Zilch's AK Design Collaborative - Econowave Speaker

Foofighter -- interesting. Any measurements before/after on this mod?

Sorry but no measurements. Everything i wrote was based on listening impressions. I should say that i have pair of d220ti that is not yet treated this way but i've decided to do it the same way as Sync (project number 60) that i've posted pictures of. The cloth that he used in the part of the chamber just above the Ti membrane is cotton. One could use a bit of cotton wool just to se if that brings any sound improvement.

Everyone can try to se if this fits for him. In that case i would use some modeling clay in gaps of compression chamber inside. On the outside a lot of modeling clay as well.

That way if one is not pleased, nothing is ruined. You just demodify it and that is it. It costs virtually nothing. Knock on the back side of d220ti and on to the D250 or d2500ti to see for yourself. The difference is huge. Aluminium is material that does not resonate that easily unlike plastic.

I don't think that there will be some important changes in FR graph of modified driver. We used this only to kill resonating plastic of compression chamber. Sound stays the same but without distortion created by chamber itself hence less harshness.
 
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ff, Ok, will give it a try. See if I can do some meas with it, too, might see something in the response if there are resonances bad enough.

Sorry but no measurements. Everything i wrote was based on listening impressions. I should say that i have pair of d220ti that is not yet treated this way but i've decided to do it the same way as Sync (project number 60) that i've posted pictures of. The cloth that he used in the part of the chamber just above the Ti membrane is cotton. One could use a bit of cotton wool just to se if that brings any sound improvement.

Everyone can try to se if this fits for him. In that case i would use some modeling clay in gaps of compression chamber inside. On the outside a lot of modeling clay as well.

That way if one is not pleased, nothing is ruined. You just demodify it and that is it. It costs virtually nothing. Knock on the back side of d220ti and on to the D250 od d2500ti to see for yourself. The difference is huge. Aluminium is material that does not resonate that easily unlike plastic.

I don't think that there will be some important changes in FR graph of modified driver. We used this only to kill resonating plastic of compression chamber. Sound stays the same but without distortion created by chamber itself hence less harshness.
 
ff, Ok, will give it a try. See if I can do some meas with it, too, might see something in the response if there are resonances bad enough.

:lurk:

I found some black speaker carpet that had carpet glue on the back, cut it to fit the center of the cap and put some black butyl putty in the two other spots. Listening so far is inconclusive, I'll try more tomorrow.

I am kind of surprised that this was not discussed earlier, when there was talk of damping the diaphragm with something. The sound of the plastic when struck is much improved (less) on the one I modified.

All the JBL drivers I have ever opened have had some sort of pad on the back cap to absorb the rear wave from the diaphragm, so It seems like a no-brainer to put that in.
 
Selenium D220Ti Mod

FF, thanks for the idea. I tried it today.

Opening up the rear was very easy. Then I damp the rear chamber with 3 layers of cotton kitchen wipe. I also damp the flimsy rear cover with bluetack.

dsc_5216.jpg



Below is the measurement. Blue=original, Black=modified. The frequency response is virtually the same. If you observe closely there are breakup modes at 7.5khz, 10khz. 12khz, etc. This is consistent with typical metal dome breakup.

The diapragham structure is quite large which explains why the breakup frequency is low. Normally with 1" dome the breakup is around 15khz (see Seas 27TBCF/G). My understanding is D2500 also uses Titanium but no harshness. I would be interested to see the measurement.

I normally eq with small notches 7.5kh and 12khz. The 12khz breakup is what causes tizziness. This measurement is without EQ.

Indoor, 89cm, design axis, 0deg, no smoothing
08c89cmmodifiedvsoriginalT.png



I will post listening impressions soon!


As comparison, this is DE250 on home made waveguide. Damn smooth. As seen there is virtually no breakup there. Maybe just a soft one at 17khz.

Outdoor, 190cm, 11deg, no smoothing
de250.png
 
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FF, thanks for the idea. I tried it today.

...................................................


I normally eq with small notches 7.5kh and 12khz. The 12khz breakup is what causes tizziness. This measurement is without EQ.

Indoor, 89cm, design axis, 0deg, no smoothing
08c89cmmodifiedvsoriginalT.png



I will post listening impressions soon!

Thanks for the measurements and for confirming the claim that there won't be any important changes in FR graph of modified driver.

I think that you could do the A/B test (modified/not modified). We haven't tried that one yet. That would be the right way to determine for yourself if there is any sound improvement.
 
In the time domain we can observe the behavior based on same data.

There is a difference on how the resonance behave between original & modified. I'm not sure if this is for the better or worse. Observe the area from 9khz - 20khz.

The original settled quicker but the modified has less amplitude after that.


d220Tioriginal.png




d220Timodified.png



The DE250 which is 3x the price shows that it is indeed much superior.

de250wf-1.png
 
There is a difference on how the resonance behave between original & modified. I'm not sure if this is for the better or worse. Observe the area from 9khz - 20khz.

interesting! I've yet to get to grips with measurements beyond basic frequency response. I'd be curious to see the same measurement for the D2500.

HOLMIMPULSE has a graph of THD it produces from it's sweep, it would be interesting to see if that changes much with the damped plastic casing.
 
HOLMIMPULSE has a graph of THD it produces from it's sweep, it would be interesting to see if that changes much with the damped plastic casing.

I just did the "tweak", using a packet of bluetak and a cutout square of kitchen wipe, Holmimpulse measurements taken before and after do show a reduction in a peak of 2nd order harmonic distortion at about 12K.

Measurements taken at about 75cm from the waveguide, woofer disconnected, but using the highpass crossover.

d220-2ndHD-before-and-afterblutak.png


I wonder if I can smear anything in blutak to reduce the 7K peak as well?

I also did some Arta burst decay graphs and got results similar to Gainphile's, given I did them quickly and ddnt set the scales the same.
 
The 12khz breakup is what causes tizziness. This measurement is without EQ.

You have to remember, this is a price point item. That breakup is also what gives this driver a LOT of its extension on the high end. The Eminience 2002 is very similar in this regard. Get rid of that breakup node and you'll also give up some extension and the high end compensation likely wont be enough. Its an inexpensive driver that sounds better than it has any right to, but a certain amount of what I called "fizzyness" rides on the high end.

To large extent, I felt this effect was much improved through charge coupling the crossover. All that's in here somewhere in this gigantic thread.:D

russellc
 
...
I wonder if I can smear anything in blutak to reduce the 7K peak as well?

...

Aquaplas? (On the diaphragm.) If it moves, coat it...

It's good to see some measurements showing a change. Maybe some more absorbent materiel is the next step? Foam? Plush weave carpet (1/4") is what I tried. I'm going to break out the carpet glue (6700), that stuff is a really good damper, like a coating of rubber. Stays soft for years. For the cap, not the diaphragm.
 
Are there any commercially available adapter rings to put a 12 inch woofer in a 15 inch hole? Want to build the deluxe design in a Mach 2 cabinet.
 
Yeah. Apartment dweller without workshop space/router so I was looking for an alternative solution.

Gotch' ya. If you can't find what you are looking for, try a woodworking store. They normally will have a board with names of guys in your area that can make stuff. The ones I've used are retired and don't charge much at all.
 
I serched the thread because I thought I remembered this being discussed but couldn't find it.

Speaking of woodworkers, I was just thinking I could pay a visit to one of the car stereo places that does custom subwoofers and see if they would do it.
 
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I think there is a source for various size rings talked about in this thread somewhere...

Yes, there was a place in this thread where someone used a ring as an adapter. If I recall correctly, they got it from a hobby place like hobby lobby, I forget what they were for now......making a wreath maybe? But they worked great for someone to put a 10 inch driver in a 12 inch hole.

Russellc
 
I've seen plant stands that are basically, MDF circles with cork on one side. That could work great...

Regards,
Gordon.
 
You have to remember, this is a price point item. That breakup is also what gives this driver a LOT of its extension on the high end. The Eminience 2002 is very similar in this regard. Get rid of that breakup node and you'll also give up some extension and the high end compensation likely wont be enough. Its an inexpensive driver that sounds better than it has any right to, but a certain amount of what I called "fizzyness" rides on the high end.
russellc

Yes, and I made it very clear on the posts above that DE250 is 3x the price of D220Ti.

I wonder how something of similar price like DE10 would work. It does not use metal dome but mylar like DE250.
 
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