Open baffle speakers
Open baffle speakers design is the simplest , to get bass response similar to other design , like ported, the baffle size must be huge to avoid low frequency degradations . Tipical size the baffle width 10-20" got weak bass performance. I am wondering how open baffle speakers design became so popular ?
I don’t believe that Dalquist DQ10s really qualify as open backs. The woofer is in a separate sealed container (closed back). The lower midrange has a thick piece of padding that covers the back of the cone to remove any rear radiation/reflection. The two dome tweeters are sealed and the piezo is a sealed horn.
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The DQ10 was not an open baffle speaker in the purest sense. It was a speaker with numerous time aligned baffles. It was a beautiful sounding speaker that could not image. One has to be specific about what they are calling open baffle speakers. The are bipolar speakers, both sides radiating in phase and dipolar speakers, the sides radiating out of phase. Most open baffle speakers are dipoles and most are planar speakers of one sort or another, ESLs, Ribbons and Planar Magnetics. Trying to do this with multiple dynamic speakers has never worked well. This brings us to line source speakers. Line source speakers project sound more effectively than point source speakers. Acoustic power drops off at the cube of the distance with point sources, but at the square of the distance with line sources which is why you see them at large concerts. Due to their construction, planar speakers fall naturally into the line source category, with some irregularity. For a speaker to project as a line source it has to be longer than the wavelength of the lowest frequency it is to reproduce. For a free standing speaker to project 20 Hz as a line source it would have to be 60 feet long! There is one major caveat. If the line source terminates at a barriers, a walls, floors or ceilings it will maintain line source behavior down to 1 Hz. Dipolar line sources, like any dipole does not like making bass below 100 Hz. This is particularly true of full range dipoles like ESLs. They will do it, but it creates distortion with everything else the speaker is doing. Even if the speaker ends at barriers. typically the floor and the ceiling, it is best to cross over to subwoofers at 100 Hz, but it can not be any old subwoofer. In order to maintain balanced amplitude behavior with distance it has to be a line source subwoofer. Even two subwoofers will get lost under line source speakers. The major problem is most "line source" speakers really are not line sources. A speaker that is 6.5 feet tall in a room with 8 foot ceilings looses it's line source behavior under about 250 Hz. As you move away from these speakers they will become progressively brighter or tinny. Line source, dipole speakers have one huge advantage in residential size rooms. Because they do not radiate sound to the sides, up or down there is way less room interaction. Only the front wall is a problem and this can be easily dampened behind the speaker. Only Horn loaded speakers have dispersion controlled at this level. The OP is right to question the bass performance of "open baffle" speakers. The baffle has to be so large you enter the realm of infinite baffle loudspeakers. People including Linkwitz have tried it, tongue in cheek and they will provide the illusion of bass, but it is far from accurate. What most people are listening to under 100 Hz is a mess anyway. Don't believe me? Measure it for yourself.
DQ10s are not open baffle speakers. They are a bunch of separate, time aligned baffles mounted in a cage with mass insanity for a crossover. They could not image to save their lives. They hold a place in HiFi history next to Bose 901s.
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@mijostyn the wall behind the speakers is not supposed to be damped with the apogee speakers, which are dipole. You are the only person I have ever heard say this. |
@vetsc5 +1 The DQ10 is a remarkable design that 50 (!!!) years later can still compete with today's over-priced speakers. I have a nicely upgraded pair on custom stands. I find the bass adequate though a sub does help if playing pipe organ recordings. |
My woofer towers are H-frame open baffle with four servo-controlled 12" drivers. There is obviously cancellation at the lowest frequencies where the backwave wraps around, but the circuitry in the amp does an excellent job compensating for this. The measured response in my 29'x17'x8' room is not without some room interactions, but considerably less so than my previous conventional subs and is the deepest, tightest, and most natural sounding bass I've ever had in my system. To say that open baffle subs can't create excellent bass is hogwash. Yes, you need more power and more radiating area to compensate for the backwave cancellation, but if done properly the bass is superb. Open baffle speakers need some room to sound their best. Most of the manufacturers say 3ft to the wall behind them, but in my experience you really need more than this. I have mine set up approximately 7ft from the front wall and 4ft from the side walls. The side wall distance is less critical since the backwave cancellation helps reduce side wall interactions. As long as I have the space for them, I wouldn't consider switching back to box speakers after living with the speakers I have now. |
