[Hegemony]

Hi all,

I am interested in learning a little about the benefits and downsides of open baffle design.  Could you potentially list some manufacturers of open baffle speakers...or designs for that matter and a little about their positives and negatives?

Thanks guys,
Russ

"Russ - I hope that you don't mind that I split this discussion off from the main thread, since I think it belongs out in the open, where folks can find it.  If I have bothered you with this action, please PM me, and I will try to explain in more detail why I would move in on your post etc.  " mcgsxr, Moderator

[KKM]

Jamo has a new one, here's a review:

http://6moons.com/audioreviews/jamo/909.html


Linkwitz Orion, interesting photos:

http://www.linkwitzlab.com/orion-photos.htm


Gilmore:

http://www.glacieraudio.com/new%20Glacier%20Audio%20Site/Products%20folder/Gilmore/Gilmoreaudio1.htm


Why do they call it "open baffle", isn't the baffle the front panel? Shouldn't it be call "Enclosureless" or "boxless", I know, it doesn't have the same ring. When I first heard of open baffle speakers, didn't know what it was until I saw photo's.

[ctviggen]

Some of these speakers are only part open baffle.  For instance, the OB7 by GR-research is both open baffle and closed box.  Meanwhile, the Linkwitz Orions (as an example) are completely open baffle.  I'm not sure why one would want part open baffle and part closed box. 

I currently have VMPS RM40s, but am considering the Orions solely because of the designer and how much information he has to support his theories.  As a former electrical enginerd, I like someone who provides theories. 

The term "open baffle" is confusing.  Boxless would be better.

[Danny Richie]

An open baffle lower section like the Orion throughs another wrench or two into the mix.

Even using a couple of pretty large woofers with really low Fs still won't get you much in the way of SPL. They have very limited output levels. Plus they need a transform circuit to equalize the low end output loss. This means separate amps must be used as well as an active network.

The really low frequencies are omni-directional anyway and can be controlled by adjusted output.

Designers like Paul of Nomad, The designer of the Alon's (Nola), and myself see more advantage in not allowing the lower ranges to be in an open baffle.

[Davey]

The really low frequencies are omni-directional anyway and can be controlled by adjusted output.

Designers like Paul of Nomad, The designer of the Alon's (Nola), and myself see more advantage in not allowing the lower ranges to be in an open baffle.

Danny,

Do you understand the whole concept of pressure-source versus velocity-source and the 4.8db relative difference in room excitation?  Yes, there is a large subjective element to this...and people will have their preferences...but to describe it as "the really low frequencies are omni-directional anyway" is simplistic and not totally accurate.  The relative concept is well explained on SL's site in non-simplistic terms.

Most Orion owners (myself included) would not evaluate the Orion as having "limited output levels."  It may, relative to the capabilities of some other speakers, but in normal sized listening areas and with sane music most folks will find the SPL capability adequate.

Also, the Orion does not use a transform circuit.  Yes, there is EQ applied (obviously,) but a transform circuit is used for correction of sealed-box alignments and not open-baffle configurations.

Yes, separate amps and active network are required.  This is an advantage, not a disadvantage.

Cheers,

Davey.

[Danny Richie]

but to describe it as "the really low frequencies are omni-directional anyway" is simplistic and not totally accurate.

That's true. They do load the room differently. But they do have to be dealt with in the same way. They both radiate just as much to the rear as to the front. That was what I meant by that.

Most Orion owners (myself included) would not evaluate the Orion as having "limited output levels." 

One's view of limited is subjective. The Orion's are fine for small to medium sized rooms and with most must, but they won't recreate a live concert in MY room.

I did have one customer that replaced his Orion's with a pair of our Alpha LS's because the Orion's had too much of a limited output for him.

Another Orion owner that came here to GR Research to listen to a pair of OB-7's noted that he could never get the level of output from his Orion's that I get from the OB-7's. The Orion's just don't have that level of dynamic capability.

Also, the Orion does not use a transform circuit.  Yes, there is EQ applied (obviously,) but a transform circuit is used for correction of sealed-box alignments and not open-baffle configurations.

It may not have the well known "Linkwitz transform circuit" but it is using a boost circuit to counter the output loss of the open baffle woofers.

Yes, separate amps and active network are required.  This is an advantage, not a disadvantage.

Somehow I don't see needing 6 separate amplifiers as an advantage.

The Orion owner that visited mentioned that he did not quite get the performance he was hearing from the OB-7's from his Orion's and thought that it might be due to the fact that he could not afford to buy six amps that were of the same quality as the pair of tube amps I was using on the OB-7's.

At a later date he might bring them by and compare them. It should be fun.

[PaulHilgeman]

Good thread.

So you don’t realize it when you get to my signature, this is Paul Hilgeman, owner of Nomad Audio and designer of the Ronins.

I'll go over the benefits and drawbacks to open baffle speakers and why I like them and design them.  Then I'll answer a few of the issues in the thread from my perspective.  Some of it will be techie so if there are questions, don't hesitate to ask.

I have worked with open baffle speakers now for about 4 years, working with open baffle midranges and woofers, but only in once instance an open baffle tweeter, the planar magnetic Neo3. 

From a purely subjective point of view, boxless midranges are the way to go for a pure, uncolored midrange.  Now for two disclaimers. 

1)This assumes that there really is no box around the midrange.  The 'sides' of the baffle really cant be more than about 2 to 2.5 inches deep before an audible resonance starts to form. 

2)  This also assumes proper crossover design.  Almost all drivers, weather they are metal, paper, poly, kevlar, fiberglass, ceramic, or some combination start to flex around 1500Hz or so, this is somewhat dependent on driver size and material.  The range at and above this point is what gives a driver 'character', the range from that point up higher in frequency is what makes a metal driver sound like a metal driver and a paper driver sound like paper etc.  There is a bit more to it than that, but that’s most of it.  The benefits of an open baffle midrange typically occur in frequencies below this, giving a much cleaner presentation in the midrange, and usually better dynamics in the lower midrange. 

Midrange power response.  This is a big topic to tackle but one of the critical things in designing a CLOSED BOX speaker is to get the baffle step region right.  This is accomplished by proper cabinet dimension selection and compensation in the crossover.  In an open baffle speaker, this transition occurs differently, and must also be designed around by baffle size selection and crossover design.  However, the end product is where the open baffle and boxed speaker diverge.  The closed box speaker will start to sound bloated and congested as it gets too close to any boundaries.  Open baffle speakers tend to sound very similar regardless of how close they are placed to boundaries, one caveat listed below with regard to this.  Here is an example.  In my secondary listening room, boxed speakers must be very carefully designed.  It is a much more 'live' listening room than my primary room, and the boundaries influence the sound much more.  Therefore, a speaker designed to be placed with the drives 4 feet from the rear wall(probably somewhere between 3.5 and 4.5dB of baffle step compensation)  This speaker will become totally imbalanced if the speaker is moved back to where the drivers are 2 feet from the rear wall.  With the Ronins however, the dipole midrange operates all of the way down through the baffle step region and the woofer operates below this region.  Because of this, the overall tonal balance of the speaker stays very similar weather the drivers are 2.5 feet from the rear wall of 6 feet, of for that matter, in a MUCH larger, much deader room like my primary listening room.  This all stems from the first phrase of the paragraph.  An open baffle midrange has a much more even power response than a closed box midrange.  This is because the close box midrange transitions from an omni-directional source to a source that radiates only forward at a certain frequency.  An open baffle midrange radiates in a much more uniform pattern with regard to frequency.

Midrange Power Response Pt.2.  Midranges beam.  All of them, almost independent of how small they are and how low in frequency they are crossed to a tweeter.  In a typical closed box speaker, the range from 300Hz to probably 1000Hz will have a very wide dispersion pattern across the front hemisphere. Above 1000Hz, the midrange driver will become more and more directional, and the off axis frequency response will be drooping.  A dipolar midrange actually benefits from the off-axis dipole cancellation.  Because both the front and rear wave of the driver are exposed to the room, the sound waves cancel each other out at 90 degrees off axis, and cancel less at less of an off-axis angle.  This helps to match the 300-1000Hz range where a midrange driver is typically radiates very evenly in most directions to it's higher frequency ranges where it typically starts to beam a bit.  This provides a very smooth off-axis response through this region that is very hard to obtain in a boxed speaker without using a VERY small midrange, but you still have the problem in teh above paragraph, which cant be avoided by driver selection, box dimensions and crossover point.

Bottom line, Dipolar midranges sound better in more rooms, have less coloration, and a more even power response, which gives properly designed dipole midrange speakers an incredible balance that is very hard to obtain otherwise.

The main disadvantage is that they cant be placed as close to a rear wall.  A boxed speaker that is designed to be placed close to a rear wall can sound pretty good with the drivers just 18 inches into a room, a dipole midrange speaker couldn’t do this.  The Ronins sound best 2.5 feet into a room.  However, I have not experimented with heavy treatment behind the speaker and less of a distance into the room.

The other main disadvantage is that they usually require a higher crossover point from the midrange to the woofer because the midrange requires a bit of equalization from about 300Hz on down depending on baffle size.  They also have a broad peak in the midrange, but this can be adjusted for in the crossover, and if care is taken the sonic drawbacks of these things can be completely avoided.

So from a subjective point of view, I think that dipolar midranges give a more realistic presence to the music and I find myself really getting more involved with the music.  The midrange is more pure and more dynamic.

Regarding open baffle bass systems like in the Orion.  I feel that they can sound very good, but like Davey says, it is capable of reproducing most music.  To me, that is a limitation in two ways.  First, I want my speakers to be able to reproduce just about anything.  Second, if a speaker is limited in maximum SPL, that means that it will have non-optimal performance at slightly lower SPL's.  All drivers distort as they move, the more they move, the more they distort.  When a dipole bass system has such large amounts of equalization applied to them the drivers really move a lot, and while they may be within their limits, they will produce more distortion than they would if they were producing the same SPL while moving less. 

It is for these reasons that I chose to go with a closed box woofer system in the Ronins.  I don't think that I would ever produce an open baffle woofer system, not unless it had dual 12" woofers per side, and even that had slightly lower output capability than the Ronins.

Regards,
Paul Hilgman

[JohninCR]

Danny,

You're really comparing apples and oranges.  Since the Orions have only two 10" woofers and a limited path differential for the rear wave, their output is quite limited at the bottom (Max spl at 35hz or even 40hz is well below 100db), so the Orion was designed for music that SL likes.  I'd love to hear a pair myself, or even better, spend a week with SL himself, picking his brain and discussing OBs of all types.

Some day I hope you get to step into what I call the "cone of bass" and experience OB bass at dynamic levels, including moving through the null on your way to the listening position.  The greatly reduced reflections really cleans up the presentation, plus you can get away with significant SPLs without disturbing others.


Paul,

Thanks for stopping in.  Resonances with your mids are quite easy to remedy.  To me the bigger problem as you start to fold the baffle, even at the small depths you mention, are reflections off of those side panels, which disturb the coherency of the rear wavefront.  Eliminate the reflections and the problem goes away.  I'm running an FE108 on top with a 10" wide baffle, and I wanted to get them down to near 200hz, so I needed depth on the sides.  The sides extend 4" back on one side and 3" back from the front plane on the other at driver level.  I had to go to the extreme of creating a smooth expansion for the rear wave from the driver cutout to the rear edge of the baffle, which cleared up the reflection problem giving me the sound of a flat baffle with the asthetic, structural and sonic advantages of "wings".

Regarding dynamic bass, I'm not sure even two 12's is enough for many people.  I've set my minimum goal at the surface area of two 15's per side, and that's a hybrid not pure dipole.

[Davey]

Danny/Gents,

I certainly understand the trade-offs between open-baffle bass and conventional bass designs.  I just get a little perturbed when those differences/trade-offs are mis-characterized.  Sorry about that. 

The direct-drive aspect of multiple amplifiers and line-level crossovers is an advantage no matter how you look at it.  Yes, this could result in a much more expensive amplifier setup, but only if the user believes high-dollar amplifiers are a necessity to begin with.  I do not. 

Anyways, since this is the "Open Baffle Speakers" forum hybrid systems are off-topic anyway, are they not?  Moderator?  The OB-7 and Ronin are interesting designs but not really "open-baffle."  Heck, even the Orion is not fully "open-baffle" since the tweeter is conventional.

This could be an interesting Circle.  I've seen many open-baffle designs that I would consider poorly conceived and implemented.....some totally butchered.  Yet, not one of them truly sounded bad in a way that I've heard from some conventional designs.  I attribute this to the robustness of the basic concept.

Paul,  I've actually been listening to open-baffle speakers (in one form or another) for nearly thirty years now.  I think people tend to be fickle about their preferences in speakers, and especially with bass speakers.  Opinions seem to fluctuate through the years.  Generally, and evaluated long-term, I believe open-baffle bass reproduction to be superior (subjectively) to what can be achieved by other means....in a variety of rooms.

Cheers,

Davey.

[Brad]

I think the hybrid designs - as long as at least PART of the system is OB, are within our discussion parameters,

especially when it brings in well-thought-out responses  like Danny, Paul, JohninCR, and Davey (sorry if I forgot anyone) have contributed.
The same principles still apply - and give us more ideas for experimentation.

As long as the discussion stays respectful, we are going to take a light hand in moderating it.

[PaulHilgeman]

Paul,

Thanks for stopping in.  Resonances with your mids are quite easy to remedy.  To me the bigger problem as you start to fold the baffle, even at the small depths you mention, are reflections off of those side panels, which disturb the coherency of the rear wavefront.  Eliminate the reflections and the problem goes away.  I'm running an FE108 on top with a 10" wide baffle, and I wanted to get them down to near 200hz, so I needed depth on the sides.  The sides extend 4" back on one side and 3" back from the front plane on the other at driver level.  I had to go to the extreme of creating a smooth expansion for the rear wave from the driver cutout to the rear edge of the baffle, which cleared up the reflection problem giving me the sound of a flat baffle with the asthetic, structural and sonic advantages of "wings".

Regarding dynamic bass, I'm not sure even two 12's is enough for many people.  I've set my minimum goal at the surface area of two 15's per side, and that's a hybrid not pure dipole.

With regard to rear-waves - exactly, in my expiramentation, re-directing the rear wave is actually better than damping it in the cavities to either side of the driver. 

Regarding the null patern disruptions of the 'wings', yes, absolutely true and absolutely measureable and audible.  You can actually use the wings to shape off-axis response.

With bass.  Yes, you are right, dual 12's in a 20" deep frame was not enough in my opinion.  These were XLS's too.  I really think you
need to hit 110dB@1m, 1 speaker, down to about 30Hz to be convincing in large rooms with far seating distances.

At that point, after the EQ is applied, the ammount of displacement and amplifier power required gets nearly obscene in an open baffle.

Paul,  I've actually been listening to open-baffle speakers (in one form or another) for nearly thirty years now.  I think people tend to be fickle about their preferences in speakers, and especially with bass speakers.  Opinions seem to fluctuate through the years.  Generally, and evaluated long-term, I believe open-baffle bass reproduction to be superior (subjectively) to what can be achieved by other means....in a variety of rooms.

Subjectively, I think that it is so much different than sealed box bass, that it is almost a matter of taste.  Again, ported box bass is vastly different, but the integration issues along with poor tuning in many systems throws it out for me.

Dipole bass can do some things that are pretty impressive, but big picture, it is sealed for me. 

-Paul

[Davey]

Paul,

Actually, the amount of EQ applied has nothing to do with the maximum power requirement for open-baffle configuration.  The driver capabilities and the power available determine the limits.  EQ just allows usage over a wider frequency range.  (Before you think I just contradicted myself read again carefully.) 

Also, power requirements are not obscene for an open-baffle configuration.  Actually quite the opposite since there is much less air-mass loading on the cone (especially in comparison to small, sealed boxes) to "soak up" the amplifier power.  (Remember the little Carver-cube subwoofers and the extremely high powered integrated amplifiers that were required?)

A power amp for an open-baffle woofer needs to have the capability to drive the cone to Xmax in the frequency range of interest.  The same driver used in a closed-box or in an open-baffle configuration will require much less amplifier power for the later case.  However, there's no free lunch, so you will need more drivers...about a 4:1 ratio...to achieve the same SPL capability as the closed-box system.  You would probably accomplish this with more amplifier channels, but those needn't be high power.  Modestly powered amps will work fine.

Sealed box systems can also be pretty impressive.  However, don't lock yourself into one or the other as a superior solution in all cases.  You might find yourself changing your tune in a couple of years. 

Cheers,

Davey.

[JohninCR]

This could be an interesting Circle.  I've seen many open-baffle designs that I would consider poorly conceived and implemented.....some totally butchered.  Yet, not one of them truly sounded bad in a way that I've heard from some conventional designs.  I attribute this to the robustness of the basic concept.

Davey,
That's the beauty of OBs, once you get the midrange out of the confines of a box, even compromised designs generally have very seductive qualities.  I believe that Paul is missing out with boxed bass, but to each his own.

The thing I like is that we're out here in relatively uncharted territory in many ways, and I've already done some stuff that I know has never been tried before despite being a relative noob.  There's no new territory in box designs, just different drivers and different packaging.  Plus, to me the sound from boxes is inferior.  Every driver I've tried to free from its box has sounded better for it.

Paul and everyone else,
It's really nice to be able to talk about OBs from a more than purely subjective point of view.  I'm expecting some in depth discussion in the edge diffraction thread.  I think it may enhance OB design.  Let me know when you guys are ready to talk about having a driver both OB and feed an RLH at the same time.

[Danny Richie]

I believe that Paul is missing out with boxed bass, but to each his own.

I don't know about that. I completely passive design that can be driven by anything. It will have all the best qualities of an open baffle design and still hit reasonably good output levels. I think he is hitting a broader niche.

[Davey]

It will have all the best qualities of an open baffle design and still hit reasonably good output levels.

Well, I don't think so, but that's just my opinion.

I'm thinking that most enthusiastic DIY'ers are looking to push the performance envelope vice targeting a "broader niche," but if that is the objective then it's probably correct that a hybrid system would be the way to go.  A single-amp system better fits the "profile" of what an audiophile thinks is the optimum system.

I've started into discussions like this on numerous occasions.  Generally, the first comments are "I can't justify a multi-amp system because buying another....insert horribly expensive favorite amplifier here....would cost too much and then I'd have to buy another set of MIT interconnect cables at $500.00 a shot."  Oh the pain!
When folks start from that premise it doesn't make much sense to continue the discussion. 

If you and Paul and other manufacturers don't feel you can market a system like that okay, I understand, but don't let lack of saleability to the average audiophile affect your thinking on the technical capabilities of various systems.  I'm not saying that you were, but you appeared to be headed in that direction. 

John,

Yes, my experience is similar.  However, I don't think we're in uncharted territory here.  The concept of an open-baffle design (using conventional drivers) dates waaaaaaay back.  In fact, it's box-designed systems that are the contemporary designs.  The reason Edgar Villchur came up with the initial acoustic-suspension design was to reduce the physical size of the speaker, not to make improvements on the "quality" of bass.

Cheers,

Davey.

[JohninCR]

I believe that Paul is missing out with boxed bass, but to each his own.

I don't know about that. I completely passive design that can be driven by anything. It will have all the best qualities of an open baffle design and still hit reasonably good output levels. I think he is hitting a broader niche.

Marketwise you may be right, and I see that type of design beoming more mainstream than just a niche, because of the easily heard sonic difference.

On the otherhand, I'm getting a listening position F3 of almost 30hz from a single coax 15" in an open configuration.  It won't do 110db, but does 100+, and maybe alot more with the right amp that can control the cone down low, but any amp drives it easily.  It just takes tricking the rear wave into reinforcing the front wave in the bottom octave, instead of cancelling it.  I built one for a friend to use at his beach hotel, and outside with a concrete wall about 10ft behind it's an instant rock concert with much better than concert sound whenever I visit.  Last time it was Queen and Led Zeppelin, live in concert at Jaco Beach, Costa Rica.  As critical as I am with what I build, I could find no faults outdoors, and that was using a puny Powerwave 15W Tamp and a cheap DVD player as a source.

While the sound isn't as wide open as a flat baffle OB, it does retain much of the open and natural sound typical of OBs.  I've begged Dan Wiggins to design a 10" coax for OB use, so we'll see what he comes up with.  The 15 makes for too large of an enclosure for most people, but I think I can coax similar performance out of a 10" with at least 8mm of Xmax, so my fingers are crossed.

[Danny Richie]

My issue with the 10" and larger drivers is that the off axis response falls off to quickly on them and you just can't cross a tweeter low enough to compensate for it.

I will have some new woofers available soon that I can't wait to try out in an open baffle design. I have some samples here now that I will start working with soon.

Check out the new M-165X: http://www.audiocircle.com/index.php?topic=30311.msg277401#msg277401

They use the XBL^ motor structure design and have 7.8mm of x-max each way. 

They have pretty good power handling too. I think I will try one as a mid-bass (playing up to a tweeter) and four below it covering the lower end and all five in an open baffle. I can't wait to see what kind of low end extension I can get out of four of them.

[JohninCR]

Danny,

I'm an OB guy, so I don't even think about more than 20 degrees or so off axis.  I'd opt for line arrays for wider dispersion, and with that slightly down-tilted response those woofers may be perfect for a pair of OB line arrays.

[Danny Richie]

I'd opt for line arrays for wider dispersion, and with that slightly down-tilted response those woofers may be perfect for a pair of OB line arrays.

It is on the list. I just have a few more big projects to complete first. Then I am going to have a higher Q version of the new line source woofers built. It's a lot like the M-165X but has a heavier cone, lower Fs (35Hz), the same X-max (7.8mm each way), and has a truncated frame for stacking them up.

[PaulHilgeman]

Danny,

I'm an OB guy, so I don't even think about more than 20 degrees or so off axis. 

But it matters SOOOOOOO Much.  A Shame.