I am a full-range guy in desperate need of help re-constructing the original crossover of my "Hegeman Professionals Loudspeakers." They were originally designed as 3-way speakers. However, someone replaced the mids and tweeter with 2 full range drivers, making them FAST 2-ways. I plan on restoring them to their original design.
I drew up of the crossover in its current form (first attached schematic).
The lower crossover point is supposed to be 200Hz. The mids were designed to roll-off naturally to the tweeter at 8kHz. The "HF" control is supposed to adjust the over-all output of the mid range units and the tweeter. The "M.F." and "V.H.F." controls are supposed to adjust the mids and highs of the mid range units.
First question: does the schematic make sense? As drawn, does it accomplish the above?
I believe it does, but it looks odd to me. So I'd love your feedback.
If the schematic makes sense, here is the second part of my puzzle. I believe I have identified where the tweeter was originally connected (the red circled areas on the schematic and photo).
I drew this conclusion based on the fact that the crossover panel features an entirely unnecessary terminal strip (circled in red in the photo) correspond to the red circled points on the schematic, offering a positive and negative connection. I assume it was for the tweeter.
Second Question: Am I onto something? Would it make sense to add a tweeter and its crossover components to those points? I attached a second schematic showing what it would look like.
Good? Bad? Am I crazy? I am a crossover and schematic amateur and would appreciate your help!
Thank you for your help!!!
I drew up of the crossover in its current form (first attached schematic).
The lower crossover point is supposed to be 200Hz. The mids were designed to roll-off naturally to the tweeter at 8kHz. The "HF" control is supposed to adjust the over-all output of the mid range units and the tweeter. The "M.F." and "V.H.F." controls are supposed to adjust the mids and highs of the mid range units.
First question: does the schematic make sense? As drawn, does it accomplish the above?
I believe it does, but it looks odd to me. So I'd love your feedback.
If the schematic makes sense, here is the second part of my puzzle. I believe I have identified where the tweeter was originally connected (the red circled areas on the schematic and photo).
I drew this conclusion based on the fact that the crossover panel features an entirely unnecessary terminal strip (circled in red in the photo) correspond to the red circled points on the schematic, offering a positive and negative connection. I assume it was for the tweeter.
Second Question: Am I onto something? Would it make sense to add a tweeter and its crossover components to those points? I attached a second schematic showing what it would look like.
Good? Bad? Am I crazy? I am a crossover and schematic amateur and would appreciate your help!
Thank you for your help!!!
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I had the best will to answer your questions and then I realized, no, that guy won't appreciate anything coming from a guy like me. I didn't know this kind of conduct was allowed in this forum.
It's called hyperbole. You'd think the fact that I traced, drew, and modified a crossover circuit might have clued you in.
But thanks for taking the time to be snide. It's a small jesture, but, you know, people rarely take time for the little things like that now-a-days. So thank you.
There, I edited the post to make it clear I didn't pull off a miracle by drawing a schematic and designing a crossover without any knoweledge of either.
Now if someone wants to tell me my drawing is so terrible, or my crossover so amateurish, that It would seem I know nothing, then I value the criticism. I'm here to learn.
Now if someone wants to tell me my drawing is so terrible, or my crossover so amateurish, that It would seem I know nothing, then I value the criticism. I'm here to learn.
Flippin' 'eck! This is a bit of a detour into weird and wonderful loudspeakers! 
Good ol' Roger Russell has a section on Hegeman omni's which may distantly relate to what you have here...
Omnidirectional speakers
I suppose somebody, like me, could do a sim of your speaker if we knew enough about it. But ATM, I am clueless as to what this speaker looks like.
Hegeman's Eico HFS-2 8" plus tweet filter looks like it might actually work. The cone tweeter is a bit like the old Karlson Coupler, but he seems to stuff it in some way.
Good ol' Roger Russell has a section on Hegeman omni's which may distantly relate to what you have here...
Omnidirectional speakers
I suppose somebody, like me, could do a sim of your speaker if we knew enough about it. But ATM, I am clueless as to what this speaker looks like.
Hegeman's Eico HFS-2 8" plus tweet filter looks like it might actually work. The cone tweeter is a bit like the old Karlson Coupler, but he seems to stuff it in some way.
An externally hosted image should be here but it was not working when we last tested it.
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Flippin' 'eck! This is a bit of a detour into weird and wonderful loudspeakers!
Good ol' Roger Russell has a section on Hegeman omni's which may distantly relate to what you have here...
Omnidirectional speakers
I suppose somebody, like me, could do a sim of your speaker if we knew enough about it. But ATM, I am clueless as to what this speaker looks like.
Hegeman's Eico HFS-2 8" plus tweet filter looks like it might actually work. The cone tweeter is a bit like the old Karlson Coupler, but he seems to stuff it in some way.
I own a pair of EICO HFS-2 speakers as well! The speakers I'm working on -- the Hegeman Professionals -- were the "Concept speakers" that the HFS-2 is based on. They're double the size of the HFS-2. Check out the pics: the speakers, the tweeter, the mids.
And yes, since the Professionals use the exact same tweeter, mid-drivers, and crossover points, as the HFS-2. So I used the Tweeter crossover for the HFS-2 in my schematic.
Does my proposed circuit work? Anything seem odd?
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Yep. The "ice cream cone" is constructed of a sheet of aluminum foil bonded with nitrocellulose resin to a single sheet of tissue paper. It's attached directly to the voice coil. The center cone is a phase plug.
I thought so too, but check out the layout of the crossover board. There is a two terminal riser board that serves no purpose. And the wires that connect to it were routed out of their way to get there.
The black wire (a ground wire) connected to the terminal board ultimately connects to the speaker posts. Yet, Hegeman routed the wire past the posts and connected it to that terminal board before returning it back to the posts. Why do all that extra wiring unless there was a purpose?
Likewise, if the only purpose of the brown lamp cord connected to the terminal strip was to join "Pin 1" of the H.F. pot to "Pin 1" of the V.H.F. pot, why have from one pin, to the terminal post, then back to the other pin? Why not just connect the pins directly?
Also notice, the brown cable is tied (like the other wires that connect to the drivers) to indicate polarity. There must be a purpose to all that extra work. I think it was for the tweeter.
Does the circuit not work as its drawn (second schematic)?
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I ran a little sim of something resembling this speaker with 8 ohm drivers.
Flat Baffle, 2X 8", 2X 5" and a 1" cone tweeter.
Tells us something how it works electrically at least.
The tweeter connection is distinctly odd, but it works electrically. There is the germ of a second order mid filter in there. And a conventional bass filter.
As far as I can see, the tweeter connection does odd things to the mids, making them asymmetric in response. And too much cone breakup from the mids, unless they are very well behaved and damped.
Being a 1950's design, with lots of pots to twiddle, I don't suppose any setting actually worked very well!
Some potential there for a complete redesign, IMO. Along more modern lines.
Flat Baffle, 2X 8", 2X 5" and a 1" cone tweeter.
Tells us something how it works electrically at least.
The tweeter connection is distinctly odd, but it works electrically. There is the germ of a second order mid filter in there. And a conventional bass filter.
As far as I can see, the tweeter connection does odd things to the mids, making them asymmetric in response. And too much cone breakup from the mids, unless they are very well behaved and damped.
Being a 1950's design, with lots of pots to twiddle, I don't suppose any setting actually worked very well!
Some potential there for a complete redesign, IMO. Along more modern lines.
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Provided the drivers and enclosures are in good or better condition, and unless you could fine a well documented upgrade to the original design XO, I'd be inclined to take the restoration path.
Stewart and team were no dummies, and even an almost 60yr old design could be decades ahead of its time.
This looks like a hugely fun project .
Stewart and team were no dummies, and even an almost 60yr old design could be decades ahead of its time.
This looks like a hugely fun project .
I had a look at a conventional filter that really doesn't change things much. FWIW, the power response is similar too, though I haven't shown it.
I added a bit of impedance correction all round, which helps reduce cone breakup. I added the 3.3mH to give the mids an easier ride, free of bass. The third order tweeter filter is little different too.
Looking at it, I guess you might still hear some breakup from the mids at 7kHz. You'd usually cross a bit lower, say 3.5kHz. The layout could be easier to read, but it was a quick concept test.
I added a bit of impedance correction all round, which helps reduce cone breakup. I added the 3.3mH to give the mids an easier ride, free of bass. The third order tweeter filter is little different too.
Looking at it, I guess you might still hear some breakup from the mids at 7kHz. You'd usually cross a bit lower, say 3.5kHz. The layout could be easier to read, but it was a quick concept test.
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I'm a very big fan of Hegeman's. I own a pair of his HFS-2 speakers, several pairs of his H1a Omnidirectional 2-ways, and I also owned (just sold) a pair of his Citation X speakers. All of them are gorgeous sounding.
The speakers we're discussing are a pair of "Hegeman Professionals." They were Hegeman's favorite design. He never licensed it to anyone; and all orders for the speakers went through him, personally. Hegeman oversaw the construction of each cabinet and then hand wired everything. All the labels are hand written by Hegeman.
Hegeman gave this specific pair to his neighbor in New Jersey as a gift. After the neighbor passed, his wife put them up for sale. I bought them from her.
Unfortunately, at some point the wife blew the tweeter and midrange units. So the she had some "expert" fix them up. I'm trying to undo the garbage job he did.
The cabinets are absolutely mint. Not a scratch, not a dent, no fading. It's like they were kept in a time capsule. The original bass drivers -- modified by Hegeman -- are entirely intact, though the AlNiCo magnets clearly need a recharge. And I can re-create the midrange drivers and tweeter. I know what drivers they were based on, and I know exactly how Hegeman modified them.
All the crossover parts (except the crossover for the tweeter, which seems to be gone) are original and intact. I just have to figure out how to re-wire them as Hegeman intended.
The beauty of these speakers is, the entire mid/tweeter section is in an independent cabinet that slides out of the decorative frame that sits atop the bass section. So I can restore the original cabinet, and also build a new one using modern drivers and a modern crossover. I think, ultimately, that is the route I will take.
I feel like these are a piece of history, and I've never seen another pair. So I'll be sure to restore them to their original glory.
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Okay... So back to the crossover.
I'm not convinced that the odd way of wiring in the tweeter that I proposed is accurate. I have a new hypothesis, but it doesn't solve every mystery. Let me explain:
I'm proceeding based on the assumption that an audio master like Hegeman -- particularly one who valued simplicity -- would not design a crossover with unnecessary parts and useless wiring detours.
So here are the "extras" that need a purpose:
1.) Why did Hegeman take the speaker's ground wire past its exit, connect it to an otherwise unnecessary terminal board, then route it back to the exit? (See the circled area on the first crossover board pic)
Something must have connected to it. What was it? My guess is the tweeter, somehow. But I'm not sure how.
2.) What did the brown knotted wire (also circled) originally connect to? Closer examination reveals it didn't originally connect to that terminal board.
My guess for number three is that the brown knotted wire was originally meant for the second midrange unit. It is knotted to show polarity, like the other wires connected to the drivers, and it's position in the crossover just makes more sense when it is connected to a midrange unit (see second attached crossover).
That leaves the wires that are currently connected to the second midrange unit free (circled "?"). Would the Tweeter have connected there, in series with the midrange units? How would a crossover for it be configured if so?
Hegeman used this speaker's tweeter in the HFS-2 speakers as well. The crossover he used there is attached last.
I'm not convinced that the odd way of wiring in the tweeter that I proposed is accurate. I have a new hypothesis, but it doesn't solve every mystery. Let me explain:
I'm proceeding based on the assumption that an audio master like Hegeman -- particularly one who valued simplicity -- would not design a crossover with unnecessary parts and useless wiring detours.
So here are the "extras" that need a purpose:
1.) Why did Hegeman take the speaker's ground wire past its exit, connect it to an otherwise unnecessary terminal board, then route it back to the exit? (See the circled area on the first crossover board pic)
Something must have connected to it. What was it? My guess is the tweeter, somehow. But I'm not sure how.
2.) What did the brown knotted wire (also circled) originally connect to? Closer examination reveals it didn't originally connect to that terminal board.
My guess for number three is that the brown knotted wire was originally meant for the second midrange unit. It is knotted to show polarity, like the other wires connected to the drivers, and it's position in the crossover just makes more sense when it is connected to a midrange unit (see second attached crossover).
That leaves the wires that are currently connected to the second midrange unit free (circled "?"). Would the Tweeter have connected there, in series with the midrange units? How would a crossover for it be configured if so?
Hegeman used this speaker's tweeter in the HFS-2 speakers as well. The crossover he used there is attached last.
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The first HF attenuator seems to control overall level from the whole mid and tweeter section.
The rest of it, including the LC section, really doesn't do very much, as far as I can see. Those mids are running almost full range. Which was not uncommon then. The order of the mid elements shouldn't make any difference, just being in series.
It seems to make sense to wire the tweeter across the HF attenuator. Impedance goes a bit low, but whatever. Doesn't much matter if the tweeter filter grounds to the bass ground or the mid ground after the 72uF.
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What I meant, in terms of order, was that it makes more sense to wire a tweeter in after the two midrange drivers than in-between them (as I originally hypothesized), no?
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