Grex Music3 Conference

Item 96: Home Theatre System: speaker sensitivity question

Entered by eprom on Thu May 2 04:06:47 2002:

hmmmm.....I have an average home theatre setup.

2 tower fronts speakers, 2 bookcase rear surround speakers
and a center speaker.
 
I'm thinking of replacing the center channel. 

The center speakers I've been looking at are rated at a
higher sensitivity (92 dB) than my fronts and rears (89 dB).

how important is it to match speaker sensitivity with your
other speakers?

In theory the center would be twice as loud (3dB) as the
other 4 channels?????



47 responses total.

#1 of 47 by gull on Thu May 2 13:57:45 2002:

Most home theater receivers have a way to balance the speakers, so it
shouldn't matter.  Just dig out your manual and see what the procedure is. 
Even my cheapo Aiwa receiver has a way to do it...it even has a test mode
that generates white noise in each channel in turn, to help you figure out
which ones need to be louder or softer.


#2 of 47 by tpryan on Sat May 4 20:36:22 2002:

        The SW: Phantom Menance DVD also has a home theater check-out 
clip/program on it.


#3 of 47 by gull on Sun May 5 02:14:31 2002:

I think all DVD releases where THX did the sound have that.


#4 of 47 by jaklumen on Sun May 5 11:16:21 2002:

*ponder*  Works, I guess.  I think I heard about speaker sensitivity 
being related to efficiency of how the speaker handles sound, i.e., 
it's a better indicator of output that wattage alone.  Home audio can 
get really involved if you want and Radio Shack is one place to start 
for questions and answers if you want to go further.

Otherwise, yeah, it's just figuring out how to balance the speaker 
output.  Equalizers may help if you run into distortion problems.


#5 of 47 by jmsaul on Sun May 5 14:15:35 2002:

Well... if you want to get really involved with home audio, I'd personally
stay away from Radio Shack.  The staff won't necessarily have a clue, and
depending on your price range you'll be able to get better equipment
elsewhere.  (If your price range is the kind of price range Radio Shack
carries, you're better off getting used higher-quality gear; if you have
serious money to spend, you want to go to a specialty store.)


#6 of 47 by jaklumen on Mon May 6 09:12:54 2002:

Actually, I don't doubt that, although Radio Shack has improved some 
of their lineup somewhat in partnering with RCA.  My understanding is 
that some tools and a few obscure components can be gotten there.

Used higher-end?  Where would a person find that, say, for someone 
that lives out in Hicksville, Eastern WA?


#7 of 47 by scott on Mon May 6 13:21:14 2002:

Radio Shack does sometimes have rather high-end components, although probably
by accident.  Some years ago they had a small speaker (the "Minimus-7", I
think) which some audiophiles were quite fond of.  There was even a kit you
could buy to improve the tweeter or something.


#8 of 47 by gull on Mon May 6 13:29:46 2002:

I won't buy anything made by RCA, after they churned out all those defective
TVs in the 90's.


#9 of 47 by jmsaul on Mon May 6 13:34:20 2002:

I don't know your area at all, but if there's some community out there where
rich Seattleites spend their weekends, I'd start with its yellow pages.  Or
do a Google search on "NAD, "Arcam", or "Paradigm" and whatever words you
think might find you an audio store in your region.  Those brands can
sometimes be found very cheap used, and there usually isn't anything wrong
with used high-end audio gear except scratches on the case.

Hmmm... well, if Kennesick is near you, there's a place called Quicksilver
Audio (www.quicksilver-audio.com).


#10 of 47 by jmsaul on Mon May 6 13:35:12 2002:

Oops, that was meant to be "Kennewick."  ;-)


#11 of 47 by keesan on Mon May 6 20:48:13 2002:

I am happy with the stuff we find at rummage sales and the curb, that often
only needs the switches cleaned.  Receiver, tape deck, speakers at the curb.
$5 receiver at a church sale.  Big speakers are now cheap because there are
good small ones.  Put your own ad in the paper for old stereo equipment.


#12 of 47 by tpryan on Tue May 7 01:57:32 2002:

        I saw some 12 inch speakers at the Re-use center that have
lost there speaker surronds.  
        My recently repaired speakers sound great.  No more bass
farts, and good to hear good tweeters again.


#13 of 47 by jaklumen on Tue May 7 09:06:30 2002:

resp:9  How the hell did you hear of Kennewick or Quicksilver?  It's a 
fairly long-time staple of my hometown (yeah, I used to live there).

Kennesick.  Hehehehe


#14 of 47 by jmsaul on Tue May 7 10:48:36 2002:

I did a web search.  ;-)


#15 of 47 by jaklumen on Wed May 8 04:02:10 2002:

Well, I also know there are other places, but yes, that's a biggie.


#16 of 47 by jmsaul on Wed May 8 14:28:05 2002:

Try there, then.  The key with this stuff is to actually listen to the
equipment, and ignore the hype.  Don't rely on original price as an indicator
of quality, either; there's a lot of bullshit, especially toward the higher
end of the audio market.  If you can, try to listen to multiple items of the
same type with the same music.


#17 of 47 by gull on Wed May 8 15:40:20 2002:

Also, a buck spent on better speakers is worth ten spent on anything 
else.

Don't let anyone sucker you into paying for really expensive speaker 
wire or interconnects.  In the case of interconnects, as long as 
they're well shielded and have good connectors, you're fine.  In the 
case of speaker wire, the only thing that really matters is that the 
wire gauge is correct.  (i.e., large enough that you don't loose 
excessive amounts of power.)  There have been double-blind tests that 
showed audiophiles couldn't hear the difference between super-expensive 
exotic speaker cable and ordinary zipcord from the hardware store, and 
there's no physics that says they should be able to.


#18 of 47 by jmsaul on Wed May 8 21:30:34 2002:

I agree with gull on wire and interconnects, but if your speakers are much
better than the rest of your equipment they'll just make its flaws more
obvious.


#19 of 47 by scott on Wed May 8 23:10:09 2002:

I don't agree with the "speakers are too good for the other components"
argument.  I suppose shitty speakers would sound better somehow?  ;)  Buy good
speakers, and if you then don't like your whatever else you can buy a better
one next year.  

(Caveat:  It's possible that the really good speakers are less efficient than
the OK ones, and therefore need more power which the amp may not have.  I'd
buy that argument.)

Yeah, don't spend any real money on interconnects.  Buy the basic cables at
Radio Shack (cheaper than Meijer, last I looked), and use lamp cord or
whatever for the speakers.  I used to read rec.audio.high-end years ago, and
some people were claiming that *thinner* speaker cables sounded better!  Some
people also swore by Romex, that AC stuff in the walls of your house.


#20 of 47 by other on Thu May 9 00:24:59 2002:

Probably well shielded cables are better than non, unless you're sending 
a balanced signal to the speakers.  Of course, if you're sending a 
balanced signal, then interference is irrelevant, so any cable will be 
fine so long as it isn't small enough for its own resistance to become a 
problem, but you'd still need a speaker with the capability to receive 
and interpret a balanced signal.


#21 of 47 by keesan on Thu May 9 01:06:59 2002:

You can get speakers cheaper if you are not trying to play things very large
or very bassy.  Or get good headphones.  I find the antenna is the most
important thing when listening to radio.


#22 of 47 by jmsaul on Thu May 9 02:39:13 2002:

Re #19:  I've experienced the "speakers too good for the other stuff"
         thing myself, when I hooked a pair of Linn Nexus up to a
         mid-range Denon receiver (the source was an NAD CD player, which
         was fine).  The Denon was designed to work with lower-quality
         speakers that emphasized the low end more, and everything
         sounded... ethereal through the Linns.  A better amp fixed the
         problem -- but I hadn't noticed the problem with my Polks.

         There are basically two strategies for buying audio over time:
         improve speakers first, and improve source first.  I guess it
         depends on what you want, but I'm for the second one provided
         the other stuff in the chain is at least competent.


#23 of 47 by gull on Thu May 9 14:39:56 2002:

Re #20: Usually interference isn't an issue with speaker wires because the
signal levels are so high.  The exception is when the speaker wire acts like
an antenna, and picks up a nearby amateur radio operator or AM station.  If
you do decide to use shielded speaker wire, follow good grounding practices
-- ground the shield at one end, and only one end.  Ideally you want your
system grounded in a "star" pattern -- all the ground connections should
come back to a single point.  That can be hard to achieve, though.  I have a
problem with mine because the computer is grounded through its plug, and the
VCR is grounded through its cable line, and both are connected to the same
amp.

#22 sounds like an equalization problem -- the Denon amp must have had
excessive low-end roll-off.  I don't have any equipment a serious audiophile
wouldn't turn up their nose at, though, so the amount of advice I can give
is fairly limited.  I will say that NAD will forever have a special place in
my heart for running a campaign with the slogan "Go NAD!" ;)


#24 of 47 by krj on Thu May 9 22:27:01 2002:

My feeling is that the advent of CD players largely demonstrated the 
correctness of the Linn approach of improving the source of the music
before anything else in the chain.  ( 1/2  :)  )    (Joe Saul knows
this, but for everyone else: Linn makes very high-end turntables, 
I've heard them sound very nice in the store but I was never willing
to spend that sort of money on components.)

Low-priced CD boom boxes now sound better than most home component
systems based on turntables did, in the LP era.

Of course right now most of my listening takes place in either two 
forms:  (1)  44K Real Audio streams, or (2) in a car with crummy 
door seals moving at 70 MPH...   and sometimes both...   


#25 of 47 by other on Thu May 9 23:27:28 2002:

Funny we should be having this conversation now.  Today I was trying to 
fix a noise problem with a some powered computer speakers and concluded 
that the office they were in was just flooded with RF noise.  The little 
stereo mini cord by means of which the computer audio was fed to the 
speakers was acting like an antenna and doing it waaay too well.  I 
unplugged the cord from the computer and held it up and you could clearly 
hear at least a couple of radio stations playing through the speakers.  I 
told the person whose office it was to try wrapping the cord in aluminum 
foil.  Or wallpapering in it...


#26 of 47 by jmsaul on Fri May 10 04:00:07 2002:

Re #23:  It's possible.  I'm a knowledgeable consumer of audio, but I'm not
         a technical expert.  However... if you believe that the job of the
         pre-amp, amp, and speakers is to accurately reproduce your source,
         it makes sense to upgrade the source first.

Re #24:  Linn also makes very high-end CD players.  Yes, you can hear the
         difference (no, I don't know why, but I've a/b'd them, and you
         can).


#27 of 47 by scott on Fri May 10 12:41:31 2002:

It's relatively easy and cheap to make a good amplifier instead of a cheesy
one.  Transducers are much tougher, so speakers are usually the weakest link.
Back before CDs it was speakers and turntables.  Now it's pretty much just
speakers, although there's plenty of arguments going around about CD players.


#28 of 47 by jaklumen on Fri May 10 13:44:06 2002:

resp:26 how much money we talking about for these Linn CD players?

resp:27 well, how do you do that?  Most A/V receivers aren't modular.


#29 of 47 by jaklumen on Fri May 10 13:45:25 2002:

whoops-- btw, scott or krj-- could you link this to the music conf, 
please?


#30 of 47 by gull on Fri May 10 13:54:27 2002:

Re #25: The best trick is to wrap the cord around a ferrite rod or through a
ferrite toroid, near the end the amplifier is on.  Sometimes an iron nail or
a big steel washer works, too.  The idea is to create a choke coil that will
have a high impedance to RF, but will let audio pass unaffected.

Re #26: I'm a little suspicious of informal A/B tests, because they're so
susceptible to the placebo effect unless they're done "blind".  (People tend
to expect the more expensive equipment to sound better, and they hear what
they want to hear.) There are also a lot of subtle tricks...like if one
player's output level is slightly higher, it will sound 'clearer' in an A/B
test.

Re #28: My understanding is that audiophiles turn up their nose at A/V
receivers in general.  They aren't big fans of any of the Dolby surround
sound systems.


#31 of 47 by scott on Fri May 10 15:25:07 2002:

OK, I'll link this to the Music conf.  Good idea!  


#32 of 47 by jmsaul on Fri May 10 16:42:30 2002:

Re #27:  That's true, and it makes sense to upgrade the weakest link in
         your chain.  I was assuming all elements were of equal quality,
         but if not then upgrade the worst one first.

Re #28:  (Price of Linn CD players)  I think they have models that retail
         for ~$1300, ~$2200, and ~$10000 (not a typo).

         (Separating amp and pre-amp)  He wasn't suggesting that you build
         your own amp stage for an existing receiver, he was just saying 
         that at a given price point / level of quality the amp is likely
         to be empirically better than the speakers, because it's cheaper
         to do amps right.

Re #30:  (Informal a/b tests)  I'm suspicious of them for the same
         reasons.  I had a friend switch the equipment out, I couldn't see
         which one was running, and I know he didn't mess with the volume,
         but it's always possible that other factors (e.g. output level)
         confused the issue.  On the other hand, how else do you decide
         which you like better?  There really isn't an objective measure.



#33 of 47 by bdh3 on Sat May 11 05:07:35 2002:

What parts of your body do you use to listen to your stereo?
(got a tin ear?  then buy shitty speakers) 

Thus the speakers are the most important.  The problem is
good speakers will make a shitty system sound even more
shitty than shitty speakers will. (is simple physics)

Second is the 'input'.  A shitty media player will obviously
render the best speakers mute point.  GIGO, and the best
speakers will obviously only more accurately reflect the G.

Thirdly is the 'middle ware'.  This is the last place that
you should concentrate on.  (Unless you are listening to
(c)rap in what case obviously it is the first place U should
spend yer $ - GIGO again).




#34 of 47 by keesan on Sat May 11 12:37:50 2002:

Without a good antenna I cannot even receive the three radio stations that
I listen to, no matter how good the speakers.
Toroid - magnet from a hard drive or a speaker?


#35 of 47 by other on Sat May 11 13:55:29 2002:

A toroid is an object circular in shape, with a circular cross section at 
any point along its circumference.


#36 of 47 by other on Sat May 11 13:56:05 2002:

(A washer is like a flattened toroid.)


#37 of 47 by jmsaul on Sat May 11 15:08:37 2002:

Re #34:  That counts as part of the source.


#38 of 47 by i on Sun May 12 04:19:00 2002:

Toroid = bagel with a carefully-centered hole.

CD player technology moves fairly fast.  There are probably loads of not-
the-current-model Linn CD player available much cheaper on the used market.

I've got "fancy" twisted-pair speaker cables.  I got 'em when living in a
ham radio operator's house.

Good speakers:  there are two different ways for a speaker to be good -
it can have good bass response, or it can do a good job with whatever
(limited) part of the audio spectrum that it does reproduce.  Both kinds
of good tend to cost money and the bass kind generally means physically
larger speakers, but there are plenty of crappy speakers out there, so
don't assume that big and/or expensive guarantee you anything.  Think
about what kind of good you really want *before* spending money.  I've
got poor bass (dinky & ported) but pretty-good sound speakers.  This is
good for life in a quiet apartment building.

A/B testing:  even if your awesome hearing notices that the $10,000 
stereo system sounds better than the $8,000 stereo system, aren't there
loads of other things you spend money on (car, house, vacation, eating
out, computer, etc.) where A/B testing would reveal that an extra $2,000
would get you something better?


#39 of 47 by keesan on Sun May 12 13:49:47 2002:

You can spend a lot more on speakers if you want them to sound louder, or get
smaller cheaper ones and sit near them in a small room.  Some speakers are
designed to overemphasize the bass, which seems to be important to people who
want to feel the music through their feet.


#40 of 47 by jmsaul on Sun May 12 14:03:34 2002:

Re #38:  (Used Linn CD players):  There sure are.  I've gotten all but one
         piece of my Linn gear (a CD player, ironically) used.  Linn's 
         stuff is very reliable and durable, so buying it used isn't much
         of a risk.  (If you're going to, though, email me first.  I know
         where to look and can check serial numbers too.)

         (Good speakers):  Personally, I'd prefer to have smaller speakers
         with excellent sound reproduction and minimal bass, rather than
         big speakers with tons of bass but lousy sound reproduction.  You
         can obviously get speakers with great reproduction and lots of
         bass, but that costs more.  I finally did it, because we have a
         big living room.  You can get something very good for $1500 or
         less.

         (A/B testing):  Yeah, you have to do a cost-benefit analysis on
         that kind of thing.  ;-)  Probably the most cost-effective thing
         I've ever done to improve sound quality in our house was to buy
         curtains for the huge window behind the couch...

Re #39:  Many speakers, including the majority of floor-standing speakers
         you'll see in appliance stores, etc., are designed to overemphasize
         the bass.  It's cheaper to do that, and since the people who buy
         them have crappy sources, it also helps hide that.  Smaller speakers
         aren't necessarily cheaper, though; there are some excellent small
         speakers out there that simply reproduce the upper and mid range
         very, very well.  Price doesn't necessarily corrrelate with  either
         quality or loudness.


#41 of 47 by keesan on Sun May 12 14:08:03 2002:

Good speakers have a level response curve (they don't have peaks or valleys
at certain frequencies).  It is probably more expensive to get the curve level
at higher volumes so you can get cheaper speakers that sound just as good if
they don't have to play as loudly.  Consumer Reports published one review
showing all the curves, and they suggested adjusting the speakers to give less
bass for many models, if you wanted the music to sound more realistic instead
of more bassy.  You can also adjust the receiver for more or less bass.


#42 of 47 by eprom on Mon May 13 00:07:47 2002:

I'm thinking about testing the whole system out. Tell me if this
sounds right.

1) Connect a sine-sweep generator to one of the audio inputs.
2) Set the (audio input) freq of the sine generator to 1KHz (reference
   tone) at 1 Vpp (audio input) and adjust the speaker volume (output)
   to say 60dB.
3) Take a SPL reading of the room without audio (noise floor). 
4) Set the sine generator to sweep from 20 Hz to 30 KHz and take readings
   on the SPL meter at various freqs?

The only thing i'm not sure of is the SPL meter, which seems a tad 
subjective (such as where it's placed in the room).

I have access to a oscilloscope but how would I go about getting a way to
measure the audio from the speakers?


#43 of 47 by i on Mon May 13 00:59:23 2002:

Ironic?  Since CD technology moves the fastest, it would be the reasonable
thing to get new in a all-but-one-piece-is-used system.

As keesan & jmsaul start to say, there are loads of things beyond generic
"bass response" and "sound quality" to picking speakers.  (The same is
true of other stereo piece-parts to a somewhat lesser degree.)  There is
no substitute for having someone who's familiar with both the products and 
your *real* wants help you select parts for your system.  Very-high-
efficiency speakers plus a huge amp are a money-wasting combination (well,
unless your goal is blowing out the windows); ditto low-efficiency speakers
and a nice low-power amp.  A CD player & speakers which are both a bit
heavy on the tweeter end of the spectrum sound great in a room that eats
high frequencies, but crappy in another room.  And so on....


#44 of 47 by scott on Mon May 13 01:54:26 2002:

Re 42:  The problem with getting the signal into your oscilloscope is finding
an accurate-enough microphone.  You might call around to audio places (and
car audio places) and see if they will rent you a spectrum analysis rig.


#45 of 47 by jaklumen on Mon May 13 02:05:33 2002:

oh, amen, brother.. acoustics of a room are a *big* deal, and it's 
generally a good idea to consider them when you're really serious 
about sound quality.

My understanding of bass is the speakers generally need a lot of air 
for the frequencies to move, or something like that.  More often than 
not, that means relatively large speakers, and a fairly large 
enclosure.  I remember reading a Sound & Vision article where the 
author strove for massive dB levels using 18" speakers with a 
downstairs basement as an enclosure.  To move all that air, you also 
need some oomph behind it, which makes me doubt crappy sources.  
Subwoofer speakers alone take up about 75% of your total power in a 
system, and this is generally why powered (active) subs vs. passive 
ones are popular.

My experience has been that vented ports are sometimes a good solution 
for midbass, but I haven't seen many subs that soar down to 13-20 Hz 
with one.  They just can't produce enough sound pressure.  But ports 
can be wonderfully designed to allow for smaller bass speakers; hence 
your "bass reflex" design, and the coiled tube design that is a part 
of the Bose Wave radios.

Passive radiators also tend to help with bass sound.  I'm not 
completely sure how they work, but I know that they are generally 
tuned to a particular frequency.. whatever low frequency you want 
emphasized, which is usually 40, 33, or 20 Hz.

As far as bass and acoustics, well, they are important, too.  Simply 
putting a sub in a corner will generally emphasize lower frequencies, 
as drywall needs to absorb frequencies above 40 Hz or so.  Many people 
have carpets in the room, but some have hard wood floors, so bass 
reverb can be a problem in the latter case.

There are some subspeakers available that can be mounted in the floor 
joists, or even inside furniture, but I think most people go with the 
separate floor speaker type that was designed by Infinity in the 1960s.


#46 of 47 by gull on Mon May 13 15:58:09 2002:

Re #41: It depends too on what kind of music you're listening to.  If you
listen to rock and you're trying to duplicate a concert sound, well, most
concert sounds systems are fairly bass heavy.  Likewise, pipe organ music
often contains a lot of deep bass.

Of course, these days a lot of people go for obviously unrealistic levels of
bass just because they like to make stuff rattle, and that's obviously
rubbing off on the manufacturers of stereo equipment.


#47 of 47 by jazz on Tue May 14 22:43:19 2002:

        Middleware can make some very noticeable differences if, for instance,
you switch to middleware that more easily supports Dolby Digital Surround
Sound.  Some features really are worth investing in.


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