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About difflvl

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  1. David thank you very much.
  2. Right I will not be feeding the sub amp 20hz-20khz, BUT if the amp can provide for example 1000 watts into a 4ohm load per the ftc method, than my subs should see at least that number. I agree, but regardless of its intended use, in my opinion the FTC method is a very good way to test any amp be it home or pro. The reality is that even many "pro amps" on the market will not drive a 2 ohm load @ full tilt for hours, especially amps that don't have a 2 ohm FTC rating. It depends on what you are playing through it but like I said if you are playing some real vigorous bass through the subs, the amp will most likely thermal. In the case of the XTI4000, it uses 4 MJ21193/MJ21194 transistors which can do up to 250 watts a piece @ 25C. So if we add that up, we can only handle max 1000 watts/channel @ 25C regardless of impedance, regardless of what you do, you cannot sustain any more than that for long periods of time. Now realistically the more you push it the hotter the transistors will run and they lose about 1.4watts/1C so if you are running at 45C then you essentially lose 28 watts per transistor for a total loss of over 100 watts, so now you are left with only 900 watts.
  3. I strongly suggest you stop and take a breather. First. Lets look at the FTC ratings. It is measured from 20 - 20,000 KHz. Unless you are using a full range cabinet the FTC ratings doesn't hold any weight for frequencies ranging from 30 - 150 Hertz. Reasons being you are delivering a limited frequency bandwidth, which the FTC ratings (20 - 20 KHz) cannot answer. So, you are back at square one. David Glass answered your question right here; QUOTE The 10 to 20% difference between FTC and EIA is not that much to begin with. To hear a difference in output level the output power would need to be doubled (raised by 3db). You can hear the difference between 200 watts and 400 watts, a 3 dB increase or doubling of power, but you won't hear a difference between 200 watts and 240 watts as small difference in output power are not discernable to the human ear. FTC ratings were also aimed towards home audio and, Crown is not obligated to use them because they left the home audio market 30+ years ago. What matters is performance. And Crown has always been notorious for their low-end performance for decades. Now if you still want to know the answer, you'll need to deduct the 1 KHz wattage at the given impedance by 10-20% to achieve the FTC rating of 20 - 20,000 KHz. Then, deduct the FTC frequency response to your sub frequencies (Wherever your starting and cutoff point is) at the given impedance to find the answer. Other than gloating on having a few insignificant watts over your competitor you are not gaining anything. Best Regards, If the 20hz-20khz rating is for example 1000 watts, that tells me that i will get minimum 1000watts anywhere in that range, so how do you figure it wont tell me how much my subs are getting? You cannot accurately calculate the FTC rating by using a %. I have seen amps where its 10% and amps where its a 30% difference. That percentage can also be 10% at one frequency but 30% at another frequency, so that isn't a good way to find out, its good for a guess. With the EIA method you only need to drive 1 channel (i know crown does both channels) at 1khz, thats it. With the FTC method you need to drive both channels at 20hz-20khz. Needless to say its a lot more stringent and more accurate representation of an amps true power. Play a 1khz test tone and a 20hz test tone through the same amp, see which tone draws more power. The FTC method imo is the only good method to measure wattage as it test the whole frequency range, with both and really tests the power supply a lot more than the EIA method. In the case of home theater amps, some (cheap ones who don't provide the FTC rating) wont even complete the FTC test they will just shut down because thats how stringent the FTC method is. The FTC method also requires about a hour of testing at each individual impedance (2ohm, 4ohm, 8ohm). Same thing with these pro amps as well thats why you will rarely see the FTC for 2 ohm because most likely the amp cannot and will not handle the FTC test at 2 ohm impedance, thats why most amps that give you the FTC rating only give it to you for 8 and 4 ohms. All the great amps out there I-Tech included have the FTC rating. I don't care what the MAX output of an amp is, I want to know what the sustained power is under stress and the EIA rating hardly stresses the amp. Maybe the EIA is fine if you are using the amp & speakers for voice or something weak like that but if you are actually pumping music with hard beats and bass through it, its a different story. So now you tell me which rating is going to accurately tell me how much punch my amps will deliver when both channels have been on at almost full blast hours on end?
  4. Easy there Ray. I have requested the 20-20 Khz numbers for you from our engineering department. When they are able to get to the request they will get me the info and I will get it to you. See what type of company we are. Thank you
  5. If crown is refusing to give me ratings for a product that I bought from them and giving me a run around, then that is the last time I buy a crown amp. I'll be sure to let everyone know about this BS runaround you guys are giving me and how you guys do not want to give out the real power of the amp that you guys sell, just the "useless" 1khz figure. I have been a crown loyal until now, this really *beep*es me off. 1khz is BS marketing gimicks that companies that make weak amps use to up their wattage. Its very similar to gas mileage on a car, everyone knows the EPA ratings are with a granny driving and not normal driving. Same thing here, they use this BS 1khz to be able to publish higher wattage numbers. Who cares what the wattage is in at a single point out of the whole frequency spectrum. Thanks for showing me what kind of company you guys really are!
  6. Thanks David, I understand you guys test both channels simultaneously and other people test only one. I know you guarantee your rated wattage but my question is what are the FTC numbers available for the XTI 4000? I want to know how much power the XTI 4000 is sending to my subs (30-150hz range) hence the reason I ask for the 20hz-20khz. I bought 3 of these amps and would like to know what its putting out. I don't mean any disrespect here but it seems you posted the ratings for the ITech because they are virtually the same as the EIA ratings. I find it hard to believe the engineers at crown have not tested the XTI 4000 wattage across the full frequency range. I don't think its too much to ask for as an owner of this amp to get the 20hz-20khz power rating. If you want me to keep quiet about it I will just PM me. My suspicion is the FTC rating must be a lot lower and that is the reason you guys don't want to publish it. difflvl
  7. What was the other gear if you don't mind sharing?
  8. As strange as this may sound, the XTI4000 hooked up a standard bookshelf blasting all the way doesn't make very much noise. It felt like the amp had 5 watts. Same speaker hooked up to a home receiver makes a lot more sound. But when hooked up to a JBL MRX its very loud. Its was very strange. I don't think its so much sensitivity as the home receiver with 100 watts makes 2-3 more sound than the XTI did. Don't believe me? try it for yourself.
  9. The EIA rating IMO is useless. It doesn't tell me how much power my sub will get or anything else for that matter. Are you guys not sharing the XTI4000 FTC figure because it is low? I know you have the figures so please share them.
  10. Thanks for the explanation. Just out of curiosity what is the watt output of the XTI 4000 with the FTC method? Thanks
  11. I was wondering what are the wattage specs for the XTI 4000 at 20hz-20khz, instead of the 1khz rating. I looked all over the website and can't find it. Thanks
  12. Ya you can use the XTI 4000 for the MRX515s.
  13. I have had 3 different XTI4000 do this already. Sometimes the volume/attenuator knobs stop working. Also sometimes the volume will change by itself. All amps are less than 2 months old, could it be the attenuator pots?? Thanks
  14. I would assume when bridging into a 4ohm load, each channel is running 2ohms. Running in 2ohms is pretty tough on the amp, and doesn't sound that great. Its "okay" for a sub, but probably not for the mains. I could be wrong though, but having heard the difference between XTI1000 bridge, and XTI4000 no bridge, the XTI4000 with no bridge sounded a lot better.
  15. Hi, I need the I-Tech 8000 schematic. There seems to be a problem with highs on one channel. Thanks