[sleepkyng]

Can someone explain the sensitivity ie 89dB of speakers? what does that mean exactly? is it better to have speakers with 89dB than 86dB?

second question:

what are the pros of bi amping and bi wiring a pair of speakers?


thanks in advanced!

[byteme]

I beleive that a speaker that is 89db efficient will produce 89db of sound from 1 watt of input at 1 meter from the speaker.  So, vs. an 83db efficient speaker it is 6db louder given the same input.  Increase in db requires a logrithmic (that doesn't seem like the right word there....Hmmm) increase in wattage.  So in order for the 83db to play as loud as the 89db speaker you need like 60 times more wattage.  So, the 89db efficient speaker isn't necessarilly "better" but the more efficient the lower powered amp you can use.  A SET tube amp guy isn't going to get much volume out of a 83db speaker.

Bi-amping is using a single amp for each crossover frequency "section".  So in a two way you have one amp power the mid/bass driver and another power the tweeter.  This lowers the load on the amp and allows use of different cable for each driver, theoretically so you can use cable better suited to each.

Bi-wiring will start a shitstorm depending where asked.  Some people claim it was invented by cable companies to sell more cable, others claim huge sonic increases.  All this is really doing is running a separate cable for each driver from a single amp.

[PhilNYC]

Sensitivity is a measure of the sound pressure level generated at a distance of one meter from a speaker when the speaker is fed a 2.83 volt signal (1 watt at 8 ohms).  So an 89db speaker will produce a sound pressure level of 89db when fed a signal of 2.83 volts.

In general, a speaker with a higher sensitivity rating will play louder given the same signal than one with a lower rating.  There are a lot of other factors that go into a speaker to say whether higher or lower is better.  A higher sensitivity speaker can be driven more easily by a lower powered amp.  However, you might also find that higher sensitivity speakers don't have as much control (obviously, this is very dependent on the specific implementation)...each has its own design goals and tradeoffs.

Hope this helps...

[JohnR]

89dB means that, with one watt of power in an anechoic chamber and with a microphone placed one meter in front of the speaker, that the sound pressure level will be 89 dB.

An 89dB speaker only uses half as much power to produce a given volume as an 86dB speaker. To put that another way, a 50W amp on the 89dB speaker will produce as much volume as a 100W amp on the 86dB speaker.

*However* there is no such thing as a free lunch, and *in the same size box* the 86dB speaker will most likely have deeper bass extension than the 89dB speaker. As a general rule, small size+deep(-ish) bass=low sensitivity.

I will leave the second question alone, see us in the lab if you are really interested

[Edit: shoot, two posts snuck in front of me ]

[DVV]

...

*However* there is no such thing as a free lunch, and *in the same size box* the 86dB speaker will most likely have deeper ba ...

John, I beg to disagree. While this can be the case, in real life, it hardly ever is. Less dB per watt can also mean flimsier magnets, and unfortunately, in today's world of price cutting, this is in fact mostly so. Less powerful magnets mean many things, and all of them are bad, except for the price, which is also lower, but this taken to be good.

A heavier membrane should also imply greater stiffness - but again, while quite possible, this is not necessarily so. Hark back to the heyday of bextrene cones. In their day, they were touted to be ideal (as is said of any new gimmick somebody dreams up for lack of a true idea). Then people discovered they were considerably less efficient, and what did the manufacturers say? Of course they are, efficiency and bass extension are contradictory (a half truth turned into holy gospel). Who said that? Only those making and selling bextrene cones, and these were in 90% of all case British manufacturers.

In opposition on their own home turf, they had Jordan-Watts developing VERY light all aluminium cones. So where's bextrene today? In the garbage, where its place always was, and more and more people are using aluminium cones.

Lastly, please remember that efficiency is also very much related to the design and execution of the crossover. Some were extremely complex in order to be relatively linear in their phase response, the price being that extra power was needed for their 25+ component crossovers in a 2 way speaker. Capacitors, inductors and resistors tend to gobble up power.

About the same discussion was conducted on silk/cloth vs. titanium tweeter domes. Most silk/cloth domes can be show to produce inordinate amounts of distortion, while similar titanium domes do not. Take the best of cloth/silk domes and compare them with the best of titanium domes and you will still have titanium producing less distortion. Then take a look at WHO is saying titanium shrieks, is bad, and is the devil's work - chances are it will be manufacturers of cloth/silk domes, who are losing business.

The point is, it's very hard to generalize in a world where price and market position is everything. I have indeed heard some speakers using titanium domes which really did shriek and rip your ears open, but I have heard many more cloth/silk domes speakers which did the same, or sounded wooly, mixed up, and heavily veiled.

Cheers,
DVV

[azryan]

Rewording what JohnR said,

It takes about double the power to get 3db louder so the diff. in a speaker's effi. can make a HUGE diff. on how much amp you need.

~10 times the power to go 10db louder (general rules).

byteme posted "-So in order for the 83db to play as loud as the 89db speaker you need like 60 times more wattage.-"

More like 4 times than 60.
4 times is a LOT though.

If a smallish amp is 100W it'd take ~400W monsters for the lower effi. speaker to match the higher effi. one using 100W, and then there's the matter of IF the lower effi. speaker can actually handle that much power!

Most of us use maybe a single Watt or two while listening to most stuff, but it can quickly take tens to hundreds of Watts to hit loud peaks.

Hence people living fine with baby 8W tube amps and others demanding 500W solid state or digital monoblocks to try to hit truly realistic volume levels and dynamics.

There's a few important points not yet said about speaker effi...

1). The single XXdb rating is just an avg. over the entire range the speaker is rated.

A speaker might be 86db @ 1000Hz, 90db @ 2000Hz, 87db @ 3000Hz, etc...
The overall numbers are averaged out to get say ~89db rating.

If speaker's got a great freq. response then the simple rating of say '89db' could tell you something.

If a speaker's response has huge dips and peaks if can still avg. 89db but that no longer means much.

2). Most of the time you're getting the rating from the company 'telling you what it is'.

They can call an 85db speaker a 90db speaker. You don't see something that wild often though 'cuz they'd get caught too easy, but they could easily (and often do) add a db or two to their avg. rating.

S'Phile reviews give you the effi. they find vs. the companies own rating. The two usually don't match.

Some other companies are dead honest or even conservative in their rating so you could have a speaker rated 89db and another rated 86db and find the 86db model to be louder because of one rated too high and one rated too low.

Also the lower rated speaker could have a brighter top end making it seem louder. All sorts of little things mucking it all up and making it more complicated than '89 beats 86'.

It's always good IMO if a company shows full measurments so you get a much better picture of what's goin' one there.


3). Saying '89db' is actually sensetivity not efficiency.

If an 8 Ohm speaker is 89 db and a 4Ohm speaker is 89db the 8 Ohm speaker is more effi. than the 4 Ohm one.

People (like me) usually just say 'effi.' anyway.


DVV,

Perhaps you might start a new thread on why all speakers should only use metal drivers?

[WEEZ]

azryan,

well said

WEEZ

[JohnR]

John, I beg to disagree. While this can be the case, in real life, it hardly ever is. Less dB per watt can also mean flimsier magnets, and unfortunately, in today's world of price cutting, this is in fact mostly so. Less powerful magnets mean many things, and all of them are bad, except for the price, which is also lower, but this taken to be good.

Sorry DVV but I don't think you're quite on the mark here... Try putting any driver into a modeling program and mucking about the T/S parameters. You'll see what I mean.

[DVV]

...
DVV,

Perhaps you might start a new thread on why all speakers should only use metal drivers?

Come now, that's not what I was saying, I simply used that as an example for comparison.

I do not think all drivers should be made of metal, although I must add that some of those technologies and products are most seductive in their performance (e.g. some Son Audax' titanium domes). The key word is "some", not "all", and certainly not "by default".

Cheers,
DVV

[DVV]

John, I beg to disagree. While this can be the case, in real life, it hardly ever is. Less dB per watt can also mean flimsier magnets, and unfortunately, in today's world of price cutting, this is in fact mostly so. Less powerful magnets mean many things, and all of them are bad, except for the price, which is also lower, but this taken to be good.

Sorry DVV but I don't think you're quite on the mark here... Try putting any driver into a modeling program and mucking about the T/S parameters. You'll see what I mean.

I did, and still think what I said.

You can play with the reflex tuning of any bass driver to an extent; on my own speakers, for example, the port could be tuned to 32...40 Hz with some influence on its efficiency - but it's rather small. Greater impact is made on the response speed, and this was verified in real life practical tests.

Cheers,
DVV

[JohnR]

And what happens if you change the T/S parameters of the driver? Lower the fs, for instance...

[gonefishin]

Like othres have mentioned.  Simply having a high or a low sensitivity rating on a speaker (or driver) doesn't automatically tell you the quality of the speaker (or driver) itself.  Bad sound is bad sound, no matter if you use a high or low efficiency design to get there.



   

Try putting any driver into a modeling program and mucking about the T/S parameters. You'll see what I mean.

   This isn't really fair because your pretty much creating a less than ideal condition to get a less than ideal response.  It shouldn't be hard to predict what type of sound you'll get when you try to build a speaker system that wasn't designed for the drivers your using.

    Unless I'm not understanding you correctly...what your saying is certainly true...but what you describe is a less than ideal circumstance for making any type of comparison.

   

     

*However* there is no such thing as a free lunch, and *in the same size box* the 86dB speaker will most likely have deeper bass extension than the 89dB speaker. As a general rule, small size+deep(-ish) bass=low sensitivity.

   Again, I would have to agree with what you say here.  But I think it's a bit misleading...and it doesn't even compare the bass quality of a low efficiency bass system and a high efficiency bass system.  It just tells us that a high efficiency driver cannot compare in quality to a lower efficiency system when both are put in a small box.  

    You did put qualifiers (*) in your statement to make it read true...but this certainly doesn't tell the whole story, does it?  
 
     Putting a higher efficiency woofer with a large magnet in a tiny enclosure and expecting to get any type of quality bass doesn't tell us much at all...except maybe not to put a woofer in an enclosure it wasn't designed for.


    But, if your looking for low bass in a tiny enclosure...your better off looking into Low(er)-E designs.  I'd agree with that

 



    take care>>>>>

[DVV]

And what happens if you change the T/S parameters of the driver? Lower the fs, for instance...

Change any parameter from the Thiele-Small set and you change the whole. The entire idea is to marry it all into one big, happy family. By the same token, discussing what happens when you change one parameter of a string of several is rather pointless, I think.

Ultimately, all these particulars will also depend on external factors not shown anywhere in driver specs, such as: 1) what kind of enclosure are you using (reflex, transmission line, etc), 2) how big is the enclosure, i.e. what is its effective volume, 3) how well braced is it, i.e. how stiff will it be, what materials are used, what damping, etc, 4) how will you make the compromise between fast response, maximum linearity and effectively reporudced low end, and so forth.

And just when you think you have it all, "Something wicked this way comes" (by Ray Bradbury), called the crossover. It can do anything from marrying it all harmoniously to blowing the whole thing out of focus, gobbling up power, introducing phase shifts, etc.

As a man listening to a speaker, will you even bother to ask yourself where the actual problem lies if there is one? I don't think so, that's reserved for the likes of you and me, 99% of people won't bother, and indeed, why should they?

But this is getting out of hand. John, you believe there is a relationship between efficiency and quality, where the higher the efficiency the lower the quality (in broad terms, of course); I believe you are wrong, because I have learnt from experience that low efficiency drivers may be more linear than high efficiency drivers, but they will never reproduce the microdynamics of music as high effciency drivers will, not unless they are driven by behemoths rated at 400+ watts per channel, or some such.

I believe bextrene was a total miss as such, but it was indeed most useful insofar that it directed research and development in a good direction. First kittens are always thrown out. Materials like aluminium show much promise, but that technology is not quite ripe yet either (at least in terms of bass drivers, dome tweeters are a different matter). And lastly, this entire discussion may well be out of place in view of planar speakers, which also show great promise as a technology.

Cheers,
DVV