Question on "Q" settings

Posted by: Brad225

Question on "Q" settings - 01/14/06 05:24 PM

I have started setting up my new LFM-1's and
SMS-1 today. After checking the room with the sms-1 mike (1 sub setting in sweet spot then in next most likely seating position)I was surprised that the 2 locations with the flattest response before equalization were in corners at the back of the room. The front corners created huge peaks and valleys. The side walls were even worse. After moving the sub to their back corners I ran the EQ program and had a very large peaks ( 4db above the + or - 3 db over all ) in frequency range of 25-35 Hz. I was able to bring this peak down to make a flat response + or - 3db but I had to make some drastic adjustments. I am concerned with the frequency so close the low Q I had to use to widen the octave range that the over lap might be worse than the the peak. Here is what the settings are for the 2 sliders in this area.

L -13.0
F 28
Q 2.0

L -13.0
F 32
Q 0.3

The sliders either side of the above in case it would make a difference are

L +3.0
F 20
Q 0.9

L -3.0
F 36
Q 5.6

I have a basic understanding how all of this works but much of it makes my eyes glaze over. I realize learning a lot of this is reading and trying to see what works. Any suggestion would be appreciated. If you can explain as simple as possible that would help too.

Thanks again
Brad
Posted by: gonk

Re: Question on "Q" settings - 01/15/06 01:23 PM

If you are pulling down a peak, I wouldn't worry much about the Q - my understanding is that the only case to be cautious about is when you are applying boost to the signal, and in your case the only EQ channel that you are applying any increase to is the 20Hz EQ, which is 8Hz away from the next slider. Granted, the Q on that channel is pretty low (so it affects a wide area), but the next EQ is also carrying a relatively low Q and is getting pulled down 13dB.

The only thing I might suggest would be to play a bit more with the 20Hz slider - it is at the point where the LFM-1's are starting to roll off naturally, so if your response curve starts to dip around here it isn't necessarily a problem.
Posted by: Brad225

Re: Question on "Q" settings - 01/16/06 09:42 AM

I started over with my set up. I went much more methodically thru it. I tried crossover points of 40,60,80,100 & 120 with both large and small for front speakers, small for center and surround. Each time switching the phase from 0-180 in 15deg steps with polarity + then polarity -. On one of the passes thru I decided to play with the phase on the 2 LFM-1s. I switched the phase on one of them to 180 from 0 and it did very little with the 25-35 htz peak I mentioned previously. I reset that sub to 0 and went to the other sub and switched it to 180. I just stood and stared, it had flattened the whole peak to the 80db level I had set for all speakers before the test. At that point I finished all settings that way and went back and redid the previous settings.
The settings I ended up with were mains large all others small and a crossover of 100 in 990. In the SMS-1 O phase, + polarity, (subsonic filter defaults to 21Hz and 48db/octave as Gonk suggested in his review/setup of his SMS-1).
The second best set up was at same speaker and sub settings but crossover of 120, phase 90deg and polarity + .
I was very interesting to watch the frequency curves change as adjustments were made. It helped understand how all the settings affect what you hear.
Someone in one of the threads mentioned taking a picture of the best curves on the OSD with a digital camera. This made It so much easier to compare which settings to start with.
My final curve before starting to make adjustments was + or - 3db which amazed me and obviously made further adjustments much easier.
I had printed Gonk's review/set up with his approach to the SMS-1 and It made the set up much smoother. I would highly recommend having this printed out to anyone installing the SMS-1 in their system.
I had very little time to listen last night but the higher crossover point and flat adjustment seemed to create one large sound. I really thought my speakers blended well with surround applied but the transition was quite dramatic.
Posted by: gonk

Re: Question on "Q" settings - 01/16/06 10:19 AM

Cool! Glad to hear you got it dialed in so nicely.