Is this a good or bad idea (too small enclosure for a woofer)

[critofur]

Let's say we're making a 3 way speaker and the woofer is less sensitive than the mid.

If we put the woofer in a too small enclosure the bass doesn't extend as low, but, we do get an bump in the level.

Other than not being able to go as low, is there any drawback to doing a design this way?

In the picture: green is a Tang Band W5-704 and blue is the Parts Express Buyout Alesis 6.5" Carbon Fiber woofer

 

[Conrad Hoffman]

I use an active crossover, so levels are of no concern. IMO, a 3-way is tough enough to do well, and adding passive crossovers to the mix just makes it harder. I actually prefer a *small* bump in the response, and think a system Q of .707 is too low. I go for .9-1, which sets the box size a bit smaller. Everybody's tastes vary.

 

[omni]

You may end up with a bass response that sounds boomy if the enclosure is too small......You probably will not have a very musically sounding lower end, again, if the enclosure is too small.......For example: the kick drum could possibly sound muddy...........Conrad Hoffman is describing a .707 Q, which is considered a flat response for a woofer, which, in many circles, is a preferred Q response to achieve........By taking it up to .9 to 1, he is extending his upper bass sound levels by decreasing his box size, and .9 to 1 is still a Q factor which has a fair degree of damping, so he is not losing control of his woofer response, while he is extending and gaining a bit more SPL for his given woofer.........My guess is that he has an understanding of his woofers parameters, and can design his box accordingly. If you are doing a 3 way design, you may want to gain an understansing of how box size affects woofer performance......Extending your upper bass with too small of an enclosure for a particular woofer could have a negative effect on the midrange, in addition to the fact that we are not sure if you are using a sealed enclosure or vented......If you have ever heard a car drive by that is sporting a loud subwoofer, you may be able to relate to what I am describing here, and alot of car subwoofers are notorious for being mounted in enclosures that are way too small for good, musically sounding performance........Continue to do some research..........Vance Dickasons' Loudspeaker Design Cookbooks does a very nice job of discussing your topic..........I might recommend you start there...........Respectfully........Omni

 

[critofur]

So - the sound could be negatively impacted even though the overall combined (woofer + mid) freq. responce is flat?

The woofer would be vented and the mid sealed.

I have Vance's book, I read most, I'll look again to see what he says about this particular topic...

In "those cars" with the booming bass, the overall freq. response is definately most often not flat.

 

[omni]

That may depend on what your crossover frequency is between the woofer and mid.......And how much overlap in response you might get at crossover from having the woofer response extended and how much it extends into the midrange region...........It has been my experience with a woofer which is in too small of an enclosure, that the midrange becomes a bit overwhelmed and somewhat drowned out by the extended response of the woofer in the upper end of the bass........Clarity is lost, however, as Conrad Hoffman pointed out, everybody's tastes vary........I personally prefer the woofer to handle the low end, while the midrange handles the middle frequencies, and of course, the tweet handles the upper end........You mentioned that your enclosure was going to be vented, which changes the whole scenario..........WinISD Pro may be another good resource for you....It is a neat little program you can download on the net, which will help you model yoiur enclosure for your particular situation..........Regards........Omni

 

[marchel]

If putting a woofer in a relatively small sealed box is bad, Then putting it in a relatively small vented box is really bad.

I suggest you dont do it, Unless the small box is calculated to be compatible with your woofer.

 

[Hezz]

I would be willing to bet that many commercial speakers are designed this way when using low quality components and to get a small cabinet. However, you will notice that with most higher quality drivers the bass speakers are usually more efficient than the mid/bass variants. Except for subwoofers which have a tendency to be lower efficiency.

The sound quality will suffer if this approach is taken but it can be used to make a high Q system sound somewhat better. But to do it right you need to set the midrange/woofer crossover frequency low enough. If you have a good quality mid/bass this might work OK since it will be shouldering some of the load in the upper bass region.

 

[LineArray]

Hi Critofur,

as the former posting said, compromising the
bass enclosure this way is not a good idea.

Ho much is the difference in SPL between Woofer
and Midrange (dB) ?

If the Midrange is made of untreated paper (don't know your
driver) you could apply a damping coating to the cone,
thereby reducing cone resonances.
The increase of mass will drag the efficiency down,
and increase the Qt of your midrange.

Could be a solution to make the best of it.

 

[sreten]

Let's say we're making a 3 way speaker and the woofer is less sensitive than the mid.

If we put the woofer in a too small enclosure the bass doesn't extend as low, but, we do get an bump in the level.

Other than not being able to go as low, is there any drawback to doing a design this way?

In the picture: green is a Tang Band W5-704 and blue is the Parts Express Buyout Alesis 6.5" Carbon Fiber woofer

Hi,

If the woofer is less sensitive than the mid you knock the mid back.
a 1dB bass bump will not make much difference and is pointless,
compared to a more extended flatter alignment.

/sreten.

 

[omni]

Hezz, your point about the bass speakers being more efficient than the mid/bass variants is a good one......This too can be resolved fairly easy by rolling the woofer off quickly or, as you pointed out, having a low enough crossover frequency........In Critofurs' case, he reports that his woofer is less sensitive than the mid........In my humble opinion, this is a good situation, because it seems to me that during the design phase in his crossover, he can certainly make adjustments for differences in efficiencies between the two drivers......I would rather bring the SPL of the midrange down, than to attempt to bring the SPL of the woofer up..........Omni