Zilch's AK Design Collaborative - Econowave Speaker

[GordonW]

The Fs of the driver is 44 Hz, and WinISD shows a decent plot with the box tuned to 50 Hz. Tuning it any lower (40 Hz, for example) doesn't seem to lower the F3 , but does start the roll off at a higher frequency. The surrounds are extremely stiff treated cloth type, which may be partly responsible for it's Fs being so high.

Would changing the surrounds to foam lower the Fs any? Would increasing the mass of the cone? Would doing either of these things lower the F3, or would doing so change the other parameters such that it would become a throw away?

A pair of the 2 cubic foot cabinets from Parts Express will be here today, and the B & C's are the only 12 inch drivers I have on hand. The cost was low enough that I may try to modify them somewhat before using them, if there seems to be any chance of success. Am I plotting to shoot myself in the foot?

Yes, changing the surround will lower the resonant frequency... which may not lower the f3 much, but it should act to make the very bottom of the LF curve below resonance, go a bit lower before dropping to the same level.

And yes... adding some mass will increase low end extension. Before doing that permanently, you will need to be able to measure before and after with something like a Woofer Tester and then compare the results in a modeling program; you just want to make sure you aren't about to cause a horribly bumpy response in-box.

BTW: Changing out the surrounds for foam will have a couple of effects:

First off, resonance will be at a lower frequency (naturally).

Secondly, though... Qts will go DOWN. This will offset some of the LF extending effects of lower Fs.

What I'd do: First, change the surrounds. Then measure, and model. Then try adding some mass (temporarily)... then re-measure. You just want to be able to get a flat response in the enclosure... just make sure by adding mass, that you don't get to a point where you can't do that anymore...

As for where to add mass- I find you want to get it as close to the voice coil as possible. I'd be tempted to remove the dust cap, and put it in at the cone/voice coil joint... then put the dust cap back on...

Regards,
Gordon.

 

[von.ah]

sorry if this is too off-topic, but I can't find the speaker measurement methods threads...

Does anyone know if musician's friend or guitar center-like places will loan out an RTA system, a-la the deq2496 + mic? I want to try out such a setup to measure my main system, but i don't know that I'll be able to utilize it long-term...

Any ideas on pro-sound temporary measurement setups?
Thanks!

 

[Zilch]

Any ideas on pro-sound temporary measurement setups?

Doubtful, but they may rent you a setup and credit that toward subsequent purchase. There's a hand-held device, I forget the manufacturer, that may be a suitable candidate.

Pro sound outfits will likely charge more to rent something sophisticated than an entry-level system would cost, and there's a substantial learning curve.

[They're hip to "borrowers...." :tongue: ]

 

[skywave-rider]

I just saw that Meyer announced a "studio" version of their Acheron cinema 2 way speaker. The guide reminds me of the QSC. (Just lookin' at pictures ofc.)

http://www.meyersound.com/products/cinema_experience/acheron_studio/index.php
Cool looking.

 

[devoid]

Any thoughts on my new not a wave radio? Good or bad? I just bolted one of the dh1a's to it but don't feel to compelled to connect it to one of my big amps to see what happens. It's progress though, I guess you could call it.

 

[devoid]

I have to agree with one thing I've read here on AK. And that's when you get serious into this hobby hearing protection, hardhats and steal toed boots are needed.

Ok, so, holly coherence batman! The bandwidth covered by these things is great as they get all the mids. None of that multi cone driver smear here. Timing, I guess you could call it is spot on. A very "locked in" like. So I think I see a path here. Now they are peaky in the mids but that's why EV had an equalizer for them. So I'll build one or buy one or get that fancy Behringer parametric. There soft up top but I have a pair of Heil's that should help there. My test run was with a HK 770 amp. I'd like to go tubes or class A MOSFET for power. I have a HK 500 integrated that needs rebuilding. I may convert it to power only. Got a little Maggy here too. That should get my top end singing. I have these crossed at the moment at 350hz, a bit low. Still got those big JBL and Peavey 15's from the PA cabs. Well still got the cabs too so that should start me on the bottom. DH200 or dual Rotel's...

I can put it this way too. These giant ass horns make my HPM-100's sound small. I see them pullinh HT duty this winter. I've got the next five days off. Hope I don't hurt myself.

 

[skywave-rider]

You may need one of these, too:

 

[devoid]

hehe

Not concerning my safety but rather my new voice coils, I discovered just how far down these horns go. Down to about 120hz. I believe reading somewhere that the drivers are speced down to 500. But around 150 to 180 I was thinking of crossing them over to the HPM-100's doing woofer duty only. That should get me going a little faster. Now I just have to rearrange the living room.

That lower f cuttoff; is that primarily a function of horn length, I'm thinking? And is it safe to operate the DH1A drivers down to 100hz. Obviously they won't be seeing much power in my small space but I don't want to hurt them. Planning on using a 130wpc Rotel tomorrow.

 

[Russellc]

You know the primary variables, Russell, and the horizontal displacement of the acoustic centers is primary.

In my case, the QSCs are sticking out forward of the woofs as shown in the pic, and the polarity is eWave standard after inverting the JBL woofer to industry standard, i.e., in absolute terms, the tweeter is connected inverse polarity.

At first I had them just setting on top like Econowave and was concerned
when I saw how much further the HF was from the woofer b/c of this QSC waveguides larger height.

I now have it in Zilch mode, closer for sure!:thmbsp:

russellc

 

[Russellc]

You know the primary variables, Russell, and the horizontal displacement of the acoustic centers is primary.

In my case, the QSCs are sticking out forward of the woofs as shown in the pic, and the polarity is eWave standard after inverting the JBL woofer to industry standard, i.e., in absolute terms, the tweeter is connected inverse polarity:

So if I'm understanding all this correctly, your woofers are also "Black causes Pos movement forward" but since we have them ( the QSC and DE 250) in the forward position relative to the woofer, we hook pos to red on the woof, and invert per schematic on the HF?

Perhaps this explains a perceived slight loss of bass power since I've installed this QSC guide DE 250 combo? Or do I need to give my ears a rest?

Thanks for all your work on this Zilch, while I'm still a babe in the woods with all this, the past year or so has been a real learning experience, and you and Jack are mainly responsible for it! I'm insanely close to becoming a measuring curve junkie as well!:thmbsp:

Russellc

 

[jackgiff]

Yes, changing the surround will lower the resonant frequency... which may not lower the f3 much, but it should act to make the very bottom of the LF curve below resonance, go a bit lower before dropping to the same level.

And yes... adding some mass will increase low end extension. Before doing that permanently, you will need to be able to measure before and after with something like a Woofer Tester and then compare the results in a modeling program; you just want to make sure you aren't about to cause a horribly bumpy response in-box.

BTW: Changing out the surrounds for foam will have a couple of effects:

First off, resonance will be at a lower frequency (naturally).

Secondly, though... Qts will go DOWN. This will offset some of the LF extending effects of lower Fs.

What I'd do: First, change the surrounds. Then measure, and model. Then try adding some mass (temporarily)... then re-measure. You just want to be able to get a flat response in the enclosure... just make sure by adding mass, that you don't get to a point where you can't do that anymore...

As for where to add mass- I find you want to get it as close to the voice coil as possible. I'd be tempted to remove the dust cap, and put it in at the cone/voice coil joint... then put the dust cap back on...

Regards,
Gordon.

Thanks for the great info, Gordon. Sounds like some minor alterations might take place with these B & C woofers before they are used. I really hate to mess with someone else's design, but would like just a teeny bit lower bass from them. And of course, the spider is extremely stiff as well. Maybe just going with another woofer is the best answer.

I will probably try them as is first, and then decide whether modifying or replacing them is the best alternative. They did sound quite nice in my test cabinet, but just knowing what the WinISD plot looks like sort of sticks in my mind.

 

[Zilch]

So if I'm understanding all this correctly, your woofers are also "Black causes Pos movement forward" but since we have them ( the QSC and DE 250) in the forward position relative to the woofer, we hook pos to red on the woof, and invert per schematic on the HF?

Our standard approach to dealing with inverse polarity JBL woofers is to invert them to EIA standard at the input terminals, in this case, those on the utility bass bins.

That done, the DE-250s on QSC waveguides placed as shown are connected per the standard eWave schematic, i.e., inverted.... :yes:

 

[Russellc]

Our standard approach to dealing with inverse polarity JBL woofers is to invert them to EIA standard at the input terminals, in this case, those on the utility bass bins.

That done, the DE-250s on QSC waveguides placed as shown are connected per the standard eWave schematic, i.e., inverted.... :yes:

Then if I'm understanding this, I've got it right with Pos LP from crossover goes to black terminal on bass box, Neg low pass from crossover goes to red on bass box. Tweeter is inverted, red from crossover to neg on HF driver, black from crossover to pos on the HF driver. (assuming battery pos to pos crossover input causes forward motion of the cone.)

sorry for the confusion, for a minute there I thought you meant that the postion of the horn being a little further forward would necessitate red to red, and black to black...........

Russellc

 

[Zilch]

If red in both cases means the lead connected through the crossover components to the red crossover input, yes.

That's not what the schematic shows as the HF polarity, tho....

 

[Russellc]

I see now. Although it was clearly posted several times, I failed
to grasp the part about correcting for the woofer INTERNALLY so
that the box now Externally would be standard convention. Just a little
dense here for some reason.:stupid::drunk::stupid:

Russellc

 

[Zilch]

Well, no, I don't correct the JBL box internally; I hook the crossover red to black externally to make it standard polarity, after first verifying that it is indeed inverse.... :thmbsp:

 

[skywave-rider]

Will have PE knockdown trapezoidal cabs next week like several others here. If porting, since there's no room on the front -- I think -- what do u guys recommend? I know that theoretically it does not matter where the hole goes. But practically speaking, I think the sides or top might be best because of boundary, placement and clearance issues.

 

[djnagle]

Geez, I must be turning into a chicken ****. I can't seem to get up the nerve to refoam my American Monitors for my next eWave project. Is it really that difficult to get it right? Can I scrape it all off if I get it wrong?

 

[djnagle]

Will have PE knockdown trapezoidal cabs next week like several others here. If porting, since there's no room on the front -- I think -- what do u guys recommend? I know that theoretically it does not matter where the hole goes. But practically speaking, I think the sides or top might be best because of boundary, placement and clearance issues.

Can't you raise up the wave guide, then raise up the woof to butt up to the guide, then go with two small ports on the bottom corners? I think that cab is a great deal.... thanks again Ross.

 

[Zilch]

Will have PE knockdown trapezoidal cabs next week like several others here. If porting, since there's no room on the front -- I think -- what do u guys recommend? I know that theoretically it does not matter where the hole goes. But practically speaking, I think the sides or top might be best because of boundary, placement and clearance issues.

If it's 123A's, I'd try them closed box first, the equivalent of L100+ plugged. I should model these in BB6P to determine the actual internal volume, variously stated to be somewhere between 1.5 and 2.0 cuft. I believe Gordon's suggesting that closed may be the best option for the DC-300, as well. Another perspective, from Geddes -- everything is closed box and assumes subs to make the bass, instead. For HT, at least, that makes sense, too.

Rear porting's probably less of an issue than we suppose; if we're using boundary reinforcement for the bass, we may want them closed, anyway.

Another, perhaps better, option is bottom - put 'em on stubby legs or spikes, or boards across the front and rear with the sides open. I don't know how the calcs work out with that, but I can't imagine much distance from the surface is required. That'd be a fun experiment, actually, watching the impedance peak move as the height is varied.

Bottom porting would certainly work with stands like these:

http://www.audiokarma.org/forums/showthread.php?t=248112

Can't you raise up the wave guide, then raise up the woof to butt up to the guide, then go with two small ports on the bottom corners? I think that cab is a great deal.... thanks again Ross.

There's plenty of room for front ports using the standard eWaveguide; it's the larger QSC presently under consideration here.... :yes: