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Discussion Starter #1
My Carvin HD1800 croaked. There's a loud hum. I think it means that something came unsoldered.

I'd like to replace it. It lived in the closet because of the fan noise, and I'd rather have one without a fan.

Here's my existing configuration. The IB sub has four 18" drivers. Each driver is a nominal 8 ohms, and they are arranged to present a single 8 ohm load. The Carvin is spec'ed to deliver 1200W RMS continuous into 8 ohms.

The Sub
IMG_1024.jpg

The channel level control on the Carvin was set to -17dB. In theory, I'm only using 14% of the available power. Does this mean that I only need 170W plus plenty of headroom? Correct me if I'm wrong.

I am looking at the Behringer Reference Amplifier A500. It is spec'ed to deliver 375W RMS into 8 ohms / 1 kHz @ 1% THD. $199. No fan.



Please share your thoughts. Any better suggestions?
 

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Here's my existing configuration. The IB sub has four 18" drivers. Each driver is a nominal 8 ohms, and they are arranged to present a single 8 ohm load. The Carvin is spec'ed to deliver 1200W RMS continuous into 8 ohms.

The channel level control on the Carvin was set to -17dB. In theory, I'm only using 14% of the available power. Does this mean that I only need 170W plus plenty of headroom? Correct me if I'm wrong.
If power delivery and gain adjustments were 100% linear you could probably make that statement, but neither of those really are so you can't actually correlate it that manner. And for dynamic swings in the source material you want/need additional amplification, so some 'extra' is always a good idea.


I am looking at the Behringer Reference Amplifier A500. It is spec'ed to deliver 375W RMS into 8 ohms / 1 kHz @ 1% THD. $199. No fan.
Do they list the THD in-band for your application (which I assume is 100Hz on down)? Reason I ask is most people construct an IB because they favor high quality sound, but using a low-end amp with 1% THD runs counter to that ideal. You may end up diminishing the experience if you go that route.
 

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There are several models of old BGW amps that are fanless. You won't get the kind of power output the Carver was delivering, but they're clean and built like tanks.
 

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As J-Man mentioned, the gain setting has no bearing on the power output. It’s a combination of that plus the level of the input signal. If your gain setting was really low it could indeed mean that you weren’t using much of the amp’s capabilities, but it could just as easily mean you were feeding it a really hot signal.

Might take a look at Carvin’s DCM-xxxxL series amplifiers. I’ve been using one for a number of years with no issues. It does have a fan, but it’s quiet enough that I can’t hear it at my listening position ~12 ft. away.

I am looking at the Behringer Reference Amplifier A500. It is spec'ed to deliver 375W RMS into 8 ohms / 1 kHz @ 1% THD. $199. No fan.
The specs aren’t as good as you might think. Carvin rates their amps broadband 20Hz – 20 kHz, while the A500’s power output is only given at 1 kHz. You can be certain that Carvin’s DCM2000L’s 325 watts @ 8-ohms will get more output that Behringer’s 375 watts.

Regards,
Wayne
 

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Discussion Starter #5
I don;t really want to do Carvin again since mine just died.

What do you think of this one?

Alesis RA500
  • Rated output: 8 ohms, bridged mono mode - 500 watts RMS
  • Signal-To-Noise Ratio: 105dB, 22Hz-22kHz bandwidth referenced to rated output
  • Frequency Response: 10Hz – 70kHz +0, -3dB
  • Damping Factor: 200
  • Slew Rate: 120 V/μs (bridged mono)
  • Input Sensitivity: +4dBu (1.23 V) for rated output with input control at maximum
 

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To me that seems like a better option than the Behringer. Very solid spec's for the price.
 

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Discussion Starter #8 (Edited)
So you were running the Carvin bridged?
Yes, I enabled bridging and ran a single cable from the amp to the woofers.

The four woofers are arranged in series/parallel, like this:

 

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Discussion Starter #9
Any model numbers to look for?

There are several models of old BGW amps that are fanless. You won't get the kind of power output the Carver was delivering, but they're clean and built like tanks.
 

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Discussion Starter #10
If power delivery and gain adjustments were 100% linear you could probably make that statement, but neither of those really are so you can't actually correlate it that manner. And for dynamic swings in the source material you want/need additional amplification, so some 'extra' is always a good idea.
Yeah, I started thinking about that some more after I wrote it. Running with the amp gain set to -0dB would probably not correspond to the maximum possible continuous output on some "demanding" program material.
 

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Discussion Starter #11 (Edited)
http://www.baudline.com/erik/bass/xmaxer.html
http://myhometheater.homestead.com/splcalculator.html

  • 4 number of drivers
  • 18 driver diameter (inches)
  • 20 Hz
  • 15 Xmax (mm)
The maximum output for my system at 20 Hz is 116.9 dB SPL @ 1m at Xmax.
  • Speaker Sensitivity: 90.7 dB/watt @ 1m
  • Distance: 1 m
  • 116.9 dB SPL at listening postion
The required amplifier power to reach that maximum output at 20 Hz for my system is 420 Watts.

The required amplifier power to reach an LFE peak of 115 dB at my listening position is 900 Watts.
My sub could do that at 25 hz before bottoming out.

Thoughts?
 

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Discussion Starter #12 (Edited)
I think I found the answer to how much power I need.

My main speakers have a specified Maximum SPL of 111 dB.
At the listening position of 14 feet that is 98.4 dB.
This is as loud as my system can play cleanly.

This is reference level -6.6 dB, about where I like it.

The sub should be able to play 10 dB louder than my mains.
That's 108.4 dB at the listening position.

Calculations show that Required Amplifier Power = 270 Watts.

This assumes +6 dB from locating the sub in a corner. Is that right?
 

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Yes, I enabled bridging and ran a single cable from the amp to the woofers.

The four woofers are arranged in series/parallel, like this:

Seems I’ve heard it mentioned that bridging an amp puts more strain on it than running it in stereo. And loading down an amplifier channel with multiple drivers for sure makes an amp work harder, even if they’re configured for the correct load.

Thus, the configuration with which you were running the Carvin with may have contributed to its demise. I don’t see where running it bridged got any advantage compared to stereo operation. According to the manual I found online, the HD1800puts out 1200 watts @ 8-ohms bridged. That output was divided out between the four speakers, which means each would only “see” 300 watts. At 4-ohms in stereo operation, the amp puts out 600 watts, which would be divided between two off the speakers for – 300 watts each.

What is that amp, at least 8-10 years old? Carvin makes decent amps, but they certainly aren’t on the same level as the best from Crest, Crown or QSC. In any event, I doubt the two amps you’ve mentioned would last even as long as the Carvin did. They aren’t exactly heavy-duty amps.

By all accounts I’ve seen the BGW amps are bulletproof, but expensive. However they also are under-appreciated, which means they sell used for cheap. There was a thread here recently, you might dig around for it. For something assuredly more robust than the Carvin, but probably much cheaper than the BGW, you might check into Yamaha’s PxxxxS amplifiers. You can find a user evaluationhere.

Regards,
Wayne
 

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The 100 series, 200 series, and 300 series all lack cooling fans... instead they have big aluminum heat spreaders on the sides.

There's an auction up for a 7500 that has labeling indicating it will put 600W into an 8Ω bridge. Also fanless. $170+shipping
 

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all right somebody else from Richmond, great rainy day isn't it? Just my input I know you mentioned fan less amp and it seems you want to improve w/o breaking the bank. Look into a Behringer Inuke nu3000 be warned you have to replace the fans I used Noctua RF-88 think around 20 bu there is cheaper it took maybe 10-15 minutes pretty easy. This amp will play at 2 ohms all day long. Mine is 10ft away from where I sit and I cannot hear it when the amp is on. The amp is rated at a max of 3000w but trust me there is no way but for the money people swear by it. Depending on where you look whether local like Sam Ash Guitar Center etc. or what you find online it does not hurt to ask for a discount. The average price is 260? but I feel be asking foe a better deal 240 or less is possible. You may have already decided but in any case glad to see someone else from Richmond.
 

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Discussion Starter #16
The conclusion to the tale:

I bought the Alesis RA500 because it was a cheap option and easily returnable to Amazon. The old Carvin HD1800 was in the closet, and I put the new amp in the TV console with my other equipment. I took about two hours to get the everything rewired through the crawlspace. I turned on the system and...

The same loud hum. It turns out that the Carvin amp was not the problem. I had a bad ground loop problem. But from what?

I recently got cable! It had not occurred to me that getting cable could be the cause of such a big problem, but it was. So I bought this cable ground loop isolator and it worked like a charm. Totally fixed the problem.



It took another two hours to rewire everything back the way that it was. I returned the new amp.

All's well that ends well.
 
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