Charles1dad has given the most complete answer. The size of the cone relates to mass, the drivers motor structure effects the final product. It is possible to have a 15 that is very fast indeed... How well most 15 inch play mid range is another story. Also as Charles stated, the larger the cone area, the more air it moves. Depending on room size this can be very satisfying. Alot of mass often does not work well in small rooms. Off hand Legacy comes to mind, the big guys move lots of air.
There are several 4" drivers that play down to 50 hz, so can do a very convincing job of covering the entire vocal region, when you get above most 6.5" and a few 8, they just don't go out well enough into the mid range to blend with most tweeters.... This is in general, not an absolute. I have heard quite good 15" 2 ways.
I hope this helps. Tim |
Hi Waj4all,
It is possibe for a small driver to play low bass, but not practical. I have seen 1 4 inch capable of hitting the 20's in my time, it was 81db sensitivity. To get the sensitivity up, you need motor structure, too much motor vs mass and you have to qms/mass, No Q, no low bass. It is a real balancing act. Look hard, you will see high sensitivity 6 to 8 inch drivers, won't go down...maybe to 80 or 100 hz or so, but you won't find drivers this size with real sensitivity (say 95) playing any real bass. You start adding mass to get the final Q up(qts/qtc) and sensitivity drops. That is why most 6 inch drivers that are capable of bass in the mid 30's are normally in that 85 to 86 db sensitivity range.
So to dance around your question... as Charles stated, he uses 2, 6 inch drivers in the mids to get the cone area up, but in my opinion, no it is not absolutely necessary to get large cone area to create realism in the midbass, but you do have to have drivers that properly matchs the midbass response with the bass & midrange and depending on your load and sensitivity have an amp to drive it.
creating a flat response in a driver is not too tough, how much frequency that flat response covers, sensitivity and Low end all combined, can be very tough.
Tim |
Hi Drew,
I might possibly come up with the spec on the 4" I quoted, maybe even a driver, its been along time back, but I remember well using these in a line source and getting output -3db @ 27hz. I realize that I speak in generalities so that all understand, whether a newbee or seasoned vet and you are laying down the math, but I assure you, the above is true.
>Physics dictate high displacement for realistic sounding listening levels and geometry precludes getting that from small numbers of small drivers, although you can get closer with a folded backhorn than any other technology.
This is a true statement, but needs a context, Are you saying that a smaller driver cannot be used as a midbass?
say 80 to 250 hz? Or what are you saying with this statement? |
Drew, thanks for the explanation of your statement. I think there are a few exceptions, but overall, I seem to never really find fault in your logic.
Tim |
Hi Waj4all,
>Why is it, then, that so many of the ultra-expensive, state of the art designs employ single or doubled small-coned mid-woofers crossed-over, sometimes, as low as 100hz? Are we missing something, here?
Not in a 2 way, I can think of 1 or two drivers that can be crossed at 400 or so as a 2 way, these are quite rare, there are a handful that can be crossed at 1k to 1.5K and several @ 2k or above.
I have built a few 3 ways that employed a 10" up to 100, then a 6 covered 100 to 2500 and a dome above that.
So in a 3 way or higher a 6 inch or larger makes since at that 100hz mark. |
Hi Waj4all,
This is why I thought you were talking about a 2 way or 3 way, no mention of a subwoofer here or prior, only mid woofers:
>Why is it, then, that so many of the ultra-expensive, state of the art designs employ single or doubled small-coned mid-woofers crossed-over, sometimes, as low as 100hz? Are we missing something, here? |
Hi Waj4all, first about the misunderstanding, no harm, no foul, i've never claimed to be the sharpest tool in the shed. I was listening just a couple of nights ago to a 15 inch woofer that had a highly modified 3x7 piezo...a 2 way and it was wonderful and imaged like crazy(no crossover). One issue with your statements that still tends to throw people off. Subs are typically crossed at 100hz or lower, above that point and they can become directional. Next, as a midbass, I have used a 4 inch once, I have used a 5 inch once{once I used 4-5inch), I have used a 6 to 7 inch several times. There is just no doubt that cone area matters, but I've never built with an 8 or above as a midbass driver, they were always used as a woofer for a 2, 3 or 4 way. You must consider matching sensitivies, box size needed, crossover slopes and any compensation needed.
This is where my experience lies. |
