- Great Work !
- It's a thing of beauty !
- And you've even left enough room above for a tweeter / should you decide to go that route
- Zilch, what's the internal cu volume of that L200 ?
- Great Work !
- It's a thing of beauty !
- And you've even left enough room above for a tweeter / should you decide to go that route
- Zilch, what's the internal cu volume of that L200 ?
Tweeters are what you shoot with shotguns.
Then you send your woofers out to retrieve them.
Hope this helps!
Well, I don't know how long Zilch will be able to resist the Widgets' influence / but mocking tweeters is a good start .Hope this helps!
( Hell, even I'm experimenting with tweeters )
Out here they call them mocking birds.Originally Posted by Earl K
...but mocking tweeters is a good start .
John
I earlier estimated the volume at 5.25 cu.ft., essentially the same as 4430. Gonna have to drop a plumb line to get the sloped front panel measured correctly. I'll do that today, 'cause I need to know the angle for other puposes, too (see below). It's a good design approach; despite low profile, they don't play to the knees.
Gettin' the waveguides with mid/high drivers into the cabinets made a big difference, too. Them sittin' on top of L200's for experimentation was a long way center-to-center-wise from the woofers. They now sound "integrated."
No tweeters, nope, nope. [045Be birdie would JUST fit, though....
Tried some 2404's a couple of pages back, and they didn't give me any more measurable extension than we already have with 2431's, just the ability to drive the VHF way out of proportion. I DO have a pair of 2435's I can put in there, tho, once JBL makes them "right."
Nobody's gonna bite on the time alignment thing, huh? I was surprised to see how shallow 2235H is once set up for side-by-side comparison. Just can't figure out where the "centers" are that are supposed to be aligned. If Mr. Widget measures them, we can get the answer, but I have to build up the final crossovers first.
One other thought: I may have been overly concerned about compromising the rigidity of the front baffle. The waveguide is itself quite thick and stiff, and easily supports the light-weight Neodymium driver as a cantilevered load. By the time I put 10 screws in each of them, and mounted the woofers, some of the lost baffle stiffness is restored. Gonna think again 'bout whether I HAVE to put bracing inside, but I'll likely do it anyway.
'Course, what with the sloped panel there, I'll have to buy a compound mitre saw and some nice kiln-dried lumber to do that correctly....
I'd suggest putting some of the known dimensions into a drawing .Nobody's gonna bite on the time alignment thing, huh? I was surprised to see how shallow 2235H is once set up for comparison.
- You do need to know the slope of that baffle .
- Relative locations of the component on the baffle
- Relative locations of each components' voice-coil ( approximate the mid point inside the gap )
- Need to know approx . convergence point of woofer & horn ( ie ; where you are likely to be sitting ,,,, sitting height and distance from boxes )
Yes :Just can't figure out where the "centers" are that are supposed to be aligned. If Mr. Widget measures them, we can get the answer, but I have to build up the final crossover first.
- find the acoustic centers for a few commonly used crossover frequencies on a few of the available, "obtainable" components / such as / the 2235, the 2431 on xxxx horn-wavequide / 2426,2418 on xxxx horn waveguide . You get the idea .
Wouldn't you want the *radiators* lined up, not the voice-coils? Think of it hypothetically - what if the diaphragm dome was something like 2" behind the voice coil? That's where the sound waves actually eminate from, not the center of the voice coils. I admit - the sloped/curved format of the LF speaker cone make for a somewhat confusing situation...
John
It's deceiving, because the sloped front baffle is recessed 4-5/8" behind the also sloping front edges.
Slope is -6.8817°
Internal volume is 4.9755 cu.ft.
Port is 4" dia. X 7.25" deep.
WinISD says I'm tuned to 25.7 Hz.
I must tell y'all, it was a pleasure taking the measurements with them playin' Shirley Horn so sweetly here....
Hi John
- Voice-coil alignments are a simplistic approach to the problem / I'll grant that .Wouldn't you want the *radiators* lined up, not the voice-coils?
- I believe it's quite a bit more complicated than just aligning all the sound producing membranes. The physical location that a person "assumes" should be point zero for the generation of a sound wave and where test equipment actually places that same "apparent" acoustic center / will just about always be two different locations in space .
- Only through the use of test equipment can a person expect to achieve reasonable alignment .
Once in a while I do think about these electromechanical paradoxes / but then my head begins to hurt .Think of it hypothetically - what if the diaphragm dome was something like 2" behind the voice coil?
I usually refer to the voice coils as the "acoustic center". Not sure how accurate a statement that is but just my 2 cents worth!
Ron
I can see now how the time alignment defines a horizontal plane in space where the distance from the "centers" (wherever they are) is the same, according also to the electrical phase relationship between the drivers.
Depending upon where I read, for 4430, that plane is tilted either 10 or 15 degrees upward from some point between the drivers.
If the drivers are aligned vertically, and perfectly in phase, that plane is perpendicular to the face of the baffle, i.e., on L200, it would be tilted 6.88° upward.
The closer the drivers are to each other, the less phase change occurs with vertical displacement from the plane of time alignment. If the "centers" are coincident, as in a perfect coaxial alignment, there is no change.
The absolute phase shift varies with wavelength, and is of most interest in the crossover region, where both drivers are playing the same frequencies. Outside of that region, it translates to group delay.
Well, that's my impression of it so far from reading here in the forum. The AES anthologies are on the way, and I'll hopefully be able to refine my own understanding.
Seems the answer is, "You gotta measure it."
Looking at the physical alignment of 2426H and 2235H in 4430's, there's a substantial element of BS involved in this, as well....
The drivers have a phase shift in the pass band generally so this will also vary with frequency.
I prefer the square wave test.
Ian
Now MY head hurts!I can see now how the time alignment defines a horizontal plane ... a substantial element of BS involved in this, as well....
John
Come down here and listen to these puppies.Now MY head hurts!
All will be well....
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