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ReneUhlver's picture
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BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Good night guys,

I got a question about bi-wired systems... I've read much about this but it is really really really "up to" the listener's taste.. I couldn't have any good positioning about other's opinions... What the difference is all about between single and bi-wired? 

Well, now I have a technical doubt about my system in particular:

- KEF Q300 (120W) has 2 pairs of plugs each speaker, you need to rotate the LINK in order to use single or be-wired connection: does this change the impedance of them? It is nominal as 8ohms. (I don't know the schematics about these speakers, if you rotate the link screw I don't know if the speaker will have 2 parallel impedances making it as half as nominal, or what is going on here..)

- the ROTEL RA-12 has 4 pairs of "speakers output": SPEAKER A (left + right) and SPEAKER B (left + right).

In its manual is written that if you choose SPEAKER A or B , the speakers need to have an inpedance of 4ohms minimum... but if you choose A+B making your 2 pairs of speakers ON, the speakers have to have 8ohms minimum.... there my doubts appears: So I can connect my KEF'S as "true" bi-wired configuration, I need to use A+B for my pair of speakers? Choosing A+B in my rotel front panel it will make each speaker to have 60+60W, making each one be "filled" with 120W? (because it says my rotel has 60W/ch).

Maybe Bi-Wiring (A or B with link) is a different thing from Bi-Amplifying my speakers (A+B with 2 pairs of cables for each speaker)... is that the question?

I'm really "lost" on these specs and I don't really know how to do it properly!

I appreciate if anybody can give me some clearness on this!

Thanks a lot,

Rene

 

Reggie Mental's picture
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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Just use a single run of decent (4mm or more) copper stranded cable and leave the brass links in place. Bi-wire is a nonsense. Kef thinks so too, they've abandoned it on the LS50.

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Bi wiring is no more than voodoo you hardly will notice any difference ( Bi amplifying is another story ) each speaker will receive 60W and it dosn't matter if bi-wiring or not .

the Ohm limitations is only for safe precautions if you are not breaking the  volume to very high levels on constant operatinion ( unless you are a D.J. ! )  nothing will happen .

 

 

Hi Fi : Proac Studio 140MK2 / Rotel RC 1580 / Rotel RB 1582 / Rotel RCD 1520 / B&W P7 / Tellurium Q & WireWorld cables   

 

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

OK, I'll have a go.

On the links and the speaker impedance; not overall, don't worry about it.

A and B outputs have been features on amps for a long time (and before bi-wiring became fashionable). Historically, they were used for running two sets of stereo speakers (say one set in the lounge and another in the dining room). In that situation, the amp would see the load on each speaker, hence the suggestion not to go below a nominal load of eight ohms which is an easier load for the amp to drive.

If you want to bi-wire, you do not have to use A and B outputs. You can just use A and have what is sometimes called a 'shotgun' connection where you have two connections at the amp end and four at the speaker end. You can also use A and B together if you want and have four connectors at both ends of your cable.

Whichever way you do it, you will only ever get the rated power from your amp ie 60w. And you cannot bi-amp with an integrated amp. To bi-amp, you need four channels of amplification, eg an integrated amp and a power amp, a pre amp and two stereo power amps or a pre amp and four single channel power amps (commonly called mono blocs).

FWIW i prefer to spend my budget on a 'better' run of cable and single wire the speakers.

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Just try all options available to you and see which sounds best in your opinion.

try the single run with brass connector in place play a well produced track then compare it to a bi-wired config, using A+B speaker outs. you will need the extra run of cable but you may find the out lay is worth it.

I always run the A+B option myself - to my ears the sound is better seperated and cleaner, noticed more with complex tunes at higher levels, but some will swear blind there is no difference - depends on your kit , maybe.

Let us know your findings.

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Hi Rene

Don't want to highjack the thread but wanted to hear your opinion on the combination of the Rotel RA-12 and the KEF Q300.

Exactly the components I am about to buy and was worried that the Kef will sound a bit dry with the Rotel,

Thanks

Mel

 

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

taitai wrote:

Hi Rene

Don't want to highjack the thread but wanted to hear your opinion on the combination of the Rotel RA-12 and the KEF Q300.

Exactly the components I am about to buy and was worried that the Kef will sound a bit dry with the Rotel,

Thanks

Mel

 

 

Not trying to put anything out there, but I can't help feel the RA-12 IS the RA-1520 with a DAC (going by the WHF review is how I'd discribe the 1520) - saying that its a clean sounding amp that provided is not pushed will do fine with that level of speaker. if you like your music 'up' all the time that is... Smile

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

taitai wrote:

Hi Rene

Don't want to highjack the thread but wanted to hear your opinion on the combination of the Rotel RA-12 and the KEF Q300.

Exactly the components I am about to buy and was worried that the Kef will sound a bit dry with the Rotel,

Thanks

Mel

 

Indeed. It will sounds 'dry'... at least compared to Marantz amplification which sounds 'juicy'.. comment from former Rotel RA-11 user.

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

In my experience bi-wire is beneficial where a speaker designer has included the feature as the cross over is optimised to operate at its best in bi wire mode. Bi-wiring is beneficial as it minimised back EMF.

http://en.wikipedia.org/wiki/Counter-electromotive_force

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/biwire/Page1.html

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

from Harbeth forum:

"

Default Biwiring - a non-subject that will not gain you any sonic advantage I really wish this subject of biwiring would just disappear up its own terminals. I don't have many ambitions in life but killing this discussion by deleting the biwire terminals and reverting to just one input pair is going to be at the top of my 2011 New Year's Resolution list for the remaining models that still feature biwire legacy terminals! You've given me a real motivational boost!
The terminals were fitted for one reason and one reason only: to give the user choice. Have I ever used them at exhibitions? No. Have I ever used them for critical listening? No. Have I ever used them during the design of the speaker? No. When we were offering the biwire terminals, right at the end of the design process (which has all been with single wire) I took a saw to the prototype PCB, cut in in half to isolate the bass and tweeter sections and then made a pretty PCB layout based on that. Did I listen to the biwired crossover before authorising production? No. Do I believe that even 0.00000001% of enhanced performance can be gained? No. 
Of all the subjects ranged over in the speaker arena, this one is a complete and utter waste of time - in my opinion. But what do I know about it? I only design the speakers ....... !
Biwiring does do one thing very well though: it introduces the one and only, much appreciated 'fiddle factor' to allow individuals a physical and psychological interaction with their speakers. What else can you do to them other than dust and polish them? Alan A. Shaw


Designer, owner


Harbeth Audio UK"

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Bi-wiring is superstition if you realy want an improvement go for bi-amplifying 2 power amp or 4 monobloks  : more power=more control on the speaker's drivers .

Hi Fi : Proac Studio 140MK2 / Rotel RC 1580 / Rotel RB 1582 / Rotel RCD 1520 / B&W P7 / Tellurium Q & WireWorld cables   

 

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

astracouple wrote:

In my experience bi-wire is beneficial where a speaker designer has included the feature as the cross over is optimised to operate at its best in bi wire mode. Bi-wiring is beneficial as it minimised back EMF.

http://en.wikipedia.org/wiki/Counter-electromotive_force

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/biwire/Page1.html

The second link is a joke right?

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

And yet WHF are always banging on about bi-wiring... Was just reading the review of PSB Image B5 speakers where it said :

 

"There are ways to tweak the sound to a more even balance: firstly, bi-wiring is essential as it adds a touch more weight and organisation to the sound."

If there was a consensus on the issue then there wouldn't be any confusion.

Music: Naim ND5 XS | Naim SuperNait | Kef LS50

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

Bodfish wrote:

astracouple wrote:

In my experience bi-wire is beneficial where a speaker designer has included the feature as the cross over is optimised to operate at its best in bi wire mode. Bi-wiring is beneficial as it minimised back EMF.

http://en.wikipedia.org/wiki/Counter-electromotive_force

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/biwire/Page1.html

The second link is a joke right?

Bloody hope so  :O

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

lpv wrote:

taitai wrote:

Hi Rene

Don't want to highjack the thread but wanted to hear your opinion on the combination of the Rotel RA-12 and the KEF Q300.

Exactly the components I am about to buy and was worried that the Kef will sound a bit dry with the Rotel,

Thanks

Mel

 

Indeed. It will sounds 'dry'... at least compared to Marantz amplification which sounds 'juicy'.. comment from former Rotel RA-11 user.

Not sure what is meant by 'dry' and 'juicy'.  I would characterise the sound as 'detailed & accurate' and therefore what some might call 'bright'.

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RE: BI-WIRE Doubt [ROTEL RA-12 + KEF Q300]

astracouple wrote:

In my experience bi-wire is beneficial where a speaker designer has included the feature as the cross over is optimised to operate at its best in bi wire mode. Bi-wiring is beneficial as it minimised back EMF.

http://en.wikipedia.org/wiki/Counter-electromotive_force

http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/audio/biwire/Page1.html

Have you read the St Andrew's piece in detail? It is good work.  In the simple example he uses, he predicts a 0.1dB (negligable) change in reponse at the crossover point of the two drivers.  He then goes on to point out that it is likely that using real world speaker cable resitances, that the effect will be much less. in other words, biwiring is a waste of time.

What is the 'minimising back EMF' effect you refer to?  

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