2 CH. Amplifier... #1 ch> Center channel...#2 ch> passive sub

KyleGS · 10-24-2003, 09:13 AM

Hey guys- Here's my set-up:
JBL Studio's
H/K 510
H/K power amp (100wpc)
Yamaha M-70 power amp (200wpc)

I will be amping the fronts via the H/K amp.
I would like to also amp the center and my passive Tempest.

1) Can I send one channel of the Yammie to the ctr. channel and the othter to the passive sub without "crosstalk" b/w channels?

2) Will the different loads on the amp (4 ohm on one channel and 8 ohm on the other) be hard on the amp?

The specs on the amp verify 4 ohm stablility and Channel seperation is rated @ 100 dB.

THANKS

Wayne A. Pflughaupt · 10-24-2003, 09:46 AM

It won’t hurt a thing to use the amp the way you’re proposing, Kyle. Amplifier channels are completely independent and it’s no problem to use each for a different application. In addition, with 100dB channel separation, crosstalk is a non-issue.

By the way, you aren’t supposed to include equipment lists in your signature. Check #6 at
this link from the Rules/FAQ. What you might do is have the Forum create a web page for you at the Theaters site, and you can include your list there, and even pictures if you like. Then you can include the link in your signature.

Regards,
Wayne A. Pflughaupt

KyleGS · 10-24-2003, 11:09 AM

So the differing load's also will not pose a problem?
Wayne- thanks for the info on the sig.

JohnSer · 10-24-2003, 11:50 AM

Kyle, I would do it a little different. The 510 should easily handle the center and surrounds. Run the HK amp for the mains, like you have. The Tempest, I believe, has two 8 ohm voice coils. Run one voice coil to each channel on the yammie. This will give you a full power to the sub, without robbing from the center, during long LFE passages.
JMHO.

JohnS

KyleGS · 10-24-2003, 12:53 PM

I thought about that but I have read a lot of places that the center get ~60% of movie info. I'd like to know that my center was getting a full 200w of very clean dedicated power from my Yammie. Besides, my Tempest doesn't need more than a few hundred watts in my small living room.

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JohnSer · 10-24-2003, 01:39 PM

Kyle, the center may indeed get 60% on average, of the movie info, compared to the other channels, but that doesn't relate to power requirements. The low frequencies take much more power to produce, than higher frequencies.

I am assuming your yammie amp shares a common power supply, and is not a dual-mono design (two seperate PS). When large demands for the sub are required, it will lower the rail voltage on the PS, and impact what is being produced on the center channel. It may cause clipping on your center channel.

It shouldn't be a big deal to test both types of configurations. Play some demanding scences from your favorite DVDs, and let your ears decide.

If you really need any extra power to the center (doubtful given a small room), than the 510 provides, if it is bi-ampable, try that. It is easy to do with the preouts/preins on the 510.

JohnS

Wayne A. Pflughaupt · 10-24-2003, 04:47 PM

I’m not seeing the logic here, John.

First, “burning” two channels of an amp for a DVC sub driver doesn’t necessarily result in better performance from the sub. Sub performance is about moving air, and driving the second voice coil with a dedicated amp channel isn’t going to move anymore air if the driver’s already operating at its excursion limits. Any benefits that may be realized by driving both voice coils independently can be just as easily achieved by using one amp channel to drive the voice coils in parallel.

Second, those old Yamaha amps are built like tanks, and they can operate safely at 4-ohms. Which means it’s safe to assume that it can fully deliver its rated 8-ohm power with both channels driven.

Also consider the HK 510 only has 70 watts per channel. Even if the Yamaha does have some power sag in one channel, how much could it be? A five percent drop in power? Ten percent? Even if it’s as much as 20%, the Yamaha will still be putting out more than double the power to Kyle’s center channel than the 510.

Regards,
Wayne A. Pflughaupt

JohnSer · 10-24-2003, 08:36 PM

Wayne, as I said, I am not familiar with this yammie. Maybe it is an excellent power amp. But many don't double down, ie does it produce 400w into the 4 ohm load of the Tempest? With many of todays DVDs, that stress the LFE, it can eat up allot of power, driving the tempest. If this amp is a dual mono, and can provide 400w a channel into 4 ohms, what does all that extra headroom buy you on the center channel? I don't believe Kyle is running on the hairy edge with 510, in a small room, so its unlikely to produce a noticable sonic difference. If the HK had a very wimpy amp, maybe, but it doesn't.

Also, think about this, how many multiple channel amps do you see advertised, suggesting or recommending to run your sub off one of the channels? If this was such a good idea, wouldn't they have included it in one nice package? Instead of 5 and 7 channel amps, we should see 6 and 8 channel, to run subs, correct?

There is no magic with running the voice coils seperated, one on each channel. The sub should perform about the same. The only benefit is a cooler running amp, that will last longer.

Kyle should see a drastic improvement just converting the sub to active from passive. Also having control over the volume of the sub, and able to set it seperatly from the mains. All in all, I say try both and let the ears choose. Nobodys opinion can overide what you actually hear and like.

JohnS