From ???@0x00001225 Mon Dec 11 13:17:09 2000 Path: pitt.edu!newsflash.concordia.ca!sunqbc.risq.qc.ca!news.maxwell.syr.edu!transit.news.xs4all.nl!not-for-mail From: "Dré" Newsgroups: rec.audio.tech Subject: Re: Bose speaker question Date: Mon, 11 Dec 2000 15:06:05 +0100 Organization: New Line licht en geluid Lines: 84 Message-ID: <912n4m$1t2$1@news1.xs4all.nl> References: <20001205202820.02711.00002567@ng-cq1.aol.com> <20001206012634.02941.00006481@ng-fi1.aol.com> <3a2e0177$0$20857$272ea4a1@news.execpc.com> <3a31ee1e$0$20870$272ea4a1@news.execpc.com> <3a349f43$0$90272$272ea4a1@news.execpc.com> NNTP-Posting-Host: s340-modem3463.dial.xs4all.nl X-Trace: news1.xs4all.nl 976543702 1954 194.109.173.135 (11 Dec 2000 14:08:22 GMT) X-Complaints-To: abuse@xs4all.nl NNTP-Posting-Date: 11 Dec 2000 14:08:22 GMT X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 5.00.3018.1300 X-MimeOLE: Produced By Microsoft MimeOLE V5.00.3018.1300 Xref: pitt.edu rec.audio.tech:136678 Status: N "Mike Suhm" wrote: > Using a 200 w/ch receiver as an example, even if the music is played loud > enough to the point of clipping the amplifier, each individual driver is > getting a little over 22 watts. Hardly enough power to cause overexcursion > of these drivers. As is mentioned earlier, excursion follows second power reciprocal of frequency. Add to that the fact that it's (according to your statement) a BASS REFLEX cabinet (meaning it will NOT drop off second order but 3-4th order instead) and you can see that these speakers will have a very bad time providing anything substantial below 50Hz. It's NOT the world according to Bose, it's the world according to Physics. Unless either you or Bose have found a way to avoid these physical rules, you're quite stuck with providing a very VERY good subsonic below ooh aah 45Hz (or maybe even higher). But let's look at the physics for a while. Let's simulate an average 5" driver (even BIGGER than the ones used in the Bose speakers BUT the smallest I had info on) in an average BR cabinet and let's plot maximum power vs. frequency for ONE speaker. Let's take a Vifa WP-130 (a speaker that will quite probably outperform the Bose speaker with it's 4.65mm maximum lineair excursion and 80W power rating). This speaker does well in a 4.1 liter Bass Reflex cabinet (so 9 of them should fit in a 36 liter cabinet, probably quite close to the 901). Freq. vs. Maximum power: 100Hz 80W 90Hz 80W 80Hz 80W 70Hz 80W 60Hz 80W 50Hz 45W 40Hz 10W (goes FAST doesn't it?) 30Hz 8W 20Hz 5W DC 3W From the above it is quite visible that if you feed it with a 22W signal at 40Hz, the unit may FAIL!!! Let's look at the maximum acoustic power (restricted by either power rating (higher freq.) or excursion limits (lower freq.) vs. frequency (a thing that says a bit more IMO) per speaker: Freq Acoustic output: 200Hz 0.5W 100Hz 0.3W 80Hz 0.1W 60Hz 0.05W 40Hz 0.0005W So, even if you combine 9 of these drivers, their MAXIMUM output at 40Hz will only be 0.0045W. That's 88.5dB (or probably less depending on placement (since this number assumes half sphere loading))!!! That's quite a bit lower than the 118dB these speakers can produce at 200Hz! And all this is done using a 5" driver model instead of a 4" driver model (could be compensated for IF it should be that the 4" Bose speakers have a bigger X_max than the 4.65mm of the Vifa speaker (which I doubt BTW)). > And because of the small driver size, thus the smaller > voice coils and magnet structures, the drivers don't have the capability to > reproduce very low bass signals in any case. I know, this is where the Bose > EQ with the infrasonic roll-off comes into play, but the system will always > be subject to the mechanical limitations of the drivers. Which will be met below 40Hz regardless of what brand is on the box. It's nice when you stick numbers to things such as these. Numbers don't care about brands and provide a lot more info than mere speculations and opinions! Short: You'd better make sure there is a good subsonic to protect the speakers or you'll be spending huge amounts of time reconing the things (if that's even possible with speakers such as this). -- André Huisman New Line licht & geluid huisman@new-line.nl http://www.new-line.nl --- pardon my French, I'm Dutch ---