Building large format 2x18 vented enclosures for the 18TBX100 - diyAudio
Go Back   Home > Forums > Loudspeakers > Subwoofers

Please consider donating to help us continue to serve you.

Ads on/off / Custom Title / More PMs / More album space / Advanced printing & mass image saving
Reply
 
Thread Tools Search this Thread
Old 15th July 2013, 08:20 PM   #1
pognoot is offline pognoot  United States
diyAudio Member
 
Join Date: Feb 2013
Default Building large format 2x18 vented enclosures for the 18TBX100

Hi. First time post. I'll try to keep this succinct: my goal is to build (4) large format, professional quality front loaded 2x18 reflex enclosures for live sound reproduction optimized for the B&C 18TBX100. Budget is not a huge concern; I want to do this right the first time around. The subs will be used for a dance band, so they need to play low and hit hard.

I have heard several professional quality front loaded 2x18s like the Clair BT-218, L-Acoustics SB218, Meyer 700HP, and JBL CRS82l. I understand each listening experience was under different conditions using different amplification and processing, but I think it is safe to say these pro level models will outperform your local Guitar Center variety. If possible, I am hoping my design will at least be in the ballpark of the "pros". Wishful thinking? Probably...

I have some basic plans drawn up and long with measurements using BassBox Pro 6. If I present these plans, would someone be willing to take look and make sure I'm headed on the right track? Another set of eyes never hurts before I break out the credit card and the saw.

Last edited by pognoot; 15th July 2013 at 08:32 PM.
  Reply With Quote
Old 15th July 2013, 08:53 PM   #2
diyAudio Member
 
Join Date: Jan 2011
I just saw a little article on the new bassmaxx 2x18 cabinets. 42x42x22.5 I believe....they were almost flat to 20hz, almost. and they said no EQ was used down low to achieve that. Impressive for touring sound, are you looking for something of that nature? If so I say start with a cabinet size similar to that. If you don't NEED that kind of extension, cabinet size can be much smaller.
  Reply With Quote
Old 15th July 2013, 09:09 PM   #3
diyAudio Member
 
Join Date: Feb 2004
Here is a common dual 18" DIY sub from the UK that are comparable to the designs you mention:

Speakerplans.com
G-SUB CUTSHEET - Speakerplans.com Forums - Page 1
Ported Enclosures - Speakerplans.com Forums - Page 1

They are typical dual 18's that roll off around 40 hz.
  Reply With Quote
Old 15th July 2013, 09:13 PM   #4
pognoot is offline pognoot  United States
diyAudio Member
 
Join Date: Feb 2013
I can go big since these subs will be used for outdoor concerts, hotel grand ballrooms, etc. My current design is 52" x 24" x 30"D (about 16.5 cubic ft) tuned to 32hz. I can post the graphs when I can home.

An initial question, with a large volume enclosures, in general, it is better to tune it lower? BassBox recommends 30hz, but tuning it up to say 35hz certainly increases the efficiency / SPL at the knee. Amplifier power won't be an issue. I don't think we will be driving this babies uber hard. Thoughts?
  Reply With Quote
Old 15th July 2013, 09:28 PM   #5
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
not good to drive a BR with signals below box/system tuning

so basicly you would want to either tune below what you need....or use low cut/high pass on your signal/amps...or both

but I have zero experience with this stuff, so...
  Reply With Quote
Old 15th July 2013, 09:49 PM   #6
NEO Dan is offline NEO Dan  United States
diyAudio Member
 
NEO Dan's Avatar
 
Join Date: Jun 2008
Location: N.E. Ohio
In general as you tune lower the excursion peak above tuning will required a driver with more excursion. Bassmaxx are loading high end Faital drivers in that cab I think.
__________________
Regards,
Dan
  Reply With Quote
Old 15th July 2013, 09:53 PM   #7
tinitus is offline tinitus  Europe
diyAudio Moderator R.I.P.
 
Join Date: Nov 2005
hmmm...

and what happens if there is music signal below the tuning frequency ?
  Reply With Quote
Old 15th July 2013, 10:24 PM   #8
OMNIFEX is offline OMNIFEX  Jamaica
diyAudio Member
 
OMNIFEX's Avatar
 
Join Date: Mar 2003
Location: Locked Up In The Amp Rack
Quote:
Originally Posted by pognoot View Post
I can go big since these subs will be used for outdoor concerts, hotel grand ballrooms, etc. My current design is 52" x 24" x 30"D (about 16.5 cubic ft) tuned to 32hz. I can post the graphs when I can home.

An initial question, with a large volume enclosures, in general, it is better to tune it lower? BassBox recommends 30hz, but tuning it up to say 35hz certainly increases the efficiency / SPL at the knee. Amplifier power won't be an issue. I don't think we will be driving this babies uber hard. Thoughts?
Follow the principal of achieving a flat frequency response on what you want. If you want 32 Hz, make sure the design can give you no lower than 32 Hz @ -3 dB. Having a flat frequency response @ 32 Hz would be best but, I don't believe those drivers are capable of giving you that without equalisation involved.

It is interesting you call 16.5 cubic feet a big box. Thirty years ago that would be the standard size for a pro audio bass bin.
__________________
OMNIFEX
  Reply With Quote
Old 15th July 2013, 11:47 PM   #9
diyAudio Member
 
Join Date: Jan 2011
Quote:
Originally Posted by tinitus View Post
hmmm...

and what happens if there is music signal below the tuning frequency ?
The mandatory high pass filter will take care of that. Unless you want the full 20hz and up, then you need to have speakers which will handle that. And amps equally as powerful. Many amps bridged at 4ohms are rated at 1khz, with higher distortion than at lesser loads (higher impedances). Just gotta be aware of all those things.

The bassmaxx boxes I was referring to are the ZV28
http://www.bassmaxx.com/products/sub...ndo-subs/zv28/

Last edited by m R g S r; 15th July 2013 at 11:51 PM.
  Reply With Quote
Old 16th July 2013, 01:37 AM   #10
OscarS is offline OscarS  United States
diyAudio Member
 
Join Date: Jan 2011
Quote:
Originally Posted by pognoot View Post
An initial question, with a large volume enclosures, in general, it is better to tune it lower? BassBox recommends 30hz, but tuning it up to say 35hz certainly increases the efficiency / SPL at the knee. Amplifier power won't be an issue. I don't think we will be driving this babies uber hard. Thoughts?
The answer is two-fold. You should tune it low enough so that you attain the frequency response desired WHILE simultaneously keeping the cone excursion in check with the available amplifier power. Remember, there is an excursion PEAK right above the tuning frequency, since the port is a narrow-Q radiator, it only dampens cone excursion over a very small range. It is this peak that is trouble-some---unless of course you have Xmax to spare, which opens up the possibilities for low-tunings because it is a limiting factor.
  Reply With Quote

Reply


Hide this!Advertise here!
Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not 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 code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
large format midrange driver or... Hrmmf Multi-Way 39 3rd December 2012 12:10 PM
Large Format Concert Arrays thadman Multi-Way 3 17th October 2009 07:46 PM
Economical large format bass-horn broughd Subwoofers 11 8th January 2008 04:18 PM


New To Site? Need Help?

All times are GMT. The time now is 04:54 AM.


vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2014 DragonByte Technologies Ltd.
Copyright 1999-2014 diyAudio

Content Relevant URLs by vBSEO 3.3.2