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Central Dual Speaker

SirLouen

Standard Member
Recently I bought a new AV Onkyo 525
After I finished mounting the system I had a thought:

Some years ago when I bought my Behringer monitors B2030P they came in 3 pack of 2. I was thinking on building a 7.1 system since my last AV was 7.1 capable. But I ended building a 5.1 and stored 1 in the garage (i though on the 6.1 but it did not fit in the back of the room well and after I preferred to put it away)

Now I've been thinking if it will be possible to build a central dual monitor system since I read something about this some weeks ago

Is this possible with this system configuration?
Onkyo 525 Onkyo | TX-NR525
130W p/channel
B2030P Behringer: TRUTH B2030P

If possible, how shall I do this? Any DIY explanation that I can see somewhere?

Thanks in advance
 

PSM1

Distinguished Member
Not sure I understand what you are trying to do? Are you trying to use 2 speakers for the central channel?
 

Jameskatie

Distinguished Member
If you can get the impedance right for the amp then yes go for it
 

Jameskatie

Distinguished Member
You will need to wire the two speakers either parallel (red to red black to black) or series (red from one to amp black and red inbetween together and black from other to amp) to make sure you don't show your amp a load it cannot handle.

On the back of the speakers it will say how many ohms they are, if they are both 8 ohm wiring in parallel will show the amp a 4ohm load, if the amp can run at 4 ohm it will be fine.
If your speakers are four ohm each wiring them parallel will show the amp a 2ohm load witch it certainly won't do with out breaking it so wiring in series would show an 8ohm load which would be fine.
If they are 8 ohm and your amp cannot handle a 4ohm load you would have to wire in series and show the amp a 16ohm load which will work but you will have to see if you get the output required out of them, should do as increasing the amount of speakers increases the sensitivity
 

PSM1

Distinguished Member
Personally I would not bother since more than likely cause more issues than it will improve. Connect the speakers in parallel and you half the impedance which could be too low for the amp. In series you double the impedance which can have other issues and also each speaker sees a different voltage. Having 2 speakers close together producing the same sound may well cause sound interference issues hence I would stick with just the 1 speaker as a centre. More in this case does not mean better I feel.
 

SirLouen

Standard Member
This are the specs:

http://www.behringer.com/assets/B2030P_P0194_S_EN.pdf
These are 8 ohm monitors

Onkyo TXNR525

Dynamic Power: 180 W (3 ohms, 1 ch), 160 W (4 ohms, 1 ch), 100 W (8 ohms, 1 ch), THD+N (Total Harmonic Distortion + Noise): 0.08% (20 Hz-20 kHz, Half power)
  • Damping Factor: 60 (Front, 1 kHz, 8 ohms)
  • Input Sensitivity and Impedance: 200 mV/47 k-ohms (Line)
  • Rated RCA Output Level and Impedance: 200 mV/2.2 k-ohms (Line Out)
  • Maximum RCA Output Level and Impedance: 2.0 V/2.2 k-ohms (Line Out)
You feel in this case two speakers in parallel wont mean better central sound solution?
 

Jameskatie

Distinguished Member
Try it and see the amp can take a 4ohm load so good to go
 

PSM1

Distinguished Member
Just because it gives a wattage value at 4 ohm does not mean it can run at that without issue. Also has a value at 3ohm and I would certainly not run speakers with that low an impedance. I would advise against it but it is your system so do what you want. What are you trying to solve by having 2 centre speakers? Onkyo are known to run hot and have hdmi board issues due to this so running low impedances on it which will make it run hotter does not seem sensible especially since I can not see it improving anything and could make it sound worse.
 

SirLouen

Standard Member
Ok, I understand. I'm not trying to solve anything. I just want to improve audio quality since I have 1 speaker that is in the garage and I'm not using :)
 
Not a good idea, phase issues. Just use a single quality speaker for the center.
 

BlueWizard

Distinguished Member
As we have all seen, most center speakers are MTM, meaning a horizontal configuration of a Mid-Bass+Tweeter+Mid-Bass. That in itself is a less than ideal configuration.

If you use two bookshelf speakers for a center channel, you have to consider the orientation of the speakers. For example, if they are laying on their sides, will they be oriented as Bass-tweeter-tweeter-Bass, or with the be tweeter-Bass-Bass-tweeter or perhaps Bass-tweeter-Bass-tweeter?

The ideal configuration for the speakers when placed horizontally would be Bass-Tweeter-Tweeter-Bass. You want to place the tweeters as absolutely close together as you possible can to prevent phase cancelling and comb filtering. How much those problems will bother you personally in your circumstances is not predictable, maybe a lot and maybe not.

I'm in a vaguely similar situation. I have two large pair of speakers side-by-side. Not necessary for music but great for Home Cinema. I do get some Comb Filtering and some Phase Cancellation, but I feel that what I gain is more than what I lose, so I'm content.

As others have pointed out, there is the matter of Impedance. Two 8 ohm speakers in Parallel is 4 ohms. Your amp may or may not like that. Again, hard to predict.

If you wire the speaker in Series, the output will be the same as a single speaker, however, you will drive the speaker pair much more gently to get a given level of output. In fact, you will have roughly half the excursion for equal output, and twice the power handling capacity. But, two speakers so wired only put out sound equal in volume to one speaker.

I will try to explain this but it is a bit convoluted. Because you have two speakers you have twice the output. But because the speakers are wired in Series, each speaker gets half the signal.

So if X is the output of a single speaker, and we now have two speakers, that gives us 2X. Now because they are in Series each speaker only get HALF (1/2) the Signal, so we now have 2X/2.

2x / 2 = X

X is the output of a single speaker; X is the output of two speakers wired in Series. But at that output, you have half the excursion or cone movement so the speakers are straining much less to give the same output level. You have reduced the excursion by half and increased the power handling capacity. So even though the output is the same, you have gained something.

You amp, is far from high end, though reasonably far from the bottom as well -

Onkyo | TX-NR525

Onkyo is not known for its strong power ratings -

http://www.uk.onkyo.com/downloads/2/4/8/8/0/ONKYO_TX-NR525_datasheet_EN.pdf

* 130 W/Ch (6 Ω, 1 kHz, 1% THD, 1 Channel Driven, IEC)
* 160 W/Ch (6 Ω, 1 kHz, 1 Channel Driven, JEITA)


The fact that they are rating at 6 ohms and at only one frequency, and at pretty high distortion levels, and the fact they are using IEC and JEITA instead of Continuous power in another indication that they are fudging on the power ratings.

I'm going to guess the real power on this amp is about 80w/ch to 8 ohms full spectrum with 2-channels driven at reasonable distortion levels.

However, given that you will only drive one channel at 4 Ohms (2x center in parallel), and assuming your amp has adequate ventilation, this may not be a problem. I think it is certainly safe enough to try. If it does overheat, the amp will simply shutdown. I can't guarantee no problems, I can only say that I think you are not likely to have any problems.

Try both Series and Parallel wiring, and see if you like what you hear, but DO PLACE the tweeters as close together as possible.

Just one man's opinion.

Steve/bluewizard
 
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PSM1

Distinguished Member
As already said adding another speaker will most likely decrease your audio quality. It will certainly no add to it so I would leave it were it is in the garage. The only sensible way to use it would be as a rear centre speaker in a 6.1 configuration but only if you have space to the rear of your seated location.
 

PSM1

Distinguished Member
But what do you think you are going to gain by doing it? How is having 2 of the same speaker in the centre going to help? Considering you will get some form of sound cancellation etc. going on it is most likely going to make it sound worse.
 

BlueWizard

Distinguished Member
But what do you think you are going to gain by doing it? How is having 2 of the same speaker in the centre going to help? Considering you will get some form of sound cancellation etc. going on it is most likely going to make it sound worse.

The sound cancellation is likely to be frequency specific. For example, if the tweeters are spaced 3" apart (76mm), then the frequency associated with that is 4500hz. If your woofers are 16 inches center to center, then the frequency relative to that distance is 843hz. If the crossover of the bass drivers is BELOW 843hz, then this aspect doesn't matter. If the crossover is at or above 843hz, then there is going to be a problem. Potential problems are Lobing, Phase Cancellation, and Comb Filtering.

But, you are also going to gain. The question is are you going to gain more than you lose. Are you going to gain in areas that you want to gain, and equally are you going to lose in areas that one hopes are less significant to you?

You can only try. Try and you will know.

One of the gains is that you are simply moving more air. As some else pointed out, you get equal sound in series, but half the excursion, meaning you can go a lot louder without distortion.

It is about weighing the pluses and minuses to see if you, the individual, find any benefit.

Steve/bluewizard
 

moonfly

Banned
Half the distortion for a start
Plus increased sensitivity and headroom in the centre channel, so it will also go louder. Stacking them will alter the dispersion characteristic which could also be beneficial. Series wiring them to give a lighter amp load could take some strain of the amp as well.
 

PSM1

Distinguished Member
But if you have 2 speakers the same and assuming that the OP can currently get a volume that is high enough without major distortion then were is the gain there? They could move more air as it were with 2 speakers but since they have a sub and presumably a sensible crossover point then the centre is not going to be going that low anyway. Also the sub will move far move air than even 2 of the monitor speakers the OP has. I just see far more issues than actual gains. Just because they have an extra speaker does not mean it should be used!!!!! Also would not be happy with a 4 ohm load on an Onkyo receiver, they hardly have the best reputation for reliability so why drive it even harder in a parallel configuration. If in series then will have to turn the trim up on the centre speaker a fair bit to get the same level as the front left/right speakers. Since the OP has the same speaker across the front 3 speakers then this is the ideal setup so why mess with this?
 

BlueWizard

Distinguished Member
"I just see far more issues than actual gains."

Yes, you see far more issues than gain. But it is up to the Original Poster to decide if his ears bare that out. He has the speaker, it cost nothing to try. Knowledge is never wasted.

I do agree that a 4 ohm load on an Onkyo amp is a bit border line. But it is only one channel, and assuming the amp is properly ventilated, it is worth trying. And should be safe, assuming you don't go crazy on the volume control. Whether a 4 ohm Center is practical long term is a matter for later discussion.

In series, there should be no problem, and yes, it depends on the volume levels he is playing at to determine if there is any real gain. But the only way to know is to try.

In my case with two pair of front speakers, I can definitely hear the negative aspects, but they are not enough to over-ride what I gain. It is a trade off. I'm willing to lose what I lose to gain what I gain. But given a substantially larger budget. I would rather have one great speaker, than two OK speakers. Unfortunately, I don't have a substantially larger budget, and I have to make the best of what I have.

In either case, it would be necessary to re-run the SetUp routine to re-balance the speakers.

I don't disagree with anything you said in concept. But, for the individual, the only way to truly know is to try.

The only combination that could potentially have a problem is the Parallel configuration. Just for a quick SetUp and listen, I'm not sure there will be a problem. Perhaps if you try sustained prolonged playback with 4 ohms on the Center channel, the amp might shut down. While I can't guarantee it, I don't see this causing damage.

In either case, I don't expect huge gains, but the only way to know if either configuration is worthwhile and practice, is to try.

One must ask, is this simply an excuse to use a currently unused speaker, or are you searching for a way to improve the system; implying in the process that the system needs improving?

For what it is worth.

Steve/bluewizard
 

moonfly

Banned
Gains or issues asides, I always like to encourage people to experiment, particularly when it costs nothing to do so. You will learn far more that way than reading theory on a forum.
 

Mr Andy

Established Member
I'd be tempted to pay with how you configure the dual centres. If you could do above and below the screen with both speakers equal distant to you it may sound better then right next to each other
 

BlueWizard

Distinguished Member
Keep in mind, you will have to recalibrate between trying Series and Parallel.

Parallel is going to be louder, and that alone could make you prefer it.

However, Series, while no louder than one speaker, is going to be less strained, with less excursion for a given output, and with higher power handling capacity.

Steve/bluewizard
 

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