Heritage Center Channel

[DrWho]

This came up in another thread and I thought I'd make a new thread to see if we can't get some more definitive answers.

For

example, what is the raw sensitivity of the K400 and K77 and all that?

And what are the available tap-settings? I seem to recall a lot of

variation in these numbers so am kinda wary of taking any of the

numbers I find in old posts. Heck, even the Klipsch website speaker

info isn't consistent [] Does anyone have the raw frequency response

measurements with calibrated SPL?

The initial design I was

hoping to go with involved a pair of the Eminence Delta Pro-12A

drivers. They are 8 ohms @ 99dB with 2.83V so a pair wired in parallel

is going to yield 4ohms @ 105dB with 2.83V. I've seen specs quote for

the lascala between 102dB and 105dB, which means these drivers will

definetly be able to keep up.

The other advantage to these drivers is they have a very similar raw

frequency response to that of the lascala - so voicing should be

similar if done correctly (gonna have to play with baffle layout to get

the dispersions as close as possible). I don't think 5 cubic feet is

too incredibly big when you consider the necessary depth for the K400

(~2 feet). This requires a cabinet roughly 3 feet wide and 1 foot tall

- which is about the minimum necessary for dual 12's and the squaker in

the middle.

[DrWho]

Btw, can anyone verify the numbers in the attached pdf?

LaScala11.pdf

[DrWho]

Here's the best freq. response curve I can come up with (yuck). Lascala is on the bottom, khorn on top:

[DrWho]

And the drivers are available from PartsExpress:

http://www.partsexpress.com/pe/pshowdetl.cfm?&PartNumber=290-510

($126.09 EA (1-3) x 2 = $252.18)

The Eminence product info page:

http://www.eminence.com/proaudio_speaker_detail.asp?web_detail_link=DELTA%20PRO-12A&speaker_size=12&SUB_CAT_ID=1

spec sheet:

http://www.eminence.com/pdf/deltapro-12a.pdf

and recommended cabinet designs:

http://www.eminence.com/pdf/cab-deltapro-12a.pdf

I figure once we gather all this info that we might as well put it all together into an article and put it on the klipschcorner website that we can have a single reference instead of digging up old posts all the time.

[BEC]

Sensitivity of the K-400 with K-55 driver is about 107 db at one watt.

Frequency response is here:

http://forums.klipsch.com/forums/thread/773013.aspx

Sensitivity of the K-77 is about 104 db. Varies quite a bit between samples of the tweeters though.

Frequency response is hard to quantify since some only make it to 12 khz and the best go to somewhere around 16 khz.

Bob Crites

[DrWho]

Wow, that was fast. Thanks Bob. Just outta curiousity, what would be the sensitivity of your tweeter? I didn't get a change to hear it in Hope and was kinda bummed...

This is just for convenience:

Looks like 600Hz would make a good crossover point regardless of squaker type? That's probably a bit high for how far apart the woofers will be.

[BEC]

Supposed to be 105 db. But it is almost identical in output to the K-77 until you get to the area where the K-77 quits. The CT125 just keeps on going up to 20 khz.

Bob

[colterphoto1]

never mind

[Daddy Dee]

DrWho,

That will be an awesome center. Can't wait to see your project will look like upon completion.

BTW, have you ever checked out the CT-125's? To my ears, they were a significant improvement over the K77 and were my preference to the Beymas, which I had been using in my Khorns. The realism in the cymbals sounding live was what got my attention.

[jwc]

Mike,

Are you planning on putting the K401 and K77 between 2 12 inch woofers....all aligned horizontally?

[Guest " "]

You might want to consider the ST-350 as well.

[damonrpayne]

Have you given thought to cabinet construction? Maybe we can get popbumber to build them?

Be sure to have all the bugs worked out byt the time I can afford the LaScala II .

[DrWho]

Mike,

Are you planning on putting the K401 and K77 between 2 12 inch woofers....all aligned horizontally?

Ya...it's

crazy I know. I'm working on the feasibility of a slightly modified

motorboard that will both increase horizontal dispersion and bring that

105dB down to around 104dB so that only one autoformer is needed in the

crossover. Of course, it'll need to be easy to build too - and not

affect the performance of the K400.

My computer has exploded actually (writing in the labs which I normally

do cuz I seem to be stuck here all the time), so it'll be a bit before

I can get some of the drawings out. Maybe I'll just recreate some later

tonight and y'all can critique away.

It will also be rear ported - unless I can tuck them up beside the tweeter (and avoid any diffraction effects).

[tagger]

Is there any notable disadvantage to it being rear ported?

[DrWho]

A 55Hz tuning will have wavelengths on the order of 20 feet coming out the port, which will easily "wrap around" the cabinet and still be in phase with the woofers. At louder SPL's the port chuffing (if there is even any) will be less audible than in the front. The downside is an ever so slight loss in efficiency (since the wave is travelling further) and it is harder to position (gotta have enough breathing room). I believe the RC-7 is rear ported, but Klipsch has moved to front ports on all the new reference centers...

Another idea I'm mulling over is that of a taperred array crossover, which is another thing Klipsch is doing with their reference centers. However, they are crossing over much higher in frequency (where it's a bigger concern).

[colterphoto1]

Is there any notable disadvantage to it being rear ported?

I think rear porting limits the usability of what is already a rather large cabinet in probably cramped surroundings.

Any way to make em front ported Doc?

M

[damonrpayne]

I think Doc's rear ported design had the ports behind the drivers, so the overall surface area of the front panel was in line with typical center channel form factors? At least, that is a worthy goal IMHO.

[jwc]

Mike.

I went through this whole process a little over one year ago. I didn't go the route you are seeking.

Sounds to me like you consider the ideal Heritage center To have a matching SPL and incorporate the K400.

Seems you also are trying to make a "shape" like the modern center channels.

I was against rear porting after long hard thinking. I have a Herescala that can be rear ported by changing the back plate. However, I don't fell it is necessary since I have it as "small" in my HT processor. You may be doing to affect overall SPL.....let me know.

So I have the K77, K55/K401 and one k22. All Alnico. This is the shape of a La Scala but "mini.

The SPL won't match what you are doing although fairly close to what heresies or Cornwall's do.

I thought about the dual 12's to accomplish what you are doing but I felt it was too much and it would be very wide.

Just some input.

here:

http://forums.klipsch.com/forums/thread/611692.aspx

jc

[DrWho]

The ideal center IMO is simply one that sounds identical to the mains...

To achieve this I believe you will need an identical on-axis response

with similar distortion patterns and as close as possible power

response (identical off-axis behavior). And according to PWK and all

the boring physics, distortion is mostly related to the efficiency of

the design - so though an identical distortion distribution won't be

possible with the lower registers, the magnitude of distortions will be

about the same if you maintain the same system efficiency.

Due to the physical position of the center channel in relation to the

mains (~1/3 space versus 1/8 space), you're going to need a little

extra oompf on the low end. And even though you're going to set it

small on the reciever, you still need extension below the crossover to

ensure a smooth crossover transition to the subwoofer. The port tuning

also works to minimize cone-movement, which is going to further

decrease distortion.

The lascala bass bin is already wide, so achieving a similar horizontal

dispersion shouldn't be too difficult. The vertical dispersion however

is going to be uncontrollable and very different, which is annoying

because the number of early reflections in the vertical plane is going

to dramatically increase (moreso when you consider the center channel

is probably going to be mounted up higher in the air).

So with all that in mind...identical won't be possible, but we can get

it close. The horizontal array is by nature a compromised design, but

it seems to be the most feasible shape to accomodate most listening

environments.

Front porting would be ideal, but it's also going to increase the size

of the front baffle. There is some room between the corners and the

drivers (round shape on a rectangle) and then there should be some room

between the tweeter and the woofers. But I've never been a fan of ports

so close to the tweeter because when you start cranking it, you can

hear the port chuffing modulate the higher frequencies. That leaves the

corners, which doesn't leave much room. Maybe these might be a viable

option?

http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=260-713

One downside is that once you start getting funky with the shapes, you

start introducing more distortions in addition to the actual port

tuning being harder to predict.

Anyways, that's what's going through my mind right now. Today is my

busy day with classes, but I'll try to get up some drawings in the near

future - and if I'm feeling adventurous I hope to do a few 3D drawings

as well.

[theplummer]

Hey Doc,

Its been a while, Just a thought about porting, try to think Cornwall when thinking about porting. Seems like a 1" by whatever port uses less room than a round port, plus it would be forward firing. I think something like my academy only larger with a cornwall port could be the ticket.