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Vox 3012LF/Alpha 6A cabinet tests

#61
Success! i raised the 3012LF's x-o point to from 850hz to 980hz, and installed an adjustable L-pad on the 6A. dialing the 8 ohm L-pad's pot to just under half way it has made the cab ALOT closer to the K140's, and it doesn't sound or feel like it has the dip at 1khz anymore. i really cranked it up and this cab ROCKS now. with just a little nudge on the volume it can get just as loud and full as the dual K140 cab, and its hard to believe that such a small cab can sound so HUGE! it took me awhile, but all the time and money spent on it was more than worth it.

all i have to do now is break them in.

i want to thank everyone for all of their input!
 
#62
billfitzmaurice said:
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.
Click to expand...

It's very easy if you know where to look ;) FR, Z and distortion measurements from Greg Timbers himself:

E145
 
#63
BTW, here's the results of the last RTA test that i ran today using a pink noise generator.
All readings taken with the GK1001RBII head's controls set at 12:00 (zero contour, zero presence)

the top one is the 3012LF's crossed over at 850hz. (taken earlier today)
the middle one is the 3012LF's crossed over at 980 with about 5-6 db mid attenuation.
and the bottom one is the JBL K140 cab.

RTA_results-2.jpg


after changing the x-o point and attenuating the 6A, and playing thru it, i could immediately tell that the cab sounded alot more like the K140's before running the last analyzer test, and the RTA seemed to verify it, as the middle and bottom readings are pretty similar, especially for being two completely different sized cabs with completely different drivers. it appears that the JBL's do have a dip at around 2.5K, and the 3102LF/Alpha 6a is pretty flat in that range, but that's something i can live with. ;)
 
#64
Pretty remarkable work man :) Glad you got what you wanted out of it - seems to confirm my suspicion that many, many players would be just fine with a 3015LF or a pair of 3012LFs and a lower end mid driver than the 6nd410.

Personally I think I would have gone with a parametric eq and a ~1.5 octave -5db cut @ 3khz, but it's definitely a cool exercise to have a crossover that "vintagizes" the midrange automatically.

What'd your components count come out to in rough dollars for the xover?
 
#65
rpsands said:
Pretty remarkable work man :) Glad you got what you wanted out of it - seems to confirm my suspicion that many, many players would be just fine with a 3015LF or a pair of 3012LFs and a lower end mid driver than the 6nd410.
Click to expand...

thanks! yeah,in my case, i saw no reason to get a higher end/higher efficiency mid driver when i don't really prefer to have a snappy high end.

rpsands said:
Personally I think I would have gone with a parametric eq and a ~1.5 octave -5db cut @ 3khz, but it's definitely a cool exercise to have a crossover that "vintagizes" the midrange automatically.
Click to expand...

yeah, i was deliberately going for the 'vintage' tone without having to use any extra outboard devices to achieve it. now i can just take either cab and get basically the same sound out of either one of them. the best thing that came out of this is that now, i know i can fairly closely replicate a vintage JBL cab with modern, lightweight components.

rpsands said:
What'd your components count come out to in rough dollars for the xover?
Click to expand...

i bought an assortment of values of coils and caps to experiment with, but i get them at dealer's cost. the coils that i used (a 1.3mH-15ga. and a 2.7mh 16ga.-Jantzen) ran me about $30.00, the two caps (20uf and 10uf made by Erse) ran about $3.50 each, and the 100 watt 8 ohm attenuator pot was $12.00.
 
#68
rpsands said:
seems to confirm my suspicion that many, many players would be just fine with a 3015LF or a pair of 3012LFs and a lower end mid driver than the 6nd410.
Click to expand...

You are always going on about that. But I find it preferable to adjust crossover and L-pad values if I want a different tonal balance. Because if you find at some point you are really hitting the cab with big wattage to the limits of what the woofers can deal with then your midrange can definitely still keep up, with a sufficient safety margin.

Not so different than using compression drivers that are really sensitive and padding them back, really. Power handling safety margin ... A lot of home builders are using compression drivers padded way back instead of dome tweeters, partly because that also gives a better main signal to harmonic distortion figure than can be had with a dome tweeter.
 
#69
greenboy said:
Because if you find at some point you are really hitting the cab with big wattage to the limits of what the woofers can deal with then your midrange can definitely still keep up, with a sufficient safety margin.
Click to expand...

Toasting midrange drivers is an expensive habit! The more sensitivity and power handling, the better!

Alex
 
#70
greenboy said:
Though if one couldn't accommodate to the different voicing IN AN ACTUAL MIX I'd probably prefer at that point to use EQ rather than add additional crossover circuitry.
Click to expand...
I'm the last one to recommend using anything passive in lieu of active, but my impression is that the OP doesn't care to use active correction.
 
#72
greenboy said:
You are always going on about that. But I find it preferable to adjust crossover and L-pad values if I want a different tonal balance. Because if you find at some point you are really hitting the cab with big wattage to the limits of what the woofers can deal with then your midrange can definitely still keep up, with a sufficient safety margin.

Not so different than using compression drivers that are really sensitive and padding them back, really. Power handling safety margin ... A lot of home builders are using compression drivers padded way back instead of dome tweeters, partly because that also gives a better main signal to harmonic distortion figure than can be had with a dome tweeter.
Click to expand...

Right, and I've never once said it was preferable period in any technical way and I am not advocating that DIYers do it with a fEarful in general (although if I was doing a 3012LF, I would not use a 6nd410 for a single one under any circumstances, just ridiculous to pad something back 10db;).

What we see here though is someone being happy with an Alpha 6a padded back 5db with 2 3012Lfs to support (and frankly with the 6nd410 padded back 6db with a 3015LF, I am not really bothered).

Which indicates to me that commercial cabinet companies could, since they are so bloody cheap, get away with an in-between midrange and still make a better sounding cabinet in many cases than is currently available.

I know pretty much all of the reasons for going with the 6nd410 - which is why I shelled out for it :)
 
#74
rpsands said:
although if I was doing a 3012LF, I would not use a 6nd410 for a single one under any circumstances, just ridiculous to pad something back 10db;).
Click to expand...

More like 8 dB (not that passive fixed L-pad values always end up being what you'd expect), and switchable, so that one can use a 12/6 on top of 12sub for some gigs. Not everybody wants a dark voicing, and when they do, they don't want it all the time. Most of the people who've been interested in that approach seem to prefer flexibility over a limited tonal profile.
 
#75
rpsands said:
How much power would the OP need to put through his cab to toast an alpha 6a crossed at 980 hz with a 5db pad on it?
Click to expand...
About 1500w, give or take, assuming a clean signal. But dirty it up and that figure will drop like a stone, so I wouldn't use less than one per woofer, two with a 3015LF.
 
#79
koobie said:
OP, I'd like to hear what kind of tonal results you get with some of the other heads you own. And do you have a pic of the interior of the cab with your latest driver arrangement?
Click to expand...

i'll take a pic of its internals and post it later today.
which head would you like to hear thru it? right now, i have access to my SVT, a '72 V4B, a Fender Super Twin head, a Sunn 2000s, a Sound City Bass 150, and of course the GK 1001RBII. all my other heads are so buried in my back room that they're a bit hard to get to.

BTW, even though this cab is not 'bright' sounding, it isn't at all dark sounding either. to me, it just sounds like a great JBL cab, that doesn't have any crossovers or mid drivers in it. i have an old crown active crossover, and usually when using an XO, i do prefer using an active one, but the whole premise of this build was to be able to take this small cab to a gig in place of the large 2x15 cab, with no other outboard gear, or using a preamp / power amp / XO as a head. IMO, it ended up sounding like what i want out of a great sounding standard non 2-way bass cabinet. i have played thru it at a higher volume than i'll probably ever need to with the GK head, at it doesn't appear to have a problem handling it. i never thought that i'd say this, but it seems to be capable of getting (in the ballpark) as being as loud and full as my Ampeg 8x10 cab, and to me, that's pretty incredible. of course, it may take a little more watts to get it there, as the 3012LF's aren't really very efficient speakers.
 

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