Nat P research

[ruseriousclark]

At the risk of sounding like the newbie I am...I've run into some design issues that need some expert insight.

I've seen and researched multiple different Nat-P designs from bookshelf to towers, ported and sealed.

I'm ridding myself of my commercial Infinity's for a home theatre comprised of DIY in a year long project beginning in March. So to get to the point here are my questions...

1. What is involved within the crossover from the bookshelf design to the tower design. Is there a TL version and if so is it similar to the Seas/Thor version? That's not important to me, just curious.

2. Are there design issues with a horizontal arrangemnt with Nat-P and would a seperate mid need to be added to accomodate dialoge as is typical with most Center channel designs. Again what crossover issues are underlying?

3. Ohm ratings and Power. Never heard anyone state the specs on the design for these and if there is an optimal configuration of impedance and power. I'm running SS amp 150 at 8 and 250 at 4. I'd love to keep it at the 4 range but I'm sure this is up to the builder and which drivers and crossover components are selected.

4. Last question. As I understand an optimal enclosuer is one that is very dead from an accoustic point. Is this why solid wood enclosures and never discussed or is this a cost prohibitive issue. I happen to have an abundance of very good supplies available and want to know if there is a reason I should not use real solid building material.

Thanks in advance and please don't slap me around for asking such elementary questions.

I've sweat over this decison for over a year now and I'm all in. No turning back now. So all the advice you can offer is greatly appreciated.

I have one remaining question but I'll reserve it until I see what kind of response this generates.

DA

Go CATS!

[BobEllis]

At the risk of sounding like the newbie I am...I've run into some design issues that need some expert insight.

I've seen and researched multiple different Nat-P designs from bookshelf to towers, ported and sealed.

I'm ridding myself of my commercial Infinity's for a home theatre comprised of DIY in a year long project beginning in March. So to get to the point here are my questions...

1. What is involved within the crossover from the bookshelf design to the tower design. Is there a TL version and if so is it similar to the Seas/Thor version? That's not important to me, just curious.

I built a MLTL type for a friend. Internal dimensions 44"h x 7.5"w x 14" deep, rear firing 3" ID x 6" port, IIRC. Subjectively bass extension into the low 30s or upper 20s. The catch is that we are still talking about a pair of 7" drivers. You cannot get very loud without distortion. It's fine for normal listening, but don't plan on reference level movies. My friend chose this route to save a separate stand and get some deep bass until we build his sub.

Since it sounds like you'll be using a sub anyway, just go sealed and let the sub(s) do their job.

2. Are there design issues with a horizontal arrangement with Nat-P and would a separate mid need to be added to accommodate dialogue as is typical with most Center channel designs. Again what crossover issues are underlying?

Yes - unless you can live with a small sweet spot, wait for the upcoming small format center or go for the RS WT/MW center in the missions accomplished section. The latter will leave you wanting to go for their counterpart L/R towers if your budget can handle it.

3. Ohm ratings and Power. Never heard anyone state the specs on the design for these and if there is an optimal configuration of impedance and power. I'm running SS amp 150 at 8 and 250 at 4. I'd love to keep it at the
4 range but I'm sure this is up to the builder and which drivers and crossover components are selected.

Nominal impedance if these were commercial speakers would be 4 ohms, but it dips close to 3 at the lowest. As a newbie, stick with the established design. You cannot just swap in different drivers without redesigning the crossover. You amp should be fine. Be sure it has plenty of ventilation since 4 ohm loads generally cause amps to run hotter than 8.

4. Last question. As I understand an optimal enclosure is one that is very dead from an acoustic point. Is this why solid wood enclosures and never discussed or is this a cost prohibitive issue. I happen to have an abundance of very good supplies available and want to know if there is a reason I should not use real solid building material.

Wood expands and contracts with humidity changes. While it can be done, it is difficult to maintain an airtight box with solid wood. It also is less dense than MDF, making it less attractive when looking for a dead enclosure. Bracing solid wood makes allowing for movement more difficult.

Some use Baltic Birch void free ply for enclosures with good results. I prefer MDF, in large part due to cost. I don't care for the raw ply edge, so I'll veneer or paint anyway.

Enjoy your project, The NatP is a great sounding speaker, especially when considering the price.

[EdL]

Bob is right about the level of playback with a cabinet that extends the low bass response. I've also modelled the drivers. I think we got similar results. X-max is exceeded for anything over 25 watts input. That should get you into the ~105 dB range. Note the scale. This is for a 1W input.

Image not available


Which Cats will show up against Vandy? I live in Berea. I'd be happy to further discuss this with you if you like.

[Brian Bunge]

The crossover is not impacted by building either a ported or sealed cabinet. So that won't have to change. Build whichever you prefer.

[BobEllis]

I suggested sealed for use with a sub since it fits most receivers and pre/pros built in subwoofer XOs better. Brian is correct as to sealed/ported having no impact on the NatP internal crossover.

Note that room gain will likely completely counteract the droop in low end response shown on Brian's graph. Real rooms will show something less than the predicted 12 db/octave gain below the frequency determined by the room dimensions.

IMHO, room gain is one of the reasons some people say that ported boxes sound boomy. If your anechoic response is flat to say 35Hz. room gain will actually cause a hump in bottom end response.

[wkhanna]

You have already gotten good advise from some really good people, here. I will add my $.02, since I am nearing the end of my Nat P Project.

1. What is involved within the crossover from the bookshelf design to the tower design.

No difference, port length is adjusted for the size of the enclosure. Larger boxes normally can achieve a lower tuning due their increased volume.

Is there a TL version and if so is it similar to the Seas/Thor version? That's not important to me, just curious.

Don't worry about variations, use the design that is in the first post of the Nat P thread, the XO was designed specifically for the components listed. These XO's were designed to exceed just about anything you could find in the commercial market, and as such should be treated with the respect they deserve. Don't scrimp on XO components. By the time you finish your speakers, $50 more spent on components is minimal, compared the sweat equity and time you have already spent, IMHO.

2. Are there design issues with a horizontal arrangement with Nat-P and would a separate mid need to be added to accommodate dialog as is typical with most Center channel designs. Again what crossover issues are underlying?

Wait, be patient, a new design is on the way, soon.

3. Ohm ratings and Power. Never heard anyone state the specs on the design for these and if there is an optimal configuration of impedance and power. I'm running SS amp 150 at 8 and 250 at 4. I'd love to keep it at the 4 range but I'm sure this is up to the builder and which drivers and crossover components are selected.

Assume 4 ohm.

4. Last question. As I understand an optimal enclosure is one that is very dead from an acoustic point. Is this why solid wood enclosures and never discussed or is this a cost prohibitive issue. I happen to have an abundance of very good supplies available and want to know if there is a reason I should not use real solid building material.

I used Baltic Birch ply, I like natural wood too, but ply offers rigidity and density and acoustically performs better than solid wood. MDF is very good, but veneering is required to get a wood finish. If you must have a wood finish, consider birch, but remember, you have deal with end grain unless you miter your joints. Unless you’re experienced with this technique, I would recommend taking a less complicated route for your first pair of speakers.

Thanks in advance and please don't slap me around for asking such elementary questions.

Your welcome, and keep the questions coming, and read, read and read some more. the Modula thread is the same as the Nat P, the only difference being the XO design is a bit more sophisticated and expensive, and will deliver a bit more SQ on higher-end systems. And the threads on the designs offer some tips that can be applied to any project.

[ruseriousclark]

Thanks to all! Very much what I was hoping to hear. This is my third set of DIY but the first that was not a pre fab kit.

Wkhanna- your last statement has more truth to it than I ever thought possible. My wife's been on my case for the past 4 months since I have had a tendancy to us my evenings reading up on design preferrences and the such like.

This is developing into an obsession!

I'm in no hurry for the center version. I think I have plenty to keep me busy until a design is worked out. But thank you for the insight I'll be anxiously waiting to see how the test results compare to that mentioned earlier by BobEllis. Although I would like to avoid a 100 lbs center! Jeez. Weighs as much as one of my subs.

Really appreciate the feed back. You guys have really helped me sort through what can be a very saturated topic. I've found in as much as many DIY'ers are right on with the $/quality perspective of DIY, there are still some very expensive DIY routes that from the data provided just don't seem to offer the the bang for the buck of what I've found here. Not to mention the organization on this site is far better than most and much easier to sort through.

May have some more questions later on and my brother and I are considering a 2 channel 3 way design for him. Think I saw someone with an avatar with a beatiful cherry MTMWW using HiVi WW. Haven't seen plans for it but I'll cross that bridge when we get to it.

Well here I go a building...thanks again.

DA

Go CATS!

[ruseriousclark]

Ed,

Great to hear there is someone else who shares both of my passions in life.

I'll have my fingures crossed on Sunday.

I may have to take you up on that offer. I've not found to many near lexington with any DIY experience. Most just buy retail. At least I got my stuff on sale.


DA

Go CATS!

[TNRRClassic]

Ed,

Great to hear there is someone else who shares both of my passions in life.

I'll have my fingures crossed on Sunday.

I may have to take you up on that offer. I've not found to many near lexington with any DIY experience. Most just buy retail. At least I got my stuff on sale.


DA

Go CATS!

Well, there are other UK fans out here, myself included. It is halftime right now, and they are nine points up. Will this be the typical game with them squandering a lead and going back and forth until they lose in the last thirty seconds?

I hope all your projects turn out better than their season.

Matt

[MuaDibb]

Hey guys, I'm right outside of Lexington myself. I'm getting ready to build Nat P's also, I have the speakers and am working on the crossovers right now. Yes, the cats did just that, and I am a sad, sad Panda.
If anyone wants to compare notes or get together for a listen when they're done drop me a line.

[TNRRClassic]

I missed the end of the game, but I had a pretty good idea of the outcome three minutes into the second half. Actually, I live about four hours from Lexington in Tennessee, but I went to school there and lived there for some time. I am nearly ready to start assembly of my Modula MTM project. I just couldn't forgive myself if I did the NatP and thought I was missing something. It is good to see that there are some folks from the Bluegrass state on the board.

[BobEllis]

Although I would like to avoid a 100 lbs center! Jeez. Weighs as much as one of my subs.

Sounds like we've identified your next project. Bigger subs.