NatalieP tower port location?

[renton]

Hello all,

I've been lurking here for a couple of weeks trying to get a grasp on things and have decided to try my hand at building the Natalie P in a tower. To keep the overall size small-ish, I don't want to raise the enclosure and put the port on the bottom and from what I have read ( the whole NatP thread a few times ), the second best place for the port is on the rear.

My question is, does it matter where on the rear panel the port goes? Can it be just anywhere along on the back baffle as long as it has clearance? ( 3" I think? )

If it helps, I am basically using the enclosure outlined in the Dr. K's MTM project from PE with measurements, 40"H X 9"W X 12"D, port 3" X 6.5".

Also, I have seen some commercial tower enclosures that are mass loadable, meaning they have an area sealed off in the tower where you can add weight via sand or whatnot. Is this something I should look into for my tower? Is it beneficial?

Sorry if these questions are a bit basic. There is so much more involved in this than I imagined, but I would like to learn and do it properly.

Thank you,

[wkhanna]

I’m going from memory, and not a very good one, but I think you don’t want to put the port directly behind the drivers, and keep it at least ½ the port diameter from any edge if possible.
I typically see ports near the bottom of the cabinet, but don’t know it there is a functional reason for this practice.

I expect others with vastly more knowledge will chime in with more precise info.

And welcome to the forum! And good luck with your build!
As one who has already made a Nat P tower, you have chosen wisely, Grasshopper!

[renton]

@wkhanna

Thanks for the quick, informative reply and welcome. Placing it towards the bottom sounds good.

It is great to see everyone one's experiences and feedback on their projects. I will be sure to post my trials as they progress. :T

[Sefferdog]

Mine is centered about 6 inches up from the bottom of the cabinet. Hope this helps.

[renton]

@Sefferdog

Thanks. That seems like a good spot and if there are no objections, I am going with it.

[renton]

What about the mass loading? Does anyone have experience with that?

[Dennis H]

What about the mass loading? Does anyone have experience with that?

Probably not worth it for a couple of light 7". The box will be plenty heavy.

[renton]

@Dennis H

Great thanks. This will help me simplify things a bit.

[Whrswoldo]

Hello all,

I've been lurking here for a couple of weeks trying to get a grasp on things and have decided to try my hand at building the Natalie P in a tower. To keep the overall size small-ish, I don't want to raise the enclosure and put the port on the bottom and from what I have read ( the whole NatP thread a few times ), the second best place for the port is on the rear.

My question is, does it matter where on the rear panel the port goes? Can it be just anywhere along on the back baffle as long as it has clearance? ( 3" I think? )

If it helps, I am basically using the enclosure outlined in the Dr. K's MTM project from PE with measurements, 40"H X 9"W X 12"D, port 3" X 6.5".

Also, I have seen some commercial tower enclosures that are mass loadable, meaning they have an area sealed off in the tower where you can add weight via sand or whatnot. Is this something I should look into for my tower? Is it beneficial?

Sorry if these questions are a bit basic. There is so much more involved in this than I imagined, but I would like to learn and do it properly.

Thank you,

I am in the process of building some similar speakers, and I have already used up a 4X8 sheet of 3/4" birch plywood and had to go back to buy more; I don't think you will have a problem with a lack of mass. Also, what tuning are you going for with that port length?

[renton]

heh - yeah the more I look into the design of these, the more I realize that they are probably going to be fairly heavy. I worked at Home Depot back in the day loading lumber, etc . . .and MDF is not light. . . at all


I downloaded WinISD and am still playing around with enclosure volume, port length and tuning.

The original specs I posted were from the Dr. K's MTM project from the Parts Express Showcase.

From the above project write up they recommend for the "extended bass" version:
40"H x 9"W x 12"D
3" x 6.5" port giving a tuning of 35Hz
Volume 1.7 cf / 48.1L

Looking at the gain chart for the above specs, it seems to start rolling off fairly early though. I have the room and may shoot for something a bit larger in the 60L range.

I am in the process of building some similar speakers, and I have already used up a 4X8 sheet of 3/4" birch plywood and had to go back to buy more; I don't think you will have a problem with a lack of mass. Also, what tuning are you going for with that port length?

[renton]

Question about the fundamentals of tuning the box.

I may be misunderstanding this so please correct me if I am wrong but, ultimately wouldn't you want the gain chart to be as level as possible through the entire frequency range and then roll off sharply at the low end of what the speaker can produce? In the case of the RS180, 40Hz ?

[Sefferdog]

Question about the fundamentals of tuning the box.

I may be misunderstanding this so please correct me if I am wrong but, ultimately wouldn't you want the gain chart to be as level as possible through the entire frequency range and then roll off sharply at the low end of what the speaker can produce? In the case of the RS180, 40Hz ?

renton, a gradual roll off will keep the bass from sounding boomy when room gain is factored in.

I built them in a box 60 liters tuned to 32hz and they sound unbelievable. Here is a post from Jon Marsh regarding this as well:

http://www.htguide.com/forum/showpost.php4?p=301943&postcount=417

Hope this helps.

[renton]

Thanks Sefferdog. That makes sense. Going to go with the 60L and 32hz tune. No use trying to muck with a design that is already considered to be excellent by those who know far more than I. :T

renton, a gradual roll off will keep the bass from sounding boomy when room gain is factored in.

I built them in a box 60 liters tuned to 32hz and they sound unbelievable. Here is a post from Jon Marsh regarding this as well:

http://www.htguide.com/forum/showpost.php4?p=301943&postcount=417

Hope this helps.