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Old 22nd February 2012, 04:41 AM   #1
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Default Class D Amplifier Choice

Decided to bite the bullet and go active on my new speaker project and would just like some advice on my choice of Class D amplifiers.
Currently I am using the Rotel RB-1092 and RB-1091 (1000w/500w @ 4/8 ohm) Class D amps and I am quite happy with the definition they provide to my mains and centre speakers.
Obviously going active means I need far more channels, but not as much power per channel, and I also read going active means needing even less power because it doesnít have to force its way through an inefficient passive crossover. So figuring I could go either 3 or 4 way on each 5 channel amp.

So how much is enough?
I got a price on a couple of the Rotel RMB 1565 (5 * 200w/100w @ 4/8 ohm) Class D amp and AFAIK the use the same technology of their bigger brothers.
The next step up is the RMB 1575 at twice the power but more than twice the price at an RRP of $2,999ea Vs $1399ea for its smaller brother.
I realise that I havenít mentioned what type of music I listen to or how loud but generically speaking in your opinion would a RMB1565 cut it per speaker?
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Old 22nd February 2012, 09:02 AM   #2
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First of all. Keep the Rotels. Have a look here : Amplifiers | Hifimediy .
I use them without problems. Some basic knowledge & you can install them by yourself. Sound is great without modifications. But do not expect miracles like the rotels you have.

Quote:
Originally Posted by Silent Screamer View Post
Decided to bite the bullet and go active on my new speaker project and would just like some advice on my choice of Class D amplifiers.
Currently I am using the Rotel RB-1092 and RB-1091 (1000w/500w @ 4/8 ohm) Class D amps and I am quite happy with the definition they provide to my mains and centre speakers.
Obviously going active means I need far more channels, but not as much power per channel, and I also read going active means needing even less power because it doesnít have to force its way through an inefficient passive crossover. So figuring I could go either 3 or 4 way on each 5 channel amp.

So how much is enough?
I got a price on a couple of the Rotel RMB 1565 (5 * 200w/100w @ 4/8 ohm) Class D amp and AFAIK the use the same technology of their bigger brothers.
The next step up is the RMB 1575 at twice the power but more than twice the price at an RRP of $2,999ea Vs $1399ea for its smaller brother.
I realise that I havenít mentioned what type of music I listen to or how loud but generically speaking in your opinion would a RMB1565 cut it per speaker?
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Old 22nd February 2012, 10:08 AM   #3
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I was planning on keeping the RB-1092 and RB-1091 for something like a seriously big subby if I donít need them for the main speakers, I was merely looking for a couple of replacement amps to use on the multiple drivers in the mains of the speakers I am about to build.
I donít have a problem with the price of the multi channel amps I listed I was just wanting to know if it was enough power for individual drivers to function optimally i.e. do I need a bigger amp to keep out of the range of distortion?
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Old 22nd February 2012, 10:57 AM   #4
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Then look at the specifications of your speaker drivers you are going to use. Take the maximum peak value in watt that they can withstand & choose the amp accordingly. I have a system in PA mode. It has 2 seas tweeters (6ohm/90watt) & 2 pairs of seas midwoofers (they are a 4ohm load paralleled /80watt max). I used 2 stereo class-d 2*100 watt each, so i have about 10watt more power for the tweeters & 20 for the midwoofers.
If you get higher powered amplifiers you will have control over power & will always know your limits because speakers don't burn easily with more power.
If you buy less powered amps (lower than max power of every speaker unit) your speakers will burn easily if the amp is pushed louder to its limits & will start distortion because of clipping.

Quote:
Originally Posted by Silent Screamer View Post
I was planning on keeping the RB-1092 and RB-1091 for something like a seriously big subby if I don’t need them for the main speakers, I was merely looking for a couple of replacement amps to use on the multiple drivers in the mains of the speakers I am about to build.
I don’t have a problem with the price of the multi channel amps I listed I was just wanting to know if it was enough power for individual drivers to function optimally i.e. do I need a bigger amp to keep out of the range of distortion?
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Old 22nd February 2012, 11:12 AM   #5
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Check the 125ASX2 modules sold @ the Vendor area.
Not exactly Hypex quality but much better than your average Tripath amp.
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Old 24th February 2012, 12:08 AM   #6
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WOW! It sounds like Mr. Screamer is running his own Majestic sized theater. There are now diy amplifier boards available that could help, and some of these are not ridiculously expensive, though once you add in the necessary power supplies, you are still talking about $300US or so for 500-600W RMS into 4 ohms, somewhat less power into 8 ohms. I understand that the Rotels cost on the order of $1500 each, so clearly cost is little object here.

Once this setup is completed, perhaps Mr. Screamer can turn up the volume a little so that I can hear how it sounds...right here in Easton, PA!
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Old 24th February 2012, 12:52 AM   #7
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Itís all kind relativeÖ If I buy a top shelf digital crossover for ~ $4k (which is seriously on the cards right now) and I buy another 3 x Rotel RB-1572 amps (2 channel Ė 500amp @ 4 ohm - RRP $1299ea) ~$3k once I hit them up for a hefty discount.

Weíre talking $7k for the electricals, say another $4k on drivers for the speaker cabinet and a few bucks on wood. For ~$11k I bet they blow the Cremonaís I currently have into the weeds.

Since there is so much money tied up, really saving a couple hundred dollars per amp really doesnít make a lot of economic sense when I donít have the necessary skills for the DIY side of the amp electronics.

Safer to stay with what I know, rather than risk blowing up expensive parts I canít fix myself.

Wait till in burn the drivers in and Iíll crank it up for ya!
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Old 24th February 2012, 04:23 PM   #8
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Yup, makes sense. I'll keep an ear peeled for loud but euphonious sounds emanating from Down Under. Best of luck with the project.
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Old 25th February 2012, 01:24 AM   #9
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Thanks stujonesmd I joined the forums with one idea in mind and it has evolved into something completely different. Deciding to go active has really opened up a whole new world of ideas. I have reverted back to a layout idea I had back in the late 90ís, but there is digital technology that now exists to make it possible.
As the project starts to solidify I am getting excited about what the outcome is going to sound like, I think going active will take me to a whole new level.
As for amps I think I am probably best off waiting until I decide on driver direction and then just buy something that is big enough to do the job with plenty of head room rather than trying to guess what I need now.
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Old 25th February 2012, 08:33 PM   #10
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Sounds very reasonable, as well as potentially VERY loud! I sometimes wish I had resources similar to yours to invest in sound equipment, but suspect my aged ears, tho thoroughly spoiled by past experience, might not notice the difference.
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