Deqx pre8

By placing the measurement microphone about six-inches directly in front of each driver to be measured should minimize its first reflection back to the microphone.  Of course the best, but usually not practical solution would be to place the speakers to be measured either outdoors or in a very large indoor space short of in an anechoic chamber.  In my case with the Apogee FRs, the mid-range and tweeter ribbons are crossed over passively and are treated as one driver by the Pre-8.  For that reason, I have to set the measurement microphone directly between the mid-range and tweeter ribbons about 16- to 18-inches away from the area in front of the two ribbons.  For consistency, I also measure the bass panels from the same distance as well.  Unfortunately, moving the measurement mic away from the driver, such as in my case, is not ideal since by doing this allows more time for the first reflection to be picked-up by the measurement microphone. 

During the ownership of four DEQXs over the last 12 years, I have found that trying to create a quasi-anechoic environment with easy or economically to obtain items is almost impossible.  A specific material may be great at absorbing energy at some specific frequency but actually reflects sound quite efficiency at other frequencies.  I have always taken my best measurements when the measurement mic as close to the drivers a practical.  Again, about six-inches seems to work best for conventional come and small drivers, but you may need to back away  a little when measuring ESL, magnetic planer, ribbons, etc.

For the "trim" adjustment, as I understand it, this setting is used to truncate the lowest frequency of speaker correction.  Trim is set so the DEQX will not correct frequencies that occur after the first reflection.  You can determine the first reflection after you complete the "Measure Drivers": task by changing the graphical view to.from Frequency Response to Impulse Response and the expand the X-axis noting where there is a small second impulse after the decay of the initial impulse.  At this point you can locate your trim slider to position it immediately before the first reflection point. This will create the "perfect" trim or truncation.  That being said, there is always some wiggle room either up or down test for what sounds best.  Moving the trim slider to the right past the reflection point can make the bass woolly; to the left the bass can get thin.  What’s nice is that you don’t need to take a new measurement each time you want to change the trim point, or any other setting for that matter.  Just reload the existing left- or right-driver measurement file, make the adjustment and save it as a different file name.

As for attenuation/boost, I too am at a loss on how to use these adjustments. I think that attenuation/boost controls the amplitude, up and down, limits of speaker correction.   I played around with these settings a little and the sound always got worse as I moved away from default.   I also played with smoothing a little but didn’t find any real difference - but I only moved it down to 9 from 10.  So that’s not a real test.

Right now, I've created my best profiles with all the settings in the default positions, except for trim.

I think it would be great if DEQX would document all of these setting in detail.  It would sure be a great help to the Gen 4 community..

I agree with measuring drivers up close is a good practice. Last, (3rd), measurement I’ve been doing at listening position. 2nd measurement I’ve been doing about 1 meter, assuming this is only for time alignment, not sure if this is best.  
trim feature, I tend to get a reflected “bump” at 7 ms.  Would we assume .007 is 7ms? 

I’m also wondering about the PEQ frequency response.  I’m under the belief DEQX creates a flat response through its automatic EQ. Not sure what I’m looking at. Also it doesn’t match the FR I see from REW.

Unit sounds great, would love a little more manual control of crossovers, but overall it’s great.

Yes, 0.007 is 7ms which really isn’t all that bad. It’s bouncing back from the nearest surface - wall, floor, ceiling, etc  Move your trim pointer immediately before the bump and go from there.  Later on, you can reload that same driver file without taking another measurement and move the trim pointer to the right may to 10 to 12ms, save to a different file name and continue with steps 2 and 3 then give that a try.

In v1.4.0 the frequency response heard by the measurement microphone in step 3 in now superimposed on to the the PEQ screen. Whow!  Like you, it’s not what I expected!  It looks like a profile of the Smoky Mountains.  I thought the Pre-8 would flatten it out for the most part - and without any PEQ the profile’s sound left a lot to be desired.  I haven’t pulled out my XLR-phantom-power-to-USB Roland Rubix22 to connect my Earthworks M23R to my REW laptop yet to check it, but you do need to use the same measurement mic placed in the same exact position to do a direct comparison.  I may try it soon.

Well anyway with PEQ, I can flatten the response a bit - quite a bit - returning great sounding results.

In step 2, "Create a Speaker",  I’m finding that somewhere about 40 to 60% of the distance on-axis to the listening position works best for me.  What I found was that if my measurement mic was set up just slightly right or slightly left I would get vastly different relative distance measurements between the bass and the MRT section. The bass panel would lag the MRT section anywhere  between 0 to over 100 mm.  I’m not sure if the following way is correct, but after much trial and error, measuring each side accurately as possible with the measurement mic set the same distance and pointing at the same exact place on both the right and left speakers, I found that if one side has a very low relative distance number, say under 30mm and the other is much higher, I will ultimately manually set the speaker with the higher distance to match the speaker with the lower distance.  Right now, I’m listening to a profile with both speakers’ bass panels set to 27mm and is among the best sounding profile created to date, BUT I still think that there is still a better sounding profile to be had either with another software update or me finding that ah-ha moment with taking measurements - I thinking probably both now. 

Subwoofers are another story.  You can see some very unrealistic distance numbers here - especially if you has multiple subs.  In the past Alan said to take a physical measurement of the distance of your subs to you main speakers then add 0.6m then override the sub relative distance with this new number.  This procedure really doesn’t work if you have multiple subs in different locations. For this reason you can only input your measurements as a WAG (wild ass guess).  I did notice however that the relative distances returned in step 2 for my subs appear to be somewhat realistic now in v 1.4.0, and for that reason I went with that.  The bass seems to be quite good and tightly integrated.

There is not much to say when doing step three, "Creating a System".  Set the measurement microphone where your head would be at your listening position and take the measurements.  If all goes well and you sit down for that first listen, you either say OMG that sound unbelievably great OR that’s just down right awful!

The first thing I do now after I create a new profile is listen to track 2 of the Sheffield Labs XLO Test CD to quickly make sure that everything is totally in phase.  I do this because there was a bug in the software (version 1.37.21) where the final profile had the right and left speaker drivers out-of-phase more often than not. Alan said that they were aware of the issue and had me jump on their development server to test the fix.  I was please to find that all the test profile that i created were totally in phase; however, I did manage to create a couple of profiles recently under v1.4.0 that were out of phase.  For that reason, I just deleted everything and started over again and all profiles created since has been in phase.  I’m not totally sure but when it happens during the calibration process, but I think the out-of-phase situation occurs during step 2.

Bottom line is that there is a lot of time and work involved in properly implementing a four-, six-, or eight-channel BETA DEQX Pre-8.  It’s not for the impatient.  I’ve done hours of work just to take one listen and then delete everything and start all over again - and moreover with every new software release you will need to do it all over again. But so far, like you I’m sure, I think that is the most technologically advanced piece of audio equipment ever produced.  It’s still being developed and I always look forwarded to next software update and ultimately, the final product.