Accidental MLTL Technique - Page 2 - 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 13th March 2013, 09:59 PM   #11
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
If it is a room effect, does it change depending on where you sit in the room to listen to it? Doing a measurement will tell a lot. That's interesting that a bass line from a favorite song is what tipped you off. If it is everywhere in the room then the measurement will reveal a big dip in the bass. One other thing, have you checked for air leaks around your driver gaskets or lack of wood glue to seal your cabinets? A small hairline air gap due to bad glue seal can mess with the low bass notes. Is it the low low 41 Hz note?
  Reply With Quote
Old 13th March 2013, 11:43 PM   #12
diyAudio Member
 
tuxedocivic's Avatar
 
Join Date: Jan 2011
Location: Ladysmith, BC
I once made an accidental TL. At least I think I did. Built a really tall MTM and put the port near the bottom. Just did. Had a ton of bass. But wasn't very good. Considering I screwed up, it's not a surprise. I've learned since then. I usually just stick to sealed boxes now. If I wasn't a subwoofer user I'd want to learn more about TLs.
  Reply With Quote
Old 14th March 2013, 01:08 AM   #13
diyAudio Member
 
LineSource's Avatar
 
Join Date: Sep 2003
Location: SiliconValley
You will find these programs useful if you are interested in experimenting with MLTL alignments using just free software.

Transmission Line Alignment Tables Spreadsheet by Keith Web on
Transmission Line Theory

Hornresp Plots MLTL SPL response without stuffing effects.

Akabak .. does it all pretty well. Hornresp design data can be exported to Akabak.

ROUGH:
1) use Keith Webb's Excel spread to enter your speakers T/S parameters and use a SL/SO taper=1 to get the Tline cross section area. This area can be entered into Hornresp for a good quality MLTL simulation
2) use Keith Webb's Excel spread to enter your speakers T/S parameters and use a SL/SO taper= 0.05 to 0.1 to mimic the bottom MLTL port area to get the MLTL total height. This height can be entered into Hornresp for a good quality MLTL simulation. These good estimated help you tune a Hornresp design.
3) After studying MLK's MLTL website information you can decide on where to position the speaker and port. The diameter of the speaker also affects the offset distance. You do not want to put a 16" Altec 604 very close to the top. Locating the speaker center in the TL length 0.20x to 0.33x from the top is a good start. A 0.33x spacing removes many harmonics.
4) You can export the Hornresp design data into Akabak and fine tune the port position and the stuffing.
5) DO NOT FORGET ROOM EFFECTs. Many MLTL's depend upon rear wall or corner effects to get the best in-room performance.
Download the free
Baffle Edge Diffraction Simulator Ver 1.2 by Jeff Bagby
"Diffraction & Boundary Simulator 1.20"
6) There are genius designers that blend quarter wave TL tuning with clever BR stuffing and port design.
Attached Images
File Type: jpg MLTL Altec604.jpg (114.3 KB, 813 views)
File Type: jpg Hiraga Altec 604E.jpg (80.3 KB, 802 views)
  Reply With Quote
Old 14th March 2013, 01:24 AM   #14
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Line Source,
Yes, I am aware of these resources and I also use Akabak. The point of my thread is that it doesn't matter, all you need to do is design for a bass reflex alignment tuned lower than you normally would (no more than 75% of fs) and build the bass reflex box in a long aspect ratio between 30 to 45 inches depending on fs. Set your length and baffle width and the volume gives the depth and the bass reflex program also gives the vent dimensions. Magically, maybe luck, it ends up close to what MJK optimization might produce.
  Reply With Quote
Old 14th March 2013, 01:43 AM   #15
diyAudio Member
 
Join Date: Nov 2012
Location: Western Massachusetts
Quote:
Originally Posted by cogitech View Post
I was getting along great with them, then last night I played "With or Without You by U2. The bass-line in that song is one that is ingrained in my head, and I have heard it played correctly so many times I would be embarrassed to say.

Within the first four notes on the Pensils, I knew something was very, very wrong. I eventually realized the cabinets (or their interaction with my room) have a huge, deep null somewhere down low. 2 notes out of the 4-note bass-line were down 15dB or more from the other notes. It was almost like Adam just wasn't playing the notes.

I messed with the EQ and had to get very aggressive with it and even then the bass-line was a mess.

Tuxedo will find it hard to believe, but my accidental nanoTowers can do bass more consistently than my Pensils.
I have always enjoyed 'mysterious ways' by U2 as a bass test song. With that song my fathers Bose 301s sound pretty nasty. The tuning of the cabinet seems to not have a dead spot so much but a live spot where that note is deafeningly loud compared to everything else. It's probably just an inherent problem with resonant systems- with my WiBAQ you have go turn up the volume pretty high to 'activate' the cabinet and get the air moving to get some real bass.
  Reply With Quote
Old 14th March 2013, 02:51 AM   #16
diyAudio Member
 
cogitech's Avatar
 
Join Date: Jan 2011
Location: Kamloops, BC
Quote:
Originally Posted by xrk971 View Post
If it is a room effect, does it change depending on where you sit in the room to listen to it? Doing a measurement will tell a lot. That's interesting that a bass line from a favorite song is what tipped you off. If it is everywhere in the room then the measurement will reveal a big dip in the bass. One other thing, have you checked for air leaks around your driver gaskets or lack of wood glue to seal your cabinets? A small hairline air gap due to bad glue seal can mess with the low bass notes. Is it the low low 41 Hz note?
It is the lowest of the 4 notes in that bass line, and much of the second-lowest note as well. On the other hand, the two higher notes are very BOOMY.

Listen to the song again if you have it and imagine that the first 8 notes are solid and BOOMY, then the second 8 notes nearly disappear, then back to BOOMY, then disappear to a lesser extent.

It is annoying as sh!t, and my other two pairs of speakers don't do it. Each note has the same volume.
  Reply With Quote
Old 14th March 2013, 04:32 AM   #17
diyAudio Member
 
cogitech's Avatar
 
Join Date: Jan 2011
Location: Kamloops, BC
Got the issue mostly solved.

Alpair 10.2 "Castle" ?
  Reply With Quote
Old 14th March 2013, 06:10 AM   #18
xrk971 is offline xrk971  United States
diyAudio Member
 
xrk971's Avatar
 
Join Date: Oct 2012
Location: Virginia
Glad you fixed it. I did not realize you stuffed all the way either. I learned from TABAQ that bottom third is empty and that has just stuck with me. Sometimes I remove up to 1/2 along length for extra bass.
  Reply With Quote
Old 14th March 2013, 06:12 PM   #19
diyAudio Member
 
Join Date: Aug 2009
Location: North Texas, USA
You guys sound like you expected a MLTL to have significantly different response than a vented box of the same volume. The MLTL will have extended low end, but not by 10 or 20Hz as you all seem to have expected. It will be be a few hz.
Using a vented box model and having it be close to an MLTL shouldn't be a revelation.

Having "lots of bass" out of a tall ported box shouldn't be a surprise if your normal build is a sealed box.
__________________
I was so much older then, I'm younger than that now.
  Reply With Quote
Old 14th March 2013, 07:15 PM   #20
Gost22 is offline Gost22  Bolivia
Banned
 
Join Date: Sep 2012
Location: San Ignatio de Velasco
Hi sir Xrk971!
Which speaker combination (box) you propose for the LM3886 audio amplifier!?
Offer your solution a lot because I appreciate your work!
thank you and cheers!
  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
Tell us about your accidental discoveries sprinter Music 32 21st October 2013 07:22 AM
Accidental Death of a DoZ... aspringv Solid State 13 22nd July 2012 10:38 AM
Accidental DIY Audio Waterdog Introductions 9 23rd January 2012 07:31 PM
RB250 Rewiring - accidental mess up? InfiniteGain Analogue Source 5 30th January 2009 11:11 PM


New To Site? Need Help?

All times are GMT. The time now is 12:00 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