Link to XLbaffle here - very simple OB simulation that takes T/S into account
https://sites.google.com/site/amateuraudio/design-software/xlbaffle
https://sites.google.com/site/amateuraudio/design-software/xlbaffle
@ Kjeldsen:
If you are hoping to use free modeling tools you will likely need to use more than one anyway. Even if you can find some software that models both the driver response and the baffle response together, you still need to model what the crossover will do when you insert that. Tools that can do everything are often overly complicated and expensive commercial products.
What I typically do (when modeling) is use the Edge or the Boundary and Diffraction Simulator to generate an FRD file of the baffle response. In a separate program like the Woofer Box and Circuit Modeler I import the baffle response and combine it with the driver response. For a first approximation I model the free-air response of the driver, e.g. in an "infinitely large" closed box. At this point I can see what I am up against in terms of how far "down" the response is as a function of frequency, e.g. is the driver -6dB or -18dB compared to the passband (e.g. >1k Hz) level, and I can make decisions about how much boost I will need to apply and how low in frequency I can expect this driver+baffle combination to be usable, and at what SPL level. All these things are important to consider.
If things look OK at this stage, I export the combined driver+baffle response as another FRD file and then import it into another program in which I will design a real crossover. It's very important to model the driver excursion before this step as a function of SPL and keep that in mind. It is too easy to design an open baffle that is flat to 20Hz if you ignore how much input power is needed to achieve this and what cone excursion is required from the driver. With OB low bass, the demands on the driver are significantly greater.
If you are hoping to use free modeling tools you will likely need to use more than one anyway. Even if you can find some software that models both the driver response and the baffle response together, you still need to model what the crossover will do when you insert that. Tools that can do everything are often overly complicated and expensive commercial products.
What I typically do (when modeling) is use the Edge or the Boundary and Diffraction Simulator to generate an FRD file of the baffle response. In a separate program like the Woofer Box and Circuit Modeler I import the baffle response and combine it with the driver response. For a first approximation I model the free-air response of the driver, e.g. in an "infinitely large" closed box. At this point I can see what I am up against in terms of how far "down" the response is as a function of frequency, e.g. is the driver -6dB or -18dB compared to the passband (e.g. >1k Hz) level, and I can make decisions about how much boost I will need to apply and how low in frequency I can expect this driver+baffle combination to be usable, and at what SPL level. All these things are important to consider.
If things look OK at this stage, I export the combined driver+baffle response as another FRD file and then import it into another program in which I will design a real crossover. It's very important to model the driver excursion before this step as a function of SPL and keep that in mind. It is too easy to design an open baffle that is flat to 20Hz if you ignore how much input power is needed to achieve this and what cone excursion is required from the driver. With OB low bass, the demands on the driver are significantly greater.
I agree, I just think XLbaffle is better than Edge if just one tool have to bee used. I measure raw driver and distortion as well as using my ears. Then I use DSP to overcome the natural obstacles for any speaker and any room. I often overdo it at first, and then I remodel and end up with a simpler filter - when I "abuse" the DSP, the outcome looks good on the freq response, but heavy eq and steep filter just don't sound good (or at least I can't get them to sound good)
I have just bought two woofer for testing their performance.
Build quality, Xmax, Fs and price have been major factors in choosing the right woofer.
B2 audio IS15v2
My major concerns have been high Mms and low Vas, but input from here and reading Adires pdf about woofer speed convinced me, that I could still use this woofer. I have had a lot of other woofers in my mind, but several of them was way to expensive (Dayton RS line and AW Dipole15 amongst others - at least compared to B2 audio)
Build quality, Xmax, Fs and price have been major factors in choosing the right woofer.
B2 audio IS15v2
An externally hosted image should be here but it was not working when we last tested it.
My major concerns have been high Mms and low Vas, but input from here and reading Adires pdf about woofer speed convinced me, that I could still use this woofer. I have had a lot of other woofers in my mind, but several of them was way to expensive (Dayton RS line and AW Dipole15 amongst others - at least compared to B2 audio)
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Id appreciate some advice please on getting Open Baffle bass to fill in 40Hz - 160Hz under ESL's using just a simple planar open baffle to match the ESL panel.
Ive looked at 25 drivers and only the Acoustic Elegance Dipole series models well for 40Hz OB bass. All the others seem to have inherent attenuation under 60-80Hz just where the OB bass is falling off anyway or such pathetic Xmax that they cant deliver SPL on my rudimentary modelling.
The AE Dipole 18" version looks like it gives higher SPL then the 15". However I have room for two 15" under each ESL panel or three 12" but only one 18".
With OB bass is there a formulae to work out the dB gain at the listening position with extra drivers eg is it 3dB going from one to two drivers, 6dB gain with four and 9dB gain with sixteen?
With direct OB bass how does the attenuation fall with distance? Does it beam like an ESL panel with much less attenuation over 5m compared to point source or box speakers? Is there some formulae for working out attenuation over distance for OB bass versus planar ESL versus boxes?
Another thing is if the baffles and drivers are sealed with the floor does that effectively increase the baffle size and limit the OB attenuation with falling frequency? The Edge doesnt seem to model for floor sealing effect but it seems like a floor seal would create a defacto big baffle effect? Also would the reflection off the floor create extra SPL at the listening position some 5m away across the room with a wooden floor and ears at 1m high?
Any suggestions appreciated with much thanks
Ive looked at 25 drivers and only the Acoustic Elegance Dipole series models well for 40Hz OB bass. All the others seem to have inherent attenuation under 60-80Hz just where the OB bass is falling off anyway or such pathetic Xmax that they cant deliver SPL on my rudimentary modelling.
The AE Dipole 18" version looks like it gives higher SPL then the 15". However I have room for two 15" under each ESL panel or three 12" but only one 18".
With OB bass is there a formulae to work out the dB gain at the listening position with extra drivers eg is it 3dB going from one to two drivers, 6dB gain with four and 9dB gain with sixteen?
With direct OB bass how does the attenuation fall with distance? Does it beam like an ESL panel with much less attenuation over 5m compared to point source or box speakers? Is there some formulae for working out attenuation over distance for OB bass versus planar ESL versus boxes?
Another thing is if the baffles and drivers are sealed with the floor does that effectively increase the baffle size and limit the OB attenuation with falling frequency? The Edge doesnt seem to model for floor sealing effect but it seems like a floor seal would create a defacto big baffle effect? Also would the reflection off the floor create extra SPL at the listening position some 5m away across the room with a wooden floor and ears at 1m high?
Any suggestions appreciated with much thanks
I haven't got the B2audio yet, It seems to be hard to get. While I'm wating I have bought a Gladen RS15FA (it's a free air car woofer). Little lower Fs, lighter cone and a bit higher Vas. Linear one-way Xmax is 16 mm. I'm almost done with a test baffle. Build quality for the Gladen (less than 200$) is no less than impressive for the price (no Monacor or Dayton in same price range have similar quality - at least in Denmark). It seems that you can get a lot for the money i car stereo - But just look out, because there is also a lot of junk.
a very informative read from John. Thanks.
I have an unfinished 4-way OB with a 15inch Definimax 4015LF driver from Eminence for the low end (Qts just over 0.5 and Xmax 9mm). the driver was chosen solely based on the subjective impressions by people I trust on this forum (most of them present in class A amplifier threads), and with the intention of digitally EQing and bi-amping.
I am still a little uncertain how the driver's 40Hz resonance will be handled but the goal is not to go too low with the bass (down to 40ish would be Ok)?
just thought I would throw my driver into the mix here. (sorry no data to show; got sidetracked with my already great sounding system(s) so these OBs are stil collecting dust)
http://www.diyaudio.com/forums/multi-way/266524-you-active-multi-way-5.html#post4158184
p.s btw a lot of people experimented after MJK published that paper (long time ago), and most suggested that even beta version sounded better than alpha which tended to be "muddy". eventually the likes of S Linkwitz showed that in multiamping and EQing the whole high driver Qts "issue" becomes irrelevant. moreover, the room interactions rule down low so OB bass is not even necessary; (I have LXMinis with a help of an "invisible" pro subwoofer perfectly integrated into an irregular shaped and pretty open space which already proved the point in my home).
I have an unfinished 4-way OB with a 15inch Definimax 4015LF driver from Eminence for the low end (Qts just over 0.5 and Xmax 9mm). the driver was chosen solely based on the subjective impressions by people I trust on this forum (most of them present in class A amplifier threads), and with the intention of digitally EQing and bi-amping.
I am still a little uncertain how the driver's 40Hz resonance will be handled but the goal is not to go too low with the bass (down to 40ish would be Ok)?
just thought I would throw my driver into the mix here. (sorry no data to show; got sidetracked with my already great sounding system(s)
so these OBs are stil collecting dust)http://www.diyaudio.com/forums/multi-way/266524-you-active-multi-way-5.html#post4158184
p.s btw a lot of people experimented after MJK published that paper (long time ago), and most suggested that even beta version sounded better than alpha which tended to be "muddy". eventually the likes of S Linkwitz showed that in multiamping and EQing the whole high driver Qts "issue" becomes irrelevant. moreover, the room interactions rule down low so OB bass is not even necessary; (I have LXMinis with a help of an "invisible" pro subwoofer perfectly integrated into an irregular shaped and pretty open space which already proved the point in my home).
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I can now recommend the Gladen woofer. In an almost flat narrow baffle, woofer very close to floor it plays 30 Hz in room without eq. This is way better than expected and much much better than my present Vifa (four 10 inch per speaker)
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sorry to hijack the thread
can you advice which diy amplifier that will have 30 - 50 ohm output impedance? I have aragon2004 for my 21" subwoofer in OB but i'm not sure the output impedance.I was looking at ESP P101 or P68 to build.
btw with my mauro penasa gainclone, I have never used its full power, so i think I dont need brute force but a proper amplifier.
this is the driver that I use, might add another to put them in paralel
21″ PA 113212 SW FABULOUS BY ACR | ACR Speaker
Something important when playing with high output impedance / current source amplifiers is that you don't want to use them close to fs. At within 4x of fs the distortion rises a lot compared to a voltage source (measurements on a 6ND430).With that in mind I wouldn't use it on a woofer and especially not a subwoofer.
Current source amps are mind blowingly amazing above 4x fs though, you don't need to have copper heavy motors to get good distortion as just the amp fixes a lot of the distortion.
that is great info, i have read NP test on several FR with F1/F2 amplifier but now i think i will stick on regular voltage source for my sub.
OB speakers interact with the room differently to traditional monopoles. I found that room problems showing up with traditional subs (a 10dB spike at 40Hz, for instance) simply didn't show up when using a pair of OB speakers.
Chris
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