Onhwy61...Agreed. You can get deep bass from small speakers: even from the 3/4 inch drivers in headphones. However, real LF sound at high volume, such as generated by an organ, is felt as much as heard. It takes large drivers to create the total sensation. |
In case of a knockdown, go to a neutral corner. |
Small drivers, like 3/4 inch headphones, are perfectly capable of LF response, but not at any volume. Because a small driver cannot move enough air to achieve useful volume at low frequency they are designed for other characteristics like mid/high reproduction. A 6 inch subwoofer is technically possible, but would be almost useless for any real audio system. |
I am a believer in large area LF drivers. My subwoofer system sports three 15" drivers and three 12" drivers. I have some small monitor speakers that will play almost as low in frequency, but there is obviously no comparison in the impact of the sound. Large diameter (area) LF drivers have an effortless quality to their sound. |
Onhwy61...A better analogy would be trying for high torque at low rpm from a small displacement engine. The small engine might produce lots of horsepower, but you won't win many drag races. |
Bluebull...Actually, the reason for 3-way speakers is good midrange: not good bass. |
I gather that the BOMB speaker utilizes heavy electronic equalization to flatten the response of drivers mounted in a too small enclosure. This is a neat idea, and one that Dr Bose came up with about forty years ago. I hope that patent issues have been resolved. The requirement for a powerful amplifier is less of a problem now than it was back then.
I am unimpressed by the reported difficulty of making the massive aluminum baffle (or whatever it's called). A numerically-controlled milling machine could knock these off at high speed to tight tolerances. Probably cheaper than a fine furniture grade wooden enclosure. |
Yep Gregm.
In a series crossover you first put the woofer and tweeter in series. That would, of course, pass all frequencies through both drivers, briefly until the tweeter burned out. To avoid this you put an inductor across (in parallel with) the tweeter, so that LF signal bypasses the tweeter. Similarly, a capacitor across the woofer keeps HF out of that driver. The value, mH, of the inductor, together with the inductance of the driver determines the high pass frequency of the tweeter.
In summary, the inductor relates to the tweeter, not the woofer.
Perhaps the terminology just got mixed up, but, I wonder... |
Karls...Can you explain what the "Linkwitz Transform" is. What I got from your website is that it is an equalization curve, of unspecified characteristics.
I guess Dr Bose beat Linkwitz by about 20 years. I described the concept as a "neat idea". I do not consider it a bandaid.
After more than four decades as an aerospace engineer, involved with manufacture of precision electromechanical equipment I assure you that I am not "completely ignorant" about NC milling machines. Also I never suggested that your aluminum slab was a bad idea. I like it, but it costs too much.
Lots of luck. :-) |
Karls...Thanks for the info. For your sake I hope there are enough people willing to spend $20K on speakers to make your effort worthwhile. If they go for multichannel you have it made.
You cite 10 dB as the boost. When Bose did it I seem to remember that the "inverse transfer function" (to use your technical jargon) was about 40 dB. Bose operated the drivers BELOW resonance because of the smoothness of the response in that range. I think he had driver resonance at about 200 Hz. Do you operate (mostly) below resonance? |
Sean...The original (sealed) Bose speakers are the only ones that I ever thought sounded good. All speakers generate output below the driver resonance, and many use equalization, but designers usually try to get resonance down as much as possible so as to minimize operation below resonance. The Bose idea was to deliberately push the resonance up, and equalize the hell out of the signal. I think that the speakers we are talking about here take somewhat the same approach, but not in such an extreme way as Bose.
Again I note that Bose's objective was not bass extension, but rather smoothness of the response curve because of the inherent smoothness of the drivers response when operating below resonance. LF roll off was taken care of by the drastic LF boost. |
Karls...As sean said, noone is comparing your speaker's sound to that of a Bose 901. (How could I...never heard yours). But, there seem to be some similarities with the design concepts of the ORIGINAL 901. Did you ever hear original Bose 901's? Not to be ridiculed, especially for 35 years ago. That's why your effort to develop the technology is of interest to us old farts. |
Karls...Is there a way to hear your speakers in New England? |
Karls...In a SERIES crossover, a WOOFER inductor? You need to explain this. |
Karls...Having messed around with crossovers for more than 40 years, I don't need your schematic to comprehend a series network.
Let me ask you...which driver's crossover frequency does the inductor determine? Shouldn't we call the inductor by the same name as the driver it serves?
The way I regard a series crossover is as a series connection of two elements...(1) Tweeter/Inductor parallel pair and (2) Woofer/Capacitor parallel pair.
(And, to Sean's point, a "parallel" crossover is a parallel connection of two series-connected elements).
Makes sense to me, but you evidently have some other way of looking at it. There is more than one way to skin a cat, which we can perhaps agree is a good idea. |
It's more than 40 years since EE101, and although, as an aerospace systems engineer (not an EE) I worked with a lot of fancy circuits since then I never actually designed a crossover network except at home for audio. I went to the only reference that I have handy at home to read up on series networks, Dickason's Cookbook, but I drew a blank. He says that the parallel configuration is "definitely preferable" and therefore does not discuss series further.
I have always been a "contrarian", so if everyone else is using parallel configuration I would probably look at series, as you have done. However, when you take the contrarian path you must be prepared to strike out a lot. But the grand slam HR makes it worth while. Your bases are loaded.
Peace
Ed |
Karls...Stop pontificating!
Of course LF energy flows through the inductor to the woofer. That's why it doesn't flow through the tweeter, so that the tweeter tweets and doesn't woof.
Suppose that you change the inductor value: make it smaller. The frequency at which its impedance equals that of the tweeter goes down, which means that the tweeter carries energy at lower frequency. Its crossover frequency has been changed. Now, has the woofer been affected? I don't think so, except for possible second order effects. Some current that formerly flowed through the inductor now flows through the tweeter, but a full range signal arrives at the woofer. Same as before. Now the capacitor across the woofer provides the low impedance path for HF and keeps it out of the woofer.
This whole silly discussion is about how to name the inductor. I claim that it should be called the "tweeter" inductor because it determines the tweeter crossover frequency. You like to call it the "woofer" inductor because it carries the spectrum of signal that is routed through the woofer (by the capacitor I might add).
Let's change the subject. Why do you think that a series crossover is superior to a parallel one, assuming that both are properly designed and optimized for the driver characteristics? I know of no reason why one should be better than the other, and I suspect that the recent flurry of series designs may be a marketing ploy. |
Karls...Thanks, I guess :-)
How many continuing education credits do I get for this?. Will there be a final exam? |
