0 Members and 1 Guest are viewing this topic. Read 21002 times.
As a fan of O.B., please explain how even a 4 foot wide baffle can provide the dipole effect on a 60 Hz (20 foot long) sound wave.
Note that dipole fans might put down drivers in boxes, yet most use boxed subwoofers to make bass/deep bass. Surprised that I haven't read of any home owners here at AC using infinite baffles for subwoofers. Requires a space >10 times driver Vas behind the mounting wall (and avoid closets/rooms with hinged doors that could blow the cone out if slammed - or just add slow action door closers). Some use crawl or attic spaces. Garages can work too. Without box reinforcement it's not an efficient way to make bass, so often two to four 15 inch drivers are used.Search for "The cult of the infinitely baffled".
I think perhaps your intuition is leading you astray here, to understand it properly requires tackling a little OB theory. It's probably best addressed in the OB circle, but the short version is that at the sides of the baffle, the time delay between the front and rear waves is zero and hence they cancel, thus creating the dipole null. In front of the baffle, the time delay between the front and rear waves is non-zero, so they do not cancel; instead, the amount of cancellation progressively increases as frequency lowers below the frequency known as Feq - the result is a 6dB/octave reduction in SPL as frequency reduces (in free space). This time delay (and thus Feq) is determined by the geometry of the baffle but in the case of a flat baffle it's primarily the baffle width.HTH Happy New Year!
So I did a bit more research: Linkwitz has good conclusions (a few that I disagree with); Martin J. King has a nice write up that explains O.B. bass - basically you need brute force (such as the "right" higher efficiency bass drivers/multiple such drivers/floor reinforcement/bigger baffles) to make it work (as I thought), but he seems to ignore sound quality versus simple frequency response making O.B. seem more doable than realistic; and an insightful professional review of the rather large and quite expensive/reportedly impressive Jamo R909; but as we've seen here on AC overall it's hard to find unbiased opinions on this topic. I'm still confused as to why dipole designs that use discrete drivers almost universally use only a forward firing tweeter (while a few box speakers add a rear firing one to add "space/ambiance"), seemingly ignoring some of the basic premises of O.B.My conclusion is that largely boils down to the old subjectivity of audiophiles tastes, in this case of imaging.
Without box reinforcement it's not an efficient way to make bass, so often two to four 15 inch drivers are used.
Actually, IB is a really good way to make bass......box reinforcement reduces efficiency, it doesn't improve it......relative to IB. Your power amplifier doesn't have to work against the air spring within the box.But John is right.......IB would be even more scarce than OB in retail (or even domestic) environment. Dave.
Disadvantages to the IB? When a speaker is mounted in an enclosure, the air inside the enclosure acts like a spring against the speaker cone, and the resulting buildup in pressure provides mechanical damping and prevents excessive cone movement. But an IB installation does not use an enclosure, so the mechanical damping is poor, resulting in "hang-over" and lack of definition. The power handling of the speaker will also be compromised since the IB provides very little control over cone excursion.Can someone explain how designers overcome the above?
Hi folks, First, happy new year to all and wish the best. I have been reading this post on and off since yesterday with interest while I am working around my house and feel like this discussion more likely a comparison between the designs rather then answering the OP.Ultralight,There are number of different type of speakers and always will. But there are different type of consumers with a great objective matters in their head as well. Not everyone buy the speaker for the sound. One might buy the most expensive one to impress his friends or the nice looking one or a small monitors because of his wife and lastly might be for sound.You see more posts in OB circles, but if you look carefully you might be answer your own question that only 1% is a buyer and the rest are the DIYers or kit builders.Would you build up a retail business based on only 1% customer even though it is better?Sometimes people look at the audio business like voodoo. There is no difference between audio or anything else. No profit= No business and it does not matter what is good or bad.If you want to find the truth, and see which one works the best for you, then try to make few speakers and compare them with each other and see what you think. Do not worry about the money you spend because you are educating yourself. If you go out there and buy the best speaker, you would still loose a big amount of money when you sell them any way.Retail store would only sell you the ones that can make the most profit regardless it is good bad or however.I would say if the retail stores are trying to sell you only the best and out performance gears then how about we stop selling all three way passive designs and replace them with active regardless of type of speaker?
My take on the original question is that the box speaker, especially due to its smaller size which minimizes materials and shipping costs, is the cheapest way to make a speaker with a sound that is gratifying to the average buyer.
From a newbie perspective I would probably think box speakers dominate in the sense that they are easiest to set up and offer the most benefits for the typical household. Not everyone has a theater. Nor a dedicated two channel listening room with all the proper treatments. A small box speaker w/port is higher on the WAF than a larger IB/OB design. At least it's that way with my wife. And I would "guess" that a box speaker with a crossover would cover the frequency spectrum better at higher volumes. And the fact that there are more box speaker designs available to me than any other would be a deciding factor for me.
