how much power do i actually need?

[12.1]

hi there, I am pretty new to all of this and so need some help. I am thinking of getting a pair of B&W 683 stereo speakers (though this may be somewhat in the future due to money flow) and am now looking around at either amps/preamps or an integrated system. However there do not seem to be that many powerful amps out there. The B&W recomendend amp power for the 683s is 25-200W into 8 ohms - but I also heard it recomended that you need twice the speaker rated power - anyway I was thinking of something that can deliver 100W/channel into 8ohms? would this be sufficient - say a rotel rb 1070 - a rb 1072 also would fit this but i can't find any prices for it. also if you can suggest anything a bit cheeper that would be good as well.

 

[JerryLove]

(guessing) Max Transient Db * Speaker Efficiency +10% ?

I'll let someone with more familiarity put a number on it, but the issues are having enough power to drive the sound you want (an issue on the low end of the frequency range) and not overdriving your amp (clipping). Unless your amp has a protection circuit on it, this will damage your tweeter.

The rule of thumb does seem to be to try to get more amp than your speaker is rated for to avoid clipping (and there are 225WPC amps out there), but one can get away with less if you don't drive the amp too hard.

If you do end up pre-pro, I suggest more than 100WPC for those speakers. Used 160WPC or so are all over, and 200+ isn't that rare.

In a receiver, they tend to rarely push past about 145wpc... given there's a limited budget, that's what you've got to work with.

Again, there are those with far more specific and detailed advice than I. I'm sure they will be posting shortly, and I defer to their suggestions.

 

[cfrizz]

Hi. All speakers perform better with the more power that you give them, so buy as much as you can afford to ensure that your speakers will operate to their full potential.

I always recommend 200wpc @ 8ohms. This will pretty much drive any speakers you have now & in the future with ease.

Rotel makes great gear. So does Parasound, Sunfire, Adcom, Nad, B & K. To get the most bang for your buck, shop for these on www.audiogon.com.

To very good companies to buy new from are www.outlawaudio.com & www.emotiva.com.

Look at Emotiva XPA series. And for Outlaw look into their 200wpc monoblocks. Naturally you would need to buy 2 of them one for each speaker.

This isn't a cheap hobby, but if you are willing to spend more money now & get good gear the first time around, it will keep you happy for years to come without the need to upgrade.

 

[lsiberian]

Once you understand the relationship between power and volume your opinions change drastically.

Most B&W speakers are incredibly efficient 90db/w or more. That means you get really into hearing damage levels at a 1 watt. 100 watts can reach up to 110db which is the limit of most consumer level speakers I've encountered.

Therefore based on that scientific fact I conclude that an amp capable of delivering within 100 watts per channel is sufficient for you.

IOTW get a good receiver and you're set.

Make sure you listen to the speakers. I've heard a few B&Ws and the differences aren't small between them. Go listen to some.

 

[j_garcia]

How much power you really need depends on how big your room is, how far you sit from them, and how loud you generally listen. IMO, those Rotels should do fine even in a fairly large room with those speakers.

Twice the rated speaker power is ridiculous. The person who told you that doesn't know what they are talking about.

 

[12.1]

thanks for the advice guys
- jerrylove I can't find those specifications for the 683s on the B&W website though it would be interesting to find the result.
Cfrizz I am kind on your thinking - no point in spending less money now only to have to upgrade in the near future - looking at the nad c372. Isiberian you make an interesting point that i hadn't thought of:
Am i right in assuming that the sensitivy spec of 90DB spl mean that 1watt give 90db of sound at 1 meter or is that dependant on the something else? Also would I not need the extra power as a backup for the peaks in the signal - I mean i guess the speaker might not be reaching higher than 90DB on average but everyone now and then it might, in which case would having only 100watts cause clipping?

 

[lsiberian]

thanks for the advice guys
- jerrylove I can't find those specifications for the 683s on the B&W website though it would be interesting to find the result.
Cfrizz I am kind on your thinking - no point in spending less money now only to have to upgrade in the near future - looking at the nad c372. Isiberian you make an interesting point that i hadn't thought of:
Am i right in assuming that the sensitivy spec of 90DB spl mean that 1watt give 90db of sound at 1 meter or is that dependant on the something else? Also would I not need the extra power as a backup for the peaks in the signal - I mean i guess the speaker might not be reaching higher than 90DB on average but everyone now and then it might, in which case would having only 100watts cause clipping?

You need to double power in order to get a real benefit. I don't think that benefit is worth the cost.

Have you listened to the 683?

I found it to be very boomy with lot's of distortion in my demo session. The 705's where the best speaker I heard and the 684's were acceptable. I found the 705 was the only speaker worthy of it's price tag in my B&W listening session.

I recommend you check out Ascend Acoustics they have really good build quality usually.

90db is over the entire range of the speaker. It will be 87 at the -3db mark, but the difference is considered insignificant. and your bottom mark is 38 hz which is very low for that speaker. It is going to be much closer to a 4ohm load than the stated 8 ohm load.

So you only need 200 watts at 4 ohms to hit your speakers potential. This means a 100 watt per channel amp with 4 ohm stability will drive your speakers to their fullest potential.

This is my recommended receiver for those speakers

http://www.accessories4less.com/make-a-store/item/ONKTXSR806B/Onkyo/TX-SR806-THX-Ultra2-130w-x-7ch-HDMI-806-Receiver-BLACK-FREE-SHIP-/1.html

It has the top version of room correction available in receivers today. It has plenty of power and is capable of handling even a 3ohm load. It will give your speakers all the power they can take.

It's greatest weakness is it's upscaler. If you need a better one then step up to the 876.

For 550 that's a really good receiver that will meet your needs and give you all the features you could probably want.

 

[JerryLove]

Pretty much, everything said has been right (except for the guy saying "more power always better". That will fry your speakers).

Yes. 90db efficiency means that the speaker puts out 90db at 1 meter at 1 watt. 100db at 10 watts. 110db at 100 watts.

What is that like at 10 meters? That depends on the size/shape of your room, and the size/shape of your source (a headphone speaker looses dB faster with distance than a large speaker will.. something about inverse-square in relationship to emitter).

The long-and-short: bigger room = larger speaker or more power or both to fill it.

I don't know the details of transient spikes. I really don't. I hear that a unit that can't deliver peak power will clip and cause tweeter damage. I believe this but without real numbers.

That said: I have a set of Paradigm Studio 40s that I run off a Marantz 110WPC unit at pretyt high volumes in a (about) 14x12 vaulted-ceiling room (and I used to run them off a Sony receiver), and a pair of Infinity RSIIIb's I run off an old 2-channel Pioneer (125WPC) to fill a combination living-room/family room and (to a lesser extent) kitchen. I'd guess about 800 ft^2 with a 18' vaulted ceiling. I've not had a problem.

Unless your room is very big, or you listen very loud, I think you'll be fine.

 

[basspig]

Now that you've heard the standard wisdom on "how much power", I'll step in with my radical 2 cents...

But first I'd like to point out that power vs. decibel SPL is not linear in the real world. Speakers experience a phenonmena called power compression--as the voice coil heats up, it's resistence rises and its ability to load the amplifier decreases, thus reducing power transfer to mechanical energy. Another factor is core saturation--the magnetic motor has a finite permeability. This has a curve too, and it's not linear. So a speaker rated 90dB 1W 1M may suffer 4-5 dB power compression at the rated 100W, so in effect, 105dB is the real maximum output level.

Power compression has been a long term challenge for industrial professional sound reinforcement applications, and designers have come up with methods of reducing the phenomena, ranging from humungous voice coils, to servo pistons, to horn-loaded systems, to Neodymium magnets and specially-designed core/pole piece systems. There has been a lot of development along these lines in the past 4-5 years.

Of course, the standard issues everyone knows about, the rise in distortion as power input increases, is also a factor with these consumer loudspeakers, so I would be remiss to imply that it doesn't.

Now, here's a new take on things.. what does a true audiophile try to achieve? Realistic reproduction of sound--any sound. So what happens when you watch a movie like U-571 where depth charges are exploding from all directions? You've already set the level for natural dialog volume, but now along comes these explosions, some 25dB louder than the dialog. In reality, these sounds are concussive, well in excess of 120dB and consisting mostly of low frequencies in the 10-15Hz range. If one is seeking realistic conveyance of the experience, as the producer of this movie apparently was trying to achieve, then one needs to be able to get those low frequencies up above 120dB, for the full chest-caving experience of being on a U-boat under attack.

Now there's probably at least two philosophies here: if you're going to experience the film in its fullest, may as well share the danger.
The other school is that of spectators behind an iron fence, shielded from the full impact of the event.
So it's either, get in the cage with the lion and feel the terror and thrill, or stand on the other side of the fence and watch the lion from a safe distance.

So, how much power do YOU really need? It's up to you. Do you enjoy working with explosives? Do you like firing high caliber weapons? Do you enjoy going to battle reenactments with live cannons and still want for more? Do you enjoy watching shuttle launches? These are all events which go way past the safe threshold for hearing. But if you crave the real thing, it just eats away at you until you get it. So if you're watching that 1 in a 1000 movie that's got a really heavy soundtrack and you're feeling you wish you had more umppphhh, then you need more power. That's all the way around--more powerful speakers, more amplifier power (dependant on speaker efficiency) and possibly a dedicated ac line for the amplification equipment. Oh, and, no neighbors within a mile of your address.

Seriously, ask yourself, what kind of persona am I? Do my tastes fall into the average, or am I on the lunatic fringe? Maybe somewhere in between? What kind of program material do I listen to? String quartets? Or pipe organs? If it ranges from Bach to Bassotronics, then you need unusual speakers and copious amounts of amplifier power. Get ready to DIY, because you won't be in the world of consumer products anymore.

Train yourself to know what loudness levels are at different frequencies. 125dB at 2KHz is pretty darned painful. But at 20Hz, it's quite soothing. How much do you want to feel that explosion in the war movie? Just perceptably? Or chest caving in til it knocks the wind out of you? There's about a 30dB difference there. You figure the difference in power.

If you're on the extreme end, then you need to determine whether your home can stand the shaking without damage, and what sort of structural reinforcements will be needed to improve safety. There is nothing more stressful than having a 4x8 sheet of sheetrock fall from the ceiling during the opening to Also Sprach Zarathustra. It can really ruin your day.

How real do you want YOUR reality?

 

[12.1]

I havn't heard the 683s yet but will of course be doing so before buying!Need to also look at the ascend accoustics also. Regardless I will still be getting a stereo pair in that power range - and so that reciever isiberian is a brilliant suggestion - when buying a/v equipment it sometimes really sucks to live in the uk - such a great price for what it is, but no shipping outside the US anyway it would really allow me to expand later on so I may have a look at getting it somehow. How can you tell what impedance the speakers will really have btw? but yes if it is more like 4ohms i believe 100W/channel will do me fine - my room isnt too big, something like 15x12 without a high ceiling (though may be moving somewhere larger) so won;t need that much volume. Cheers for the DB confirmation and room tips also jerrylove.

 

[lsiberian]

I havn't heard the 683s yet but will of course be doing so before buying!Need to also look at the ascend accoustics also. Regardless I will still be getting a stereo pair in that power range - and so that reciever isiberian is a brilliant suggestion - when buying a/v equipment it sometimes really sucks to live in the uk - such a great price for what it is, but no shipping outside the US anyway it would really allow me to expand later on so I may have a look at getting it somehow. How can you tell what impedance the speakers will really have btw? but yes if it is more like 4ohms i believe 100W/channel will do me fine - my room isnt too big, something like 15x12 without a high ceiling (though may be moving somewhere larger) so won;t need that much volume. Cheers for the DB confirmation and room tips also jerrylove.

I think if you give those speakers a listen you'll buy a different pair of speakers IMO. I couldn't stand them.

If you want truly loud speakers get JTR triples.

http://www.jtrspeakers.com/triple8ht.html You can drive those with a pro-amp.

The UK complicates things I am not familiar with discount houses there so you'll need to shop around.

 

[JerryLove]

@basspig

1) His speakers don't go that low.
2) 120db at 1m would require 1000 watts of power at 90db efficiency, where his speakers are only rated for 200W. It doesn't matter if you think he should have the amp for it, his speakers cannot take it.
3) Given #1 above, and knowing that the bulk of the power is indeed in frequencies below what these speakers will produce, you should really be discussing why he wants a 1000W powered subwoofer, not why he needs more amp than his speakers could survive.

Among EEs and custom-builders (and both are here): conventional wisdom should be heeded.

You mention 125dB? That's more than 2000 watts.

@12.5
I know I've deferred a bit, but I do stand firm that a 2000 watt amp is entirely inappropriate for these speakers.

 

[12.1]

wow basspig, inspiring stuff! actually I am a drummer and definately like the full boom, however realistically (as you indirectly mentioned) I can't aim for that as the neighbours would kill me. Your DIY point is quite interesting btw, as my music tastes pretty much do range from 'Bach to Bassotronics' and I also like the idea of customising my stuff - so how come the consumer world won't be able cope with such a range - what sort of speaker designs would I be wanting?

 

[lsiberian]

@basspig

1) His speakers don't go that low.
2) 120db at 1m would require 1000 watts of power at 90db efficiency, where his speakers are only rated for 200W. It doesn't matter if you think he should have the amp for it, his speakers cannot take it.
3) Given #1 above, and knowing that the bulk of the power is indeed in frequencies below what these speakers will produce, you should really be discussing why he wants a 1000W powered subwoofer, not why he needs more amp than his speakers could survive.

Among EEs and custom-builders (and both are here): conventional wisdom should be heeded.

Just for clarification not argument.

1. The speakers have very good extension at the sacrifice in sound quality.
2. In peaks the speaker can handle more power. Just not in sustained loads.
3. These speakers have the extension of many commercial subs with a -3db of 38hz.

 

[lsiberian]

wow basspig, inspiring stuff! actually I am a drummer and definately like the full boom, however realistically (as you indirectly mentioned) I can't aim for that as the neighbours would kill me. Your DIY point is quite interesting btw, as my music tastes pretty much do range from 'Bach to Bassotronics' and I also like the idea of customising my stuff - so how come the consumer world won't be able cope with such a range - what sort of speaker designs would I be wanting?

If your interested in DIY there are limitless options and limitless potential.

I'm a DIY'er and love it.

 

[12.1]

Hmm those jtr triples do look damn loud! little bit out of my price range though...

So with the DIY option, say I wanted a stereo pair that could handle the whole 'Bach to Bassotronics' range of music types I guess I would be looking at something with multiple drivers and crossovers in order to reproduce the whole frequency range well - does this sort of this end up being really expensive or is that only if u want it to be - also is it possible to reproduce the same sort of build quality (cone suspension - mounting - tapered ports etc) without all the production methods employable by actual companies?

@jerrylove - while a massive power system would be 'awesome' I must admit that when I found out that to get an single increase (i.e +3dB) you require 10 times the power I did think it a bit wastefull when moving from 100-1000W for only that 3dB

 

[highfigh]

Once you understand the relationship between power and volume your opinions change drastically.

Most B&W speakers are incredibly efficient 90db/w or more. That means you get really into hearing damage levels at a 1 watt. 100 watts can reach up to 110db which is the limit of most consumer level speakers I've encountered.

Therefore based on that scientific fact I conclude that an amp capable of delivering within 100 watts per channel is sufficient for you.

IOTW get a good receiver and you're set.

Make sure you listen to the speakers. I've heard a few B&Ws and the differences aren't small between them. Go listen to some.

We have a festival called Summerfest (www.summerfest.com) and they monitor the SPL at the carious stages for several reasons- OSHA and avoiding one stage drowning out others being the main ones. They set a maximum of 95dB at the mixer's position and it's still damn loud, but it's also extremely wide-range sound. The sound company knows that some of the acts will be using synths and 5 string bass guitars, which go down to about 25HZ, and they supply equipment accordingly. Being outdoors, thbe front rows get blasted out but it's still loud at the back row, usually a minimum of 100' away at the average stage.

However, in a normal-sized house and a room with at least two walls opening into another area, you'll need more power than a room with four walls because you won't have the first reflections from the other two walls. If it's a standard 8' ceiling and about 12' x 18', you should have plenty of SPL with a 100W amp and speakers that produce 90dB@ 1W/1 meter.

Remember- every time you double the distance, you lose 6dB in a free field environment. In a room of that size, you'll lose less because of the reflections but you still lose SPL as the distance increases. 6dB equates to cutting the power to 1/4. 90dB from 10' is the same as driving that speaker with 4W and measuring from 20'.

 

[highfigh]

I havn't heard the 683s yet but will of course be doing so before buying!Need to also look at the ascend accoustics also. Regardless I will still be getting a stereo pair in that power range - and so that reciever isiberian is a brilliant suggestion - when buying a/v equipment it sometimes really sucks to live in the uk - such a great price for what it is, but no shipping outside the US anyway it would really allow me to expand later on so I may have a look at getting it somehow. How can you tell what impedance the speakers will really have btw? but yes if it is more like 4ohms i believe 100W/channel will do me fine - my room isnt too big, something like 15x12 without a high ceiling (though may be moving somewhere larger) so won;t need that much volume. Cheers for the DB confirmation and room tips also jerrylove.

You should be able to find a lot of good speakers in the UK and I though B&W was a British company, anyway. I know they have a dealer locator on their site.

This link shows that the minimum impedance is 3 Ohms.
http://www.bowers-wilkins.com/display.aspx?infid=2281&terid=2284

 

[jostenmeat]

hi there, I am pretty new to all of this and so need some help. I am thinking of getting a pair of B&W 683 stereo speakers (though this may be somewhat in the future due to money flow) and am now looking around at either amps/preamps or an integrated system. However there do not seem to be that many powerful amps out there. The B&W recomendend amp power for the 683s is 25-200W into 8 ohms - but I also heard it recomended that you need twice the speaker rated power - anyway I was thinking of something that can deliver 100W/channel into 8ohms? would this be sufficient - say a rotel rb 1070 - a rb 1072 also would fit this but i can't find any prices for it. also if you can suggest anything a bit cheeper that would be good as well.

Speakers are where it's at. Let's see, you've only got one pair of speakers on the radar so far, and already seem more concerned with the power behind them.

Amps are generally designed to be ruler flat across the entire hearing range. Speakers . . . hoo boy . . . the greatest variances in SQ are here, and it's not even close with any other component you will buy, save perhaps room treatments.

Think about it: it's where the electrical energy is finally converted to mechanical energy, which yours ears finally get to discern.

I aimed to listen to 50 pairs, and got half way there. I will dub you as my audioholic brethren if you promise me that you will "aim" to listen to a dozen pairs.

Otherwise, I'm not talking to you anymore!

j/k, the 68 series by BW are interesting if only due to the use of 1st order xovers, IIRC. Now, if you can't afford Triple 8s, you can't afford the BW 804s as demo/used for 3k, but that's what I typically recommend aiming for in their lineup. That's just my experiences. They can image like a mofo. They are (as I would explain it anyways) very consistent timbrally throughout the range.

At the rough budget of what I'm guessing the 683 costs, I'd aim instead for the finest bookshelves I could muster, and then when funds permit, add two subs working in stereo (or even mono, but regardless, they still need to be placed closely to respective monitors).

 

[basspig]

The power scale is as follows, not taking power compression into account:

+3dB = perceived as slightly louder, just barely, but requires TWICE the power
+10dB = perceived as twice as loud, but requires TEN TIMES the power

So to make something twice as loud, you need to go from say, 1W to 10W. At those levels, it's pretty linear, but the 10W to 100W jump will be a challenge for home hi fi speakers to achieve without severe power compression. In this case, you might only gain 5dB more loudness, not to mention a LOT of distortion.

There's no way that I would recommend a 2,000W amp with home hi fi speakers. And in the realm of realistic, 90dB 1W 1M sensitivity isn't going to get you there with any commercially-available amplifier. You need to start with building blocks having over 100dB sensitivity and group them together to achieve benefits of mutual coupling.

Anyone remember building a "sweet sixteen" loudspeaker back in the late fifties? 16 5" PM speakers mounted on a 36" square baffle, wired series/parallel. Individually, they sound like a table radio, but together, they sounded close to Bozak Concert Grands, just missing the highs above 8KHz. Some said they were reasonably flat to 20Hz. Certainly with all that mutual coupling, the benefits were certainly astonishing, compared with the single driver of the same type.

The concept for building a monster sound system expands on this, using the best industrial drivers, the largest amplifiers in production, and large arrays of these drivers. The total is greater than the sum of the parts.

Of course, this could be scaled to any need and to fit a wider range of budgets. But it is a total commitment. That means it starts with appropriate structural upgrades to the house, the room, and careful attention to protecting valuables like glassware in the kitchen/dining room areas. There are so many details, like putting a lip on every shelf to prevent glassware from walking off the edge, to putting in solid bracing every 24" in the floor joists, to putting in drywall screws ever 2-3" on the walls and ceiling... the list goes on--and I haven't even gotten to acoustic treatments yet!

Once all that's in place, then you're ready to figure out the system components. Since 90% of the power you'll need is below 75Hz, much of your effort should be invested in the low frequency reproduction hardware. An array of woofers, and at least a middle of the road pro-grade amp, such as some of the larger amps from Behringer, or, if you have to have audiophile gear, a couple of Carver's larger mag-field amps, or pick up some used Hafler 500s and bridge them for mono operation. eBay is a great place to pick up deals on a lot of this gear and to get launched without a second mortgage.

I recommend DIYing the woofer/subwoofer cabinets and using industrial woofers. There was a company selling a decent woofer to the general public called Acoupower, but I think they went out of business. There is another company that bought the domain name and it is NOT the same company, nor drivers. However, there are a growing number of competent subwoofer drivers on the market from a handful of manufacturers that will really please the hardcore low-frequency fanatic, so there are options for the DIY'er.

It's hard to find good midrange drivers today, unless you go with ribbon arrays, but they are power-limited to a great extent, so you'll need a large number of them. Another alternative is to use high grade midrange drivers and build a line array. That will give the power handling, SPL and a nice sense of acoustic space.

Amplifier power is pretty cheap. There are amps from Behringer, Carver, Crown, QSC, Powersoft, etc., in power outputs ranging from a few hundred watts to ten thousand. It's economical to buy industrial amps that are "off tour", ie, a couple of years old and being rotated out of service. You get real muscle for modest investment.

The bottom line is to listen to a range of installed systems and decide how much is enough for you. If you like standing on the runway facing the exhaust of a General Electric GE90 at takeoff, then you're equipment demands are going to be expensive. On the other hand, if you're satiated with the sound you get at a major rock concert, then it will be much easier and less expensive to achieve in a home environment.