Switched Amps. Where Could The Difference Be Coming From?

[Trdat]

They don't even have to be comprehensive. Just a simple measurement using music that he thinks shows the effect (equipment needed: soundcard/interface and four resistors) and waveform comparison using @pkane 's incredible software. If there's clipping or overload or whatever from the amp, the differences will be trivially easy to see.

I can measure with REW and have a db meter so I can level match but measuring from the amp with a volt meter is something I can't do.

 

[Deleted member 48726]

Bookshelf-3WC

What's your listening position distance from the speakers?

How loud do you listen when you experience distortion?

Have you applied any EQ or room correction?

Which amplifier do you use to control volume?

 

[Trdat]

Maybe a silly question but it needs to be asked, are you sure you didn't connect the speakers out of phase?

You mean from the terminals?

But the DSP would take care of phase 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?

 

[Trdat]

What's your listening position distance from the speakers?

3.5 meters

How loud do you listen when you experience distortion?

Well I didn't experience distortion with the NC252 even close to clipping around 90db C weighted. But I didn't check the loudness when cranking the NC502 but it was only mildly louder but definitely higher volume from the Marantz AVR.

Have you applied any EQ or room correction?

Yes, Audiolense creates an automatic filter after proper measurements. The subs are also time aligned from the AVR with the Audiolense DSP correction on top of that for music listening.

Which amplifier do you use to control volume?

Marantz AV7005

 

[Trdat]

Yes

Yep,and lets not forget that doubling the power results in a 3db SPL rise,not much if in the previous condition was already clipping.

(I have to ask,how does the clipping was evident?Does the NC252 MP built has an indicator? )

Yes, the Hyoex has some protection system that automatically turns the amp off. It still sounds great close to clipping and then just turns off and I immediately turn volume down and it turns on again.

 

[Sokel]

Yes

Yes, the Hyoex has some protection system that automatically turns the amp off. It still sounds great close to clipping and then just turns off and I immediately turn volume down and it turns on again.

So,to be exact,the clipping indicator (led) is blinging and after pushing it a while the amp shuts off?

 

[SIY]

I can measure with REW and have a db meter so I can level match but measuring from the amp with a volt meter is something I can't do.

You don't need a voltmeter, you're just recording signal (i.e., a section of the music where you think you're hearing a difference). Use pkane's software, it's free. The only "complication" is that you want to protect your interface or soundcard, thus the four resistors to make a voltage divider for each channel. 10:1 would be appropriate (10k series and 1k shunt are close enough, exactness isn't critical). Any level-matching issues are handled in the software.

 

[Deleted member 48726]

3.5 meters

Well I didn't experience distortion with the NC252 even close to clipping around 90db C weighted. But I didn't check the loudness when cranking the NC502 but it was only mildly louder but definitely higher volume from the Marantz AVR.

Yes, Audiolense creates an automatic filter after proper measurements. The subs are also time aligned from the AVR with the Audiolense DSP correction on top of that for music listening.

Marantz AV7005

Nothing alarming about your listening pos. or the SPL.
Nothing alarming about the speaker. It's a 3-way nom 8 ohm with quite flat phase/impedance with a min. Z = 3.3 ohm at 125 Hz.
What I would like to know is how does the correction EQ from your AVR look like? How much does it boost?
How much voltage does the AVR output?
What is the input sensitivity of the Hypex amp? What is it's max input voltage (clipping point) ?
Do you have the speakers high-passed? -You mentioned subs.

 

[Sokel]

Nothing alarming about your listening pos. or the SPL.
Nothing alarming about the speaker. It's a 3-way nom 8 ohm with quite flat phase/impedance with a min. Z = 3.3 ohm at 125 Hz.
What I would like to know is how does the correction EQ from your AVR look like? How much does it boost?
How much voltage does the AVR output?
What is the input sensitivity of the Hypex amp? What is it's max input voltage (clipping point) ?
Do you have the speakers high-passed? -You mentioned subs.

Troels says he's driving the speaker with his 32 watt tube amp to thunderous levels
What's going on here?

 

[Dimitri]

Bookshelf-3WC

So...these are "120W" speakers that first were being fed from a 250W amp that then was upgraded to a 500W amp.

What I believe is being heard is not a "difference in the amps" but the effects of the speakers being "over-excited".

To repeat the speaker designer's words: (taken from http://www.troelsgravesen.dk/power-handling.htm ) (emphasis in bold is mine)
"....The lesson to be learned from this is that we do not feed a 95 dB speaker for domestic use 400 solid state watts. This doesn't mean it cannot be driven from such an amp, but if your kids turn the volume knob all the way we may blow our drivers. Using 400 watt solid state amps we better think about what kind of speaker to use and maybe we have to look for PA drivers in case we also want to play seriously loud. Very few "hifi" speakers can handle disco levels. But don't think just because a PA driver is rated 600 watt, these watts come with reservations in terms of what kind of signal they are fed and for how long. ..."

 

[Blumlein 88]

I can measure with REW and have a db meter so I can level match but measuring from the amp with a volt meter is something I can't do.

Buy a voltmeter. They are pretty cheap.

 

[Trdat]

You don't need a voltmeter, you're just recording signal (i.e., a section of the music where you think you're hearing a difference). Use pkane's software, it's free. The only "complication" is that you want to protect your interface or soundcard, thus the four resistors to make a voltage divider for each channel. 10:1 would be appropriate (10k series and 1k shunt are close enough, exactness isn't critical). Any level-matching issues are handled in the software.

Ill take a look, don't know about Pkanes software but I am sure there is some instructions I can follow.

 

[Trdat]

What I would like to know is how does the correction EQ from your AVR look like? How much does it boost?

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.

How much voltage does the AVR output?

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...

What is the input sensitivity of the Hypex amp? What is it's max input voltage (clipping point) ?

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...

Do you have the speakers high-passed? -You mentioned subs.

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

 

[Trdat]

So,to be exact,the clipping indicator (led) is blinging and after pushing it a while the amp shuts off?

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.

 

[Trdat]

So...these are "120W" speakers that first were being fed from a 250W amp that then was upgraded to a 500W amp.

What I believe is being heard is not a "difference in the amps" but the effects of the speakers being "over-excited".

I am also thinking along those lines, hence why in my original post I mentioned that it could be that the bass driver was just receiving too much power at that 4ohms.

 

[Trdat]

Buy a voltmeter. They are pretty cheap.

Got one, but what would I be measuring? The voltage out of the amps? I am sure I can probably try and learn how to manage it, plenty of stuff on youtube to learn how to measure voltage.

 

[Blumlein 88]

Got one, but what would I be measuring? The voltage out of the amps? I am sure I can probably try and learn how to manage it, plenty of stuff on youtube to learn how to measure voltage.

It is simpler than any other method to match output. Put red on red and black on black at the speaker terminals. Feed it a 400 hz tone at -10 to -20 dbFS just be consistent with whichever you use. Start with volume at a normal comfortable listening level. Read the voltage. Most voltmeters even pick the proper range, but if not very simple. Literally yes a youtube video if it makes you feel confident and you can learn it in 5 minutes.

Once you have read the voltage, swap to the other amp. Voltage is probably different. Adjust 2nd amp to read within 2% (really 1.5% is better) of the same voltage. Note the volume position. Then you can switch amps and keep output levels the same.

 

[Sokel]

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.

What you describe is not clipping.
Either thermals kick in or some other limiter (voltage,current,something).

You should better check if something is off with the speaker,that's not normal.

 

[Sokel]

Got one, but what would I be measuring? The voltage out of the amps? I am sure I can probably try and learn how to manage it, plenty of stuff on youtube to learn how to measure voltage.

What @Blumlein 88 said and pay attention not to short them,steady hands and you'll be ok.

 

[Blumlein 88]

If you insist on using a sound level meter and REW it can be done if you are very careful. You need to use the RTA and averaging function with at least 4 averages. Use at least 128 k FFT (as long as sample rates are not above 48 khz). Using a tone 1 khz is about as good as any. You have to stand in the same spot, as even moving from one spot to another during the two measurements will cause the reading to fluctuate. This will average out other noises enough to get repeatable .1 db accuracy which is the goal. If you had some unusual noise like a neighbor's leaf blower, lawn mower etc even this might not work.

I don't know how well using pink noise will work as suggested by speedskater. I've tried it and seem to remember you could sometimes get okay results and sometimes not after restricting the pink noise to 500-2000 hz. The single tone was more precise if you are careful.

Capturing a music file as SIY describes would be more informative of what is going on. Capture the two files and match in Deltawave. I would caution you to make sure you understand this before doing it.