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Open baffle speakers?

post #1 of 72
Thread Starter 
Am I missing it, or are there not many diy builds of open baffle speakers on this forum? Is that because most builds here are used in home theater? Just curious.....
post #2 of 72
Probably. They're very complex, require lots of space, and don't offer many advantages in the HT world. Also usually low sensitivity compared to what is built around here. Complexity is probably the biggest issue.
post #3 of 72
Thread Starter 
Makes sense. Thanks
post #4 of 72
I have been helping a lot of people with open baffle speakers ever since the Lotus Group used the Dipole12's in their Granada a couple years ago. In the hi-fi world, open baffles have become one of the biggest trends. They are typically used for music only type applications. They have the ability to be more accurate than boxed type designs due to the lack of cabinet resonance. The nulls at 90 degrees to the driver main axes can help with room interaction as well. On the other hand, they require large amounts of excursion from the woofers to make up for the massive losses from the baffle rolloff, so the driver design is very important. That is where the Dipole woofers have come in as they are one of the few woofers anywhere that were really designed with this in mind.

The Edge baffle simulator works very well for modelling the baffle effects. One thing is that people tend to underestimate just how significant the baffle rolloff is. The following is a graph of a baffle about 18" wide.



From 250hz down to 30hz there is a 16dB drop and this takes significant driver displacement, EQ, and a good amount of power to compensate for. Typically multiple larger drivers are needed to take care of this. However, if you were crossing to a subwoofer whether sealed, vented, infinite baffle, or passive radiator, an open baffle going down to only 80hz or so could be more practical for home theater use. At least for the front 3 channels anyway. Ideally you would want to cross to an infinite baffle subwoofer then to achieve similar results with no enclosure resonance.

Here are a few good examples of commercial and DIY open baffle systems:

http://www.lotusgroupusa.com/Granada.htm
http://soulsonicspeakers.com/gallery.html
http://www.kyronaudio.com.au/Gaia.html

http://www.diyaudio.com/forums/multi-way/233045-ae-speakers-dipole-15-lo15-need-advice-4.html
post #5 of 72
Quote:
Originally Posted by keager View Post

Makes sense. Thanks
Also go and hear a few before deciding to spend the time and effort in building some. A NaO or a Linkwitz Orion would be a good point of reference to decide if you like the concept. I've never heard one I like (so far) especially with rich and complex stuff like Beethoven 9th or NIN.
Edited by A9X-308 - 4/27/13 at 1:35am
post #6 of 72
Thread Starter 
Thanks for the info guys.
post #7 of 72
Keager,
There's no better source of information regarding OB designs/information, than Siegfried Linkwitz.

If one took the time and perused his wonderfully informative website, they'd come out the other-side all the better ... just sayin'.

There's a lot there, I certainly enjoy it.
post #8 of 72
Thread Starter 
Quote:
Originally Posted by FOH View Post

Keager,
There's no better source of information regarding OB designs/information, than Siegfried Linkwitz.
You the man, FOH!

If one took the time and perused his wonderfully informative website, they'd come out the other-side all the better ... just sayin'.

There's a lot there, I certainly enjoy it.
post #9 of 72
Open baffle speakers aren't great for home theatre. The rear output creates a large sweet spot but it also results in a loss of image focus. The image is artificially stretched and lacks sharpness and focus. I find this a problem for home cinema where voices appear stretched and vague in location. However, there is an option worth pursuing here. One could take an Econowave styled speaker with a CD waveguide and combine it with a large open baffle midwoofer running to say 300 Hz on a relatively wide baffle. There is no loss of sensitivity and the lateral null extends dispersion control down into the midrange. You can do this with a horn but the mouth must be larger. Now if you treat the wall behind heavily, you can now get image focus. Essentially now you have a more conventional speaker with enhanced dispersion control. Add in a bass module below and there is no loss of sensitivity.

Here is one example of a small dipole:



This particular one, from memory, had a Vifa P13 midwoofer - you can see the constant directivity in the midrange comes from the baffle, then it starts beaming a little before handing over to a dome tweeter. The combination is a bit of a mess but you can see what can be achieved in the midrange.

Now here is a speaker of mine, an Ewave type speaker with a 10" mid and waveguide:



You see the better transition in using a waveguide, but as a monopole the dispersion becomes quite wide in the midrange.

An open baffle speaker removes "box coloration" but adds "room coloration." Open baffle fans tend to forget that part. Killing the back wave inside a speaker box is much easier than killing it in a room with a lot of acoustic treatment. Most rooms are not well treated enough for this to be a better situation. It puts you very much at the mercy of the room.

BTW I've heard the Kyron speaker at the Australian Hifi Show and it was very impressive.
post #10 of 72
Thread Starter 
Quote:
Originally Posted by paulspencer View Post

Open baffle speakers aren't great for home theatre. The rear output creates a large sweet spot but it also results in a loss of image focus. The image is artificially stretched and lacks sharpness and focus. I find this a problem for home cinema where voices appear stretched and vague in location. However, there is an option worth pursuing here. One could take an Econowave styled speaker with a CD waveguide and combine it with a large open baffle midwoofer running to say 300 Hz on a relatively wide baffle. There is no loss of sensitivity and the lateral null extends dispersion control down into the midrange. You can do this with a horn but the mouth must be larger. Now if you treat the wall behind heavily, you can now get image focus. Essentially now you have a more conventional speaker with enhanced dispersion control. Add in a bass module below and there is no loss of sensitivity.

Here is one example of a small dipole:



This particular one, from memory, had a Vifa P13 midwoofer - you can see the constant directivity in the midrange comes from the baffle, then it starts beaming a little before handing over to a dome tweeter. The combination is a bit of a mess but you can see what can be achieved in the midrange.

Now here is a speaker of mine, an Ewave type speaker with a 10" mid and waveguide:



You see the better transition in using a waveguide, but as a monopole the dispersion becomes quite wide in the midrange.

An open baffle speaker removes "box coloration" but adds "room coloration." Open baffle fans tend to forget that part. Killing the back wave inside a speaker box is much easier than killing it in a room with a lot of acoustic treatment. Most rooms are not well treated enough for this to be a better situation. It puts you very much at the mercy of the room.

BTW I've heard the Kyron speaker at the Australian Hifi Show and it was very impressive.

Thats great info, thanks. My intent was just for music listening. I already have a decent setup for home theater. Already have a reasonably substantial infinite baffle subwoofer system under my floor. Basically what got me interested, was the fact I was given a bunch of very nice veneer and started considering a new build. I would like to experiment with this I think. I already have a mini dsp and receiver, would just need plans and drivers, and an amp or two.
post #11 of 72
It's well worth trying - even just with scraps. Easily done in an afternoon.
post #12 of 72
For music, if you have the right drivers and have a way to EQ/compensate, I say go for it. Otherwise, I agree with Paul and John 100%.
post #13 of 72
Thread Starter 
Well, I think I want to try it. I have the mini dsp, a receiver, a four channel classdaudio 1000w amplifier, and the subs already. I would just need a recommendation on some drivers, and maybe a basic baffle design. Probably would want low cost initially to experiment with to make sure I want to go that path. if I do, I would be willing to invest needed funds for high end components. I appreciate everybody's time and consideration.
post #14 of 72
The plans are probably not expensive, but the drivers are. Most OB speakers done right are 4 way, and for a reason. The have a high low-end cut off and a dipole peak fairly low at the top, thus the band pass is very small. With a subwoofer system perhaps there is a 3-way that ignores the bottom portion available.
post #15 of 72
A bit of misinformation being tossed out in this thread. Compared to monopoles, dipoles radiate a greater percentage of total sound as direct to listener. The backwave is still less sound than the indirect sound radiated by monopoles, and thus dipoles tend to be less room dependent, not more. As for absorbing the backwave, if felt necessary, monopoles emit equally strong backwave in the lower frequencies that are difficult to absorb. Dipoles emit more rear mid and high frequencies, which are not difficult to absorb if desired. IME, this greater direct/reflected sound ratio tends to tighten imaging, not smear it. If anything, the characteristically narrow dispersion creates hyperfocused imaging with small sweet spot that can be problematic for multiseat theater use. Smearing sounds more like a description of some panels, which are typically dipole, but not all dipoles are panels.

Spot on comment about dipoles tending to be low in efficiency, specifically low frequencies. This can be overcome with enough surface area, but you pay in both price and size required.

Designing a good dipole isn't trivial. Designing one that can rock out reference levels at a good distance with superb quality is possible, but very complex, expensive, and large.

Using horns can retain many benefits of dipoles such as increased direct/indirect sound ratio and balanced power response, but with qualities beneficial for theater such as wider (but still controlled) dispersion and much increased efficiency/sensitivity. They can also be built far cheaper than an HT dipole champ. As with any topology, horns have some tradeoffs but these tend to not be as noticeable in an HT environment. Its no surprise horns remain popular around here, as AVS tends to be largely focused on home theater.
post #16 of 72
Quote:
Originally Posted by keager View Post

Well, I think I want to try it.
Here you go then.
post #17 of 72
OP, have you considered building the Statements? They have AB open back mid-range and have gotten excellent reviews. Another good speaker that has the open back mid-range s the Philharmonic 3 from Dennis Murphy, although not a DIY design, it has also gotten excellent reviews.

Are you capable of designing a crossover? That is the biggest hurdle that you will have to jump. Oh and you will need some measurement gear as well.
post #18 of 72
Thread Starter 
Quote:
Originally Posted by Martycool007 View Post

OP, have you considered building the Statements? They have AB open back mid-range and have gotten excellent reviews. Another good speaker that has the open
back mid-range s the Philharmonic 3 from Dennis Murphy, although not a DIY design, it has also gotten excellent reviews.

Are you capable of designing a crossover? That is the biggest hurdle that you will have to jump. Oh and you will need some measurement gear as well.

Thanks marty. I would like to try a true ob to start with since they are relatively easy to build, so I can tell if I like the way they sound. I know the statements are great speakers, but are very involved to construct. Since I have a mini DSP and an extra amp, I was thinking of doing an active x-over.
Edited by keager - 4/28/13 at 6:37am
post #19 of 72
Ran into thread while investigating some OB possibilities for my HT. Coincidentally, I recently built a DIY version of Bert Dopppenberg's Orelo although 1/2 the drivers. I am currently using Eminence Kappalite 3015LF for the main L and R speakers in a two way setup, actively crossed. Although not a high Qts driver for an OB, they are performing very well thus far.

I just finished installing them a couple of days ago and am running the system through it's paces to compare with my previous enclosures. I am really impressed with the sound and capability of this design and the whole OB setup. I had no clue that an OB can sound so good. I stared out with Klipschorns and have continually worked my system trying to find the sound I like for both 2 channel and 7.1 HT.

I did take a bunch of outside FR measurements prior to building three of these and was impressed enough to continue the build. Granted, I am only using them from 70Hz to 204Hz. I use a pair of actively controlled Klipsch RSW-15s from 20Hz to 70Hz and my Oris horns form 204Hz on up.

I'm very much a newb on the OB theory, but really like the quality of the sound.





My current goal is to find similar performance with a smaller waveguide footprint. These are approx. 52" at the mouth and about 25" deep. When I tested just the OB, no 'wings', the low end suffered enough that it seems necessary to have the waveguides in place.

This is Bert's Orelo:



Sorry, I can't figure out why the Orelo picture is on it's side...but you get the idea.

Here is the back of my mains:


Edited by Rudy81 - 4/28/13 at 8:05am
post #20 of 72
Thread Starter 
Wow, those look amazing. I have found a couple small, inexpensive OB builds that I will try so I can see if I like the sound. These will be placed in a large open living room with plenty of "challenges", so I don't want to dump a ton of money and time into something that just doesn't work in my room.
post #21 of 72
Its worth noting that adding horn flared baffles to an open baffle will result in asymmetric front and rear lobes. Power response might be usable, but lots of careful measuring is in order.
post #22 of 72
Quote:
Originally Posted by keager View Post

Wow, those look amazing. I have found a couple small, inexpensive OB builds that I will try so I can see if I like the sound. These will be placed in a large open living room with plenty of "challenges", so I don't want to dump a ton of money and time into something that just doesn't work in my room.

One thing that really impressed me about the OB is that unlike every other speaker I have measured in my room, these provided the cleanest plots and showed the least room interaction. I have no idea why that is, but those were my results. An OB setup is certainly about as inexpensive a build as you can get. A very simple OB prototype will tell you if it will work in your room or not. Although, I did find that just my baffles alone without the wings lose some performance in the low end.

The FR plot below was taken outdoors while working on my baffle and prototype wings. No smoothing or gating! As you can see, the red line is the baffle only and it does take a hit in the low end compared to the wings added.

post #23 of 72
Thread Starter 
I'm hoping I can go with a relatively narrow baffle since I really don't need any bass below 50hz from the OB speakers. Was thinking maybe a couple twelves in each
post #24 of 72
Quote:
Originally Posted by paulspencer View Post



Is it just me or does this look like the Stanley Cup laying on its side?
post #25 of 72
Thread Starter 
It's a sign!
post #26 of 72
Narrow is better for open baffle afaik.
post #27 of 72
^^ It's frequency dependent. Linkwitz and Kreshovsky have quite a bit of detail about it on their pages.
post #28 of 72
Yes you're more correct. Width is a trade off of low frequency extension and the upper dipole off axis peak.
post #29 of 72
OB's are great! Built a simple 2 way pair for my PC setup using some cheapy 6.5" woofers in about 2 hours. They do require massive amounts of EQ to not sound "tiny" though. However I do like the massive soundstage for music listening biggrin.gif
post #30 of 72
Quote:
Originally Posted by keager View Post

Am I missing it, or are there not many diy builds of open baffle speakers on this forum? Is that because most builds here are used in home theater? Just curious.....

I don't get OB speakers. They look to me like a good methodology for getting less than the optimum amount of bass out of perfectly good LF drivers.

Looking at the technology of loudspeakers, a lot has been understood and benefited from by controlling the directivity of speakers, and OB seems to be running in the opposite direction.

I've spent a fair amount of time listening to a well set up pair of Linkwitz-provided Orions, and done level matched done level matched comparisons of them to conventional systems and while I have no complaints about their SQ, I also heard nothing that I'd pay a nickle for.
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