lukeamdman

I'll post raw responses (no eq or xo) from every amp I have driving the sealed 21s. I'll also test the XLS, among other amps, for max power at 25hz, 20hz, 15hz, 10hz, and 5hz.

The only way to know how the inuke6k or ipr2-7500 would perform compared to the 7.5 would be for me to run the same test under identical conditions. If I could measure the amperage draw at these maximum output levels we'd have a much better idea of the actual power output. I know the starting resistance, but as power and excursion increases that resistance is going to change. Additionally, an amp most certainly could provide more power in 4ohm stereo vs. 2ohm stereo because lower impedance loads require more amperage from the power supply. For example: 2,000w per channel in 4ohm stereo = 89.4v and 22.3A per channel 2,000w per channel in 2ohn stereo = 63.2v and 31.6A per channel If the power supply can only provide a total of 45A, it'll hit 2kw per channel at 4ohm but will only provide 1kw per channel at 2ohm stereo.

Any evidence/data to support this? It seems you're suggesting the alignment of the sealed subs has a direct effect on the resonating surfaces in the room (in this case the floor), and additionally that it's also not related to SPL? Like everyone else I've sold subs that I've built, but I've also been shocked to find that my own sub was completely unrecognizable in a friends HT room which is on the 2nd floor of his house. Not only was he using less than half the power I was, his room was 3-4x larger and basically open to every other room on his main floor. He didn't even have two full walls on his HT. The difference in tactile feel <20hz was planets apart. My approach is always to try it and just find out, hence me selling my beloved tapped horns to try sealed again. I'd really like to see the difference of a vibsensor at 10hz and lower between Bosso and Brandon's systems. Brandon's system, while epic in every respect, in my experience didn't have the same dizzying floor rumble that Bosso's room has below 10hz. After all, why would anyone expect a concrete slab to resonate like a suspended wooden floor?!?

Agree 100%. By far the most puzzling situation for me was a guy on AVS who lives about 20 min from me in Minneapolis. He has a PSA Triax and wanted me to come over and measure his subs because he felt the low end was non-existent. It turns out, his response was crazy flat to 12-13hz, but below 25hz there was nothing felt nor heard. His room was really small too, probably only ~12x15. No vibration of the floor, walls, couch...nothing below 25hz. Really bizarre.

I can personally attest that Bosso's floor is a trampoline <15hz. Not only is his entire theater on a suspended floor, the rear seating is also on a riser. When the dual HST-15s were shaking the floor with more tactile sensation than my dual Ghorns pumping out 134db at 15hz, I was seriously jealous and angry at the same time!

Its price tag alone make it a driver that few will ever purchase, but it has a few specifications that really stand out for some specific, and I'll admit rare, use cases. The tremendous BL has the horn guys salivating as the possibilities, and its thermal handling capabilities look to surpass just about everything else out there as well.

Something funky happened to the SPL numbers for this driver in the systems list. They're all blank.

I'm also modifying my spreadsheet to make the results easier to read. Currently it's a little too busy, and I'm removing the SPL numbers since that requires more work and additional strain on the amps/subs since I have to run another max power/output test but this time watch for SPL in the room.

I'm waiting on the FTW-21 drivers to continue testing. If Mark is still on schedule, they should ship out next week.

Compression sweeps are jaw dropping...

This system sounds awesome. The 4520 brought it to a whole new level and it was kind of shocking. I'm impressed with the THT and it's amazing what it can do with only 300w!

Are you selling all that stuff you just listed?

I recently picked up a Crown XLS 2500 that I'll add the list of amps to be tested.

I'd need better/faster equipment to measure that. It takes the Fluke 117 about a second to read the RMS voltage, so a 5-7 cycle burst would happen too fast for it give a reading. I just noticed the peak voltage thing in the GUI, and yes, I'm measuring RMS voltage. So far I've only been able to barely squeeze out 50v RMS with one channel driven at 5.5ohm, and that only lasts about a second.

Here are screenshots of the GUI: The limiter settings are still at the defaults:

I don't think so, but I'll double check. With one channel driven the volume on my preamp will get to about -9. With two channel driven, only -12db.

I’ll post some screen shots of the GUI/configuration. It’s very possible that I could be missing something that’s causing this.

Whatever is doing this limiting, it isn't consistent with either voltage limiting or amperage supply since regardless of the resistance you get the same wattage per channel. It doesn't matter if it's running 2ohm stereo or 5.5ohm stereo, you'll only get ~210w a channel if you want more than a second or two of output. At dual 2ohm, it'll supply 10A (or ~20v) per channel just fine. At 5.5ohm, you only get 6A (or ~34v) a channel. Through all this, the amp never even gets slightly warm, the fans never turn on, and the limiter lights are never on (you can limit based on either voltage, watts, or dBu). I only guessed it was bus pumping based on what I've read about it recently. Whenever this behavior manifests itself, it plays multiple frequencies at once and it's "pulsing" rapidly. The other two class D amps I've tested so far haven't behaved anything like this when pushed to and over the limit.

LG says the amp isn't bridgeable: If it really is a "dual mono" design, than what I'm experiencing isn't bus pumping?

Interesting! I really like the SQ (meaning it's no different than any other decent amp I've heard) and the EQ is great. However, the power output I'm getting from it isn't making any sense to me. With the 2ohm tests, I was able to get ~10A per channel without bus pumping. Increasing the levels to ~10.5A a channel, I'd get bus pumping after ~2 seconds into the tone. That lines up with the 20A figure mentioned in the review you just posted. If the power supply is capable of 20A, why are my 5.5ohm tests limited to about 6A per channel? Shouldn't I be getting about ~550w per channel instead of ~210w? In my tests, regardless of the resistance, I was limited to ~210w per channel without bus pumping. What am I missing? Could this be a software/firmware issue?

I just re-ran the IDP 2400 test at 80hz and 5.5ohm, but this time on the same 240v 30A circuit I did the SP2-12000 tests on. The results were EXACTLY the same for both one channel driven and two.

Maybe running it with 240v mains would help?

I checked again and the limiter is set to the maximum voltage, which is 98v for each channel. I also have the channels "linked", so whatever settings I change on one channel are mirrored to the other (things like input gain, EQ, XO, phase, limiter voltage). Even if it were the voltage limiter doing this, it still wouldn't explain how I get more voltage with one channel driven vs. two channels driven, right?

I've been pestering Mark for a few months about a packaged deal for the FTW drivers, and he made sure I was at the top of the list for the group buy. I'd feel like a jerk to back out after all that.

What's next? Spill the beans!