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#225994 - 10/19/08 09:12 AM I just blew my amp (Denon 4308CI) now what?
peenerhead Offline
buff

Registered: 10/19/08
Posts: 44
OK here's the setup.

Denon 4308CI Amp, 4 Axiom M80v2(2 on Front A)(2 on Front B), VP150 Center Channel, 2 QS8 Surround (Have 2 more still in box for Surround Back but not hooked up yet), HSU Research VTF-3 MK3 Subwoofer, 10 awg wire to all speakers. Sub is wired preout from amp.

I've had this amp for a little less than 1 year. Occasionally, I get the chance to JAM when no one is home. Well, Friday was one of those days..... and after a round of trying to crush beer cans with sound waves - my amp shut off. The amp is dead. Still under warranty, so I took it back. They said 3-4 weeks for repair/replacement. They gave me a Denon 2809CI as a loaner.

Anyway, I was concerned with the lack of power from the 2809 I started to wonder if the M80s could be rewired for 8 ohm so that I didn't blow the loaner amp. So I took one of the M80s and remove the speaker wire and jumper clips. I grabbed my Fluke to get am Ohm reading and was surprised to find the the upper posts had a resistance of 9.2 Ohms and the bottom post had a resistance of 3.2 Ohms.

Before I got the resistance reading my thought was to wire the upper and lower posts in series with each other by jumping the lower(-) to the upper(+) and connecting the speaker wire to the lower (+) and upper(-). But after getting a different resistance reading between the upper and lower posts I am assuming that the internal wiring of the M80s is not the way I thought it was. I thought that each pair of binding posts were wired to 1 woofer, 1 mid-range and 1 tweeter.

Any and all comments and suggestion are welcome. I am looking for information on internal wiring of the M80s and possible setup changes that might help the loaner amp survive and improve performance (beer can crushing capability) when the 4308 comes back.

Thanks in advance for any help.
PEENERHEAD
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#226012 - 10/19/08 10:55 AM Re: I just blew my amp (Denon 4308CI) now what? [Re: peenerhead]
michael_d Offline
connoisseur

Registered: 07/23/04
Posts: 3822
Loc: Up yonder
What you are essentially doing is running two M80’s in parallel off of one amp. There’s no way the 4308 will carry that load (2 ohm), which is why it blew. For now, run one set of M80’s with the loaner and don’t get crazy with the volume control. If you really want or need to run twin M80’s in parallel, you should pick up an outboard two channel amp that will support the load. Use the 4308 as a pre/pro for the R/L channels. Be prepared to shell out some serious coin for an amp that will drive a 2 ohm load.
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#226014 - 10/19/08 11:14 AM Re: I just blew my amp (Denon 4308CI) now what? [Re: michael_d]
myrison Offline
connoisseur

Registered: 02/03/08
Posts: 1898
Loc: Austin, TX
These amps aren't necessarily pretty, but they'll do the job if you need something that will drive a 2 ohm load. (700 watts into 2 channels at 2 ohms)

(Plus, it's remarkably cheaper than continuing to blow out 4308s) ;\)

Crown XTi 1000 Amp

Jason
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#226016 - 10/19/08 11:18 AM Re: I just blew my amp (Denon 4308CI) now what? [Re: michael_d]
peenerhead Offline
buff

Registered: 10/19/08
Posts: 44
Sorry, I should have explained my setup better. I have the second set of M80s on the Amp Assign. Electrically, I thought that this would control each pair individually (4 ohms) rather than in parallel (2 ohms)please correct me if I am wrong.

On the question of the different Ohm readings for top and bottom binding posts, are the readings I am getting normal? If so how are the speakers wired internally? If the reading is not normal what should the correct readings be? And finally is there a way to rewire the speaker to get a higher resistance?

I have an old Harman Kardon PA2400 in storage I think it was rated @ ~200 wpc if I recall correctly. Would this be sufficient to power the M80s ? I use to run 4 Cerwin Vega VS150s on this amp and never had a problem.

Thanks
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#226019 - 10/19/08 11:32 AM Re: I just blew my amp (Denon 4308CI) now what? [Re: peenerhead]
Ken.C Online   content
shareholder in the making

Registered: 05/03/03
Posts: 17696
Loc: NoVA
The top posts are to the 2 mids and 2 tweets, the bottom posts are to the 2 woofers.
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#226049 - 10/19/08 02:10 PM Re: I just blew my amp (Denon 4308CI) now what? [Re: Ken.C]
myrison Offline
connoisseur

Registered: 02/03/08
Posts: 1898
Loc: Austin, TX
I'm still confused on how you have things wired. (which is likely my fault, not yours)

In the first post, you said they were connected to Front A / Front B. I have the 3808 and don't remember such an option. I took a look at the 4808 manual to see if there was a difference and while there are some different connection options for multi-zone playback, I don't see this specific option there either.

In your second post you said you have the second pair set up on "amp assign." In the 4808 manual, there is an option listed to have one set of front speakers designated for multi-channel listening, and a second set of speakers for direct/stereo modes. This allows you to have 4 front speakers, 2 of which are active depending on what mode you are in (surround versus stereo). The manual lists this option in the section having to do with bi-amping and bi-wiring your mains.

I can't find anywhere in the manual where they give the option of running both sets of main speakers at the same time. The only settings I know of on the 3808/4808 to run 4 speakers through 2 channels is on the Surround A / Surround B option, which I imagine they support since typical impedance of surround speakers is fairly high.

Can you elaborate on which channels you are using to run your 4 M80s and what mode you are listening in (or were listening in) that runs all 4 at the same time?

Jason
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#226052 - 10/19/08 03:38 PM Re: I just blew my amp (Denon 4308CI) now what? [Re: myrison]
peenerhead Offline
buff

Registered: 10/19/08
Posts: 44
I actually have the 4308 not the 4808 (don't know if there are differences). The Amp Assign outputs allow me to send a 2 channel signal to a second set of speakers (what I referred to as Front B since that's where they were). This could be done by wiring to the Surround B/Amp Assign or Amp Assign 2. I believe I had my Front B speakers wired to Amp Assign-2 but can't be sure. Since I don't have the amp at the moment, I don't recall exactly what the setting was in the menu to activate both pairs. I will have to dig out the manual to check, but i believe it was the bi-amp setting that allowed me to do this.

I was able to get sound from all 4 front speakers in any mode as I recall. Any surround sound mode or 5/7 channel stereo played fine.
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#226053 - 10/19/08 03:43 PM Re: I just blew my amp (Denon 4308CI) now what? [Re: myrison]
jakewash Offline
shareholder in the making

Registered: 12/26/03
Posts: 10394
Loc: Calgary, Alberta
Sounds to me like a faulty amp to begin with or speakers incorrcetly hooked up, as Jason has eluded to a bit of confusion with the posts.

I have run ~2 ohm loads as a center on both my 1804 and now my 3808, with no problems, albeit not cranked right up but around 80db.
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Jason
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#226057 - 10/19/08 06:07 PM Re: I just blew my amp (Denon 4308CI) now what? [Re: jakewash]
myrison Offline
connoisseur

Registered: 02/03/08
Posts: 1898
Loc: Austin, TX
Peenerhead - (love that name)

4808 was a typo by me... I meant 4308 (and that was the manual I looked at).

If Jakewash is right that they can handle 2-ohm loads then I guess it doesn't matter how they were hooked up, though if the speakers were hooked up to different amp channels, it definitely shouldn't have mattered as I'd think it would be quite capable of running 4-ohm loads on separate channels.

Let us know if you're able to crank it back up when you get the new one.
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Epic 80-800: HG Cherry | HT Pics

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#226064 - 10/19/08 07:55 PM Re: I just blew my amp (Denon 4308CI) now what? [Re: myrison]
Wid Offline
axiomite

Registered: 06/22/03
Posts: 6717
Loc: The Peoples Republic of Il.
We all know no one uses that kind of power, one watt is more than enough
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"A fear of weapons is a sign of retarded sexual and emotional maturity." Sigmund Freud


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