Vox 3012LF/Alpha 6A cabinet tests

[johnk_10]

Older drivers sound smoother simply from being very well broken in. With accelerated break-in over the course of a few days the initial harshness of new drivers can be fixed. Or you can just play them for a few years.

i'm going to run the cab with a freq generator sweeping it thru a sub range for a while to see if it'll loosen them up a little.

even after extensive use, i still don't think that a 3015 will ever have the same frequency response and tone of a K140. they're just two different animals.

 

[johnk_10]

here's some winISD results comparing 2-3012LF's to two JBL K140's, using the dimensions and porting of my two cabs.
(the 3012LF is in green and the JBL in red

SPL:

Gain:

they appear to be pretty darn close to me,especially at 50hz and i can hear that the JBL's are more sensitive by about 2 1/2dB, just as the program depicts.

 

[rpsands]

You might want to take a peek at cone excursion and SPL with a ~1000w signal (the GK should be able to put out peaks of that high I'd think). I don't have a file for the K140 or I'd be happy to model it.

Might also want to compare a 3015LF in there.

 

[Passinwind]

here's some winISD results comparing 2-3012LF's to two JBL K140's, using the dimensions and porting of my two cabs.

Now try modeling the 3012LFs in 4.6 cu ft, tuned at 44 Hz.

 

[billfitzmaurice]

Gain:

-3dB at 60 Hz indicates the box is too small for the 3012LF; with 2.2 cu ft and a 40 Hz Fb you'll get a 45 Hz F3.

The thing about low Qts drivers is that they'll reach their maximum low frequency potential in a very small box. The bad news is that potential is limited, and putting them into a larger box doesn't get much more out of them.
For a more apples to apples comparison model the K140 and 3015.

 

[johnk_10]

yeah, i know its too small to get what they're capable of, however i didn't like the cab (2.7cu ft volume) at all with just one of them and its actually a very usable cab the way that it is right now. the JBL's don't have all that much down there either, but i love the way that they sound.

the premise wasn't so much to maximize the 3012LF's low end potential, but rather to see if i could get the small cab to sound and feel as close as i could to the big one, and i feel that i've accomplished that. the little one is so much easier to load and unload and makes alot more room in my car for hauling other gear.

i'm going to try moving the xo point on the 3012LF's up to 950hz as opposed to where it is now at 850hz since it seems that the JBL's have a little more going on at 1k than the 2x12 cab does right now. the Alpha 6A is crossed over at 950hz so it may remove the slight dip that the cab has at around 1K now. for me, at this point, instead of modeling it with winISD, its just trail and error until i get it the best that it can be, for my taste. i have a feeling that it'll probably be hard to tell changing the xo point from 850hz to 950hz without doing it with a switch, as opposed to opening up the cab, rewiring the xo and then re-testing it.

 

[johnk_10]

before i change the x-over, do any of you speaker experts think that crossing the 3012LF's over at 950hz is too high (as opposed to the 850hz that it is now)?

i don't want the cab to bark at me, but it just seems a tiny bit scooped to me right now.

 

[billfitzmaurice]

before i change the x-over, do any of you speaker experts think that crossing the 3012LF's over at 950hz is too high

Too low IME. With its dispersion there's no need to go lower than 1kHz.

 

[rpsands]

Bill, your philosophy seems to be that big peaks are OK because adequate eq can control them, but something to bear in mind here is that John is trying to achieve a sound without any corrective eq.

John, I really think you need to measure the K140 and then calculate your crossover based on what's going to match you up with a flattish (from your amp) signal through the K140.

 

[johnk_10]

Bill, your philosophy seems to be that big peaks are OK because adequate eq can control them, but something to bear in mind here is that John is trying to achieve a sound without any corrective eq.

that's exactly right. or at least with minimal eq changes.

John, I really think you need to measure the K140 and then calculate your crossover based on what's going to match you up with a flattish (from your amp) signal through the K140.

+1!
i've been running some RTA tests on it right now. the 3012LF cab definitely has a little more subs, but its the mid bass and midrange (i.e. where alot of the detail and K140 vibe lies) that i'm trying to duplicate.

 

[billfitzmaurice]

Bill, your philosophy seems to be that big peaks are OK because adequate eq can control them, but something to bear in mind here is that John is trying to achieve a sound without any corrective eq.
.

My philosophy is that all musical instrument drivers have peaks, it's in their nature, so there's no need to be especially concerned about them. Unfortunately I don't happen to have a chart of a K140 handy, but my guess is that what he likes about the K140 is its midrange break up mode.

 

[rpsands]

If I had to go with my gut I would cross the 3012LF very low to the Alpha and pad the alpha back a little, I think you'll get a better midrange that way. The breakup mode of the 3015LF at least I can say is really offensive to the ear and sounds way different and way worse than my old JBL D140s - which were quite pleasing to the ear in the mids.

I'd go way low and try like 600hz or so.

The reasoning for that is kinda tenuous really but I find that Alphas and Betas sound a little more "old school" to me in the mids than the Kappalites so the more you send to the alpha the more you'll like it I think.

 

[johnk_10]

here's the results of my 'quick and dirty' test, which seems to verify that the 3012LF cab is lacking a little in the 800-900hz range. the 3012LF reading is on top, and the K140 is on the bottom.

you can also see that the 3012LF cab has a more pronounced high end starting at 3.5K but really is more drastic above 5K. that's really not an issue for me since i can always cut the treble on the head. (the GK's treble control is at 7Khz). and when i install a mid attenuator, i can adjust it a little more.

 

[billfitzmaurice]

The breakup mode of the 3015LF at least I can say is really offensive to the ear and sounds way different and way worse than my old JBL D140s - which were quite pleasing to the ear in the mids.

Apples and oranges. The only JBL that approached the specs of the 3015LF was the K/E 145. I never heard one, so I can't attest to how it sounded, and like most of those old JBLs charts on them are impossible to find, which is odd, as you can find EV and Altec charts with little difficulty.

 

[billfitzmaurice]

here's the results of my 'quick and dirty' test, which seems to verify that the 3012LF cab is lacking a little in the 800-900hz range.

I assume that's with a mid driver, and if so I'd look at the crossover. All the 3012LFs I've measured come quite close to the Eminence data sheet chart.

 

[rpsands]

here's the results of my 'quick and dirty' test, which seems to verify that the 3012LF cab is lacking a little in the 800-900hz range. the 3012LF reading is on top, and the K140 is on the bottom.

you can also see that the 3012LF cab has a more pronounced high end starting at 3.5K but really is more drastic above 5K. that's really not an issue for me since i can always cut the treble on the head. (the GK's treble control is at 7Khz). and when i install a mid attenuator, i can adjust it a little more.

Yeah, I think padding the 6a back is going to be where it's at, but you're going to want to line up the overlap in such a way that you don't get a "scoop" of course.

The nice thing is, when you pad the 6a back, you can cross it over lower, which should make lining it up easier.

Least, that's what it looks like to me

 

[alexclaber]

...its the mid bass and midrange (i.e. where alot of the detail and K140 vibe lies) that i'm trying to duplicate.

As Bill says I bet it's the break-up modes of the K140 that you like and unfortunately effectively EQing your 3012LF cab through crossover tweaking will only change the response curve, it won't change the distortion characteristics.

Alex

 

[johnk_10]

Yeah, I think padding the 6a back is going to be where it's at, but you're going to want to line up the overlap in such a way that you don't get a "scoop" of course.

The nice thing is, when you pad the 6a back, you can cross it over lower, which should make lining it up easier.

Least, that's what it looks like to me

i think that you're correct. i'm going to start by crossing the 3012LF's over at 980hz first, and test it.

if it still has the dip, i'll then try crossing in the 6A at 900hz, instead of 950 where it is now, but it may not make much difference.

BTW, here's the TS specs for a K140:

 

[johnk_10]

As Bill says I bet it's the break-up modes of the K140 that you like and unfortunately effectively EQing your 3012LF cab through crossover tweaking will only change the response curve, it won't change the distortion characteristics.

Alex

i completely agree with you, that no amount of eq is going to duplicate the actual feel and distortion of the K140, however, i can hear the dip in the freq response curve, so i'm going to try changing it to 980hz right now.

 

[billfitzmaurice]

i think that you're correct. i'm going to start by crossing the 3012LF's over at 980hz first, and test it.

if it still has the dip, i'll then try crossing in the 6A at 900hz, instead of 950 where it is now, but it may not make much difference.

BTW, here's the TS specs for a K140:

Those I have, it's SPL charts that are made of unobtainium.