Great info, Art! I really enjoy reading these types of findings.
The SpeakerPower SP4000 option is fantastic. Maybe not ideal for my situation, but I was just looking for a high power plate amp w/XLR in for another project. Speakon out is a definite plus.
Have you any experience with the Crown I-T8000? There's a sound engineer a couple hundred miles from me who switched to those from his PLX's. He runs (4) TH-118 off of one I-T8000 and reports much more LF content without the notes dying off quickly like his previous amps.
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"It only works on certain types of amps and is tied to how the power supply is handled.* Amps with a sperate power supply for each channel will not generate any more power.
Yes it inverts the B channel with respect to the A channel.* And ties the B channel input to the A channel input.* This only works if you are sending the same signal to both outputs-which is not the case in stereo.
So you would need 2 amplifiers with 4 loudspeakers hookedup to do this in stereo."
-Ivan Beaver
Yes it inverts the B channel with respect to the A channel.* And ties the B channel input to the A channel input.* This only works if you are sending the same signal to both outputs-which is not the case in stereo.
So you would need 2 amplifiers with 4 loudspeakers hookedup to do this in stereo."
-Ivan Beaver
Not when the amp is actually built with an inverted channel, IPR series 1600's and 3000's for example.
"It works and some amps are built like this from the factory now. "
It makes a fraction of a dB difference and can have a downside of dynamic woofer off-set going in opposite directions in a stereo amplifier.
It has been tried in the past in many commercial designs, and then abandoned.
It is touted as being a fix for power supply pumping in half-bridge class D designs, but that remains to be seen.
It makes a fraction of a dB difference and can have a downside of dynamic woofer off-set going in opposite directions in a stereo amplifier.
It has been tried in the past in many commercial designs, and then abandoned.
It is touted as being a fix for power supply pumping in half-bridge class D designs, but that remains to be seen.
I have no direct experience with the Crown I-T8000, but am not a fan of extreme current limiting, the amp puts out 4000 watts per channel at 4 ohms (good for single high powered 4 ohm speaker or two lower powered 8 ohm speakers) but only 3500 watts at two ohms, not enough power to get the most out of a pair of four ohm DSL TH-118 per side.
One of the excellent features of the SP4000 is it's low frequency performance at really low impedances. I have used it with four Lab 12 in parallel, at Fb that is only a 1 or 1.5 ohm load, and the amp still kicked hard, though it would be possible to kick it's breaker if leaned on too hard for too long.
That said, on paper the I-T8000 would have 3 dB more output in to a four ohm load than the SP4000, whether it would actually make a particular sub sound louder is a question only answered by an A/B test, my investigation of just four amps revealed large differences that don't correspond to specifications.
Of note, the old school heavy metal Crown PSA 2 (weighs 8 times what the SP-4000 weighs), rated for only 460 watts at 4 ohms, and 700 at 2 ohms, put out 1 dB more output in to a BC18SW115-4 than the Crest CC 2800, rated at 965 watts at 4 ohms, and 1400 at 2 ohms, almost exactly double the paper rating of the PSA-2.
Not that it means all the difference in the world, but just to clarify - I believe he's using the 8 ohm versions. So, 4 ohm load/4000W per channel, 2000W per TH-118.
The prices for these amps have reduced a little bit due to new versions coming out. I saw the amp as a more powerful (yet lightweight) upgrade from what I'm currently running (DSP being a bonus). I have found some used Crest CA-9 and CA-12 amps for enticing prices - I just don't know how I'd enjoy quadrupling my rack weight
The I-T8000 seemed a decent compromise. I'm loving the knowledge I'm reading from you all, so I'm not asking for that to stop Before I click "Start Measuring" I clicked "Check Levels" to be sure everything was still even - yet, it popped up with "Level is Low" before audio was heard through the sub
So, the measurement process stops, but the 2 sweeps continue to play.
I get this dialog box (attached) before any audio is played
When I enter the SPL Meter for calibration, it supplies a filtered pink noise signal, not sine wave choice. When I enter the Signal Generator, it doesn't show an incoming signal, just outgoing and "RMS Level dB FS" adjustment. Where do I need to be and what do I need to do to get this done properly?
Attachments
Sounds like REW most likely just needs to be restarted...
Check the settings for the correct device and R/L channel selection = same as calibration.
Did you plugin a USB sound card after starting REW? = restart REW
Are the only things connected to the (USB?) sound card the line out to the amp and the mic cable = no other loop
Check the settings for the correct device and R/L channel selection = same as calibration.
Did you plugin a USB sound card after starting REW? = restart REW
Are the only things connected to the (USB?) sound card the line out to the amp and the mic cable = no other loop
Yes.
Before the measurement attempt, I went into Preferences > Levels > Check Levels. I then set the L & R levels with the gain on the sound card to get it to ~18dB FS, like suggested in the dialog box. Maybe I'm doing something wrong here.
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