Oh, boy...!
And when I started this thread, the whole world seemed so simple...
I am starting to seriously doubt a OB system is the choice for me at the moment (spouse acceptance factor), but I'm certainly learning a lot in here. Much more then I thougt there was to it.
Then again, I suppose this is still better than starting a diy project and never being pleased, simply because the knowledge wasn't there at the beginning.
Where have all you geniouses learned your stuff about theory and practice. It must have taken a lot of money and time...?
Jennice
And when I started this thread, the whole world seemed so simple...
I am starting to seriously doubt a OB system is the choice for me at the moment (spouse acceptance factor), but I'm certainly learning a lot in here. Much more then I thougt there was to it.
Then again, I suppose this is still better than starting a diy project and never being pleased, simply because the knowledge wasn't there at the beginning.
Where have all you geniouses learned your stuff about theory and practice. It must have taken a lot of money and time...?
Jennice
I have tried almost all the options there are for my drivers including the same size baffle as Kuei has (with very similar driver as well), but the smaller baffle with active eq simply sounded better, that's all I'm interested in. So for me it wasn't just a matter of compromise. The larger baffle (65*105 cm) had a much worse off axis response wich reminded me a bit to the Quad ESL's, not my cup of tea, I like to listen to music at any place in my room, it occurs maybe ones or twice a week that I'm actually listening at the sweet spot. If it doesn't sound good in the whole room than it's not a penny worth to me.
Hi,
Highly personal thing, "sounds better".
Funny you would call onto the Quad ESL... I'm allways calling it "A Quad ESL with cojones...." ;-)
Actually, for that true omni's or semi-omnis are best, so the polar opposite of what I'm trying to get with open baffles.
Sayonara
Sjef said:
Highly personal thing, "sounds better".
Sjef said:
Funny you would call onto the Quad ESL... I'm allways calling it "A Quad ESL with cojones...." ;-)
Sjef said:
Actually, for that true omni's or semi-omnis are best, so the polar opposite of what I'm trying to get with open baffles.
Sayonara
rcavictim said:
here are those drivers.
http://www.matelectronics.com/acatalog/Speaker___Woofers.html
Variac,
I have to take back my short side / long side analogy because I think there is some boost resulting from that long side. The added distance results in some reinforcement of the front wave by the back because the waves are closer to being in phase than out of phase.
I traded emails with SL last night and got more into the math on his site. The formula f = .17 * v/D was taken out of context, add is used to determine driver requirements to obtain a specific SPL. The D is radius, but f is just the frequency where excursion and output equal that of a sealed box, not the point where roll off starts.
My visualization of how this roll off thing works was wrong. The back wave isn't sneaking around and cancelling at the edge. If you listen at the sides everthing is cancelled (to the extent front and back output are equal) NO MATTER HOW WIDE THE BAFFLE. It's 2 waves that are out of phase and as long as you are the same distance from the source of both they net to 0.
When you go to the front of the baffle it's still 2 waves that started out of phase, but the rear wave has to travel further. The closer the 2 waves are to being directly out of phase the more they cancel. The lower the frequency (the longer the wavelength). the closer the 2 waves are to being directly out phase and more cancellation results.
At higher frequencies, where the extra distance the rear wave travels results in the waves being directly in phase or out of phase response peaks and nulls occur. That's why a driver centered on a circular baffle would be the worst possible setup. If a speaker was a perfect point source, you would have almost total cancellation or doubling of sound at different frequencies accross the spectrum. To minimize this effect you mount the driver off center, so the a sound is travelling infinite different distances to get to your ear.
Where does this leave us?
First,
The spreadsheets and formulas can only give us an estimate of where to start. As Kuei Yang Wang stated, surface area of the baffle is important, but if you take it to too much of an extreme (a very tall, very narrow baffle) the extra surface area will have little added benefit because most of the rear wave will be going around the sides to get to your ear. Everything from baffle size, to driver diameter and room placement will affect the outcome, so experiment first with cardboard baffles in room.
Second,
Measuring a dipole at 1m is a waste of time for 2 reasons (I'll assume the driver is in the center of a circular 2m radius baffle for simplicity and to exagerate the points). 1. The extra distance for the backwave to travel is greater than in the far field because it has to get back to the middle. At 1 meter the extra distance the rear wave travels is over 3.2m and at 4m the extra distance is only about 2.5m . This will result in a significant difference in the OB rolloff point. 2. At 1m, the back wave sound is over 6db lower than the front wave due to the extra distance travelled. At 4m the SPL difference is only about 2db.
Third,
At your listening position, side baffles that are folded back gives you a wider effective baffle because it increases the distance travelled by the rear wave. Taken to the extreme (the entire side folded back 90 degrees), it doubles the effective width. While seemingly advantageous, it does bring up other issues of cavity resonances, dispersion, and room interaction (They aren't silent at the sides anymore.).
Fourth,
Rear wall distance is more of a factor than boxed speakers. The rear wave is in play with dipoles. The closer the speakers are to the rear wall, the more the reflections off of it are part of your response because they are higher in SPL due to less additional distance travelled which also affects the phase relationship with both the rear and front wave output.
While all of this seems intimidating due to the lack of hard numbers that you can calculate for a boxed speaker, I highly encourage everyone to experiment with dipole. I made my first dipole less than 9 months ago, and have made over 10 different pairs most of which were sold. IMHO each sounded better than any boxed speaker I ever owned. I did no measuring except by ear using a tone generator and music.
Experimenting with dipole is fast and easy using cardboard and tuning and tweaking is just as simple because everything is open. You can literally build a test speaker in a few minutes with a piece of cardboard, tape and a knife. Plus you have many different things you can use to tune the response ranging from changing the baffle size and shape, changing placement, to damping the rear wave with polyfill or open cell foam.
I've made dipoles for desktops, ones tuned to sound great with the bottom butted up against the rear wall, and even an OB line array for a bar with a baffle consisting of a flat piece of plywood hung from the ceiling. It's all much easier to experiment, build and tune than a boxed speaker and I, along with everyone I've shown mine, think they sound better than a box.
Sorry about the long post, but I'm still an OB dummy and wanted to share what I've learned.
I have to take back my short side / long side analogy because I think there is some boost resulting from that long side. The added distance results in some reinforcement of the front wave by the back because the waves are closer to being in phase than out of phase.
I traded emails with SL last night and got more into the math on his site. The formula f = .17 * v/D was taken out of context, add is used to determine driver requirements to obtain a specific SPL. The D is radius, but f is just the frequency where excursion and output equal that of a sealed box, not the point where roll off starts.
My visualization of how this roll off thing works was wrong. The back wave isn't sneaking around and cancelling at the edge. If you listen at the sides everthing is cancelled (to the extent front and back output are equal) NO MATTER HOW WIDE THE BAFFLE. It's 2 waves that are out of phase and as long as you are the same distance from the source of both they net to 0.
When you go to the front of the baffle it's still 2 waves that started out of phase, but the rear wave has to travel further. The closer the 2 waves are to being directly out of phase the more they cancel. The lower the frequency (the longer the wavelength). the closer the 2 waves are to being directly out phase and more cancellation results.
At higher frequencies, where the extra distance the rear wave travels results in the waves being directly in phase or out of phase response peaks and nulls occur. That's why a driver centered on a circular baffle would be the worst possible setup. If a speaker was a perfect point source, you would have almost total cancellation or doubling of sound at different frequencies accross the spectrum. To minimize this effect you mount the driver off center, so the a sound is travelling infinite different distances to get to your ear.
Where does this leave us?
First,
The spreadsheets and formulas can only give us an estimate of where to start. As Kuei Yang Wang stated, surface area of the baffle is important, but if you take it to too much of an extreme (a very tall, very narrow baffle) the extra surface area will have little added benefit because most of the rear wave will be going around the sides to get to your ear. Everything from baffle size, to driver diameter and room placement will affect the outcome, so experiment first with cardboard baffles in room.
Second,
Measuring a dipole at 1m is a waste of time for 2 reasons (I'll assume the driver is in the center of a circular 2m radius baffle for simplicity and to exagerate the points). 1. The extra distance for the backwave to travel is greater than in the far field because it has to get back to the middle. At 1 meter the extra distance the rear wave travels is over 3.2m and at 4m the extra distance is only about 2.5m . This will result in a significant difference in the OB rolloff point. 2. At 1m, the back wave sound is over 6db lower than the front wave due to the extra distance travelled. At 4m the SPL difference is only about 2db.
Third,
At your listening position, side baffles that are folded back gives you a wider effective baffle because it increases the distance travelled by the rear wave. Taken to the extreme (the entire side folded back 90 degrees), it doubles the effective width. While seemingly advantageous, it does bring up other issues of cavity resonances, dispersion, and room interaction (They aren't silent at the sides anymore.).
Fourth,
Rear wall distance is more of a factor than boxed speakers. The rear wave is in play with dipoles. The closer the speakers are to the rear wall, the more the reflections off of it are part of your response because they are higher in SPL due to less additional distance travelled which also affects the phase relationship with both the rear and front wave output.
While all of this seems intimidating due to the lack of hard numbers that you can calculate for a boxed speaker, I highly encourage everyone to experiment with dipole. I made my first dipole less than 9 months ago, and have made over 10 different pairs most of which were sold. IMHO each sounded better than any boxed speaker I ever owned. I did no measuring except by ear using a tone generator and music.
Experimenting with dipole is fast and easy using cardboard and tuning and tweaking is just as simple because everything is open. You can literally build a test speaker in a few minutes with a piece of cardboard, tape and a knife. Plus you have many different things you can use to tune the response ranging from changing the baffle size and shape, changing placement, to damping the rear wave with polyfill or open cell foam.
I've made dipoles for desktops, ones tuned to sound great with the bottom butted up against the rear wall, and even an OB line array for a bar with a baffle consisting of a flat piece of plywood hung from the ceiling. It's all much easier to experiment, build and tune than a boxed speaker and I, along with everyone I've shown mine, think they sound better than a box.
Sorry about the long post, but I'm still an OB dummy and wanted to share what I've learned.
Kuei and Raka
I was referring to the Quad ESL (the 57) because I have owned a pair of them. Not very enjoyable outside the sweetspot, really started to hate them for that.
I happen to like the smaller baffles WITH active correction. I'm using a DEQX dsp unit as crossover/correction and that's make a whole lot of a difference. Without this or any other active crossover/eq a small baffle wouldn't do any good if you want to use from 110 Hz upwards like I do.
Just remeber that EVERY speaker system is a compromise. I have done my compromises. I know how I can can make them sound better fo classical music or jazz, but it also has to sound good on Rammstein when I'm in the mood for it, so compromises have to be made. What sounds best ? Depends on what music you like. I like to play Cannonball Adderly as well as I like to play Rammstein when I'm in the mood for it. I like Indian sitar music as much as I like bigband Jazz. etc etc. and I like to listen to it as much as I'm sitting in a chair as when I'm doing the dishes.
I'm listening to music all day but I don't see myself sitting in a chair all day. And when I'm not sitting in a chair doesn't mean I don not listen.
But enough on that, whe were discussing open baffles for dummy's weren't we ?
I was referring to the Quad ESL (the 57) because I have owned a pair of them. Not very enjoyable outside the sweetspot, really started to hate them for that.
I happen to like the smaller baffles WITH active correction. I'm using a DEQX dsp unit as crossover/correction and that's make a whole lot of a difference. Without this or any other active crossover/eq a small baffle wouldn't do any good if you want to use from 110 Hz upwards like I do.
Just remeber that EVERY speaker system is a compromise. I have done my compromises. I know how I can can make them sound better fo classical music or jazz, but it also has to sound good on Rammstein when I'm in the mood for it, so compromises have to be made. What sounds best ? Depends on what music you like. I like to play Cannonball Adderly as well as I like to play Rammstein when I'm in the mood for it. I like Indian sitar music as much as I like bigband Jazz. etc etc. and I like to listen to it as much as I'm sitting in a chair as when I'm doing the dishes.
I'm listening to music all day but I don't see myself sitting in a chair all day. And when I'm not sitting in a chair doesn't mean I don not listen.
But enough on that, whe were discussing open baffles for dummy's weren't we ?
Sjef said:
You are absolutely correct, but it happens that I listen different, didn't mean better, of course. I have different compromises, and it's good to see that we have different solutions.
One day I will try one configuration of the nice list Kuei has on this forum, the one of the big baffle fullranged. Now I'm very fond on Linkwitz site, but maybe this will change in the future. BTW, Linkwitz has described so well his theories that seems to be imposible not to design the Orion. Big thanks to Sigfried for sharing
Jennice said:
Don't worry. There are hope. As you said, you can have a top and mid in ob, and a closed box for sub. It does not quite get as good as ob sub, but close
Bastanis have a kit called prometheus (http://www.memphis-highend.de/diy/prometheus_en.htm)
If you build the sub integrated with the baffles, it dont take up more space than an ordenary boxspeaker. And it sounds good too.
Bjørn
Attachments
I'm using two 2205 16 Ohm version per w-baffle. The w-baffle is always used with two woofers. this way you will get force cancelation. Works like a charm, the whole 'enclosure' is almost totally free from vibration.
At first I have build the w-baffle with 18mm multiplex. It still had a little audible vibration on the sides.Later on I added a layer of 4mm bitumen and a layer of 8mm multiplex on the sides and now it's very silent. Still using them. Tried a lot of other bass systems over the years but keep coming back to this one. It's not as 'free' sounding as a flat baffle but has more extension on the bottom end. It's also not as 'punchy' as a boxed woofer but is has a lot les colouration. It falls just somewhere in between. Open baffle sound with punch, with it's own darwbacks offcoarse (A loudspeaker without compromise will never ever excist I'm afraid) ) but afterall very good.
At first I have build the w-baffle with 18mm multiplex. It still had a little audible vibration on the sides.Later on I added a layer of 4mm bitumen and a layer of 8mm multiplex on the sides and now it's very silent. Still using them. Tried a lot of other bass systems over the years but keep coming back to this one. It's not as 'free' sounding as a flat baffle but has more extension on the bottom end. It's also not as 'punchy' as a boxed woofer but is has a lot les colouration. It falls just somewhere in between. Open baffle sound with punch, with it's own darwbacks offcoarse (A loudspeaker without compromise will never ever excist I'm afraid) ) but afterall very good.
Funny, just realized this is an 8 year old threat and after trying lots and lots of drivers since then (Sold a lot of them and still have a closet full of them left) I'm still listening to the same system for almost 10 years by now.
This can only mean two things. Fist, I'm a lazy bastard. Second, it's that good.
The truth is somewhere in the middle as always.
This can only mean two things. Fist, I'm a lazy bastard. Second, it's that good.
The truth is somewhere in the middle as always.
OB
Hi there S: Thanks to J for starting an interesting thread on OB. A couple of years ago I too got caught-up in the OB addiction. The sound seems to fill the room, rather than comming from a box. Bass notes you feel rather than hear. I think too many people* get caught-up in the theoritical complexities, trying to optimize every possible parameter, and not getting anything built for listening (and if you are desposed , measure to your hearts content). I think we talked J out of DIY, and scared her and spouce away, with the technical aspects; rather than getting started with some EBAY drivers, Hone Depot/Lowes precut panels and enjoying listening.
*(I'm a guilty one who has HR simmulated TH's till dawn, and never built an easy one.)
and Sjef: no you do not come across as lazy and I appreciate your comments
...regards, Michael
Hi there S: Thanks to J for starting an interesting thread on OB. A couple of years ago I too got caught-up in the OB addiction. The sound seems to fill the room, rather than comming from a box. Bass notes you feel rather than hear. I think too many people* get caught-up in the theoritical complexities, trying to optimize every possible parameter, and not getting anything built for listening (and if you are desposed , measure to your hearts content). I think we talked J out of DIY, and scared her and spouce away, with the technical aspects; rather than getting started with some EBAY drivers, Hone Depot/Lowes precut panels and enjoying listening.
*(I'm a guilty one who has HR simmulated TH's till dawn, and never built an easy one.)
and Sjef: no you do not come across as lazy and I appreciate your comments
...regards, Michael
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