Clipping led flashes on my proamps

[TLS Guy]

I am determined to get to the bottom of this clipping issue. I checked the impedance of my pl 89's and my pl 28 and all three are reading 3ohms instead of the rated 8ohms The ma 2050 and xls1500 claim 500wpc(probably more like 400) @ 4ohms but the acoustechs have a rms of 250w. Can this be the cause of the amp red clipping LED flashing?

You can't measure the impedance like you did. You need a woofer tester from Parts express, and the you can post the impedance curves. The woofer tester measures phase angles also. This latter is often more significant than impedance.

The next issue is that if it is the clip on the power amp flashing it is not a gain issue. That will only flash if the power stage of the amp in not meeting the power demands required.

Often amp ratings are severely embellished.

Peak power is nonsense, despite what nonsense Bob Carver put about. There are plenty of musical passages that demand continuous high power.

The real issue is how much continuous power your amps really deliver. The manufacturers don't want you to know on these budget prices amps.

Look up the continuous RMS power rating of your amps and post here if you can find them.

 

[Eyecantcode]

You can't measure the impedance like you did. You need a woofer tester from Parts express, and the you can post the impedance curves. The woofer tester measures phase angles also. This latter is often more significant than impedance

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Well thanks a lot TLS for making me look like a total idiot
I've checked the crown and marathon websites for the rms rating and each claim 300wpc @ 8ohms. Both the crown and the marathon clip in the same fashion. It's funny, I was told that I didn't need an amp because the 1121 would be more than enough, yet here I am clipping too different amp.

 

[Rickster71]

This is something you have to go step by step and systematically to find.
It could be something as innocuous as a speaker wire whisker.

 

[TLS Guy]

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Well thanks a lot TLS for making me look like a total idiot
I've checked the crown and marathon websites for the rms rating and each claim 300wpc @ 8ohms. Both the crown and the marathon clip in the same fashion. It's funny, I was told that I didn't need an amp because the 1121 would be more than enough, yet here I am clipping too different amp.

Check all the obvious first.

However my money is that this problem is the speaker design.

This will be a leaning experience for you.

As you measured a DC resistance of 3 ohms, the overwhelming probability is that the speakers are four ohm or less.

Now we have no got to talk about phase angles. To get the impedance the amp actually sees, you need to take areas on the phase curve that show negative angles and multiply the impedance at that frequency by the cosine of the phase angle. You would be shocked at what results can come up.

The next issue is if you measure an impedance below the DC resistance you measured, than the speakers are total junk and nothing will drive them. This is an absolute rule no exceptions.

The next issue is sensitivity, which is not what it seems.

There are two ways to spec, it. I volt 1 meter and 2.83 volts one meter.

At 8 ohms the numbers are the same. However if you spec at 2.83 volts, then a four ohm speaker sucks twice the amp power of the 8 ohm one, and yet the spec. will be the same.

So get you Dayton woofer tester from Parts express ASAP. It is very easy to measure the impedance curves and phase angles here. Then we will all learn a lot.

By the way I can not drive my friends B & W 800 Ds, to concert level in his room without clipping his 400 watts RMS per channel Mac amp into clipping.

Only very good amp and speakers can really be driven cleanly at true concert level dynamic range.

 

[Eyecantcode]

Ok, for those who are interested, what I found was I had the gain turned too high; I was thinking they were volume knobs and was absolutely wrong. I had the gain controls on both channels set to -6, I adjusted them to -12 and the clipping went away. The only thing that changed was how much volume I'd give from the 1121 before it got really loud. before, It would get to a certain output level and then clip now I can get to that same output level and it never clips.

Now on to another question I have. I noticed that the signal LED would only react to sounds like a really sharp snaredrum beat played from the tweeter, but would not react to lower frequency sounds played from the 8" drivers. Anyone care to share why this is?

 

[Eyecantcode]

If you are giving me the buisness then it is well desirved. The ep4000 would'nt help me in this situation. Now for my diy sub build, well thats a totally different beast. EP4000 maybe in my sights.