AVS › AVS Forum › Audio › DIY Speakers and Subs › Measuring Amplifiers
New Posts  All Forums:Forum Nav:

Measuring Amplifiers - Page 62

post #1831 of 1913
1/16/12 at 7:03am
Arny,

Any links to your amplifier testing? I'd really enjoy reading anything you've got.

Thanks
Reply
Reply

AVS Top Picks

post #1832 of 1913
1/16/12 at 1:55pm
Arnyk,
Have you ever pushed your XTi's to the point that the cooling fans were activated?
And if so, what part of the sound spectrum caused the fans to turn on?
What drivers are you using currently?
Reply
Reply
post #1833 of 1913
1/16/12 at 5:45pm
Quote:
Originally Posted by LINEARX View Post

Arnyk,
Have you ever pushed your XTi's to the point that the cooling fans were activated?

Yes. Both on the test bench and in actual use.

Quote:


And if so, what part of the sound spectrum caused the fans to turn on?

IME it is not about spectral content, its about power levels. No surprise!

Quote:


What drivers are you using currently?

I've used my Xti's with EV ZX-1s and a homemade subwoofer that is based on a 12" driver with dual 4 ohm voice coils. The subwoofer driver VCs are in series, and the amp is bridged. It's the subwoofer for a sound system in a 500seat venue, and it frequently runs its Xti 2000 within a few dB of clipping.

So, in one case the amp was handling broadband audio, albeit with quite a bit of bass boost below about 150 Hz, and in the other case the amp is handling 32-100 Hz for the subwoofer in a live sound system.
Reply
Reply
post #1834 of 1913
1/16/12 at 5:53pm
Quote:
Originally Posted by FOH View Post

Arny,

Any links to your amplifier testing? I'd really enjoy reading anything you've got.

I haven't published much lately.

My test equipment ranges from an AP System One (actually two operational ones on hand right now - readying for sale), to some heavily modded Heathkits, to some sound card-based, software driven setups.

Obviously, the sound card based stuff has the most impressive residuals, the AP Ssystem Ones are the easiest and nicest to use, and the Heath stuff used to be impressive 30 years ago, but not so much any more! ;-)

I did most of my sound card based testing with Spectra Lab back in the day, but more recently I've gotten lazy and cheap and mostly just run Rightmarks.

My dummy loads have built in attenuators - pretty simple stuff just a 5K 2 watt pot per channel. I have both resistive and reactive loads.

If you go to one of those internet web site archive sites, you can find my old PCAVTech web site, and also my old PCABX site.
Reply
Reply
post #1835 of 1913
1/16/12 at 6:23pm
What happens when an amp clips on subs?

Is it like a short circuit where the amp drops full power into the load?

Two Scenarios

You have an amp that has N power. You also own a couple of subs that can handle different power loads. One can handle N power x2, and another sub that can handle < N power.

Say you drive the amp load to clipping.

The sub that can handle N power x2 will do what?
Will it make a bad sound? will the amp just power cycle or trip a breaker?

The sub that can handle < N power will do what?
Will it make a bad sound? Will it blow the driver? Will the amp just light up the clip lights? Will the amp trip a internal breaker or wall breaker?
Reply
Reply
post #1836 of 1913
1/16/12 at 11:17pm
Quote:
Originally Posted by arnyk View Post

As far as I can see, the load resistors are water heater elements or something like them. The obvious and serious problem with these parts like these is their temperature coefficient which is usually very large, even for modest temperature changes.

I'd be happy to recant on this comment were I answered with actual tests of their resistance versus temperature from room temperature to the boiling point of water.

Chas gives the Rdc at the start and end of the tests.

The simple solution is to put the resistor array in a tub of water of sufficient volume, or direct enough through the tub, eg tap- tub -garden sprinkler. Unless you are soak testing, the couple of minutes taken to do the test doesn't make much difference and you wan't usually need moving water. Long term, I'd use the same, a water pump, car radiator and fan/natural cooling which would allow high power tests over a period. They work very well and are good enough for most purposes, not to mention cheap.

I have a 100W/8R generic chinese unit on the way which I'll get tested in the work lab to see how it measures and may buy more if OK, but we'll see how it goes against my new spare water heater element.
Reply
Reply
post #1837 of 1913
1/17/12 at 4:52am
Quote:
Originally Posted by Archaea View Post

What happens when an amp clips on subs?

To coin a phrase, "That depends".

Quote:


Is it like a short circuit where the amp drops full power into the load?

Not usually.

For openers, a subwoofer usually presents at least 3 different kinds of load depending on the frequency. Below resonance, it is varying from a resistor at DC to a inductor just below resonance. At resonance, it is like a high value resistor. Above resonance it is like a capacitor sloping down to the point where its voice coil reactance starts taking over and it again looks like an inductor.

These days we have the option of making the amplfier clip in its input DSP in which case the amplifier continues to drive the speaker with a low source impedance. Or, we can let the output stage clip, in which case the source impedance of the amplifier looks more like a diode. If the amplifier's output voltage is appreciably below VCC then the output devices are saturated and act like low impedances. If the amplifier's output voltage is near or above VCC the amplifier's source impedance will be high unless there are diodes that clamp the output to VCC.

Quote:


Two Scenarios

You have an amp that has N power. You also own a couple of subs that can handle different power loads. One can handle N power x2, and another sub that can handle < N power.

Say you drive the amp load to clipping.

The sub that can handle N power x2 will do what?
Will it make a bad sound? will the amp just power cycle or trip a breaker?

The sub that can handle < N power will do what?
Will it make a bad sound? Will it blow the driver? Will the amp just light up the clip lights? Will the amp trip a internal breaker or wall breaker?

The problem here is that you are presuming that the driver's power limits are relevant to the question you asked. You asked what happens when an amp clips, and then you start talking about the load. Amps are sources and speakers are loads and to a large degree their operation is separate.

Speaker drivers are unlike amplfiiers in that they don't change their operating characteristics rapidly when you increase the power you apply to them. The power handling capacity of a driver has both excursion limits and thermal limits, but compared to amplifier clipping, both limits are soft and spongy. The transition between them is dependent on signal frequency, and even that transition is soft and flexible.

For that and other reasons, speaker power ratings are more complex, vague, and pften can be generally violated without the kind of harsh short term effects we see in power amps.

Of course, good amplifiers are almost indestructable, while any speaker can be destroyed if you work at it, or are merely careless. If a speaker doesn't make ugly noises or burn up, its power ratings can be pretty much ignored. One is wise if one sizes speakers so that they either make somewhat ugly sounds or just keep on choogling, when the amplifier totally runs out of gas. A just barely undersized amp for the speaker at hand is a thing of beauty.
Reply
Reply
post #1838 of 1913
1/17/12 at 7:20am
Quote:
Originally Posted by arnyk View Post

After playing around with the alternatives for over 50 years, I now use a load resistor bank composed of a dozen forced-air-cooled 250 watt precision non-inductive resistors.
Having enough bench power to actually test modern amplifiers is another usually unmet challenge. I pulled a 30 amp (per leg) 230 volt line to the room where I test amplifiers.

`
Sorry Arnyk with the forced air cooled resistor bank and all that testing equipment, YOU have just become the AVS defacto "AMP TESTER" for AVS.
We need your address to send our amps for testing like Chasw98 did.
In addition to the testing protocol and the charts Chasw98 produced, we need pictures of each amp being tested and pictures of the equipment readouts during testing and under load.
`When can you start?
Which amp do you want to test first?
The following is a list of amps AVS members want tested:
`
1) FP14000 China Clone
2) Peavey IPR 3000 DSP
3) Peavey IPR 6000 DSP
4) Behringer EPX 4000
5) Bryston any
6) Crown ITech 8000
7) Behringer Inuke NU3000DSP
8) Yamaha P7000SP
9) Crown Macro Tech 5000 i
10) Powersoft K10, K20
`
We have AVS members anxious and ready to go.
We might be able to arrange a small stipend to defray your costs of electricity. Let us know what kind of cost you incur.
Reply
Reply
post #1839 of 1913
1/17/12 at 7:32am
actually I bet we could arrange to pay you... I bet through numerous $5 - $10 donations from people who want to see the amp tested you could gather a set fee for each amp - before it would be tested. That would reimburse you for your time spent too and be a slightly less burdensome experience if there is a bit of financial reward.
Reply
Reply
post #1840 of 1913
1/17/12 at 7:35am
Quote:
Originally Posted by Archaea View Post

actually I bet we could arrange to pay you... I bet through numerous $5 - $10 donations from people who want to see the amp tested you could gather a set fee for each amp - before it would be tested. That would reimburse you for your time spent too and be a slightly less burdensome experience if there is a bit of financial reward.

I'd be on board with this.
Reply
Reply
post #1841 of 1913
1/17/12 at 7:37am
Quote:
Originally Posted by arnyk View Post

To coin a phrase, "That depends".



Not usually.

For openers, a subwoofer usually presents at least 3 different kinds of load depending on the frequency. Below resonance, it is varying from a resistor at DC to a inductor just below resonance. At resonance, it is like a high value resistor. Above resonance it is like a capacitor sloping down to the point where its voice coil reactance starts taking over and it again looks like an inductor.

These days we have the option of making the amplfier clip in its input DSP in which case the amplifier continues to drive the speaker with a low source impedance. Or, we can let the output stage clip, in which case the source impedance of the amplifier looks more like a diode. If the amplifier's output voltage is appreciably below VCC then the output devices are saturated and act like low impedances. If the amplifier's output voltage is near or above VCC the amplifier's source impedance will be high unless there are diodes that clamp the output to VCC.



The problem here is that you are presuming that the driver's power limits are relevant to the question you asked. You asked what happens when an amp clips, and then you start talking about the load. Amps are sources and speakers are loads and to a large degree their operation is separate.

Speaker drivers are unlike amplfiiers in that they don't change their operating characteristics rapidly when you increase the power you apply to them. The power handling capacity of a driver has both excursion limits and thermal limits, but compared to amplifier clipping, both limits are soft and spongy. The transition between them is dependent on signal frequency, and even that transition is soft and flexible.

For that and other reasons, speaker power ratings are more complex, vague, and pften can be generally violated without the kind of harsh short term effects we see in power amps.

Of course, good amplifiers are almost indestructable, while any speaker can be destroyed if you work at it, or are merely careless. If a speaker doesn't make ugly noises or burn up, its power ratings can be pretty much ignored. One is wise if one sizes speakers so that they either make somewhat ugly sounds or just keep on choogling, when the amplifier totally runs out of gas. A just barely undersized amp for the speaker at hand is a thing of beauty.

Thank you for this response! The question arose from the recent KC subwoofer blind meet where a Captivator Pro pair and a CHT 18.T pair were driven of the same Inuke DSP 3000 amp and had vastly different overload characteristics. The Inuke just power cycled on the JTR Cpativator subs when it went into clipping driving the subs in 2ohm stereo mode. The amp goes all red, LCD and amp shut off and it comes back on a couple seconds later. The JTR Captivator subs never make a bad noise - just go silent for a couple seconds. I've seen this behavior multiple times before the meet in testing. It's always the same. With some prior and post meet testing on the CHT 18.T subs when the amp went into clipping bad noises were heard from the sub at 8ohm stereo mode, but the amp didn't power cycle. The Cap driver is rated for 7,200 watts peak, the CHT driver is rated for 800 watts peak.

The inuke amp puts out 1500 watts per channel in 2ohm and 440ish watts per channel in 8ohm.
Reply
Reply
post #1842 of 1913
1/17/12 at 10:44am
I haven't read the shootout thread yet, so I've no idea what happened, etc. I don't know if I've seen an amp go into protect merely at clipping, who knows,..obviously it was a shootout, and things were being ran hard. Maybe the INuke saw what it thought was a dead short,.. (full power at 2 ohms nominal). My understanding, class D amps behave oddly at clipping/overload,..and typically that's the big diff between first class bullet proof amps, and those that offer high value,...stability at the extreme.

Wow! Brutal, correct me if I'm wrong, infrasonic content, hard clipping, into 2 ohm stereo, with a 7 pound $400 amp. You know all amps possess essentially the same audible characteristics, as long as you stay away from their limits


Thanks
Reply
Reply
post #1843 of 1913
1/17/12 at 11:01am
The amp seems to do pretty well to me...I've never heard it make a bad noise before going into protect mode on the caps...it just reboots, but yes I realize I need a more powerful amp to play with. I'm considering the Crown XLS-5000 after Gorilla83's recent praise. He says it's 5-7 dB louder at max clean volume than his EP4000 on his Captivator pair.

http://www.avsforum.com/avs-vb/showt...php?p=21494000
Reply
Reply
post #1844 of 1913
1/17/12 at 1:12pm
Quote:
Originally Posted by whoaru99 View Post

In what way did the Face 1150TX beat out the PL9.0?

Wow am I late on this reply, sorry about that

Not that either amp ran out of power driving the pair of LMS Ultra's but the Face 1150TX just seamed to have an extra gear, the punch felt was very noticeable. The Face just had better control over the LMS Ultra's where as the PL9.0 sounded sloppy in comparison. The levels were the same as was the EQ, the only thing that changed was swapping amps.

I never heard the PL9.0 reach it's limits and the Face got close a few times. If more power was needed than the PL9.0 would be the way to go but for my needs the Face sounded a lot better than any sub amp I have owned before.

I also had a RMX5050 around the same time but the Face F1150TX just sounded better as well. QSC still makes excellent amps and they bested all of the other amps I had before that. The Face amps are just better sounding to me and until I find something else that bests them then there here to stay.
Reply
Reply
post #1845 of 1913
1/17/12 at 2:10pm
Quote:
Originally Posted by Archaea View Post

The amp seems to do pretty well to me...I've never heard it make a bad noise before going into protect mode on the caps...it just reboots, but yes I realize I need a more powerful amp to play with. I'm considering the Crown XLS-5000 after Gorilla83's recent praise. He says it's 5-7 dB louder at max clean volume than his EP4000 on his Captivator pair.

http://www.avsforum.com/avs-vb/showt...php?p=21494000

Yeah, I saw that, seems to be a good match with the Caps. At the price at which that amp can be had, a nice little deal. Maybe they're closing them out, I don't know.
Reply
Reply
post #1846 of 1913
1/17/12 at 4:16pm
Quote:
Originally Posted by mjaudio View Post

Not that either amp ran out of power driving the pair of LMS Ultra's but the Face 1150TX just seamed to have an extra gear, the punch felt was very noticeable. The Face just had better control over the LMS Ultra's where as the PL9.0 sounded sloppy in comparison. The levels were the same as was the EQ, the only thing that changed was swapping amps.

I never heard the PL9.0 reach it's limits and the Face got close a few times. If more power was needed than the PL9.0 would be the way to go but for my needs the Face sounded a lot better than any sub amp I have owned before.

I also had a RMX5050 around the same time but the Face F1150TX just sounded better as well. QSC still makes excellent amps and they bested all of the other amps I had before that. The Face amps are just better sounding to me and until I find something else that bests them then there here to stay.

`
That's an interesting analysis. I would have thought the bigger more powerful QSC amps would have been more impressive and accurate.
The F1150TX is only 1150 watts @ 4 ohms VS
PL9.0 3400 watts @ 4 ohms VS
RMX5050 1800 watts @4 ohms.
Reply
Reply
post #1847 of 1913
1/17/12 at 4:32pm
Quote:
Originally Posted by arnyk View Post

At resonance, it is like a high value resistor.

Yes, for a sealed box.

For a ported box, at Fb the impedance has a minimum that's close to Re.
Reply
Reply
post #1848 of 1913
1/17/12 at 4:33pm
Quote:
Originally Posted by LINEARX View Post

`
That's an interesting analysis. I would have thought the bigger more powerful QSC amps would have been more impressive and accurate.
The F1150TX is only 1150 watts @ 4 ohms VS
PL9.0 3400 watts @ 4 ohms VS
RMX5050 1800 watts @4 ohms.

I would have thought the same thing but I went back and forth for a good month or more but couldn't give up the F1150TX. I wanted to like the PL9.0 as it is an insane piece of engineering but the Face amp just sounded better.
Reply
Reply
post #1849 of 1913
1/18/12 at 5:52am
Quote:
Originally Posted by noah katz View Post

Yes, for a sealed box.

For a ported box, at Fb the impedance has a minimum that's close to Re.

That's because of the effect of the port's resonance which is an anti-resonance from the perspective of the driver. Depending on the Q and tuning of the box, driver and the port, the dip may not go all the way down to Re.

Here's an example:

http://www.stereophile.com/content/v...r-measurements
Reply
Reply
post #1850 of 1913
1/18/12 at 8:46am
Quote:
Originally Posted by LINEARX View Post

`
That's an interesting analysis. I would have thought the bigger more powerful QSC amps would have been more impressive and accurate.
The F1150TX is only 1150 watts @ 4 ohms VS
PL9.0 3400 watts @ 4 ohms VS
RMX5050 1800 watts @4 ohms.

Originally Posted by mjaudio View Post
Not that either amp ran out of power driving the pair of LMS Ultra's but the Face 1150TX just seamed to have an extra gear, the punch felt was very noticeable. The Face just had better control over the LMS Ultra's where as the PL9.0 sounded sloppy in comparison. The levels were the same as was the EQ, the only thing that changed was swapping amps.


this is where one of the problem is the PL9 needs 3.0 volts to be driven to it max when the face needs only 1.4 volts. just push her a little more you should feel a little difference 3 db ish .
Reply
Reply
post #1851 of 1913
1/18/12 at 8:56am
Quote:
Originally Posted by kouack View Post

Originally Posted by mjaudio View Post
Not that either amp ran out of power driving the pair of LMS Ultra's but the Face 1150TX just seamed to have an extra gear, the punch felt was very noticeable. The Face just had better control over the LMS Ultra's where as the PL9.0 sounded sloppy in comparison. The levels were the same as was the EQ, the only thing that changed was swapping amps.


this is where one of the problem is the PL9 needs 3.0 volts to be driven to it max when the face needs only 1.4 volts. just push her a little more you should feel a little difference 3 db ish .

3db is not a little difference. I am not exactly sure what your trying to say but is it that the PL9.0 would outperform the F1150TX at max levels? If that's the case then I would tend to agree since I could push past the F1150's comfort zone but I never listen that loud anyway. Even then the Face amp sounded better than the PL9 right up until ear bleeding levels.
Reply
Reply
post #1852 of 1913
1/19/12 at 3:45pm
Quote:
Originally Posted by mjaudio View Post

3db is not a little difference. I am not exactly sure what your trying to say but is it that the PL9.0 would outperform the F1150TX at max levels? If that's the case then I would tend to agree since I could push past the F1150's comfort zone but I never listen that loud anyway. Even then the Face amp sounded better than the PL9 right up until ear bleeding levels.

Simple what i was trying to say, to figure out if an amplifier sound different to the other one you shall match level first before trying to listen to them, if one is playing louder because you haven't match level, that amp will probably sound better to you .
Reply
Reply
post #1853 of 1913
1/19/12 at 4:10pm
Quote:
Originally Posted by kouack View Post

Simple what i was trying to say, to figure out if an amplifier sound different to the other one you shall match level first before trying to listen to them, if one is playing louder because you haven't match level, that amp will probably sound better to you .

Maybe I didn't make it clear when I said:

"The levels were the same as was the EQ, the only thing that changed was swapping amps"

I did match up the levels on the amps so that one was not playing louder than the other. I not only checked with my Galaxy spl meter but my SMS-1. I am pretty sure I had the omnimic at the time and used it's SPL meter just to make sure it was a fair test.

To clarify it was the levels on the amp, not the levels in the pre-amp was was kept the same. I even went as far as having all the trim pots turned up then setting the levels on the pre-pro individually to make sure that wasn't the difference. I only did the last part as I couldn't understand why the F1150TX sounded better than the PL9 or even the RMX5050, not what I was expecting at all.
Reply
Reply
post #1854 of 1913
1/19/12 at 5:33pm
could be my french side lol from what i did read i was under the impression you did not match level and yes i thought you kept the same level on the pre amp, so my first comment on the 1.4 and 3 volts, cheer.
Reply
Reply
post #1855 of 1913
1/20/12 at 9:58pm
You know; I still have that new 2000TX sitting in my rack. Likely been a year since we last shared bench racing stories via PM, and I still haven't put it to use.

I still have the 3 1200TS units too, and I'm looking to do some dual opposed 15" units at three mid-wall points.

I'm thinking about picking up an LMS Ultra to mate with the 2000TX and place her at the mid-wall closest to me.

Hope you've been well!

Larry

Quote:
Originally Posted by mjaudio View Post

Wow am I late on this reply, sorry about that

Not that either amp ran out of power driving the pair of LMS Ultra's but the Face 1150TX just seamed to have an extra gear, the punch felt was very noticeable. The Face just had better control over the LMS Ultra's where as the PL9.0 sounded sloppy in comparison. The levels were the same as was the EQ, the only thing that changed was swapping amps.

I never heard the PL9.0 reach it's limits and the Face got close a few times. If more power was needed than the PL9.0 would be the way to go but for my needs the Face sounded a lot better than any sub amp I have owned before.

I also had a RMX5050 around the same time but the Face F1150TX just sounded better as well. QSC still makes excellent amps and they bested all of the other amps I had before that. The Face amps are just better sounding to me and until I find something else that bests them then there here to stay.
Reply
Reply
post #1856 of 1913
1/21/12 at 8:32am
Quote:
Originally Posted by 04FLHRCI View Post

You know; I still have that new 2000TX sitting in my rack. Likely been a year since we last shared bench racing stories via PM, and I still haven't put it to use.

I still have the 3 1200TS units too, and I'm looking to do some dual opposed 15" units at three mid-wall points.

I'm thinking about picking up an LMS Ultra to mate with the 2000TX and place her at the mid-wall closest to me.

Hope you've been well!

Larry

That 2000TX is one sweet amp, I wish I had one

Which 15" subs were you thinking for your dual opposed?

You won't be disappointed with the LMS Ultra, cleanest sub I have ever owned.

I hope your doing well too my friend.

Mike
Reply
Reply
post #1857 of 1913
1/21/12 at 8:40am
Here's a shot of my Face amps. One of the F1200TS is gone and this was before the 1150TX and 1600, I need to update my picture.



I think only 1 Face amp was actually connected, I put the others in there to take a pic for some buddies.
LL
Reply
Reply
post #1858 of 1913
1/21/12 at 3:35pm
Quote:
Originally Posted by Archaea View Post

The amp seems to do pretty well to me...I've never heard it make a bad noise before going into protect mode on the caps...it just reboots, but yes I realize I need a more powerful amp to play with. I'm considering the Crown XLS-5000 after Gorilla83's recent praise. He says it's 5-7 dB louder at max clean volume than his EP4000 on his Captivator pair.

http://www.avsforum.com/avs-vb/showt...php?p=21494000

Hey Archaea, have you done a "write-up" on the INUke NU3000? If so point me to it. If not, get busy.
Phil
Reply
Reply
post #1859 of 1913
1/22/12 at 7:19am
Quote:
Originally Posted by LINEARX View Post

Hey Archaea, have you done a "write-up" on the INUke NU3000? If so point me to it. If not, get busy.
Phil

http://www.avsforum.com/avs-vb/showt...7#post21261117

Here ya go.

I like the Inuke amp. It's a nice little amp.
http://www.avsforum.com/avs-vb/showt...7#post21261117
Reply
Reply
post #1860 of 1913
2/29/12 at 8:35pm
Quote:
Originally Posted by Archaea View Post

The amp seems to do pretty well to me...I've never heard it make a bad noise before going into protect mode on the caps...it just reboots, but yes I realize I need a more powerful amp to play with. I'm considering the Crown XLS-5000 after Gorilla83's recent praise. He says it's 5-7 dB louder at max clean volume than his EP4000 on his Captivator pair.

http://www.avsforum.com/avs-vb/showt...php?p=21494000

Hopefully I didn't miss something earlier on, but sounds to me like it might be an issue with intolerance to AC line sag, not necessarily something going on with protect from hard use, per se.
Reply
Reply
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: DIY Speakers and Subs

AVS Top Picks

AVS › AVS Forum › Audio › DIY Speakers and Subs › Measuring Amplifiers