Stick to RSX1065 or go to 1055/1075 separates?

[dirk67]

Hi BleakShore,

your german is very good for just one year of lessons. I find the price differences rather weird, in Germany the 1066 is less expensive, in the US the 1055... But given that, in the US it's certainly logical to hook the 1055 to a 1075.

Dirk

[NonSense]

Hello All

Looks like I may have been over zealous with my hypothesis on the poor efficiency of the 2 amplifier/Bi-Wire system with a passive network. But I still believe a significant amount of power is being wasted. (Thus making the active crossover/Bi-Amp still attractive, if only on a power efficiency basis, should the earlier proposed model prove true.)

My argument is as follows. Consider a basic, 2-pole LC (Inductor (L), Capacitor (C)) Low Pass Filter as the crossover network for a separated bass driver arrangement in your loudspeaker. Two reactive elements, giving two poles in the response when properly arranged. From some earlier info, we know that as the frequency increases, the inductor acts to block the signal, and the capacitor will more readily pass the signal. The arrangement should be that the inductor is placed in series with the positive terminal and the capacitor should be placed across the bass driver terminals, (which is across the +/- terminals) in a shunt configuration. We know that a single pole response is only 6dB/Octave, which is often not sufficient, and the second element is required to increase the high frequency roll-off. The second element, the capacitor, will act to short the high frequency energy around the bass driver element. Energy generated by the amplifier, but not blocked by the inductor. Since the bass driver element was not able to use this energy, I consider this lost. I wish I could include a crude bode plot to explain. Imagine we were to plot the separate response of the series inductor and the shunt capacitor. We would see that they would likely have differing 3dB points, but a similar roll-off characteristic following their 3db points (6db/Octave). Then plot the combined response, and compare (overlay) this response with the separate response of just the blocking inductor. Now lets highlight the region above the combined response, and below the separate inductor response. I propose that this area, represents the high frequency energy generated by the amplifier, not blocked by the inductor, but never reaches the driver element to be converted to sound. I would expect this to be lost power.

I have also tried to include a link to an actual crossover network, which gives us some real numbers to convince ourselves that what I propose may be true. (Ignoring a few additional elements, we essentially have a 2-pole network) The terminal K2 represents the bass driver terminals.

http://www.speakerbuilding.com/content/1104/figure8.jpg

An inductor of 3.9mH is placed in the series position as the blocking element. Using the impedance formula Z=jwL, (hope this is right?) and lets say a 5kHz tone (representing somewhere in the voice range). I calculate an equivalent impedance of approximately j120 Ohms. (10KHz giving j240+) Reasonably large when compared to the approx. 8 Ohms (effective impedance at 5KHz) of the other network which is usually placed in parallel at this frequency to draw most of this frequency’s power. But not so large when left alone and faced with the task of blocking this power generated by the amplifier. Not quite the brick wall we were hoping to see. We definitively see a conservation of power, but not an entire recovery of this power. Based on the alternative that most of this power would normally be sent to the other crossover network via the path of least resistance. (8 Ohms)

Once again, I concede that my earlier claims were proven greatly exaggerated. However, I still propose that passing the full audio spectrum to both amplifiers is not as efficient as passing only the pre-filtered audio bands to their respective amplifiers. I still think that a significant amount of energy can be recovered in the amplifier and put to better usage, somehow offering better acoustics.


True? I will likely never know!



<a href="http://www.speakerbuilding.com/content/1104/figure8.jpg" target="_blank">http://www.speakerbuilding.com/content/1104/figure8.jpg

[BleakShore]

Hi NonSense,

I totally agree with you, and we don't have to go to Bode plot to explain it. I know all about it but we can spare those who are not really interested in poles or zeros and such

I understand what you are saying perfectly. In one post, I was just trying to explain how crossover blocks or passes signal to guys that are not EE.

Yes, there is penalty to pay when you go to higher order network. I was "lumping" it as the "insertion loss" in one of my previous posts. Probably around a dB or so, is what I guess. Please note that not all "unwanted" spectral power is lost as heat here. A significant chunk is first blocked by the inductor (so this "unwanted" spectral power is never lost), then the attenuated unwanted signal components that leak through the inductor will now be shunted through the capacitive path to the ground (this is lost power, a much smaller portion of the full unwanted spectra). For a higher order network, this process would repeat until a desired roll off slope is achieved.


I am not arguing the fact that external crossover before amplification is the way to go. Nor I am arguing that the use of internal crossover does not give you near the same performance as the axternal true biamping. Elliot made it clear, and I wholey agree.

True biamping with external crossover:

1. completely elliminates power loss introduced by the internal crossover,
2. does not suffer from nonlinear impedance of the speaker seen by the internal crossover, and
3, is the king of kings

I think we all agree on this point ?

However, what I was really trying to say in my original / early posts was that:

1. If you had extra amps lying around and
2. If you did not want to go inside the speakers due to warry reasons or just personal preferances (I like to keep what I buy as is. I will mod things that I make), and
3. If you did not want to spend the extra money/effort to buy/build the external crossovers,

then the use of the extra amps to drive you speakers gives you a quick and dirty way of delivering more power.

Of course, there will allways be the crossover network loss.
BUT the loss is there regardless you use two amps or a single amp as long as you use the internal crossover. This loss is inherent in the speaker as long as you use internal crossovers.


Pseudo BiAmping with Internal Crossover

1. Does it deliver 2x power for me?

Well, from a single amp, let's say the loss introduced by the crossover is 1 dB (translates to about 80% efficency). So 80% is delivered to the bass driver. Further, let's say that at 350 Hz crossover, power delivered to the bass and tweeter is 50/50. Then for a single 100W amp, the bass driver sees .5 x .8 x 100 = 40 Watts of power. The tweeter also sees 40 Watts of power. 10 W is lost as heat.

Now let's use a 100W amp dedicated to the bass driver, and another for the tweeter. The bass driver now sees .8 x 100 = 80 Watts of power. 20 W is wasted as heat.

But it's clear that we are in fact delivering twice as much power than before (80 W vs 40W, all things being equal)!. That's 3 dB gain. This is true, regardless of the crossover loss. That's what I was trying to say.

it is also clear that passing full spectral power to the speaker with internal network results in loss of power that is actually delivered to the speaker drivers.

With two amps, we can deliver twice (assuming 50/50 power split between the tweeter and woofer) as much power leading to much increased head room. This was the case with me .



Does it deliver 2x power for Mike Hayes?

Let's look at the case with Mike. His system is crossed at 3 kHz to 4 kHz. I forget, but let's say the power split is 80/20.

If he uses 1 100 W amp then the power delivered to woofer is (still assuming 80% efficiency of the crossover) .8 x .8 x 100 W = 64 W. The power delivered to the tweeter is .2 x .8 x 100 W = 16 W. Again total power used by the speaker is 80 W, and 20W is lost in the crossover.

Now if he uses two 100 W amps for the woofer and the tweeter, the power delivered to the woofer is .8 x 100 W = 80 W. As the power delivered to the tweeter will be proportional to 80 W, it is 16 W x 80 W / 60 W = 21.3 Watts. Power lost in the tweeter crossover is 5.3 W. Total power utilized by the speaker is 80 W + 21.3 W = 101.3 W. Total required amplifer power is 101.3 W + 25.3 W (insertion loss) = 126.6 W. He just needs a 100 W amp for the bass, and a 26.6 W amp for the highs. If he uses a 100 W amp for the tweeter, he is wasting roughly 73 Watts of power. It does not make sense for him. It would be much better for him to use a single powerful amp. Or use a powerful amp for the woofer, and a small one for the tweets.


Are we all on the same page ?
I think so. We are all trying to make oursleves clear, I imagine.

Regards,

[Jurgen]

I have been following the recent subject on bi amping on this forum (started by bleakshore) and although it’s difficult for me to comment on the technical aspect of bi amping, I certainly can throw my listening experiences in the mix. With the two rb1070’s and the speaker crossovers still intact, there is no reason for me to assume a second amp is a waste of money. I will however connect one amp and let you all know about the differences(which, based on my previous bi amping configuration, can be very dramatic).
Furthermore, I would definitely advise against the use of bridging an amplifier for hi fi purposes(I do use a bridged amp solely for a passive subwoofer). I have experimented with it and for me it was definitely a step backwards (compared with an ordinary Denon integrated amp I used at that time.)

The above quote is from subject Roteldebotel, but I thought I’d place it here since I have the feeling that I can contribute to this ongoing discussion about pseudo bi amping. Again: I can’t really comment one way or another on the technical analysis of bi amping(except for expressing my admiration). But I am strongly convinced that ears are more important than figures. And that means, with al respect, that I have to regard the fact that some people think(perhaps from a technical point of view)that the effects, when adding a second amp for pseudo bi amping purposes, are negligible, as utter BS.

Why? Because I’ve actually tried it(I’ve compared the two amps as announced in my quote). And anyone who thinks, by experience, that a second amp doesn’t contribute that much shouldn’t even consider upgrading to other components because that would surely mean that the limitations in hearing capabilities have been reached. Maybe I am reacting to strongly, but I can’t agree with the purpose of pseudo bi amping solely to prevent amps, that you have at your disposal, from doing nothing. It is a very legitimate and conscious choice to ad a second amp and the sound upgrade should immediately be noticeable.

Of course it means that I am curious to the improvement that can be made by external crossovers. But IMHO there is a night and day difference between a single amp and 2 amps and therefore should not be considered as a half, or second best, solution. (so bleakshore: be proud!!).

Jurgen

[BleakShore]

..I find the price differences rather weird, in Germany the 1066 is less expensive, in the US the 1055...

It sure is weird. Some kind of marketing thing. I heard that one reason is, in Europe, pre/pro's are sold a lot more than receivers. So price it lower to move more units. In the States, it's the other way around. We Americanos are lazy bums who prefer convenience over quality . So more receiver are sold at a cheaper price.

...But given that, in the US it's certainly logical to hook the 1055 to a 1075.

Well, at least it is not illogical, i like to think...

Regards,

"I'm pink, therefore I'm Spam"

[Mike Hayes]

Are we all on the same page ?
I think so. We are all trying to make oursleves clear, I imagine.

I am on the same page with you, Bleak For my purposes, either a small multichannel amp for the tweeters (perhaps an RMB1066 or maybe even a smaller multichannel amp) makes more sense than a second 1075. Also, I am kind of going back to my original thought of adding a 1080. It just makes more sense economically for me than selling the 1075 and going with a 1095. The only concern I would have about the 1080 combined with a 1075 would be the mismatched power capabilities of the 2 amps during either 5.1 or 7.1 applications. Do you have any idea how to figure out how loud the system would need to be for the speakers powered by the 1080 to somehow "sound louder" than the speakers powered by the 1075?

[BleakShore]

...Of course it means that I am curious to the improvement that can be made by external crossovers. But IMHO there is a night and day difference between a single amp and 2 amps and therefore should not be considered as a half, or second best, solution. (so bleakshore: be proud!!)....

Thanks jurgen. Another thing I noticed and felt I ought to mention is this. When I crank things up (and my B&W's will get loud, and take every Watt I can dish out to them ), the use of two amps will strain far far less. Basically you have improved the dynamic range (or head room) considerably.

With efficient speakers like Klipshes, this may be a moot point though..

Regards,

[NonSense]

I agree with you totally. In the end it's the sound quality that counts. I've heard 25Watt amps lay waste to cheap 100Watt amps, when it comes to reproducing silky smooth sound. It’s the application, not the numbers, and usually personal preference.

When on a level playing field (same wattage), surely two amps will perform better than one. However, Mike had spoke to his dealers and was being advised that 2x 120W amplifiers would deliver more power than 1x 200W.

Bleak, thanks. I do agree that you are getting the extra power benefit (sometimes it takes me awhile) I spoke with a couple of dealers yesterday about 2 1075s verses a single 1095 and both felt that they are nearly equivalent options with the 2 1075s holding a slight advantage powerwise.

Was this true? Was he actually getting more usable power? If sound quality was based solely on effective usable power (which it is not), which arrangement would offer Mike the most usable power. (The fact that the 200W amp can deliver all 200 Watts to either a high or a low should not be taken lightly vs. the 120W limit in the split arrangement) My argument was that 2x120W was not really 240Watts of effective useable power, due to the additional losses you have in the separated crossover configuration. Thus making Mike’s decision that much harder. Bleakshore has an easy decision. He owns all the amps. He even spent the time testing various arrangements to ensure the best possible settup to maximize sound quality for his tastes. No doubt an awesome sounding system.

But most of all, I’ve thoroughly enjoyed this discussion. Rarely get to talk the tech with others so enthused about audio.

Thanks!

[Jurgen]

Hi Bleakshore,

I agree with this your description: more headroom, reduced strain, better dynamics, the ability to go loud(wattage)…. But I feel I should mention some other sound differences (instead of: you are getting more from the same) which, btw, should also be beneficial for efficient speakers.

Perhaps we mean the same thing, but I would most definitely want to add higher resolution(the detail on offer is stunning!), stereo placement(there is much more a feeling of “being there”, the localisation of a drum set for instance, the breathing of a pianist player etc…) Please forgive me when I am being vague but your listening through your equipment instead of listening to. It’s like a curtain been pulled up in front of your equipment. "pant pant”… :crazy: I should stop before I’ll start tree hugging.

It’s just that there have been few changes in audio equipment that, for me, have been quite so dramatic as when I went from single to bi amping(except perhaps for putting the power plug in the socket). I think that this explains my fanaticism.

Regards,
Jurgen

[Jurgen]

Hi Nonsense,

Our replies crossed, needless to say I agree with you. And yes, this has been (and still is) a very interesting subject. Thank you Bleakshore!

Greets,
Jurgen

[Jurgen]

Double post, sorry :stupidpc:

[BleakShore]

...Do you have any idea how to figure out how loud the system would need to be for the speakers powered by the 1080 to somehow "sound louder" than the speakers powered by the 1075?

Hmm. Not quite sure what you mean here, but I will take a gander.

Let's look at your system:

1080 = 200 Wpch
1075 = 120 Wpch

N805 = 88 dB spl, 50W - 120W
HTM2 = 88 dB spl, 50 - 120W
DM601 = 88 dB spl, 25W - 100W

Case 1: Signals in all 5 channels contain acoustic programme at the same level in 5.1

As the sensitivity of all your speakers is the same, all speakers will reach their operating limit specified by B&W at the same time. This limit may have been imposed for the maximum distortion B&W wants to allow, or to protect the speakers from blowing up. Either case, when all speakers are blasting away at their peak capabilities, you will have heftier headroom of 80W for the fronts, and none for the center and surrounds. At this point, both the 1075 and speakers will add fair amount of distortions to the output for the center and surrounds. For the mains, 1080 should't even be breaking sweat, but 805 will be sweating (literaly from heat, I imagine ).

Case 2: Signals in the surround channels are much lower than the main and center channels

The effect would be much less so than the case 1. 1080, and 1075 for the surround is running cool. 805 and HTM2 sweating. 601 running cool.

Case 3: Signals in the center and surround channels are much lower than the main channe's

I think this is the most likely case for HT use. The reason I say that is in previous generation of AV receivers, it was not uncommon to see main channels delivering, say, 100W, but the center and surround channels would be rated at 60W or so.

I think the center channel is carrying mostly vocal signals for better voice localization, and the surrounds carry effects signals. Mains do most work.

1080 runs cool. 805 sweats.
1075 runs cool. HTM2 and 601 run cool.

If you crank the volume up such that the center and surround speakers are maxing out, I speculate that 1075 would run a bit less than maxed out (because only 3 channels are running, which provides a hefty relief on the power supply).

Assuming that the mains require about 60% more power (pulling this out of the sky, but loosely based on the older generation amp ratings of 100W for the main, and 60W for the center & surrounds),1080 would need to dish out 120 * 1.6 = 192 Watts, which is slightly less that its rated output. So is probably ok. This is nice because both the 1080 and 1075 are running near its maximum capacity at the same time. No wastage.

At this operating point though, your N805 would be throwing out some serious distortion. Perhaps die eventually. So if you begin hear N805 grunting, stop turning that knob :!: .

However,

Aside from all the power handling factors and speculations, I think adding the 1080 will give you cleaner sound in general because it is running well below its rated operating limits. There will be just that much lower distortions all around.

The center and surrounds will sound cleaner too, as 1075 is not powering the mains anymore, and there is that much less demand on the 1075's power supply. That translates increased dynamic headroom for the center and surround channels of 1075. The output transistors may get hot a bit, but hopefully, they can take the heat (no pun intended). But, there will be no distortion introduced due to the power supply running out of juice trying to cover all 5 channels.

I think getting a separate amp for the mains is always a good idea anyway, especially if you listen to music in 2ch a lot. So 1080 sounds good to me.

I apologize if I was tedious and long winded stating the obvious.
I get like that easily..

Regards,

[BleakShore]

Double post, sorry :stupidpc:

Ha ha ha... Pretty funny. *Much* better than my word description.

Oh, BTW, yes. I like the improvements in my system, just like you say. It's smooooth, open, detail, ..... Ahhh.

Sorry, had ta get mushy there a bit.

Cheers,

[BleakShore]

..However, Mike had spoke to his dealers and was being advised that 2x 120W amplifiers would deliver more power than 1x 200W.

Bleak, thanks. I do agree that you are getting the extra power benefit (sometimes it takes me awhile) I spoke with a couple of dealers yesterday about 2 1075s verses a single 1095 and both felt that they are nearly equivalent options with the 2 1075s holding a slight advantage powerwise.

Was this true? Was he actually getting more usable power?

No this is not true. Please see my recent post with Mike's system power analysis. I also address the inherent power loss in internal passive crossover there as well.

I guess, I kind of lost sight there for a while and fixated on just the power. No. Power is not everything, by far. It is the quality of the power, as you and jurgen timely pointed out. In the back of my mind, I was just thinking that we are all using Rotel amps which are pretty top notch , and are trying to make improvements on what's already excellent. What's better than excellent? Outstanding! (burrowing from the rating system of US of A gov't). So I figured the baseline quality was there to begin with, and I kind of lost sight amongst all the discussions.

But most of all, I’ve thoroughly enjoyed this discussion. Rarely get to talk the tech with others so enthused about audio.

Thanks!

Thank you, Mike, jurgen, and all others for healthy and very fun discussions! Afterall, that's what a hobby should be like. I have to admit though, I had no idea this thread would grow like this..

Cheers,

[espo]

I'm glad we all eventually came to the same conclusion. Yes I agree it was fun. :LOL:

I quote myself:
"Also if the 1xamp is the same power as the 2xamps combined, and the speakers are bi-wired, the larger amp should be much better, due to the increase in dynamics, soundstage, and openness usually associated with a larger amp."

[Jurgen]

cheers! :^x