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jaygeorge1979
10-25-2005, 03:15 PM
ok the search thing wasnt working for me, I am trying to figure a couple of things out:

what is a plate amp? is it a reciever?

what is a line array system or something like that?

If you build your own speaker box and buy the individual speakers, (woofer, couple midrange, tweeter) do you crossover each one individually inside of the box?

does the reciever you buy really influence sound quality to a noticable level or is it just the speakers?

do you guys buy seperate equalizers or doer your reciever do taht for you?

thanks to all who assist, BOOOO to all who refuse....:)

JimJ
10-25-2005, 03:24 PM
what is a plate amp? is it a reciever?

A plate amp is an amplifier mounted on a...well...plate. It usually mounts on the back of your sub enclosure.


what is a line array system or something like that?

A vertical row of speakers, designed to get very efficient and have excellent on-axis response.


If you build your own speaker box and buy the individual speakers, (woofer, couple midrange, tweeter) do you crossover each one individually inside of the box?

The crossover you use will divide the speakers into their respective frequency ranges, yes.


does the reciever you buy really influence sound quality to a noticable level or is it just the speakers?

If you buy a cheap receiver, it might go into clipping sooner, or build construction might be lacking...


do you guys buy seperate equalizers or doer your reciever do taht for you?

I did because I'm not using a receiver, but seperate components...higher-end integrated amplifiers and receivers do include some sort of onboard processing though.

PV Audio
10-25-2005, 03:33 PM
if you aren't watching movies, then don't get a receiver. i want to sell mine because i'll never have a tv in my room to watch a movie off anyway.

JimJ
10-25-2005, 03:35 PM
if you aren't watching movies, then don't get a receiver.

:confused:

No, I think the correct thing to say is "If you don't care about broadcast band reception, or are serious enough about it to invest in a seperate tuner, don't get a receiver".

PV Audio
10-25-2005, 03:42 PM
tsk tsk, i was alluding to an integrated amp. those receivers with 12.1 surround and 50 million features don't help the quality of the sound if u are just doing stereo, they just hurt your wallet.

MastaFlex
10-25-2005, 03:49 PM
The receiver i bought for my room i got for my surround sound system. Also i got it for my tv, but the main reason was so i had a place for my Cd player - aka the 6 disc changed i bought for it to plug into something. I think it was a great buy on my part. The reciever is great quality, works great for my sound system.!

thylantyr
10-25-2005, 04:25 PM
A vertical row of speakers, designed to get very efficient and have excellent on-axis response.

Could be horizontal, could be 'J', could be leaning, like the tower of pizza[:yumyum:], could be upside down on the ceiling, :typing: :patrioti:
... also could be this stacked
http://cover6.cduniverse.com/CDUCoverArt/video/6811719.jpg

Line Ray :smokin:

jaygeorge1979
10-25-2005, 11:11 PM
Mr. Frost...you sure know your stuff...now, this line array business...why is it good to have to have "on axis response"? i mean, how does taht differ from regular speakers cabinets?

so a plate amp is only an amp used for a subwoofer mounted to a box? so u wouldnt use a plate amp to power, say, tower speakers or the center?

As far as equalizer goes, you said most recievers have some kind of sound processing? If not, shouldnt the crossovers put the right freq into the speakers? or would i need to buy a seperate equalizer for that?

thanks for ALL help :)

JimJ
10-26-2005, 02:13 AM
What I meant by on-axis response is that the speaker has a high soundstage - a wider "sweet spot" up/down vs. side to side.

Plate amps are generally used to power subs - but if you had a Class A/B plate amp, you could use it to power full range speakers. They're just less flexible to use, IMO, than a dedicated power amp.

The Xovers on the speakers are only part of the system :) Sometimes, you want an EQ to tame any harsh responses you might get in-room, or to tune the system for personal taste.

PV Audio
10-26-2005, 09:20 AM
this is only a theoretical guess, but will you have less beaming with a line array? i haven't heard a DIY one, so i can't say.

jaygeorge1979
10-26-2005, 10:48 AM
what is beaming?

and what is a dedicated power amp as opposed to a plate amp?

im learning so much...keep the answers coming :-D

JimJ
10-26-2005, 10:52 AM
Beaming...a good example of this is a larger diameter driver (like an 8") playing high frequencies. Once you move out of the driver's "sweet spot" on-axis (with the driver pointing directly at you), the sound begins to suffer.

Some speakers (like my Klipsch Forte II's) actually sound worse pointing directly at you.

By a regular PA I mean...well, like a regular piece of on-the-shelf equipment :)...because most don't use plate amps for powering their main channel monitors.

jaygeorge1979
10-26-2005, 11:22 AM
so beaming is the term used to describe poor sound quality outside of the speakers sweet spot...if i am not in the sweet spot, and i hear crappy sounds, i call it beaming?

im not really understanding how an 8inch driver playing high frequencies relates...unless by sweet spot you dont mean where you are sitting, instead a sweet spot is the recommended freq range? ahh im confused agian...

PV Audio
10-26-2005, 01:04 PM
think about the higher range of sound as a flashlight versus a lightbulb. the lightbulb is turned on when in the optimal range, and the smooth sound (hence sweet spot) has excellent soundstage and imaging. now, take it out of it's ideal environment and u turn on the flashlight. the flashlight is very monodirectional and when pointed at you, it is uncomfortable on your eyes, much like a beaming speaker on your ears. so frost, that is what i was asking. do line arrays suffer from beaming much because of the multiple driver use?

squeak9798
10-26-2005, 01:15 PM
so beaming is the term used to describe poor sound quality outside of the speakers sweet spot...if i am not in the sweet spot, and i hear crappy sounds, i call it beaming?

Not just "poor sound quality", but actual decreased off-axis output (increased directionality). The higher in frequency you go, the more directional the speaker will be become.

It has to do with the relationship between the length of the soundwave and the diameter of the cone. Because of this, obviously, with a large cone you are going to run into more beaming issues sooner in the frequency range.

Some speakers may just sound like crap off-axis. Doesn't inherently mean it is beaming.....just that that particular speaker sounds like crap off-axis.

Beaming is a certain relationship (wavelength to cone area), causing a certain effect (increased directionality)



im not really understanding how an 8inch driver playing high frequencies relates...unless by sweet spot you dont mean where you are sitting, instead a sweet spot is the recommended freq range? ahh im confused agian...

It was just an example, since an 8" woofer will begin to beam at a *relatively* low frequency.

A good read on the subject of beaming: http://forum.carstereos.org/showthread.php?t=41151&highlight=beaming

PV Audio
10-26-2005, 02:30 PM
squeak, does it hold true if you use many smaller diameter cones versus one large one (thus my line array question).

jaygeorge1979
10-26-2005, 03:51 PM
is on axis and off axis simply a result of whether or not the speaker is pointed AT you or not direcltly at you? is off axis response a good thing? does beaming occur only on axis? what exactly does beaming sound like?

JimJ
10-26-2005, 03:55 PM
is on axis and off axis simply a result of whether or not the speaker is pointed AT you or not direcltly at you?

Yup.


is off axis response a good thing?

Yes. A speaker that throws a wide soundstage and is more forgiving where you sit is a very good thing.


does beaming occur only on axis?

Beaming is a very narrow on-axis response. Move beyond that, you start hearing it drop off...

Being too far off axis to a speaker can result in some funky things...Fostex and Lowthers, for example, have a very nasal and honking characteristic if no phase plugs are used and they're placed facing away from the listener.

squeak9798
10-26-2005, 04:34 PM
squeak, does it hold true if you use many smaller diameter cones versus one large one (thus my line array question).

I presume you mean something like.....a single 10" driver vs. an array of 3" drivers accumulatively totaling the same Sd as the single 10"?

Line array's aren't my forte.....but my guess would be that beaming for the array would occur at the point that it would for the single individual smaller driver.

I'd have to do more research to actually back that up, however.

thylantyr
10-26-2005, 04:52 PM
Nothing in my post is written in stone, there is a tolerance for error just
in case one of those line array scientists intrudes on the discussion with
esoteric response. Try to keep the understanding the line array simple,
then it all becomes easy. Don't cloud your mind with too much science
otherwise you'd never build one.

Jim Griffin's line array document.
http://www.audiodiycentral.com/resource/pdf/nflawp.pdf

If you use cone drivers there is a formula to give you a maximum
recommended crossover point to minimize comb filtering.

It's

13560/driver center to center spacing.

If you want to make line array with 4 inch midranges and the center to
center spacing is 4.5 inches, plug that number into the formula and
you get 3013hz or ~3khz is the maximim recommended low pass to use
on the 4" drivers.

If you want to use 8" mids, with 8.5" center to center spacing, then
1595hz is the max recommended crossover point.

Are these numbers written in stone? .... no
You can cheat. If you increase your listening distance cheating doesn't
sound that bad.

Re: Beaming. Horizonal dispersion is limited to the performance of the
single driver. If your 4" drivers @ 3khz crossover has better off axis
performance than an 8" driver @ 1.6khz then the 4" will be have higher
horizontal dispersion.

But if you use a 1khz crossover point for the 4" and 8" then you may not
be able to tell the difference.

Beaming is over-rated if you are building a system just for you and not
an audience because you can design your loudspeaker to be toed in
for sweet spot listening. The NSB/PT2 array I made has a turntable mechanism
so I can rotate the array for whatever listening position I'm in. If I'm sitting
on the couch in the center, I toe in both arrays equally so the drivers are
pointing at me for optimium sweet spot. If I sit on the left side of the couch,
I toe the left side less and right side more. This is an array with 4" drivers
crossed over at 1.7khz, so because these drivers are not operating at very
high frequency there is less beaming and the tweeters are really the focal point
of the system. So, the sweet spot is really based on the tweeters not the NSB's.

On the other hand, if you designed your array where the midranges are doing
higher frequencies then aiming those midranges might be more important.

When you make a vertical line array from floor to ceiling, stacking drivers on top
of each other and obeying the generic comb filtering rules, it would give you
the illusion of having very high vertical dispersion because you can hear the
sound whether your head is low to the ground or way up high near the ceiling.

Comb filter is hard to grasp for some people. The best way to describe this is
to visualize it. Get two 15" subwoofers and place them 3 feet apart. Stand in
front of one of them and move towards the other sideways, did the sound change
or did you hear the same amount of bass? Most likely it sounds the same.
What if you spaced those woofers 500 feet apart? Yes, you can hear a difference
as you move from one woofer to the other.

Do this same test with two tweeters. Get two tweeters spaced 3 feet apart.
Stand in front of one and listen, then move your body sideways to the other
one. Did the sound change? Probably, because when you stand in the 'line of fire'
staring at the tweeter the sound is in your face, but as you moved away you
heard it less and started to hear the other one more. This is like comb filtering.

To minimize this perception you need to place those tweeters very close together
so you don't hear the 'voids'. You can see how lower frequencies are more forgiving
to distance than the higher frequencies. That's why if you make a line array with
domes that have excellent dispersion, it's best to keep the center to center close,
ideally less than 1.5". If you use planars or ribbon type of tweeters, because they
have weak vertical dispersion, you can just stack them and the void between
elements isn't as critical, but at very close range you will be able to hear the combing
effects. The ideal planar or ribbon is contiguous, ie buying a one piece element that
spans the whole floor to ceiling instead of using stacked smaller tweeters.

The bottom line is. If you listen to your array at greater distances the more error your
design can have and stlll sound excellent. But if you don't have that luxury and want
to listen to your array .. lets say 5 feet or closer, then you have to pay attention to
comb filtering more so you don't hear these 'voids'.

PV Audio
10-26-2005, 06:26 PM
I presume you mean something like.....a single 10" driver vs. an array of 3" drivers accumulatively totaling the same Sd as the single 10"?

Line array's aren't my forte.....but my guess would be that beaming for the array would occur at the point that it would for the single individual smaller driver.

I'd have to do more research to actually back that up, however.
precisely :)