I've got a little problem along similar lines, so I didn't think it needed it's own thread.
I need a little help with a 2x15 bass extension cab to pair with a 2x12 that has great mid-low tones, but is missing smooth rumbling lows. It is relatively a low wattage system. The 2x12 handles 300watts and 2x15 will handle about 200watts both RMS values.
The 2x15 is roughly based upon the guidelines laid out in EV’s Bass Reflex Tech Bulletin 10A. Internal measurements are 45”h x 30”w x 15”d giving a volume of about 20250 cuin or 11.7 cuft. What’s giving me trouble is figuring the port dimensions. The chart just doesn’t make any sense to me. According to the bulletin the effective port area should be equal to the diaphragm area, in this case about 117 sqin per speaker. How do I figure the size tube or rectangular vent?
I need a little help with a 2x15 bass extension cab to pair with a 2x12 that has great mid-low tones, but is missing smooth rumbling lows. It is relatively a low wattage system. The 2x12 handles 300watts and 2x15 will handle about 200watts both RMS values.
The 2x15 is roughly based upon the guidelines laid out in EV’s Bass Reflex Tech Bulletin 10A. Internal measurements are 45”h x 30”w x 15”d giving a volume of about 20250 cuin or 11.7 cuft. What’s giving me trouble is figuring the port dimensions. The chart just doesn’t make any sense to me. According to the bulletin the effective port area should be equal to the diaphragm area, in this case about 117 sqin per speaker. How do I figure the size tube or rectangular vent?
you need to put driver specs in a speaker calculator
though you will need a minimum port size, it will also change the port length, or tuning, or box size, depending on what you want to achive
I had thought I would be getting a little better advice. I have already used calculators and found them to be useless.
The online calculators all seem to go nuts when you start using a cabinet volume of this size. I end up with tubes being in negative measurements using http://www.lautsprechershop.de (reccomends sealed).
Here Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators. A 4” tube about 1 11/16” in length. Using a tube less than 4” gives a negative value.
Yet another says 4.31 for single or 11. 55 for two PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES.
I’m trying to tune the cab to within the 25-28Hz range.
Funniest of all, none really take the Thiele-Small parameters into account, and none come close to the chart.
The drivers have similar specs as the SRO 15s but higher wattage rating @ 16ohms. That's what I used as a baseline for calculating the cabinet volume. The final impedance with both cabs is 6-6.15 ohms (tested).
The online calculators all seem to go nuts when you start using a cabinet volume of this size. I end up with tubes being in negative measurements using http://www.lautsprechershop.de (reccomends sealed).
Here Subwoofer Enclosure Calculators, Fraction to Decimal, Parallel, Series, Port Length and Volume Calculators. A 4” tube about 1 11/16” in length. Using a tube less than 4” gives a negative value.
Yet another says 4.31 for single or 11. 55 for two PORT Size Calculations and Formulas for WOOFER and Subwoofer BOXES.
I’m trying to tune the cab to within the 25-28Hz range.
Funniest of all, none really take the Thiele-Small parameters into account, and none come close to the chart.
The drivers have similar specs as the SRO 15s but higher wattage rating @ 16ohms. That's what I used as a baseline for calculating the cabinet volume. The final impedance with both cabs is 6-6.15 ohms (tested).
I have 3 different Eminence 12" guitar cabs. Two 1x12 and one 2x12. The 2x12 cab sounds best with about 1/2 back and the 1x12 cabs sound best with open back. All 3 cabs sound a little muffled and lose some highs when I put a back on them. Looks to me like you'd need overly bright speakers to make closed backs sound good. So open vs closed may have a lot to do with the driver itself.
Don
Okay....
I advise you to stop reading EV’s Bass Reflex Tech Bulletin 10A. It was written before Novak discovered the T/S parameters, back when a wild guess was the best they could do.
I advise you to stop wasting time with online "calculators" that don't ask for T/S specs, as they are going to assume high compliance and will be worse the the EV nomographs.
I advise you to get the exact T/S specs for your speakers - "similar to SROs" isn't close enough.
I advise you to post those specs here and let someone with decent software and some experience using it offer you a suggestion as to box size and the desirability of porting.
Just for reference, the low E on a bass guitar is about 41Hz, a guitar is 82Hz unless you down-tune. C# is ~70Hz.
BTW, I prefer closed boxes to ported boxes for musical instruments. The second order roll-off sounds fuller, and the slope makes it easier to compensate for 1/2 space.
Sure it is! It's an an open baffle with folded wings. Not a well-designed one, perhaps, but it obeys the math.
Open backs, and converting closed cabs to open backs has been rising in popularity the last couple of years. Several companies offer choices of back panels allowing 1/3, 1/3, and fully closed, as well as the oval opening popularized by Dumble. Scumback has a cab with half the back on a piano hinge, so you can adjust the openess to taste.
I think what's happening is we're all playing in smaller spaces these days and without the need to project to the back of the hall, cabs with a more open, airy 3-dimensional feel are becoming more appreciated.
Yesterday, I got a new guitar amp (60w head+ 4x8" enclosure).
The sealed cabinet is pretty large for 4x8" drivers, so the one-note bass I've mentioned previously isn't a huge problem. Bass still has to be turned down to 3/10, but it's a good (loud!) sound.
When the waranty has gone, I'll take the back off. For now, it's sufficient for bedroom practice
Chris
The sealed cabinet is pretty large for 4x8" drivers, so the one-note bass I've mentioned previously isn't a huge problem. Bass still has to be turned down to 3/10, but it's a good (loud!) sound.
When the waranty has gone, I'll take the back off. For now, it's sufficient for bedroom practice
Chris
AX84 Cabinet Plans
Many good suggestions, but since since the guy is/was building a P1, why not just try the AX84 cabinet plans? I am building a smaller one with Eminence Raging Cajun 10", and the plan looks pretty straight forward to me (as most guitar cabinets are...)
http://www.ax84.com/corecabinets.html
Jaz
Many good suggestions, but since since the guy is/was building a P1, why not just try the AX84 cabinet plans? I am building a smaller one with Eminence Raging Cajun 10", and the plan looks pretty straight forward to me (as most guitar cabinets are...)
http://www.ax84.com/corecabinets.html
Jaz
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