How to diagnose the need for room treatment?

Shadrone/Almarg - Good point about beaming in HF and the effect of tinkering with toe-in. But with speakers 11 ft away, and with only a six ft spread, you really are not that far off axis to begin with.

Shadrone, "The bass response is superb...". Obviously I agree, but let me say that I never thought it was suspicious. It actually resembled my bass frequencies before I tweeked the set up a bit (without using any acoustic crutches, which I still do not need). For fun, and for illustration of the benefits of position tweaking for Lewinskih.

My set up is as follows, in a 13.5x19.5x9 ft room with the speakers 58" from the wall behind them, 9' apart and the listening spot (ear location) at either 52" or 36" from the back wall.

........52"....36"
1000 0db db0
200hz 0db 0 db
160 -1db 0 db
125 +2db +3db
100 +1db -2db
80 0db -2db
60 -2db -1db
50 -5db -4db
40 -4db -3db
32 +1db +4db

One might think that the bass response at 36 inches would be better because it is smoother and it has some beneficial (I think) boost at 32hz, like the poster. But to my ears, any linearity one might loose, the gain in imaging by moving the listening position forward 16 inches was huge.

Shadrone, I want to thank you for bringing to my attention something (some time ago in another post) about the creation of a null on the center line of the room. I've since moved my listening position and speakers off center line and it has helped in getting a more balanced frequency response whereas nulls had previously been a problem.

IMHO, of course, just a mid-day stream of (un)consciousness. :-)

Nice.

Newbee: thanks for sharing your experience in your room. Your freq response does resemble indeed the shape of mine!BTW, how far is the listening position from the speakers?

Al: the speakers are indeed facing straight ahead. I gather beaming refers to high freq, right? Shadorne's [very interesting] explanation seems to suggest beaming in the mids. I have no clue what the dispersion of the mids driver is. Anyway, as Newbee said, at 11 ft away it would seem dispersion would be wide enough, right?

Bottom line, what I'm taking away is:
a) frequency response looks "good enough". No need to get into bass traps, resonators, diffusors, etc.
b) imaging is likely to be improved by moving speakers further apart (will try it for fun)
c) playing with speaker location might improve things some, particularly if they are exciting a room mode

Are these fair takeaways?

Thank you!!

Re distance - 10 ft from the plane of the speakers (10 1/2' from each speaker itself).

Re takaways - IMHO, yes.

Al: the speakers are indeed facing straight ahead. I gather beaming refers to high freq, right? Shadorne's [very interesting] explanation seems to suggest beaming in the mids. I have no clue what the dispersion of the mids driver is. Anyway, as Newbee said, at 11 ft away it would seem dispersion would be wide enough, right?

My understanding is that a driver will tend to beam as its diameter approaches or exceeds the wavelength of the sound it is radiating. According to a quick calculation I did, the one inch diameter of your dome tweeter corresponds roughly to the wavelength of a 12 kHz note. So at or near that frequency, and higher, it could be expected that the tweeter's dispersion would narrow considerably, and progressively with higher frequency.

The speaker is spec'd for +/- 30 degrees dispersion, which your listening position clearly satisfies, but we have no way of knowing how rigorously that spec was defined, e.g., if it was intended to cover all frequencies up to 20kHz.

In principle, a similar concern could exist with respect to the mid-range driver, given its 6 inch diameter and 4kHz upper crossover frequency. But I would have higher confidence that the manufacturer's spec for dispersion would be accurate for the mid-range frequencies, than for say 15 to 20kHz which most people can't hear anyway.

So that is the background on why I raised the question, but I think that Shadorne's good response pretty much puts the issue to bed.

Regards,
-- Al

Al,

That is roughly correct but beaming starts a little earlier. If you look at figure 3 you will see that the prototypical 6" woofer and combined midrange should not really be used above 1.8 Khz - like was done in the famous Energy Pro 22 speaker.

So why do we see so many speakers with 6 inch woofer/mids and a tweeter with a crossover much higher than 2 Khz?

Cost is the answer - unfortunately few tweeters can handle SPL requirements at that low crossover point - not without distortion and risk of failure. However to avoid having to add another driver (increased cost/complexity) the designers make do with beaming in the midrange...odd really in what is ostensibly an audiophile design and given we have known about the physics of loudspeakers for donkeys years and considering this frequency region is where our hearing is the most acute and discerning.