# Why do I need to overdrive my center channel



## TonyLS (Sep 26, 2008)

The center channel (2, 4" drivers) I currently have does not match the front bookshelf speakers that I am using ( 1, 5 1/4 driver). I need to over drive the center volume by 5 to 6 db's from the calibration point that was setup with the receiver's calibration sequence inorder to hear the dialogue properly. Is this due to the mismatch with the center and front bookselves? Everything is 8 ohms.


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## tonyvdb (Sep 5, 2007)

TonyLS said:


> Is this due to the mismatch with the center and front bookselves? Everything is 8 ohms.


Could be, how large are the drivers in your bookshelves? Its sounding to me that your center channel is not able to reproduce the same frequency response as your mains.


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## TonyLS (Sep 26, 2008)

The bookshelves have a single 5 1/4" driver. The center and bookshelves are made by the same company, however they do offer a center channel that's matched to the bookshelves I have. I'm thinking about getting that one. They told me that the tone quality will match very well with the high-end center. I'm surprised with the large difference I'm seeing.


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## tonyvdb (Sep 5, 2007)

speaker cabinet design and the materials used play a huge part in the tonal quality so it could very well be that replacing the center with a higher quality one will improve the sound dramatically.


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## Wayne A. Pflughaupt (Apr 13, 2006)

Some speakers aren't as efficient as others. A speaker with low efficiency will require more power (and consequently higher volume settings) to reach the same SPL level as a speaker with higher efficiency.

Regards,
Wayne


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## thxgoon (Feb 23, 2007)

So you ran auto calibration, _then_ boosted the levels?

It could be that your center has some resonance which is making it hard to distinguish dialog properly, or it could be that you just prefer it louder. Which speakers are you using?


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## maikeldepotter (Jan 10, 2008)

TonyLS said:


> The center channel (2, 4" drivers) I currently have does not match the front bookshelf speakers that I am using ( 1, 5 1/4 driver). I need to over drive the center volume by 5 to 6 db's from the calibration point that was setup with the receiver's calibration sequence inorder to hear the dialogue properly. Is this due to the mismatch with the center and front bookselves? Everything is 8 ohms.


Well, I have to boost the center channel (Dynaudio Contour S C) with +4 dB when calibrating against the fronts (Dynaudio Contour S 1.4) using a Radio Shack meter. The speakers are designed to work together (see specs below). The fronts and center are powered by two seperate Rotel RB-981 amplifiers. For the center I use the right channel (leaving the left idle) and the amplifier is not mono-bridged. Listening distance is identical as are the speaker wires. I don't have a clue why I still have to boost the center. Tried switching amlpifiers but it did not change anything....

Contour S 1.4 Contour S C
Sensitivity
(2,83 V/1 m) 85 dB 86 dB

IEC Power Handling 160 W 150 W

Impedance 4 Ohms 4 Ohms

Frequency Response (± 3 dB)	41 Hz – 25 kHz 65 Hz – 25 kHz 

Box Principle 2-way, bass-reflex 2-way, bass-reflex 

Crossover Frequency 1900 Hz 1400 Hz

Weight 12.6 kg 10.3 kg

Dimensions (W x H x D) 188 x 404 x 360 mm 7.4 x 15.9 x 14.2"	
490 x 160 x 303 mm 19.3 x 6.3 x 11.9"


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## tenzip (May 4, 2007)

I think the question to ask is, how does it sound? Are you noticing weird things happening in your front soundstage, like cars/planes/whatever getting much louder/closer in the middle as they move across the screen? If the sound is acceptable, I don't think I'd get too fussed about it. I have my center boosted a couple of dB over the rest, as I have trouble distinguishing dialogue sometimes, but it doesn't seem to mess with the soundstage noticeably.

Of course, if you want an excuse to upgrade . . . there it is.


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## salvasol (Oct 31, 2006)

> ...I need to over drive the center volume by 5 to 6 db's from the calibration point that was setup with the receiver's calibration sequence inorder to hear the dialogue properly...





> ... Well, I have to boost the center channel (Dynaudio Contour S C) with +4 dB when calibrating against the fronts (Dynaudio Contour S 1.4) using a Radio Shack meter


After you boost the center channel ... Are you reading the same SPL on each speaker???? (75db I assume) :yes:

First you mentioned 5-6db from calibration point ... then, +4db when calibrating against the front :huh:

Most of the time each speaker will have different level ... as long as you get the 75db on each, is not a problem :yes:


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## maikeldepotter (Jan 10, 2008)

tenzip said:


> I think the question to ask is, how does it sound? Are you noticing weird things happening in your front soundstage, like cars/planes/whatever getting much louder/closer in the middle as they move across the screen? If the sound is acceptable, I don't think I'd get too fussed about it. I have my center boosted a couple of dB over the rest, as I have trouble distinguishing dialogue sometimes, but it doesn't seem to mess with the soundstage noticeably.
> 
> Of course, if you want an excuse to upgrade . . . there it is.


In my case _- NOT being the owner of this thread by the way - _ t sounds GREAT! Just want to know - out of curiousity - why speakers that have nearly identical sensitivities can differ 4 dB in sound level. Dynaudio has a VERY good reputation of delivering high quality stuff, and the contour series is popular amongst high-end surround fanatics. Maybe I should put this question forward to the Dynaudio guys...


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## maikeldepotter (Jan 10, 2008)

salvasol said:


> :
> First you mentioned 5-6db from calibration point ... then, +4db when calibrating against the front :huh:
> :


The +4dB is coming from me, not being the thread owner. Sorry for the confusion...


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## tenzip (May 4, 2007)

maikeldepotter said:


> In my case _- NOT being the owner of this thread by the way - _ t sounds GREAT! Just want to know - out of curiousity - why speakers that have nearly identical sensitivities can differ 4 dB in sound level. Dynaudio has a VERY good reputation of delivering high quality stuff, and the contour series is popular amongst high-end surround fanatics. Maybe I should put this question forward to the Dynaudio guys...





maikeldepotter said:


> The +4dB is coming from me, not being the thread owner. Sorry for the confusion...


Ah. Now it becomes a bit clearer, but I think my question still stands.

20 lashes with a wet noodle to Maikel for causing us all mental anguish by muddying the waters. :neener:


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## TonyLS (Sep 26, 2008)

It's not just me, others listening to the center agreed that it needed a lot more volume. It still lacked depth and tone quality at the high volume level. I wanted to purchase the larger center but had height restrictions due to the other components that I have. 

I decided to remove the cable box and use a wireless IR expander, so now the cable box sits behind the table which frees up enough space for the matched center channel

I received the new center last night, amazingly different! I don't have to increase the volume from the original calibration setting(based on ear and SPL) , and the tone quality is superb! I should have listened to the sales guy from the beginning, didn't think one step down in center quality would have been that noticeable. I believe the main factor was with the mismatch of the front bookshelves.


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## salvasol (Oct 31, 2006)

TonyLS said:


> I received the new center last night, amazingly different! I don't have to increase the volume from the original calibration setting(based on ear and SPL) , and the tone quality is superb! I should have listened to the sales guy from the beginning, didn't think one step down in center quality would have been that noticeable. I believe the main factor was with the mismatch of the front bookshelves.


Good to hear that you solved your problem :T


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## salvasol (Oct 31, 2006)

maikeldepotter said:


> ... out of curiousity - why speakers that have nearly identical sensitivities can differ 4 dB in sound level.
> ...


I think that the room boundaries or the placement has a lot to do with that :yes:


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## maikeldepotter (Jan 10, 2008)

salvasol said:


> I think that the room boundaries or the placement has a lot to do with that :yes:


That thought crossed my mind too. I suppose that putting the Radio shack meter close to the speakers (about 2 feet) will eliminated most of this effect, and subsequently should bring the readings closer together. I will try this first.


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## salvasol (Oct 31, 2006)

maikeldepotter said:


> ... I suppose that putting the Radio shack meter close to the speakers (about 2 feet) will eliminated most of this effect, and subsequently should bring the readings closer together...


That's possible ... but remember that you need to calibrate them with the mic at your listening position to get the same volume level from all speakers :yes:


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## maikeldepotter (Jan 10, 2008)

salvasol said:


> That's possible ... but remember that you need to calibrate them with the mic at your listening position to get the same volume level from all speakers :yes:


Thanks for confirming my understanding: this experiment will not change my calibration settings.

I came to think of another question which might deserve a new thread. 

REMARK: I moved this question to a new thread: 
http://www.hometheatershack.com/forums/general-discussion/13703-ideal-amount-good-reflections.html


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## maikeldepotter (Jan 10, 2008)

maikeldepotter said:


> That thought crossed my mind too. I suppose that putting the Radio shack meter close to the speakers (about 2 feet) will eliminated most of this effect, and subsequently should bring the readings closer together. I will try this first.


OK, I finished my measurements. :nerd:

The 4 dB difference between the Dynaudio Contour S 1.4 (fronts) and the Contour S C (center) stays the same no matter the distance from the speaker. The rear speakers from the same series (Contour S R) produce even less SPL at the same volume levels of pink noise (minus 7 dB). All speakers have (almost) similar sensitivity according to their specs (see above). 

My conclusion: Sensitivity is just but one factor in determining the SPL output at a given volume setting using pink noise. Stiil curious as to what the other factors could be but I can live with some unanswered questions... :dunno: that is, as long as it does not stand in the way of getting the right sound, and it doesn't.. :bigsmile:


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