - you are going to notice that disparity in the overall tonality of the speaker. So, targeting a specific response curve without knowing how your drivers are behaving in the odd-order distortion category will yield less than excellent results. Note: steeper slopes on drivers with rising distortion in the crossover region (most drivers) will exacerbate that issue. I discovered that on Cabrini Redux - a design which has very low measured distortion with the low order slopes. When I added a capacitor to the woofer network to try and get a 4th LR out of it, it caused some serious peaking in the distortion and definitely degraded the sound, despite a very similar on-axis response. I would have had to drive the crossover point well below what the tweeter was capable of playing to hammer the distortion back down, which creates other issues. So that is now a consideration when I am designing.
Where I listen to music here is a black hole and what I do for home differs from any other environment, so I hesitate to give advice on low end tuning. For example, a pair of AE TD-15S in sealed 5cf cabinets will sound thin here without a hefty amount of EQ, but would probably rock most of your homes.
Less good transfer function:
Icky transfer function:
Just representative. Do enough modeling and you will see how it is so easy to end up with such icky transfer functions.