Except for the name calling this has been an interesting thread. I've learned several things.
I realize that I'm not answering your question but I would like to take a step back and look at this from another angle.
1. Your Moabs are spec'd to 20 hz. I've never heard these speakers but they have great reviews and I've never heard anybody say they are shy in the bass.
2. You purchased two subwoofers which cost $350 each and weigh 40 lbs. to supplement the bass of a pair of full size, full range, highly regarded $4500 speakers that reportedly compete with speakers costing 10 times their price.
3. If the Moabs go anywhere near 20 hz you don't need subwoofers. If pipe organ is your favorite type of music and you are missing the 16hz notes then you could spend several thousand dollars on a sub that would not only go that deep but was equipped with a high quality crossover that included a very low cutoff point. Wilson makes a sub for $40,000 that accomplishes this purpose.
4. The subwoofers you bought are accentuating the frequencies that your Moabs are already putting out. They are doing nothing constructive.
5. If I understand correctly, the subs have no speaker input and no speaker output. In my experience cheap subs are usually designed so that you hook your speaker wires to the sub and the sub crossover sends the main speakers the high pass signal. That prevents the sub and the main speakers from doubling the bass frequencies. It looks like these subs are designed for folks who have small stand mounted speakers that have their own natural rolloff at 60 hz or higher. It's pretty obvious to me that they were never intended to integrate with a pair of full range speakers like the Moabs.
The lesson here is that your subwoofers are doing more harm than good. You are just adding low frequencies that your Moabs are already supplying. If they sound bass shy then it's likely that your room is the problem, not the speakers. It's probably not feasible to return the Sparkes but you should have devoted that money to room treatment instead of subs.
I can provide an example of a subwoofer/full range speaker setup that is working well. I have a pair of Thiel CS6 speakers that are rated to 28 hz on the low end. The bass is great but it is lacking in the lowest octave. I also have a 15" Velodyne subwoofer that incorporates a pretty steep crossover. It is adjustable down to 40 hz. I use the Velodyne with the crossover at its lowest setting. About 80% of the time the subwoofer just sits there looking impressive but not making any sound at all. But when I put on something that has low bass it gracefully adds the gut jiggling frequencies that the Thiels just can't reproduce. But this didn't just happen. I've spent a lot of hours on speakers placement to get there.
Sorry to be sarcastic, but if you think your Moabs need a pair of $350 subwoofers to sound good than you should seriously consider returning the Moabs, not the subs.
I realize that I'm not answering your question but I would like to take a step back and look at this from another angle.
1. Your Moabs are spec'd to 20 hz. I've never heard these speakers but they have great reviews and I've never heard anybody say they are shy in the bass.
2. You purchased two subwoofers which cost $350 each and weigh 40 lbs. to supplement the bass of a pair of full size, full range, highly regarded $4500 speakers that reportedly compete with speakers costing 10 times their price.
3. If the Moabs go anywhere near 20 hz you don't need subwoofers. If pipe organ is your favorite type of music and you are missing the 16hz notes then you could spend several thousand dollars on a sub that would not only go that deep but was equipped with a high quality crossover that included a very low cutoff point. Wilson makes a sub for $40,000 that accomplishes this purpose.
4. The subwoofers you bought are accentuating the frequencies that your Moabs are already putting out. They are doing nothing constructive.
5. If I understand correctly, the subs have no speaker input and no speaker output. In my experience cheap subs are usually designed so that you hook your speaker wires to the sub and the sub crossover sends the main speakers the high pass signal. That prevents the sub and the main speakers from doubling the bass frequencies. It looks like these subs are designed for folks who have small stand mounted speakers that have their own natural rolloff at 60 hz or higher. It's pretty obvious to me that they were never intended to integrate with a pair of full range speakers like the Moabs.
The lesson here is that your subwoofers are doing more harm than good. You are just adding low frequencies that your Moabs are already supplying. If they sound bass shy then it's likely that your room is the problem, not the speakers. It's probably not feasible to return the Sparkes but you should have devoted that money to room treatment instead of subs.
I can provide an example of a subwoofer/full range speaker setup that is working well. I have a pair of Thiel CS6 speakers that are rated to 28 hz on the low end. The bass is great but it is lacking in the lowest octave. I also have a 15" Velodyne subwoofer that incorporates a pretty steep crossover. It is adjustable down to 40 hz. I use the Velodyne with the crossover at its lowest setting. About 80% of the time the subwoofer just sits there looking impressive but not making any sound at all. But when I put on something that has low bass it gracefully adds the gut jiggling frequencies that the Thiels just can't reproduce. But this didn't just happen. I've spent a lot of hours on speakers placement to get there.
Sorry to be sarcastic, but if you think your Moabs need a pair of $350 subwoofers to sound good than you should seriously consider returning the Moabs, not the subs.