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Max wattage DIY sub takes to reach Xmax

3K views 11 replies 3 participants last post by  sicride 
#1 ·
I am building my first sealed box 2cu.ft for a tidal audio 12" sub. I am trying to find out how much power it will be able to take before reaching Xmax at low frequencies, ie. 18hz. This will help me figure out my max output for flat response after equalization. Can anyone help me with how I can model this properly?
 
#2 ·
DO you have the T/S parameters for this driver?

These will be needed to determine what wattage is needed to hit Xmax. Why are you wanting your sub to hit Xmax at 18hz?
 
#3 ·
Nominal Impedance (IMP) 2/8 ohms
DC Resistance (Re) 1.8/7.2 ohm
Resonant Frequency (Fs) 20.9Hz
Electrical "Q" (Qes) .397
Mechanical "Q" (Qms) 4.172
Total "Q" (Qts) .363
Equivalent Volume (Vas) 5.92 ft3
One Way Linear (Xmax) 17.0 mm
Cone Area (Sd) 545 cm2
Sensitivity (Spl) 88.6db
RMS Power Handling (Pwr) 50 to 400


I am not trying to reach Xmax as much as I am trying to figure out how to protect my driver while knowing and achieving the best frequency extension with equalization.
 
#4 · (Edited)
I've just plotted some graphs in WinIsd pro. A bit of mucking around to post them so I'll just write what I've found.

2 cu ft sealed box with 350W of power will take the sub to Xmax at 18Hz with no EQ. Approx 99dB SPL at 18Hz and 113 dB SPL at 80Hz.
4 cu ft ported box tuned to 20Hz with 350W of power will take the sub to Xmax at 16.5Hz. Approx 107 dB SPL at 18Hz and 113dB SPL at 65Hz. This box will handle 400W.

With EQ (linkwitz transform) the maximum power the sub can take is only 30W. Approx 99dB SPL at 18Hz and tapering off to just over 102dB at 50Hz.
There is no real gain in output at the low end due to the limits of the sub.

Ported box wins hands down.
 

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#5 ·
Ported does look like a winner but is also more space than I can handle. I am limited to 15.5" deep x 18 wide x 26" tall external dimensions. I also would be building this as a first box and would be making it front slot ported. I do not know enough to time it properly for port velocity etc.
 
#7 ·
I've just modelled a ported box with your dimensions. In metric it's a 95L box with a slot port the width (40cm)of the box x 2.5cm high and 67cm long, giving a net volume of about 89L, and tuning of 21Hz.
Port velocity kept under 32m/s with 450W of power. Round port not suitable.
106dB at 18Hz and 114dB at 50Hz. Even this box wins over the sealed.

Jason
 
#8 ·
I decided to go with the sealed box 18x18x15.5 anyways. I could not find a port option I liked and prefer the sound of a sealed subwoofer. I also like the options that gives me for driver upgrade in the future to a 15" Ultimax.

I started the build today and I can assure you it has already run way over budget but I will have tools for future builds I did not have before. I also really stink at cutting things straight with a circular saw. Hopefully they are "close enough" and seal well enough with wood glue and caulk.
 
#9 · (Edited)
Yellow is a pair of Tidal Audio subs, red is a pair of Dayton Ultimax 15's with upgraded iNuke 6000 in the future. Obviously with some equalization these things can be flat and loud in room probably near reference levels at primary seating position. Thank you btw. I did not know winisd did excursion stuff.

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#11 ·
Make a straight edge guide out of MDF. Then you can use it everytime you use your CS for straight lines.
 
#12 ·
I am building 2 separate enclosures. 1 sub each enclosure. I'm just duplicating the box volume in WinISD for simulation... Is that not correct? I did start to use a straight edge piece after the first few cuts but after measuring 6-7 times cutting once I still managed to make mistakes of course. I failed to make appropriate adjustments for blade thickness etc. All is not lost I have extra wood and may need to cut additional pieces, we'll see how they test fit.
 
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