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Discussion Starter · #1 ·
I was wanting to build some Natalie P towers and matching center channel for my mom. I have a question about making the towers. I have seen many people that build a full tower for this platform. They are using the extra box volume to get lower extension. Doesn't this change the crossover needed since the internal volume is changing. I realize that some people just make the Natalie P's look like towers, but they are simply mounting the normal configuration on top of a bottom box to make it look like a tower. There are also people that change the internal volume all together, and actually make a tower out of it. I figure that if I am going to make it look like a tower, I might as well get the extra extension that the extra volume provides.

Can someone lead me in the right direction to accomplish what I am wanting to know. I mainly just want to know what volume I need to stay at for a tower, and if there needs to be a change in the crossover.

Thanks in advance.
 

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Good choice!
http://www.htguide.com/forum/showthread.php4?t=30536

You've been advised correctly. LF tuning is independent of XO design. I made mine 65l, using the added volume to create an "extended bass shelf" or EBS alignment. This trades mid-bass output for increased bass LF extension, relying on room gain to fill in the lost mid-bass while extending LF even farther. My port tuning is ~23Hz. I'd give you deails, but it's a slotted port, which makes it somewhat unique to my design.

An EBS alignment is a very good idea if you're only making her an LCR. If there's any chance for a sub, you may want to stick with a smaller, sealed driver volume, regardless the external form factor. You can also model all this yourself. If you have Excel, look for "Unibox," otherwise WinISD.

Also, and this is important, if you plan on a horizontal CC, DON'T MAKE A THIRD NATP FOR THE CC. Make this, instead.
http://htguide.com/forum/showpost.php4?p=144234&postcount=1
or if mounted in furniture containing the TV...
http://htguide.com/forum/showpost.php4?p=146516&postcount=30

I've short-shrifted my CC's for years, and just built this version. It's not cheap, but it works much better than any option using wider driver spacing and higher crossover freq. Highly recommended; even the wife noticed.

Also, any chance she's got a CRT? If so, wait for the shielded drivers, due in early May per PE. If not, the unshielded ones are a direct replacment to the XO, but require some tweaking of the bass alignment.

Have fun,
Frank
 

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Discussion Starter · #3 ·
I saw that the center channel you recommended is the Modula MTM. I think this speaker is around $400. I want to go with the Natalie P's because parts are around $400 for the pair of speakers, and then I would build the boxes. I need to get my mom a 5.1 surround system for $1000 including the sub which I will also build. I do see the problem with the MTM alignment for the center channel. I saw that there is a crossover made to help this problem with the Natalie P's. The crossover is a 2.5 way instead of the normal 2 way. Should I use a 2.5 way for the front 3 or just stay with the original design. I do understand the problems with the MTM alignment for a center channel, but my Mom has never had surround sound so she will be happy as pie with the Nat P's.

What are you thoughts? Also, thank you for the information on the XO. I didn't realize that box volume had no effect on XO configuration.

Oh, my mom has an LCD so no problems with the non shielded drivers.
 

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Discussion Starter · #5 ·
I can't find the original plans now, but I did find this tonight. http://www.htguide.com/forum/showthread.php4?t=13969 This might be similar to the plans I found before, but I noticed that these plans talk specifically about using a tower version with some very low tuning. It looks like this solves the non linear problems that the RS180 has. The RS180 looks like it can be tuned very low for a 7" woofer. I did notice that the Xmax is very large for this size of woofer. Even though I really wanted to use the peerless nomex woofer because of the great frequency response and low distortion, I am getting excited about building the Nat P.
 

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Discussion Starter · #8 ·
Thank you very much for the tower plans. I saw that I could buy the cabinets from parts express, but since I need to save money and build the towers anyway, I mights as well build all the boxes. The BOM that I had only showed $308.66 for all of the parts for a pair of towers. I better make sure that is somewhat current.
 

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I saw that the center channel you recommended is the Modula MTM. I think this speaker is around $400. I want to go with the Natalie P's because parts are around $400 for the pair of speakers, and then I would build the boxes. I need to get my mom a 5.1 surround system for $1000 including the sub which I will also build. I do see the problem with the MTM alignment for the center channel. I saw that there is a crossover made to help this problem with the Natalie P's. The crossover is a 2.5 way instead of the normal 2 way. Should I use a 2.5 way for the front 3 or just stay with the original design. I do understand the problems with the MTM alignment for a center channel, but my Mom has never had surround sound so she will be happy as pie with the Nat P's....
But only if you have a good CC.

I've been down this exact road - NatP CC --> 2.5-way CC --> Modula CC - so I offer my experieces. The 2.5-way did what was advertised, but didn't sound as good as the base XO to my ears at that time. The 2.5 XO is also twice the cost of the NatP XO. Granted, Modula doubles the price of the speaker...

Much as I love my NatP's, you might better serve your mother's needs with a different design. NatP's are a "bargain" design from a high-end designer; maybe something smaller and simpler would suffice? If you like the RS-series, the Aviatrix uses ND140 drivers with the RS28... and it's a complete design (MTM, MT and CC). Zaph Audio (John Krutke) sells several kits through Madisound that are in your price range. The ZA-series is a complete design...
http://madisound.com/store/index.php?manufacturers_id=186
... and the SR71 is an MT, but one user worked with Krutke to create an SR71 CC.
http://techtalk.parts-express.com/showthread.php?t=222069

Yes, there are consistency issues with RS28-series tweeter sensitivity. They are most common when combining drivers purchased years apart (as I did) and the fix is as simple as adding a parallel resistor across the hotter one. Sensitivity is marked, so you know if you should expect to tweak a little.

I just re-priced things and yes, $400/pair for NatP drivers and XO parts. You see, I want another pair....

Have fun,
Frank
 

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Discussion Starter · #13 ·
fbov, I see what you are saying. It would be better to spend the money once and get it right since the center channel is so important. I am very concerned about some things I have read about the RS28. The inconsistency problem is one thing, but I am really concerned about the fact that the tweeter is completely different design from when most of the crossovers were made. The tweeter use to be a fluid cooled design, but now it is not. i haven't seen any new designed crossovers that were made after this tweeter change. The tweeter change is documented on the Zaph audio website.
 

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Discussion Starter · #14 ·
Does anyone know if the Natalie P's were ever made with the Seas tweeter? This would make me feel better about it since Zaph's audio has kind of made some bad remarks about QC on the RS28.
 

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Design change? Where'd you get that idea; it's not on Zaph's site. Ferrofluid is not a cooling fluid, it modifies the magnetic field, and it's only one of many ways. It seems Usher found the tweet worked better without it, so removal was an upgrade.

There were some quality issues discussed when I built my NatP CC in 2008, but they were resolved before then; there's no lack of new designs since them. Aviatrix are one new and popular design, and then there's these, which were tied for best-of-show on my card at InDIYana 2009. My Continuums have the mis-match tweeters I cited above, and they do not disappoint.
http://www.salksound.com/continuum - home.htm

Have fun,
Frank

PS The Modula series used Dayton RS28a (Aluminum Dome), Seas 27TDFC (Textile dome), or Seas 27TBFC/G (Aluminum Dome) tweeters. NatP uses only RS28A or F.
 

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Discussion Starter · #16 ·
I got the idea because supposedly the new tweeter version (without ferrofluid) is suppose to be a little better, which would mean a change in frequency response a little, and wouldn't that change the crossover a little
 
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