In Reply to: Hi, Rip! Sleep well? posted by John Marks on December 22, 2009 at 19:54:52:
Pardon me while I put on my "manufacturer" hat. Here are three arguments in favor of a vented box:
First, in a two-way design, the woofer's performance in the region of the crossover frequency is of paramount importance. If we're going to ask a cone woofer to go up fairly high (I take 12" woofers up to 1.5 kHz ballpark), the cone better be light and the motor strong. Now it just so happens that woofers with light cones and strong motors generally do not give adequate bass extension in a sealed box (not even my 12's). So if we don't want to add subs, a vented box is called for.
Second, for years I assumed that a sealed box had better midrange than a vented box, but a couple of years ago decided to find out for sure. I build two test speakers, one ported and one sealed, but otherwise identical. I then conducted a blind listening test, instructing the listener to focus only on the vocals. In every trial the listener preferred the vented box. I have since learned how to make a sealed box that is comparable to a good vented box in midrange clarity, but it's more expensive to do than a plain old vented box.
Third, seldom is the acoustic environment in a room exactly right for a given speaker in the bass region. With a vented box and a bit of ingenuity and/or courage, it is possible for the end user to change the shape of the speaker's bass response curve and improve the in-room response.
Just for the record, it's been years since I read John Dunlavy's critique of vented boxes but my recollection is that he chose a rather boomy vented box alignment to compare with, and unfairly characterized all vented boxes based on this example. Likewise, I could chose a Qtc = 2.0 sealed box and thus make sealed boxes look bad.
All that being said, I use both sealed and vented enclosures in my own designs. Depends on the specific application.
Duke
Me being a dealer makes you leery?? It gets worse... I'm a manufacturer too.
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Follow Ups
- Some sealed vs vented ramblings - Duke 20:24:54 12/22/09 (10)
- RE: Some sealed vs vented ramblings - hahax@verizon.net 21:12:18 12/22/09 (9)
- RE: Some sealed vs vented ramblings - Duke 21:51:29 12/22/09 (8)
- RE: Some sealed vs vented ramblings - morricab 04:23:24 01/05/10 (0)
- RE: Some sealed vs vented ramblings - hahax@verizon.net 10:55:00 12/23/09 (0)
- RE: Some sealed vs vented ramblings - 3db 04:32:10 12/23/09 (1)
- Obviously I should have been more specific - Duke 08:47:41 12/23/09 (0)
- well told - Ole Lund Christensen 03:37:04 12/23/09 (3)
- RE: well told - hahax@verizon.net 11:00:06 12/23/09 (0)
- RE: well told - Duke 08:50:59 12/23/09 (1)
- RE: well told - loudspeakerguy 11:00:36 01/05/10 (0)
- RE: well told - Jack D II 13:06:35 01/16/10 (0)