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Old 5th December 2009, 17:55   #1
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Default Bridging an Amp - Is it wrong?

Hi all,

A friend of mine and myself are in the process of setting up a good audio system for his Fiat Palio Stile 1.6. GTX. Since we already have some equipment fom his previous car and plan on retaining them for his current install we do require a good subwoofer and components. The equipment we are retaining are the Pioneer 5850 headunit & the Sony XM-504Z 4-channel amplifier.

Eventhough I advised against it, my friend is inclined towards installing an active subwoofer inorder to save boot space. So off we went today to check out equipment at Auto Sonic on SV Road, Bandra West which is an authorised showroom for Blaupunkt products & Llumar sun film.

We started to check out the overpriced components (10k for a pair) & enclosed subwoofers (10k a piece) but he did not have stock of active subwoofers which are apparently 15k-18k a piece. We even auditioned the 10" enclosed subwoofer in my Swift through my JBL 301.1 monoblock and I really didn't find it as good as my 12" Infinity Reference. But for some reason, he started saying that the Blaupunkt had better sound quality that my current Infinity and that even my wiring was bad and was locally made. I am using Ground Zero wiring & RCAs :-) I did'nt say anything & just listened.

Bridging an amplifier is wrong as per Auto Sonic

Then we decided to tell him the set-up we wanted & how we would like the entire sound stage in the front of the car & plan on using 2 channels of the amplifier for the components & the other 2 channels to be bridged and drive the subwoofer & the rear coaxials to be driven by the headunit. We were taken aback when he got all annoyed & told us that bridging a 4-channel amplifier is absolutely wrong & those who recommend it don't know ANYTHING about music & car installs. He claims that a subwoofer MUST BE driven by a monoblock only & nothing else as the frequencies given out by a 4-channel amplifier are way different than that given by a monoblock and affects sound quality. His explanation was that a 4-channel gives out all frequencies, i.e. low & high while a monoblock gives out only low frequencies and hence affects sound quality Thes best part is, he said that amplifiers that are bridged have a shorter life span and have higher chances of breakdown.

We also asked him about if we need to have the doors & boot of the Palio damped & he told us that it was not required as the pannels & doors of the car have the best acoustic material.

Would request all experts to kindly give their views & feedback on the above as I am hearing about someone advising against bridging & damping for the first time.
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Old 5th December 2009, 19:28   #2
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Haha. Sounds like a fun outing for you and your friend. You guys seem to have met an entertaining gentleman.

Anyway, here are some facts -

An active sub and a passive sub differ only in the fact that an active subwoofer has the subwoofer driver, enclosure and the amplifier to drive the sub - all in the one unit. These are usually meant as solutions and probably work well at the entry level in international markets where folks would like to DIY rather than take expensive professional installation services. In my opinion, the best option is to choose the subwoofer driver and the enclosure for it separately, based on your tastes, and then get the appropriate amplifier to drive it.

There is nothing wrong with bridging an amp to drive a sub. If we went by the guy's logic, it would mean that nobody had subs in their cars till the late 90s, since Class D monoblock technology wasn't available in cars before then.
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Old 5th December 2009, 19:49   #3
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Originally Posted by Bass&Trouble View Post
Haha. Sounds like a fun outing for you and your friend. You guys seem to have met an entertaining gentleman.

Anyway, here are some facts -

An active sub and a passive sub differ only in the fact that an active subwoofer has the subwoofer driver, enclosure and the amplifier to drive the sub - all in the one unit. These are usually meant as solutions and probably work well at the entry level in international markets where folks would like to DIY rather than take expensive professional installation services. In my opinion, the best option is to choose the subwoofer driver and the enclosure for it separately, based on your tastes, and then get the appropriate amplifier to drive it.

There is nothing wrong with bridging an amp to drive a sub. If we went by the guy's logic, it would mean that nobody had subs in their cars till the late 90s, since Class D monoblock technology wasn't available in cars before then.
B&T to the rescue as always Yes it was a very entertaining outing today & I was amazed by what 'so called' professional installers are hired at audio stores. And mind you, this is an authorised Blaupunkt store!

What about the damping? Is it required for the Palio?
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Old 5th December 2009, 19:59   #4
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Originally Posted by Epic View Post
What about the damping? Is it required for the Palio?
Some cars require less, and some need more. Also depends on the quality of gear going in, the band they are intended to play, and the power running to them. Palio doors are indeed robust, so won't need too much especially for a basic setup. One can get away with bare minimum damping.
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Old 5th December 2009, 20:25   #5
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@B&T - Since my friend doesnt want to spend too much on the equipment and also retaining equipment from his previous car which is the Pioneer 5850 headunit & Sony XM-504Z 4-channel amplifier, we are planning to invest in only good components & a good sub. We plan to use the amp to drive the components & sub and connect the rear coaxials to the headunit. He listens to alot of rock & instrumental music.

So which components & sub would you suggest for the same to match the amp & setup? And would we require damping in this case?
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Old 6th December 2009, 02:11   #6
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That guy didn't quite exactly know what he was talking about, OBVIOUSLY
But, he did say some things which hold partially true.

Bridging an amplifier means you're effectively combining both the channels of that amp for higher single-channel output. However, you get an increased minimum impedance than the individuals channels. A 4ohm load on a bridged channel is like a 2ohms load on both of those channels. What some people might not know (and what that dealer might have experienced) is that you cannot drive a 2-ohm load on a bridged channel with most of the common amplifiers. When you do this, you're going above the rated specification. This is what would damage the amplifier because the protection circuitry is not equipped for this problem and the amp would keep trying to 'lift' the '40kg' weight when it is only equipped to lift '20kg'.

The only drawbacks of bridging an amplifier is that the amplifiers damping factor is reduced resulting in a loss of sound quality (some people believe that this loss is inaudible). And when an amplifier is bridged, its efficiency goes down by around 5-10% (this is alot of loss!).

Now, about the frequency, when you run a subwoofer from a full-range amplifier, the subwoofer is able to reproduce its range of frequency (mostly 30hz - 500hz), and the rest of the frequencies (500hz - 20Khz) are sent back to the amplifier and dissipated as heat (many amps have crossovers to undo this part). However, with the higher ranges of frequencies, you do not have alot of power involved, thus this loss is extremely low. Monoblocks are better compared to full range amplifiers because they are mostly d-class, and they concentrate only on one channel output which makes them use less construction materials and thus cheaper to produce.

I used to have a 4-channel amp dedicated to a pair of subs and they used to sound extremely hard, no problem. There is NO WAY that you cannot drive subs with full range amplifier and need a dedicated mono block for it. Monoblocks do have their advantages but they are not mandatory to get the job done.
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Old 8th December 2009, 12:30   #7
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the problem is that if you have equipment of sufficient quality which allows you to notice it then class D amplifiers are prone to quantization errors. You will hear this as a smearing of the sound ie as if the bass notes are slightly bloated and delayed (i sometimes get this when i use high quality subs with class D amplifiers) i tried a Morel Ultimo with a Phoenix Gold xenon x1200.1 and then i tried the same sub with my class A/B Phoenix gold xenon x200.4 which produces 1/3rd of the power when 2 channels are bridged

to be honest even thought the 200.4 only gave the sub 400 watts as opposed to the 1200 watts from the 1200.1 I preferred the sound quality from the 200.4 far more because it seemed far more pacy and detailed and it also had far more transient attack. Dont worry if you dont understand what i am talking about because the bottom line is that most of the time a well set up class A/B amp CAN sound better than an equivalent or better specced class D

which is one of the reasons why i did not get a monoblock for my subs in my new upcoming system even though those are more efficient and better into lower impedances and also far kinder to your battery and alternator but to me personally i dont like the sound of them. NOTE that these differences are so slight that you would have to concentrate to hear them or know exactly what you are looking for (nothing to do with having better hearing but its about knowing what to listen for)

as for this claim here

Quote:
His explanation was that a 4-channel gives out all frequencies, i.e. low & high while a monoblock gives out only low frequencies and hence affects sound quality
is he forgetting that you would be using a crossover and generally even if you use the one built into the amplifier those are at the pre-amp stage hence would be reducing frequencies before the amp reproduces them anyway. The amp would only play full range into bass speakers if you are using passive crossovers to reduce frequencies but nobody uses these for subs anymore unless they are experimenting with tri-mode usage so his argument here mostly falls flat

Quote:
Thes best part is, he said that amplifiers that are bridged have a shorter life span and have higher chances of breakdown.
as cvc2145 stated above he is partially correct in this mostly because of the impedances that you will be running in bridged mode hence it will definitely run hotter and heat is not friendly to electronic circuits hence you do reduce the lifespan but it also depends on the volume levels you use ie if you run flatout all the time and use the system as a ground pounder or if you are more into SQ and use powerful equipment but running them in a comparatively "idle" mode then you wont be straining the amplifier so much and its less of a factor

higher chances of breakdown is more likely if its a cheap low quality amplifier. If you do have a high quality amplifier it will take most things into its stride

Quote:
We were taken aback when he got all annoyed & told us that bridging a 4-channel amplifier is absolutely wrong & those who recommend it don't know ANYTHING about music & car installs
im sure most people on here telling you that there is nothing wrong with bridging an amplifier have a done substantially more installs than this gentleman has done

Last edited by naughty001 : 8th December 2009 at 12:34.
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Old 8th December 2009, 13:47   #8
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the only case when you shouldn't bridge an amp is when its already bridged internally ( for example, the amps inside your HU. You can't bridge HU channels). You usually cant bridge bridged amps

@ naughty - lets not paint all the monoblocks with the same brush. There are some Class AB monoblocks right ?

Last edited by greenhorn : 8th December 2009 at 13:51.
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Old 8th December 2009, 22:13   #9
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Ask the man to look up the old ORION HCCA Series 250 / 225 / 2150 etc
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Old 8th December 2009, 23:58   #10
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Quote:
There are some Class AB monoblocks right ?
no modern ones that i know of at the moment - and if you do find any those will be of the extremely rare variety.

Quote:
@ naughty - lets not paint all the monoblocks with the same brush
Dont get me wrong all i am saying is that i dont prefer monoblocks personally because i dont play the bass larger than life. there is absolutely no boom in my car and when i play the sub its still more about quality than output hence why i stick to class A/B amps. But i am by no means implying that all class D amplifiers are bad .... far from it because you will get lots of high quality class D amplifiers but i have had no need for those

BTW a class A/B amplifier bridged internally wouldnt be what i would term a monoblock anyway

Last edited by naughty001 : 9th December 2009 at 00:01.
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Old 9th December 2009, 13:02   #11
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Quote:
Originally Posted by naughty001 View Post
(i sometimes get this when i use high quality subs with class D amplifiers) i tried a Morel Ultimo with a Phoenix Gold xenon x1200.1 and then i tried the same sub with my class A/B Phoenix gold xenon x200.4 which produces 1/3rd of the power when 2 channels are bridged

to be honest even thought the 200.4 only gave the sub 400 watts as opposed to the 1200 watts from the 1200.1 I preferred the sound quality from the 200.4..the bottom line is that most of the time a well set up class A/B amp CAN sound better than an equivalent or better specced class D
Current Class D Amps do not compare well with Class A/B but as the state of the art improves I wont be surprised if they become as good as Class A/B. That said the real reason why Class D has found a niche in audio is becuase these amps create less heat and occupy lesss space (although I have seen some Class D amps that are almost as big as similar rated Class A/B amps).
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Old 10th December 2009, 20:42   #12
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Originally Posted by greenhorn View Post
the only case when you shouldn't bridge an amp is when its already bridged internally ( for example, the amps inside your HU. You can't bridge HU channels). You usually cant bridge bridged amps

@ naughty - lets not paint all the monoblocks with the same brush. There are some Class AB monoblocks right ?
The sub-channel on the Bosto GT50 is a class AB as are all the other channels. Do I love my amp or what?
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