Go Back   Home > Forums > >
Home Forums Rules Articles diyAudio Store Blogs Gallery Wiki Register Donations FAQ Calendar Search Today's Posts Mark Forums Read

Multi-Way Conventional loudspeakers with crossovers

Help needed with TL calculation
Help needed with TL calculation
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 19th November 2017, 07:40 PM   #1
Ingborgbo is offline Ingborgbo  Sweden
diyAudio Member
 
Join Date: Aug 2017
Default Help needed with TL calculation

Hello!

I would like to build myself a pair of TL speakers! That seemed pretty easy at first, I read how people thought designing them wasn't very complicated. Speed of sound, herz, cone area and easy as pie.
Well. No.
The more I read, the less I understand! So here I am now asking for help with designing those magic unicorn speakers.

I'll try to give as much info as possible about the room conditions and so on.

The room is 4 x 5 meters (some 13 x 16 feet) with 2,2ish meters (7 feet) floor to cieling. The speakers will have to be placed about 3m (10 feet) from eachother, and listening distance will be about 3,5m. The wall the speakers face is a "log-wall" with the actual logs of the wall visible, so it's very uneven. The only furniture along that wall is the couch I'll be sitting on when listening.

I have 3-way speakers in mind, using Monacor elements. A 12" SPH-300KE as woofer, 6,5" SPH-165KEP as midrange and 1" DT-350NF as tweeter.

Woofer specs

Impedence (Z) 8ohm
Resonant frequency (fs) 22Hz
Max frequency range f3-2200Hz
Music power 200W max
Power rating (P) 120W rms
SPL (1W/1m) 90dB
Suspension compl. (Cms) 0,81mm/N
Moving mass (Mms) 65g
Mech. Q factor (Qms) 4.15
Electr. Q factor (Qes) 0.36
Total Q factor (Qts) 0.33
Equivalent volume (Vas) 250l
DC resistance (Re) 6,2ohm
Force factor (BxL) 12,5Tm
Voice coil induct. (Le) 1,5mH
Voice coil diameter 65,5mm
Voice coil former Glass fibre
Linear excursion (Xmax) +-6,5mm
Eff. cone area (Sd) 496cm2
Magnet weight 1,2kg+79g
Weight 5,4kg

I have KMTech 24dB/oct active filters allowing me to set the crossovers as I please. Active speakers powered by LM3886, one each for mids and tweeters, two each for woofers. Fed by XLR from a JC-80 clone.
From an esthetical view I like tall, not very wide but deep enclosures.

I'm not sure how much of this is actually relevant, but what I do know is that I'm fed up with banging my head against the wall trying to figure out how to design the speakers by myself. Hopefully you guys got a moment to help me out.

Regards, Andreas
  Reply With Quote
Old 19th November 2017, 11:18 PM   #2
Dissi is offline Dissi  Switzerland
diyAudio Member
 
Join Date: Sep 2012
Location: Winterthur
Hi Andreas,

TL design is not that easy and I'm not an expert. But let's start simple, with a conventional vented loudspeaker design. Attached is an overview of possible alignments for the Monacor SPH-300 KE. The volume Vb ranges from 80 to 300 liters, but if we ignore the exotic cases, we normally choose 110-150 liters and get a cutoff frequency F3 of around 30 Hz.

That's already quite a large box and 30 Hz is probably more than enough.

A TL design usually is chosen in order to extend the range towards lower frequencies. Even though the list shows vented alignments, it is also a rough estimate of what can be expected from a transmission line. A volume of 220-300 liters and an F3 down to 20 Hz.

So the first question is, do you really need such a low corner frequency and are you willing to build such a large box?
Attached Images
File Type: jpg EnclosureRecommendationsMonacorSPH-300KE.jpg (175.8 KB, 257 views)
  Reply With Quote
Old 20th November 2017, 05:40 AM   #3
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally Posted by Ingborgbo View Post
Hello!

I would like to build myself a pair of TL speakers! That seemed pretty easy at first, I read how people thought designing them wasn't very complicated. Speed of sound, herz, cone area and easy as pie.
Well. No
Greets!

They really are once you learn some fundamentals of TL, and nowadays, T/S theory. That said, MJK took all the fun out of TL design over a decade ago for those 'not practiced in the art', so either follow the instructions or use the provided Excel program:

http://www.quarter-wave.com/TLs/Alignment_Tables.pdf

http://www.quarter-wave.com/TLs/Alig...tor_3_3_09.xls

All that's left then is to choose its tuning with ~25 Hz for a TL's version of a T/S max flat alignment and damp to 'taste'.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 20th November 2017, 12:15 PM   #4
Mario Pankov is offline Mario Pankov  Europe
diyAudio Member
 
Join Date: Aug 2007
Location: Sofia
Help needed with TL calculation
Download (if you haven`t already) a piece of software called Transmission Line. You can play with it and explore different setups. The Monacor is a nice woofer but its Qts is better suited for a ported enclosure (it doesn`t mean it won`t do well in a TL). If you haven`t bought the driver yet, perhaps you may also want to explore the possibility to use two smaller woofers instead of one large? If you position them correctly, you can equalize the ripples in the response of the TL and will be able to compensate for the baffle step loss by rolling the lower woofer around the transition frequency.

I gave up on transmission lines for anything larger than 8" as the line gets too long and the final cab, well, not very enjoyable for many. If done correctly, however, they do reward the hassle.
  Reply With Quote
Old 20th November 2017, 08:25 PM   #5
Ingborgbo is offline Ingborgbo  Sweden
diyAudio Member
 
Join Date: Aug 2017
Thanks for the replies!

I've been fooling around a bit with the info GM gave me, and yeah transmission lines sure are big.
1017 cm2 pipe that's 2,86m long, 290ish liters for 30Hz, if I remember correctly. I guess I could do that
but it wouldn't be easy to get the wife to accept those giants in the livingroom.
Sadly I haven't been able to find the program Mario mentioned but his idea of dual smaller woofers sounds
nice, however I guess the Vb would end up about the same.

I don't NEED silly low frequencies. I won't be using my speakers for movies - just music. So what Dissi
pointed out makes a lot of sense. Good ol' vented box. That's when I started to get silly wondering what
else I could get for about the same money as the SPH-300KE.

Dual 10" SPH-250TC
Dual 12" SPH-300TC
Or a 15" SPH-390TC

However, I don't JUST want loud, I want it to sound good. I'm going through the trouble of building myself
a pair of JC-80 clones and I don't want to ruin the overall sound quality by choosing the wrong woofers.
I listen mostly to industrial/EBM music and I'm no "true" audiophile so I'm not rediciously picky.

I haven't given up on TL but to be perfectly honest, becouse of size I'll probably end up with vented.

What's that fancy software you use, Dissi?
  Reply With Quote
Old 20th November 2017, 09:16 PM   #6
scottjoplin is offline scottjoplin  Wales
diyAudio Member
 
scottjoplin's Avatar
 
Join Date: Dec 2015
Location: Penrhyndeudraeth
A smaller driver also means a smaller cross section for the line, ie smaller cabinet
__________________
Woofer Assisted Wideband is the New Testament renounce the anachronistic acronym FAST
  Reply With Quote
Old 20th November 2017, 10:36 PM   #7
pkitt is offline pkitt  United States
diyAudio Member
 
Join Date: Feb 2009
Using the T/S specs provided by the OP, I modeled a tapered line 70" long and tapered at 15:1, having a beginning cross-section of 16"W x 15"D and an ending area of 16"W x 1"D. The woofer's center was located 14" from the beginning of the line. Without any stuffing the line's 1/4-wavelength resonant frequency tunes the system to 24 Hz, and this drops a couple of Hz with the first 2/3 of the line stuffed at 0.75 lb/ft3. The resulting f3 was a smidgen above 30 Hz and the response was all but flat from the knee in the curve up to 1 kHz (the limits of Martin King's software). The line's volume is ~150 liters.
Paul
  Reply With Quote
Old 20th November 2017, 11:01 PM   #8
Ron E is offline Ron E  United States
diyAudio Member
 
Ron E's Avatar
 
Join Date: Jun 2002
Location: USA, MN
TLines are not space efficient and they rarely get deeper than vented, even in a larger box. They also have nulls in the response and have a 4th order rolloff just like a vented. Transient response is also not likely any better than vented.

Before I saw Dissi's post I modeled a 130liter vented enclosure tuned to 27Hz and got an F3 of 28Hz. 10.2cm diameter vent, 18.3cm long.
__________________
Our species needs, and deserves, a citizenry with minds wide awake and a basic understanding of how the world works. --Carl Sagan
Armaments, universal debt, and planned obsolescence--those are the three pillars of Western prosperity. —Aldous Huxley
  Reply With Quote
Old 21st November 2017, 12:01 AM   #9
planet10 is online now planet10  Canada
frugal-phile(tm)
diyAudio Moderator
 
planet10's Avatar
 
Join Date: Oct 2001
Location: Victoria, BC, NA, Sol III
Help needed with TL calculation
Quote:
Originally Posted by Ron E View Post
TLines … have a 4th order rolloff just like a vented
That all depends on how they are stuffed.

dave
__________________
community sites t-linespeakers.org, frugal-horn.com, frugal-phile.com ........ commercial site planet10-HiFi
p10-hifi forum here at diyA
  Reply With Quote
Old 21st November 2017, 10:26 AM   #10
Mario Pankov is offline Mario Pankov  Europe
diyAudio Member
 
Join Date: Aug 2007
Location: Sofia
Help needed with TL calculation
Quote:
Originally Posted by Ingborgbo View Post
Sadly I haven't been able to find the program Mario mentioned but his idea of dual smaller woofers sounds
nice, however I guess the Vb would end up about the same.
Reason is his website is down by some reason. There i an offline installer here - Transmission Line Modelling Software

Dual smaller woofers would allow you to reduce the amount of stuffing because they can offset the line ripples caued by each if spaced orrectly. You have ot experiment but usually putting the drivers at 1/3 and 1/5 of the line length does the trick but sometimes they need to be spaced differently. With reduced stuffing, you will get more low end output.
  Reply With Quote

Reply


Help needed with TL calculationHide 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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Vas calculation didelcas Multi-Way 7 12th November 2017 01:53 AM
Help needed in Crosstalk calculation popilin Tubes / Valves 15 31st January 2017 02:36 AM
Zobel calculation, help needed! martinbls Multi-Way 5 23rd February 2011 08:42 PM
Calculation aguantesoda Solid State 5 31st December 2006 09:02 PM
Sime filter calculation help needed. Nordic Parts 20 15th November 2006 02:42 PM


New To Site? Need Help?

All times are GMT. The time now is 07:14 AM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2018 DragonByte Technologies Ltd.
Copyright ©1999-2018 diyAudio
Wiki