Funnily enough, recently I've been doing A/B comparison of 2 very similar speakers. GR Research OB 5's and OB 7's. This pair here have the exact same tweeter network, the mid network in the OB 5's and OB 7's are normally identical, with only a difference in the woofer network due to the different configuration of that section. However, these OB 7's have an updated mid network as a result of testing in this new totally open baffle configuration that differs from the first models which had the open baffle top portion shrouded with a back and a top, with open sides. Both models will sport this new network, however, these OB 5's are awaiting the parts on order for them to be converted.
This is the sequence that I have found to be the best for listening comparisons. I set them up from left to right in this sequence, OB 5- OB 7 on the left side of the room, then OB 5- OB 7 on the right side of the room as well. That way you don't have one pair sitting inside another pair ( and therefore closer together than the other pair ). You also have the same first reflection point ratio to the side walls, albeit asymmetrical to the left/right speakers themselves. You simply shift your center position slightly going from one pair of speakers to the other.
I also leave a decent space in between the speakers so that you don't mess the baffle step of the speakers. I don't use a sub initially, but add it towards the end of the session, to see how the mains to sub integration differs in room.
The way I find best is to split music into categories, and listen for different things. For example, I will listen to one track specifically because of the drum track. I'm listening for detail in transients, timbre, impact,dynamics, depth, spatial location, and FR response and distortion.
I'll then pick tracks that feature instruments, and vocals that I know well, and go through the same sequence for both speakers. This is where I've been able to here very clearly the differences between 2 speakers.
I
highly recommend devising as rapid fire a method to do the change overs as possible. Having the dormant speakers in another room while you listen to the active pair is not a good idea IMO. I recommend the set up I mentioned before. If you can get a buddy to do the wiring change overs for you while you sit in the same spot, that is really helpful, and I would highly recommend that. Also have a remote that can cue, pause, etc ..is very important. (If your CDP has an A/B loop feature, that's a huge bonus).
I listen to short segments of sequences, looped a number of times, them pause, and change over. I can do this half a dozen times or more on every featured instrument.
I also sit back and listen to complete tracks and employ a more casual approach as well.
As far as the dormant speaker acting as a passive radiator, yes, the drivers are moving sympathetically. So will other things in your room, and act as passive radiators as well, including the walls. You can't possibly eliminate everything. I thought about that as well, so I would throw a heavy shipping blanket over the dormant speaker to minimize the sympathetically moving drivers affecting things. I did some A/B 'ing of the effects, and the effect was not really noticeable ( I'm in a large space, with no nasty first reflection points, and a really high [ 17'] ceiling, so YMMV).
The other thing I found was that you are best to listen with your eyes closed. With your eyes open, they are scanning as you are listening, and therefore, multi-tasking. Your perception of sounds is much better when your eyes are closed.
In the test I just finished doing, I was able to hear differences very, very clearly between these 2 very similar speakers. I probably spent between 10 and 12 hours total. And plan to do the same once I update the mid network in the OB 5's.
Cheers
