From David.S.Baker@tek.com Wed Apr 8 21:22 PDT 1998 Received: from fw1.tek.com (fw1.tek.com [192.65.17.16]) by mickey.ee.pdx.edu (8.8.6/8.8.6) with ESMTP id VAA10465 for ; Wed, 8 Apr 1998 21:22:08 -0700 (PDT) Received: from fw1.tek.com (root@localhost) by fw1.tek.com with ESMTP id VAA15294 for ; Wed, 8 Apr 1998 21:22:06 -0700 (PDT) Received: from auspex.vnd.tek.com (auspex.vnd.tek.com [128.181.189.30]) by fw1.tek.com with ESMTP id VAA15290 for ; Wed, 8 Apr 1998 21:22:05 -0700 (PDT) Received: from modtestpc3 (modTestPC3.vnd.tek.com [128.181.190.48]) by auspex.vnd.tek.com (8.8.5/8.8.5) with SMTP id VAA08814 for ; Wed, 8 Apr 1998 21:22:04 -0700 (PDT) Message-ID: <352C4C6E.30A7@tek.com> Date: Wed, 08 Apr 1998 21:19:58 -0700 From: David Baker Reply-To: David.S.Baker@tek.com Organization: Tektronix X-Mailer: Mozilla 3.0 (WinNT; I) MIME-Version: 1.0 To: thunder5@ee.pdx.edu Subject: [Fwd: Re: Banpass or Sealed?] Content-Transfer-Encoding: 7bit Content-Disposition: inline Content-Type: message/news Content-Length: 3079 Status: O X-Status: Path: news.tek.com!uunet!in4.uu.net!newsfeed.internetmci.com!134.222.90.2!EU.net!news0.Belgium.EU.net!newsr.Belgium.EU.net!not-for-mail From: "Steven Tolleneer" Newsgroups: rec.audio.car Subject: Re: Banpass or Sealed? Date: 7 Apr 1998 11:34:35 GMT Organization: EUnet Belgium, Leuven, Belgium Message-ID: <01bd6166$d20763a0$LocalHost@telbakske> References: <3526FE7B.FC2ED58@monadnock.keene.edu> <1998040503590300.WAA14578@ladder01.news.aol.com> NNTP-Posting-Host: idialup135.antwerp.eunet.be X-Newsreader: Microsoft Internet News 4.70.1157 Xref: news.tek.com rec.audio.car:173972 JKinnj2 wrote in article <1998040503590300.WAA14578@ladder01.news.aol.com>... > bakwards? hmmm so you saying that even if im wrong, that a small sealed box > is indeed "boomy" ... then my friend you are the one who is misinformed! > sealed boxes are tight and accurate, not boomy. im not saying i know > everything, but i do have some experience that a small sealed box will be > tighter than one with a larger internal air space. think about it... why does > a ported box usually play 3+ db louder than sealed... > 1) its ported > 2)no air spring (resistance) > think that one over bud! The *extra* 3dB that you get, is traded in for a steeper roll-of below the resonant frequency of the speaker and a larger enclosure. It is correct to say that for an identical -3dB point, a vented design will have a 3 dB higher efficiency over a closed system, but that is just because a speaker intended for vented designs can use a lighter cone. In fact, your claim that a vented designs has no air spring is misleading. The radiation impedance is very high around resonance... the driver will have almost no cone movement, as at that frequency, the tuned enclosure (forming a Helmholtz resonator) is responsible for the output. Once again: - a large sealed enclosure has low Q behavior around resonance - a small sealed enclosure has high Q behavior around resonance The Q expresses damping. Low Q, good damping; high Q, bad damping. The damping expresses how fast the cone stops moving after a pulse. A severely underdamped enclosure will exhibit overshoot and ringing. Graphically.... Applied signal * * * * * *-------*-------*-------------- * * * * * Low Q enclosure * * * * * * *-------*-------*-****--------- * * * * * High Q enclosure * * * * | * * * * * | OVERSHOOT *-------*-------*---*-*-*-****** * * * * * * ---RINGING--- * Some people think that a smaller box is less efficient than a bigger box. This is true, but has nothing to do with the air space, but with the parameters of the driver. If two identical drivers are installed in a large and a small enclosure, the smaller enclosure will have a better efficiency (and a better displacement limited powerhandling), because of the peak around resonance. Steven Tolleneer