[2gumby2]

I will be attending RMAF this October and I am planning to build a DIY speaker project after the show. RMAF seems to be a good venue to hear various speaker designs. I was seriously considering the Clearwave Audio Design "Tombstone" kit or the Selah Audio "SS3DP" kit.  Both of these are open baffle designs with very nice components. However, I've been reading a little recently about some of the problems of dipole designs. The articles mention out-of-phase energy problems and that, in general, they are extremely sensitive to placement. Obviously, these types of designs have some following so I am interested in learning more about the Pros and Cons of these designs. I thought this forum might be a good place to inquire. A non OB design that I am also considering is the Selah Audio RC5 kit.

[iON]

"Extremely sensitive to placement" is not my experience of dipoles. Dipoles of course have out-of-phase effects, that's basically what causes the characteristic Dipole figure-of-an-eight pattern. I dont really consider it a problem though.. but rather a nice way to reduce early reflections from side surfaces.

Cheers,
J

[hurdy_gurdyman]

In about six years of OB use I haven't found a really bad place to put OB's. They seem to sound good almost anywhere. Of course some places are better than others... aa

Dave

[Wind Chaser]

I'm not big on technical explanations... specifications... or even other people's opinions for that matter...  Not that any of those things don't matter, but to me, ultimately it's what the ears hear and what sounds "right".

To get the best performance from any loudspeaker, careful placement is required.  It shouldn't be a haphazard shoot from the hip effort.  From what I've seen over the years, it seems a lot of folks don't put too much effort in positioning their speakers.  For the most part they place them wherever they happen to look good in the room relative to where the furniture is!

The better the speaker, the more critical the placement.  In like manner you can't explore the potential of driving a Bugatti Veyron down a busy city street!  With high performance speakers, certain conditions have to be met or you're just plodding along with the crowd.

[Dmason]

I am a hardened OB listener, have been for some time now, and have successfully designed, built and sold my own OB design. All I can say is that the benefits far outweigh any drawbacks, and considering how well the music is served, I would say little about any drawbacks on the issue. I also agree that this notion of placement sensitivity is alot of smoke. I have been through so many, and NEVER have I found placement much of an issue at all, just, as Dave Leonard says, some positions are better than others. In fact, it would seem to me that placement issues are in the realm of the box speaker, where placement is ultra critical. Dave, perhaps you recall when I wrote you almost in a state of shock as to just HOW good those Eminence coaxials sounded stuck on some plywood baffles. So if you are interested in knowing why there is a "following," one only needs to listen. It is now going around, for example, that the best Lowther speaker is an open baffle one. Lowthers and guitar speakers. Best of show. Likely alot of people attribute that sound to a given speaker design, however I believe the sound they are attracted to is in fact the sound of unencumbered drivers, operating optimally, with static air masses on both sides of the diaphragm.

Recently I was listening to a pair of very, very expensive speakers in a high end "salon," enjoying being condescended to by the snarky, pseudointellectual drivel of the guy trying to insult me into spending large dollars on sound, and lecturing me on absolutes, which to a man of science such as myself just comes off as hogwash, and my overall impression of these speakers was that box speakers are inherently compromised. I swear I could hear the cabinet, the inside of the cabinet, all competing with the output of the drivers. It seems to me that the highest performance driver is the one completely unloaded, ergo, open baffle. My Delco Pioneer car ovals on plywood in the garage sound highly musical. The car speakers are open baffle speakers.

I have also discovered another phenomenon relating to OBeez, and that is that tube amps sound even better when powering open baffle speakers. I have no idea whether this isnt psychosomatic, but I do notice that the whole thermionic gestalt is far more ...enjoyable.... when used with open baffle speakers. I mentioned this weird little anomaly to Darrel Hawthorne and he agreed. Maybe others can comment, but it seems as though tube amps and OB speakers were made for each other. And when you are into that, it doesnt get much better. This is why I dont go to audio shows anymore. Not much there that interests me. In my own opinion, the very best sound systems use tube amplifiers and open baffle speakers, which to me means that one doesnt need to spend much money to have the best sounding stereo available.

Lastly, there are several commercial designs available right here on AC.  What I do not understand is your query is about open baffle speakers, on the open baffle forum, and you conclude by stating you are interested in some box kit design. This makes no sense to me at all. If you did get the Selah kit, you could optimize its sound by mounting the components on an open baffle.

[jeffreybehr]

2, the one overwhelming charactersitic of OBs that I LOVE is their spaciousness.  ALL front-firing-only speakers sound very forward to me.  If you love poppish music in its hundreds of versions, I think you'll be happier with the in-your-face sound of front-firing speakers.  If you love classical and/or other kinds of acoustically played music, and if you love hearing the soundstage of an orchestra extending dozens of feet behind the plane of the speakers, OBs are for you.

Because I didn't know any better, I started my recent DIY project with a desire to build an OB, line-array system and a carton of Sonic Craft 6-1/2" bass/MR drivers.  Those systems fairly quickly evolved into the 3rd prototype...


I've just this summer selected better tweeters for the finished versions which I'll be building soon.  Each will have 11 of those fabulous B/MR drivers, 8 B-G Neo8-PDR tweeters, and no woofers.  The system has been tri- or biamped for maybe a year; I use a dbx DriveRackPA and Music Reference EM7-series flea-powered SET poweramps, 10 WPC on the B/MR and 5WPC on the treble.


I'm THRILLED with the sound I'm getting!

[scorpion]

In my opinion it is not placement that is really critical, at least for highbass-midrange-tweeter OBs, but rather room characteristics that matter. An OB will not play at its best in too a dry or damped room, some liveliness must exist. I cannot resist a picture also:



This is 'Volks-OB' MKII playing in comparison with my Magnepan 1.6, guess which one most people prefer ? 
I brougth the 'Volks-OB' to DIY-shows in Stockholm and Gothenburg. Stockholm was a big success, Gotenburg less so just because of the room they played in there.

/Erling

[Michael V]

I agree 100% with Wind Chaser

[2gumby2]

I appreciate all of the great advice and input you've provided. I'll expand a little more on my interest in OB designs. I heard the Selah Audio "3D" OB speakers at RMAF in 2006 and thought they were some of the best sounding speakers of the show. This experience piqued my interest in OB designs. I also heard the GR-Research OB7 Plus, but it did not stand out from any other good speakers that I heard there. I have to admit that I am drawn to the stunning appearance of the Clearwave Audio Design "Tombstone" OB speaker. I know the sound is what really matters, but those are some very nice looking speakers. I don't know a lot about the OB concept so I value your insight and opinions. Your passion for OB is obvious in your responses.

I mentioned the Selah Audio RC5 "Box" speaker in my initial post only because it is one of the options I am considering. I have an open mind so I'm not set on anything yet, just trying to learn more and seek opinions from those that are drawn to OB designs. I'm sure I'll meet some folks at RMAF this year that wouldn't mind discussing the OB vs. box designs.

I will be using an Audio by Van Alstine Ultra FET Valve 550 amplifier and Bel Canto PRe2/P preamp so this should be plenty of power in most cases I think.

[opnly bafld]

I also heard the GR-Research OB7 Plus, but it did not stand out from any other good speakers that I heard there.

IIRC this was the cabinet design with box on bottom and box on top with OB between like the picture on the GR "kits" webpage.
I agree, IMO it did not have an OB sound to it at all (sounded like a very good box speaker), I'm not sure why. 

Lin

[panomaniac]

Well.....
On the flip side, I DO find OBs to be sensitive to placement, at least in my room.
Placed about 1 meter from the back wall is the worst for my rig, as this gives a big mid-bass peak - and the room dimensions reinforce it.  Better to be closer or farther.  The effect is not subtle.  Other placements yield other results.

Toe-in also makes a difference, but that should be true of box or horn speakers, too.

There should be some fun OB stuff at RMAF this year.  It's a good idea to wait until after you've heard the current crop.

[Mr Content]

If you are willing to some sort of treatment to the rear wall, your have more of a chance getting the speakers to sound just right where you want to put them. You can actually tune the rear wave to the placment with the right amount and sort of treatment. I have a very heavy set of drapes behind my speakers, opening and closing the drapes provides a lot of tuning.

Mr C

[nodiak]

I agree with using absorption and/or diffusion behind the ob's to tune them. Mine are in a narrowish room at 12' wide (26' long). They're 6' out from wall behind them, but only 2.5' from sidewalls. There are full length 5" thick bass traps straddling the corners that also absorb the ob's rear wave. Can use diffusion in front of this for a more spacious sound. Also toeing them in more changes the rear waves effect as it goes off the side walls. Diffusion in the room helps keep the ob spaciousness. Adjusting woofer height to floor very helpful for tuning bass to room.
Have learned major adjustments can be done with just physical placement and room treatment.
Don

[2gumby2]

I'm glad the topic of room treatments has come up as I was wondering about the interaction of OBs with treatments. Due to my room furniture arrangements and WAF, the speakers would probably end up being about two feet from the rear wall on the short side of a room 16' X 26', opening to a kitchen and hallway on the long side. I've gotten by pretty well using my box speakers without treatments, but wasn't sure about OBs.

[Rudolf]

Due to my room furniture arrangements and WAF, the speakers would probably end up being about two feet from the rear wall on the short side of a room 16' X 26' ...

2gumby2
I am not sure you know what that implicates. For a 50x100cm baffle with a specific woofer at the bottom the following simulation diagram (courtesy of MJKs OB worksheets at www.quarter-wave.com) compares different wall distances WRT to the performance without any walls - floor only (red):



A front wall distance of 1 m (blue) will enhance the SPL level from 35 Hz up - exactly where it is most helpful for that driver and baffle size. With a distance of 50 cm (green) you loose 5 dB at 35 Hz. If you can´t pull your OBs 1 m into the room, you should at least try to put them at a 45° angle (or even more) WRT the walls and probably each 1 m from the adjacent side wall. That way the "back wave" will see more distance to the front wall.

I would strongly recommend to play with toe-in-angles and wall distances first before trying room treatments. You don´t take the effort to build a speaker with dipole radiation pattern and not use that in the end - don´t you?

[hurdy_gurdyman]

I would strongly recommend to play with toe-in-angles and wall distances first before trying room treatments. You don´t take the effort to build a speaker with dipole radiation pattern and not use that in the end - don´t you?

Yes, we want to use that rear wave. I use diffusion for the rear wave, but avoid absorption. Absorption kills the lively sound and makes things sound more like a boxed speaker sound. That great OB sound-stage is caused by using the rear energy. Diffusion scatters it but still uses it, giving the effect of a bigger room. I put bookcases filled with varying sized books, CD's and videos behind my baffles. Works great!

Dave

[Danny Richie]

IIRC this was the cabinet design with box on bottom and box on top with OB between like the picture on the GR "kits" webpage.
I agree, IMO it did not have an OB sound to it at all (sounded like a very good box speaker), I'm not sure why.

That must have been back in 2006.

The slight lack of transparency (that they typically have ) in that room may have had more to do with how heavy the wall and corners behind the speakers were treated to control the really low bass response created by the powered 12" woofers.



I will have a couple of over the top open baffle designs there this year. Don't miss them.

[2gumby2]

Good advice on speaker placement and treatments. This is valuable information. I may be able to get 1M from the back wall, but it will be a challenge with the furniture placement and WAF.