Using TWO centre speakers, wired in SERIES, to create lift!

[Son_of_SJ]

For quite some time, a year or three, I've been aware that in my parlour, with a 11.1 speaker system using Audyssey processing of a Denon AVR 4810 receiver, the dialogue from the centre speaker has been a bit physically below the television. The systems in my kitchen and my bedroom (though not the front bedroom, which has only a 5.1 Yamaha receiver) use Yamaha receivers that can drive front presence speakers. The front presence speakers are about four or five feet higher than the centre speakers, and are on the wall immediately behind the televisions. Using one of Yamaha's movie sound processing modes, some of the output from the centre speaker appears to come from the presence speakers, and hence if the centre speaker is (as usual) physically below the television, the overall effect using the presence speakers (on a Dialogue Lift setting of 3, on a scale of 1 to 5) is that then the dialogue appears to come from a height about the middle of the television, not from below the television.

However, the Denon receiver in my parlour doesn't do dialogue lift processing. It does drive Front Height speakers, but that is only for processed and extracted Height information, the Front Height speakers carry no centre channel dialogue. It occured to me one fine day in July last year that the solution might be to use TWO centre channel speakers, and have one (as hitherto) speaker positioned immediately below the television, and one immediately above the television. Then, with a bit of luck, the dialague sound in films would appear to come from a vertical height somewhere in the middle of the television, not below the television. Of course, this effect would work best with two identical centre speakers, which I didn't have - my main centre speaker is a Kef Cresta 20c, and the extra one that I've now added is the centre speaker from my first home cinema speaker package, the Yamaha NX-C130. The Yamaha speaker is physically about only a fifth of the size and weight of the Yamaha, but better than nothing, or so I thought. Lastly at this stage, I wondered how best to connect the two centre speakers - I had heard of people connecting speakers in parallel, but I was worried about too much current being drawn from the receiver in that case, so I thought that I would connect the speakers in SERIES.

 

[Son_of_SJ]

But, how could I position the smaller centre speaker immediately above the television? Answer – a small portable music stand! Gumtree was my friend, I saw this £4 effort advertised about 75 minutes’ walk from where I live, so in July I went there and bought it – one of my best sub-£10 purchases ever.

 

[Son_of_SJ]

Below is a picture of the two centre speakers around the Panasonic television, on a very sunny day - yes, we do sometimes get them in Edinburgh! Note also that in order to prevent the lower, larger centre speakers from obscuring the Panasonic, the television's desktop stand is on four blocks of wood, to raise it about two inches. The whole thing is on an Optimum AV300 stand, which is the same as the one that Gel has. The 65-inch television overhangs the Optimum stand at the sides, but in my opinion not too badly.

 

[Son_of_SJ]

A view from behind the television, which shows the £4 music stand carrying the small Yamaha centre speaker.

The two centre speakers are in SERIES, not in parallel. The electrical connections are: (a) from positive (+ve) centre speaker output pin of the Denon receiver to +ve terminal on the Kef centre speaker; (b) from –ve terminal of the Kef centre speaker to the +ve terminal of the small Yamaha centre speaker; (c) from –ve terminal of the Yamaha back to the negative centre speaker pin of the Denon.

So, how does it all work?? Pretty well, though not perfectly – it would have been perfect if I’d had two identical speakers. But, even as it is, I’m now no longer conscious of the sound coming from below the television. In fact, I now don’t think about the centre channel sound at all, but when I do, it appears to be coming from a vertical height of one third of the way up the television. (With two identical speakers it would have been exactly half way up the television.) Job done!

 

[Son_of_SJ]

Does anyone know how to stop the width / height ratios of pictures being distorted when pasted on to this forum???

 

[Benedict_Arnold]

If you wire them in series, you'll get half the power output of one single speaker. If you wire them in parallel and assuming your receiver can cope with both the lowered impedance seen at the receiver (half that of a single speaker) and can deliver twice the current as a result, you'll get the full output of each speaker.

Say you're getting, for argument's sake 80 watts RMS out of a single 8 ohm speaker. Since Power (P) = Current (I) squared times resistance, your current draw is the square root of 80 watts divided by 8 ohms = the square root of 10, which is 3.162 amps. Now since voltage (V) = I.R, your amp will need to produce a voltage of about 25.3 volts to force this much current through the speaker.

Now say you've got two 8 ohm speakers in series.

Your impedance is now 16 ohms. So, with the same 25.3 volts, you'll get a current of 25.3/16 = 1.58 amps, or half what you got before. Your power output per speaker will be 1.58 squared times 8 ohms, or 20 watts, giving you a total output of 40 watts. Like I said, half what you'd get out of a single speaker.

Now say you've got two 8 ohm speakers wired in parallel.

Your impedance is now 1/(1/8 + 1/8) = 4 ohms. Let's assume your receiver can cope with a 4 ohm load or has a switch on the back or a menu setting enabling this.

Your current draw at 25.3 volts is now 25.3/4 = 6.32 amps. Let's assume you receiver can deliver this much current.

The current gets divided into two, half going through each speaker (assuming they have identical impedance, of course). So 3.16 amps is going through each speaker, producing 3.16 squared times 8 ohms = 80 watts per speaker, total 160 watts.

 

[Benedict_Arnold]

PS. This is exactly how I wired up two 24-inch x 8-inch centre-channel speakers in my home theatre. I would have used one in the wall, but there's a stud "Murphy's Law" right where I didn't need it to be, so rather than have an asymmetric centre speaker, I've put one above and one below the TV, mounted in home-made surrounds. Once I have the cash for a screen and a 4K projector, I'll mount them in the wall, but left-right symmetrical of the screen vertical centreline, on the horizontal centreline.

 

[ellisdj]

It would have been much easier to angle the below centre speaker up at the listening position then it setup properly will integrate perfectly with the overall sound field.

 

[Son_of_SJ]

If you wire them in series, you'll get half the power output of one single speaker. If you wire them in parallel and assuming your receiver can cope with both the lowered impedance seen at the receiver (half that of a single speaker) and can deliver twice the current as a result, you'll get the full output of each speaker.

I entirely agree with your calculations, which certainly don't stretch my B. Eng degree in Electronics to understand. But the rub is your phrase that I've highlighted. I wasn't sure if the receiver could deliver double the current, and I didn't want to find out if not with an all-too-familiar smell of burnt electronics (before I got my degree!) and a repair bill of about £200 to £300. So I thought it was safer to wire them in series, not in parallel, and live with the lower acoustic output.

The funny thing is, somehow the combination of the two speakers seems only very slightly less powerful than the single speaker, not the 3dB less that your calculations would suggest. I've increased the volume setting of the centre speaker by only 1 dB, and it now sounds just as loud as previously, but from a better centralised sound vertically, not from below the television. So I'm happy!

 

[Son_of_SJ]

It would have been much easier to angle the below centre speaker up at the listening position then it setup properly will integrate perfectly with the overall sound field.

No, I don't agree. My problem wasn't the direction that the centre channel sound was coming from, my problem was that I was all too aware of its vertical location below the television. Angling the centre speaker up would not have helped. And the cost was only £4, plus two 75-minute walks, and I'm supposed to be walking more anyway, and then about an hour at home fiddling with connections and setting up the music stand and placing the Yamaha speaker on it. So it's all good!

 

[bigboss]

Hmmm....that's strange. Psychoacoustics should have placed the sound on the TV. In my previous house, the centre speaker was above the TV, closer to the ceiling. But I never felt that the sound was coming from the top.

 

[ellisdj]

It would have been much easier to angle the below centre speaker up at the listening position then it setup properly will integrate perfectly with the overall sound field.

No, I don't agree. My problem wasn't the direction that the centre channel sound was coming from, my problem was that I was all too aware of its vertical location below the television. Angling the centre speaker up would not have helped. And the cost was only £4, plus two 75-minute walks, and I'm supposed to be walking more anyway, and then about an hour at home fiddling with connections and setting up the music stand and placing the Yamaha speaker on it. So it's all good!

Angling the speaker will work if not then you have other issues either setup of the fact it's on glass or could be a few things. Heard a lot of systems with speakers below a tv never seen it as an issue honestly

 

[Son_of_SJ]

Angling the speaker will work if not then you have other issues either setup of the fact it's on glass or could be a few things. Heard a lot of systems with speakers below a tv never seen it as an issue honestly

No, I don't think that I have setup issues, nor do I think that the glass Optimum AV300 stand is a problem. I have heard other systems, both at various dealers and in other people's homes, and there I have always been aware of the centre channel sound coming from below the television. I'm not sensitive to flicker or various other things that some people complain about, but it seems that I am sensitive to the location of the centre channel speaker, if it is below the television. My solution, with two centre channel speakers, one immediately above the television and wired in series, works for me.

 

[Son_of_SJ]

Hmmm....that's strange. Psychoacoustics should have placed the sound on the TV. In my previous house, the centre speaker was above the TV, closer to the ceiling. But I never felt that the sound was coming from the top.

Maybe I'm strange! (I've been told that before .....!) But I can check the effect easily. In the kitchen system, the 8.1 speakers, including presence speakers, are driven from a Yamaha RX-A2010 receiver. Now, with a single button press on the Yamaha's remote control, I can change from playing Blu-ray straight (where the 5.1 or 7.1 audio signals are sent directly to the appropriate speakers, with no sound processing) or using the one of the Movie modes, which do involve the presence speakers to carry some of the centre channel output to create dialogue lift, so that the dialogue appears to come about half way up the televsion, instead of from only the centre channel speaker, which is immediately below the television. A single button press goes from one mode to the other. And I can definitely tell that with the straight mode, the dialogue is coming from below the television and in the Movie mode, the dialogue appears to come from about half-way up the television, not below it. Equally definitely, I prefer the Movie mode to the straight mode, though I know that some purists aver all sound processing. It would take only a moment to demonstrate this effect to any passing visitor!

 

[RobinKidderminster]

With as many systems at home to make a small retailer envious you must be struggling with the centre speaker focus. My two penneth is that for most of us our brains adapt to dovetail the picture and sound especially with speech & faces. I am sure a top and bottom speaker would better focus the vocals but most would find it unnecessary.

 

[ellisdj]

Below is a picture of the two centre speakers around the Panasonic television, on a very sunny day - yes, we do sometimes get them in Edinburgh! Note also that in order to prevent the lower, larger centre speakers from obscuring the Panasonic, the television's desktop stand is on four blocks of wood, to raise it about two inches. The whole thing is on an Optimum AV300 stand, which is the same as the one that Gel has. The 65-inch television overhangs the Optimum stand at the sides, but in my opinion not too badly.

Also if you running that centre speaker with the 2 main speakers in the rear of the picture you are always going to have a hard time tying that front sound stage together. The L&R speakers are feet behind the centre by the looks of it.

Of course the av receiever will set the delay but that affects sub integration and sub phase. Getting them more in line will be a huge sonic benefit .

 

[ellisdj]

Son of SJ - I think you are experiencing a few things here, no such thing as magic ears or susceptibility, everyone can hear once they are trained to hear it

I am guessing you are using a horizontal centre and vertical orientated L and R speakers like a lot of people

This will break down the front sound stage to a point regardless of how well the speakers are all integrated and how good all the kit is. However you can reduce this effect to a point by either raising the centre speaker the same height or angling it upwards to have the ear more on axis with the tweeter probably similar to how the L and R speakers are due to their increased height.

I think you would likely prefer cinema style speakers XTZ, MK, KK style where all front speakers are identical. You would benefit from raising the height of the display and having all front 3 speakers the same height.

I see what you have done no offence intended as more of a bodge fix rather than a true step forward in your system sound performance. Of all the people running home cinema I have never seen anyone do what you done before. I think its more a hinderance than a true help, especially as the speakers are not even the same

There is no subsitiute for proper speaker placement - eq does not fix this depsite what some people think.

You should also check your time delay of the centre speaker making sure its exactly in time with the sub - there are complex perfect ways to do this - or an easier way that will get you 90%. I wouldnt trust any auto receiver setup to do a bang up job, manual will always be better. If you do this for the front L and R as well the distances of the front 3 speakers should integrate the front soundstage better and you therefore dont need another speaker.

Another thing to check is lip sync - this could be out and need increasing which will recess the vocal into the soundstage more and tie in your front sound stage, panning and bass better as well.

Please dont think I am trying to be a **** here, I honestly dont see the mileage in what you have done, I think take the time to think about your front 3 setup and how you can improve it.

The centre speaker is argued as the most important speaker of them all and often it gets the rawest deal - L and R get proper dedicated speaker stands but the centre gets plonked on a TV stand out of convienience and then people wonder why their dialogue isnt that clear and such like problems.

 

[Benedict_Arnold]

FWIW if you hunt around on Amazon or EBay or wherever you should be able to find speaker brackets that bolt to the mounting screw holes on the back of your TV, enabling you to hang a centre speaker below, or support one above, your TV.

To Son-0f-SJ - my dugrea is in mekanicual injurearing (Brunel 84-88), but we did as much elektricual injunearing in the first two years as we did solid body mechanics and thermodynamics / fluids. The reasoning being most machines aren't powered by steam engines any more, so knowing how to get the juice to our electric motors, and how they work, was probably a good idea. I tnink you'll also find that unless you've got the volume knob dialled up to 11 (see "Spinal Tap") your receiver will cope. I cheated though. In preparation for a 7.2.4 setup with the "proper stereo" speakers acting as extra fronts over and above those I've got in the wall, I'm using a cheap Onkyo 75 WPC power amp to power my centre speakers. I used a splitter off the back of the receiver and feed the same centre signal off the RCA plug on the back of the receiver into both left and right sides of the power amp, drive one speaker off each. I use the same idea to drive the "proper stereo" speakers with bridged stereo power amps driving each biwired and biamped speaker, the receiver itself driving the in-wall fronts (for now). When I get my new receiver I'll just use the in-walls until I also get the cash together to get a "proper (and expensive) stereo" again.