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I regard the "subwoofer" not as a separate speaker system, but as part of the main speaker system...the part that the manufacturer left out because of size and cost. Naturally this means that every main speaker has its "own" subwoofer driven by the same channel signal with appropriate electronic crossover.
The reasons for having a subwoofer are (1) to use a larger diameter driver appropriate for LF (or, the same thing, to enable use of a smaller driver for the main woofer) and (2) keep the LF cone excursions out of the woofer.
I think that the issue of "slow" subwoofers is overdone. Low frequency sounds are inherently "slow" and the subwoofer is properly reproducing them. For example: a sixteen foot organ pipe is slow...its sound develops slowly to its full volume/tone. A tuba is slower than a piccolo. |
Newbee...SW crossover frequency depends very much on what your particular subwoofer can do. Based on quite a bit of experementation I have also concluded that the type of music being played also has a big effect, so I have crossovers that enable me to change frequency with the twist of a knob. For some classical music I let the Maggie 1.6 take it from 50 Hz up. For some massive pieces, such as theatre organ, I run the SWs up to 200-300Hz, and there is no doubt that it is better.
An interesting test that I have run is to play white noise and sweep the X/O between 40 Hz to about 400 Hz and higher. With my rig there is no audible change in the sound up to about 300 Hz, which tells me that I have the levels well matched and that the SW (a 12" and a 15" for each channel each driven by their own amp) are not out of gas at 100 Hz. Of course my SW systems are custom designs that have been extensively tweeked, and my results may differ from those using off-the-shelf SW. |
Rauliruegas...I read the links you recommended, and find little with which to disagree. In particular, discussion of the "slow bass" myth is exactly consistent with what I said in my earlier posting. I have been designing, building, tweeking subwoofers for several decades.
The overlaping X/O frequencies for SW and Mains is not important in my opinion. There will be some overlap anyway because of the finite filter slopes, and some electronic crossovers make provision to boost or cut response at and around the X/O frequency so as to optimize integration.
My present SW design is taylored for use with planar speakers, Maggie MG1.6. To that end I used a lot of cone area so that excursion would be small like the planars, and I stacked the 12" and 15" SW drivers and located them directly (several feet) behind the Maggies, so that the SW "plays through" them.
"Integration" is (dare I say it) perfect. |
Rauliruegas...It happens that I have a spectrum analyser in my system, and can therefore give sure answers about frequency response.
The Maggie 1.6 low end rolls off rapidly around 40 Hz, which is exactly what Magneplanar says. For most music their low end sounds better than you would expect because it is very smooth, and the planar format means that SPL is quite uniform throughout the room (at least in my room).
My SW systems exhibit flat SPL to 1250 Hz. (And they are flat to 20 Hz). This is when driving them with a full range white noise signal. However, if you drive them with a swept-frequency tone, distortion becomes evident around 400 Hz. So the SPL is there at 1000Hz, but some of it is harmonic distortion.
Advocates of small drivers may find it hard to believe that a 15" driver can do 400 Hz or higher. Actually it is not the size (mass) of the cone that matters, but rather the ratio of the motor power to the cone mass. My 15" driver has a 4" voice coil, and about 20 pounds of magnet, driven by 600 watts, so it is not at all surprising that it can perform well up to 400 Hz. I also have a set of JBL LE15A drivers (used in some of their classic top-of-the-line systems) and they are good for 800Hz (but they won't do much below 30 Hz).
About the 200 to 300 Hz crossover...this is just for certain types of music, most notably theatre organ, but also brass bands and massed choral music. There is no way that three MG1.6 can deliver the impact of six big cones. |
4yanx...The integral subwoofer that you describe in the Vandersteens is a very good approach. What you end up with is a four-way system. A passive crossover for a three way system is a tough design job, and a four way would be worse, hence the use of the electronic crossover and separate power amp. Also the inductor and capacitor values that would be needed for a passive SW crossover are large and expensive. Last, but not least, the all-in-one aspect has definite cosmetic benefits.
The only drawback that comes to mind is that the SW enclosure size is probably less than what you could use for a separate SW. When I built a tower system with integral powered SW I used the "isobaric" design (two drivers mounted one behind the other in a short tunnel) so as to cut the enclosure volume requirement in half. |
Rauliruegas...At first I took the same approach as you, (and everyone else it seems) and I tried to find the a frequency for "best quality sound reproduction". I never seemed to get it right. It took me many years to realize why: there is no one best X/O frequency, at least for my system. It depends on the kind of music being played. I do not use the X/O frequency as a tone control. I have my system tweeked up so that there is no audible or measurable (RTA) change when I sweep the frequency. But with music that has heavy LF the six 12" and 15" subwoofer cones have the "punch" that folks say is missing in Maggies. |
Rauliruegas...My experiments with SW crossover frequency has led me to the conclusion that, at least for my speakers, there is no one "correct" frequency. My main speakers, MG1.6, are good to 40 Hz, and my custom SW systems are good to 400 Hz, so I am free to vary over quite a range. The best X/O frequency depends on the type of music, and how loud I play it. Classical chamber music calls for 40 Hz and Organ music sounds best at 200-300 Hz. These are extreme examples, most of the time I run around 80 Hz. My point is that the crossover electronics should permit the frequency to be easily changed, and one should not be afraid to adjust it as freely as the volume control. |
Rauliruegas...I forgot to mention that when I sweep the X/O frequency I am listening to and observing a white noise signal. Music is another story, which, of course, is the reason that I vary the frequency. My ability to sweep the X/O frequency without audible effect may not be usual, but my claim is that it indicates that my custom designed SW systems are well matched to the MG1.6 speakers. |
Rauliruegas...Not surprising to me. My subwoofer systems, each consisting of a 15" and a 12" driver, has the centerpoint of the two drivers about 40 inches above the floor. This puts them near centered behind my Maggies, which was a design objective.
By the way, I also elevated the Maggies by about six inches, and that helped too.
I have always been a fan of elevating speakers, including suspending them from the ceiling if the wife permits. (They usually don't). |
Sirspeedy...I too am familiar with the idea that low frequencies are non-directional. Absolute BS! |
Sirspeedy...I have no idea who Dave Wilson might be, and can only speculate as to why he might promote this myth which is only too easy to disprove simply by listening. |
Sirspeedy...Do my three subwoofer systems,(for the front channels) each having a 12" and a 15" driver qualify me as having some first hand experience with subwoofers?
Upon further consideration I realize that a single subwoofer may be appropriate if your source is vinyl. Because of problems with vertical groove modulation it is common for LF signal to be blended to mono, which is horizontal groove modulation.
Have a nice day.
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Rauliruegas...I basicly agree with your argument. But please note that I do not cross over at 80 Hz (as you state). After many frustrating years of trying to find the "right" X/O frequency I have realized that there is no one right frequency, even for a particular system. It depends on the music. I have therefore chosen an electronic crossover where the frequency is easily adjusted with the twist of a knob.
Where the music has little LF content, I push the X/O down to 40 Hzm or so. My Maggies are fine at 40 Hz. Where the music has a great deal of LF content (typically organ) I push the X/O up as high as 200+ Hz. I can do this because my subwoofer systems include a 12" NHT woofer that is used up to 800 Hz in their systems, so my SW systems are not band-limited on the high end. (They actually go up to about 400 Hz without audible distress). 80 Hz is just where I am set before these music-sensitive adjustments.
Another feature of my system that I think is good is the placement of the subwoofers as a line array (if 2 drivers make a line) behind the Maggies so that all the sound originates from the same place and with planar dispersion characteristics.
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Rauliruegas...No doubt that I said that in the past. But I get smarter every year! Don't we all. It was really a great relief that I don't need to worry about finding the "golden" X/O frequency. |
