Natalie P Center Channel and MT Surrounds

[bmuir]

First post here so be kind! LOL

I like the idea of the cost effectiveness and reported great sound of hte Natalie P towers using the RS28 tweeter. I would like to use them as the base of an upgrade of my HT.
However, it would be nice to have a Natalie P center channel design/crossover and a Natalie P MT design for surrounds. Is this possible?

I sent an e-mail to cjd on this and here is his initial thought to get the thread started:

CJD: What kind of frequency response are you looking for in your mains?

>>bmuir: -- frequency down to 80 Hz is fine as these will be integrated with a Quatro 15" sub)

CJD: The Modula CC was designed to match the Modula MTM mains, and there is also a Modula MT variant. As such, I'm not really sure it's the best match for the Natalie P tower. In fact, going with the RS28A on a 9"
tall baffle would not land you all that far away from the current Natalie P layout. Of course, the trouble here (and why that particular Scan tweeter was used) is that the further the mids are apart, the worse/lower the results from comb filtering. My RS150 MTM site has off-axis measurements that highlight this (a lower crossover on those, such as the one I proposed for use with the RS28A, would help, but not alleviate this issue). If you're not worrying about past 15-20 degrees off-axis, it's a relative non-issue in almost all cases though

bmuir: -- 20 degrees is fine in the 16 x 20 ft room).

CJD: A bigger issue is WHY you have such a limited space

>>bmuir--the center channel is housed inside the stand on which the TV sits and the available space is just 10 inches high), which suggests not only a 10" height limit, but a very different actual "baffle" dimension with respect to diffraction and more importantly, baffle step.

CJD: I suspect that a slight tweak of the Natalie P crossover would get you pretty darned close, though not quite as smooth as the mains. Knock out ~3-4dB of baffle step may be close enough - I did not find the vertical/horizontal on-axis measurements of my MTM to be significantly enough different where baffle step was not an issue.

However, since I am sure you're not alone in pondering this, why not post a thread up on HTGuide about it where everyone can contribute. We might even land a Natalie P MT variant as well.

Thanks

[cjd]

hmm, well I find I have nothing more to contribute since my comments are already here. :P Though you neglected to mention that your goal was to stick with the RS28A as tweeter.

The only thing I will add is that the "WHY" comment (re: cc placement and height restriction) wasn't a question. :P It was a prelude to the comment that by placing the CC in this cabinet, you would be looking at a different baffle dimension as seen by the drivers.

C

[GrahamT]

I might be interested in a NatalieP center channel too. I would love to build the ModulaCC but that little SS tweeter is $213 CDN. 8O

As Chris mentioned, the C-C spacing might be too far for the higher x-over point on the NatP. It might not work that well. A TM center might work better.

I know Jon is really busy right now too.

Bmuir,

For the surrounds, why not build the ModulaMTs?

[cjd]

Modula is a higher priced crossover and a different set of target slopes.

The TM fails the center channel height requirement.

MTM should be OK as long as it's not significant off-axis.

*shrug*

C

[GrahamT]

Modula is a higher priced crossover and a different set of target slopes.

I didn't think that the Modula MT crossover was significantly more expensive, but I haven't priced them.

The TM fails the center channel height requirement.

I meant to say a horizontal MT center. It has the potential for better horizontal dispersion, correct?

[Evil Twin]

The Modula MT is perhaps misnamed- it's crossover topology is essentially the same as the Natalie P, both being a modified series network... very modified.

Cost/performance considerations were paramount in both cases.

The Modula MT was a successor to the EM7.2, which was otherwise known as the Elaine Marie, so perhaps the Modula MT should be re-christened to the Elaine M2. Or, just call it "Yoda MT"? Sounds better than the "Jar Jar B". I think....

[cjd]

but...but... 27TDFC :P

Though the Seas tweeter versions would be quite a bargain. That's $100 savings by the time you've done a 5 speaker setup.

How do you feel about just using the Modula crossover on a horizontally set up speaker? And how 'bout the best way to negate a bit more of the baffle step?

C

[Dennis H]

but...but... 27TDFC

Maybe Evil Twin has a soft spot for cats and dogs and doesn't want to drive them out of the room. Whoda thunk it? :W

[cjd]

Maybe Evil Twin has a soft spot for cats and dogs and doesn't want to drive them out of the room. Whoda thunk it? :W

:crazy:

We all know better than that. :P

:rofl:

C

[Dennis H]

Seriously though, if we're doing a metal dome like the Seas, with a big resonant peak in the mid 20's, shouldn't we include a notch filter to protect our cats, dogs and children? We old-timers can't hear it but they can.

[cjd]

We old-timers can't hear it but they can.

Huh. I must be one of those three then, but can't quite figure out which... cat maybe. mmmm, spend all day napping with the occasional snack... please don't skin me!

C

[Dennis H]

Well, obviously you're "children" you young guy. (Old fart speaking).

[bmuir]

Okay. Looks like Modula MT with the RS28A tweeter will work. Now what about the center channel with the RS28A. Anyone have any ideas?

[Brian Bunge]

Chris,

Have you looked at modifying your own RS150 MTM xo's for horizontal use? I know you built one for your sister, but is it the same xo that you used for your MTM's or is it different? My thinking is using the 150's would make the CTC spacing slightly less and maybe the 27TDFC or RS28A would still work fairly well (no need to buy that expensive SS tweet). Just throwing out ideas plus I'm curious as to how it'd work seeing as I'd like to build your MTM's and a center using the same drivers for Ashley's dad sometime next year.

[cjd]

Chris,

Have you looked at modifying your own RS150 MTM xo's for horizontal use? I know you built one for your sister, but is it the same xo that you used for your MTM's or is it different? My thinking is using the 150's would make the CTC spacing slightly less and maybe the 27TDFC or RS28A would still work fairly well (no need to buy that expensive SS tweet). Just throwing out ideas plus I'm curious as to how it'd work seeing as I'd like to build your MTM's and a center using the same drivers for Ashley's dad sometime next year.

Have you looked at the page for those recently? :P

I have an alternat RS28A crossover with an 1800Hz crossover point that should be better suited for CC use. Haven't built 'em though, but I think there's not too much risk there. I specifically tried to make that so it was the same crossover either way (as long as baffle step needs remained unchanged) since that project is kind-of intended as a cross-over piece from more budget oriented stuff into the real high end drivers - it's the same box size as the Triune project (with similar goals) that Curt C put together.



C

[Brian Bunge]

Chris,

Yes, I had looked at it, but didn't seem to read carefully enough to notice that you mentioned using it atop a TV. I'll probably end up building them as towers for the front L/R and this size for the center. I think they'd be a big step up from his Klipsch speakers, especially the center channel.