Monkey see, monkey do... two RL-P18s for me too! - Page 3 - Home Theater Forum and Systems - HomeTheaterShack.com

Reply
 
Thread Tools
post #21 of 151 Old 10-07-07, 10:59 AM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

You mean wrap the port with whatever I line the box with? Seems like people are using fibreglass mostly, or in some cases foam sheets. Would something visco-elastic like Dynamat work well?

Last edited by Bradley; 10-07-07 at 11:05 AM.
Bradley is offline  
Sponsored Links
Advertisement
 
post #22 of 151 Old 10-07-07, 01:37 PM
Elite Shackster
 
SteveCallas's Avatar
Steve
 
Join Date: Apr 2006
Posts: 2,398
Re: Monkey see, monkey do... two RL-P18s for me too!

When you determine your final enclosure volume, you will need to re-simulate the design, as 8.25" diameter ports will need to be longer than 8" ports for the same tune.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
SteveCallas is offline  
post #23 of 151 Old 10-07-07, 05:42 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Right-o. I've already considered that. Looks like they are closer to 8.375 inches I.D., although it is a little tricky to measure because the tubes are not perfectly round. I may take these Sakrete tubes back and hunt for some genuine Sonotube.

Part of my plan to determine net volume is to weigh each piece of internal bracing and calculate the volume based on its known (measured & verified) density. Unfortunately, I think the bracing is going to eat up a lot of volume, which would require a longer port length at the same tune. Only so much I can do about it right now as I'm already committed to the external dimensions of 26H x 30D x 49W. Net volume may be as low as 17 ft^3 and port length may wind up being around 35" for a 14.5 Hz tune.

Off to assemble the table saw...

Bradley

Last edited by Bradley; 10-08-07 at 01:21 PM. Reason: Typo.
Bradley is offline  
 
post #24 of 151 Old 10-09-07, 03:24 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Been mucking around with Google Sketchup. Confusing at first, but slowly getting the hang of it. A concern I have now is how close the 8" port tube is to the rear wall and also to the driver. There is just no way to keep it one port diameter away from those other surfaces. Is this anything I should even concern myself with? At the end of the port inside the cabinet there is more than one port diameter "in front" of the port.




Last edited by Bradley; 10-09-07 at 09:36 PM.
Bradley is offline  
post #25 of 151 Old 10-09-07, 03:51 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Also, I had a scare last night about the net/working volume. I thought I had horribly underestimated the volume that the bracing will take up. I knew it would be more than what Collo's Boxnotes program estimates but wasn't sure how much more. Finally, I decided to write a VB script to calculate the net box volume, with reasonable approximations for the number and style of braces being. For the sake of this estimation, the style of brace is simply a rectangular panel that matches the internal dimensions of the box with a LARGE circle taken out of it.

If anyone is interested in having a look at the script, you can see it here.
Bradley is offline  
post #26 of 151 Old 10-09-07, 05:43 PM
Senior Shackster
 
Mongrel714's Avatar
Mongrel
 
Join Date: May 2007
Location: Melbourne,Florida
Posts: 242
Re: Monkey see, monkey do... two RL-P18s for me too!

Quote:
Bradley wrote: View Post
You mean wrap the port with whatever I line the box with? Seems like people are using fibreglass mostly, or in some cases foam sheets. Would something visco-elastic like Dynamat work well?
I'm not to sure about the dynamat, that is mostly for deadning troublesome vibrating panels, you need something like fiberglass, I used some 1" thick "batting" I picked up at an upholstery shop, better than fiberglass and no itching.


To view links or images in signatures your post count must be 10 or greater. You currently have 0 signatures.
Mongrel714 is offline  
post #27 of 151 Old 10-09-07, 09:35 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Yeah, I didn't think so. I was just wondering since I have a bunch of dynamat-like material somewhere in my garage, new in the box.
Bradley is offline  
post #28 of 151 Old 10-10-07, 02:37 AM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Totally out of control over here! Not done and not really happy with the braces. But here's what I've got "sketched up" so far:



Again, this is just a rough draft and work in progress. However, if I'm lucky the port will terminate in that third brace. Both ends are going to get the mondo 1.5" radius flare.
Bradley is offline  
post #29 of 151 Old 10-10-07, 06:44 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Here's the latest draft.



I think the only thing left to do is add some donut support rings for the port tube. I'm not going to bother trying to model the flares or rounded edges.

The smaller holes, or "swiss cheese", aren't really necessary. I'm just a little worried about coming in at 17.0 cubic feet (or higher) as planned. I'll need to add up the volume of all the bracing and port tube once the "ink" has dried on the design.
Bradley is offline  
post #30 of 151 Old 10-11-07, 02:15 PM Thread Starter
Senior Shackster
Bradley
 
Join Date: Aug 2007
Location: Seattleland
Posts: 146
Re: Monkey see, monkey do... two RL-P18s for me too!

Came up shy on the net volume inside the box, so I've had to make revisions. The side-to-side braces in the middle (just behind the driver) were retarded anyway, so I got rid of them.



By the way, I ditched the VB script in favor of an Excel spreadsheet to calcuate the volume using surface area measures taken from the Google Sketchup drawing. All the files I'm using are on my web server if anyone wants to check them out, including the Sketchup drawing.

http://s16v.com/subwoofer

Bradley
Bradley is offline  
Reply

Bookmarks

Tags
monkey , rlp18s

Quick Reply
Message:
Options

Register Now




PLEASE COMPLETE ALL REQUIRED FIELDS BELOW... THANKS!

REQUIRED FIELDS ON THIS PAGE
YOU MUST COMPLETE ALL OF THESE

Username
Password
Confirm Password
Email Address
Confirm Email Address
Random Question
Random Question #2




User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.

Password:


Confirm Password:
Email Address
PLEASE READ BELOW PRIOR TO ENTERING AN EMAIL ADDRESS!

ATTENTION!

YOU MUST ACTIVATE YOUR ACCOUNT!

Activation requires you reply to an email we will send you after you register... if you do not reply to this email, you will not be able to view certain areas of the forum or certain images... nor will you be able download software.

AN INVALID EMAIL ADDRESS WILL CAUSE YOUR ACCOUNT TO BE DELETED!

See our banned email list here: Banned Email List

We DO NOT respond to spamcop, boxtrapper and spamblocker emails... please add @hometheatershack DOT com to your whitelist prior to registering or you will get nowhere on your registration.


Email Address:
OR

Log-in










Thread Tools
Show Printable Version Show Printable Version
Email this Page Email this Page



Posting Rules  
You may post new threads
You may post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML is not allowed!
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

 


For the best viewing experience please update your browser to Google Chrome