Hey everyone!
Here's a little story about how I became infected with the open baffle virus.
A couple of years ago I bought some Telefunken (DEW / Magnetfabrik Dortmund) 10 inch (25 cm) drivers for €3 on a flea market. It's an old paper driver with a whizzer cone. Can't find any info about them though. I never got around to do anything with them, though the idea of building some open baffles for them has been in the back of my mind ever since I've had them... Weird speaker designs intrigue me.
After years of gathering dust on the shelf I finally built a pair of open baffles for these drivers yesterday. The design is based on the design of the Betsy by Caintuck Audio. Don't look too closely, they're quite rough and they're actually not finished yet. It started as a quick and dirty project.
At first the drivers were very shouty. It was so bad, I considered giving up on the project, or at least, the drivers. But then I read something about putting a resistor in series with the driver, so I added a 1,1 Ohm resistor in series with the driver. This fixed most of the shoutyness. Magic!
When I first started listening to them, I wasn't impressed at all. But then I started noticing new things and I started playing with placement, and well... I've been listening to them this whole afternoon!
There's so much wrong with them. They're still quite peaky / shouty and there's no output below ~80 Hz and I guess above ~12 KHz, but I love the sound. I've had Victor Wooten (especially The Vision) and Take 6 (Sweet Georgia Brown) on repeat for at least an entire hour. High Water Everywhere (live from the Royal Albert Hall) by Joe Bonamassa suddenly came to live. There's such an immense sense of space and depth. Instrument separation and definition in the lower frequencies is unmatched. Hearing an open baffle speaker for the first time really is quite the experience!
On to my problem - after putting them away again and putting up some music on my regular closed box speakers I miss the transparency and the soundstage of the open baffle speakers... The sound of the speakers I've loved for so long seems dull, dry, I don't know... It's missing something - room interaction? Space filling sound?
Has anyone else had this experience after hearing open baffle speakers for the first time? And how do I get rid of this open baffle disease...
Here's a little story about how I became infected with the open baffle virus.
A couple of years ago I bought some Telefunken (DEW / Magnetfabrik Dortmund) 10 inch (25 cm) drivers for €3 on a flea market. It's an old paper driver with a whizzer cone. Can't find any info about them though. I never got around to do anything with them, though the idea of building some open baffles for them has been in the back of my mind ever since I've had them... Weird speaker designs intrigue me.
After years of gathering dust on the shelf I finally built a pair of open baffles for these drivers yesterday. The design is based on the design of the Betsy by Caintuck Audio. Don't look too closely, they're quite rough and they're actually not finished yet. It started as a quick and dirty project.
At first the drivers were very shouty. It was so bad, I considered giving up on the project, or at least, the drivers. But then I read something about putting a resistor in series with the driver, so I added a 1,1 Ohm resistor in series with the driver. This fixed most of the shoutyness. Magic!
When I first started listening to them, I wasn't impressed at all. But then I started noticing new things and I started playing with placement, and well... I've been listening to them this whole afternoon!
There's so much wrong with them. They're still quite peaky / shouty and there's no output below ~80 Hz and I guess above ~12 KHz, but I love the sound. I've had Victor Wooten (especially The Vision) and Take 6 (Sweet Georgia Brown) on repeat for at least an entire hour. High Water Everywhere (live from the Royal Albert Hall) by Joe Bonamassa suddenly came to live. There's such an immense sense of space and depth. Instrument separation and definition in the lower frequencies is unmatched. Hearing an open baffle speaker for the first time really is quite the experience!
On to my problem - after putting them away again and putting up some music on my regular closed box speakers I miss the transparency and the soundstage of the open baffle speakers... The sound of the speakers I've loved for so long seems dull, dry, I don't know... It's missing something - room interaction? Space filling sound?
Has anyone else had this experience after hearing open baffle speakers for the first time? And how do I get rid of this open baffle disease...
I agree completely!
A friend of mine built the same thing you did above (copying the Caintuck construction) but used Lii Audio F-15. Incredible midrange. I've had them for about 6 months now and the quality of the timbre of saxophones still shocks me. They're also very loud even with a 45 SET amp.
As for whether or not the open baffle speakers are "better" than box speakers, I'm not sure. But to your point, when I go back to listening to box speakers, the sound is muffled, constrained, and pretty unsatisfying. They are a pair of Polk Monitor Series 2 from the 90s. Nothing special and belonged to my parents. You can get them for $100-300 on eBay. They don't do anything particularly well, but they do cover a decent range.
My wife took some courses on audio engineering and recording in college and vastly prefers the Polk to the Lii Audio. She finds the compromises that the Lii make with regard to bass and the high-end to be unforgivable.
The really interesting thing (at least to me) is that the differences between the speakers mentally "fade" the longer I listen to either without switching back. That is to say, the magic of the open baffle fades (somewhat) the longer I listen. The offensive box-y qualities of the Polk are very pronounced when I rotate them back in, but I quickly come to appreciate the balance and greater range that they offer. (As I mentioned, they are bass reflex and can easily outdo the open baffle in our room).
In the end, I have to say that it's easy to be swept away by aspects of open baffle sound, but in the long run, I do appreciate the fact that the Polk sound similar regardless of the room that they're in. The open baffle speakers, though, are very sensitive to placement and room size and so forth. I've heard the same speakers in a very small room in a near-field listening setup and find them to be mediocre in that situation.
A friend of mine built the same thing you did above (copying the Caintuck construction) but used Lii Audio F-15. Incredible midrange. I've had them for about 6 months now and the quality of the timbre of saxophones still shocks me. They're also very loud even with a 45 SET amp.
As for whether or not the open baffle speakers are "better" than box speakers, I'm not sure. But to your point, when I go back to listening to box speakers, the sound is muffled, constrained, and pretty unsatisfying. They are a pair of Polk Monitor Series 2 from the 90s. Nothing special and belonged to my parents. You can get them for $100-300 on eBay. They don't do anything particularly well, but they do cover a decent range.
My wife took some courses on audio engineering and recording in college and vastly prefers the Polk to the Lii Audio. She finds the compromises that the Lii make with regard to bass and the high-end to be unforgivable.
The really interesting thing (at least to me) is that the differences between the speakers mentally "fade" the longer I listen to either without switching back. That is to say, the magic of the open baffle fades (somewhat) the longer I listen. The offensive box-y qualities of the Polk are very pronounced when I rotate them back in, but I quickly come to appreciate the balance and greater range that they offer. (As I mentioned, they are bass reflex and can easily outdo the open baffle in our room).
In the end, I have to say that it's easy to be swept away by aspects of open baffle sound, but in the long run, I do appreciate the fact that the Polk sound similar regardless of the room that they're in. The open baffle speakers, though, are very sensitive to placement and room size and so forth. I've heard the same speakers in a very small room in a near-field listening setup and find them to be mediocre in that situation.
Add a helper woofer below 120Hz. Can be sealed or reflex or if you want to keep OB, try a SLOB (slot loaded open baffle). I am getting bass down to 43Hz (F3) and 90dB sensitivity. It makes a huge difference for the overall balance. OB or dipole tops have a great natural sound and can be quite amazing. Have fun.
As Adason said, work on your baffles. Your baffles have circular radius which makes them a large truncated disk with close to equidistant edges. This is not good for minimizing diffraction. A rectangle is better and a trapezoid is better than a rectangle. And if you are adventurous, a Fibonacci sequence spiral shape (increasing radius like a seashell is even better than a trapezoid).
As Adason said, work on your baffles. Your baffles have circular radius which makes them a large truncated disk with close to equidistant edges. This is not good for minimizing diffraction. A rectangle is better and a trapezoid is better than a rectangle. And if you are adventurous, a Fibonacci sequence spiral shape (increasing radius like a seashell is even better than a trapezoid).
This might just be the best solution.
Oh yes, I've seen the Lii Audio drivers in several pictures... I'd love to hear / own a pair some day, they appear to be very well made. Though I have to say, the fun for me is in the fact that these Telefunken / DEW drivers only cost me €3. I did not expect this experiment to end with me going down the OB rabbithole.
Yeah, I understand where your wife is coming from. It's hard to appreciate something that sounds "wrong" if you are an audio engineer I guess. The purist / perfectionist in me hates these things
. But I'm trying to distance myself from perfectionism. That's the key to be able to start enjoying what you have, instead of always wanting something more (or supposedly "better").I recognize what you're saying. Once the OB sound is imprinted in your brain, a boxed speaker sounds weird. Once you're used to the sound of a boxed speaker, the OB sounds a bit funny at first. I read a quote the other day (here): "Many people who hear a speaker with an open baffle for the first time are first irritated, then thrilled.". This is very true!
I don't know if OB is the end-all solution for me. My daily drivers are a pair of Magnat All-Ribbon 4P speakers. I've tried several other speakers, but I've always come back to these. They're the underdog in the All-Ribbon series imho. So far I've built a two way MLTL, a small full range TL, and now open baffles cross my path. I just like to look around and explore the different philosophies / directions in the audio hobby. There's so much fun to be had and weird ideas to explore.
I might do that if I get serious with these! However, I do think my drivers are quite shouty by themselves. The whizzer cone is very prominent in the midrange. So I'll have to decide whether I want to improve these speakers or just start from scratch with more suitable drivers.
I based the current baffle dimensions fairly accurately on the Betsy OB. The driver is mounted 4/9th down from the top of the baffle, so off the vertical center. Horizontally it's centered though. I've been thinking about cutting away more from the top of the baffles to create a "fat egg" shape 🥚, might be fun.
I like your Fibonacci / spiral shape design. Don't you get beaming or one-sided reflection issues that way? It would appear to me as if they get even more sensitive to placement, but I could be very wrong there.
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check, "Cabinet Design"
https://sites.google.com/site/undefinition/dipole-and-open-baffle/diy-aethers
http://web.archive.org/web/20080209173425/http://www.troelsgravesen.dk/OBS.htm
https://speakerprojects.wordpress.com/2019/08/01/eminence-lil-buddy-open-baffle-speaker/
https://speakerprojects.wordpress.com/2016/08/29/eminence-beta-12lta-on-open-baffle/
https://speakerprojects.wordpress.com/2015/12/14/vifa-tc9-plus-helper-tweeter-on-open-baffle/
post 2757 3 way open baffle
https://www.diyaudio.com/community/threads/fast-fun-inexpensive-ob-project.110583/page-138
https://sites.google.com/site/undefinition/dipole-and-open-baffle/diy-aethers
http://web.archive.org/web/20080209173425/http://www.troelsgravesen.dk/OBS.htm
https://speakerprojects.wordpress.com/2019/08/01/eminence-lil-buddy-open-baffle-speaker/
https://speakerprojects.wordpress.com/2016/08/29/eminence-beta-12lta-on-open-baffle/
https://speakerprojects.wordpress.com/2015/12/14/vifa-tc9-plus-helper-tweeter-on-open-baffle/
post 2757 3 way open baffle
https://www.diyaudio.com/community/threads/fast-fun-inexpensive-ob-project.110583/page-138
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Adding a resistor in series will not do much to the shrill sound.
You either need a BSC, which is a resistor and inductor, or a notch at the offending peak(s).
I haven't found a driver that would not benefit from a little tweak here or there.
Simple enough, but you will need a mic.
If one is into audio, a mic is just as necessary as a toaster if you want toasts in the morning.
The "illusion" that my OBs cast of soundstage depth is what gets me everytime. I've let my Lii F15 system sit idle for sometime, as I prefer the seat I have in the bedroom vs the sofa. Lately I occasionally turn on the livingroom system when having lunch, for some background jazz streaming from my iPhone to the system via BT. The "easy" listening input; I dont have power up a big screen and boot Windows...log in...just to hear some music.
[I know, I should just have a Daphile bootable USB stick at the ready; wait for it to show up on the network.]
Walking past on my way into the kitchen, I wondered if they still... Wow! That instrument is back there; a clear as day image floating well behind the plane of the baffle board. I like it.
Always wonder why the Betsy "barrels" are copied repeatedly verbatim, when a little "crosseyed" offset of the speaker on the baffle location just might mitigate some of the edge diffraction due to the perfect symmetry of the original design? Guess it must be a trade off between an attempt to maximize bass (no short edge where bass can leak around) and whatever diffraction there is. You can always put a wing back there, out of sight.
I've noticed in building a couple OBs that the baffle board is a long, flappy thing pinned to the ground at its stand. Captured at essentially the bottom edge, it rings mechanically. A box is much less "flappy". Wings help stiffen the structure, while providing more distance the back wave has to go around to get to the front.
[I know, I should just have a Daphile bootable USB stick at the ready; wait for it to show up on the network.]
Walking past on my way into the kitchen, I wondered if they still... Wow! That instrument is back there; a clear as day image floating well behind the plane of the baffle board. I like it.
Always wonder why the Betsy "barrels" are copied repeatedly verbatim, when a little "crosseyed" offset of the speaker on the baffle location just might mitigate some of the edge diffraction due to the perfect symmetry of the original design? Guess it must be a trade off between an attempt to maximize bass (no short edge where bass can leak around) and whatever diffraction there is. You can always put a wing back there, out of sight.
I've noticed in building a couple OBs that the baffle board is a long, flappy thing pinned to the ground at its stand. Captured at essentially the bottom edge, it rings mechanically. A box is much less "flappy". Wings help stiffen the structure, while providing more distance the back wave has to go around to get to the front.
Hmm yes that would be interesting to try. I'll see if I want to do that. I'm actually thinking about starting over with decent drivers. I saw another post on this forum from someone using the Tang Band W4-1337SDF in an open baffle configuration. That might be a cool step up from this random driver / baffle combination.
I will check these out, thank you! Especially Troels Gravesen his webpage looks very interesting. I've seen his name pop up quite often on the forum.
The resistor in series with the driver creates a voltage divider over the resistor and the voice coil and it loosens the control the amplifier has over the coil. I believe it tends to make a solid state amplifier behave more like a tube amplifier (something with damping). I found out about the trick here on AudioKarma and it definitely makes a difference. I've played around with some other values (up to 6,8 Ohm but that's absolutely pointless as the driver would only receive power when it's impedance is high) but between 0,5 - 1,1 Ohm seems to work best. I'll buy a measuring mic soon!
Lii Audio F15 seems to be very popular... I'm getting a curious itch to try them now.
I think it has a lot to do with the WAF and because the Betsy attracted a lot of attention for its performance. If something is known to perform well, why not take it as a baseline for your own speaker? (Of course I know they use a completely different driver which works exceptionally well in that specific baffle but still, it's an easy starting point).
Short version: aside from aesthetics, for the commercial side of things (of which there are several examples, e.g. the Decware offerings) it's quicker & cheaper. One baffle, no mirroring, no different templates, no risk of any logistical mixups.
Re a series resistor, a single resistor doesn't create a voltage divider as such, but it has the effect of raising the effective output impedance of the amplifier, so the FR is a little more likely to track the speaker impedance. The lowered mass-corner will at the least give a touch more LF extension -how much depending on how much resistance is added. Inefficient, since you're burning up power in the resistor, but providing it can handle the current & has decent heat-sinking / ability to dissipate the excess heat buildup, it can be useful in certain situations, providing you know exactly what you're doing and why.
Re a series resistor, a single resistor doesn't create a voltage divider as such, but it has the effect of raising the effective output impedance of the amplifier, so the FR is a little more likely to track the speaker impedance. The lowered mass-corner will at the least give a touch more LF extension -how much depending on how much resistance is added. Inefficient, since you're burning up power in the resistor, but providing it can handle the current & has decent heat-sinking / ability to dissipate the excess heat buildup, it can be useful in certain situations, providing you know exactly what you're doing and why.
Makes sense from a commercial perspective. Still wondering how bad this baffle shape can really be, regarding the many positive reviews of the Betsy.
I use 2x 10W 2,2 Ohm resistors in parallel per driver (for heat dissipation indeed), netting me a 1,1 Ohm series resistance. The effect is very audible and rather pleasant.
I'm thinking of adding a phase plug to the drivers to reduce bouncing waves inside the whizzer cones. Might improve the HF response
(Upper) mass corner frequency = 2 * Fs / Qts'
where Qts' = driver Qts augmented by any series resistance from amplifier output impedance, cable, coil, resistor, connection...
Calculate new Qts
I hope I'm not generalizing too much by saying that it is the frequency below which a driver needs help from an enclosure. By adding a series resistor, you will raise the effective Qes and thus Qts, thereby lowering the upper mass corner frequency and will get a bit more LF extension from the same baffle or enclosure.
where Qts' = driver Qts augmented by any series resistance from amplifier output impedance, cable, coil, resistor, connection...
Calculate new Qts
I hope I'm not generalizing too much by saying that it is the frequency below which a driver needs help from an enclosure. By adding a series resistor, you will raise the effective Qes and thus Qts, thereby lowering the upper mass corner frequency and will get a bit more LF extension from the same baffle or enclosure.
Hi,
What is the driver size advised in a no baffle design for the mid to treble range please. I see Linkwitz used to choose a 3 above a 6" but see alsonmany use 10 to 12" as bastanis. The first nul in the highs with high diameter unit occurs very soon, no ?
Is a full range is working the same way in open bafle than loaded, as Bastanis does with 12" ?
What is the driver size advised in a no baffle design for the mid to treble range please. I see Linkwitz used to choose a 3 above a 6" but see alsonmany use 10 to 12" as bastanis. The first nul in the highs with high diameter unit occurs very soon, no ?
Is a full range is working the same way in open bafle than loaded, as Bastanis does with 12" ?
Congrats on a nice build! You'll enjoy them for a long time to come.
I love open baffle speakers and have build a fair number with many different size drivers 21, 18, 15, 2x15, 12, 10, 8 and 6x9 inches. I've build good ones and bad ones. Maybe one or two great ones. But open baffle has a dirty little secret. Lack of bass. OK, maybe not so secret, but certainly dirty.
Because the long bass wavelengths wrap around the baffle front to back and back to front, they cancel out. That means a distinct lack of bass. That's the dirt. And that means to get a proper tonal balance on OB, you have to throw away efficiency. You have to throw away some of the top end response to make it match the low end. If you don't, then your OB will be all midrange and top end, thin with no weight. This part seems to be a secret to many builders/designers. With OB you are going to get only so much bass, therefore for a proper tonal balance you either have to boost the bass, or attenuate the mids and highs so that it all balances.
To achieve good tonal balance on OB the usual thing to do (once you have chosen the drivers and baffle size) is to use a low pass shelf. That easy make from just two parts - an inductor bypassed by a resistor. Determining the value of the inductor is the tricky part, the resistor is easier and can be done by ear.
If you are using a 10" driver on OB, there isn't much hope of getting any real bass. As others have said, that's a good driver to use with a helper woofer. I've done a few 6-10" vintage drivers on OB with the help of 15" woofers underneath. It's a great combo.
Enjoy the OB, there is no going back!
I love open baffle speakers and have build a fair number with many different size drivers 21, 18, 15, 2x15, 12, 10, 8 and 6x9 inches. I've build good ones and bad ones. Maybe one or two great ones. But open baffle has a dirty little secret. Lack of bass. OK, maybe not so secret, but certainly dirty.
Because the long bass wavelengths wrap around the baffle front to back and back to front, they cancel out. That means a distinct lack of bass. That's the dirt. And that means to get a proper tonal balance on OB, you have to throw away efficiency. You have to throw away some of the top end response to make it match the low end. If you don't, then your OB will be all midrange and top end, thin with no weight. This part seems to be a secret to many builders/designers. With OB you are going to get only so much bass, therefore for a proper tonal balance you either have to boost the bass, or attenuate the mids and highs so that it all balances.
To achieve good tonal balance on OB the usual thing to do (once you have chosen the drivers and baffle size) is to use a low pass shelf. That easy make from just two parts - an inductor bypassed by a resistor. Determining the value of the inductor is the tricky part, the resistor is easier and can be done by ear.
If you are using a 10" driver on OB, there isn't much hope of getting any real bass. As others have said, that's a good driver to use with a helper woofer. I've done a few 6-10" vintage drivers on OB with the help of 15" woofers underneath. It's a great combo.
Enjoy the OB, there is no going back!
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Welcome to the dipole world ! Those look very nice. Within their bandwidth, they always bring an unmatched magic of music reproduction.
2011 was the year when I built my last boxed speakers, MTM WW and then no more. Since then it has been open baffle speakers in different configurations, mostly 2 ways and then even single driver in large L shaped baffles, always driven by tube amps…
The infection was so intense that I ended up gathering over a dozen of different full range drivers and equal number of tube amps…. (DIY is now an on going craziness)
The current dipole fever has graduated to horn loading in the front. It’s altogether an experience at another level….. But still “no box” !
2011 was the year when I built my last boxed speakers, MTM WW and then no more. Since then it has been open baffle speakers in different configurations, mostly 2 ways and then even single driver in large L shaped baffles, always driven by tube amps…
The infection was so intense that I ended up gathering over a dozen of different full range drivers and equal number of tube amps…. (DIY is now an on going craziness)
The current dipole fever has graduated to horn loading in the front. It’s altogether an experience at another level….. But still “no box” !
I made some ( closed box ) speakers that sounded hard and shouty, I to tried a resistor to reduce damping, but I found it dull, so I added a 1uf film cap across the resistor, and got a pleasant sound, and the combination was left in for some time. I eventually replaced it with a contour network that was better. A resistor seems to work well with aperiodic vents as well. I'm curious if the sound you like is because of the radiated back wave, or the almost none existent back wave coming back though the cone. Would you like an omni as much, or does the open baffle give more directionality to the front wave?
I made some open baffles and decoupled the drivers from the main baffle, but I grossly over estimated the bass.
I made some open baffles and decoupled the drivers from the main baffle, but I grossly over estimated the bass.