For better or worse: 2xRB1070 or 1xRB1080

[Boombox]

I've been considering adding another RB1070 to my hi-fi as opposed to upgrading to a RB1080...
I have Boston Acoustic VR2 floorstanders at present rated at 200Watts running off a RB1070 @ 4ohm (bi-wired).

This what I can conclude...

Keep in mind that my subjective evaluation is based on Boston providing
a speaker with an ideal 8W (W=ohm) or 4W load (all things being equal
inside the cabinet)...

Reason:
"...The damping factor indicates the ability of an amplifier to resist a
change in it's output signal..."
That said, the higher the damping factor (DF) the better the amp tells
the speaker what to do...i.e. who's boss...!!!

From the starting blocks, this will mean the RB1080 (DF = 1000) is far
ahead of the RB1070 (DF = 500) (1-0). Also, 200Watts for the 1080 and
130Watts for the 1070 (2-0).

8W load: Using a normal 16 gauge speaker wire for both set-ups and an
average "speaker wire" length of 3 meters, the DF at the speaker
terminals results in 250 (75% loss) for the 1080 and 200 (60% loss) for
the 1070 . However, its still 250 compared to 200 (3-0). In terms of
wattage, the 1080 delivers a huge 198.8Watts to the speaker whereas the
1070 only manages 129.2Watts (4-0). That said, this results in 0.60%
loss of power for the 1080, but the 1070 only losses 0.62% of its
power...hmmm...close.......still, we can't forget the 198.8Watts at the
VR2's doorstep!!!....so...I guess it's 4-0 in favour of the 1080...!!

4W: Here the 1070 delivers 160Watts and 98.8% of this power reaches the
speaker, i.e. 158.13Watts. Furthermore, the DF lowers to 125 which is
not a good sign..?!! The 1080 delivers approx. 240Watts in a 4W
load...237.16Watts reach the speaker...almost 80Watts more than the
1070, but here too the DF reduces to 142.86. This means that the 1070
losses 37.5% (from 200 to 125) of its DF as compared to a 43.2% drop for
the 1080 in DF...(5-1), but who cares...237Watts is still alot (6-1).
KNOCK-OUT!!! And now the 10 count starts....can the 1070 pick itself
up..??

1: The 1080 is only stable into 4W and 8W, and so too the 1070...
2: The 1070 is bridged....330Watts...; the 1080 cannot be bridged..(6-2)
3: Its DF rises back to 200, but its only stable into a 8W load...(7-3)
4: The 1070 delivers a monstrous 328.06Watts to the VR2...(7-4)...
5: If we shorten the speaker wire to 2meters so that the speaker is on
average 3m away from the pre-amp, then the DF climbs to 250 (7-5)...
6: The wattage increases to 328.7Watts (7-6).
7: 2x1070 is R100 (17US$) less than the 1080...(7-7)...ok...maybe this one is on
the fringes of prejudice (and so is count 6)....HOWEVER......the 1070 is
UP!!!! :T

Ok...who wins...well which one will cost you less to run....In idle mode
the 1070 consumes 50Watts of power which means 100Watts of power is
consumed when idle for the two amps..The 1080 also consumes 100Watts of
power so its still (7-7)...

Sooooo....in the highly unlikely event of a blown fuse or a
reconditioning of the amp, then, the 1080 system is completely down,
whereas the one 1070 can be reconfigured to run in stereo mode and still
deliver either 130Watts into 8W or 160Watts into 4W and there is
effectively no down time, while the other 1070 is being repaired!!

7-8 in favour of the 1070...!!!! And that's that!!!

Conclusion:
Having done this analysis, one question remains...will there be an
AUDIBLE difference?????? Won't know, can't tell, will have to find
out...
Gut feeling: No audible difference!!! Audible differences only
results when the DF drops to below 10..!!!! So does the DF really
matter?

Also, what good is it to have so much power with little control...?? But
still, just knowing of how much power is available can lead to a
prejudiced and subjective opinion of resultant audio quality....!!

Some interesting links on my "research"...
Quick short calculatory facts, with examples...

http://www.trueaudio.com/post_013.htm

Damping factor calculator depending on speaker wire...

http://www.bcae1.com/dampfact.htm

Audible differences....in damping factors....

http://www.audioholics.com/techtips/audioprinciples/amplifiers/dampingfactor.php

[Boombox]

Forgot to mention....theoretically, the higher the damping factor, the better....

[UCLAman]

explaination please

[QUOTE=Boombox]I have Boston Acoustic VR2 floorstanders at present rated at 200Watts running off a RB1070 @ 4ohm (bi-wired).
QUOTE]

Please explain how this is done. Sorry I am sort of a newbie. I am trying to understand how an 8 ohm speaker goes to a 4 ohm?

The RB1070 is 2 x 130 watts and
so because your VR2s are biwired, that makes them 4 ohm?

Please explain this part. Thanks

So what you are asking to do is get a second amp, the 1070, so that esentially each speaker gets its own amp. 130 watts for the highs and mids and 130 watts for the lows for each speaker.

OR Use only 1 1080 (2 x 200 watts) and biwire the speakers. This would only give you 200 watts per speaker. As opposed to the 2 1070s which would give you 260 watts per speaker.

And your conclusion is that 2 1070s are better than 1 1080?

No kidding?!

[miner]

Boomer,
If you decide to sell your RB-1070 let me know.

Miner

[thyname]

Boombox, with all that research and thinking, I don't believe somebody can give your a better answer than yourself...

[Zoran]

I strongly recommend considering of the biggest RB-1090. Superior soundvise vs RB-1080. Never tried smaller RB-1070, but can forsee the outcom, especailly if electronic issues on the table.

Twice more money, but RB-1090 remains Rotel's statemant amp IMO...

[NonSense]

Boombox

You should do a search on this topic because it has been discussed several times, and you should be able to extract all the information that you are looking for from those threads.

In short, with all things being equal (mainly the manufacturer), a single 200W 2Ch amplifier should outperform 2x 130W 2CH amplifiers in a non active cross over, standard bi-wire, Bi-Amp configuration. With additional power reserves, the 200W will give you better driver control. Since you are comparing 2x130W to a 200W of the same manufacturer, the decision is easy if you leave you decision based on performance alone.

Lots of other factors may sway your decision, but 2x130W does not make 200W's of control (even though it translates to less than 3dB SPL difference) and there are several people on this forum that have made this comparasin and have chosen the 200W as superior.

[soundhound]

Well put NonSense, I was one who tried active bi-amping a pair of 1070's, and shorly after opted for the solo 1080, and was happy I had.

[chachi]

what about 2x bridged 1070s vs a 1080 ?

[Boombox]

Well chachi, that's what I plan to do....
Bridging the 1070s...this will theoretically give me 330Watts of power according to Rotel here..instead of bi-amping or bi-wiring. Each amp driving one channel. I still think it will outperform one 1080....

[Kevin D]

It's doubtful that two bridged 1070's would out perform a 1080 either. The 1080 outperforms the 1070, and not just because of power. There's the whole design of the amp you have to look at.

More importantly, the increase distortion (IE, decreased sound quality) you encounter anytime you bridge an amp will certainly push the 1070 even futher away from the 1080 SQ wise.

Kevin D.

[Boombox]

Good point Kevin D....increased distortion....I haven't thought of that and will look into it....hmmm....

This discussion is almost like that of the girlfriend that cheated on you and you are trying to convinve yourself to take her back, but all your buddies are advising you to run away from here...!!!

[miner]

Negative; 'my' cheating girlfriend you can have but leave my Rotel amp alone.