The Flute Pipe TL - diyAudio
Go Back   Home > Forums > Loudspeakers > Full Range

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 9th June 2013, 08:54 PM   #1
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Default The Flute Pipe TL

I was looking at ways to model in AkAbak, a Karlson-like slot to reduce resonance peaks and dips by strategically placed Q-spoiler holes. IG81 suggested placing them at the 7/4-mode and 9/4-mode anti-nodes as described in this post:

KARLSON

I modeled a 224 cm long TL with 3.5 in x 2.5 in CSA, driven at the end witha Fostex FF85WK. The TL starts at the top, goes down and has single fold at the halfway point so that the terminus exits straight up.

The holes were placed at the following locations:

7/4-mode: 32 cm, 96 cm, 160 cm
9/4-mode: 24.9 cm, 74.7 cm, 124.5 cm, and 174.2 cm

The hole diameters were determined by trial and error while trying to flatten the freq response (increase hole dia) while keeping bass extension low as possible (keep holes small as possible). I am sure better optimizations can be done - this was done rather quickly and manually.

The hole diameters ended up as:

7/4-mode: 0.25 in, 0.35 in, 0.60 in
9/4-mode: 0.0625 in, 0.40 in, 0.50 in, 0.50 in

The following plots show the base TL case with no holes, all 7/4-wave holes open, all 7/4-wave and 9/4-wave holes open.

As you can see, as expected, the addition of the holes drastically reduces the bass extension which was 37 Hz and ended up at about 77 Hz. However, the amplitude of the bass increased dramatically and the flatness of the bass frequency response was significantly improved. There are still some dips and peaks but I think with a little stuffing, this TL may actually work quite well. The FF85WK really is not a driver meant to operate anywhere near 37 Hz and 77 Hz is closer to its ideal limit I think and it shows.

Also included are the cone excursion and impedance for the case with all holes open.

The resulting TL, if it were built would resemble a large flute-like pipe with oddly sized holes.

Last edited by xrk971; 9th June 2013 at 09:00 PM.
  Reply With Quote
Old 10th June 2013, 01:07 AM   #2
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
Interesting how it smoothed out the lower bass response, this was somewhat expected though. ~70Hz is about as low as the FF85WK plays decently in the little BLH I have them in. It was similar in the 224cm foamcore pipe. Power handling is probably not too high there though.

The peaking above ~200Hz might still be prominent as it was in my physical build, but stuffing might kill it just good.

IG
  Reply With Quote
Old 10th June 2013, 02:24 AM   #3
freddi is offline freddi  United States
diyAudio Member
 
freddi's Avatar
 
Join Date: Aug 2005
interesting - thanks for the work - would it somewhat resemble Sapkowski's patent? (which like the later Bose patent gives no credit to Karlson)

Click the image to open in full size.
  Reply With Quote
Old 10th June 2013, 02:39 AM   #4
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Freddi,
Similar but mine has distinct holes based on modes rather than holes to look like a K slot. Patents will only reference prior art that they feel is different but if the same they won't reference it as it means they have nothing novel. So or is not surprising when someone takes credit they fail to reference Karlson's work.
  Reply With Quote
Old 10th June 2013, 03:11 AM   #5
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
I remembered having seen that holey K-slot but forgot which one that was, thanks Freddi.

IG
  Reply With Quote
Old 10th June 2013, 03:22 AM   #6
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
IG,
Are you going to try cutting holes in your FC F-83 TL? Or build a new one?
  Reply With Quote
Old 10th June 2013, 03:26 AM   #7
freddi is offline freddi  United States
diyAudio Member
 
freddi's Avatar
 
Join Date: Aug 2005
Karlson in his original Acoustic Transducers and Fulmer both talk about use of holes. It could be just a few of varying size but don't think there was mention of spacing. A test enclosure with a removable panel for the holes would be interesting. I don't have any drivers under 8" which are worthwhile.
  Reply With Quote
Old 10th June 2013, 12:25 PM   #8
IG81 is offline IG81  Canada
diyAudio Member
 
IG81's Avatar
 
Join Date: Feb 2008
Quote:
Originally Posted by xrk971 View Post
IG,
Are you going to try cutting holes in your FC F-83 TL? Or build a new one?
I didn't keep the FC pipe for very long, just measured and listened a bit. It had enough promise that building a wood version could be fun and I may yet do it, really can't say when though.

IG
  Reply With Quote
Old 10th June 2013, 01:54 PM   #9
diyAudio Member
 
Join Date: Jan 2012
Goes to show how good mass loading is.

Related question to the 'holes', and perhaps onken style enclosure etc. So given the same apparent terminus area, the higher the aspect ratio of the vent and/or the number of high aspects vents totalling the same terminus area, generally the 'better' the results ?

I use better very ambiguously here, but generally it does good things no?
  Reply With Quote
Old 10th June 2013, 02:06 PM   #10
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Well, its acoustical loading becomes more resistive, so is better if the cab is acoustically too small and/or the driver has a high Qts and/or is driven with a high output impedance.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  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
TL for silver flute 6.5"? Dave R Multi-Way 26 26th April 2013 09:45 PM
TL, Ported or other box type ? for Silver Flute W20RC3808 nickthevoice Multi-Way 0 14th December 2007 04:32 AM
Here's an interesting TL pipe question ??? Fish Chris Subwoofers 16 1st February 2007 08:10 PM
4 ohm TL = narrow pipe? bwbass Multi-Way 9 19th October 2004 04:27 PM
Oblong pipe for TL? Dave Jones Multi-Way 11 12th August 2003 10:38 PM


New To Site? Need Help?

All times are GMT. The time now is 12:02 PM.


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