Rotel RMB 1066 bridged with M&Ks?

AngelEyes

Distinguished Member
Hi Chaps,

I am considering getting a 1066 to go with my 1075 when I get some additional rear speakers.

I will use the 1075 for the 4 rear channels (4x120w) and planned to bridge the 1066 fo front duties (3x150w) which seems like a good way to go. (I will have one redundant channel on the 1075 but I can't see another eay to go giving me 3 front channels with more than 120w and still remain with Rotel; suggestions?)

Anyway the problem seems to be that when bridged the 1066 must have a minimum of 8ohms load (from the back panel drawing) and my fronts are M&K 850s rated at 4ohms...

Will I have to look elsewhere or are they just playing safe?
 
R

recruit

Guest
AngelEyes said:
Anyway the problem seems to be that when bridged the 1066 must have a minimum of 8ohms load (from the back panel drawing) and my fronts are M&K 850s rated at 4ohms...

Will I have to look elsewhere or are they just playing safe?

I would be cautious of running them with the 1066 it would more than likely clip and damage the speakers if pushed too hard :(
 

Steve.EX

Active Member
Rotel topology is such that in bridged mode the amp 'sees' half of the ctual speaker impedance. Hence when connecting a 4 ohm load the amp will see a nominal impedance of 2 ohms that will fluctuate dependant on usual program material and indeed drop way below 2 ohms? It is likely that your new 1066 will have a lifespan of about half an hour if you are lucky under these conditions.

It is generally accepted that bridging the vast majority of amps offers a degraded performance. Bi-amping would nearly always be my chosen route over bridging channels.

The 1066 is unlikely to be a match for the 1075 in absolute terms regardless.
Personally i would use the larger 1075 amp to drive the front 2 or 3 speakers (bi-amping if possible) and the lesser 1066 driving the rears every single day of the week.
 

joffy1780

Active Member
How about a 1070 (130x2) or 1080(200 x 2).You could use the 1070 for the back rears or the 1080 for the fronts.
 

AngelEyes

Distinguished Member
Thanks for feedback, I figured this would be the case. Shame as it sounded good in principal.

If any channel is going to have more power I want it to be the centre rather than the L&R which is why this option looked so appealing as the front 3 all would have more power... anyway if you can explain the basics of Bi-amping that would be great.

Thanks for the suggestions :)
 

inzaman

Moderator
AngelEyes said:
anyway if you can explain the basics of Bi-amping that would be great
Two amp channels will be driving one speaker, the signal going to the amp will have to be split to allow this.

Do the M&Ks have only one set of binding posts though?
 

Steve.EX

Active Member
Your speaker may have more than one pair of terminals on the back, 2 pairs is common 3 pairs are also found.
We will work on the basis that there are two pairs on the back of a speaker (2 red terminals and 2 black)
By offering 2 pairs of terminals on a speaker the internally mounted crossover is able to be split into 2, allowing high and low frequency drivers to fed by seperate channels of amplification.
Hence if you ran a single run of cable from a single channel of a power amp
to the speaker (+ and -) then the 2 red terminals would be linked together as would the 2 blacks.
If you were to feed that speaker with 2 channels of the power amp you would send one channel to one pair of terminals (often marked LF) and another channel to the 2nd pair of terminals (often marked HF) REMOVING THE LINKS BETWEEN THE 2 RED TERMINALS AND THE 2 BLACK TERMINALS
This in effect menas that the bass dirver is being fed by (i.e) a 100w channel and the mid/high drivers are being fed by another channel of 100w.

This has the combined effect of improving the dynamic response of the speaker as you have twice the power driving it and an additional 3db of headroom. It may also lead to a less compressed and more open and fluid presentation when playing demanding tracks as the amp will not be in such a hurry to wilt.
There can be complications and issues arising from crossovers etc but in most instances this can be considered as a good guideline.

From worst to best this is how i would rate powering a single speaker.

Single channel of average amp.

Bridging 2 channels of a moderate amp (i can see where this route may offer an improvement over the above, but i would generally turn my nose up at such an action)

Bi-amp with 2 channels of a moderate amp.

Single channel of a better amp.

Steven
 

Steve.EX

Active Member
Edited to include the BOLD
This is very important if you want to keep your multichannel power amplifier from suddenly exploding or (more commonly and much less dramatically) immediately shutting down and refusing to work.

Steven
 

AngelEyes

Distinguished Member
Looks like I need to find myself a 3 channel amp... some hope:rolleyes:, as the M&K850s don't support Bi-Amping and have a single set of binding posts. :(

I am not really in the position upgrade to a better 7 channel amp, I don't suppose that leaves me with many options other than those suggested by joffy?
 

Steve.EX

Active Member
If you have a Rotel fixation then the RB993 is not a bad unit for £300ish 2nd hand
3x200w THX
 

AngelEyes

Distinguished Member
Not really a fixation, I just like things to look the same if possible. I certainly welcome any alternative manufacturer suggestions :smashin:

Ideally I would like a neutral or warm sound as the M&Ks are brighter than I am used to. :)

Newbie with seperates :blush:

Thanks,

Adam
 

inzaman

Moderator
Why do you need three more channels? you have five with the 1075 so you only really need two. You could find a second hand 980, i have one biamping my front, this is 120 wpc and could be used for the front l/r with the 1075 driving the four rears and the centre.
 

inzaman

Moderator
Or i suppose to keep them looking consistent then the 1070 as joffy1780 mentioned above.
 

Steve.EX

Active Member
I believe the slightly cruder attitude of screw what they look like, will they drain the national grid when i turn them on is nearly always the best policy in matters of this circumstance. Honestly.
 

CYRUStheVIRUS

Active Member
I would try and use the same amp across the front three.
You can still bi-amp with one set of posts (just twist the cables together), that said i agree with Steve- A better amp is the best solution.
Rotel 993 for the front three is a good shout for reasonable money.

The columns are 8ohms by the way.:smashin:
 

AngelEyes

Distinguished Member
Thanks again for the feedback.

I really wanted a 3 channel amp because I want the front three to have more power than the rears if possible and not the other way round which would be the case if I opt for the 1070.... or as suggested using it for the L&R would leave the centre slightly down on power.

I have got it in my head (as a 90% movies viewer) that the front 3 should be powered the same and if anything the centre should have more power than the L&R which is what I would like in an ideal world. Am I barking up the wrong tree here?

Thanks for the tip on Bi-Amping with single posts, are there any rules on how to match amps etc. should they be identical? Can you Bi-amp one channel from a multi channel amp to a stereo or monoblock etc? I am quite curious about this yet unexplored route :)

Hi Cyrus, yeah I checked already ;) I'll be in touch early next week to meet up.
 

inzaman

Moderator
Steve.EX said:
I believe the slightly cruder attitude of screw what they look like, will they drain the national grid when i turn them on is nearly always the best policy in matters of this circumstance. Honestly.
:rotfl: :rotfl: :rotfl:


Personally for bi-amping i would go with the same amp per speaker(s). I tried to bi-amp my fronts with three channels from my receiver and three from a power amp but it just did not sound right. Either the treble was too harsh or the bass boomed, using the same power amp per speaker solved this problem.
 

booktrunk

Banned
I agree with what some of the others have said use the 1075 bi amped for the front three bi-amp the l&r with it,

and just use however many channels of the 1066 you need for the rears. Maybe use the other channels to power a second room?

Or just don't get or sell the 1066 and get something like an old 971 or rb03 power amp for the rears. Or two of them if 3 / 4 rears.
 

Hungry Horace

Novice Member
Or get another 1075 and bi-amp the center using one channel from each 1075 while driving the fronts with one of the 1075s, and the other for the rear speakers. The possibilities are endless :)
 

joffy1780

Active Member
Hungry Horace said:
Or get another 1075 and bi-amp the center using one channel from each 1075 while driving the fronts with one of the 1075s, and the other for the rear speakers. The possibilities are endless :)
With another 1075 you could bi-amp the front three and use the remaining four channels for the rears.Not cheap though :eek: .
 

AngelEyes

Distinguished Member
Interesting stuff, thanks guys.

I may have to stick with 5.1 for now until I decide the best way to procede. Out of interest, and forgive me if I am labouring the point, which is better a biamped setup or a similiarly priced single more powerful amp (given my speakers have single terminals).

I have to say this bi-amping with single terminals seems a bit 'wrong' in my mind and I am pretty sure the M&K manual says they can't be biamped... what are the pros and cons of single post bi-amping?

Thanks again.
 
R

recruit

Guest
Angeleyes - are you still finding the 850's too bright or have they settled down ?
 

AngelEyes

Distinguished Member
Sad thing is I haven't really listened to them since, certainly not for music anyway. Work is crazy right now :(

The 'AngelEyes destructa-room EQ process' starts on Wednesday hopefully, so with a completely redesigned and sealed room I can look at spending some time setting this up properly.

(I think/hope the echo inducing stairwell may be causing some of my high frequency issues)

I'll reserve comment on things until then.
 

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