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

MCM 55-1205 sealed or TL?
MCM 55-1205 sealed or TL?
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 5th May 2019, 07:28 PM   #1
Frankenspeakers is offline Frankenspeakers  United States
diyAudio Member
 
Join Date: Dec 2018
Location: Middle of a desert. Kalifornia expat.
Default MCM 55-1205 sealed or TL?

Hello all:

I have a few MCM 55-1205's* kicking around and want to experiment a bit. Some are currently in .3 cu ft sealed boxes which actually sound better than they should. I want to see if they are candidates for TL duty. The first kicker is I want to use a 2.5 TMM configuration in leiu of BSC, rolling the second one off around 600~ Hz instead of burning 3-6 dB up in a resistor.


Second is I want to see if it is practical to use a tall/ slim straight / folded TL to get what low end there is.

I also found out I'm a few days late to get Martin King's mathcad files, so I am trying to bend my non-calculus brain around the still available charts. I also found a couple of calculators to try modeling some configurations instead of trial & error. Paper is cheaper than sawdust.


What I have been exploring are iterations on the Weems Pipe, but with updated math for the TLL with the SL>SO. One spreadsheet wants something like a BIB line, the other looks more reasonable but I'll have to translate some German terms... Looking for some more (non-calculus) solutions, or a line on the currently unavailable MJK mathcad files.



Thanks in advance for your feedback, pointers, and suggestions .


* Here is the driver sheet: www.newark.com/mcm-audio-select/55-1205/5-1-4-poly-treated-cone-woofer/dp/36C6658
Fs=65Hz, Qts~.77, Vas=.388ft2.
  Reply With Quote
Old 6th May 2019, 08:41 AM   #2
Lojzek is online now Lojzek  Croatia
diyAudio Member
 
Lojzek's Avatar
 
Join Date: Feb 2012
Location: Croatia
Hi,

Build a larger vented box, you can simulate and optimize to a reasonably good loading and then plug the port if needed. Corner loading can further help to decide what sounds better. Try to measure the TSP yourself to further reinforce your confidence in doing the right thing.


p.s. your link appears to be damaged, an excess of letters just before www.
  Reply With Quote
Old 6th May 2019, 04:58 PM   #3
DickHertz is offline DickHertz  United States
diyAudio Member
 
Join Date: Feb 2006
The best candidates for TL enclosures are woofes with a Qts around .40.
  Reply With Quote
Old 6th May 2019, 05:48 PM   #4
pkitt is offline pkitt  United States
diyAudio Member
 
Join Date: Feb 2009
Yep and within the range of 0.35 to 0.45 (and sometimes up to 0.50 or so). The OP's choice of this quite high-Qts driver will result in a really ugly-looking response in a TL.
Paul

Quote:
Originally Posted by DickHertz View Post
The best candidates for TL enclosures are woofes with a Qts around .40.
  Reply With Quote
Old 6th May 2019, 07:34 PM   #5
Frankenspeakers is offline Frankenspeakers  United States
diyAudio Member
 
Join Date: Dec 2018
Location: Middle of a desert. Kalifornia expat.
Thanks for the responses Gentlemen, I have looked at the plots for sealed & reflex boxes, and the driver dosen't seem to gain much unless I go over 2 cubic feet for a 5.25" driver. Even then, I have to push the tuning down into the 40's to level out the hump. (will post when iPad starts talking to desktop). Sealed .8 cu.ft. -1.5 look OK.



I know that .4 Qts is a good ballpark for reflex enclosures because the Vas ~optimal cabinet volume, but I was under the impression that higher Q drivers were 'happier' in TL's.



Does anyone have a line on martin King's "Lost files"?



Will post some graphics when the desktop is more obedient.


Mucho Gracias!
  Reply With Quote
Old 6th May 2019, 10:07 PM   #6
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Greets!

As already noted, inverse tapered TQWT are best suited to lower Qts' systems same as for BR alignments. Beyond ~0.312 Qts' to ~0.54 Qts' is better suited to constant [straight] tapered pipes with expanding TQWT [ pipe horn] up to the practical limit where the mass corner has dropped to Fs [Fs/Qts' = Fs].

The Weems Pipe is a vent terminated [mass loaded] pipe horn aka ML-TQWT in MJK 'speak' and I choose to call a ML-horn to differentiate it from his inverse tapered ML-TQWT.

Adding 0.5 ohms for wiring/whatever brings the Qts up to a ~0.811 Qts' = Qts + any added series resistance [Rs]: HiFi Loudspeaker Design

I'll post some Hornresp straight pipe, pipe horn sims as time permits.

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.

Last edited by GM; 6th May 2019 at 10:11 PM.
  Reply With Quote
Old 6th May 2019, 10:12 PM   #7
GM is offline GM  United States
diyAudio Member
 
GM's Avatar
 
Join Date: Jun 2003
Location: Chamblee, Ga.
Quote:
Originally Posted by Frankenspeakers View Post
Does anyone have a line on martin King's "Lost files"?
What 'lost' files?

GM
__________________
Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
  Reply With Quote
Old 15th May 2019, 08:44 AM   #8
Frankenspeakers is offline Frankenspeakers  United States
diyAudio Member
 
Join Date: Dec 2018
Location: Middle of a desert. Kalifornia expat.
Quote:
Originally Posted by GM View Post
What 'lost' files?

GM

Hi GM: The files I was referring to are Martin J.King's worksheets. I contacted Martin and found that they are no longer available.



"Hi Frank,
Unfortunately I stopped new user access to the MathCad worksheets at the end of 2018. I suggest looking into HornResp or Leonard Audio's TL program, both are available on the DIYaudio forum.
Sorry,
Martin"


Since those are no longer an option, is there a good copy of the Leonard Audio TL program available? I'm reading up on HornResp which looks to have a bit of a learning curve to become proficient.


I did try using Keith Webb's spreadsheet from MJK's Quarter-wave site, and the size is a bit big for 5.25" drivers. It does appear that Bl & Qt do have more of an affect than I would have supposed.



What effect does reducing (or porting the open end of the line (I see it is now called "mass-loading")? Seems like it would diminish the loading & efficiency.


Thanks,


Frank

Attached Images
File Type: jpg 55-1205 Excel screen shot.JPG (93.8 KB, 61 views)
File Type: jpg 55-1205 sl-sq=25.JPG (70.4 KB, 58 views)
  Reply With Quote
Old 15th May 2019, 09:14 PM   #9
Frankenspeakers is offline Frankenspeakers  United States
diyAudio Member
 
Join Date: Dec 2018
Location: Middle of a desert. Kalifornia expat.
Quote:
Originally Posted by Frankenspeakers View Post



Since those are no longer an option, is there a good copy of the Leonard Audio TL program available?

Any ideas?



Thanks in advance.
Attached Images
File Type: jpg Cannot DL app...JPG (60.0 KB, 33 views)
File Type: jpg Cannot DL app(2).JPG (54.0 KB, 34 views)
  Reply With Quote
Old 16th May 2019, 12:31 AM   #10
BHTX is offline BHTX  United States
diyAudio Member
 
BHTX's Avatar
 
Join Date: Feb 2006
I recommend using these drivers free air and driving near xmech with a 10Hz sinewave.
  Reply With Quote

Reply


MCM 55-1205 sealed or TL?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

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
Vam 1205 CDM 12.5 Naim CD5 hifive Digital Source 13 15th September 2014 09:00 AM
Sears RE-1205 AM/FM resever QsoftStudios Solid State 6 13th February 2012 05:58 AM
Meridien 560 mod mech from 1205 to CDM12.4 cm Digital Source 3 25th February 2011 07:49 PM
Vam 1205 /vam1250 / Cdm12.5 jmmartins Digital Source 1 1st January 2010 05:44 PM
Where to buy CDM 12.5 (aka VAM 1205) memorylane Digital Source 1 11th May 2005 06:51 PM


New To Site? Need Help?

All times are GMT. The time now is 01:10 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 14.29%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio
Wiki