Deqx pre8

After some offline discussions with mijostyn about the difficulties in taking accurate measurements of dipolar speakers such a the Soundlabs that he has and the Apogees that I have, as well as any other dipolar speaker for that matter, I found that his experience and advice in this area proved to be correct and very helpful.

>> YOU MUST BLOCK THE REAR WAVE OF A DIPOLE SPEAKER FROM REFLECTING FROM THE WALL BEHIND IT IN BOTH STEP 1 AND STEP 2. <<. Otherwise, you will get comb filtering which produces all sorts of undesirable side effects. Even though your graphic results may not show what appears to a traditional repeating comb "tooth" pattern over a wide frequency band, you will probably immediately notice a problem in step 2 when the driver distances appear. Your first clue is when you see unrealistic relative distances between the drivers in your main speakers. I have found that these driver distances should be within the hundredths-of-a-meter without manual adjustment. I’ve also found that manual adjustment won’t fix this problem either. If you take these unrealistic defaults you will most likely have very noticeable phase issues. If you manually correct the distances, you may correct the noticeable phase issues, but it will still not sound right. This problem may be because there are driver phase/group-delay correction issues that cannot be corrected by manual relative driver-distance manipulations alone. Remote subwoofers are a different story and may need manual relative distance intervention. I’m still looking into the best way to deal with remote subs. Any suggestions in this area are certainly welcome.

I my case I was able to effectively block the rear sound wave from my Apogees with a heavy sound-absorbent blanket similar to what you would find in under-hood sound insulation in a automobile but of higher density. Please don;t ask exactly what it is or where I got it, it just appeared in garage one day, but any heavy-weight sound absorbent material such as a heavy quilt should work just as well. Just be sure to position the material in such a way in order to cover ALL of the rear of your dipole speaker. As I understand from our conversations, due to the exceptional acoustic transparency of the Solundlabs and probably most other ESL speakers as well, mijostyn informs me that simply blocking the rear of those speakers with a quilt was not enough and for this reason, he is building a Sallie for his unique situation.

Finally, be sure to remove the rear covering before starting step 3 since in this step acoustic properties of your entire room are quantified from your listening position.

Here a tip to help minimize aggravation when measuring speakers.  

If it's going to take a bit of time to reposition blankets, wall coverings, sofa cushions, furniture, etc, between measuring your left and right speakers in step 1, consider LOGGING OUT while moving these items to set up for measuring second speaker then log back in just before your start to take measurements again.   What I have found is that after taking so much time to move and reposition these items, the Security Token would expire right in the middle taking driver measurements requiring you to start all over again on that speaker.  This is especially aggravating when you have completed your main speaker and the token expires after you move to its associated remote subwoofer.

Welp, I'm going to throw out what I know may be a terrible idea.  Sorry.

What about taking a cue from ground-plane measurements?  Often used for subwoofers.  The idea is to put the subwoofer up against the floor so there is no reflection point.  The microphone is also nearly at floor level. 

What I am thinking you might want to do instead is to put your planars up against a wall and attempt the same thing? 

Sorry I'm not familiar enough with DEQX to help more.

Actually that sounds like it may be a great idea for measuring the subs and I'm going to be thinking about doing just that, but unfortunately that's not going to work, at least in my case, for a pair of 81-inch high 300lb (each) speakers.  Even a couple of inches to the right/left or forward/back becomes a quite a chore.  Thanks, every idea helps!

The problem that I run into during the integration of a pair of stereo subwoofers using the Pre-8 is that all drivers’ relative sound levels, for both the main speakers and subs, are measured during the first step. Essentially, you place the measurement mic very close to each driver for left channels then repeat the process for the right. After all the driver measurements are collected for the left channels, graphic results are displayed of the response curve for each driver relative to each other. This in my case includes the left subwoofer sitting about five-feet behind the left main speaker and the same is on the right side as well. This seems to work well for drivers on, or nearly on the same plane, but for the subwoofer that I just took a near-field measurement, five feet (1.5m) behind my main speaker, is not going to have the same relative sound-level when measured at the plane of the main speaker.

In DEQX-Cal, used for legacy DEQX processors, you could match the level of your subwoofer to your main speakers by matching the subwoofer curve amplitude to the main speaker’s curve as measured from the sweet spot, but this was a manual process. You could also match impulse response of your subs to each other then both to the impulse response to your main speakers in order to set the correct delay. It appears now that subwoofer time alignment as well as time alignment of all drivers is performed automatically in step two with a provision to override (in distance).

But how could step two possibly set the subwoofer’s relative loudness when relative levels are set in step one and the subwoofer is substantially on different plane than the main speakers?

For me when I perform driver measurements in step one and close-mic my subs, the final outcome is low bass "lite".  As a kluge, which actually returned fairly good results, I made step-one measurements of the main speakers, in my case at 16" (40cm) then moved the mic along the same plane as I measured my main speakers to where the mic was directly in front of my sub and still on the same plane as my main speaker. This placed the measurement mic about 66" away from the front of the sub and I then took the measurement. I also limited the lower speaker correction (but not room correction) to 200Hz crossing over at 60Hz12dB/oct since the Apogee woofer panels go very low. The bass is pretty damn good now, but I know this couldn’t be best way.

Always open to suggestions.