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Old 30th September 2011, 02:46 PM   #1201
AndrewT is offline AndrewT  Scotland
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Quote:
Originally Posted by chrapladm View Post
I think so Bob. Because 15-20db would be insane for me. I was told along time ago to use rms power and atleast an amp that can deliver 3db more for headroom. SO I would need 5000 watts per speaker for my subs and to have 17.5-10db more WOW!!! that would be a LOT of power. I thought I was crazy. But I understand what you are saying Andrew T.

Now my speakers I am building Bob will be very efficient. A similar speaker combo has a 105db rating.
if you are proposing to use 105dB/W @ 1m speakers then simply subtract 10 to 15dB from my earlier example.

-15dB ref 5000W = 158W.
But, how did you come up with 5kW?
5kW into 88dB/W @ 1m speakers would give ~120dB @ 2.5m listening distance for a stereo pair. That is insane !

95dB speakers and 100W of power is more than most would want/need for any domestic occasion.
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Old 30th September 2011, 02:57 PM   #1202
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Covering the last octave has always been about displacement but I also need wattage. So for my subs I need rms power. (2500 watts) Then with an added L/T circuit I will need more wattage but will just stick with 2500. Then wanting to have 3db headroom that puts me at 5000 watts. Now I will have amps that will coast by 95% of the time. Transients aren't that long but I have enough power to reach all peaks in reserve power at reference volume plus.

Now for the 105db speakers thats a whole other game.
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Old 30th September 2011, 03:51 PM   #1203
bcmbob is offline bcmbob  United States
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I don't use the MyRefs with the Denon 7.1. That is a completely different system with its own internal power amps. I switch speaker leads to the DIY LM3886 builds when I listening to two channel stereo music. I rediscovered the simplicity and accuracy of straight-up stereo once I combined the MyRefs with my current speakers. I now feel most of the DSP action/options in receivers is really unnecessary when the "amp - speaker" combination is a proper match and of sufficient quality. The "Sunflower" speakers I built are open back for the mid-range and provide all the room ambiance I need - reflects the production goals of the source material.

In "Audiophile" listening the only thing I might add form time to time is the Carver C-1 preamp with its "Sonic Hologram" capabilities.

If you want to develop a 5/7.1 system with your own builds, there is a thread dedicated to that concept elsewhere on this forum.
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Last edited by bcmbob; 30th September 2011 at 03:55 PM.
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Old 30th September 2011, 04:05 PM   #1204
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Bob is the 3886 not a good place to start for a multi channel amp?
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Old 30th September 2011, 07:40 PM   #1205
bcmbob is offline bcmbob  United States
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It's probably as good a place as any and depends on your choice of configurations - 5 mono-blocks, self-contained etc. Check on the Chipamp Photo Gallery to see what others have done..
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Old 2nd October 2011, 09:53 PM   #1206
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This is how the boards are fixed to the heatsink. I should've use a less thick clamping bar, but that's what I had in hand.
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File Type: jpg 2.jpg (317.0 KB, 254 views)
File Type: jpg 3.jpg (310.6 KB, 248 views)
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Old 2nd October 2011, 10:36 PM   #1207
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All base panel drilling done (12mm thick aluminium, military spare), all the boards with their screws, and a sexy traslucent panel showing the RIFAs
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File Type: jpg 5.jpg (328.0 KB, 237 views)
File Type: jpg 6.jpg (164.1 KB, 92 views)
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Old 3rd October 2011, 04:30 PM   #1208
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You and those Rifa's. If I had them I would show them off too. We just do not have a full compliment supplier here in the U.S. at affordable prices for those monsters. Even if you find them overseas the shipping will kill you.
Things are looking really nice so far. How you liking all that aluminum tapping? Ain't it fun.

Tad
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Old 3rd October 2011, 05:07 PM   #1209
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Quote:
Originally Posted by tryonziess View Post
You and those Rifa's. If I had them I would show them off too. We just do not have a full compliment supplier here in the U.S. at affordable prices for those monsters. Even if you find them overseas the shipping will kill you.
Things are looking really nice so far. How you liking all that aluminum tapping? Ain't it fun.

Tad
I got the RIFAs from Elfa.se, P/N is 67-685-92. The cost killed me, you're right. But because the amplifier is being made for a friend, he pays :

Net value................ 250,80 EUR
Freight cost............. 20,00 EUR
Taxes.................... 67,70 EUR
---------------------------------------
Gross value.............. 338,50 EUR


I managed to don't make any tapping (lucky me) I made "fake holes", don't know the name in english. See the attached picture.
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Old 4th October 2011, 09:14 AM   #1210
AndrewT is offline AndrewT  Scotland
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spot face, or recess, or probably quite a few others would describe.
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