A very simple Quarter wave pipe the MidiTrike - 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 5th March 2012, 03:39 PM   #1
DrBoar is offline DrBoar  Sweden
diyAudio Member
 
DrBoar's Avatar
 
Join Date: Apr 2003
Location: Stockholm
Default A very simple Quarter wave pipe the MidiTrike

It really starts with two carboard pipes one inside the other
Click the image to open in full size.

I use a Philips 6-6.5" fullrange driver.
Diameter of he outer pipe is 1.5 the effective cone diameter (in my particular case 200mm) the length is 4 times diameter and distance to the floor 1/10 diameter. Inner diameter is 0.6 M-wall tickness. I used a 120mm pipe and that is close enough to the calculated 116mm i get with a 4mm thick outer tube. Lenght of inner tube is 0.6h in my case 480mm. Nominal lower frequency limit is 35000/h in mm here 44Hz. The actual tuning frequency is slightly above this. The proportion of diameters of inner to outer pipe should be kept at >0.5 and<0.7 and the h>at least 3 times M to behave as a proper pipe. But otherwise the design scale well up and down over a wide range.
Click the image to open in full size.
To get the end stoppers you need some MDF or wood. some wool cables and glue is also needed. I added some damping foam and bitumen pads in the top of the outer pipe and some crossbraces at the open end of the pipe.

This is how it looks assembled, I had a glue cartridge that was about to dry up so I was very liberal with it.
Click the image to open in full size.
And then some damping material and cables
Click the image to open in full size.
Connector and 3 legs
Click the image to open in full size.
I used a fabric that had that vintage look and a black foam top.
Click the image to open in full size.

Notes:
1.A elastic fabric sewn as tube with a snug fit was pulled over the tube and then stapled at both ends on the inside of the tube.
2. The top baffle is recessed the hight of the driver and the thickness of the foam cover.
3. Using a scissor to cut away some fabric before drilling is a good idea as the the drillbit never stops tearing up the cought fabric...

Measuring it with Woofer Tester 3 shows a fundamental resonance at 70 Hz as well as a damped third harmonic at 210 Hz and the fifith harmonic at 350 Hz. With no damping material the harmonics is far more visable.
Click the image to open in full size.

The driver has a sticker AD3710M but it looks like a later generation in that series of drivers.
Click the image to open in full size.

They really sound quite nice, largely due to the this little gem of a driver. I simply like to listen to music with these drivers, a far cry from say Philips 9710 that need a lot of taming to sound good.

This folding og pipes could also be used to make bass-traps

Last edited by DrBoar; 6th March 2012 at 06:20 AM. Reason: Photobucket thumbnailing did not work
  Reply With Quote
Old 5th March 2012, 03:52 PM   #2
diyAudio Member
 
Scottmoose's Avatar
 
Join Date: Mar 2005
Location: UK
Nice work!
  Reply With Quote
Old 5th March 2012, 04:21 PM   #3
diyAudio Member
 
Join Date: Aug 2004
Location: Karlskoga
Nice work

Do you have some bigger pictures of your creations,I can only see small pictures. :-))
__________________
/betong gör livet tyngre
  Reply With Quote
Old 6th March 2012, 08:39 PM   #4
DrBoar is offline DrBoar  Sweden
diyAudio Member
 
DrBoar's Avatar
 
Join Date: Apr 2003
Location: Stockholm
OK bigger pictures and added one of the driver as well. I will get a scale and measure so that I get equal amount of wadding in both pipes and see if they match better than now.

I also plan to buy the PE OmniMic measurment system, that will help the tweaking,perhaps, those omnidirectional speakers are hard to measure.
  Reply With Quote
Old 7th March 2012, 04:37 AM   #5
diyAudio Member
 
Join Date: Aug 2004
Location: Karlskoga
Thank you.Now I see the pictures.Nice. Tackar.:-)
__________________
/betong gör livet tyngre
  Reply With Quote
Old 7th March 2012, 09:27 AM   #6
Squeak is offline Squeak  Denmark
diyAudio Member
 
Squeak's Avatar
 
Join Date: Jul 2007
Location: Frederiksberg
You could do some 180 degree reflectors, by simply creasing an oval piece of plexiglass with a heatgun and a ledge, then put it at a 45 degree angle over the cone (oval to compensate for anisotropy). This would improve room behaviour, highs and allow the speaker to be placed near room boundaries better.
  Reply With Quote
Old 7th March 2012, 09:07 PM   #7
DrBoar is offline DrBoar  Sweden
diyAudio Member
 
DrBoar's Avatar
 
Join Date: Apr 2003
Location: Stockholm
In the original articles they suggest experiments with reflectors. The problem is that the midiTrike sound quite light as it is. With the small round baffle there is a 6dB loss below 600 Hz and reflecting more hight frequency sound can cause a even "lighter" balance. Mind you it has nothing of the shrillness like the 9710 it simply would need som fatter low end to even up the balance. Perhaps I can make a passive filter to shelve down everything above 600 Hz...
  Reply With Quote
Old 9th March 2012, 10:05 AM   #8
DrBoar is offline DrBoar  Sweden
diyAudio Member
 
DrBoar's Avatar
 
Join Date: Apr 2003
Location: Stockholm
Added a baffle step compensation filter calulated values are 3.5 Ohm and 1mH, for a 6 dB step at 570 Hz. I used 4.7 Ohm and 0.85 mH as that is what I had at home, remember this is a low cost project. For the Zobel calculated values are 20 microF and 4.4 Ohm I used 20 MicroF and 6.8 Ohm. Keeping it vintage and low cost I use very old electrolytic caps and some of the wires are not even copper and very very thin ( harvested from some old speaker crossover wires). So much for ultra fidelity plastic caps and foil coils...

Green curve is driver as it
Pink curve shows the effect of adding the Zobel, even if the resistance is 50% high it still works well the driver impedance is much flatter and reach 5 Ohms at 12 kHz instead of 2 kHz.
Blue curve shows the baffle step added to the mix. At the nominal cutof the impedence difference is about 1.5 Ohm and between 1.5 and 20 kHz it is pretty constantly 4 Ohms.

It sounds better with a better bass to higher range balance. Is there room for improvements? Sure is, but this was a major step forward. I would like to get a lift in the last two octaves as the driver is facing upwards...

Perhaps I shall look into reflectors, it never ends does it

Click the image to open in full size.
  Reply With Quote
Old 9th March 2012, 10:53 AM   #9
diyAudio Member
 
vitalstates's Avatar
 
Join Date: Jan 2006
Location: uk
brill!

a few years ago I played with putting an FE167 in a succession of cones to approximate an elongated horn. I gave up because it seemed overly complicated. Well done for persevering.

who dares wins.
Attached Files
File Type: doc confo.doc (26.5 KB, 30 views)
__________________
There is nowhere you can be that isn't where you're meant to be
www.vitalstates.org
  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
Goodmans Axiom 201 in TQWT Voigt Quarter Wave Pipe? calvert73 Full Range 60 3rd January 2012 09:32 PM
Help (very much) wanted for simple quarter-wave design for cheap drivers. Spasticteapot Full Range 9 4th May 2006 09:14 PM
large quarter wave, HELP!! psychosteve Multi-Way 5 8th October 2004 02:08 PM
Quarter Wave Recommendations Kofi Annan Multi-Way 37 2nd June 2004 02:44 AM


New To Site? Need Help?

All times are GMT. The time now is 09:55 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