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In Reply to: RE: Using REW with Maggies posted by computerman on October 10, 2015 at 09:00:13
Depends on how complicated your system is, what you're trying to do and how much time you're willing to spend. Measuring and listening should give you a better result.
To interpret measurements this might be helpful: Acoustical Measurement Standards for Two Channel Listening Rooms http://www.acousticfrontiers.com/room-acoustic-measurements-101/Speaker Placement (mains) - I did not use REW (or Magnepan's instructions) for placement of my 3.6s. I did use it to adjust and confirm speaker toe-in to get the proper high frequency roll-off. Warning. Slight changes in microphone placement yield wildly different responses at high frequencies due to their small wavelengths. Room impulse response measurements aren't that enlightening. RT60 times have more validity in auditoriums than small home listening rooms.
Speaker Placement (subs) - I have 2 passive subwoofer towers (5 x 10") and 1 active powered sub (Rythmik 15"). REW confirmed the extra sub provides useful frequency smoothing of response below 250 Hz even though all the subs crossover at 88Hz and a slope of 24dB/octave (see DSP). Good thing too as I had already bought them.
Powered Sub Adjustments - (gain, PEQ, delay, etc) - The Rythmik HP15 has enough options to make your head explode. REW's useful to fine tune a powered sub for fixing 2-3 dB room anomalies that can be very difficult to hear.
Setting Active Crossover Gain, Slopes & Qs - REW's indispensible for this. My system's active 3 way (Pass Labs). Changing slope changes frequency and phase. Although I emulate the Magnepan 3.6 passive XO, just adjusting gain for mains and subs, I get much better results measuring than by ear and it takes far less time. No I'm not deaf....
Room Treatments - While you can see frequency and decay (waterfall) results change with every addition and removal of a bass trap, you don't really need REW for this. If you're really lucky, like me, you can get good measurements that sound bad.
Room EQ with DSP - The REW "EQ" program goes through an iterative analysis that results in filters to add to your DSP unit to get a flat response and/or mirror your house curve, as well as optimize decay times. There is nothing intuitive here. Manually setting DSP filters can give strange results. REW can recommended combinations of boosts and cuts around a single frequency. Set REW for no finer than 1/6 octave or you'll end up with a LOT of filters. Although it would seem to make sense, I have found it is NOT productive to adjust each L&R speaker's response curve separately. One reason - you can't increase gain for FQ dips!
It took a lot of work, but here's where I ended up before I boosted the bass 2 dB more. Note that this is 1/6 Octave smoothing not 1/3rd!
Edits: 10/10/15 10/10/15 10/10/15Follow Ups:
This is a very helpful post. I am presently using a DCX2496 that hopefully will be modified, or I may end up getting rid of this in favor of a miniDSP product, and not sure which I would purchase. I have a mini-DSP 2x4 that I have done some experimenting with just to get familiar with their products. They seem quite versatile and a pretty good bang for the buck. I am using dual pre/pros in my setup. One is used as a "switcher" and the other one for output using the analog 8 inputs coming from the DCX, which gives me separate channels for each driver. I have attenuators on the inputs to better match the output of the DCX and that took care of any clipping I had. I know it is not the ideal XO and not so easy to tweak, but it is what I have for now. See my post http://www.audioasylum.com/cgi/vt.mpl?f=mug&m=216892 to better understand my setup.
My room placement is very limited, so I am hoping that with the application of room treatment, and tweaking of the DCX2496, I will be able to better optimize the sound. I have a UMIK-1 calibrated mic for use with REW. Thanks for posting the link to help with interpretation that looks to be very helpful as well.
Why the large drop off after 10 KHz? Both my 3.7i and biamped IIIa maintain a "normal" output up to 20 KHz (limit of measurement)?
More for others who are unfamiliar with this as I know you have used REW, the blue line is a house curve created to model the "optimum B&K listener response curve" in the other post. It's then best fit overlaid by the REW EQ program on the actual room measurement data (green line).If I toe the speakers in more, it would tilt the whole high frequency range up too much and music would sound overly bright. You'd think the pic below would sound just the opposite, too dull with my aging ears, but it really sounds just right to me.
Some of the roll-off is probably also due to my inability to exactly replicate the position where the microphone placement was when I originally positioned the speakers. As you know, it's a bitch to reposition the mic exactly.
Edits: 10/11/15
at listening position with very little speaker toe in. I could fix it but it sounds good as is as I don't have bat-like hearing. It gets close to mirroring this without sounding too bright.
Edits: 10/11/15
Yeah, despite all the technological advancements our ears remain the most important tool we have in our armamentarium. I found that cryo treatment, mainly sticking my head in the freezer for a couple of hours - my wife's suggestion - improves my acoustic sensitivity to the finer audiophilic nuances :).
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