Which crossover network is this?

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UncleMeat
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Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 1:14 pm

Could someone who knows ALS speaker design please tell me which version of crossover this is by looking at this photo?

Image

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radioeng2
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Re: Which crossover network is this?

Post by radioeng2 » Sun Oct 11, 2015 1:50 pm

Well...until the expert (Robert) shows up...you might chew on this one previously posted for the Platinum....

Image

From what I can see in the photo, not impossible to be it if the big resistor is there instead of the pair of 36 ohm on the drawing across the ribbon output. Hard to see enough detail in the photo to tell how close it is but at least some similarities.

Mark
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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 3:28 pm

I'll have to check my schematics - might have this one someplace, but it looks like it's just some early version of the Platinum upgrade kit, sold to upgrade the Originals with the newer 60" Platinum ribbons. Besides a new ribbon and crossover, that conversion involved some rewiring of the woofer arrangement. So what you have is essentially a customized version of the early Platinum crossover.

The one Mark posted has dual inputs. Does yours? What sort of symptoms are you having? Are both channels the same?

That very big resistor is the early-used equivalent of the four-in-parallel set of 25 watters (R1-R4) in the schematic. It's rated at 100 watts, and should test in the neighborhood of 4 ohms. If it opens, your highs would suffer a lot. They'd be absent entirely if C2 opens up, of course.

I suspect the biggest difference between this version and the one in the Plat schematic in the manual would be the value of the resistors that Mark mentioned - the ones right across the ribbon. Those are clearly there to balance the ribbon-to-woofer outputs, and matched with the older style woofers they stand to be different; in fact i believe they are absent entirely.

The four coils are likely all the same as the schematic. The one marked 74 would be L1, on the woofers. 75 appears to be L2, and 76 is l3. The little half-hidden one would be L4, and R3 and C4 are clearly visible next to it.
C1 is at the far left, with smaller C2 next to it. That leaves C3, and the parallel pair you have right over the middle coils seems to be that; what value Bob wanted there I don't know - you can probably read them - but I doubt it was 10 mf - he could buy that value easily as a single piece, right off the shelf. It's a bit of voicing.

Unless I missed something, that just leaves about a 5 watt resistor in the upper left corner. Check to see if it is in series with C2, for the same balancing purpose that R6 and 7 served later, when the woofers were quite different. So in this version, he maybe reduced the ribbon output a bit in a different way, right up front.

RobertR
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UncleMeat
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Re: Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 3:52 pm

Robert R wrote:I'll have to check my schematics - might have this one someplace, but it looks like it's just some early version of the Platinum upgrade kit, sold to upgrade the Originals with the newer 60" Platinum ribbons. Besides a new ribbon and crossover, that conversion involved some rewiring of the woofer arrangement. So what you have is essentially a customized version of the early Platinum crossover.

The one Mark posted has dual inputs. Does yours? What sort of symptoms are you having? Are both channels the same?
Thanks so much for your detailed reply!

No bi-amp option, single inputs, 60" ribbons. The symptoms are incredibly weak bass; without bass knob maxed and bass boost on on my C-1 there is little to no bass notes. In addition; the vocals are way out in front without bass and treble being increased; also the high notes have no brightness and background music is faint. As a comparison, my AL-III's have stronger bass with very little bass increase on my C-1; vocals are clear/bright but not way in front of the background notes. I was expecting similar vocals/highs but much better bass from these Amazings, so that's why I'm wondering about the crossover being correct and whether it should be re-capped or replaced with a newer version.

Thanks again for your help with this!

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radioeng2
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Re: Which crossover network is this?

Post by radioeng2 » Sun Oct 11, 2015 4:14 pm

Likely not but...the pic shows original honeycomb woofers. Do they move normally? I'm wondering about heavy handed treatment of the surrounds trying to keep them together causing poor movement?

A voltmeter may or may not be terribly accurate at lower bass frequencies...but I'd tend to want to run a lower sinewave at a modest level and with the VOM set to AC look at the voltage shown going into the crossover and then out of it. The comparison rather than the ultimate value being the issue.

Troubleshooting for me is divide and conquer. Or...narrowing down where the problem is and isn't.

Mark

PS...I'd (carefully) check the 450mfd cap (as shown above) or the equivalent for heat after running and see if it's showing sign of going short. And then there is the ol'....have you checked to make sure phase isn't flipped on one side...thing.
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UncleMeat
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Re: Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 4:40 pm

All the woofers move normally; the foam looks like it's in great shape for it's age, almost new looking aside from some 'crispy' glue, but the glue is still holding the foam outer flanges to the baskets so I'm not going to try and re-glue just yet. So far as I can tell there are no dead woofers, but I should remove the grills and verify this visually. Speakers are connected in-phase (+to+, -to-) to a TFM-45, but I'll double check the speaker connections to be sure.
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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 5:10 pm

If that masking tape is still on the front of your ribbons it would go a long way in explaining why they don't sound right...

RR
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radioeng2
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Re: Which crossover network is this?

Post by radioeng2 » Sun Oct 11, 2015 5:17 pm

Anybody recognize if that's an original surround? Those drivers are I think the highest Q driver every used in a speaker. Normal surround material might not be right if somebody redid them. Though, from Bob's story on them it sounded like the spider was a big part of the drivers success.

Mark
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Re: Which crossover network is this?

Post by Eddie » Sun Oct 11, 2015 7:01 pm

Here is a picture of the regular ALS Plats!
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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 7:18 pm

Looks pretty close to the schematic version Mark put up, though here they seem to have added yet another resistor in the series combo across the output; that would bring up the ribbon a bit. Maybe the tweak of the week. And C2, if it's the blue item lurking under some resistors, has gotten smaller.

Thanks Eddie!
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Re: Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 7:23 pm

Robert R wrote:If that masking tape is still on the front of your ribbons it would go a long way in explaining why they don't sound right...

RR
LOL yeah the tape was removed before playing them, I taped the ribbon boxes shut before removing them from the speaker frames, wrapping them in bubble wrap and a moving blanket for the 400 mile trip home. The speakers didn't sound quite right when I bought them, but we thought it was a room effect due to bass traps at both ends of the room (in an apartment building). When I set them up at home I put them in the same location as my AL-III's and connected to the same equipment. The AL-III's have better sound, and I know they have less bass than PMAT's ALS-Silvers. If anything I should be needing to turn the bass dial down, not way, way up.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 7:26 pm

We still have to figure out your bass situation - those things should give you bass from here to the Mexican Boarder. About now I'd want to just reassure myself that there really is bass coming out of the 45s - maybe some crazy problem upstream? Got a modest full-range speaker handy for a double check? Can't hurt to be sure, because the next steps get a bit more involved. Try both channels.
Also try both channels of the Originals pair. Are they about the same?

In an earlier post that got lost and never made it onto the forum I was suggesting that you test the woofers with a 9v battery, hooked right in where the power amp would normally hook in. All woofers should move together, and the opposite way if you reverse the battery. Once this test is passed, remove C1 (clip one lead, in such a way that you can solder it back together) and hook up your amp and try the bass without that big cap in there. It's just supposed to remove high frequency material. Without it you should have more highs from the woofers, but bass is the thing to listen for. If the bass is suddenly there, C1 has turned into something behaving more like a resistor than a capacitor, and needs replacement. There is only one other crossover part that affects the woofer output - inductor L1. If that's open, you would have no woofer action whatsoever. In the unlikely event it has shorted out, you'd have bass, but again with excessive highs from the woofers.

RR
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UncleMeat
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Re: Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 7:28 pm

radioeng2 wrote:Anybody recognize if that's an original surround? Those drivers are I think the highest Q driver every used in a speaker. Normal surround material might not be right if somebody redid them. Though, from Bob's story on them it sounded like the spider was a big part of the drivers success.

Mark
The foam is original. The glue is drying up where it attaches to the baskets (glue getting crispy, the foam is lifting a bit in some spots) but the foam is still supple/strong. If these were ever re-foamed it was a very long time ago, and I see no evidence that they were ever stripped of old foam.

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Re: Which crossover network is this?

Post by UncleMeat » Sun Oct 11, 2015 7:41 pm

I'm all but certain the TFM-45 is not the problem, it rocks the house with the AL-III's when turned up to 50%, but to be sure I will hook up some full range speakers and swap amps over to my TFM-35x to double check.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 7:45 pm

Let's hope it's not the electronics, unless it's something like a simple oversight. Speakers are a lot easier to troubleshoot than amps.
RR
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