noble@hobbes.ncsu.edu (Patrick Brewer) (03/14/91)
I have heard from various people (and read in the news groups) that you should never use box subwoofers with dipolar speakers. I believe the reasoning was that it would be hard to get them to blend in together. I was listening to some of Infinity's RS series three speakers. I got to talking to the salesman about Infinity the company, and of course he brought up their $75,000 speakers. I left with some documentation on them. From the description in the docs, it appears they are basically a bipolar system with a rather large subwoofer. In the docs they kept saying that they were bipolar down to 70hz. Who has heard any the Infinity IRS line of speakers? Do they work? Does this mean you can use subwoofers with bi-polar speakers? Thanks for any comments. -- ----------------------------------------------------------------------- Patrick W. Brewer President of CATT Program at NCSU noble@catt.ncsu.edu
sbhattac@cmcl2.NYU.EDU (Shankar Bhattacharyya) (03/20/91)
In article <10210@uwm.edu> noble@hobbes.ncsu.edu (Patrick Brewer) writes: > I have heard from various people (and read in the news groups) >that you should never use box subwoofers with dipolar speakers. I believe >the reasoning was that it would be hard to get them to blend in together. I think much of what is written about dipoles and woofers is nonsense. I am an esl enthusiast and own a pair of old Quads. I like their strengths so completely that I tolerate their faults without major complaint. A home-made woofer has alleviated the bass deficiencies somewhat. I do not ever expect to use a non-esl to produce sound above a few hundred hz. All esl owners are guilty of some such single-minded idiocy. I don't know my way around planar magnetic designs like the Magneplanars, or the subset of ribbons, such as the Apogees, or, for that matter, arrays of the Infinity driver. What I have to say applies basically to esl's. I will therefore restrict myself to esl's. I do not mean to suggest that it is easy to mate woofers with esl's. The problem is not that dipoles and non-dipoles do not mix (assuming a low crossover frequency). The problem is that many esl's are stunningly natural in the midrange, above about 100 hz, with no enclosure resonances to speak of (there are frame resonances, but these are usually not severe), and it takes a really good woofer to provide the same kind of uncoloured, resonance-free sound. The argument is made that box woofers cannot mate with dipoles because their radiation pattern is different. For a signal at 100 hz the wavelength in air is over 3 m, and as long as the dimensions of a woofer are small relative to 3 m, it is going to behave as a point source. It does not matter whether it is a dipole or a box woofer. A "dipole" is omnidirectional at low frequencies, as is a box. One caveat that I must offer is that tall, narrow dipoles radiate uniformly in the horizontal at low frequencies, but may well be fairly directional in the vertical at some frequencies of interest, eg. at 100 hz. A dipole woofer would not cure that, unless it were pretty much coincident with the main panel, or centered in it, as is the case for some designs. The former is not exactly feasible, the second has various problems. The argument is also made that dipoles are fast, and box woofers cannot be as fast. Also nonsense. Even the esl's are not particularly fast. Many small tweeters are faster, and small ribbons usually are. Even if they are, it is irrelevant, since woofers don't have to reproduce high frequencies, assuming proper choice of crossover frequency. Recent discussions on rec.audio have beaten this into the ground, and I do hope that people are convinced. I, too, am tempted by the purist elegance of a dipole subwoofer. I spent some time doing paper design of such an animal. But I submit that this is not a sensible enterprise, insofar as real performance is concerned. - Shankar
sbhattac@cmcl2.NYU.EDU (Shankar Bhattacharyya) (03/25/91)
>In article <10210@uwm.edu> noble@hobbes.ncsu.edu (Patrick Brewer) wrote: >> I have heard from various people (and read in the news groups) >>that you should never use box subwoofers with dipolar speakers. I believe >>the reasoning was that it would be hard to get them to blend in together. In a response I wrote: >I think much of what is written about dipoles and woofers is nonsense. .... rest deleted ..... It struck me afterwards that the post may have sounded dismissive towards Patrick's question. It was not so intended. I take his question entirely seriously. I do, however, remain dismissive towards much that is said and written about matching dipoles with woofers. A lot of it requires suspension of belief in physics. My basic point, to Patrick, and anyone else with the same question, is that they should stay aware that much of what they will hear and read on the subject is wrong. The common wisdom is at least limited on the subject of whether box woofers can be mated with dipoles, and, on the subject of why there are problems, the common wisdom is wrong. - Shankar