Help! Cab tuning difference between kappa 15A and kappalite 3015? (solved!)

[walterw]

i tried firing up winISD as well as a couple online speaker box calculators and couldn't make heads or tails of any of it

i have nice little single 15 cabs that don at LDS designed around the kappa 15A (the cheap one, not the pro); near as i can tell they're 23 1/2" by about 18" by about 15" on the outsides, with two 4" round ports that are maybe 6" deep. with the kappa As they're surprisingly solid on the low end, my 4-string really feels "supported" on the low notes.

i recently swapped speakers for the 3015s (non LF) in pursuit of lighter weight (of course) and maybe a bit more mids and highs. it still sounds good but i notice them kind of farting when i hit the low notes hard (one side of a QSC PLX 3002 for 900w into two cabs, 30Hz filter engaged).

what's the tuning difference between these two drivers, and is there an easy improvement to be made by say adding to the length of the port tubes?

 

[Downunderwonder]

That's a lot of amp for 215 even if they are the fancier kind. Without firing up the winISD myself it looks like a simple case of too loud too low. Raise the HPF or lower the low EQ and ease up on the loud knob.

 

[Rick James]

For best results the 3015 needs a 2.8 cubic foot (net) cab tuned to 45 hz, with a 40 hz high pass. You cabs are probably big enough but a 30 hz high pass is too low, at 30 hz they run out of excursion with only 70 watts. How Don might have calculated the box for a Kappa 15 only he can say, because that driver works best in 5 cu ft (net) tuned to 33 hz, so it wasn't a perfect match.

 

[jnewmark]

With the QSC, you could raise the HPF to 50 hz, no ?

 

[kpc]

I would imagine cab and speaker are not a match.

 

[walterw]

With the QSC, you could raise the HPF to 50 hz, no ?

that is indeed something i will try next.

i tried it once long ago with the old speakers and hated it, seemed like the sound was "missing" even though i had the rig up way too loud. at the time i was relying on it to hear myself in loud bands on little stages.

these days i'm pretty much always on in-ears so i never need to push the rig anymore.

 

[walterw]

For best results the 3015 needs a 2.8 cubic foot (net) cab tuned to 45 hz, with a 40 hz high pass. You cabs are probably big enough but a 30 hz high pass is too low, at 30 hz they run out of excursion with only 70 watts. How Don might have calculated the box for a Kappa 15 only he can say, because that driver works best in 5 cu ft (net) tuned to 33 hz, so it wasn't a perfect match.

thanks for the math!

yeah, i'm gonna try again with the 50Hz filter on my QSC; it looks like that filter is 3dB down at 50, with a little fullness bump at 100. (i find myself wishing it was a 40Hz filter, that seems more normal.)

i'm just rocking a 4-string in Eb, so the nominal low note of Eb and its theoretical 39Hz or even when i "drop D" and am supposedly putting out like 35Hz at that Db, the real result is mostly a hint of fundamental and lots of that 78 or 70 harmonic.

so in general, does shortening or lengthening the port tubes raise or lower the box tuning? which does what?

 

[kartiste]

thanks for the math!

yeah, i'm gonna try again with the 50Hz filter on my QSC; it looks like that filter is 3dB down at 50, with a little fullness bump at 100. (i find myself wishing it was a 40Hz filter, that seems more normal.)

i'm just rocking a 4-string in Eb, so the nominal low note of Eb and its theoretical 39Hz or even when i "drop D" and am supposedly putting out like 35Hz at that Db, the real result is mostly a hint of fundamental and lots of that 78 or 70 harmonic.

so in general, does shortening or lengthening the port tubes raise or lower the box tuning? which does what?

Lengthening lowers the tuning. Reducing the area lowers the tuning.

 

[walterw]

How Don might have calculated the box for a Kappa 15 only he can say, because that driver works best in 5 cu ft (net) tuned to 33 hz, so it wasn't a perfect match.

having just looked back over my email chain with don, he said he tuned the boxes for 52Hz with the kappa A.

makes me wonder what gluing an additional inch or two of tube length onto the ends of the ports would do?

 

[Downunderwonder]

From memory.
Select driver.
Select box style, box volume, port style, number of ports, size of ports,

Telling it desired tuning it gives port length.
Giving it port length tells you tuning.

 

[walterw]

From memory.
Select driver.
Select box style, box volume, port style, number of ports, size of ports,

Telling it desired tuning it gives port length.
Giving it port length tells you tuning.

maybe that was an earlier version, but i couldn't even get that far with the new winISD.

 

[Foz]

I'd just tune it - lean it on its back and sprinkle some salt/rice on a cone - feed a few volts of 42 Hz into the cab - when the salt stops jumping Bob's your ankle.

 

[JimChjones]

makes me wonder what gluing an additional inch or two of tube length onto the ends of the ports would do?

I've recently built a cabinet for a speaker I didn't have numbers for, and found that while doubling port length had a big impact on the impedance curve, it didn't change the sound too much. But my amp seems to have a high pass which has a slope starting at 63, so maybe it's chopping out a lot of the fundamentals.

 

[Rick James]

The correct box size and tuning for the specs will get the most out of a driver, but it can't get out of a driver what it doesn't have to give.

 

[walterw]

so i did a lower volume "acoustic" gig (drums, electric bass and acoustic guitar) w/ one cab over the weekend, and i took the opportunity to switch back and forth between the 30Hz and 50Hz filter on my power amp.

it was a cavernous, boomy ballroom and my one cab was on the floor so kinda hard to really tell without blasting my rig, but it seemed like at 50Hz the speaker tightened up without becoming anemic, a little more like a recorded and mastered bass tone rather than a "live" bass tone.

switching back to 30Hz i didn't really hear more low end, it was just a bit looser-sounding.

i'll compare again next weekend, where i'm using the full stack on a much more dead-sounding stage so it should be much easier to hear the difference.

i still find myself wishing the filter on the amp had a 40Hz setting, that seems like it would be just right.

 

[walterw]

to bring this back around, after a bunch of gigs with the new speakers i don't find myself worrying about it anymore, it sounds great just like it is! i'm still running the amp with the 30Hz filter.

i may indeed have just been pushing the cabs too hard in that initial test.

 

[walterw]

OK, delving in again, i think i got the newest winISD to sort of work for me.

i had to manually load in all the specs i could find for the 3015, and as near as i can tell my cabs are right at three cubic feet internal.

using those stats, with my two 4" round and approx 6" deep ports that gave me about the low 50s tuning that matched up with what don O told me the cabs were.

the software is kind of awkward in that i couldn't like enter the port size and length and see the tuning results; i could only tweak the given tuning frequency and then see what length ports it called for to get there.

if 45Hz is the magic tuning for the 3015 then i think i can get there by adding about 2"-2 1/2" to the port tube lengths; i've got some extendy flange things coming from parts express to try that out.

the "transfer function" curve as well as the SPL curve showed a slight bump and then a steep dropoff at the 52Hz tuning but a sloping flatter rolloff at the 45Hz tuning, less SPL at the tuning frequency. if that translates to a tighter low end with less unloading of the speaker than i might be cool with that.

it showed the speaker excursion as being the least right at the tuning frequency so bumping that down to 45Hz might be good (since there would be less stuff below it causing overexcursion and "farting out") but what i couldn't tell is whether the lowered tuning and excursion (and reduced SPL) translated to more power handling down there or less.

 

[walterw]

i guess i'm really trying to turn these cabs into greenboy bassic 15s

 

[HaphAsSard]

it showed the speaker excursion as being the least right at the tuning frequency so bumping that down to 45Hz might be good (since there would be less stuff below it causing overexcursion and "farting out") but what i couldn't tell is whether the lowered tuning and excursion (and reduced SPL) translated to more power handling down there or less.

Down there, short answer is more. The two dips in mechanical power handling are a ways below the tuning freq area where the resonance ceases to contain the excursion of the speaker, and the latter gets unloaded, and above, where the bump in the response is; the latter dip can be eliminated with a high tuning, but the con in doing that is that the former (bottom) dip region extends to the lowest fundamentals. Vice versa, a low tuning can move the bottom-end unloading region into frequencies that don't actually make to the driver because the bass doesn't produce them in the first place, and/or the built-in high pass filter in the (pre)amp filters them out; the upper bass power dip will however become more pronounced in that case. All the above depends on the Xmax of the driver, airspace (internal size of the box), but also on the power input: if you get the SPL you need before Xmax is reached in either area you're good to go.
Now, the "Maximum Power" and "Maximum SPL" plots show the power dips, while the "SPL" one (sound pressure curve at the input power you've entered in the "Signal" tab of the project) doesn't; however, if you go to the "Advanced" tab - right below "Signal" - and tick the "SPL graph is Xmax limited" box, the dips will be shown there as well.

the software is kind of awkward in that i couldn't like enter the port size and length and see the tuning results; i could only tweak the given tuning frequency and then see what length ports it called for to get there.

Hm, in my version (0.7.0.950) the port opening size (diameter if round, width and height if rectangular) is enterable, as are tuning frequency and no. of ports, then the length is auto-calculated.

 

[walterw]

Down there, short answer is more.

awesome, and thank you.

Now, the "Maximum Power" and "Maximum SPL" plots show the power dips, while the "SPL" one (sound pressure curve at the input power you've entered in the "Signal" tab of the project) doesn't; however, if you go to the "Advanced" tab - right below "Signal" - and tick the "SPL graph is Xmax limited" box, the dips will be shown there as well.

oops, don't think i entered anything for "signal", that might be why some of those are showing as flat lines

Hm, in my version (0.7.0.950) the port opening size (diameter if round, width and height if rectangular) is enterable, as are tuning frequency and no. of ports, then the length is auto-calculated.

you're right, that's what i have too. i can pick port size and number, it determines length.