CurtPalme.com Home Theater Forum

MYoung · Joined: 24 Feb 2007 Posts: 369 Location: Madison, WI

I just bought an entry-level 5.1 surround sound system in a box (Sony HT-DDW700) for my beater basement home theater setup. It's 900W system -- 140W x 5 + 200W subwoofer. I got it for $190 after taxes and 10% off code from CircuitCity.com with same day pick-up (yeah, I'm just as shocked that I actually found something worth buying there!). I was thinking of replacing the dinky left and right channels with a little larger, 2 driver, bookshelf speakers. That way I can get some richer sound when playing music. Granted, I'll have to turn down the sub a bit. The tiny speakers it came with are rated at 140W, though I think my bookshelf speakers are 100W (I still have to dig 'em out and verify that). What are the negative consequences of hooking up 100W speakers when the spec speakers are 140W? Crappy sound? Risk of damaging/blowing the lower wattage speakers? Fire hazard? Dogs and cats living together... mass hysteria?!?!

MYoung · Joined: 24 Feb 2007 Posts: 369 Location: Madison, WI

Hmm, in digging around the Internet I see some people stating that it's not a huge deal to run a little lower wattage speakers on an amp than what it's rated for -- though one shouldn't "crank it" too loud, as that's where distortion comes in and potentially, damage to the speakers. Does that sound right?

**Curt Palme** · Posted: Wed Apr 23, 2008 2:45 am Post subject:

Here's the scoop:

Speaker ratings are somewhat ambiguous when it comes to wattage. THe key is: CLEAN POWER! I was running a pair of 10 watt bookshelf speakers off a 250 watt amp in high school, ran them WAY louder than I should have, but never blew them because the amp gave out clean unclipped power. It's actually easier to damage a 100 watt speaker with a 50 watt amp than a 50 watt speaker with a 100 watt amp.

MOst manufacturers in the 'old days' with rotary volume knobs hit clipping (max power) at about the 12:00 mark. Past that the amp would clip, and you'd blow your tweeters.

General rule:

Blown tweeters- amp run into the clipping point.
Woofers blown- too much power into low power speakers.

Then there's speaker efficiencies, etc.

Bottom line is, speakers will be damaged well BEFORE you can hear the distortion. If you hear distortion, you're way too loud for what the amp can put out, so turn it down.

Chances are you'll never blow your speakers though.

Tom.W · Joined: 09 Mar 2006 Posts: 6635

Better to run the amp at about half power anyways. It should run cooler with less distortion. Can you put a limit on the amp output to the speakers to prevent the wrong hands at the master volume control ?

MYoung · Joined: 24 Feb 2007 Posts: 369 Location: Madison, WI

Thanks for the info, Curt! So the bottom like is that so long as I'm not a jackass with the volume, I'll be okay. I suppose that if I do blow the speakers, no big loss. They're 3 year old $80 Sony speakers. El cheapo, but still better than the rinky-dink satellite speakers that come with the system. The system still gives good bang for the buck. Beats the poo outta the 15W Altec Lansing speaker set I got from Walmart for $26. The receiver cannot switch video, but I think I'm going to opt for a separate 4x1 switcher that will switch component video and digital optical audio.

mike calcott · Joined: 18 May 2006 Posts: 307 Location: Australia

make sure the impedence match is correct, if the amp outputs at 8ohms use 8ohms not 4ohms.

MYoung · Joined: 24 Feb 2007 Posts: 369 Location: Madison, WI

The receiver is pretty low end and doesn't appear to have any controls for limiting power output. I don't even think I can specify cross-over frequencies, which is kind of a bummer now that I'm using left and right channel speakers with more base. Though turning down the sub seems to work fine. I know I'm matching the impedence, but thanks for the reminder. $190 and worth every penny! It will be a good beater setup. It sure beats getting a POS RCA surround sound system from Walmart.

ecrabb · Posted: Wed Apr 23, 2008 3:37 pm Post subject:

I'd also like to point out the fact that the system that is sold as outputting 900w (140x5) is probably not even outputting 1/4 of that in reality - never mind whether it's clean power. I'd guess that receiver is good for maybe 50w with all channels driven. And the sub - 200w? Yeah, right.

High-end $1500 receivers with discrete power supplies can often barely output their full rated power (if they do), let alone a cheap HTIB system. The way they rate those systems is practically criminal. One manufacturer uses one channel driven, another uses two channels, one uses a 4khz test tone, another 2khz. I wish the FTC and a trade group made up of responsible manufacturers would force a REAL standard rating system to be used to sell any sort of amplifier.

Note, I'm not saying the little Sony systems isn't just fine for what it is. Compared to one of the tiny little RCA box systems, it's probably great. The tiny systems probably can't muster 25w on a good day.

Mike - Take a look at the labels on the back of the receiver and the sub. It should list power consumption on it somewhere - in watts - Just for fun, tell us what those ratings are.

SC

**kal** · Posted: Wed Apr 23, 2008 4:07 pm Post subject:

ecrabb · Posted: Wed Apr 23, 2008 4:25 pm Post subject:

Kal,

I've never seen those Emotiva's before - those are damn good prices for that much power. If they had an XPA-6, I could sell my Crowns and pick one of those up. I was always an ATI fan, but they're way out of my price range. These look about as well-built as the ATI's. The LPA-1 is a really great price, but I think it actually has less power than my Crowns. Looks like a hell of an amp - have you heard them?

BTW, you linked to the XPA-5 instead of the LPA-1.

SC

**kal** · Posted: Wed Apr 23, 2008 4:43 pm Post subject:

Emotiva's got a pretty strong following. IIRC they spun off of AV123.com. The only problem is that their prices scare me a bit. They have (supposedly) fully featured pre-pro's for about $1000 with some high end HDMI units coming out this year to compete in the $3-8K league... but at around $1000-$1400!

There are some threads over at AVS where they compare a bunch of $4-12K pre-pros and a $799 Emotiva unit and it reviews extremely well.

I'm keeping my eyes on them.

Kal

MYoung · Joined: 24 Feb 2007 Posts: 369 Location: Madison, WI

Believe me, I'm in no way making a case that this system I got is anything fancy. It's quite low-end. I just wanted to make sure I wouldn't have problems hooking up 100W speakers when the receiver states 140W per channel.

I was considering getting a better receiver for my main setup -- one that would switch HDMI so I could then convert my video chain to digital and get a HDfury, but I decided to just live with component video and 5.1 analog audio from my HD-A1 for now as I still have yet to see many titles on Blu-ray I'm interested in. I have no complaints about the HD-A1's component video output quality. Perhaps I might even end up staying with component video and getting a stand-alone Blu-ray player with better component video output than the PS3, assuming they have better component video output. I'm finding I'm using the PS3 much more as a gaming system than a Blu-ray movie player. The PS3 has been living in the basement attached to the D50, sparing the 1292Q static burn-in from hours upon hours of Call of Duty 4! Speaking of that, it will be nice to play that game with surround sound. It's frustrating hearing sounds and having no idea where they're coming from in the game! Of course, it remains to be seen how good the surround sound is implemented in the game.

perisoft · Joined: 29 Aug 2007 Posts: 2920 Location: Ithaca, NY

The per-channel thing is why I've got separate amps for each set of channels and to each sub... I've got relatively lousy home audio receivers (rated at maybe 100w/channel) but am driving the fronts with one, the center with one, the rears with one... so I don't have to pull near maximum power and I can get reasonably clean sound out of a bunch of salvation army amps that were basically free. The only one I paid anything significant for is the one driving the fronts, which isn't too bad.

To do that, though, you have to have per-channel analog output and have some kind of control of what goes where, which usually means HTPC. I'm not sure many stand alone players have anything but digital output.

**kal** · Posted: Wed Apr 23, 2008 9:19 pm Post subject:

**kal** · Posted: Wed Apr 23, 2008 9:21 pm Post subject:

greg_mitch · Joined: 03 May 2006 Posts: 5320

**Curt Palme** · Posted: Thu Apr 24, 2008 12:04 am Post subject:

Give me brute force class AB amps over anything. A good amp weighs 60 lbs minimum.. Smile

None of this nancy boy digital switching 1 giga watt per channel, and it only weighs 11 lbs BS for me!

mike calcott · Joined: 18 May 2006 Posts: 307 Location: Australia

When I was selling power/pre combo's 30 years ago, amps like original US Marantz, Phase Linear and the like had huge power supplies which was the major contribution to their weight. The constant reserve of power contributed to the constant output wattage over the full dynamic range. Most modern amps/receivers rated at 100-150 watts over 5 channels lack the low end grunt that the older amps used to give, it seems the output of modern amps are rated around the midrange, but lack the low end performace due to the lightweight power supplies and small output caps which do not supply sufficient output voltage required for good low end performance

**Curt Palme** · Posted: Thu Apr 24, 2008 12:53 am Post subject:

Exactly! I explained it to rookies coming into my old repair shop this way (a bit technically flawed, but it made understanding the concept easy):

A large heavy amp has big filter caps that store electricity for when the big bass notes come along. They dump their power into the speakers, then store themselves up again over time.

A small switching amp doesn't have these large capacitors in them, so they don't have as large of a reserve within the amp, and rely on the AC power line to instantaneously supply the power needed for the big bass notes. If the power isn't available because you're running the coffee maker right next to the amp at the same time, the amp clips, blows up, blows the speakers, or distorts.

I got a lot of customers to repair their old amps that way instead of buying new.. Smile

**AnalogRocks** · Posted: Thu Apr 24, 2008 2:15 am Post subject: