Which crossover network is this?

Carver Speaker Discussions and Questions
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Robert R
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Re: Which crossover network is this?

Post by Robert R » Sun Oct 11, 2015 8:07 pm

BTW, I never said I thought the 45 was the problem - just possibly 'something upstream'. Preamp, program source, interconnects, any processors - whatever. Best not to inject a different amp - fewer variables is better. If the 45 as now hooked up blasts away normally with your IIIs, that's fine - no problem there. Now it's either the crossover (all of two parts), the drivers themselves, or the way they are wired.

One other odd idea is forming in my feeble old brain, but it can wait until you test C1.

RR
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UncleMeat
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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 3:54 am

Thanks RR it's always good to be certain that basic things like sources, amps and connections are working properly. The only change that was made was swapping the AL-III's for the Amazings. Checked connections at the back of the speakers they are good and in correct phase. Amp is unchanged, sources are my Harman Kardon ST-7 TT, and Carver 490t CD player. Both sources present exhibit the same problem when playing on the Amazings, so I'm pretty sure it's not the source. The only other possibility is a pre-amp or amp problem, I could switch over to my C-1000A as a pre-amp/phono to test.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 5:38 am

It seems that your electronics are working normally - just wanted to be sure before exploratory surgery.

Working on just one channel at a time is probably best from here on. Hopefully whatever is wrong with one will turn out the be the problem with the other, but that's not a certainty.

If you clip out that largest NP electrolytic in one channel and then run just that speaker, what if any changes do you hear in the bass?

BTW, the next step may involve using an ohmmeter - I'm assuming you have a half-decent one of these. If not, you should get one.

RR
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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 10:00 am

Yes I have a Tektronix DMM; it should be good enough. It's not a Fluke, probably just a basic DMM with the Tek logo. I'll disconnect the cap on one speaker and let you know what I hear.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 10:20 am

If you hear a lot of bass it means that big cap is shot - has become a resistor.
If no improvement, or just a noticeable increase in higher frequencies from the woofers, the next step is to unhook your amp and measure the DC resistance across the speaker's input terminals. Leave C1 unhooked for now.

RR
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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 10:34 am

On the right speaker I clipped the C1 cap; but sadly there is no change to the bass note. Less energy is going into the ribbon but the bass note is still not there.

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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 10:39 am

Left speaker says 2 Ohms, Right speaker (clipped C-1) says 3.8 Ohms.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 11:17 am

3.8 seems reasonable, figuring around 2.7 for the woofer array, another half-ohm for the coil, and a bit more for the connecting wires. A bit high, perhaps, but your coil value is one of our unknowns - may not be the one used in the Plats, which had, of course, entirely different woofers.

Now let's isolate the woofers from the ribbons. Simply clip one end of C2, just as you did C1, and try her again. This time you should have zero output from the ribbon. Any bass response from the woofers yet?
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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 11:30 am

Wait, is 2 Ohms reasonable for the left speaker that does not have a clipped C1?

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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 11:38 am

No, no bass, there is a bit of midrange coming out of the right speaker but still little to no bass.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 11:51 am

Yeah, well, I was just looking at one at a time. On that other one, the first obvious move would be to clip C1 there, as well, and see what that does for your reading. Those big bipolar caps are subject to breakdown, for sure. But right now I'm trying to figure out why your woofers won't woof. With C1 gone and C2 gone the only thing between the woofer array and your amp is L1, which you could jumper, eliminating its effect. Then you would be running the 4 drivers unencumbered. If they still have no appreciable bass response I'd have to conclude they are shot, somehow. Maybe voice coils seriously burnt, or something. Unless the permanent magnets have disappeared, or maybe turned into lemon drops.

You could test just one driver, individually - say the top one, since just one wire to remove. Hooked directly to an amplifier putting out some low frequencies it should demonstrate some serious cone excursion.

RR
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radioeng2
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Re: Which crossover network is this?

Post by radioeng2 » Mon Oct 12, 2015 12:09 pm

The original picture to me sort of looked like less than inspiring soldering. It made me wonder if the speaker has a past "rework". If this was purchased as is, then maybe that was a big part of selling it. A redo gone sideways. Maybe checking for correct wiring to the drivers themselves might be in order. Also, confirming the polarity and function of each driver with a 1.5v cell.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 12:21 pm

Mark - I have suggested a battery check several times; hopefully he did it. The overall DC resistance is, at least, in the ballpark.

I have seen Carver woofers fried to the point where they would hardly move, but the voice coils were still intact, electrically. They were not free moving, however - they were obviously scraping the pole piece. But we discussed that, too, and he says these are free-moving, not rubbing.

](*,)

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Re: Which crossover network is this?

Post by UncleMeat » Mon Oct 12, 2015 12:34 pm

I jumpered L-1, still weak bass. I tested the resistance of the woofer array it registers 4 Ohms which should be correct. In order to get the woofers to visibly respond to the bass notes I still have to crank the bass dial up and turn the low freq boost on. When I crank the bass settings I do get decent bass but not earth shattering. They do seem like they have a bit more bass note than before (hard to tell with the speaker running full range), but not a huge amount of bass. When the C-1 is set flat it has very little bass sound but of it's also running full range, so its hard to say what it should sound like.

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Robert R
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Re: Which crossover network is this?

Post by Robert R » Mon Oct 12, 2015 12:44 pm

Actually, the woofer array should measure just what each individual woofer should measure: 2.7 ohms, according to the manual. You need to check them one at a time, both for resistance and response. A 9v cell should make each one individually jump in or out quite a ways. Plus to plus, they should jump forward; reverse it and they jump the other way, same distance.

RR
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