dipole measurements

[Marcus DiBenedetto]

Hello all, I just installed some brand new dipole (open baffle) speakers. A fellow owner (on another forum) said REW measurements for dipoles are tricky. Asking here before I take measurements if there is anything I should know that's different.

Thanks
Marcus

 

[Sonnie]

Tricky? Never heard of such really. I've seen all kinds of measurements from online review professional with dipoles that are no different than any other speaker. Naturally in a smaller room like we have in our homes the actual measurement at the listening position is likely not going to be exactly what we hear (Toole and others), but that is any speaker for the area above the transition frequency. We can easily fix up to about 4x the transition frequency... usually 500-600Hz with no issues and what we measure there should be fairly accurate. When we get above that area, the measurements will include the reflections.

 

[ddude003]

The "tricky"part is speaker placement... With a dipole it needs to be far enough into the room from the front wall to get the reflected energy to align with the direct energy... There should not be much of an issue with first reflection point as there should be little energy going going towards the side walls...

You might take a look at the Cardas room placement calculator to see what they think is the difference is between monopole verses dipole placement... http://www.cardas.com/room_setup_calculators.php

As for REW measurements, what you hear and what REW plots may differ a bit... Trust your ears...

 

[Marcus DiBenedetto]

Thank you! I will proceed with REW measurements. Clayton Shaw (speaker designer) recommends 3 feet from front wall. I'm set at 4.5 feet. Cardas recommends a bit over 7 feet (assuming what they mean by rear wall is actually the front wall). I can't do 7 feet and they sound excellent at 4.5 feet. I'm set at 2 feet from side wall. Thanks for confirmation on dipole cancellation towards side walls.

Thanks again!
Marcus

 

[Sonnie]

Definitely on out into the room. I started out with Cardas recommended and between Wayne, Dennis and myself, we moved them slightly... a few inches farther out into the room.

Here are the options based on your room shape: http://www.cardas.com/room_setup_main.php

"Panel or dipole speakers such as Apogees and Magnepans cancel their side waves, so a formula of .618 x the ceiling height can be used for determining placement from the rear wall. Most box speakers radiate low frequencies in all directions thus a formula that places the speaker to rear wall distance at 1.618 the side wall distance should be used. "

Yes... "rear" means what I call "front" with Cardas.

 

[Marcus DiBenedetto]

@Sonnie Thank you.

 

[ddude003]

Seven feet does seem a little excessive although I don't know the dimensions of your room... Even less than an inch movement of your speaker placement can sometimes make a big difference in soundstage and imaging so it does pay to experiment with various distances from back wall and side walls as well as toe-in... If your speakers have adjustable "feet" you might also see what tilting them back a touch might do...

 

[Marcus DiBenedetto]

@ddude003 I agree. I've had my new speakers on sliders since they arrived. Of course, my wife thinks I'm nuts moving them around all the time. The listening area is 14 feet wide. Ceiling is vaulted with an average height of 12 feet. Length is 15 feet to MLP but the actual length of the room is 30 feet (part of a great room). Right now, I am happy with the speakers 4.5 feet out from the front wall. My wife prefers 3 feet from the front wall for aesthetics. The depth of the soundstage shrinks at 3 feet. Not terrible but not preferred. At the moment, I am keeping the speakers where they are and just listening to music. I plan on running REW and will adjust based on results.

Marcus

 

[ddude003]

Well @Marcus DiBenedetto, I won't presume to argue with your wife... I noticed a photo of your setup in another thread, it looks like some wide band absorbers at the wall directly behind your Dipoles... Have you tried moving the absorbers around allowing for a little more or less reflective energy? As with speakers, absorber placement by even a few inches can make a big difference with Dipoles...

 

[Marcus DiBenedetto]

@ddude003 The greatest impact is moving the speakers farther from or closer to the front wall. The soundstage grows (farther) or shrinks (closer) in depth. The second most impactful move is toe-in. Sidewall distance does not seem to have much impact. Of course, dipoles cancel side output so maybe it's to be expected. The absorber/diffusors are GIK 6 inch Alpha series with 2 dimensional scattering. I had them horizontal (for old bookshelves) and now vertical for the new speakers. Yesterday, I moved them out entirely because I had an electrician over to do some work. I just did not hear a huge difference in any situation. But, many dipole owners swear by diffusors on the front wall. I own them so I will use them. Unexpectedly, my wife told me they have to go back because they cut the sound way down traveling through the front wall in to the master bedroom. Once I get everything back in place, I will be more diligent in absorber/diffusor positioning. And I agree, even a few inches can make a difference.

Marcus

 

[Sonnie]

I know Toole and Linkwitz both are in favor of diffusion on the front wall for dipoles. I built those massive diffusion panels, as well as absorption panels, so that I could swap them out and see what I prefer with my MartinLogan 15A's, but I'm having a hard time figuring out which I like the best... lol. I want to say the absorption panels seem to make imaging a bit more refined, but there is no way to A/B them instantaneously, so it's hard to say for sure. I'll let Wayne and Dennis tell me what they think when they get here next month.

 

[Marcus DiBenedetto]

@Sonnie Awesome. Thank you so much for being a part of this conversation! I super appreciate your viewpoint.

Marcus