Woofer question: One big versus several small?

[charlielaub]

So far the discussion about more smaller or fewer larger woofers has focused around total displacement, or how to arrange more smaller woofers. This is completely ignoring the fact that larger woofers are just better at producing bass. Smaller woofers that can "play low" will less efficient and they will typically (generally speaking I mean) have higher distortion for the same SPL level even when using multiples of them with the same cone area. On balance, to make that larger woofer "play nice" you will need a larger cabinet, sometimes much larger. It really depends on how low in frequency you were planning on reaching with the loudspeaker and at what SPL. Low and loud more or less requires large drivers. If you are targeting a more "monitor" like F10 of 60Hz, then a single 6.5" will probably do just fine. OTOH, 30Hz and below at room filling levels is another matter.

I am a bit saddened by what seems to be the latest trend in consumer loudspeaker form factor: a tower loudspeaker using multiple 6.5" class woofers. Compare a current example of this (how about the B&W 804 D3) to the good old days of a 3-way monkey coffin or a speaker like the B&W 801, which used one larger (12" ?) woofer in a big cube below the mid and tweeter, which were in separate enclosures. This is just not a great approach, and I think it's more a matter of market forces (e.g. shipping costs) that are driving the multiple-small-woofer-tower trend since they can be slimmer and lighter and each package will fit under the UPS/FedEx weight limit of 70 lbs and can be placed unobtrusively on either side of a large screen TV. Gotta have a market and an affordable price point to be successful in business.

If you do a Google search about this topic (I just did) you will find a thread in this forum from 2011 with lots of different opinions. I assume the same will hold in 2019.

[billfitzmaurice]

I'm (semi) working on a design that uses (8) 4" drivers with approx. the same cone area as a 10-12" woofer and although it does dig low, a nice 10 or 12" woofer would undoubtedly have more powerful 30-45 Hz output.

I should have mentioned before that using a lot of smaller drivers rather than one larger one also gives one the ability to run the drivers to a much higher crossover. My HT LR mains use eight four inch midbasses, crossed over to twelve tweeters at 4kHz, which wouldn't work well with even 8 inch woofers. The advantage to crossing that high is being able to use 1/2 inch domes, which have twice the dispersion angle up high of one inch domes. The mains only go to 80Hz, but below that is what subs are for.

Do you really want to wire up 9 drivers?

Nine drivers wired as three driver sets in series, the three sets parallel, gives the same impedance as one. It's the preferred arrangement if you need to keep the load impedance the same as one driver, as eight drivers wired series/parallel with give a load half that of one driver.

[devnull]

That's what Bose did with the 901s, 10 or 12 small drivers They had to EQ them to get the response at the top and bottom. One thing to keep in mind is a good 4" driver might have an Fs of 75-80 whereas even an inexpensive 12" driver will have an Fs in the 30s. I think where multiple drivers really start to come into play is when you're comparing multiple 12s or 15s vs single 18s or 21s. I've actually been pondering a coffee table size subwoofer using 4 of the HSU buyout 12" subwoofers. That's a lot of Sd for 250 bucks

A question: Do you really want to wire up 9 drivers? That's a bunch of connections and polarity problems waiting to happen....

[tomzarbo]

With several smaller woofers, you end up usually spending more on crossover parts as you have to cross the drivers farther from the tweeter at lower and lower frequencies as you move farther away from the tweeter.

I'm (semi) working on a design that uses (8) 4" drivers with approx. the same cone area as a 10-12" woofer and although it does dig low, a nice 10 or 12" woofer would undoubtedly have more powerful 30-45 Hz output.

On Kevin's point above... I have a set of Polk RTi's that have an MTM section on top, and three 7" woofers on the bottom. They can play ear-bleedingly loud, but the lowest octave is still missing in my opinion.

TomZ

[Unbiasedsound]

IMO a bigger woofer sounds fuller and usually goes lower.....Other then that I agree with that is mostly about aesthetics and WAF...Space wise most do not have it and big speakers in a small space seems to only add to the clutter.….The Japanese are use to the clutter and seem to like the huge old school JBL speakers in there tiny apartment sized houses because they are still traditional in where the women do not get there way like they do in the USA.

[a4eaudio]

I know there are some threads out there where people like one vs the other, but I think the primary driver for the trend in narrower speakers is aesthetics. We can claim it is WAF (wife acceptance factor) but it is more convenient to place a narrower speaker in most rooms, wife acceptance or not.

[mikec]

And this is how you learn ;) Thanks for the replies!

.
One bigger driver with a decent xmax seems more cost effective than several smaller woofers.

Makes sense -- I was just looking at cone area, not displacement.

[kevintomb]

Polk Audio in the 80s mostly, sold several" speakers that used multiples of their 6.5" mid woofers.
I liked the sound back in the day, but honestly not sure several smaller woofers had anything to do with the sound tonality and balance.

Now looking back it seems okay to use a few smaller woofers, but not cost effective to use more than maybe a few.
One bigger driver with a decent xmax seems more cost effective than several smaller woofers.

[billfitzmaurice]

For example, nine 4" drivers or four 6" drivers would have same area as one 12". If all the drivers had similar properties would there be a difference?

Yes, if they're vertically arrayed. Dispersion at the upper end of their range would be wider in the horizontal plane, narrower in the vertical plane.

Would multiple smaller similar drivers have a higher total cost?

Usually, which is the main reason for using the larger driver.

Would the narrower baffle have an advantage?

Only if for some reason you want the baffle step to be at a higher frequency.

[mikec]

too much time to think---

Has anyone listened to similar enough designs to decide if there's a noticeable difference?

For example, nine 4" drivers or four 6" drivers would have same area as one 12". If all the drivers had similar properties would there be a difference?

Would multiple smaller similar drivers have a higher total cost?

Would the narrower baffle have an advantage?