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What is the appeal of open baffle?

dfuller

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I don't understand how this could possibly be a better option than an enclosure. It seems like you pointlessly lose efficiency and low end response in favor of... something. What am I missing here?
 

mdsimon2

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Taken directly from Linkwitz's site -> http://www.linkwitzlab.com/conclusions.htm

Open baffle loudspeakers
  • Open baffle speakers are inefficient in terms of the mechanical movement that is required to create a given level of sound. This not only applies to speaker cones but also to panel vibrations.

  • Open baffle loudspeakers reproduce bass with less room interaction. It is more articulate than from box speakers.

  • If dipole behavior covers the full frequency range, then the room response becomes perceptually masked by the direct sound.

  • The radiation from the rear of the cone must not be absorbed, but the distance to the nearest reflecting/diffusing surface should be at least 3' (1 m).

  • An open baffle circumvents the box problems of delayed radiation through cone and enclosure panels. They occur typically in the mid-frequency range and are difficult to suppress.

  • Large panel radiators or long line radiators suffer from severe lobing at higher frequencies. It manifests in critical room and listener placement.

  • Even though a dipole requires a 6 dB/oct boost towards low frequencies, it takes little power to drive it to maximum excursion at its lowest bass frequencies. Amplifier power could be an issue as frequency increases, where it requires higher cone acceleration to reach Xmax. Thus SPL is limited by driver volume displacement at the very lowest frequencies and becomes amplifier limited as frequency increases.

  • Realistic bass levels can be obtained from dynamic drivers in open baffles, not from panels. For extreme SPL requirements the number of drivers could get very large and, therefore, below 50 Hz they are more economically replaced by sealed box subwoofers.

  • At frequencies where a 8" driver would become directional it has wider frontal dispersion for an open baffle than if the baffle were closed in the back.

  • Open baffle speakers reach deeper into the room and are less subject to the room response if their polar response is well behaved.

  • ORION exemplifies open baffle loudspeaker design in terms of polar response control and dynamic range. It circumvents the limitations of large panel radiators and yields a small package.

  • The low masses of the moving parts in an ESL, a planar magnetic, or a ribbon driver are necessary to generate useful sound pressure levels. The force generated by an electrostatic or planar magnetic motor is weak. Since SPL is proportional to air volume acceleration, and moving parts Acceleration is Force divided by Mass, the mass has to be lower if the force is too weak to generate sufficient acceleration. Furthermore, since excursion is limited with these drivers the radiating area has to be large to move a sufficient air volume.. These relationships seem to be difficult to grasp by audiophiles. Marketing departments and even some designers like to tout low mass as an inherent benefit giving greater "speed" or frequency response to their speaker, when it is only affecting sensitivity in SPL/W.

  • It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker.

Michael
 

Apesbrain

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Magnepan are open-baffle. I once had a room big enough for a pair of 1.7 and they sounded wonderful. Needed some volume, though. (Or, maybe I just liked to play them loud.) And, had to be away from walls. Adding an REL sub was even better.
 

peanuts

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i agree with linkwitz. i was shocked the first time i heared a good dipole. even his small lxmini sound far less colored than all my other speakers.
 

Roland68

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I don't understand how this could possibly be a better option than an enclosure. It seems like you pointlessly lose efficiency and low end response in favor of... something. What am I missing here?
You can discuss and study about open baffle for the next 5 years, but a minute of listening will do a lot more.

There is a lot of truth in "It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker.". A loudspeaker enclosure, regardless of the type (closed, bass reflex, TL, etc.) creates a lot of problems, most of which you can only hide, but cannot solve.
 

q3cpma

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Way more unpredictable room interaction, but potentially more cancellation leading to a greater direct/omni SPL ratio than normal monopoles. Market advances in LF directivity control make it obsolete, in my opinion.
 

Willem

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My Quad 2805s reproduce the music in the room rather than from the speaker. They also produce fewer room modes, for a cleaner bass. Their size is the only disadvantage.
 

Vandemann

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My Quad 2805s reproduce the music in the room rather than from the speaker. They also produce fewer room modes, for a cleaner bass. Their size is the only disadvantage.
They are bipolar, operating like open baffles.
 

Plcamp

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I don't understand how this could possibly be a better option than an enclosure. It seems like you pointlessly lose efficiency and low end response in favor of... something. What am I missing here?

my OB’s are 95+ dB at 2.8v, so the efficiency criticism isn’t true. Bass is limited with dual 15” woofers to about 50 hz, but that’s easily filled with a sub. In their range, dual OB 15” woofers really pack a punch.

It’s different, and bass sound better IMO…probably due to the 90 degree off axis nulls in OB bass.
 

FrantzM

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Hi

I thought I knew and for the longest time , I cared only about planar speakers. I used to own Magneplanar (several) , Quad ( ESl63). Martin Logan (CLSII) Those planars are in fact open-baffle.
Years went by, I began to notice that the speakers I consistently deemed "better", those that I pursued, were not open baffle... I also began to notice that there was a "sameness" in the sound of open baffle, they impose a singular character, a sort of "spaciousness" on every music from every recordings ... And most require space, aka larger rooms.
Not sure that I would care for these now. I was interested in the Linkwitz LX541 but it would not fit my present room, still need to experience the LX521. Never heard it or the LX Mini...I may still build an LX Mini but what I hear from the LSR308 has me wanting the 708p or better speakers as my next upgrade.
I am at this point in the non-open baffle camp,

Peace
 
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antennaguru

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The dynamic OB main speakers in my reference system are also 95+ dB efficient, and blend seamlessly with my very large sealed cabinet subwoofer system that is also very efficient and has its own amplification with servo control. The natural deep bass front/back wave cancellation of an OB can be a feature rather than a bug when it comes to blending with subwoofers placed in appropriate places in the room that will support great bass. The best part is how the OBs completely disappear in the room and present a natural soundstage of life-like musicians.

High efficiency dynamic OBs are very different from planar and electrostatic panel speakers which are inherently compressed. The high efficiency brings greater transparency and the ability to provide lifelike transient response.
 
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Plcamp

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I am at this point in the non-open baffle camp,

I can’t make up my mind on this. Upstairs is Paradigm Studio 100 v5 and downstairs is PAP Trio 15’s. At this moment the upstairs wins, but I expect that reverses when I change out the OB fullrange.
 

mhardy6647

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I've fiddled, off and on, with open baffles for nigh on two decades. I have heard OB implementations (using more or less conventional dynamic drivers) sound good, but not good enough for full-time listening.
As good a place to start as any for OB experimentation IMO and IME: http://jelabsarch.blogspot.com/2012/06/open-baffle.html

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While some of the aforementioned planar drivers (including electrostatics), I suppose, fall into the OB category, I cannot help but think of them as a somewhat different kettle of fish. I will mention that the epochal Quad "ESL-57" included some (presumably empirically designed) damping material to control the back wave in some way/to some extent. I don't know about later Quads, nor other large planar full- or extended-range electrostatics, though.
 

OWC

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Dipoles/open baffles have a couple of benefits, compared to monopoles

- The interact "less" with the room; meaning cause less standing waves and reflections, the backwave even works for spaciousness.
- Have no internal issues with cabinet resonances/reflections, no non-linear behavior of damping material in the cabinet as well as provide symmetrical acoustic load on the speaker. A cabinet always provide some non-symmetrical load on the speaker = distortion

But like everything in physics, there are always caveats.

Efficiency of open baffles goes down rapidly and drastically beneath the "baffle-step" point.
This heavily depends on the (wave)length between the back and the front.
So in other words, it depends on the size of the baffle they are mounted in.
Often this results in big and wide baffles.

But so much so, that it is really hard and expensive to do anything substantial beneath 40-50Hz.
Even with a double 12 inch, or like 15 inch etc.
Definitely not suitable for any higher SPL applications.

This cancels out some of the earlier mentioned benefits quite a bit.
Because it means the same speaker has to provide (a lot) more excursion and power to get the same amount of SPL.
More excursion always results in more distortion.

The first mentioned advantage can also be taken care of with a multi-sub system.
Actually, this will often give a better and a much more predictable result that can even be easily tuned.
(especially these days, with free software and cheap mics).

The distortion from uneven loading in a closed cabinet is also not as bad, and mostly 2nd order distortion.
Which is in many cases not really noticeable according the literature.

So where open baffles really shine, is from 80-150Hz and up.

But as always, it depends of context and how you compare stuff.
If you would just compare a open baffle or dipole direct to something like a standard 3-way system, the definitely have the benefits of dealing with the room much better. Another flavor of this is the cardioid.

From a construction point of view, open baffles are a lot easier to make.
And to some extend, this is maybe also the psychological power of the system.
It's kind of magical to hear such (great) sound just from a wooden panel or board.
 
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dfuller

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Honestly, from what I've seen so far it's more or less... relying on room reflections? I can't help but feel this would be terribly fiddly.
 
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