2 x bookshelf speakers as central speaker?

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MrFlower

68 posts

Master Geek

#74880 9-Jan-2011 14:58

hi all, need some help here....

I've came up with an idea of running 2 book shelf speakers as centre speaker by placing them on their side, so I bought a pair of Wharfedale Evo2-8 bookshelf to match my existing front Evo2 40 and rear, which is Evo 40, They are all 6 ohms, my receiver is Yamaha RXV3900.

Any comment? or problems I may face? the receiver now need to drive 2 speakers at 6 ohms, rather than one traditional central speaker at 6 ohm....?

Thanks

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1574 posts

Uber Geek

#425446 9-Jan-2011 15:17

What you are doing is essential possible, but the effective impedance will be 3 ohms. This is if you are running them in parallel.

You will be putting extra stress on your amplifier.
It probably won't have much of a negative effect if you run the system at a low volume, but if you were to really crank it, you would run the risk of damaging the centre channel on the amp.

Batman

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#425457 9-Jan-2011 16:03

one word, inteference. which means everyone that isnt seated directly in front of the speakers will hear weird stuff. stick with one center speaker.

illicit

553 posts

Ultimate Geek

#425476 9-Jan-2011 16:53

^^^ interference? explain?

You could run them in series (12ohm) and turn up the center channel in the amplifier

richms

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#425479 9-Jan-2011 17:04

The distance between the listener and the 2 speakers will not be the same, so some freqs will be boosted and some cut depending on their wavelength. If you put it so the tweeters are close it may be tollerable, but there is a reason they only ever have one on a proper speaker.

Richard rich.ms

MrFlower

68 posts

Master Geek

#425483 9-Jan-2011 17:08

illicit: ^^^ interference? explain?

You could run them in series (12ohm) and turn up the center channel in the amplifier

Can you please explain how to run them in series?

Thanks

richms

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#425493 9-Jan-2011 17:52

MrFlower:
illicit: ^^^ interference? explain?

You could run them in series (12ohm) and turn up the center channel in the amplifier

Can you please explain how to run them in series?

Thanks

Amp + to first speakers +, form that speakers - to the second speakers +, from the second speakers - back to - on the amp. You will need to up the level on the amp to compensate for the higher impedance. I cant recall if its 3 or 6dB you will need to boost it by.

Richard rich.ms

illicit

553 posts

Ultimate Geek

#425561 9-Jan-2011 22:03

richms: The distance between the listener and the 2 speakers will not be the same, so some freqs will be boosted and some cut depending on their wavelength. If you put it so the tweeters are close it may be tollerable, but there is a reason they only ever have one on a proper speaker.

So when listening to a stereo system when not seated in the exact optimum position in a room with a perfectly calibrated system would sound crap also?

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tomgeeknz

923 posts

Ultimate Geek

#425571 9-Jan-2011 22:19

To explain the interference problem, If you have two speakers outputting the same source frequency at two different points, they crossover as above, causing loud and quiet spots as you move across the sound field. The picture above demonstrates this using blue light. If it was a sound field and you were to walk across it in a straight line where the blue and black bars are, in the blue parts the sound would get louder and in the black bits it would get quieter.

tomgeeknz

923 posts

Ultimate Geek

#425573 9-Jan-2011 22:22

illicit:
richms: The distance between the listener and the 2 speakers will not be the same, so some freqs will be boosted and some cut depending on their wavelength. If you put it so the tweeters are close it may be tollerable, but there is a reason they only ever have one on a proper speaker.

So when listening to a stereo system when not seated in the exact optimum position in a room with a perfectly calibrated system would sound crap also?

No, because the sound coming from the left and right speakers is different, it is this difference that causes you to here things in 3 Dimensions, as you can tell where the sound is coming from. Interference only occurs when the same signal comes from two different points....

[I am a sound engineer and physics student]

richms

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#425585 9-Jan-2011 23:36

illicit:
richms: The distance between the listener and the 2 speakers will not be the same, so some freqs will be boosted and some cut depending on their wavelength. If you put it so the tweeters are close it may be tollerable, but there is a reason they only ever have one on a proper speaker.

So when listening to a stereo system when not seated in the exact optimum position in a room with a perfectly calibrated system would sound crap also?

stereo is meters apart so the effect is much less pronounced, but that is why the center channel exists, so that centrally placed mono sounds sound a lot better for everyone in the room. If you are not going to have friends watch with you, then you can do without the center if you sit in the middle.

Richard rich.ms

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#425588 10-Jan-2011 00:40

you can try it for yourself - old speaker vs one new speaker vs 2 new speakers parallel vs 2 new speakers series.

if you want to that is, tedious i know. I have defied physics and tried it out myself and found that one was way superior than 2. (hey i actually did exactly what you thought of so great minds must think alike... until brought down by physics)

illicit

553 posts

Ultimate Geek

#425624 10-Jan-2011 08:09

I get the physics side of it, but I'm not sure the majority of people would be able to hear the difference, I could well be wrong as I have not tried it myself.

I would have thought the benefit of a center channel 'image' centered on the TV screen would out weigh the rest

geekiegeek

2513 posts

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#425646 10-Jan-2011 09:45

so you brought speakers to do this? why didnt you just buy a center speaker?

I could understand this if you had no money and had a couple of old bookselves lying around..

Dunnersfella

4086 posts

Uber Geek

#425649 10-Jan-2011 09:51

You may well be better off using the two new bookshelves to create a 7.1 system.

MrFlower

68 posts

Master Geek

#425656 10-Jan-2011 10:35

hi all.

Bought them cos they seemed a deal to me, was thinking if it sound terrible, I will make my system into a 7.1..

I hooked up the speaker late last night, did them in series,

Will do an automatic setup thing with the receiver today. wondering what will happen?

Is the receiver smart enough to tell there are 2 x 6 ohm speakerS in series and therefore automatically make the adjustment?

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