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Cab tuning question?

#2
Myth_103 said:
Ok, so I am building a 4x12 cab right now. 4 deltalite II 2512s. I was wondering how I'm supposed to find out the diameter and length of the tubes for ports? I want it to be tuned to around 37-40 Hz. How shall I got about doing this? My internal volume is about 9.331.
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With the same software that you used to determine your choice of drivers and the correct box size to put them in.
 
#9
Myth_103 said:
The ampeg 8x10 is around 11.549 ft^3. So, would you guys suggest I make it a tad bigger? And those 6" ports will tune it correctly?
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If I was building it, all size and weight concerns aside, I would shoot for 10 cu ft. total box vol. That's around 9.6 cu ft. if you subtract out the driver displacement and 9.6/4 = my magic 2.4 cu ft. per driver that I think graph's out nice with the 2512 II in WinIsd. It's not the strongest low bass setup, but a good compromise for the 2512 and a stronger low end than most 10" setups on the market.

Ports tune the box, not the speakers. If you make the box 10 cu ft (9.6 with driver disp) you will need to make the two 6" dia ports about 5.5" long to get 40hz.
 
#10
Just a thought, are you sure you want to tune that low? Be careful, coming from a hifi speaker building background, I assumed I wanted all the way down to the lowest string (~31 Hz for my fiver), but after reading some stuff on here (and for that matter, look at all the bass cabs out there, especially ones like Ampeg, who are known for having some serious meat to them, have an F3 of around 75Hz) I decided to got for around the 70-80Hz range and am quite happy with the result, I might have even preffered tuning it a bit higher. Just remember that what may sound great at home can sound muddy on stage.
 
#11
Make sure not to only subtract the area the drivers and bracing take up from internal dimensions, but also the area porting takes up. Depending on port design (make sure you aren't building a chuffing problem - be aware that the more power you tend to use, the more chuffing can exist so be generous in port area), that area can be a significant factor in getting it right. Also be aware that you need to use the right port compensation (one free end, two free ends, flanged etc - it's all in the WinISD Pro HELP file) to get tuning close enough - final tuning may need to be done by ear.

As far as tuning, the 2512 runs out of excursion fairly quickly, so the illusion of a low tuning driver may quickly be shattered when you go beyond xmax. That's one reason why the 3015LF is a good choice. You may want to look at some other tuning curves and slightly smaller boxes too, for the 2512. For a low B, it's nice to have fairly flat response down to 60 Hz, 55 Hz if you drop to A.

As far as "boominess" in most environments a big midbass hump arguably causes more boom than an extended bass reach does, but that big midbass hump is also a big part of an old-school sound, so choose the driver and tune/size the cab for the default voicing you think you want, and USE EQ to solve any stage/acoustics problems you may think you have (often what you think you hear onstage has little to do with what a band mix needs up front where the audience is, anyway).
 
#12
I'll also add that unless you are building toward performance the marketplace can't supply, that you better enjoy the woodwork. Frankly, rather than building a one-way or two-way cab around the 2512, I'd just buy an Avatar 212 or two, or if you want more sophisticated design, the Genz Benz NeoX 212 is really worth looking at.
 
#13
MellowTone said:
Just a thought, are you sure you want to tune that low? Be careful, coming from a hifi speaker building background, I assumed I wanted all the way down to the lowest string (~31 Hz for my fiver), but after reading some stuff on here (and for that matter, look at all the bass cabs out there, especially ones like Ampeg, who are known for having some serious meat to them, have an F3 of around 75Hz) I decided to got for around the 70-80Hz range and am quite happy with the result, I might have even preffered tuning it a bit higher. Just remember that what may sound great at home can sound muddy on stage.
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i agree with whoever said that you should use equalisation for that. that high tuning will give you that big hump around 100hz (quite severe, and very difficult to remove if you dont want it). it will also mean that you can exceed the xmax very easily, and destroy your speaker if you put much low end into it. using his design (2512 with ~2.6 ft^3 per speaker) you only need to put in 10w per speaker of 40hz to exceed xmax.

that doesnt mean playing through a 10w amp maxed, it means 10w of undistorted 40 hz. still would be a problem that you would have to look out for. easy to let some one play through it once and turn the bass right up followed by a blown speaker.

a better aproach would be a sealed cab of the right volume. it would reduce the low end by limiting xmax and be able to handle more low end (but not reproduce it too efficiently at a certain frequency). the hump wouldnt be as big either (good or bad is a matter of opinion)

im not saying your cab is bad, i just dont think that its for everyone, as im sure many would blow speakers. im glad you are happy with the cab, just wished you had mentioned the tradeoffs of the design.
 
#14
black_labb said:
i agree with whoever said that you should use equalisation for that. that high tuning will give you that big hump around 100hz (quite severe, and very difficult to remove if you dont want it). it will also mean that you can exceed the xmax very easily, and destroy your speaker if you put much low end into it. using his design (2512 with ~2.6 ft^3 per speaker) you only need to put in 10w per speaker of 40hz to exceed xmax.
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Huh? I'll make the assumption that you are talking about an 80hz tuning with the 9.33 cu ft box, but that still gives you 28w per driver to x-max at 40 hz. Not good, but not 10w. In the 40 hz tuned box that the OP wants to build it can take full RMS sine waves down to 35 hz without distortion.
 
#15
NoGraveConcern said:
In the 40 hz tuned box that the OP wants to build it can take full RMS sine waves down to 35 hz without distortion.
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It can take full RMS power between 35 and 47Hz but unfortunately power handling drops massively between 47 and 105Hz, reaching a low of 1/3 RMS power at 65Hz...

Although I can see benefits from tuning a cab to get the F3 as high as 70 or 80Hz I'm very dubious about tuning a port that high in a bass guitar cab, I wouldn't want a speaker to be unloaded from that high a frequency.

Alex
 
#17
black_labb said:
a better aproach would be a sealed cab of the right volume. it would reduce the low end by limiting xmax and be able to handle more low end (but not reproduce it too efficiently at a certain frequency). the hump wouldnt be as big either (good or bad is a matter of opinion)
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The 2512 would make a crap sealed box and the driver would still reach xmax way too early below 125 Hz. The final gotcha is that in order to get the same amount of bass response as a ported box of the same size one would have to boost for that pleasing tonality - and run out of xmax before the ported box would.
 
#18
alexclaber said:
It can take full RMS power between 35 and 47Hz but unfortunately power handling drops massively between 47 and 105Hz, reaching a low of 1/3 RMS power at 65Hz...

Although I can see benefits from tuning a cab to get the F3 as high as 70 or 80Hz I'm very dubious about tuning a port that high in a bass guitar cab, I wouldn't want a speaker to be unloaded from that high a frequency.

Alex
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I agree. The port has to be tuned to around 40 Hz. My approach is to leave it there, and "tune" the box using the box volume only. Raising the cone / box resonance produces a 12 dB/octave slope below the -3 dB point, until it reaches the port tuning, and 24 dB octave thereafter.

One might ask: If I am dialing in a 12 dB/oct slope, then why bother with the port? The reason is that the port still gives me more low end than a sealed box with the same driver, plus some measure of protection from over-excursion.

I am using around 32 liters for a single driver. My design goal was to match the response curve of another system that I was trying to emulate. However, I would not advise anybody else to blindly duplicate my design without being aware of what my design goal was.

Among the pleasures of DIY design is to try things that would cause a mainstream designer to question their own sanity. :D
 

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