help please with 802 D

[zork]

HELP PLEASE WITH B&W 802D
« on: Today at 08:22:44 am »

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hi
i ve got at the moment
rotel 1069 processor
rotel 1095 amp
b&w 683
B&w 600 center
b&w small surrounds
2x 500 infinity subs
hdmi projector
hdmi pvr
ps3 as blue ray

i am looking at buying 802 d for my mains,then moving my 683 back as surrounds
will my rotel setup be enough to power the 802 d
will this setup work.
any advice would be appreciated please!!!

[htsteve]

zork,

You have a nice system. And are considering a very nice upgrade.

The 1095 will drive the 802d's (and your system) fairly well. However, the more powerful amp that is used (one with more current delivery), the better the performance will be on the 802D's. Accross the board improvement: soundstage, dynamics, detial, depth, low level listening, bass quality, etc. I went from a 200 watt 5 channel amp to a 250 watt stereo amp (definite improvement) to my current 400 watt stereo amp (awesome performance).

Stereo or monoblock amps are ultimately the best way to power 802D's. In the Rotel family, look at the 1092 (500 watts X2) or a pair of 1091's (500 monoblocks). Also, the 1090 (380 X2) is also nice, although those are a bit harder to find. This way your system synergy remains intact (All Rotel) and you provide serious current to the 802D's.

Also, a down the road item would be to upgrade the center channel. The 600 will be left behind in the new system with 802D's up front and 683's in the back.


A different topic to consider is acoustic treatments. You can improve the sound of any system with some treatments. Bass traps, first point reflections, etc.


Hope this helps.

[scanido]

Generally those speakers would need more power to be at their best and yes, your 1095 would "work". But depending on your room size and acoustic treatment, it may well be satisfactory to you.

I myself will be running my new 802Di's off of a Mac MC205 for the time being as my room is small ( 18' x 13') . That amp has some grunt so we'll see how it goes and enjoy the slow upgrade path. At the end though i see them being run off some nice mono blocks ie (MC601)!

[mjb]

No offense to anyone, but it does annoy me to keep reading how 802D's NEED so much POWER, its simply not true. They may prefer more, but they don't need it.

A good example is here: a 70 watt tube amp (Octave RE 280MkII) driving 800D's, and I bet it sounds really sweet!

http://www.htguide.com/forum/showpost.php4?p=523467&postcount=3566

It is entirely feasible to upgrade to 802D's, and drive them with a Rotel 1095. Sooner or later upgraditus will strike again, and you can consider a more powerful or refined amp for your left/right speakers, or upgrading the center... or what ever. It is often recommended to spend more on the speakers than the amp, as the speakers will make a much bigger difference.

Upgrading is part of the pleasure of this hobby, we don't all start out with killer systems!

[ninja12]

Congrats on getting the 802Ds. :T If I were you, I wouldn't worry about a new amp at the moment. The 1095 should be able to hold you over for now. I think the next thing you want to look into is the getting a matching center channel for the 802Ds which would be either the HTM2D or the HTM1D. However, they don't make the HTM1D anymore; but, maybe, you can find a used one. After that, you should look into room treatments if your room is not treated. Actually, you can look into room treatments before you get the center channel. The biggest improvement you can make to your room is with room treatments. You will get more from room treatments than you would an amp. No electronics in the world can fix a room. Now, for the amp, I said you can hold off because the 1095 is 5 x 200. The 802Ds are efficient speakers. I believe they are 90 db. For example, if you set 12' away from the 802Ds, and fed it 10 watts of power, it would produce 85 db at your LP which means you are not taxing your amp at all, and 85 db is pretty loud. So, that's why I say you can hold off on the amp. I am not saying you shouldn't upgrade to a different amp. If that's what you really want to do, then you should do it. I'm just saying that upgrading to a different amp should not be that high on your priority list.

Now, if you want to listen at reference level of 105 db, then the 1095 will not cut it. You will need 1010 watts of power to produce 105 db if you sit 12' away from your speakers. If you sit 9' away from your speakers, you will need 568 watts of power to listen at reference level. So, what you really need to decide is what SPL do you want to listen at based on how far you sit from your speakers. That will tell you what kind of amp you should really get.

Anyway, congrats again, and I hope you enjoy your new speakers. :T

[dukester]

If your priority is 2ch music, upgrade your amp as i think you'll appreciate the increased power controlling your woofers and enhancing your mids. If HT is your thing, get a new center channel (HTM2Di)...since once you get the 802Di's, the timbre mismatch will be very obvious...IMO. I either scenario, it's win win...enjoy the upgrades :T

[emig5m]

I would say definitely do the center channel before amp. Room treatments are also a must do before amp. In fact, the room I'm remodeling right now for my rig I don't even plan on putting my system in there before I do acoustic treatments....well depends on how long shipping of the panels are. : Maybe I should order my panels now since I plan on having the room done by the 30th.

[wettou]

Here we go What has the most effect on Sound if sit more than 6 feet away from your speakers!

1. Your ears and your mood

2. The room (including size, acoustics, materials, furniture, how many people are in the room)

3. The speakers

4. Amplifiers

5. Processor

6. Source

7. Cables

[emig5m]

Here we go What has the most effect on Sound if sit more than 6 feet away from your speakers!

1. Your ears and your mood

2. The room (including size, acoustics, materials, furniture, how many people are in the room)

3. The speakers

4. Amplifiers

5. Processor

6. Source

7. Cables

I agree with that list, but might want to add in Speaker & Listening Position.

[mjb]

I agree with that list, but might want to add in Speaker & Listening Position.

I agree with the list, and the order :T Listening position is really covered by 1.

[Antonkk]

No offense to anyone, but it does annoy me to keep reading how 802D's NEED so much POWER, its simply not true. They may prefer more, but they don't need it.

No they do. My 200 Watt Mcintosh 6900 sounds like crap driving them but maybe it's the autoformers.

[Cruxis]

Here we go What has the most effect on Sound if sit more than 6 feet away from your speakers!

1. Your ears and your mood

2. The room (including size, acoustics, materials, furniture, how many people are in the room)

3. The speakers

4. Amplifiers

5. Processor

6. Source

7. Cables

Might also want to include the source material (quality of recording)

[Skyblue]

Also, the noise from the neighbors and the color of your speakers.

[sg2]

Hi,

I am also rejecting the idea that a massive power amp is a must for the 80xD's: things are not as simple as "I don't need more power, because I don't listen that loud".

I will try to explain why as simply as possible.

Electrically speaking, a loudspeaker is not a resistive load for an amplifier, i.e. one that would respect Ohm's law where U (voltage) = R (resistance) x I (current).

Rather, a loudspeaker is what is called a "complex" or "reactive" load, where the various non-purely resistive components (filter capacitors, filter and transducer coil inductances) on the signal path introduce what is called a "delay" (i.e. a phase angle) into Ohm's law: the current is "happening" either "before" the voltage, or "after".

Those who don't want to pull more maths from old memories can skip the bulleted items below:

- "complex" is the real math term to refer to those non-scalar (but rather vector) numbers.

- The generalized Ohm's law can be written U = Z.I, where Z is not a basic scalar resistance value, but rather a "complex number" which denotes this current / voltage "delay" or “phase shift”.

- Z, a two-coordinate vector, is called the impedance (rather than the scalar resistance).

- Z's first coordinate, the "real" part, is the load's pure resistance

- Z's second coordinate, the "imaginary" part, is the load's pure reactive characteristic (the one which induces the phase shift)

- The current / voltage "delay" or “phase shift” value changes at each frequency. This is why the impedance of a speaker is generally plotted over the audio frequency spectrum.


All commercial speakers’ impedance is generally listed in Ohm, which does not make any sense, because it only reflects the purely resistive component of the actual speaker's impedance.

If you imagine an amp's P watt power characteristic as it's ability to deliver P (power) = U (voltage) x I (current) into a resistive load, then scaling up the power will only change the ability to listen louder.

But with reactive loads such as a speaker, it does not compute like this at all.

Given that the reactive part of the speaker's impedance induces a delay between voltage and current (in either direction; capacitive components eat current before building voltage, and selfique components do the opposite), the current which the amp has to deliver can increase when the voltage decreases or the opposite).

See it as if you were shaking a weight through a spring. As soon as the spring starts to play its elastic role, sometimes you'll be pulling up without any force, and sometimes you will be pushing down while the weight is going down even faster, creating additional drag down.

This is the key to understand that an amp's power does not tell anything with respect to its ability to drive a given speaker.


Now let's consider the 802D. Read this:

http://www.stereophile.com/content/bw-802d-loudspeaker-measurements

You will note this critical statement: "The B&W's impedance plot reveals [...] an awkward combination of 4 ohms and –50° electrical phase angle at 60Hz".

In layman's words, this means that in the mid-bass region, the speaker is an AWFUL load to the amp. Current peaks at almost zero voltage, with an apparent resistance (4 Ohm) which is half the advertised, nominal "impedance" of 8 Ohm.

All other commercial speakers have angle shift too (because of the intrinsic characteristics of their capacitors and coils), but -50° along with halving the apparent resistance is rather uncommon. Trust me, I've read a lot of such impedance plots


This has a consequence which is true at ANY listening level: if you want your amp to control the mid-bass, whatever the listening level, then your amp has to be able to deliver current at zero voltage. And this is not common to all amps. It generally denotes that the amp has a VERY low output impedance, along with some other dynamic characteristics.


In fact, when you read Stereophile's amp measurement plots, and associated comments about the amp's compatibility with "difficult" loads, you will see that most solid state amps are only moderately capable of this, even when delivering low power; and that almost no vacuum tube amp can do this either.


The consequence is, most amps will deliver a bloated / muddy mid-bass with 802D's, at any listening level, as this is not a matter of power, but rather a matter of being able to retain the current control when it becomes out of phase with the voltage.


So, the question to ask is not "is this amp powerful enough", because no one likely listens with more than a few watts of actual power flowing through. The question to ask is rather ‘is this amp able to deal with very reactive loads’, as this is required for controlled mid-bass with these particular speakers.


In order to generalize, you have to look at a speaker's impedance / frequency plot (including the phase angle), in order to see if this will be a problem or not, and in which frequency region. Some speakers exhibit a very reactive behaviour in the treble... Then you have to find an amp which has good reactive load handling capability in this region.

Another quintessential question to ponder is the amplifier’s “damping factor”.
Again, this notion is linked to the reactive nature of the speaker as a load. The current tries to flow back from the speaker to the amp, for example when a transducer’s cone is brought back to its zero displacement point by the suspension. In this case, the motion of the transducer’s voice coil around the magnet induces voltage into the coil, i.e. the opposite physics of the amp pushing the cone out.
The amplifier’s damping factor can be seen as its ability to swallow this current flow back. It is also linked to the amplifier’s own output impedance. A high damping factor says that the speaker’s current reflow (thus cone motion) will be well controlled, and a low damping factor says the opposite.
This has an audible influence, again lying in the notion of “the amp controlling the speaker”.

Typically, most well-designed solid state amps have a decent damping factor, while most tube amps do not. This is the very reason why tube amps are not well suited to control large cone speakers, typical of which are the 80xD’s.


Hoping this will be useful!

[ShadowZA]

... in the mid-bass region, the speaker is an AWFUL load to the amp. Current peaks at almost zero voltage, with an apparent resistance (4 Ohm) which is half the advertised, nominal "impedance" of 8 Ohm. ...

Thanks for your detailed explanation. Interesting stuff, Stéphane!

This is most likely the reason that my 802D's have never sounded as good as they do now that I'm driving them with a Krell EVO 403e. This beast seems to be able to deal with the 802D's reactive loads better than any amp which I've previously owned.

[Antonkk]

And I should once again state - stay away from Mcintosh!!! Autoformers KILL the sound with B&W 802Ds unless you go up to 400-500 Watts. The combo of 6900 and 802D is the worst sound I ever had and right now I'm thinking of selling the speakers since because of my ongoing divorce I cannot afford a serious amp upgrade.

[zork]

thanks for the advice
must it be a htm2 or will a htm4 center do the job

[sg2]

I'll make it short this time: a HTM2D will perfectly blend with 802D's, while a HTM4 will not (and by far).

[htsteve]

I'llmake t short this time: a HTM2D will perfectly blend with 802D's, while a HTM4 will not (and by far).

Zork, I agree with this. I does mean more money, but the synergy is excellent.

[dukester]

Curious, with a question to more experienced forum members: Considering the upgrades (802D and HTM2D) in this case, and relegating the 683's to the rear, will the 1095 be over-tasked (as enlightened by sg2)? Will the 1095 be capable of handling the "load" or will an amp upgrade become inevitable/unavoidable?

Antonkk, interesting thought on the autoformers...hope my combo is ok.

[zork]

i would like to knowv aswell

[bigburner]

Another quintessential question to ponder is the amplifier’s “damping factor”...
A high damping factor says that the speaker’s current reflow (thus cone motion) will be well controlled, and a low damping factor says the opposite.
This has an audible influence, again lying in the notion of “the amp controlling the speaker”.

The damping factor of the RMB-1095 (20-20,000 Hz, 8 ohms) is 400. Is that sufficient Stéphane or should Zork upgrade the engine for his 802Ds to the mighty RB-1080, which has a damping factor of 1000?

Nigel.

[mjb]

Sg2, I agree totally and have tried to make this point (although not as eloquently) about the 802's before. The problem is solved not by using an amp with a higher theoretical output (at 8 ohms), rather one with a low to zero output impedance. For anyone who wants to google reactive load phase changes, the buzz word to remember is CIVIL: capacitive loads (C) current leads voltage, inductive loads (L) current lags voltage. With audio the frequency is obviously continuously changing, so speaker loads can be inherently compliicated. Again, which is not always solved by buying a bigger amp.

[emig5m]

Sounds like one of the old Sunfire amps might be good in this condition? What about say, the newer Emotiva mono blocks or their 3 or 5 channel amps? How would they work?

[sg2]

Hello all,

I see questions as to whether this or that amp would be suitable, both in this thread and in my private mails.

Without first hand experience (and I haven't got any with almost all the listed amps), it's only by looking at a comprehensive and standardized measurement set that I would be able to answer; I know only one such database, which is the "measurement" pages of the Stereophile amp reviews.

Also, the reasoning is entirely different with class D amps, but I fail to understand how one may spend >$10K into speakers with high fidelity expectations, and feed them with amps which are totally unable to reproduce a 1 KHz square wave, and smear it into a garbled sinewave full of residual HF noise... How a violin may sound timbrally correct with current class D amps is beyond me (and I do have first hand experience with violin, which I hear live every afternoon when my daughter practices, as well as with class D amps which I have been listening to by curiosity).

[wettou]

Forget class D please

Class A or A/B is the way to go especially with 802D or 800Diamonds

[windshear]

"Stirring the pot" :P Gosh i didnt know we listen to square waves.

[sg2]

I'll make it long this time (to perfectly alternate long and short posts in a square wave pattern )

We don't listen to square waves... Or in fact we may, sometimes, without knowing

We listen to harmonic compositions, as any sound (or any signal) is a sum of sine waves, each with its frequency, amplitude and phase.

Each musical instrument has its own harmonic composition, from the simple (a flute emits a sum of only a few tones) to the complex (a violin or a harpsichord emit a very complex sum of tones).

In general, the more vibrating components in an instrument, the more complex its harmonic spectrum is. This is very logical, as each vibrating component will itself emit a fraction of those tones.

This harmonic spectrum, if considered including the phase notion, is what we may call an instrument's timbre.

The square wave is an infinite composition of sine waves; in other words, it is the most complete harmonic composition from a fundamental tone.

There is thusly a good interest in looking at a square wave reproduction from an amp: if it does not look like a square wave, then the amp simply cannot reproduce complex harmonic structures.

I did not randomly choose a 1 KHz square wave in my critic of class D, as 1 KHz is in the middle of the audio spectrum (seen from a logarithmic point of view, as it should), and it is a fundamental tone which most natural instruments will reproduce along with their upper, i.e. to 20 KHz (or lower) harmonic constructions.

Thus, looking at the reproduction of a 1 KHz square wave gives a VERY good hint at the capability of an amp to reproduce unaltered harmonic constructions of natural instruments.

If the amp is able to reproduce this square wave, then you may look further into other characteristics (as phase shift, ability to drive highly reactive loads, output impedance, damping factor, and negative effects of feedback etc.).

Look at Stereophile amp measurements:
- almost 100% of the classic solid state amps very accurately reproduce a 1 KHz square wave

- most of the tube amps show overshoot and rounded angles, which demonstrates in a single graph their inability to accurately carry a timbre construction. They may sound nice, but this is mostly due to the fact that the human hear likes the harmonic alteration that they do on the signal. Google for euphonism: nice but cannot pretend to being accurate.

- zero class D amp is able to show anything but noisy sine waves (or show me one !)

Don't get me wrong, my ears are the judge at the end; yet i won't bother listening to something which I know cannot be accurate, and this can be seen in many ways in measurements; harmonic fidelity would rank at the top of my criteria, and the amp's inability to be harmonic-accurate can be seen in a fraction of a second from its 1 KHz square wave graph.

On the same note, a 10 KHz square wave graph is somehow useless, as any upper harmonic of the fundamental 10 KHz sine tone except maybe for the first (20 KHz) will be outside of the audio band.

[leej]

Thanks Stéphane. I enjoyed reading your enlightening explanation of reactive loads, phase shift and impedance. Very interesting.

[wettou]

I'll make it long this time (to perfectly alternate long and short posts in a square wave pattern )

.....

Look at Stereophile amp measurements:
- almost 100% of the classic solid state amps very accurately reproduce a 1 KHz square wave

- most of the tube amps show overshoot and rounded angles, which demonstrates in a single graph their inability to accurately carry a timbre construction. They may sound nice, but this is mostly due to the fact that the human hear likes the harmonic alteration that they do on the signal. Google for euphonism: nice but cannot pretend to being accurate.

- zero class D amp is able to show anything but noisy sine waves (or show me one !)

On the same note, a 10 KHz square wave graph is somehow useless, as any upper harmonic of the fundamental 10 KHz sine tone except maybe for the first (20 KHz) will be outside of the audio band.

Engineer, mathematician! Thanks for the scientific explanation doc :T