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 15th June 2012, 10:24 PM #1 diyAudio Member   Join Date: May 2012 Help interpreting speaker data I'm thinking of building some cheap bookshelf-style speakers for above the test bench and was attracted to some low-price (\$30) 5" woofer/midrange devices. But, as a newbie to enclosure design, I'm having difficulty interpreting the data provided on-line. Most of the parameters are clearly stated: Specifications  Nominal impedance: 8 ohms  Power nominal: 50WRMS  Frequency response: 70Hz - 7kHz  Sensitivity: 88dB (1W@1m)  Qms: 1.404  Qes:0.717  Qts: 0.474  Fs: 67.63Hz The missing ingredient, Vas, is given at the bottom of the Impedance vs Freq graph as "Vas=7.266m M". See: http://www.jaycar.com.au/products_up...0parameter.pdf Can someone familiar with similarly-sized drivers suggest what unit of measurement must be intended here? Being a Volume, I'd be expecting Litres, Cubic Metres or something similar. But what's an "m M"? They also give the dimensions according to some convention I'm not familiar with: Dimensions:  A= 145  B= 136  C= 120  D= 56 Would I be right in assuming that:  A= 145 is outside diameter of basket  B= 136 is diameter of the circle of mounting holes  C= 120 is diameter of cone (5" = ~125mm)  D= 56 is front-to-back (ie depth)? Terry
 16th June 2012, 02:19 AM #2 frugal-phile(tm) diyAudio Moderator     Join Date: Oct 2001 Location: Victoria, BC, NA, Sol III Blog Entries: 5 Some of the units are strange on the graph. For that size driver Vas is likely 7-some litre. SOmewhere they will have a key to ABCD, your interpretation is likely correct except that C is likely the cut-piy diameter. dave __________________ community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi p10-hifi forum here at diyA
 16th June 2012, 05:54 AM #3 diyAudio Member   Join Date: May 2012 Great, thanks Dave. I'll plug that in and see if it makes sense. You had me puzzled with "the cut-piy diameter". Oooh, I thought, another loudspeaker technical expression I'm unfamiliar with. But, checking the keyboard, I note that the letters "o.u.t." are all one to the left of the letters "p.i.y.". (Pesky, finding those dashes, isn't it!) So, I'm going to proceed on the basis that 120mm is the cut-out diameter. It certainly makes more sense than my guess! Terry
frugal-phile(tm)
diyAudio Moderator

Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
 Originally Posted by Terry McGee You had me puzzled with "the cut-piy diameter". Oooh, I thought, another loudspeaker technical expression I'm unfamiliar with. But, checking the keyboard, I note that the letters "o.u.t." are all one to the left of the letters "p.i.y.". (Pesky, finding those dashes, isn't it!)

Very perceptive of you, and exactly what happened... i took grade 11 math insteadof grade 10 typing, and when on the laptop in low light my already poor typing becomes worse.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA

 17th June 2012, 06:13 AM #5 diyAudio Member     Join Date: Feb 2005 I never would have figured that out. I'd be torturing my poor already-abused brain on p.i.y. acronyms for the next month. ..Todd
 17th June 2012, 06:20 AM #6 diyAudio Member   Join Date: May 2012 Heh heh. The only good thing about getting old is you get very, very sneaky.... Terry
 17th June 2012, 06:28 AM #7 diyAudio Member   Join Date: May 2012 Hmmm. Proceeding on the basis of the dimensions given, I get a 12.37 litre box, a port diameter of 25mm (1") and a port length of 1.61cm, suspiciously close to the thickness of the wood I specified, 16mm (5/8"). I guess that's just telling me to drill a 25mm (1") hole in the box? Or should I get suspicious? Terry
frugal-phile(tm)
diyAudio Moderator

Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Blog Entries: 5
Quote:
 Originally Posted by Terry McGee Hmmm. Proceeding on the basis of the dimensions given, I get a 12.37 litre box, a port diameter of 25mm (1") and a port length of 1.61cm, suspiciously close to the thickness of the wood I specified, 16mm (5/8"). I guess that's just telling me to drill a 25mm (1") hole in the box? Or should I get suspicious?
Terry,

That is an OK looking sim.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA

 17th June 2012, 07:53 AM #9 diyAudio Member   Join Date: May 2012 Thanks Dave I'll go chop down a tree in anticipation... Terry

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