Zilch's AK Design Collaborative - Econowave Speaker

[foofighter]

This may be of interest, my eWave *with* foam

The foam causes attenuation of -2db.

blue: original
black: with foam insert

The attenuation is quite uniform, as shown by compensated graph below. It tracks very identical to no-foam. So this is good. Only in extreme highs that it deviates.

blue: original
black: with foam insert and +2 db.

The changes to the sound is subjectively subtle, and that is consistent with the above plots. I thought horn coloration is reduced, but at the expense of airy-ness. It's a good tradeoff. Is it a must? definitely not but I got them cheap.

Have you used reticulated foam, closed cell or open cell ? I've seen Geddes wrote that he uses closed cell foam because "reticulated can't really do anything" few days ago...

 

[dumptruck]

Have you used reticulated foam, closed cell or open cell ? I've seen Geddes wrote that he uses closed cell foam because "reticulated can't really do anything" few days ago...

That can't be right; wouldn't closed cell foam just block the HF completely? Here's something: http://www.diyaudio.com/forums/multi-way/132036-question-dr-geddes-about-his-wg-foam-plug.html

 

[foofighter]

That can't be right; wouldn't closed cell foam just block the HF completely? Here's something: http://www.diyaudio.com/forums/multi-way/132036-question-dr-geddes-about-his-wg-foam-plug.html

I was very much surprised for myself... The thread is not in this forum i think. He was talking with Paul Spencer (his avatar is red spade on that forum). They were talking about the foam and its availability in Australia also.

Maybe i am mistaken. Like i said, i was surprised by the statement too...

 

[EarlK]

Thanks Frank

I got my first plugs from these guys (way too expensive) and looking at the site, I am using open cell and not reticulated. When I look at what I have, the number of non-open cells walls is very small. The reticulated is far too open to do much of anything. It would take a lot of it.

I compared the stuff I got with what you use. About the same PPI. There was a difference, but not much. Yours had a few shiny surfaces, mine did not. Comparable thicknesses pass about the same amount of light. The stuff I bought worked. I got a big hunk and I filled up a large, (22"X5" mouth), and ugly sounding exponential horn with it and gained great improvement in sound quality - the honk practically disappeared. (Compared to a good waveguide that horn, even with foam, is not a great device).

>>>> From here !

EarlK

 

[foofighter]

Bravo :thmbsp:

I was starting to believe that i am losing my mind

So, it is not reticulated or closed cell. It is open cell

Six forums are mixed up in this blender that i call head

 

[gainphile]

The foam that I am using *does* make a difference (see graphs). It's 30ppi reticulated foam.

After some listening I tend to not like it. Initially I thought the sound was very smooth, but after 2 days I noticed that high frequency resolution is missing, not "airy", muted cymbals etc. This is with the corrected XO to compensate the loss -- so identical frequency response.

I have since tried a less thicker foam (about 7cm) and only attenuates at -1db, but still I did not like it. The tradeoff is too great for the obtained "smoothness".

I'm surprised that no one reported this tradeoff with popular gedlees speakers. All review seems to be glowing.

Paul Spencer whom I know very well noticed the same tradeoff, except that he tends to like it over time.

 

[djnagle]

Are you towing in the speakers? I've found that with my ESS-waves, they sounded much smoother without tow in. I did have the little Kegger foam plugs in them, but when I had them pointing straight at me, they were a little ragged. When they pointing straight out, they where much smoother.

 

[audiothings]

Never built a multi way speaker before. Have bought all parts for the standard kit... Will build next week. Bunch of questions... please see pic. Have deided to go sealed, for now... the room is going to be quite boomy and I don't want the speaker to add to the mess.

* Is the 12" gap between the mid points of the woofer and CD acceptable?

* WinISD seems to suggest that I will get f3 in the mid 40s and f10 in the mid 20s with a 160L sealed box such as this... is this making sense?

* Will I need more bracing than what is provided by the chipboard used to make the compartment for the CD? If so what sort of bracing would be suggested for this box?

* Is the OC703 infill going to do a good job, the way I'm using it? Can't get polyfill here...

* If I don't like the sound of it sealed, can I put ports in later? The volume is about 160L.

* Do I really need to put the CD in a separate compartment?

* Is the insulation necessary around the CD, or is it sufficient to insulate the woofer enclosure?

Any guidance is much appreciated.

 

[dumptruck]

Wow, that's some very old-timey construction you've got there audiothings!
I can answer some of these:

* Is the 12" gap between the mid points of the woofer and CD acceptable?

If you're building boxes from scratch, you have every reason to space them as close as possible.

* WinISD seems to suggest that I will get f3 in the mid 40s and f10 in the mid 20s with a 160L sealed box such as this... is this making sense?

Looks like that would be approaching critically-damped size, and yeah, that sounds like what you'd get. Power handling will be low in the bass region, around 20W, ~100dB.

* If I don't like the sound of it sealed, can I put ports in later? The volume is about 160L.

Yes. Actually with the box this huge you'll get a little more power handling ported.

* Do I really need to put the CD in a separate compartment?

Most people haven't been.

 

[bwaslo]

Are you towing in the speakers? I've found that with my ESS-waves, they sounded much smoother without tow in. I did have the little Kegger foam plugs in them, but when I had them pointing straight at me, they were a little ragged. When they pointing straight out, they where much smoother.

They shouldn't point straight at you, toe them in more. They should point toward a spot five feet or so in front of you, you want to be off-axis at the other edge. That's how the very large sweet spot effect happens and near wall reflections get minimized. (Assuming that's what you're after)

 

[mor2bz]

If the lowpass is about 150 hz. do you think the tube amp would be in danger/ ? thanks

Anyone considering passive speaker level biamping with tube amps should carefully think about what that means to the loading of the amp.

For example in the case where a passive highpass filter is used between a speaker and the output of the tube amp, and the tube amp receives a full range input signal, the tube amp is unloaded (open circuit) for the portion of the frequency range below the HP crossover. Running a tube amp unloaded can be a really bad idea for the amp, and it definitely wastes voltage swing, since the amp will use up its voltage headroom amplifying an unloaded signal.

I don't even want to think what this does to the stability of a feedback amp with marginal bandwidth.

I think most people will have figured this out but I want to make sure that nobody is running passive crossovers and tube amps in a manner that is dangerous or wasteful.

 

[mor2bz]

this 150 hz filter is not in a econowave. hats off to your forum
and all the respect paid to Zilch. I just got some old Frazier mark V and
now i am starting to think EW.

 

[djnagle]

They shouldn't point straight at you, toe them in more. They should point toward a spot five feet or so in front of you, you want to be off-axis at the other edge. That's how the very large sweet spot effect happens and near wall reflections get minimized. (Assuming that's what you're after)

I think it depends on the room. I've tried that in my room and it never sounds that good. I've tried it with many different speakers to no avail. I've heard it done in other rooms and it sounds good.

 

[audiothings]

Thank you dumptruck.

Based on your advice, I have changed the design, like this:

Really looking for more inputs here... never done such a thing before, and being in India, I had to go through a lot of trouble and expense acquiring the components... don't want to screw up...

 

[Mmaxed]

I think you should be good to go audiothings. I am no expert like some here, but I built my standard ewaves with much less attention to detail than you have in the works. They are in repurposed cabs and they sound very good. I have the foam in mine like has just been discussed. It's not coming out for now. Much smoother to my ears. My next step will be to dampen the WG's and drivers. There is a thread here about it, but I can't find it now.

Good luck and enjoy the ride! It's worth it.

 

[4343]

...

Really looking for more inputs here... never done such a thing before, and being in India, I had to go through a lot of trouble and expense acquiring the components... don't want to screw up...

That's a nice design. I like the dual layer construction.

I'd run two more braces, one drawn like the ones just added (side-to-side) but up against the front baffle between the waveguide and the woofer. That's the weakest part of any speaker box. Also, from the rear of that side-to-side brace run one to the rear panel.

OK, I'd like to run one down the middle of the rear panel (top-to-bottom), and one down each side panel (top-to-bottom again) to really make sure the box is "dead". Tie your side-to-side braces to the top-to-bottom ones. Also the front-to-back brace should tie to the rear top-to-bottom brace. I find that this is the minimum amount of bracing that I can stand to build. Not that I find that the minimum amount that I can listen to, just that as long as I'm in there, it's going to be better...

Here's an example of shelf bracing:

http://www.audioheritage.org/vbulle...Woofer-Project&p=260233&viewfull=1#post260233
The next post in that thread:

http://www.audioheritage.org/vbulle...Woofer-Project&p=260234&viewfull=1#post260234

And the next:

http://www.audioheritage.org/vbulle...Woofer-Project&p=260236&viewfull=1#post260236

This takes the bracing I've described to it's logical conclusion, to put it mildly.
There's more, if you want to start at the beginning of that discussion:

http://www.audioheritage.org/vbulle...78-2245H-Sub-Woofer-Project&highlight=bracing

 

[audiothings]

Thank you Mmaxed... that is just the encouragement I was looking for.

4343, thank you. I am looking up those threads with the bracing examples.

Will post again with (unfinished) pics... They will be tested for a while at my studio before they go to their final home, where they will be finished according to the decor.

Thanks again,

Jai Shankar.

 

[juniorJBL]

I would not sandwich the building paper between the 2 pieces of mdf, unless you have a bonding agent just for wood and asphalt and you can put it together before cutting. You might get interaction between the glue used for the mdf and the asphalt and your cab will slowly start to degrade.

I would glue your 2 pieces together before cutting or just use a single piece of 3/4" or 1".

If you were to laminate 2 pieces of mdf together then I might think of fiberglass or kevlar or similar.

 

[foofighter]

The foam that I am using *does* make a difference (see graphs). It's 30ppi reticulated foam.

After some listening I tend to not like it. Initially I thought the sound was very smooth, but after 2 days I noticed that high frequency resolution is missing, not "airy", muted cymbals etc. This is with the corrected XO to compensate the loss -- so identical frequency response.

I have since tried a less thicker foam (about 7cm) and only attenuates at -1db, but still I did not like it. The tradeoff is too great for the obtained "smoothness".

I'm surprised that no one reported this tradeoff with popular gedlees speakers. All review seems to be glowing.

Paul Spencer whom I know very well noticed the same tradeoff, except that he tends to like it over time.

Of course it does. I just commented Geddes statement from DIYaudio forum.

Have you tried supertweeter of any kind just to see if that would add some energy that high? Maybe that would return the resolution and make the sound more detailed...

@all

I have some questions about speaker placement to you guys...

Getting the speaker centers as close as possible may not be the right thing to do in the situation where one knows the xover frequency. Shouldn't driver centers be apart from each other regarding the xover frequency and wavelenght of it ???

If the only thing to do with spacing drivers from each other is to put them as close as you can, every major speaker manufacturer would do it because it would be very simple way of getting good sound.

 

[JoMoCo]

I have some questions about speaker placement to you guys...

Getting the speaker centers as close as possible may not be the right thing to do in the situation where one knows the xover frequency. Shouldn't driver centers be apart from each other regarding the xover frequency and wavelenght of it ???

If the only thing to do with spacing drivers from each other is to put them as close as you can, every major speaker manufacturer would do it because it would be very simple way of getting good sound.

Remember the focus has been primarily on two way, woofer tweeter. This has been discussed earlier in the thread, steering lobes(?) and the only way to integrate the tweeter w/ woofer is to measure the drivers with the crossover.

Avoid the wank...follow the Zilch plan...prototype, test, modify, test, finalize, test...:thmbsp:

Sound pressure is not the same as controlled directivity....:scratch2: