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Class D Switching Power Amplifiers and Power D/A conversion

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Old 5th July 2011, 06:02 PM   #1
Matty is offline Matty  Germany
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Default Class D in an active 3 way system

Which is the best Class D board? This question has been asked quite often in this or in other forums. An it has been answered even more often. So with a little effort, it is quite easy to find a bunch of reviews for the most Class D boards on the market.

But the most reviews rate the boards as a fullrange amplifier.

If being used in a multi way system for only a restricted frequency range, the quality valuation of a board may come up quite different. There is no need for a powerful bass, when driving only the tweeter of a system. How important is the resolution or whatever if the board is only used with a (sub)woofer?
So it seems quite obvious to me to select 'specialists' for the different ways of an active systems to get the optimal result. But will different Class D boards automatically blend with each other? Are there important aspects to be considered?

I'm looking for an optimal Class D configuration for the following system:

- Oris horn with BMS4952ND (modified)
- BD15 bass (BD-Design)
- crossover frequency ~270Hz
- Both drivers have a very high sensitivity so there is no need for lots of Watts.

As it is a 3 way system (BMS4592nd is a coax) and the Class D modules are intended to be placed on the back wall of the speakers, I would ideally need three mono boards or one mono and one stereo board on each side.

So, what are your suggestions, which combination of boards would you use in such a configuration?
I'm really looking forward to hear your recommendations

Cheers,
Matthias
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Old 5th July 2011, 06:59 PM   #2
matsj is offline matsj  Sweden
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Take a look at Abletecs Alc0180 for the coax. It's a stereo amp modul with integrated powersupply. And maybe their bigger modules for the low. I have the Alc0180 to my diy.

Mats
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Old 5th July 2011, 07:10 PM   #3
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Default Just use a good full range amp

Well, I have been considering the same question and have come to the conclusion that it doesn't matter, and if you are going to go fully active 3 way with class D you might as well just go for a single design of decent quality full range amp everywhere and be done with it. My reasoning is as follows:

a) A good amp is a good amp and will perform well across the full audio spectrum. Nobody (pure subwoofer duty aside) is going to specifically design a class D to be poor at one end or middle of the audio spectrum, so if there is such an amp it is pretty much by definition a bad design. Now if it is a bad design it probably has other faults as well as being poor at one side of the audio band so why bother with it?
b) Leaving aside the fact that nobody anywhere will have tested a range of amps specifically for the pass band you are going to use what will it mean when some kind sould gives a report of x vs y vs z amps and which parts of the audio band they are best at? I suspect it will largely mean that the a,ps responses aren't flat and have more gain in their 'stronger' area of performance, this of course is useless to us if we are driving them separately and give appropriate gain to each driver. Alternatively the more discerning audiophile might not just go by apparent loudness of the amps on highs and lows but might actually detect a qualitative difference, what then done this mean? I submit it is likely to mean the speakers used have some particularly nasty response characteristics at those points and the perceived sound difference is likely to be how well the amp can handle a nasty load. Now an amp that can handle a nasty load meets another quality of 'good amps' and gets an honourable mention for use all across the frequency band.
c) Possibly there is mileage in using lower powered amps for highs to mids to bass, but why? In general the claims seem to be the higher power class D amps tend to sound better so why use a lower powered one? Especially as that is likely to require different power supply voltages so complicating the design.

Note this is all in the context of using class D amps throughout. Now if we were using valve amps I would definitely want to optimise for each driver - at the minimum using optimised transformers for each. Staying more closely to home there is the question of whether it would be a good idea to use a class A amp for the treble where less power is required and it is more practical. That's a very different question so I'll just dodge it
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Old 5th July 2011, 07:46 PM   #4
ssanmor is offline ssanmor  Spain
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We think we have a very suitable combination for three-way systems based on Sonora Combos and S250 modules with no additional power supply (the Combo can supply external modules). If you want more information, contact us at info@coldamp.com
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Old 5th July 2011, 08:02 PM   #5
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For the bass, there is a clear advantage in having a specialized class d amp. You don't need high switching frequency. This simplifies the the amp and raises the efficiency even further.

I have some NXP 8950TH based amps, and they sound really good, especially for bass

You can get some very interesting amps based om NXP and T.I. chips here
Amplifier store Small Orders Online Store
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Old 5th July 2011, 08:57 PM   #6
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Quote:
Originally Posted by Kjeldsen View Post
For the bass, there is a clear advantage in having a specialized class d amp. You don't need high switching frequency. This simplifies the the amp and raises the efficiency even further.

I have some NXP 8950TH based amps, and they sound really good, especially for bass

You can get some very interesting amps based om NXP and T.I. chips here
Amplifier store Small Orders Online Store
Yes, and if you are looking to supply very large amounts of power for professional this is clearly important or at least an item worthy of consideration. But if if we are talking of domestic contexts (which is my focus and also how I took the OP) is extra efficiency in the bass amplifier above normal class D really important, or even important at all?

Now, are you saying that one of specialised bass/sub driver amps will actually sound better than a good full range design? If so I'm prepared to listen ...

Edit: I should also say that I am thinking of driving active speakers within their 'normal' range where they provide an essentially flat response. Where a system is engineered so bass frequency response depends heavily on equalisation and bass power requirement is abnormally high (compared to music power distribution) then yes, even in a domestic context, supplying very large amounts of power to the bass becomes an issue and I can see the benefit of different amp design.

Last edited by goosewing; 5th July 2011 at 09:06 PM.
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Old 5th July 2011, 09:02 PM   #7
Matty is offline Matty  Germany
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@matsj:
Got me.
The first response and yet a product I never heard about ...
Do you have some more information? Your experiences, price, where to get?

@goosewing:
I agree partly to your arguments, especially the increased complexity of the PSU when using different boards. Otherwise - a Tripath 2020 e.g. has absolutely enough power for the bms4592nd for normal volumes in my living room, but I would not use it for the bass. Sure I could use more powerful boards for mids and highs too, but basically more power means more expensive with no additional benefit.
Btw that's the combination I'm using right now, a Tripath TA2020 by Arjen Helder together with an Hifiakademie PowerAmp. But I don't wont to keep this combination, especially because the PowerAmp is a stereo board which therefore would have to stay between the speakers.

@ssanmor: Considering the 'integrated overall concept' aspect, your solution looks very interesting. I think I will take a look at it.
Anyone who shares his experiences with these modules here?

Cheers
Matthias
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Old 5th July 2011, 09:05 PM   #8
AP2 is online now AP2  Italy
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Quote:
Originally Posted by Matty View Post
Which is the best Class D board? This question has been asked quite often in this or in other forums. An it has been answered even more often. So with a little effort, it is quite easy to find a bunch of reviews for the most Class D boards on the market.

But the most reviews rate the boards as a fullrange amplifier.

If being used in a multi way system for only a restricted frequency range, the quality valuation of a board may come up quite different. There is no need for a powerful bass, when driving only the tweeter of a system. How important is the resolution or whatever if the board is only used with a (sub)woofer?
So it seems quite obvious to me to select 'specialists' for the different ways of an active systems to get the optimal result. But will different Class D boards automatically blend with each other? Are there important aspects to be considered?

I'm looking for an optimal Class D configuration for the following system:

- Oris horn with BMS4952ND (modified)
- BD15 bass (BD-Design)
- crossover frequency ~270Hz
- Both drivers have a very high sensitivity so there is no need for lots of Watts.

As it is a 3 way system (BMS4592nd is a coax) and the Class D modules are intended to be placed on the back wall of the speakers, I would ideally need three mono boards or one mono and one stereo board on each side.

So, what are your suggestions, which combination of boards would you use in such a configuration?
I'm really looking forward to hear your recommendations

Cheers,
Matthias
Hi, I'm glad that someone speaks of "resolution" in the class D amp . apparently, we call this phenomenon "resolution" (the instruments in the range of high frequencies are not clearly defined, this sum is an odd intermodulation, typically after 60% modulation. I have studied this "phenomenon" that is independent of the carrier frequency high. unfortunately you can not measure this error and it is present in 90% of the amplifiers I've heard. (companies who need to choose the amplifier for the driver, know well this problem in fact, many are still going on with the class AB drivers)... No, it's just that I wanted to understand what it depends on this low "resolution". Therefore, it is possible that an amplifier with excellent audio measurements, the high frequency sound is crap . obviously depends on whether the listener is able to understand. or all amplifier is very good, very nice sound.

Regards
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Old 5th July 2011, 09:09 PM   #9
Matty is offline Matty  Germany
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Quote:
Originally Posted by goosewing View Post
But if if we are talking of domestic contexts (which is my focus and also how I took the OP...
Thats exactly what I'm reflecting on. Getting the right/best products for the context they are going to be used.
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Old 5th July 2011, 09:19 PM   #10
Matty is offline Matty  Germany
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Join Date: Sep 2006
Quote:
Originally Posted by goosewing View Post
Staying more closely to home there is the question of whether it would be a good idea to use a class A amp for the treble where less power is required and it is more practical. That's a very different question so I'll just dodge it
Perhabs a hint? We can change the forum if you want or send me a PN.
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