Econowave Speakers

[richidoo]

Thanks Tim. Good to know you are a tool collector too, never know when I might need a metric right angle widget remover.  

I got the ports out. As usual with my epoxy jobs, a firm tug will undo it. Actually, I only used small spots of epoxy hoping it could be removed in case of disposing of the boxes.

I'll figure some way to cut them on the table saw.

I'm listened to some tracks with no ports installed, just the 4.75" diameter, 3/4" deep hole in the plywood. The mids sound better, very detailed like the horn, fast and dense. No noticeable chestiness on male vocals.  YAY!! that's worth celebrating.
 

The bass is still punchy, but not as low or intense as with the 4" long ports. And there is something weird about the sound of the bass now, kinda smeared tone, and it feels separate from the upper freqs. Sticks out like sore thumb. Could be the 4.75" dia. holes are too large diameter without the molded 4" ports in place. And definitely not as pretty with caulk remnants hanging out.

[richidoo]

For anybody interested in some reading about port lengths:

Troels suggests that the standard port length calculations used in almost all software simulators are wrong, and the ports usually need to be shorter.
http://www.troelsgravesen.dk/vent_tuning.htm

http://www.ehow.com/info_8575773_effects-longer-subwoofer-port.html

Obligatory sreten wisdom:
http://www.diyaudio.com/forums/multi-way/208509-shall-i-extend-shorten-length-port-if-i-want-more-extended-bass-volume.html

Serious theory on how ports work:
http://www.hometheaterhifi.com/volume_5_2/cmilleressayporting.html

And another, even more technical
http://www.6moons.com/audioreviews/haigner/sidebar.html

[richidoo]

Shane came today and gave them a qualified thumbs up. Good potential, needs TLC

I just swapped out the B&C DE250 compression drivers for the Radian 475PB. They need to break in, but initial impression is even more detail. Nothing offensive, but a lot of detail. They sound good so far, hopefully it will get even better.

Shane reminded me that I can tune the ports accurately by watching the port impedance peak using WT3. That will help. Removing the ports for cutting each time is a drag, so I want to make an adjustable length port so I can fine tune it in place. Not sure how to do that... any ideas? The inside surface should be smooth for the whole length. Maybe it doesn't need to be perfect just to find the right length. Like using cheap caps to find the right value then replacing with good ones.

I bought metal angle brackets to make some removable cross braces for the front baffle above the woofer. It is moving a lot without the braces and this is smearing lower midrange. Bracing the bottom of the woofer helped a lot, so this should too. Thinking about econobox 2.0.

[stereofool]

Rich,
I think that I refered you to this site before, but I think that he has updated his crossover software.

http://www.bodziosoftware.com.au/

[richidoo]

Thanks Steve. 

I was a beta tester over the last 2 years for the just released Dirac Live speaker management room correction software. It uses both FIR and IIR filters were each is appropriate in the frequency range. Dirac is used in Bentley and BMW car systems and super high end theaters. They are finally offering a PC version for audiophiles.  No convolution hosts, it runs as a service in Windows. My next speakers will use it.

http://www.dirac.se/en/consumer-products.aspx

[richidoo]

I put the removable braces in to hold the top of the woofer. That cleaned up the lower mids a lot. Adjusting the port length and adding more stuffing still remain to optimize LF.

The Radian CD is breaking in nicely. It is strong in the treble, and extremely high detail, but low distortion of a CD so it is not fatiguing. It will probably need some adjustments to the xo to mate perfectly with this woofer. I don't sense any edge, acoustic instrument and vocal tone is excellent. But the treble is a bit strong for me.  I think it is flatter and more extended or maybe even rising HF compared to the DE250. It seems clearer and purer than DE250. It costs about twice as much.

I will do some measurements tomorrow to see where we are with FR and port tuning.

[richidoo]

Thanks Doug. Yes it will be interesting.  Sounds like a nice sounding rolloff. It certainly has plenty of sizzle where it counts.

I did run a quick impedance sweep tonight to see just where the port tuning is now. See attachment.  It is at 29Hz, even AFTER I shortened the ports by almost 3 inches! It should be tuned to 38Hz! So that explains the sounds we're hearing, and why 1st iteration was a bass bomb with 7" long ports.  

I'll shorten them further to reach 38Hz, hopefully that will sound real nice.  

[Response Audio]

Those are some very nice speakers Rich. Are you going to do any further finishing to the cabinets? Either way, they look sharp as they are. How's the monkey doing?

[richidoo]

Hi Bill, thanks!!

I like the size and shape of them, and not too heavy...
I will stain and varnish them if I ever get them sounding how I want. Hasn't ever happened yet, but this one shows promise.

My daughter used to be a webkinz nut, she has about 60 of them. So everybody in the family has a webkinz monkey. Mine is named Thelonius, he is a jazz monkey.    She made the "helmet" for him, it is for space travel, and protection while listening to my speakers up close. 

[richidoo]

Shortening the ports did not work. 2" port length tunes to 31Hz, but not 38Hz that I need. I must have made a mistake somewhere in my box design, because WinISD said I needed 7" and that sounded very bad. I will switch to Jeff Bagby's Woofer Box simulator as Face suggested. I gotta find my Office 2000 install discs first to install the Analysis Tookpak.  It doesn't run in OpenOffice.   

[richidoo]

Found the disc (miracle) and have WooferBox up and running. Spreadsheet seems easy enough to use. Thanks Mike for the reminder about this.

Based on the work today I would be surprised if I don't have to build another box.  I need to check my numbers to find out what went wrong. I think the box volume is too big.

[mgalusha]

Rich, I can plug the numbers into Winspeakerz if you like and see what it spits out.

[richidoo]

Thanks a lot Mike, that will be interesting.

I used the Eminence published T/S specs into WinISD:
Fs = 37 Hz
Re = 5.04 ohm
Le = .46 mH
Vas = 147.2 liter
Qes = .44
Qms = 3.13
Sd = .052 m^2
Xmax = .005 m
Qts = .39

WinISD spit out max flat FR (attached) and specs for Butterworth ported alignment:
131.7 liters
38.3Hz
2 vents 4.02" diameter and 6.89 inches

I'll verify the T/S specs for my actual drivers. Could be they are too far off from the factory published specs I used, but that's not like Eminence.  I'll also verify the actual volume of my box. Could have been a snafu in the unit conversion or measurements.  But it will be interesting to see if WinISD and Winspeakerz agree about these numbers.

Thanks!!
Rich

[richidoo]

I'm having trouble getting the WooferBox spreadsheet to work in Excel 2000. Everything works except all the graphs are blank. Toolpak is installed. Any ideas?

[richidoo]

Got it working. Nice program.

I entered the specs, and it said use one 4"w x 3"L vent, or 2 4" x 7" (like WinISD.) But WT3 says the 4x3 port rings at 24Hz, not 37Hz like it should.  So I don't know what's going on. I verified volumes, but I did not measure the actual driver yet.

I am about to read vented box chapter in loudspeaker cookbook to try to gain an intuitive feel for what is supposed to be happening. Maybe get some simple formulas to do by hand. 

At least WinISD and WB seems to agree, so that means reality is the problem.