Switched Amps. Where Could The Difference Be Coming From?

[Sir Sanders Zingmore]

You mean from the terminals?

Yes. Speaker cables connected out of phase

But the DSP would take care of phase

Only he remeasured. The first post implies he didn’t.

so I am also wondering if the new amp could have something out of phase that needs correction from the DSP. Is this a possibility?

Seems unlikely. Connecting speakers out of phase is an easy mistake to make and far more likely.

 

[Deleted member 48726]

There is no corretion from the AVR. All I have done in the AVR is time align the subwoofer to the mains with REW alignment tool and added the distance. The correction is from Audiolense which is essentially a software DSP, how much it boosts I have no idea but it has plenty of taps with a maxium of 14 db correction in the correction filter. But I can tell you from the measurment graph that there is two frequencies with around 10-14 db correction.

I can only go on from Amir's measurements with the later models of the Marantz AVR and it seems it is nearing 3 volts when I get close to clipping and with the NC502 I was nearing 4 volts. Assuming that my older model produces similar voltages...

This I don't know and probably couldn't tell you, unless I find some calculations done in another thread on the Hypex amps. Or I learn how to use a voltmeter which isnt going to happen soon unfortunately...

No, the mains play full range but there sealed with an Fs of 55hz. The subs overlap up to 100hz.

Output voltage and input sensitivity looks like an okay match if not overdriven like mad.

But your info on EQ is concerning. -Which frequencies are boosted 10-14 dB?

Input sensitivity on an NC502MP-->
LINK

 

[antcollinet]

Even mounted on a 100mm heatshink,etc or active cooled the rating is at 1Khz.

Isn't that how we normally measure rated power? And the current limited note - that just means with a 2ohm load it runs out of current before volts - that is hardly unusual - Id suggest it applies to almost all amps - if they can't double power from 4 to 2 ohm, then they are current limited.

And the measurements here of the Ncore amps show the noise/distortion by frequency, also showing the point at which clipping starts. (Chart from the NC252)

I find it far more likely that the speakers are distorting than the amp is.

 

[Sokel]

Isn't that how we normally measure rated power? And the current limited note - that just means with a 2ohm load it runs out of current before volts - that is hardly unusual - Id suggest it applies to almost all amps - if they can't double power from 4 to 2 ohm, then they are current limited.

And the measurements here of the Ncore amps show the noise/distortion by frequency, also showing the point at which clipping starts. (Chart from the NC252)

I find it far more likely that the speakers are distorting than the amp is.

The point is that his NC252 MP shuts down with every bang down low,is not just distorting.
That not clipping as he described,that's the amp going in some condition.Thermals,current,voltage,short,something.
Or some kind of aggressive EQ is applied that drains it.

For that speakers does not seem normal,even if the power low is limited (Amir measures 122 watt at 4ohm at 20Hz and then goes to protection) .
I would double check the speakers condition.

 

[Deleted member 48726]

The point is that his NC252 MP shuts down with every bang down low,is not just distorting.
That not clipping as he described,that's the amp going in some condition.Thermals,current,voltage,short,something.
Or some kind of aggressive EQ is applied that drains it.

For that speakers does not seem normal,even if the power low is limited (Amir measures 122 watt at 4ohm at 20Hz and then goes to protection) .
I would double check the speakers condition.

OP stated that there is 10-14 dB correction boost a couple of places as well..

 

[Sokel]

OP stated that there is 10-14 dB correction boost a couple of places as well..

Oh,I missed that.
14db would need 10 times the amps power on top of what he already needs.
Makes sense now.

 

[Deleted member 48726]

Oh,I missed that.
14db would need 10 times the amps power on top of what he already needs.
Makes sense now.

Yeah. He hasn't returned my request as to where those corrections are done. But I suspect that it's in the bass area(s) because of the magnitude as it can only be room modes that dips so much.

 

[Sokel]

Yeah. He hasn't returned my request as to where those corrections are done. But I suspect that it's in the bass area(s) because of the magnitude as it can only be room modes that dips so much.

A 5" voice coil 10" Morel or some pro similar voice coil driver down low instead of the Scanspeak and one of the big boy 1kW Ncore,icepower,or Purifi to drive each might do the trick

Seriously now,EQ is one of useful tools when used sensibly but as anything else has/exposes limits.
So...

 

[boxerfan88]

OP stated that there is 10-14 dB correction boost a couple of places as well..

Wow!! That’s a lot of boost!

 

[Trdat]

Output voltage and input sensitivity looks like an okay match if not overdriven like mad.

The Marantz outputs 12 volts at full volume.

 

[antcollinet]

The point is that his NC252 MP shuts down with every bang down low,is not just distorting.

I don't see anything at all in the OP's description of the problem that suggests that either amp is going into protection. That would be a really obvious issue. Which strongly suggests to me the low frequency current limit is not being triggered.

And it is the higher power amp that has the audible issue from his point of view. So let's say the 20Hz limit is at 244W - with 120W rated speakers.

Also 90dB / 1W sensitivity. So if they were being driven close to that 244W, then we'd be talking about 110dB+ output.

I say again - this is by far more likely to be a speaker distortion problem, than an amp one.

 

[Sokel]

I don't see anything at all in the OP's description of the problem that suggests that either amp is going into protection. That would be a really obvious issue. Which strongly suggests to me the low frequency current limit is not being triggered.

And it is the higher power amp that has the audible issue from his point of view. So let's say the 20Hz limit is at 244W - with 120W rated speakers.

Also 90dB / 1W sensitivity. So if they were being driven close to that 244W, then we'd be talking about 110dB+ output.

I say again - this is by far more likely to be a speaker distortion problem, than an amp one.

I'm quoting him.post #54:

There is no clipping indicator, I just get close to 75 db on the Marantz volume and if a big bass drum kicks in the amp shuts off, but mainly one channel and I am very quick to bring the volume down. From this point it goes all back to normal in matter of seconds. This is why I wanted to change to the NC502MP, and because I experienced no real sense of distortion I thought I can add a few more db without to much issue.

 

[Deleted member 48726]

The Marantz outputs 12 volts at full volume.

Whoops! Can the Hypex amp even take that much voltage on its inputs?

Even if you don't have your volume cranked it's likely the AVR is outputting significant voltage in the 10-14 dB EQ boosted frequency ranges.

I would reset the EQ you have applied and see if the problem still exists. Then add boost within reason. And not boost deep nulls.

 

[antcollinet]

I'm quoting him.post #54:

But that is not the sound quality issue he was talking about in OP : his actual problem. That is just another indication that he is overdriving things.

Plus it relates to the smaller amp - which is sounding fine "up until the point of clipping" (Protection).


So I'm going to suggest (again) that the sound quality issue with the bigger amp is him being able to drive the speakers way over that level which the smaller amp is protecting him from - and causing the speakers to distort.

 

[Sokel]

But that is not the sound quality issue he was talking about in OP : his actual problem. That is just another indication that he is overdriving things.

No one talked about sound quality or tonality down the road,as it was evident that there's a real problem here when things cleared.
If an amp shuts down as easy as that,3db more won't fix it,there's other things at play here,that's what I'm saying from the start.

It's maybe our fault insisting about EQ without defining the limits which translates to people going miles ahead,filling dips with 14db (!) and expect to be ok.
Nope.

 

[Trdat]

Yeah. He hasn't returned my request as to where those corrections are done. But I suspect that it's in the bass area(s) because of the magnitude as it can only be room modes that dips so much.

Here is the typical measurement from the LP you can see where the corrections are needed, but I can't say with how many db Audiolense corrected. I can provide the filtered response or the simulated response which might give a better idea...?

 

[Trdat]

No one talked about sound quality or tonality down the road,as it was evident that there's a real problem here when things cleared.
If an amp shuts down as easy as that,3db more won't fix it,there's other things at play here,that's what I'm saying from the start.

It's maybe our fault insisting about EQ without defining the limits which translates to people going miles ahead,filling dips with 14db (!) and expect to be ok.
Nope.

Audiolense makes an autmotaic correction, I can't be too sure exactly how many db it used at what frequency but max correction in the procedure is 14db and I have dips of around 10db or so. I am presuming that there will be corrections of around 10-14db.

Yeh I am not sure about the amp shut down, I just presumed it was to many volts in from the Marantz that produces 12 volts and maximum volume so at around 75 I am newar 4 volts with peaks that I don't how high.

 

[antcollinet]

No one talked about sound quality or tonality down the road,as it was evident that there's a real problem here when things cleared.
If an amp shuts down as easy as that,3db more won't fix it,there's other things at play here,that's what I'm saying from the start.

It's maybe our fault insisting about EQ without defining the limits which translates to people going miles ahead,filling dips with 14db (!) and expect to be ok.
Nope.

Well, yes - filling 14dB isn't going to help.

Plus, to make things worse, he'll be pumping 14dB more power into the speaker for no additional SPL/volume - since the 14dB higher level reflections will still be cancelling out.

The speaker still has to do the work though.

Without going back to read the whole thread - is EQ something added based on suggestions in this thread, or was it already applied.

 

[Trdat]

Well, yes - filling 14dB isn't going to help.

Plus, to make things worse, he'll be pumping 14dB more power into the speaker for no additional SPL/volume - since the 14dB higher level reflections will still be cancelling out.

The speaker still has to do the work though.

Without going back to read the whole thread - is EQ something added based on suggestions in this thread, or was it already applied.

Eq was already applied. And left on listening to the new amp....

 

[antcollinet]

Eq was already applied. And left on listening to the new amp....

OK - so if you have a 14db Boost, that is 25 times the power at that frequency.

So if you are playing at (say) 5W average - tones at that frequency might go up as high as 125W. But you won't hear that in the volume since the null will still be cancelling.

It is why when applying EQ we don't try to fill the dips - only bring down the peaks. It sounds like you need to turn off (or re-do) your eq. At least as a starting point.