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barbetta cab gets new life


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Some might recall my mention of having a Barbetta active speaker cab blowing its power amp panel. It would have cost too much to fix the old amp to justify considering the cheap availability of newer units that sound as good.

 

But in between posting and trying a couple of new ideas on my bass I decided to cut a fiberboard filler panel so that the woofer would still have complete enclosure and perform with its normal porting. I ran the woofer wires out one of the ports (leaving the tweeter alone for now) and hooked them into a 6-foot dual banana lead and plugged it into my rack and let a few hundred watts into it full-range.

 

Sounded great considering it is 18x22, by 14 deep, and weighing maybe 40 pounds. No farts on a pummeled B string, punchy, detailed enough tone for jamming and old-school demands if a little mid-bass humpy.

 

Then I sat my Carvin 210 on top of it vertically and plugged them in as a biamp setup, with crossover set at 125-140 Hz (hard to tell with silkscreening, tuned to ear). This time each cab was getting demands of a few hundred watts. Wow, smoothed the mid-bass hump out, and now I'm hearing 210 articulation too, and of course a bullet tweeter. Seems to take the wattage and deliver clean tone.

 

So, looks like I need to make a nicer back panel with a Speakon connector and maybe get that peizo horn inline with a rudimentary crossover (they sound better that way, piezos do), and I'll have a subcompact bass pumper, or a full-range cab that I won't have to worry about.

 

Hey, good comes of the bad - I'm happy to have another rig that can deal with the demands! Maybe that'll become my woofer for a polemount 2x8 / tweeter. Then, if it ever starts to go south on me I'll just put one of the new small-enclosure Magnum subwoofer drivers that Eminence recently put on the market. But somehow I think it will be awhile - it's a pretty pleasing sound and seems rock solid : }

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Here I am being "impulsive" - er, I meant, having further thoughts, following up my own post. Is there a LAW against that? ; }

 

I actually decided to gig the Barbetta and the Carvin 210 standing on top of it vertically. I did one set with each channel of my DPC-1400X driving one cab, first as full-range (gave me independent volume/gain control). I did the first and last sets bi-amped. Either way, no problems with volume or booty and I did hit full power amp output a few times just to see if everything was up to it (525 watt peaks, per cab).

 

Though the two cabs have about the same volume and blend well when set up with good alignment, running full range also tended to emphasize the midbass hump each has separately and required more low-end EQ to compensate.

 

Bi-amped with crossover at 100 Hz, it was easier to play exceeedingly loud and not have such a prominent throatiness when playing way up the neck, and to have articulation details when playing on the clean side of my preamp. It also helped the lowest frequencies seem more balanced as one cab was not reproducing much of the freqs that make for boominess, instead concentrated on the lowest octave and some. But unlike my big rig, it did take a bit of boost - maybe 3dB - at 40 Hz to really get close to what I like.

 

When I got up this morning I modeled a few other 15" drivers in this size enclosure using WinISD. Looks like the Eminence MAGNUM series really will do more than most others in a small enclosure - the 15" high output version would be perfect for this - either as a full range or subwoofer. Great SPL below 100 Hz considering this thing would weigh a little less than any 210.

 

Unfortunately, the current driver seems impervious to what I've thrown at it. I don't know how fast I can get it to blow up ; }

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Nice equipment recovery !! I think there were a few Star Wars movies about this kind of thing ;)

 

Try playing outdoors with it and crank it good. When the wildlife howls back, you can put the rig away....

 

Tom

www.stoneflyrocks.com

Acoustic Color

 

Be practical as well as generous in your ideals. Keep your eyes on the stars and keep your feet on the ground. - Theodore Roosevelt

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...So I put a simple 1st-order high-pass crossover on the rectangular piezo horn while posting and practicing today. I just wound a couple of 50-volt 4 microfarad non-polarity caps in parallel (to get 8 uf) on the tweeter's positive side and taped them to the Barbetta's amp panel (sans all the amp stuff, which I stripped off and filled the bolt holes.

 

Then I ran the negative side of the tweeter wire through what was formerly the Barbetta's AC line switch (which I left on the panel), so I could turn the tweeter on and off as desired.

 

So, without digging out the scientific calculator I figure I have about a 6dB/octave highpass on the tweeter at around 2500 Hz. I'll probably move it down to 1800 Hz or so, later when I get into town to buy another cap to bring it to 12 microfarads or thereabouts.

 

With the tweeter OFF it sounds like a really good Old School Fifteen cab; with the tweeter engaged I get stringiness and increased clarity and transient presence. That's with all the EQ set flat (it sounds a little more what I am used to with about 3dB of boost above 4 K Hz.) No hiss unless I put my ear right up to it!

 

In a cab that looks clean (grey epoxy coat and no obvious signs of mod) I've now got something that takes one side (525 watts) of my DPC-1400X power and weighs just a tad less than my 210/bullet Carvin. It sounds very fine - smooth indeed!

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Last night I spent considerable time on A/B listening tests with my newly revitalized Barbetta cab and my Carvin 210. First, in full range mode with 500 watts going into the Barbetta, I was able to make it break up when pegging the B string or the E string with 4 or 5 dB of boost at 30 Hz and the same amount of boost at 40 Hz.

 

Than I plugged the Carvin 210 into the other side of the power amp and ran them both full range; they both exhibited some scary breakup with those settings. Then I backed off the EQ, and the speaker torture was largely gone.

 

Unwilling to subject the body and ears to such extremes for more than a few moments, I also turned down the volume and played full range, noting what amplitude each open string had in relation to the others, and what playing on various regions of the neck did, volume- and tone-wise.

 

Then I simply switched to BIAMP mode, with the Xover set at 100 Hz. Again I pegged the amp gains and added the 30 and 40 Hz boosts so that average lower note would peg the LIMIT LEDs. This in comparion to FULL RANGE use, was near or equally as loud, but neither cab broke up. There was also more focus and articulation in the upper mids and treble, and also better balance between notes in various ranges, with very huge low end and lower mids were no longer so exaggerated and "humpy".

 

To make sure, I played a few more minutes with average plucking/picking intensity all over the neck, then left all other settings the same as I switched back to dual full range mode. There was perhaps a smidgeon more loudness in the lower mids now, but the cost was less clarity. And again, notes that were strong in those mid-bass and lower mids freqs tended to be weightier and didn't balance as well in volume or tonality.

 

For the next phase I switched back to BIAMP mode (beautiful to play so loud and have girth yet be able to have total clarity and definition of all nuances), and moved the Xover point from 100 Hz to 150 Hz, did some playing, then on to 200 Hz, then 250 Hz. Well, the clarity was there in the Carvin 210 in any of those cases, but its capabilities began to be wasted the further up I moved the Xover point; and the Barbetta as it was asked to reproduce a wider band contributed to some imbalance in tonality on various strings and postions - and there was some volume loss as well.

 

So: for such a rig, crossing over low seems to best use available power to its fullest extent, and exhibits smoothness and better string balance. And string-to-string tonal match, and register (where you are on the neck) balance. This beats the heck out of trying to use EQ to iron the same issues out.

 

For a final experiment of high SPL efficiency and tone, I then ran the Carvin 210 FULL RANGE, with the Barbetta functioning as a subwoofer only, at 125 Hz and below. This too had multitudinous booty and punch. But it seemed like there was just a teensy bit less clarity in the freqs that both cabs were reproducing. A little multiple-source time / phase smear above 100 Hz that basically seemed to negate any low frequency coupling benefits one might suppose could be gained. I suspect that tradeoff is fine when even more SPL is desired, but here it was just superfluous.

 

I'll probably tinker a little more with the TRUE BIAMP (with low Xover freq) versus FULL RANGE WITH ADDED SUBWOOFER testing though. These were the clear winners at getting good tone and balance at the highest SPLs, and wring every bit of performance out of the cabs and rig. At moderate volumes the same was true.

 

With your cabs and rig results may vary. Or your testing environment may fool ya ; }

 

 

<-- greenboy ---<<<<     mo' bass - mo' quality - mo' ev'rythang!

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You've been a low crossover proponent since you were still blending yellow and blue.

 

sounds like fun, and sounds like you've got some highly useful equipment on your hands !!

 

Tom

www.stoneflyrocks.com

Acoustic Color

 

Be practical as well as generous in your ideals. Keep your eyes on the stars and keep your feet on the ground. - Theodore Roosevelt

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Well, it was a lot of words, Kikky. But it was guided by some sort of an educational process for mind and ear. I hope.

 

Sweet Willie and Tom, you might recall my mention of using an Acme B2W underneath a small cab, crossed over low enough to get full benefit of the small cab's tone and capability. This is basically the same concept.

 

Yesterday I did a bunch more driver/cab modeling in WinISD. I looked at lots of 15" drivers. The Eminence Magnum series 15LF (for Low Frequency) would go right into this very small cab - actually a little smaller than my Carvin 210, which is smaller than some 210s. And by cutting a couple inches off the port tubes to optimally retune the cab to it, would be an incredible light-footprint powerhouse.

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GB,

 

I remember fondly the idea you floated about the Acme B2W as a subwoofer for a small, but powerful, biamped rig. Maybe a quality 1x10 w/ tweeter on top of the vertical B2W? Hmmmmm -- lightweight, loud, full-range...

 

Keep the ideas coming (as well as the updates on your Barbetta-Carvin experiments!).

 

Peace.

spreadluv

 

Fanboy? Why, yes! Nordstrand Pickups and Guitars.

Messiaen knew how to parlay the funk.

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