or Connect
AVS › AVS Forum › Audio › Audio theory, Setup and Chat › Question on bi-amping
New Posts  All Forums:Forum Nav:

Question on bi-amping - Page 27

Quote:
Originally Posted by DonH50

Quote:
Originally Posted by amir
What is the impedance at DC (0 Hz) for the tweeter circuit Arny?
Amir, are you just wanting an impedance plot over frequency?

DC is not a realistic data point, but sweeping 10 Hz to 20 kHz is easily done.

+1

I'm sure that Amir knows full well that DC is not an audio frequency because by definition DC has no frequency at all. He also knows that impedance is only a characteristic of AC circuits.

Therefore his question is a trick question, and thus shows disrespect.

Amir put an EE degree on his resume, so its reasonable to hold him accountable for at least EE101! ;-)
Edited by arnyk - 11/29/13 at 9:38am

Quote:
Originally Posted by PrimeTime

Quote:
Originally Posted by DonH50

I created a 16-bit digital sine wave in a math program (Mathcad or Matlab, not sure which I used then) then used the program to create a .wav file. Essentially I created a mathematically perfect sine wave (to the 80-bit IEEE spec), digitized by a perfect 16-bit DAC, then spit out the audio file. To clip it I simply overdrove the input of my (model) DAC by the appropriate percentage. This is harder clipping than real amplifiers exhibit but this was only for illustrative purposes. It was a while back so I am not sure if the final output was full-scale or not; I should have scaled it down to reduce the chance of the system DAC and buffers clipping but I am not sure I did that. It was just a quick and dirty test/example to help people understand what clipping sounded like. I may have repeated with two tones, it was one of my goals, but I am not sure I did (do not recall off-hand). IMD is much more noticeable on test tones (for example, IMD3 is about 9.5 dB higher than HD3, about twice as loud in the mid-band, and stands out more since it is not harmonic).
Wow -- sounds like a lot of work.

Me, I just plug the ol' signal generator in where it says "Input," attach the 'scope leads to where it says "Output," and toin the knob up until it stops looking all sine-ey. Ten seconds, tops.

The digital age is amazing in many respects, but sometimes we get carried away. Reminds me of an app note in EDN a long time ago: "Microprocessor replaces dial cord in car radio."

I laughed at the seeming absurdity of using millions of transistors as a substitute for something so simple. Looks like modern times had the last laugh on me, as that's the way it's done now (if you even have a "radio" in your car).

Still.... I think the tactile feedback provided by the dedicated dial cord system was a lot safer than the modern way where you have to monitor some kind of readout to see what "mode" your knob-twirling is controlling.

My old analog signal generator is buried in the basement someplace, and I can generate the file far quicker on my PC (seconds) than finding it, making sure it still works, getting a 'scope so I can measure the amount of clipping for a controlled study, then getting an ADC and PC hooked up to create the wave files so I could post them. This was not for myself, remember, it was to give others a chance to hear it in a controlled way. I was also doing spectral analysis and do not have an analog spectrum analyzer at home, and in any event this was a trivial exercise whilst I was working on something else. Since I already had all the functions in place, it took far less time than posting about it.

Sneer if you want, but I design and test analog circuits for a living, and have to admit sometimes digital can be a big help. In the radar and SerDes world it takes some serious processing to measure compliance to various standards, and most of my life I designed data converters and their ilk so have always had to know a little of both worlds.
Actually, the real absurdity is that I went back to one of my old files and generated a plot of the impedance for a first-order crossover using just an L and C and 8-ohms loads, then realized there's just no point in posting it. A decade away from the crossover point the impedance will be ten times the load, assuming you place the 3 dB point at the crossover frequency, and of course the impedance for an ideal circuit goes to infinity as frequency goes to 0 or infinity depending which side you are checking. For a 1 kHz crossover (what I had in my file) and 8-ohm loads (tweeter/woofer), the impedance is 80 ohms at 100 Hz or 10 kHz looking into the "off" side, and 800 ohms at 10 Hz/100 kHz. Power goes down linearly as the impedance rises, 1/10 a decade away, 1/100 two decades away.

A higher-order design will go off (rise in impedance) more quickly, always assuming no shunt elements in the circuit (i.e. it depends upon the crossover design). In the real world parasitics will limit the impedances to less than infinity at the extremes.

I don't think this has ever been debated in these threads, the argument is always about the audible impact of the reduced power demand for out-of-band frequencies when the voltages at the terminals of the two amp channels remain the same. We're back to if current clipping dominates, passive bi-amping can help; if voltage clipping dominates, it won't. So far evidence I have seen and IME leads to gaining maybe 1 - 2 dB at clipping for a passively-bi-amped system. That looks significant but is a pretty small increase in volume and that is at clipping where most systems are already pretty durn loud.
Quote:
Originally Posted by DonH50

My old analog signal generator is buried in the basement someplace, and I can generate the file far quicker on my PC (seconds) than finding it, making sure it still works, getting a 'scope so I can measure the amount of clipping for a controlled study, then getting an ADC and PC hooked up to create the wave files so I could post them. This was not for myself, remember, it was to give others a chance to hear it in a controlled way. I was also doing spectral analysis and do not have an analog spectrum analyzer at home, and in any event this was a trivial exercise whilst I was working on something else. Since I already had all the functions in place, it took far less time than posting about it.

Sneer if you want, but I design and test analog circuits for a living, and have to admit sometimes digital can be a big help. In the radar and SerDes world it takes some serious processing to measure compliance to various standards, and most of my life I designed data converters and their ilk so have always had to know a little of both worlds.
I don't think you need to defend yourself on this at all Don. Simulations are quite useful since one can easily change values of parts and re-run. All one needs is a computer so the work can be done anywhere. I was once arguing how an amplifier circuit works on another forum while I was in Japan. The other person kept insisting he was right. While going from Tokyo to Osaka on bullet train, I pulled out my laptop, ran the spice simulation and post the results later that night which settled the argument . Would have been kind of hard to build an amplifier on the train.

For others not knowing, Don does a superb job of breaking down problems/circuits/technology to a level everyone understands. He has post many super useful tutorials on WBF Forum. Here is the link to the one that I think he is talking about here: http://www.whatsbestforum.com/showthread.php?8484-Clipping-101. I think one look at that and you realize a crusty old scope and generator would not remotely be able to generate such results.

I pride myself in knowing a lot about analog design, having grown up with it as a hobby when I was young, and both practicing it in person and and as a manager of groups that developed hardware for many, many years. In the context of this topic I have so much experience with amplifier design that you could blindfold me, and by touch alone I can tell you the part number for every component in the amp!!! OK, there is no way I can do that but it sounded good writing it. Despite this level of experience, I am waiting any minute for Don to school me on one of these topics . So don't let the calm, respectful and modest tone of Don fool you. He is one of our top experts in this thread despite his measured posts.
Quote:
Originally Posted by amirm

I mentioned yesterday that I had data on other AVRs. Here is the Pioneer Elite SC-63 response. Again yellow is the "woofer" amp and green the "tweeter:"

Not the picture of "clipping" that you had in mind, right? The Pioneer uses a switchmode (class D) amplifier. We see that design topology creates very different looking amplifier response at the limit.

Amir, can't you be straight with us just once?

Just lately you were asking trick questions about DC impedance which is an oxymoron, and now it turns out you have been basing your clipping experiments on an amp that has very atypical clipping?
Quote:
Originally Posted by PrimeTime

AVRs are remarkable, really. Brought pro bi-amping (spectrum splitting) to the masses, just for starters.
Quote:
Originally Posted by DonH50

Uh, no... I have never installed, run,or even seen a pro system that does passive bi-amping.

He's referring to an AVR's capability to digitally high-pass a speaker channel prior to amplifiction and digitally low-pass the subwoofer material prior to the sub's amp.
Quote:
Originally Posted by arnyk

Amir, can't you be straight with us just once?

Just lately you were asking trick questions about DC impedance which is an oxymoron, and now it turns out you have been basing your clipping experiments on an amp that has very atypical clipping?
What are you talking about Arny? I said I tested three AVRs. The first one I post was a Yamaha which has the typical class AB amp. This pioneer is a digital amp. Pioneer Elite is a very popular brand of AVRs. So if you want to exclude that from your assumptions, this is your chance to do so . I also tested the Onkyo which is also a traditional class AB amplifier. These are the three AVRs that were on my bench to test with and represent some of the most popular brands of AVRs. If this is not being straight with you, what is?

BTW, I will come back to your DC comment later.
Quote:
Originally Posted by DonH50

I don't think this has ever been debated in these threads, the argument is always about the audible impact of the reduced power demand for out-of-band frequencies when the voltages at the terminals of the two amp channels remain the same. We're back to if current clipping dominates, passive bi-amping can help; if voltage clipping dominates, it won't. So far evidence I have seen and IME leads to gaining maybe 1 - 2 dB at clipping for a passively-bi-amped system. That looks significant but is a pretty small increase in volume and that is at clipping where most systems are already pretty durn loud.

But the purported theoretical benefit is not about audibility OR increasing output.
Quote:
Originally Posted by DonH50

My old analog signal generator is buried in the basement someplace, and I can generate the file far quicker on my PC (seconds) than finding it, making sure it still works, getting a 'scope so I can measure the amount of clipping for a controlled study, then getting an ADC and PC hooked up to create the wave files so I could post them.

Ditto.

My analog signal generators (I had 2 for doing IM testing with arbitrary frequencies), despite being heavily modified for low distortion and amplitude stability are still one or more magnitudes dirtier than what I can do almost instantly on a PC with even the simplist audio editing software.

Furthermore, who knows what kind of power amp I might have dredged up? We expect clean clipping because we are used to good conventioinal amplifiers, but look at what Amir got snookered into!
Quote:
This was not for myself, remember, it was to give others a chance to hear it in a controlled way.

There's another good point. When the goal is delivering a sound or test signal over the web or for use by someone else on their system, anything you do in the analog domain has to be digitized. Plan B is to simply start out in the digital domain. The digital domain is the only place in the real world where you can have any confidence of the expected accuracy perchance you want to do things with 24 bit or better accuracy.
Quote:
I was also doing spectral analysis and do not have an analog spectrum analyzer at home, and in any event this was a trivial exercise whilst I was working on something else. Since I already had all the functions in place, it took far less time than posting about it.

Right, in the PC world excellent FFTs are freeware.
By the way, here is the extreme clipping point for the Onkyo. Take a look at the shape of that clipping:

Compare that to the ideal clipping as simulated by Don in the WBF article (top graph):

I hope you agree there is more to this story than understanding voltage limited clipping .

Note how the woofer output (yellow) is smaller than the tweeter even way, way past the threshold of clipping for both channels. It is not a lot and is not the point I will be making later. I mention it to make sure we understand that ideal amplifier parameters do not hold in real devices.
Quote:

Quote:
Originally Posted by DonH50

I don't think this has ever been debated in these threads, the argument is always about the audible impact of the reduced power demand for out-of-band frequencies when the voltages at the terminals of the two amp channels remain the same. We're back to if current clipping dominates, passive bi-amping can help; if voltage clipping dominates, it won't. So far evidence I have seen and IME leads to gaining maybe 1 - 2 dB at clipping for a passively-bi-amped system. That looks significant but is a pretty small increase in volume and that is at clipping where most systems are already pretty durn loud.

But the purported theoretical benefit is not about audibility OR increasing output.

Where was this discussion limited to purely theoretical benefts in say the sixth decimal place?

Where did the stated goal stop being increasing output or reducing audible distortion when an amp runs out of power?

http://www.anthemav.com/support/faq.php

"If one amp starts running out of power, usually the one driving the woofer, then the other side remains clean instead of becoming part of the problem, a double-win."
Quote:
Originally Posted by arnyk

Where was this discussion limited to purely theoretical benefts in say the sixth decimal place?

Where did the stated goal stop being increasing output or reducing audible distortion when an amp runs out of power?

http://www.anthemav.com/support/faq.php

"If one amp starts running out of power, usually the one driving the woofer, then the other side remains clean instead of becoming part of the problem, a double-win."

Because the only real practical benefit (if there is one) I see is the tweeter isolation. Sure, there may be an audible improvement in your system's performance when you are operating right at the clipping threshhold, but who is really looking for THAT as a specific benefit?

"I want to operate my system so loudly that it is audibly clipping so I am going to passively biamp for the extra 1-2dB before that happens."

And, honestly, I think that the tweeter protection, although potentially there, is probably overstated. Most people who are apt to blow their tweeter are probably going to blow it no matter how they are wired.
Catching up on some posts in the parallel thread:
Quote:
Originally Posted by arnyk

The very simple clipping indicator that QSC uses in their amps starts lighting up the clipping LED around 0.01-0.02% if you are testing with sine waves.

The clip detector/indicator is composed of B1, LD2 and adjusted with TR2. There might be \$1 worth of parts at single-piece prices.
That is not a clipping detector Arny. Look at where it is placed: right after the NE5532 op amp. This is the front-end of the amp, not the power output stage where clipping will occur. The final output stage is the paralleled pair of 2SD424 and the complementary pair above it. The output of those transistors just goes to the speaker terminal and that is that. Here is the larger view of the amplifier circuit:

So what does that circuit do anyway? It is a simple full-wave rectifier that takes the AC output of the amplifier front-end, and converts it to positive waveform. This is a picture of what it does to a simple sine wave (on the bottom):

That in turn drives an LED. In other words, that is a little power supply that attempts to convert AC to DC to drive the LED. I say attempts because the bottom waveform is not DC. Normally there would be a capacitor that would fill in the gaps but it is missing here. The threshold of when the LED is turning on is set as you state. But what it is measuring is the output of the front-end of the amplifier and not the business end we care about (what feeds the speaker). Because the final (and driver) stage use variable voltages for their supplies, you cannot predict at what level they will clip based on their input level. That point is frequency and voltage dependent. So at best this will be a guess, a prediction, of clipping may be occurring. Proper clipping circuit would monitor the output of the amp, not the feed into it.

That's not all that is wrong with it though. When the op amp gets to the level that would light that LED, there would be a fair amount of current used up by that LED. The op amp used to drive it is a little part without much current ability of its own. If you burden its output to light up an LED, it is liable to distort the audio waveform coming out of it. In other words, this circuit will create distortion of its own as you increase the volume! And will make clipping worse where both the front end and final stage are getting distorted.

Proper clipping detectors start by buffering their inputs so that they put almost no load on the driving circuit. They then use voltage comparators to detect whether clipping has occurred. That takes 15 to 20 parts and cost more than a few cents by the time you include the cost of PCB, assembly/test, etc. The Bryston has that circuit if you are curious how it is done correctly.

I suspect these are the reasons QSC did away with this method. It was cheap, but not good! While not quite an "idiot light," one could call it that since it can light up when clipping has not happened or stay dark when it has. If you read the QSC manual you see that while they call this a clipping light, the usage they have for it is not at all to indicate the output has clipped.. But rather, it is to tell you if the front end of the amp has clipped. Which is what it kind of does.
Quote:
Originally Posted by amirm

Catching up on some posts in the parallel thread:

I suspect these are the reasons QSC did away with this method. It was cheap, but not good! While not quite an "idiot light," one could call it that since it can light up when clipping has not happened or stay dark when it has. If you read the QSC manual you see that while they call this a clipping light, the usage they have for it is not at all to indicate the output has clipped.. But rather, it is to tell you if the front end of the amp has clipped. Which is what it kind of does.

Wrong again Amir.

QSC didn't do away with this method - it is still used in current production amps such as the RMX 1450.

What your superficial analysis has failed to take into account is the fact that QSC's clipping indicator is inside the amp's feedback loop and only sees large voltages when the output stage is saturated.

It is true that there is no capacitor to act as a pulse stretcher or filter, and that is because the indicator is highly effective without it.

It's pretty amazing to see this light flickering on when the THD is well under 0.05%, but that's what happens.
I think I found the perfect amp. Lexicon LX-5. 5x200w and bridgeable, so I think can do 2x400 for my FL & FR, and 1x200 for the centre. That should be plenty of power, no? And about 50lbs. All for \$1000!.... but it sold so fast I didn't get it in time... I'll keep looking
Thanks for the kind words guys! I am still a tyro in audio compared to some of the experts on AVS.

Amir, can you have the DSO generate a spectrum of the clipped waveforms? Those are _very_ heavily clipped! Still, not a large difference in actual output power between the loaded and unloaded cases, about 10%?

Arny, is it possible peaks are nearing clipping even though THD remains low? More likely just margin for component tolerances in the circuit, I suppose... Seems unlikely if you are measuring 0.05% THD that the amp is anywhere close to clipping, though SINAD does tend to peak right before the amp goes over the clipping cliff.
Quote:
Originally Posted by stereoforsale

I think I found the perfect amp. Lexicon LX-5. 5x200w and bridgeable, so I think can do 2x400 for my FL & FR, and 1x200 for the centre. That should be plenty of power, no? And about 50lbs. All for \$1000!.... but it sold so fast I didn't get it in time... I'll keep looking

Theoretically bridging gets you 4x the power, but real-world amps very rarely achieve that.

An Emotiva XPA-3 gets you into that power range though not bridged, and I think they are on sale. For Watts/dollar it is hard to beat going the pro amp route, however. You can probably get that sort of power or more with a couple of amps for less money. Just have to watch the gain configuration (some may not play well with consumer equipment; most do OK) and fan noise (if the pro amp has a fan, many do).
Quote:
Originally Posted by DonH50

Quote:
Originally Posted by stereoforsale

I think I found the perfect amp. Lexicon LX-5. 5x200w and bridgeable, so I think can do 2x400 for my FL & FR, and 1x200 for the centre. That should be plenty of power, no? And about 50lbs. All for \$1000!.... but it sold so fast I didn't get it in time... I'll keep looking

Theoretically bridging gets you 4x the power, but real-world amps very rarely achieve that.

An Emotiva XPA-3 gets you into that power range though not bridged, and I think they are on sale. For Watts/dollar it is hard to beat going the pro amp route, however. You can probably get that sort of power or more with a couple of amps for less money. Just have to watch the gain configuration (some may not play well with consumer equipment; most do OK) and fan noise (if the pro amp has a fan, many do).

I have two Crown XLS1500 amps, got them for just under \$700 delivered for a pair. I've yet to hear the fans even after a couple of movies at high volume (but do use active subs). Plays nice with my Onkyo avr pre-outs. Did have to cover the bright blue led window after getting it setup. Together they weigh less than 25lbs. Specs:

XLS 1500 *1 kHz
Power
2Ω Dual (per channel) 775W
4Ω Dual (per channel) 525W
8Ω Dual (per channel) 300W
8Ω Bridge 1,050W
4Ω Bridge 1,550W
*Maximum average power in watts at
0.5% THD, 1 kHz.
XLS 2000 *1 kHz
Quote:
Originally Posted by DonH50

Theoretically bridging gets you 4x the power, but real-world amps very rarely achieve that.

An Emotiva XPA-3 gets you into that power range though not bridged, and I think they are on sale. For Watts/dollar it is hard to beat going the pro amp route, however. You can probably get that sort of power or more with a couple of amps for less money. Just have to watch the gain configuration (some may not play well with consumer equipment; most do OK) and fan noise (if the pro amp has a fan, many do).

Thanks for the tip Don. Will 200wpc be enough? Or should I be looking at 300w-400w? If so, the +300w Emotivas are way too big/heavy for me.

But, yes, their prices are unbeatable. XPA-3 = US\$719 right now... would be well over CDN\$1000 once you ship into Canada, but still a good value. Bit heavier than Lexicon, but not by much. The Lex was like \$6000 retail... \$1000 used was a steal... good ones go fast!
Quote:
Originally Posted by stereoforsale

Thanks for the tip Don. Will 200wpc be enough? Or should I be looking at 300w-400w? If so, the +300w Emotivas are way too big/heavy for me.

But, yes, their prices are unbeatable. XPA-3 = US\$719 right now... would be well over CDN\$1000 once you ship into Canada, but still a good value. Bit heavier than Lexicon, but not by much. The Lex was like \$6000 retail... \$1000 used was a steal... good ones go fast!

Without searching too much what speakers are you using? Seriously consider those Crowns I mentioned, even in Canada I'd assume there's decent availability even if not at the price I paid....
Having skimmed through the past ??? posts, I'm left with the same conclusion at entry in the conversation: inaudible benefit when biamping.

Learned:
- speaker crossovers prohibit outband signal amperage draw with high impedance
- the inband freq may gain a relatively audibly unnoticeable amount of amps
- male virility can be increased by biamping, but viagra is superior
- engineers are quite chatty about the topic
- the nation's poverty rate is unaffected by biamping
Quote:
Originally Posted by UndersAVS

Having skimmed through the past ??? posts, I'm left with the same conclusion at entry in the conversation: inaudible benefit when biamping.

Learned:
- speaker crossovers prohibit outband signal amperage draw with high impedance
- the inband freq may gain a relatively audibly unnoticeable amount of amps
- male virility can be increased by biamping, but viagra is superior
- engineers are quite chatty about the topic
- the nation's poverty rate is unaffected by biamping

Viagra? What, not smilin' Bob and his non-prescription Enzyte? Seems he's the better rep for passive bi-amping somehow.....

PS never mind, getting mixed up with impedance and impotence, gettin' old is a bitch.
Quote:
Originally Posted by lovinthehd

Without searching too much what speakers are you using? Seriously consider those Crowns I mentioned, even in Canada I'd assume there's decent availability even if not at the price I paid....

Ok will do. B&W Matrix 803. 8 ohm (minimum 3.7 ohm). Sensitivity 90dB spl (2.83V 1m). Power handling 50w-250w into 8 ohms unclipped.

Just bought Marantz sr7008 with the original intention of biamping (that's why I'm here!) but I also knew that it gave me the option to add an external amp if need be. I'm just concerned that with 9 speakers hooked up to the AVR, the power to the L&R speakers will be under a lot of strain. I have another amp I can use to power the height or rear speakers to take some of the strain off the AVR, but elsewhere I've been told that doing so won't free up any meaningful power. AVR is rated at 125w x 2ch driven... but there is no mention of the power with all channels driven, but I suspect it's well below 100w, perhaps even below 80w... yikes, that seems like too little... but I'm gathering that it may only mean a ~2db drop in max volume, which is actually very little.
Quote:
Originally Posted by DonH50

Arny, is it possible peaks are nearing clipping even though THD remains low? More likely just margin for component tolerances in the circuit, I suppose... Seems unlikely if you are measuring 0.05% THD that the amp is anywhere close to clipping, though SINAD does tend to peak right before the amp goes over the clipping cliff.

As long as the peaks are below clipping the THD of most good modern SS amps will be low - below 0.01-0.05%.

IME if you have sensitive means for detecting clipping that SNAD rise is due to small amounts of clipping.

The most significant determiner of the exact point of clipping all other things being equal, is the turns ratio with minor contributions by other losses in the power transformer. If the windings vary in terms of how tightly they are wound the turns ratio can change a little.
So if they have sensitivity of 90db for 1w/1m, at 93 db you need 2w, 96 db 4w, 99 db 8w, 102 db 16w, 105 db 32 w, 108 db 64w, 111 db 128w, 114 db 256w (all considering 1m distance) So pretty dang loud with 111db with 3db headroom for that 250w handling level they spec.....are you sure your speakers can handle that kind of output let alone your ears?
Quote:
Originally Posted by stereoforsale

Quote:
Originally Posted by lovinthehd

Without searching too much what speakers are you using? Seriously consider those Crowns I mentioned, even in Canada I'd assume there's decent availability even if not at the price I paid....

Ok will do. B&W Matrix 803. 8 ohm (minimum 3.7 ohm). Sensitivity 90dB spl (2.83V 1m). Power handling 50w-250w into 8 ohms unclipped.

Just bought Marantz sr7008 with the original intention of biamping (that's why I'm here!) but I also knew that it gave me the option to add an external amp if need be. I'm just concerned that with 9 speakers hooked up to the AVR, the power to the L&R speakers will be under a lot of strain. I have another amp I can use to power the height or rear speakers to take some of the strain off the AVR, but elsewhere I've been told that doing so won't free up any meaningful power. AVR is rated at 125w x 2ch driven... but there is no mention of the power with all channels driven, but I suspect it's well below 100w, perhaps even below 80w... yikes, that seems like too little... but I'm gathering that it may only mean a ~2db drop in max volume, which is actually very little.

The load on the AVR's power supply in actual use is always far less than bench tests, because music has a much higher crest factor than pure steady sine waves used for bench testing.

Another signficiant factor is that the tracks in a multichannel recording are obviously not identical, since they would be duplicate mono tracks if they were identical.

I've been analyzing multichannel recordings and find that generally the L&R tracks are the loudest, and most other tracks are a few dB softer, often with one or more tracks being very soft.

So, any test that presumes that all channels have the same peak level is also not proving to be representative of actual use..
Quote:
Originally Posted by lovinthehd

So if they have sensitivity of 90db for 1w/1m, at 93 db you need 2w, 96 db 4w, 99 db 8w, 102 db 16w, 105 db 32 w, 108 db 64w, 111 db 128w, 114 db 256w (all considering 1m distance) So pretty dang loud with 111db with 3db headroom for that 250w handling level they spec.....are you sure your speakers can handle that kind of output let alone your ears?

Can they handle what kind of power? The power of my AVR, which is rated at 125wpc with 2 ch driven? Or do you mean the 200w Emotiva, or the 400w bridged Lexicon?

At then end of the day, my understanding is that more power is never a bad thing - you can never have too much power, no? You always read about amps being under powered and you need lots of microfarads (or whatever they are called) for dynamic movies, etc, etc. Hence people need (or are made to be believe they need) more and more power. Ultimately, my fear is that with all 9 channels driven, can the Marantz sr7008 produce enough clean power?

I take arnyk's point that power demands in real use are not as steady and demanding as in bench testing, but as a consumer we have nothing else to refer to. Then when you throw in things like "THX Ultra 2 certification", and it makes you think "gee, my AVR is not THX certified so I'm already on thin ice to begin with!". All of this makes you want to squeeze out every bit of performance we can get, especially if it's as easy as simply using the biamping feature you already have access to (this is why the "waste of time & money" arguments against passive bi-amping meant nothing to me... it cost me nothing to do it, I just have to move from 9.1 to 7.1... and frankly, 9.1 has proven to be a much bigger "waste of time and money" in my opinion... I wasted considerable time and money setting up those last 2 useless speakers... but I digress).
Quote:
Originally Posted by arnyk

The approach to this problem described above seems to lack a solid technical base.

There was no objective determination of the problem or its cause.

When I'm chilling out listening to music late in the evening - that's not the time I start playing around with SPL metres and such.

Quote:
The statement

" I had to turn the volume up more yet it sounded like the whole system was getting quieter."

The above could be describing the ear's well known property called "Temporary Threshold Shift". Probably was.

You mean you have decided that that's what the problem was because it fits your angle better.

All I can describe it as, as it would start to sound very strangled and harsh and required more and more volume but still didn't sound full bodied from adding any extra volume.

Quote:
The idea of trying to address TTS with a 140 mm fan seems to lack insight.

It was worth a shot.

Quote:
Then we have the idea of addressing a perceived lack of power output of an AVR that might have been capable of 160 wpc by adding an 80 watt amplifer.

I already have some big old 150w ss poweramps lying around but I don't like their size and the space they take up and their inefficient power use (as they would be used all day long) and the audible transformer hum I could hear from the listening position. I had been using them in the past but went back to the AVR's amps for those reasons but then run into the problem mentioned above from doing so. Some nice small quiet efficient class-D amps appealed to me. I haven't experienced that strangled harshness since going back to outboard amps. The new amp would just gracefully shut itself off for a few seconds instead when I just had the one by itself.

Quote:
Finally, finding that downgrading the system with a lower power amp did not have the desired effect, a second 80 watt power amp was added using what is probably the least effective means for adding it.

As ultimately I am wanting to end up with an active bi-amp setup for my 2-ways - 4 amp channels will be needed. Getting the second one has also stopped any shutdowns since.
Quote:
Originally Posted by amirm

Ok, let's consider the tweeter with its simplest form of crossover, the first order 6 db/octave. In other words, the upper part of this schematic...
Better be careful! Start talking about LCR circuits and a lot of people for whom "LCR" has only one meaning will come flooding in with their non sequiturs...
Quote:
Originally Posted by stereoforsale

At then end of the day, my understanding is that more power is never a bad thing - you can never have too much power, no?
In the gearhead world there's a saying: "there's no substitute for cubic inches". To some extent that's true, although it's been updated to read "the only substitute for cubic inches is cubic dollars". We also have another less known saying: "I can build as much power as you want; how deep are your pockets?"

Speaking in practical terms is is possible to build a car with too much power, spinning its wheels madly at the slightest touch of the gas pedal. Likewise it's possible to have too much amplifier power. If you're spending big bucks on stuff like 30A outlets and electrical wiring that is typically found in factories, you might be going over the top. If you have to run the A/C in February in Minnesota because of the heat that your electronic gear produces, you might be over the top.

If you have "cubic dollars" to spend on total overkill, by all means go for it! Lord knows the home theater meme has been done to death; it would be refreshing to see a home concert hall, with stacks of Anvil cases and black everything. It's just important to realize that at some point you're spending money on latent power that can never actually be used, and could trash your speakers if you make one mistake.
New Posts  All Forums:Forum Nav:
Return Home
Back to Forum: Audio theory, Setup and Chat