x-max vs enclosure volume - diyAudio
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Old 22nd March 2013, 03:46 AM   #1
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Location: Ontario Canada
Default x-max vs enclosure volume

I am currently working on a custom ABC enclosure that will be designed for SQ while maximizing spl. I would like to know how I can figure out the optimal size for my enclosure in order for the woofer to reach x-max, at 1000 watts. The enclosure will be tuned to roughly 27hz. perhaps a bit lower

JL 12w7

specs as follows:

Free Air Resonance (Fs) 27.2 Hz
Electrical Q (Qes) 0.514
Mechanical Q (Qms) 7.807
Total Speaker Q (Qts) 0.482
Equivalent Compliance (Vas) 2.33 cu ft / 66.0 L
One-Way Linear Excursion (Xmax)* 1.15 in / 29 mm
Reference Efficiency (no) 0.249%
Efficiency (1 W / 1 m)** 86.2 dB SPL
Effective Piston Area (Sd) 84 sq in / 0.0542 sq m
DC Resistance (Re) 2.47 Ω
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Old 22nd March 2013, 05:58 AM   #2
OscarS is offline OscarS  United States
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I modeled it in Akabak. As I recall, I didn't like the resulting frequency response----huge dip within the passband.

EDIT: yup found it...

Click the image to open in full size.

Last edited by OscarS; 22nd March 2013 at 06:00 AM.
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Old 22nd March 2013, 09:52 PM   #3
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I'm not sure I understand the graph. I just want to design an enclosure that will maximize the Xmax of the driver. (30mm) it won't play below 25 hertz often and my amp has an lpf set at 30. 24db/octave
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Old 23rd March 2013, 06:21 PM   #4
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Don't want to sidetrack content.
Quote:
The enclosure will be tuned to roughly 27hz.
deebeez92, what (calculations/simulation) base do you have to say that. So I can follow you up...
That's presuming it's a BR, a sealed type looks also great?! A sealed 100L looks good for home environment with a Qtc = 0.65 (sealed good from 65-200L).
Note: the Sealed Enclosure Specifications is good maybe only for car with only Volume (net int.) 1.375 cu ft / 38.94 L
Following your line of though, with easy build enclosures not mentioning horns/others, I looked at a good alignment from VB = 100.0 L, FB = 22 Hz what would be good maybe in open space/freefield with very low F3~19/21Hz (in room/freefield).

Again , jlaudio shows for ported Volume (net int.) 1.75 cu ft / 49.6 L, what might work in car not home (65-150L)
You need to have in mind that this is a subwoofer and you have to much of infra sound. A smaller box VB = 80.0 L, FB = 20Hz might work. 27Hz tunning (look below) makes a bigger lob @40Hz that might compensate rolloff, I don't know, without further measuring or simulating. Maybe you are using active equalization or other means of control that I'm not used to/or don't use. Please criticize this.
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Old 23rd March 2013, 10:39 PM   #5
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Okay example. My current setup is 1.67 cu ft ported at 31 Hz. At roughly 900 watts, the woofer is no where near x max. I'm trying to design an ABC enclosure, and I just want to know how I figure out what size I need for me to optimize the drivers long throw.

I've read the ABC's have a much larger tuning shelf so i'd like to tune lower, (ex 27 Hz, maybe even lower) but then i'll begin to lose out around the upper 50's. The sub wont be playing much above 65 and won't play anything below 20 - infrasonic filter 24 db's / octave.

sealed is definitely out of the question.

note, i'm also aiming for a Qtc of 0.5 - 0.6
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Old 24th March 2013, 02:24 AM   #6
a.wayne is offline a.wayne  United States
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The QTS is too high i would not vent ...
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Old 25th March 2013, 05:07 AM   #7
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quick question regarding Xmax. in win isd does the cone excursion refer to one way come travel or two way. and should I be thinking of come excursion as both halves or simply as the one way linear motion (Xmax or rear Xmax plus front Xmax) peak to peak
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Old 25th March 2013, 06:08 AM   #8
VaNarn is offline VaNarn  Australia
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Xmax is one way travel and given a symmetrical magnetic field should be equal for the forward and the reverse movement.
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Old 25th March 2013, 07:40 AM   #9
Zero D is offline Zero D  United Kingdom
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@ deebeez92

Excursion In WinISD can show 3 methods

Choose any from the OPTIONS Tab
Attached Images
File Type: png cex.png (1.5 KB, 60 views)
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Old 25th March 2013, 01:43 PM   #10
AndrewT is offline AndrewT  Scotland
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Trial and error in WINisd pro.
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