JBL: CONVERSION CONSTANTS and USEFUL DATA (WITH SOME IMPROVEMENTS )

[RMC]

As I get older I keep forgetting my math formulas and data required to feed my speaker building addiction. So I made myself a one-page sheet derived from a JBL document of some of the important stuff I should remember... Which I think should also be useful for many other members here. Someone may like to make a "sticky" out of that. Be my guest and do it for the benefit of all. Richard

LITERS FEET^3 INCHES^3 METERS^3 MILLIMETERS INCHES METERS
___________________________________ _____________________________
1.00 = .035315 = 61.02 = .001 1.00 = .039 = .001 Liters = Cu. Ft. x 28.32
28.32 = 1.00 = 1,728 = .02832 25.40 = 1.000 = .0254 Cu. Ft. = Liters / 28.32
1000.00 = 35.315 = 61,024 = 1.00 1000.00 = 39.370 = 1.000

TO FIND SOUND WAVE LENGTH: divide velocity of sound by frequency (Hz)
SOUND VELOCITY = 344 m/s, 1130 ft/s or 13,560 in/s

AREA OF CIRCLE = Pi 3.1416 x (radius squared) Note: radius = 1/2 diameter; OR .25 x Pi 3.1416 x Dia. squared

TO FIND THE DIAMETER OF A CIRCLE WITH EQUIVALENT AREA:
2 x square-root of (area divided by 3.1416)
example: area of 9" (23 cm) tube = area of 8" (20 cm) square duct calculated:
(US Units) (area) 64/3.1416 = 20.372, square root = 4.5135 x 2 = 9.03" (diameter)
(Metric Units) (area) 400/3.1416 = 127.324, square root = 11.284 x 2 = 22.568 cm (diameter)

VOLUME OF CYLINDRICAL DUCT = circular area x length; logically it should be outside circular area ?

VOLUME DISPLACED BY JBL LOUDSPEAKERS: 8" (20 cm) = .05 cu ft (1.4 L.), 10" (25 cm) = .1 cu ft (2.8 L.),
12" (30 cm) = .15 cu ft (4 L.), 15" (38 cm) = .2 cu ft (6 L.), 18" (46 cm) = .3 cu ft. (8.5 L.).

JBL LOUDSPEAKER MOUNTING HOLE AND BOLT CIRCLE DIMENSIONS:

mounting holes: (Always double-check with specific driver data sheet)
8" = 7-1/16" (18 cm), 10" = 9" (23 cm), 12" = 11-1/16" (28 cm), 15" = 13-31/32" (35.5 cm),
18" = 16-13/16" (42.7 cm).

bolt circles: (Always double-check with specific driver data sheet)
8" = 7-5/8" (19.4 cm), 10" = 9-3/4" (24.8 cm), 12" = 11-9/16" (29.4 cm), 15" = 14-9/16" (37 cm),
18" = 17-3/8" (44 cm).

* Document taken from JBL FAQ Speaker Building Q & A, with some additions such as Metric conversions.

Richard

EDIT: Sorry but I just can't get the three data columns at the top to be separated so they would look more appropriate. Tried but need help on that.

[emilime75]

Maybe just format it differently?

1l = .35315^ft = 61.02^in = .001^m

...and so forth.

[RMC]

Hi Emilime,

Thanks for the suggestion and patience.
I tried about five different ways here to make the damn thing look good (data at the top) but it just won't work... Everything just gets packed together. My original was written in Wordpad (Win 7 Pro) and transfered here (copy and paste). In the "preview post" and in the "Edit" modes it DOES look good, however the moment I click "Submit post" the shi.. hits the fan... My one-page printed copy to go in my Speaker Building binder is A-1. Wish I could do that here. I'll try something different tomorrow and try re-issue the document... If you need a good copy in the meantime see my profile, e-mail me, I'll send a really nice one from Wordpad.

Richard

[dn92]

This thread is a very good idea, especially for us, that are using only international normalised scientific units and not units heritated from the Middle Age :D

This is not a criticism but the information might be more useful if formulas could be in a graphic form and inserted as images.

[RMC]

Hi dn92,

Thanks for your comments. Formulas in graphic form ??? Give me a break, I have enough trouble to get the small table at the top of my post #1 just to show correctly... I'll be trying a TEST post once again in a few minutes to see if it will show correctly...

Canada switched to Metric in 1983 if I'm right, but I was raised for about half of my life with the British Imperial system of measurements (that's why I'm not lost in the US units) and had to learn the Metric system in the other half... Knowing both systems, I still work with both and switch between the two regularly, but sometimes get mixed-up or can't remember a precise formula or number in one of the two, so this is the reason for this reminder document, moreover I also had usefulness for my European friends in mind...

Richard

[RMC]

This is only a TEST to see if data at the top of my post #1 will finally show correctly. If OK I'll re-issue document.

LITERS FEET^3 INCHES^3 METERS^3 MILLIMETERS INCHES METERS
1.00 = .035315 = 61.02 = .001 1.00 = .039 = .001 Liters = Cu. Ft. x 28.32 OR
28.32 = 1.00 = 1,728 = .02832 25.40 = 1.00 = .0254 Liters = Cu. Ft. /.035315
1000.0 = 35.315 = 61,024 = 1.00 1000.0 = 39.370 = 1.00 Cu. Ft. = Liters / 28.32

Richard

EDIT: QUITE EVIDENTLY IT STILL DOES NOT WANT TO POST CORRECTLY... EVEN THOUGH IT LOOKS PERFECT IN PREVIEW AND EDIT MODES !
IF YOU WANT A NICE LOOKING ONE-PAGE COPY, E-MAIL ME, I'LL SEND YOU ONE FROM MY WORDPAD ORIGINAL...

[cooky1257]

http://www.metric-conversions.org/measurement-conversions.htm
For bolt circle ALWAYS check the drive unit spec and measure the actual driver twice just to be sure.
If you need the formula for the volume of a cylinder perhaps you shouldn't be using power tools-or anything sharp.
Oh and stop using CAPS.:o:

[JeffW]

You might be able to alter your settings for the site and make it work.

To the right of "Welcome" next to your user name, click Settings.

Under the section My Settings in the panels on the left of the page, click General Settings.

At the very bottom of that page, under Miscellaneous Options, there are three different editor options. Pick a different one that what you are currently using and see if that allows you to format your post as you had intended.

[emilime75]

Maybe do it in Excell? You can take a screen shot of it and post it as a jpeg, and/or upload the file for people to download, maybe.

[RMC]

Hi Jeff and emilime,

Thanks for being helpful with the Forum software... I did change my settings as suggested by Jeff. Plus will try to upload text as emilime indicated. Hopefully, the damn thing will fly one day...

Previous text version: Wordpad with .rtf extension (the default setting) which the software here doesn't accept, based on the list of acceptable file extensions. So I changed the document format to Notepad with a .txt extension which the Forum Editor is supposed to accept.

At the "preview post" stage its even worst than before ! So I cancelled going further. Uploading doesn't want to work also... Looks like a lost cause. Just write me if you want a copy by e-mail. Maybe post it for me or make a "sticky" of it from my original by e-mail ? Thanks.

Richard

[JeffW]

You might try zipping the spreadsheet into a .zip and attaching that to a post. It'd be a shame to not see it displayed, but it would be accessible without resorting to emails.

[RMC]

Hi Jeff,

Thanks again for your help and patience. You're right it would be a shame after all this work done...

This is my uploaded text with .txt extension from Windows Notepad. Finally, open the Champagne bottle guys and have a cigar...
I tested it and it works OK. I read somewhere that pop-up blocker in Internet explorer had to be de-activated for the upload to work !
Can someone make a "sticky" out of it for everybody's benefit ? It still looks much better with .rtf extension in Worpad. Best regards,

Richard

[JeffW]

It looks great in wordpad with word wrap turned off (no wrap).

Here it is as a .pdf for those who might prefer that format.

[RMC]

Hi Jeff,

Thanks for the contribution in making it as a .pdf version. Text is much more clear. The only drawback in that .pdf format is that the data table at the top is not properly aligned with the title of each column, compared to the .txt Notepad version. Thanks again for your help. Best regards,

Richard