Amp Suggestions for FearFUL Cabs

[Bassman1775]

I'm currently playing on a pair of 12/6/1 FearFUL Cabs powered by a Mesa Boogie WD800. They sound incredible but about a year ago I had some traffic on an old thread where I posted concerns about my Mesa being cranked to about 2/3 Input and Master. Anything more and the amp flashes O/D and Limit lights. We play outdoors most of the time for crowds of 200-400. Our PA has a 12" sub so most of my bass is heard via my cabs. I feel like I need more out of my rig with increased headroom and a more full bottom end.

I'm contemplating building new cabs and converting them over to 15/6/1. I've heard the 15s handle power more efficiently (more volume) than the 12s and are deeper. My first thought is try the 15/6/1s with the WD800. If that's not enough of an improvement then I'd opt to use the WD800 as a pre-amp and maybe a higher powered power amp like the Crest Pro-LITE 3.0.

I'd appreciate any thoughts or suggestions. What do other players drive their 15/6 FearFULs with? Should have probably gone with 15s from the get-go but not too many FearFULs out there to try out.

 

[Lonnybass]

I'm currently playing on a pair of 12/6/1 FearFUL Cabs powered by a Mesa Boogie WD800. They sound incredible but about a year ago I had some traffic on an old thread where I posted concerns about my Mesa being cranked to about 2/3 Input and Master. Anything more and the amp flashes O/D and Limit lights. We play outdoors most of the time for crowds of 200-400. Our PA has a 12" sub so most of my bass is heard via my cabs. I feel like I need more out of my rig with increased headroom and a more full bottom end.

I'm contemplating building new cabs and converting them over to 15/6/1. I've heard the 15s handle power more efficiently (more volume) than the 12s and are deeper. My first thought is try the 15/6/1s with the WD800. If that's not enough of an improvement then I'd opt to use the WD800 as a pre-amp and maybe a higher powered power amp like the Crest Pro-LITE 3.0.

I'd appreciate any thoughts or suggestions. What do other players drive their 15/6 FearFULs with? Should have probably gone with 15s from the get-go but not too many FearFULs out there to try out.

I have a pair of Fearful 15/6/1s that I matched with a Crest ProLite 3.0 DSP. I was looking at other options for amps, but nothing else in the class D realm matched the power/efficiency of the Crest 3 when it came to driving two cabinets (500w per channel at the Fearful's 8 ohm).

 

[agedhorse]

In general, 400 watts RMS per driver is the point (with most 12" and 15" drivers in use today) of diminishing returns. Where this isn't bringing the desired results, it suggests that there is simply not enough rig for the gig.

With 12" cabinets (no matter what the driver), the trade-off between sensitivity and power handling becomes a very real challenge when high SPL is needed. As power handling increases, there is more of the voice coil residing outside the magnetic gap of the motor which reduces sensitivity. Without the wire outside the gap, as the VC moves and the end of the wire enters the gap the distortion increases almost exponentially as the force on the VC decreases. There are alternatives, but they are very costly to implement and they also directly (and negatively) impact the high frequency response of the driver. I do not know what the real world sensitivity of the Fearful cabinets are, that would be helpful for this discussion (or at least the specific 12" drivers used, from which the calculations can derive the real world half-space sensitivity)

There are 2 practical alternatives, either increase the number of drivers (which keeps the force constant per unit area acoustic load on the cone), or increase the area of the cone (and the strength of the motor).

Going to a 15" driver allows for some reasonable compromises with regards to higher sensitivity provided the motor is capable of supporting the acoustic load. Even so, the point of diminishing returns is in the 400 watt range with most of the commonly available "premium" drivers that I have tested (regardless of their published and sometimes absurdly inaccurate ratings).

I would recommend trying a couple of "premium" 15" cabinets with sensitivity in the high 90's, this will give you a better idea of what the rig is capable of.

 

[Passinwind]

I do not know what the real world sensitivity of the Fearful cabinets are, that would be helpful for this discussion (or at least the specific 12" drivers used, from which the calculations can derive the real world half-space sensitivity)

Stock off the shelf 8 ohm Eminence Kappalite 3012LF. There's a 2nd order low pass in the crossover as well, at around 800Hz.

 

[agedhorse]

So my suggestion that a 400 watt point of diminishing return holds true. There will also be an insertion loss from the low pass filter of approximately .5dB and a real world sensitivity loss of about 1dB due to how the average sensitivity of that driver is calculated. Add to this the fact that power compression begins to rise around 300 watts RMS and the point of diminishing returns is well within the 400 watts RMS that I suggested earlier.

This would place the sensitivity at somewhere around 94dB/1w/1M which may be responsible for what the OP is experiencing. Increasing the power won't really help, because above 400 watts, assuming the additional distortion is acceptable, for every dB of power that is added, less than 1/2dB of additional SPL is generated. This is the challenge that every speaker designer (I'm no exception here) faces.

The KappaLite 15LF on the other hand is ~98dB/1W/1M sensitivity and handles a little more mechanical power (right around 400 watts under typical applications) so this alone is comparable to more than DOUBLING the effective input power. It's a SIGNIFICANT improvement and a much better approach for getting more rig for the gig without increasing amplifier power.

It's also why the math is so important, there's a lot of detail there that helps understand the limitations and how to achieve real world improvement.