Something that can happen with two way loudspeakers is this:
The radiation pattern of the woofer is quite narrow in the crossover region, while the radiation pattern of the tweeter is very wide. In fact, for equal on-axis sound pressure levels, the tweeter can be putting out as much as 18 dB more energy into the reverberant field. Now the more reflective the room and/or the farther back the listening position, the more the spectral balance of the reverberant sound will influence the perceived tonal balance. And this extra lower treble energy is right smack in the region that would make female vocals tend to sound harsh.
Just to test this theory out, you might try nearfield listening; that is, listening at a distance of 5 feet or less from the drivers. If the tonal balance is better at such close range, that indicates the first-arrival (on-axis) sound has a much smoother tonal balance than the reverberant (off-axis) sound.
It's also possible that the pillows you have stacked against the wall make any lower treble emphasis stand out even a little more, if the pillows are primarily absorptive at higher frequencies. I know nothing about the absorptive properties of pillows so this is sheer speculation on my part.
If an off-axis energy excess in the lower treble region is the root problem, in my opinion the solution is loudspeakers that have a more uniform radiation pattern. It is very hard to target a specific frequency region with absorptive room treatment; absorption tends to work better at high frequencies than at lower ones, so it's very hard to absorb lower treble energy without over-absorbing the upper treble energy.
You may also want to check the room for slap-echo if you haven't already, as that can be a source of "zing". Clap your hands and see if it "zings". If you have slap-echo, it will be worst in the region where the radiation pattern is widest - that is, in that lower treble region. In this case diffusion or (if necessary) absorption on one of the two offending bare wall surfaces should take care of it. Keep adjusting the area treated, and/or increasing the area treated, until the zing is gone.
Of course it's possible that your zing may have another cause, but these are two possible acoustic causes.
Best of luck to you!
Duke
The radiation pattern of the woofer is quite narrow in the crossover region, while the radiation pattern of the tweeter is very wide. In fact, for equal on-axis sound pressure levels, the tweeter can be putting out as much as 18 dB more energy into the reverberant field. Now the more reflective the room and/or the farther back the listening position, the more the spectral balance of the reverberant sound will influence the perceived tonal balance. And this extra lower treble energy is right smack in the region that would make female vocals tend to sound harsh.
Just to test this theory out, you might try nearfield listening; that is, listening at a distance of 5 feet or less from the drivers. If the tonal balance is better at such close range, that indicates the first-arrival (on-axis) sound has a much smoother tonal balance than the reverberant (off-axis) sound.
It's also possible that the pillows you have stacked against the wall make any lower treble emphasis stand out even a little more, if the pillows are primarily absorptive at higher frequencies. I know nothing about the absorptive properties of pillows so this is sheer speculation on my part.
If an off-axis energy excess in the lower treble region is the root problem, in my opinion the solution is loudspeakers that have a more uniform radiation pattern. It is very hard to target a specific frequency region with absorptive room treatment; absorption tends to work better at high frequencies than at lower ones, so it's very hard to absorb lower treble energy without over-absorbing the upper treble energy.
You may also want to check the room for slap-echo if you haven't already, as that can be a source of "zing". Clap your hands and see if it "zings". If you have slap-echo, it will be worst in the region where the radiation pattern is widest - that is, in that lower treble region. In this case diffusion or (if necessary) absorption on one of the two offending bare wall surfaces should take care of it. Keep adjusting the area treated, and/or increasing the area treated, until the zing is gone.
Of course it's possible that your zing may have another cause, but these are two possible acoustic causes.
Best of luck to you!
Duke