Wow, ya got me flummoxed. So many questions. Let's start with:
- What is BP-4 alignment?
- What is .6 Qtc?
- Are you measuring THD with REW?
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Review and Measurements of Crown XLS 1502 Amp
- Thread starter amirm
- Start date
- What is BP-4 alignment?
- What is .6 Qtc?
- Are you measuring THD with REW?
Flummoxed here too!
tvrgeek
Major Contributor
These are parameters related to a speaker design. BP-4 means band-pass four alignment. The driver is in a sealed box but instead of directly radiating out, there is a secondary ported enclosure. If the driver is suitable, and if port lengths are not unmanageable, it has an advantage of both lower extension and of acoustic filtering above the pass band further reducing harmonic distortion. However, I do not believe at this time, it can have optimal transient response which I consider more significantly audible than pushing the HD below 1 or 2%. JBL and Bose have produced them commercially, but they are not common.
Qtc is the speaker system Q. .7 being maximally flat response, .5 being "critical damped" so optimal transient response. Higher than .7 will have a peak before roll-off and have less "impact". Think "boom box" of old. Hard to describe transient response without subjective terms, but one can measure it quite easily. You hear the difference in percussion if it is not masked.
I am using True RTA/24, brute force of stepping the fundamental and recording the harmonics, then doing the calculations for first 5 ignoring any data below -50 dB from the fundamental.
Qtc is the speaker system Q. .7 being maximally flat response, .5 being "critical damped" so optimal transient response. Higher than .7 will have a peak before roll-off and have less "impact". Think "boom box" of old. Hard to describe transient response without subjective terms, but one can measure it quite easily. You hear the difference in percussion if it is not masked.
I am using True RTA/24, brute force of stepping the fundamental and recording the harmonics, then doing the calculations for first 5 ignoring any data below -50 dB from the fundamental.
Maybe the Klipsch forum? I'd be curious as well. I see they list '100w continuous/400 peak' but also fairly efficient. I.e. compressed music -pop/rock for example, hovering in that 100w zone I would expect be quite loud.
https://community.klipsch.com/index.php?/forum/29-2-channel-home-audio/
In reference to the -20 & -10 db's: As I understand it (I have been wrong before: for proof just ask my wife) Pro Amps are theoretically calibrated so that 0 db is full power at the rated distortion. So these lights are theoretically letting you know that you are getting closer to full power at the amps rated distortion. In my experience, is extremely rare (if ever) that excessive power caused a blown speaker. Excessive distortion is the usual cause (which is most likely to happen with an amp that does not have enough power). Since the speakers that you intend to use are usually known for their efficiency, it is highly likely that your ears and your neighbors will be complaining before you ever drive the amp into enough distortion to kill the Klipsch speakers.
Volume control (attenuators here) does not operate like this. It reduces the input signal to the amplifier. If the output level is low (> 2 volts) it is set higher or wide open say. If the source has high output voltage the attenuators can reduce the input signal level.
This is why the volume setting is not comparable to power output. That is determined by input signal and load seen by the amplifier.
Do not be concerned about using a 400 watt amplifier with a 100 watt rated speaker. Your ears will tell you when you are overdriving the speakers. The Klipsch efficiency ratings seem to be around 5 - 6 dB optimistic. At least when measured with the industry accepted standards. But most are still efficient speakers. Playing compressed music and averaging 100 watts power should chase you from the room.
The high power rating is good if you really do play loud. Amplifier clipping will blow speakers quick.
Also music that is clipping. I have an old (25 years) Sarah Mclachlan CD that must be recorded in the red and distorted. Blew an output tube once playing loud and another time had a speaker crossover fail. Quit playing the CD after the second hard failure.
Can anyone attest to audible/noise floor improvements by using XLR / Crown > RCA / Preamp connection? Currently I'm using RCA / Crown > RCA / Preamp, but I wonder if upgrading to XLR matters if the preamp does not support XLR requiring RCA termination? Does a balanced connection remain "balanced" if its inserted into the preamp using an unbalanced connection (RCA) ? ???
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Quick questions:
XLS1502 has XLR inputs. Is the amp a truly balanced design? or XLR inputs are just for convenience
Also, what setting should volume knobs be set at (and forget) for best performance? Volume is controlled by a preamp feeding XLRs on Crown
XLS1502 has XLR inputs. Is the amp a truly balanced design? or XLR inputs are just for convenience
Also, what setting should volume knobs be set at (and forget) for best performance? Volume is controlled by a preamp feeding XLRs on Crown
The XLS 1502 has balanced input > conversion to unbalanced for volume control > conversion to balanced for following stages to output. The setting of the level control depends on your individual situation. If you have lots of gain in a preamp, you might run them at a low setting.
The Crown definitely has an audible reduction in noise with the XLR inputs IF you have a noise problem. I do and the difference is night and day. Unbalanced has lots of noise from nearby computers etc, but balanced is dead quiet. If you don't have a balanced preamp/dac then there is likely no improvement to be found using xlr conversion cables from RCA.
Thanks, my preamp is Schiit Mjolnir and i couldn't find if it has high gain. Assuming it has normal gain, is 2'o clock the recommended volume knobs position on the Crown. I see some folks have theirs at 2'o clock, I dont know if that position means 29db gain
The gain of the Crown stays pretty much the same regardless of the attenuator setting. You are mainly attenuating the input signal, so any setting you like on the Crown should be ok. I'm using a MOTU M4, which has a digital volume control. I set the Crown as low as possible for the volume I listen at so the digital volume reduction is minimal. If I have a preamp with analog volume control, I set the Crown high, if there isn't any noise.
Good advice. Mine are fed by a Chromecast so I set the amp "gain" at the loudest setting I would ever want to listen to - so I don't blow out my ears by mistake. Then I control the volume using my app (think of it as a preamp).
Thanks. I was reading xls2502 review Amir did and there is this line in there ‘I set the gain to 29 dB for consistency’
If the gain is not affected by the knobs, i wonder what to do to adjust it to 29db.
i was chasing this number 29db but may be i should not
Here is direct from Crown (@JeffGB is 100% correct).
Should I have the level controls on my amplifier turned all the way up?
It depends on the system and how much gain you have prior to the amplifier. The level control can be thought of as an input attenuator. It does not limit the power available from the amplifier. With the level controls turned down the amplifier can still reach full rated output power, it just takes more drive level from your mixer to achieve it. Generally, you should set the mixer's individual channel fader and master gain to 0 dB, then adjust the amplifier level controls to the desired sound level.
The newer Crown XLS models have a switch for two gain settings on the back. Many people were trying to drive the Crown's with the pre-out of AV receivers and found the gain too low so Crown added the additional setting with higher gain. The lowest noise and distortion is at the low gain setting.
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My XLS 1502 has a high gain setting, but it is accessed through the menus on the front of the unit.
Interesting. I have an XLS 1500 which is the same with cosmetic changes and no gain switch. I also have a Crown XLI800 with the new styling and it has a switch on the back panel. I wonder how they implemented the gain into the DSP settings?
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