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Discussion Starter · #1 ·
I noticed a few tower and bookshelf speakers have 8" woofers, whereas most have 6.5" or less. I have read that larger woofers can 'muddy' up the upper bass region. If so, why would anyone ever manufacture such a speaker? Are there work-arounds or ways to compensate for that? I would think that an 8" woofer would be more efficient, so if that shortcoming can be overcome, why wouldn't more speaker makers use 8" woofers?


Also, wouldn't the best solution be to have several different size woofers in a speaker and only send them the frequencies they handle well? Like a speaker with a tweeter, a 4", a 6.5", and a 8"? Why isn't that done more?
 

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Quote:
Originally Posted by shadyJ /forum/post/17007587


I noticed a few tower and bookshelf speakers have 8" woofers, whereas most have 6.5" or less. I have read that larger woofers can 'muddy' up the upper bass region. If so, why would anyone ever manufacture such a speaker? Are there work-arounds or ways to compensate for that? I would think that an 8" woofer would be more efficient, so if that shortcoming can be overcome, why wouldn't more speaker makers use 8" woofers?


Also, wouldn't the best solution be to have several different size woofers in a speaker and only send them the frequencies they handle well? Like a speaker with a tweeter, a 4", a 6.5", and a 8"? Why isn't that done more?

It's called a balance of trade offs. The 8" can potentially move more air and produce more bass. At the same time it will likely stop moving as a piston at a lower frequency making it harder to match with a tweeter. Having more drivers like a woofer, mid-range, and tweeter has a lot of advantages but also has disadvantages. It's more costly and complex to build a 3-way crossover than a two way and many argue having too much crossover is bad in itself. Some even prefer no crossover and use a single driver with a wizzer cone to help extend the high frequency and avoid the need for a tweeter. Personally I believe crossovers solve many more problems than they create but others would disagree.


So, it's a complex problem. There really isn't any rule of thumb that will tell you that one approach or another is better.


mk
 

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I can't add much to MK's excellent response. One reason you see smaller drivers in today's speakers is the move to a more slim/sleek design in speakers. With the move toward more and more speakers in a room, and comparably few having dedicated HT's, the need for slimmer more "decorator friendly" boxes became a requirement. Also with HT sound tracks, there are more dynamics involved (short, often times powerful swings in SPL levels) where quick responses from the drivers are needed. This is handled easier by a smaller driver and quite possibly where you got the larger driver being "muddy."


Larger drivers are still sometimes used in tower speakers (8", 10" even 12") but are side mounted rather in the front baffle like speakers we grew up with as kids. This works just fine since bass sound waves are much longer than higher frequencies and are much more difficult to locate. Another way designers are getting around using larger drivers is by the use of multiple smaller drivers. IOW, two 6" drivers working together can go much lower into the frequency range than can a single driver. And, by being smaller will do so much quicker/faster than one that is larger. So, you get the benifit's of being able to handle the faster transients of today's HT sound tracks AND play as deep as a larger driver.


A great example of that kind of thing in action would be a line array speaker. Depending on the size of the line array you have multiple woofers and tweeters in a vertical array. Anywhere from 10 or more 6-1/2" (or whatever size they happen to use) woofers. Now the big advantage to having all of those 6-1/2" woofers playing together is you now have the ability to extend the FR of the speaker from up high in the mid-range down into 20Hz sub bass range (or even lower) and do so with ease, speed and accuracy. With all of them working together, each individual driver is not working nearly as hard so you can cover that larger FR with ease and never taxing a single driver so you also get MUCH less distortion of any kind. The same with the tweeter array. All working together, they can cover a wider FR without ever breaking up. It makes everything so much smoooooother top to bottom. The trade off here though is the cost of line array speakers (and of course their size).


So, no matter what you do in designing a speaker, there alre always trade offs and compromises. Even using a cost no object approach for the components, doesn't guarantee good sound from the end result or finished product. It's all about integration and interaction between all of the components including the drivers, crossovers, cabinent, wiring, etc. Including probably the MOST important thing in how a speaker performs or sounds which is out of the designers control and quite often ignored.... interaction with the room the speakers are placed in. Room treatments have nearly as much to do with over all sound quality as the speakers themselves.
 

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Discussion Starter · #4 ·
Thanks for the responses guys, that definitely helps me understand better. Just to make sure I get it, you are saying the magnet in the larger cone sizes are more difficult to stop and start, due to its larger mass, so they aren't ideal for the higher frequencies below the tweeter? And this starting/stopping problem is the low-frequency oscillations that inevitably occur when as the driver has to be stopped or started, because it can not be stopped or started instantly?
 

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Another point to add is that technology has advanced within the last few years to enable some 7" and smaller drivers to produce more air movement by allowing them to move farther back and forth (called XMax, short for maximum excursion). Generally, these designs trade off efficiency for their bass capabilities, so you will need a good amplifier for this type of speaker.


Also, some audiophiles believe that smaller midwoofers produce better stereo imaging, perhaps in combination with the slimmer cabinet profile that they allow to the designer.
 

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Quote:
Originally Posted by shadyJ /forum/post/17009201


Thanks for the responses guys, that definitely helps me understand better. Just to make sure I get it, you are saying the magnet in the larger cone sizes are more difficult to stop and start, due to its larger mass, so they aren't ideal for the higher frequencies below the tweeter?

No. Anything you hear about larger drivers being harder to stop is audiophile pseudo-science probably started by a company trying to market its brand of snake oil with smaller drivers.


As confirmed by Harman Group research, people all want


1) flat on-axis amplitude response

2) off-axis amplitude response like on-axis, with a gradual increase in directivity.

3) low distortion of all sorts


Driver size makes no difference in #1. It makes a big difference in #2.


Sounds are sums of sine waves, where different sine waves at the same frequency can be added as vectors. The simplest example would be two sine waves of equal frequency and magnitude but 180 degrees phase difference cancelling.


Where frequencies increase wave lengths grow small relative to the driver diameter and there's a greater phase difference between different driver parts as you move off-axis so there's less total energy.


This is important because domestic sized rooms are small enough that your brain is adding some of the early reflections into the direct sound; and that doesn't sound natural where there are peaks and dips. 3/4-15/16 of the sound you hear can be coming from the reverberant field which came from the sound leaving the speakers at all angles.


When you cross a driver at too high a frequency, you get an increase in total power output above the cross-over point and it sounds unnatural. Wave guides and acoustic cancellation can be used to minimize this effect and reduce the lobing about the cross-over point which results from driver spacing.


Since displacement requirements quadruple for each lower octave, a lower cross-over point requires a beefier high frequency driver and/or the process to be repeated several times. You really need 3-4 ways with conventional dome and cone drivers to get good polar response with acceptable output levels where one might be a separate woofer enclosure.


There aren't any usable rules of thumb beyond nearly all conventional designs sharing flawed physics regardless of price point.
 

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Discussion Starter · #7 ·
wow, thanks for the response guys! This is all good information. By the way, I didn't hear that larger driver being harder to stop from a snake oil source, I just kind of inferred it. I don't know much about speakers, but I am learning a lot due to this place. Thanks again!~
 

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Traditionally, some of the best (and most efficient) speakers are two ways, with a horn that goes down to 500 Hz (or so) and a big 12" or 15" woofer to cover the rest.


Modern designs tend to use multiple, smaller woofers (for aesthetic reasons noted above). They usually require a separate sub-woofer to achieve a similar sound.
 

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As stated above, larger speakers aren't necessarily harder to move as quickly, it is probably more that the manufacturers can't be bothered using more metal/magnet which is probably required for better sound, just so they can make more money. Also, the cone usually requires more material to minimise distortion and allow more linear excursion.


I think I read somewhere that too much magnetic strength can also affect the sound in a bad way, but not many drivers ever get to that stage.


Finally, not many people have 8" speakers which probably require a 10" enclosure sitting next to their monitor/T.V.
 

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Discussion Starter · #10 ·
So, to sum it all up, a 8" woofer can sound just as good as a 6.5" woofer, with the exception of off-axis response. The speakers I am thinking of here are some of the Paradigm Monitors, the larger BIC Acoustechs, and some studio monitors I have seen from KRK and Behringer. I asked the initial question because I had read somewhere that larger woofers can muddy up the upper bass, but if so, why would those companies release speakers like that? It appears that the person who said that about larger woofers didn't really know what he was talking about. Again, thanks for the answers everyone.
 
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