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Discussion Starter #1
I have a cheap subwoofer and a decent sealed enclosure. I'd like to convert the sealed enclosure to a bass reflex, however. I am assuming I should use a 4" port to reduce port whistling, but I have no clue what length it will need to be. I don't necessarily need more SPL up high but I want more low-end extension. I have no problem using PVC elbows in order to increase the clearance for port length (am in fact expecting it).

Here are the manufacturer's parameters for the woofer.

* Speaker Size (cm): 30
* Speaker Size (inch): 12
* Peak Power (W): 1300
* Rated Power (RMS, W): 380
* Impedance (ohms): 4
* Sensitivity (dB/W/m): 89
* Frequency Response (Hz): 18 - 2,000
* Mass (kg): 4.5
* Mass (lb/oz): 11
* d (mm): 250
* d (inch): 9.8
* Rdc (ohms): 3.3
* Fs (Hz): 24.8
* Qts: 0.37
* Qes: 0.39
* Qms: 7.02
* Vas (Lit.): 86.7
* Vas (Cu. ft.): 3.06
* Mms (g): 162.1
* Lvc (mH): 1.1
* Xmax (mm): 5.7
* Xmax (inch): 0.2
* BL (Tm): 14.1
* Sealed Enclosure Vol. (Net Lit.): 32.7
* Sealed Enclosure Vol. (Net Cu. ft.): 1.15
Right now it is a 2.27 cu ft sealed cabinet. Will this woofer perform in a ported enclosure? What should I do??
 

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Discussion Starter #2
I used the AJ Vented Designer software and it recommends a 2.053 cu ft enclosure with a 4" diameter, 19.9" long port.

Would the slight increase in enclosure volume effect the needed length of port, and if so, in which way (longer or shorter)?

I noticed that, according to the software, the Fs of the woofer is 24.8 Hz but F3 of the enclosure is 28.9 Hz. Is it normal for the vented enclosure to have a higher resonate frequency than the driver?
 

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I am not familiar with that software, but according to WinISD, I am showing about a 3ft^ft box with a 4" port at 16" long which will tune it to about 25Hz. But to keep the driver from over excursion with only 100 watts of input power, you would need to apply a 4th order HPF at 20Hz.

If you have an amp... for a couple hundred dollars you could do a LOT better.

Are you absolutely sold on using this driver?
 

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Discussion Starter #5 (Edited)
I am not familiar with that software, but according to WinISD, I am showing about a 3ft^ft box with a 4" port at 16" long which will tune it to about 25Hz. But to keep the driver from over excursion with only 100 watts of input power, you would need to apply a 4th order HPF at 20Hz.

If you have an amp... for a couple hundred dollars you could do a LOT better.

Are you absolutely sold on using this driver?
Only 100 watts? I'm driving it with a Peavey IP-8.5C stereo amplifier which is capable of 850 watts RMS bridged into 4 ohms.

This driver has no sentimental value. ;) The only issue is cost; I'd have to sell this one before I can get another. I'd be willing to sell the driver and the enclosure together, though; if I had a better driver I'd custom build the enclosure to suit it.

A LOT better? How much is a lot? I'm very green in the Hi Fi HT area.

Edit:

If I do try to sell this sub, I would still want to port it; I could probably get more money out of it with nothing but a few dollars worth of PVC pipe and some time.
 

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I guess it depends on whether you watch many movies or just listen to music. If you watch movies, a better sub would do you wonders. If you listen to music and only listen at lower volumes, you will be fine with what you have. You certainly won't be getting your money's worth out of that amp though.

How big of a box can you build? Can you do a 4, 5, 6... even 10ft^3 box? What's your limit?

You could gain extension down to 15Hz.... and increase SPL by 10-15db with a better driver and that amp. Does that amp have a HPF (Subsonic filter)?
 

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Discussion Starter #7 (Edited)
I guess it depends on whether you watch many movies or just listen to music. If you watch movies, a better sub would do you wonders. If you listen to music and only listen at lower volumes, you will be fine with what you have. You certainly won't be getting your money's worth out of that amp though.

How big of a box can you build? Can you do a 4, 5, 6... even 10ft^3 box? What's your limit?

You could gain extension down to 15Hz.... and increase SPL by 10-15db with a better driver and that amp. Does that amp have a HPF (Subsonic filter)?
My current system sounds good with music. I built the system for movies, though. Deep bass extension is my goal; I upgraded from a pair of 8" Rampage woofers in a half-cubic foot box (blown by this amp), to this sub. 15 Hz would be superb. :bigsmile:

This amp has no filters whatsoever. HERE is the amp on Peavey's website. I'm willing to build as big of a box as is necessary.
 

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I think we can come up with some good options.

I am spent for tonight though... I will see what I can come up with on some modeling tomorrow. :T
 

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If deep bass extension is your goal then sell this sub and get what you can for it. With a Xmax of 5.7 mm this sub won't get the job done. You can port the cabinet it's in now with a 3 inch port 12 inches long. That will tune the cabinet to a bit under 26 hz and it will be a big improvement over the sealed cabinet.

What would your budget be for another sub driver?
 

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Mike definitely has a good point. If you want large dynamic capabilities while achieving low extension you will want a larger driver in a proper vented cabinet. With a budget it will be very possible to make recommendations that will most ideally fulfill this goal.

One thing to note: With such low frequency extension goals a relatively large cabinet will likely be required if maximum dynamics are to be achieved.
 

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Discussion Starter #11
Box size is of no concern; I know there's no such thing as a free lunch.

Money-wise, I'd have to see how much I can get for my current sub; I just spent my budget's worth for Christmas presents.

I do want to know what my available options are, though, and what I can expect for performance compared to what I already have.
 

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Discussion Starter #13
The available options are going to depend on how much money you are willing to spend on a sub. At least give a price range. There's no sense even talking about a $450 sub if you only want to spend $250.
Well I would say that $250 would be on the extreme top-end of the price range.
 

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If size is not a concern you have made life fairly easy for yourself. A cheaper solution would be the Dayton RS 15" subwoofer that can be purchased via Parts Express coming in at about $150. This would be approximately 11 cubic feet plus bracing and a slot port/large radius round port.

Another high quality option at the top of your price range is the CSS SDX15 which was measured by Ilkka in a sealed configuration here.

With the output levels you seem to want and the low reach you are asking for I would not recommend using a driver smaller than 15" unless you used a highly linear device. Even in such a circumstance approximately 4-6dB output loss would be typical with such a low tuning and small driver.
 

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Here are 3 popular choices in the $155 to $225 range

Mach 5 Audio MJ-18M $155 shipping included.
Mach 5 Audio IXL-15.2.2 $220 shipping included.
Exodus Audio Shiva-X 12". $182 plus shipping.

Here is some modeling comparing the above 3 and your amp to what you have now. Be aware the Peavy 8.5C will not do 4 ohms bridged. Its output power is:

270 Watts/ch 8 Ohms
425 Watts/ch 4 Ohms
550 Watts/ch 2 Ohms

and 850 watts, 8 ohms bridged.


Yellow- guess which one this is!
Green - IXL-15 in 6 cu.ft. tuned to 18 hz with 500 watts to each coil, 2 ohm load each coil.
Orange - MJ-18M in 10 cu.ft. tuned to 18 hz with 425 watts applied to a single 4 ohm coil. (This sub will take 700 watts in this setup, your amp will only produce 425 watts into 4 ohms.)
Pink - Shiva-X in 6.3 cu.ft. tuned to 18 hz with 425 watts applied. (excursion limited)

Pinhead.JPG
 

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You're missing the SPL graph of the expected output in post #15. Explod - 87 db at 18 hz, IXL-15- 114 db at 18 hz. I'm not familiar with the program you are using, but it appears to be showing the frequency response of the sub, not the SPL it will achieve with a specific input power.
 

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Discussion Starter #18
You're missing the SPL graph of the expected output in post #15. Explod - 87 db at 18 hz, IXL-15- 114 db at 18 hz. I'm not familiar with the program you are using, but it appears to be showing the frequency response of the sub, not the SPL it will achieve with a specific input power.
Yes, it only shows the frequency response; the program is designed to make a box that produces the flattest frequency response. What would 114db of bass sound like and compare to? I had a pretty phenomenal car stereo back in the day, but I have no clue how that level of volume would translate to dB's...

How would these speakers respond to an LLT enclosure? I read the LLT Explained sticky a couple of times but I'm still not sure what the sound difference would be when using the same driver when compared to a conventional bass reflex system. How would my driver perform in an LLT enclosure?
 

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The drivers Mike has recommended are basically modeled for LLT enclosures. 6-10ft^3 is larger than you typically see in commercial subs.

Try out WinISD... it's free and we have a great tutorial to help you use it. We also have most all of our sponsor's driver parameters available for download.
 
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