only large drivers produce the bass

WerTicus · « **on:** 10 Dec 2003, 02:11 pm »

I have heard it several times on this site (and others)... the notion that to get 'true' smooth, sexy and effortless bass you must not use a driver that is smaller in size than the wavelength its trying to produce. (big driver not doing much work vs little driver going nuts to get similar result)

I have a 6.5" vifa driver in a 50 litre box with two x 3 cm wide x 196.5mm long ports and it's f3 is 37hz... and its pretty nice sounding... makes me wonder what im missing!

But it also makes me wonder would this 'rule' apply to two smaller drivers working together?

For example would a 12" driver sound better than two 6.5" drivers? Or dosnt it work like that... since the total area of the two is 13" not to mention the fact that they would probably have more power for their weight. But would they still be this same 'effortless' bass?

Currently im looking into a 3 way design with a 2.5" mid range and a 10" woofer... so if i could have two 6.5"s instead would that be 'better' or would there be tradeoffs and what would they be? (besides costs!)

JoshK · « **Reply #1 on:** 10 Dec 2003, 02:24 pm »

Well just in terms of surface area, 6.5" drivers have 90.5 in.sq surface area while a 12" driver has 308.4 in.sq. Takes 3.4 6.5" drivers to make up for the surface area of one 12" woofer. Now, this is just an approximation because what really matter is the change in volume of the conic surface area when the driver moves and the air displaced.

JohnR · « **Reply #2 on:** 10 Dec 2003, 03:15 pm »

Hm, Werticus I think you may have got something mixed up somewhere -- "you must not use a driver that is smaller in size than the wavelength its trying to produce" would mean that you would need a 20-foot driver to produce 50Hz...

But, to the question, there are two issues, the first is volume displacement which as Josh says is almost certain to be significantly larger for a single 12" than for two 6.5" drivers. Apart from the 3-4 times larger surface area of a 12" driver it is likely to have a higher Xmax as well. Volume = area (Sd) x Xmax.

Now, I personally happen to think that larger drivers sound more natural than smaller ones. I attribute this to the lower excursion needed to produce a given SPL, and surmise this to be due to reduced intermodulation distortion (because the drivers moves a smaller distance) and more headroom. I have no proof, but so far it's proved to be a good working theory -- small (and I consider 6.5" small... no jokes please) drivers sound like small drivers.

Sooner or later someone will do you the favor of working out that for a given SPL you need only a certain amount of power/Sd/Vd/whatever. Almost always they forget that you need a minimum 20 dB of dynamic headroom, and preferably more, much more. To put it another way, smaller drivers will sound "strained" much more easily than larger ones, because they are compressing the dynamic peaks. It doesn't mean they sound bad, I listen to 5" drivers regularly but the dynamic limitations are obvious.

HTH

Carlman · « **Reply #3 on:** 10 Dec 2003, 03:19 pm »

I have always "felt" larger drivers as much as heard them. In my experience, a 10" driver has more impact than 2 or 3 6" drivers. So, I think you'd get more of a physical punch from larger drivers.... which I've always enjoyed. 10 to 2.5" seems like a big jump for a crossover. Good luck!

WerTicus · « **Reply #4 on:** 10 Dec 2003, 03:27 pm »

okay thanks for the info guys... i want a nice 'kick' to those drum beats so i think the 12" will be the go... and a 6.5 and a 2.5 and a 1"

4 way... yay.

JohnR · « **Reply #5 on:** 10 Dec 2003, 03:37 pm »

Don't forget that an 8/10 design that you can afford and build is way *way* better than a 10/10 design that never gets finished...

IOW, personally, I would recommend sticking with a published design.

audiojerry · « **Reply #6 on:** 10 Dec 2003, 07:01 pm »

Quote

okay thanks for the info guys... i want a nice 'kick' to those drum beats so i think the 12" will be the go... and a 6.5 and a 2.5 and a 1"
4 way... yay.

If only it were that simple. More drivers means more crossover complexity, more phase issues, more coherency problems, etc. Another consideration is damping. A 12" might go lower, but it might not give a nice 'kick', as this relates to transient speed. There are plenty of sloppy sounding subwoofers that go plenty low but have no discernable starting and stopping point. Not all drum beats are that low in frequency, and you want a driver that can define the 'kick' with precision instead of a dull thump.

JoshK · « **Reply #7 on:** 10 Dec 2003, 07:14 pm »

Quote from: JohnR

Apart from the 3-4 times larger surface area of a 12" driver it is likely to have a higher Xmax as well. Volume = area (Sd) x Xmax.

That is what I was trying to say...

jcoat007 · « **Reply #8 on:** 10 Dec 2003, 07:25 pm »

I have dual Vandersteen subs that use 3 - 8" drivers each. According to Vandersteen, the 3 - 8" drivers have the same surface area as a single 14" driver but they move much faster than a large woofer can.

With the adjustable Q, the damping factor can be adjusted for different music types or tastes. I have found this to be an excellent sub for all kinds of music, and I adjust the damping often since my taste vary so much and so often.

YMMV

Steve

BrunoB · « **Reply #9 on:** 10 Dec 2003, 07:28 pm »

Quote from: audiojerry

If only it were that simple. More drivers means more crossover complexity, more phase issues, more coherency problems, etc. Another consideration is damping. A 12" might go lower, but it might not give a nice 'kick', as this relates to transient speed. There are plenty of sloppy sounding subwoofers that go plenty low but have no discernable starting and stopping point. Not all drum beats are that low in frequency, and you want a driver that can define the 'kick' with precision instead of a dull thump.

If we would have four small drivers , connected such that they would have the same impedance as one large driver (connect in parallel two pairs (two small drivers connected in serie) ), then I think that we could avoid crossover complexity.

Bruno

doug s. · « **Reply #10 on:** 10 Dec 2003, 08:51 pm »

Quote from: Carlman

I have always "felt" larger drivers as much as heard them. In my experience, a 10" driver has more impact than 2 or 3 6" drivers. So, I think you'd get more of a physical punch from larger drivers.... which I've always enjoyed. 10 to 2.5" seems like a big jump for a crossover. Good luck!

i have a pair of old spectrum 410 floor-standers in my bedroom - these use a 10" woofer crossed over to a 1" tweet. 28hz-20khz +/-2db. really quite nice sound from these relatively inexpensive ($800 circa 1988) speakers. i tink the key is in the implementation, re: driver matching...

doug s.

nathanm · « **Reply #11 on:** 10 Dec 2003, 10:27 pm »

A kick drum produces more than just bass and the 'fast' attack part of the sound most likely is not going to be produced by the woofer anyway. (Especially if you are a fan of Rex Glissen-produced albums in which case the kicks will come almost entirely from the tweeters.

) I would have to say that it helps to have big drivers puffing air at you. Indeed, tactile sensation plays a good part in overall bass experience.

Anyone come across that picture of the Japanese audiophile who used those 31" diameter Fostex woofers in his setup. It was this huge horn thingy mounted into the wall, all in wood. It was really gorgeous. That sucker looked like it could blow out a campfire or two!

Can't seem to find it now...

JohnR · « **Reply #12 on:** 11 Dec 2003, 12:46 am »

Another advantage of larger drivers that hasn't been mentioned yet is that you can either run them sealed and still get good bass response, or if they're ported they can be tuned lower so that the group delay is less objectionable.

WerTicus · « **Reply #13 on:** 11 Dec 2003, 06:54 am »

i was going for sealed so the bigger drivers a good idea... also there is not going to be a passive crossover as it will be all active...

i think a 3.5way system is the way to go realllllly... which brings me right back to here...

http://home.hetnet.nl/~geenius/Diary.html

JohnR · « **Reply #14 on:** 11 Dec 2003, 09:52 am »

That's quite an expensive set of drivers there...

WerTicus · « **Reply #15 on:** 11 Dec 2003, 11:51 am »

yes but its only money
what else are you going to do with it? horde it? roll around in it???

JohnR · « **Reply #16 on:** 11 Dec 2003, 12:10 pm »

OK, whatever. Good luck.

Marbles · « **Reply #17 on:** 11 Dec 2003, 12:11 pm »

Quote from: WerTicus

yes but its only money
what else are you going to do with it? horde it? roll around in it???

Well I spend mine gambling, whoring and drinking....course I just waste the rest