Speaker wattages..

[imamartian]

Hi. Please humour me with this noddy question....

But can someone shed some light on the question of HI-Fi's and speaker wattages please?
If i buy a Hi-Fi rated 50W, then do i need to attach speakers rated the same? What if i add speakers a lot lower/higher rated?

And what about speaker input/output values? what do they mean?

Maybe you can refer me to a website to learn all this?

 

[JohnD]

higher rated speakers should be used so you won't damage the voice coil if you turn the amp way up

but check that you are looking at the RMS per channel output of your amp (cheap ones sonetimes quote "peak music power output" (PMPO) which is about double and add together all the channels. So they might say two channels at 25watts each is a 50 watt amp)

It is simpler to use 8ohm speakers and look at the 8ohm rating of the amp (you are unlikely to ever use anything else)

On the other hand good-qaulity speakers may be more able to cope with occasional peaks than cheap ones. I have forgotten the relevance of damping factors.

depending on who lives in the house you might never turn the amp all the way up. Mine are 100 watts per channel (5 channels) which is ridiculous and I never use it. I doubt I would ever really need as much as 25w.

 

[Stivino]

My experience contradicts JohnD's advice. I clearly remember buying hifi separates and the advice I was given was that more speakers are ruined due to the amp being under powered. The reason given was that because the amp has to be turned up to drive the speakers the subsequent distortion in sound does the damage.
I know someone in the hifi game so I could ask him when I see him.

 

[ChrisFrost]

Hi. Please humour me with this noddy question....

But can someone shed some light on the question of HI-Fi's and speaker wattages please?
If i buy a Hi-Fi rated 50W, then do i need to attach speakers rated the same? What if i add speakers a lot lower/higher rated?

And what about speaker input/output values? what do they mean?

Maybe you can refer me to a website to learn all this?

Both the above are correct, but under different circumstances...

Long term you're more likely to do damage by running an under powered amp at high volume because of distortion. The speakers pay the price.

Short term, a seriously overpowered amp running at max volume with under-rated speakers is likely to blow the tweeters. The poor old speakers get a stuffing again.

There's tons of info on this topic. Have a look at these as a start...

http://everything2.com/title/Speaker+efficiency

http://www.bcae1.com/speakrat.htm

...but don't let this keep you up at night. If you are buying from a proper Hi-Fi dealer i.e. a shop where you sit down, coffee in hand, and listen to music that sounds like the singer is in the room, then leave concerns about power matching to your host. On the other hand if you choose your Hi-Fi while standing next to a washing machine as a spotty 'yoof' plays you a selection from Ibiza Athems 2008, or perhaps worse still you 'click to buy' then quite frankly you've got bigger problems than matching power ratings

 

[imamartian]

Thanks people, i appreciate the advice.

My problem (or circumstance) is that i want to replace my hi-fi with one that plays cd's and has an ipod dock. But i'm not interested in the speakers that come with it, as i feed into a switch box which connects to 5 sets of speaks already strewn about my house.

The speakers i have already vary massively from big chunky ceiling mounted things (Genexxa - not sure how good they are) to ceiling mounted things from screwfix to small cheapo things in my conservatory.

 

[ChrisFrost]

The speakers i have already vary massively from big chunky ceiling mounted things (Genexxa - not sure how good they are) to ceiling mounted things from screwfix to small cheapo things in my conservatory.

Oh FFS The best speakers you have are Genexxa...Tandy's price-buster own brand; and then it does down(!) from there!! oh Jesus Christ.

There's us giving you sage advice about distortion levels, and you're gonna stuff horribly compressed and distorted MP3 and AAC through the system. Ha ha ha.

I'm betting the spec sheet for the "Hi-Fi" says it produces hundreds of Watts power too which is why you're concerned. Relax; they lie. They measure power at fraction of a second delivery in to a low Ohm load to get a big number. It's not real Watts. There's very little current delivery with toy systems and almost no power reserve so you're not going to blow your speakers with excess power. God knows what the distortion figures will be like - probably through the roof - but perhaps no worse than the old amp.

 

[imamartian]

seriously, those genexxas are really quite good, i have four in a kitchen/diner scenario, and cranking them up sounds really good....
not sure i should mention the make of my current stereo.? but it's a Pioneer!

Any thoughts on make/model of stereo i should go for? or replacement speakers? (talking £200-£300 in total budget!).

 

[ChrisFrost]

Pioneer made some good stuff. The A400 amp from the 80's is a very well respected classic. A reasonable rule of thumb is weight. If the amp is a heavy sucker then it's got a decent sized transformer which often means decent build quality. Conversely, if the amp is as light as a feather...

So, you want to connect your iPod and also to be able to play CDs through the system. Your budget is £200-£300. You've looked at some sort of all-in-one system with an integrated iPod dock. If it was me, then my priorities would be...

#1) Decent budget amp with good power output - Richer Sounds - Cambridge Azur 540A V2 graded (60W/ch) or 640A V2 grade (75W/ch) - both on clearance stock @ £150

#2) CD player - don't bother. Cheap ones within your budget will sound crap so are a waste of money. Something decent will blow your budget apart. Instead, rip your CDs to MP3 or AAC at 192kbps or better. Use the iPod as a jukebox.

#3) Buy a half decent iPod dock with remote control or that can be controlled. Again there's something in the Cambridge Audio range for £40 that would do. You can spend more and get extra features of that's important to you. Charging is useful. Video output is good too for track selection and control if there's a TV nearby.

If you must have a CD player then go for something secondhand and get some quality. NAD, Denon, Arcam, Creek - all decent gear with plenty of peer reviews to help you sort the wheat from the chaff. Forget about playing MP3 from a CD player; your iPod can do that just as good.

Why not an integrated iPod dock?
First, I don't trust Apple not to change the format of iPods so making a built-in dock redundant overnight. Second, I think there's a lot of poor gear being sold on the back of the "me too" appeal of having a dock. If you have money to burn then that's fine, but if not then there are better choices.

Why not a micro CD receiver?
Power - or more specifically a lack of it - Although there are small systems from Denon (DM37DAB), Onkyo (CR525DAB) and NAD (C715) that fit your budget they're all compromised by their size. There's no room for a decent sized power supply so these things kick out 12-30W. That's enough when driving a pair of high-efficiency speakers but that isn't what you've got.

Speaker upgrades?
Unless you can throw a chunk of cash at this to get something that's good and has high efficiency then IMO its waste of money. Have a look at the sub £100 bookshelf speakers on Richer Sounds and SuperFi's web sites. Look at the efficiency ratings - 85dB, 86dB. Then look at stuff at £120+, you start to get 88dB and 89dB. That 3dB extra means the speakers will sound twice as loud for the same volume from the amp. They're much better at turning Watts in to noise. That's important if you are driving several sets of speakers together.

Hope this helps

 

[freddiemercurystwin]

seriously, those genexxas are really quite good, i have four in a kitchen/diner scenario, and cranking them up sounds really good....

 

[timtheenchanter]

hmmm, seems to be a bit of brand bashing here!!!

before we bash too much, before gennexa there was realistic, who used to do some very nice PZM mics, which were basically the rejects from crown, now these didnt make crowns stock mainly due to frequency response, so they wouldnt well them for the £250 price tag, in tandy they fetched about £60.

in my early days of sound I also had some realistic speakers, 5inch bottom in a cast aluminium case, these had a very nice sound to them, they are in the back of a cupboard somwhere now as I have continued to upgrade over the years.
HOWEVER, gennexa also did some stupidly large hi-fi speakers, that were only rated to about 70W RMS, and these were, rather rubbish (being polite) so without knowing what speakers they are, I wouldnt like to comment on the quality of sound.

I do like cambridge audio amps for home systems, they are good value for money, I have 3 of them...

 

[timtheenchanter]

forgot to add, with all those speakers, you need to be careful not under run your amp, there are not may hifi amps that go below 4Ohm, some go down to 2, but not many if you under-run it, you will be effectivly causing a short accross the speaker terminals, which is bye-bye new amp.

a rule of thumb for PA systems is to have an amp twice as powerful as the speakers, and never to run at full whack, the otherway around and turning up will cause clipping (a square wave audio signal) which will do you speakers no good at all.

 

[plugwash]

forgot to add, with all those speakers, you need to be careful not under run your amp, there are not may hifi amps that go below 4Ohm, some go down to 2, but not many if you under-run it, you will be effectivly causing a short accross the speaker terminals, which is bye-bye new amp.

As long as you aren't running at anywhere near full power it shouldn't be too much of a problem. Even if you do I would hope that any modern amplifier would have some form of protection.

Still if you have a lot of speakers and don't want to spring for expensive 100V line kit it's often a good idea to use series/paralell combinations to keep the impedance in the amplifiers preffered range.