Amp Clipping Issue

[panteragstk]

1 meter since obviously I don't know what his room is like nor his seating distance

Room dimensions are 17'x13.5'x8'. Screen is on the 13.5' wall. First row is ~11' from the screen. Back row is at the back wall. Subs are positioned on either side of the screen. Sub placement is pretty limited unless I place them under the riser (which is possible). No room treatments to speak of.

I'm actually not finished with the room yet, and the next stage is dealing with room acoustics. That's obviously a whole other thread.

 

[panteragstk]

It is. You just found your systems limits. You really didn't pick up on that yet?

No, I got it. Guess I'm not good at saying that without simply stating it. I promise, I'm not as dense as it may seem.

All I'm trying to figure out here is if (as you say, which I agree with BTW) I've hit my system limit, or there is a possible problem somewhere.

 

[panteragstk]

It could have been ruled out by trying that disc on another system, particularly since OP says they did torture testing on another system, with other discs, but not that one.

...that would have narrowed it down to either the disc or the DAC, but no...

I guess that when one only has hammer, every problem looks like a nail.

I'd love to try on another system, but have no real ability to do so since I'm the only person I know with a sub that will even come close to handling the material.

 

[markw]

Ever heard of hte process of elimination?

IT's great wy of finding problems. You rule out one area at a time.

Tt could be the amp and speakers, but since you say it still craps out at half volume, that rules out the amp and speakers, right? If it was the amp/speakers, it would be clean at half volume. Gotta look at somethin else for the problem.

If it was the disc that's at fault, it would be faulty on any system, right? So, you don't need a bass heavy system to test the disc, do you? It should crap out on any system if it's the disc. If it works on another system, you should look at the DAC

Since te disc worked on another system, you need to get hold of another DAC (whatever does your processing) or receiver to test with your system.

Or, maybe your speakers can't go as low as you think they can. Do they hold up to those bass test CD's the car guys are so fond of? If not, well, maybe it is the drivers.

So far, we can't say what it is, but we can sure say what it isn't, and that's the amp/speakers.

Balls in your court.

P.S. You do know tey are specced for only 300 watts RMS, don't you? Here's the spec sheet. How much are you feeding 'em?

 

[panteragstk]

P.S. You do know tey are specced for only 300 watts RMS, don't you? Here's the spec sheet. How much are you feeding 'em?

So yes, very familiar with process of elimination.

First I thought the gain on the amp was too high. Lowered that and raised the level on the receiver so I'd get the same output level (75db at the SPL meter). Peak limiter engaged at the same spot
Second I tried a different source (internal PC sound card instead of the 809). Same result as above.
Third I tried lowering the gain on the amp as far as I could while still being able to get 75db at the spl meter using the 809 again. Same
Fourth I tried a totally different receiver (internal sound cards don't have the cleanest signal). Same
Fifth I tried rewiring the subs from 2 ohm (amp feeding them 775w) to 8 ohm (amp feeding them 300w). Problem gone

So, either I was pushing the drivers too hard (not sure how the peakx limiter would know that) or the driver was asking for more power than the amp could provide at the db level I was asking of the driver. Lowering to 8 ohms puts the amp at outputting 600w total instead of 1550w total. I'm honestly thinking the amp can't handle that low of an ohm load at max output. Of course I could be totally wrong.

Was I asking too much of the amp or the driver? I never heard any audible distortion or clipping from the driver, but that could be the amp protecting it right? I've heard a woofer clip many times and that just isn't happening.

This brings up a question: Since the RMS is rated at 300w I'm feeding them the exact RMS wattage. However, with the peak being 1200w, wouldn't 775w be OK for the driver? When I sold pro audio I was taught to go between rms and peak of the speaker when trying to figure out what amp to pair it with. Is that wrong? I've never had an issue with it (again, pro audio, not car or home) is there a difference in the way that pro gear is rated vs car or home? So by my logic 600w would be perfect for these drivers and the 775w would be more than that (obviously) but still within the OK range. I'd really like to know if I've been wrong all these years.

This is another learning experience for me and ALL of you have been huge help. I promise Mark, I'm not the moron I can come across as being. Trying to get my thoughts into a forum doesn't work as well as me just saying out loud what I'm thinking. I'm apparently less than clear. I'll try to get better.

 

[markw]

So yes, very familiar with process of elimination.

First I thought the gain on the amp was too high. Lowered that and raised the level on the receiver so I'd get the same output level (75db at the SPL meter). Peak limiter engaged at the same spot
Second I tried a different source (internal PC sound card instead of the 809). Same result as above.
Third I tried lowering the gain on the amp as far as I could while still being able to get 75db at the spl meter using the 809 again. Same
Fourth I tried a totally different receiver (internal sound cards don't have the cleanest signal). Same
Fifth I tried rewiring the subs from 2 ohm (amp feeding them 775w) to 8 ohm (amp feeding them 300w). Problem gone

So, either I was pushing the drivers too hard (not sure how the peakx limiter would know that) or the driver was asking for more power than the amp could provide at the db level I was asking of the driver. Lowering to 8 ohms puts the amp at outputting 600w total instead of 1550w total. I'm honestly thinking the amp can't handle that low of an ohm load at max output. Of course I could be totally wrong.

Was I asking too much of the amp or the driver? I never heard any audible distortion or clipping from the driver, but that could be the amp protecting it right? I've heard a woofer clip many times and that just isn't happening.

Read that link below. It sounds like your amp was protecting itself,and possibly youtr speakers.

This brings up a question: Since the RMS is rated at 300w I'm feeding them the exact RMS wattage. However, with the peak being 1200w, wouldn't 775w be OK for the driver? When I sold pro audio I was taught to go between rms and peak of the speaker when trying to figure out what amp to pair it with. Is that wrong? I've never had an issue with it (again, pro audio, not car or home) is there a difference in the way that pro gear is rated vs car or home? So by my logic 600w would be perfect for these drivers and the 775w would be more than that (obviously) but still within the OK range. I'd really like to know if I've been wrong all these years.

Click here for a brief definition on the various terms used to rate amplifier power. Please note # 4 which states, in part, "Peak power here refers to the maximum amount of power an electronic component can possibly handle for an instant without damage". What's your definition of "an instant"?

Also, read further in that part to see what it says about distortion. Keep in mind that the demand on an amp is the greatest when called upon for loud, deep bass, particularly when it lasts for more than "an instant".

On top of that, your speaker are not an infinite source of loudness. They have their physical limits as well. While some speakers may disintigrate your ear drums in the tiny, closed environment of a car, their overall effectiveness is far less when used in a larger home environment where they are asked to move a lot more air in a much larger area.

This is another learning experience for me and ALL of you have been huge help. I promise Mark, I'm not the moron I can come across as being. Trying to get my thoughts into a forum doesn't work as well as me just saying out loud what I'm thinking. I'm apparently less than clear. I'll try to get better.

 

[panteragstk]

Thanks for the link. You were spot on when you said I found the limit of my system. Thanks again for the help.

 

[AcuDefTechGuy]

Maybe I overlooked, but which scene in the movie invariably caused this amp clipping? I have to try on my system.

 

[jinjuku]

Maybe I overlooked, but which scene in the movie invariably caused this amp clipping? I have to try on my system.

You beat me to it. I was just logging on to ask the same. So a few members could go through it and post their results. Is it DVD or BR?

 

[panteragstk]

Maybe I overlooked, but which scene in the movie invariably caused this amp clipping? I have to try on my system.

You beat me to it. I was just logging on to ask the same. So a few members could go through it and post their results. Is it DVD or BR?

It's the one right after the multiple lightning strikes when everyone is looking at the ground. When everything starts cracking and falling apart as the machine comes out of the ground is when the limiter engaged.

It still gets to the top of the LED meter (turns red), but now that I'm not asking 1550w it's doesn't freak out. Now I need to figure out what driver I'm going to upgrade to.

 

[jinjuku]

This brings up a question: Since the RMS is rated at 300w I'm feeding them the exact RMS wattage. However, with the peak being 1200w, wouldn't 775w be OK for the driver? When I sold pro audio I was taught to go between rms and peak of the speaker when trying to figure out what amp to pair it with. Is that wrong? I've never had an issue with it (again, pro audio, not car or home) is there a difference in the way that pro gear is rated vs car or home? So by my logic 600w would be perfect for these drivers and the 775w would be more than that (obviously) but still within the OK range. I'd really like to know if I've been wrong all these years.

Class D takes a twist on this. Class D is 80-90% efficient which means that when you normally see a 300 RMS rating there isn't much more the amp is going to do above that. That 300 number was reached with 80-90%. Not 50% (as example) of a typical A/AB class amp.

Some are buying Class D amp that is rated higher than their RMS value of what they are going to be driving.

 

[markw]

It's the one right after the multiple lightning strikes when everyone is looking at the ground. When everything starts cracking and falling apart as the machine comes out of the ground is when the limiter engaged.

Mrs W's family is from down neck Newark where that was filmed and two of her brothers still live there. We are in that neighborhood quite often and we pass through that corner (Ferry St & Wilson Ave) frequently. St Stephens church is sort of a local landmark, even before that movie.

 

[AcuDefTechGuy]

It's the one right after the multiple lightning strikes when everyone is looking at the ground. When everything starts cracking and falling apart as the machine comes out of the ground is when the limiter engaged.

Okay, everybody, let's check out that scene tonight.

I don't think my dual Funk 18.0 (4 ohms) will bottom out, so I'll see how my ATI AT3002 handles it. At 1% THD, I think the AT3002 is capable of 600+ watts into 4 ohms.

 

[PENG]

DVD or BR? I only have the DVD on that one.

 

[avengineer]

Class D takes a twist on this. Class D is 80-90% efficient which means that when you normally see a 300 RMS rating there isn't much more the amp is going to do above that. That 300 number was reached with 80-90%. Not 50% (as example) of a typical A/AB class amp.

Some are buying Class D amp that is rated higher than their RMS value of what they are going to be driving.

Sounds like you're saying that Class D has no significant dynamic headroom. Is that correct?

 

[panteragstk]

Mrs W's family is from down neck Newark where that was filmed and two of her brothers still live there. We are in that neighborhood quite often and we pass through that corner (Ferry St & Wilson Ave) frequently. St Stephens church is sort of a local landmark, even before that movie.

Pretty cool.

DVD or BR? I only have the DVD on that one.

Blu-ray.

 

[AcuDefTechGuy]

DVD or BR? I only have the DVD on that one.

I have the BD, but I didn't have time to check it out last night. On my Task List.

 

[jinjuku]

Sounds like you're saying that Class D has no significant dynamic headroom. Is that correct?

My understanding of Class D in that regard is when you are close to the wall of the amps output it isn't going to have much more to give. Honestly an amp designer familiar with both D and A/AB/H/ etc topologies would be the best to ask.

 

[panteragstk]

My understanding of Class D in that regard is when you are close to the wall of the amps output it isn't going to have much more to give. Honestly an amp designer familiar with both D and A/AB/H/ etc topologies would be the best to ask.

Gene would be able to explain this very well. Maybe he'll chime in.

 

[avengineer]

My understanding of Class D in that regard is when you are close to the wall of the amps output it isn't going to have much more to give. Honestly an amp designer familiar with both D and A/AB/H/ etc topologies would be the best to ask.

I think you may be attributing a characteristic of a specific design implementation to a topology, when in fact they are separate issues. It is possible to design an amp with high dynamic headroom using any topology, but it may be more cost effective in certain ones. There's no reason a class D amp couldn't be designed with high dynamic headroom, but it may be more cost effective to just build in a higher maximum peak power than to try to do it dynamically.