Make a homemade Legend center?

[redtop]

Billy,

The cabinet shop is a good idea if you don't have the tools and/or the

skills to be precise. The speaker cabinet must have a tight air

seal except for the ports. If not, you risk ending up with a

speaker that does not sound as good as your C7. You can also end

up with a cabinet that makes "fart" type noises through the air leaks.

(Sorry for the language Amy! [:$])

I run my center small, but the sub-woofer crosssover is at 90htz.

The woofers are still quite active up to 700htz where the woofers hand

off sonic duties to the mid-range horn. I trust the engineering

at Klipsch and would be very careful about leaving out anything in

their design.[]

[wstrickland1]

The motor board is just hot-glued to the cabinet, so you should be able to work it loose without destroying anything.

especially with the glue they were using[]

[wstrickland1]

Willie, HTH are ya? Hey, I saw George Hamilton on a Dell HDTV commercial last week. I L'd MAO.

Billy

[wstrickland1]

Thanks Redtop, that's the route I'm gonna take.

[SCOOTERDOG]

Here is a pic of the one I built. I did have the motorboard done by a cabinet shop and it made a big difference.

scooter

[DrWho]

I just wanted to mention that there is an advantage to placing the

woofers as close to the middle as possible. It seems everyone doing the

center channel mods are spreading the woofers out, but they really

should be touching the sides of the squaker, or comes as close as

possible. It increases the highest frequency that can be played by both

woofers without decreasing the dispersion and causing comb-filtering.

[redtop]

Interesting Dr. Who...

I've never heard that reasoning on the woofer positioning and it

sounds like good sonic science, but I could use some

enlightening. Can you elaborate a little more? Is this a

theoretical problem or something I can hear? Is is an issue just

because the width of the speaker cabinet is abonormally large for a

center? The reason I ask is, as I remember my KLF-C7's, the

woofers are not squeezed up against the horn in the center.

Thanks in advance.

[redtop]

Thought of another question regarding my last post. I'm getting

ready to place the center behind an acoustically transparent screen and

I have heard the term "comb filtering" used in some of those

discussions. If my woofer spread is going to compound something

in that setup, I would appreciate your thoughts on that as well.

Sorry to get this thread a little off topic.

[DrWho]

Interesting Dr. Who...

I've never heard that reasoning on the woofer positioning and it

sounds like good sonic science, but I could use some

enlightening. Can you elaborate a little more? Is this a

theoretical problem or something I can hear? Is is an issue just

because the width of the speaker cabinet is abonormally large for a

center? The reason I ask is, as I remember my KLF-C7's, the

woofers are not squeezed up against the horn in the center.

Something you can hear? hmmmm...

Comb-filtering is a frequency respone that looks like a comb...lots of

dips which get bigger and closer together as the frequency increases

and it also increases as you move further off-axis. The reason being

that when you sit right in front of your speaker the sound from each

woofer arrives at the same time. When you move to the side, sound from

the woofer closer to you arrives before the woofer further away. For

each frequency in question this delay causes a specific shift in the phase which

then causes an interaction and you get the characterstic comb-filter

response. Here are some pictures and links over at prosoundweb that

discuss this much further with emphasis on the impact of live sound

applications, though the physics are the same for speaker design as

well (the "1/4 wavelength" distances are small which means it starts to

have an impact at larger frequencies):

-http://www.prosoundweb.com/install/cpm/lobes/lobes.php

-http://www.prosoundweb.com/live/articles/jbrusi/pa.php

-http://www.prosoundweb.com/studyhall/jbl/lfpc/lfpc.php

So how audible is this? Well the first article mentions that there is

some debate over the matter and draws a conclusion that the effects are

still important for other reasons (gain before feedback). I personally

find it to be very audible. If you want to demo for yourself what it

sounds like, take both of your mains and

feed them a mono signal. This is best to do outside so as to eliminate

the room from being a factor. Now walk around from side to side and

notice how different it sounds at different positions. This is comb-filtering. So will you hear

it? Probably not because you're most likely sitting at the main

listening position where every speaker is equidistant from you. The

person sitting next to you will hear it, but probably won't

notice...but if you move around the room then it quickly becomes

apparent because the sound is always different. Moving the drivers

closer together results in a more even coverage - aka it sounds the

same at every seat in the house. Btw, this is the effect of the direct

sound...keep in mind that about half of what we hear comes from the

reflected sounds too...so you will be hearing some of the

comb-filtering even at the main listening position.

I know just about everyone building their own speakers around here

claims they can't hear it, but perhaps it's because they have DIY

syndrom and anything you build yourself will sound better to you than

it actually does. I might also be more atuned to it because I deal with

it all the time when setting up venues (trained ears and all that).

This is a total side note, but one of the first things concepts I teach

to someone learning how to mix is the effects of comb-filtering (I

don't call it that at the time of course). The number one problem with

live-mixers that I see today is the "tweaky syndrom." All the time I

see guys turning all the dials half a notch here and there and they do

it constantly through the show. I'm sorry, but there is no way your

system is accurate to within half a decibal for every seat in the house

- if you're going to make a change, make a big one and think about it

ahead of time. It's amazing how much cleaner things sound when you take

this approach. End sidenote []

As far as transparent projector screens...I believe the concept is that

comb-filtering

occurs from reflections off the screen that bounce back onto the

speaker and then again reflect back out into the audience. The

reflections that end up bouncing back out will be delayed ever so

slightly from the original sound source so the solution is to put the

speakers as close to the screen as possible. I remember

reading or hearing something about Klipsch testing this and the effects

were very minimal in the cinema setting (which are using much bigger

speakers and a thicker screen). But don't take my word on it because I

really don't know.

Another factor with driver positioning is that it affects the polar

response of the driver. It may seem counter-intuitive at first, but

adding drivers in the horizontal plane reduces the dispersion

in the horizontal plane. Likewise, adding drivers in the vertical plane

reduces the vertical dispersion. So with the same drivers and spacing,

your KLF-30's will have a wider horizontal coverage than a horn-edized

center channel. The end conclusion to all this is that it is bad to

have a horizontal center, but it is a compromise made by speaker

manufacturers to make the center channel easier to position (because

proper positioning will have a larger effect on the sound). Thus my

sig: "It's all about compromise"

If you're going with a transparent screen, then I would highly

recommend going with a 3rd floorstander identical to your mains for the

center channel. You might also consider housing some DIY subwoofers

back there too....there's a lot of cabinet volume that can be tucked

behind a screen.

[wstrickland1]

Here is a pic of the one I built. I did have the motorboard done by a cabinet shop and it made a big difference.

scooter

Scooterdog,

How does you parts list read on that fine speaker?

[redtop]

Wow Dr.! Great reply! Very thorough and easy enough for a thick head like me to understand.

Your sharing is greatly appreciated.

[wstrickland1]

Is this Flight 1143 and is it on it's way to Cuba instead of Cincinatti?

[wstrickland1]

ya'll know I'm just kiddin

[redtop]

I hear Cuba is lovely this time of year...[]

I hope you know that even when we get off on a tangent with these "side

trips" they can offer perspectives never considered (but useful) by the

original topic. I've often learned more from a detour then my

main question. Please consider them just a "layover" on the way

to your destination. For my part in the hijack, I

apologize. I'll try to do better...or not (hehehe)[6]

Brad

[DrWho]

You old guys are so funny in that you get possesive about threads and their topics...

Everyone reading the thread reads the first post and most of the

replies and there is nothing stopping them from replying to the first

post...in fact, most people don't even read the other threads, post

their comments and move on.

I think the younger generation gets the hang of it better....a thread

is a main topic. And if that topic is of any interest there is bound to

be other related topics that get tied in (the crazier the connection,

the better). It's the tangents and side notes that keep things

interesting. Do we seriously want a forum where a person asks a

question, and only answers to the question are given? That would get

boring, but is why I'm working on a "pamphlet" (which is turning into a

book). Anytime someone asks a question I drop the book in their face

and then I can go talk about the goat I had that liked cheese, but I

ate the goat because I liked cheese too and didn't want him stealing it

anymore.

[redtop]

Old guys, eh????

Well take that <WACK> you young whippersnapper! []

Thanks again DrWho for your previous comb filtering post, I've been thinkin' bout some changes to my modded center...

[wstrickland1]

You old guys are so funny in that you get possesive about threads and their topics...

You young guys take stuff so seriously!!! That was old guy humor I was using. Heck, I can't believe a thread I started is up to 3 pages. Post on, young and old alike!!

[DrWho]

If you want a really long page count then open up a thread about tubes

and SS - start it off by bashing one topology and praising the other

[]

*rubs head*

[SCOOTERDOG]

Here is a pic of

the one I built. I did have the motorboard done by a cabinet shop and

it made a big difference.

scooter

Scooterdog,

How does you parts list read on that fine speaker?

Here is a link to my build site:

http://www.geocities.com/scooterb4u/Custom_Center.html

[formica]

If you want a really long page count then open up a thread about tubes and SS - start it off by bashing one topology and praising the other []

Or SET vs PP tube amps... vinyl vs CD... etc... i can't believe there is something which hasn't already been said about those ? [8-)]

-------------------------------

Combing effect is very real, and it's effects are far more important than enclosure proportioning mentioned earlier in this thread. Obviously enclosure volume and tuning are of primary importance but those we already have from a stock KLF.

BTW, having a centre channel with a narrower horizontal dispersion isn't actually a bad thing for imaging, but the increased vertical dispersion is (bad) due to the added floor and ceiling reflections.

Compromise it is....

Rob