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Thread: Big Reds!

  1. #31
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    Actually, I came across some indication that Audiotechniques made electronics crossovers for the Altec duplex speakers, so perhaps this is some of their work. I came across this:


    ELECTRONIC CROSSOVER
    Another control room goody that can be built with a state-variable filter is an electronic crossover for bi-amping, or for that subwoofer you've always wanted. Taking advantage of the simultaneous high-pass and low-pass outputs, we get precisely complimentary curves that fall at a rate of 12 dB. per octave. There has been a lot of talk lately about the advantages of using 18 dB. per octave slopes, so I contacted Altec, JBL, and Audiotechniques (Big Red monitors) for their recommendations. JBL was emphatic that 12 dB. per octave crossovers should be used with their components, and Audiotechniques also felt that this would create less ringing and phase shift than the 18 dB. types. On the other hand, Bob Davis explained that Altec offers crossovers in several formats, and as such he couldn't endorse any particular design.


    http://ethanwiner.com/spectrum.html

  2. #32
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    The appropriate plugs and cords came yesterday so I could connect the electronic crossover. It required two RCA -> XLR and six 1/4" -> RCA.

    I decided to first run this through an aux input on the Yamaha RX-Z9 at low volume to make sure that it was doing what it is supposed to do and document the results before putting it to the Super Reds.

    I was really disappointed when I plugged it in and what looks like a power light didn't come on, but there was no smoke. There is no "on" switch. So I checked the fuse, which was good and decided to proceed. I works, so maybe the LED is burned out/disconnected/or serves another purpose (e.g., clipping indicator).

    I ran the SACD/DVD player stereo outputs into the crossover inputs. I connected the crossover outputs to the Yamaha's aux input and set the Behringer 61-band RTA to monitor the "line level" circuit.

    I put on the pink noise track on the Stereophile Test Disk. First I connected the outputs from the auxiliary woofer channels and the results are included below. This is with the 50/75/150Hz boost circuit set to flat:


    This shows what is going to the 604E woofer section.



    And finally, this is what goes to the horn. A subsequent passive circuit between the power amp and horn (not shown here) allows for contouring.

  3. #33
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    Yesterday I was going though the provided speaker wires. Based on the connections, it would appear that they just ran the auxiliary woofer in parallel with the 604 woofer in a bi-amped mode, so whether or not they actually used this crossover is unknown. They had other electronic crossovers for sale.

  4. #34
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    I am getting a hum from the Soundcraftsmen amp that I think is caused by a difference in the chassis grounds to the crossover. I thought it was the amp, but apparently not. Anyways, I'll try a jumper between these two chassis. The crossover actually has the lugs for this provision.

    Meanwhile, even with some hum, these things sing beautifully! I can see/hear no damage to the components and they still look original.

  5. #35
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    I've been listening to the "Supers" and must say that the tri-amping and passive contouring on the horn makes all the difference in the world! I never figured that the 604E could go as high as well as it does and when the coutours are set flat, it doesn't. I don't even think that I will add an external tweeter to these.

    I did a recording and my wife thinks its too bright. I need to dial in the crossover after I figure out what's going on with a hum in the Soundcraftsmen that I'm not getting on the Yamaha or Marantz.

    https://youtu.be/vzYkXTGUgUY

  6. #36
    Senior Member Ian Mackenzie's Avatar
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    Quote Originally Posted by toddalin View Post
    Yesterday I was going though the provided speaker wires. Based on the connections, it would appear that they just ran the auxiliary woofer in parallel with the 604 woofer in a bi-amped mode, so whether or not they actually used this crossover is unknown. They had other electronic crossovers for sale.

    Seems like you are making steady progress on discovering how this system works.
    Those graphs look like the 4435 response curves (the 4435 also uses a helper woofer).
    Are you using 3 power amps to drive the helper woofer, 604E and horn at this stage?

    A tri amp crossover makes a lot of sense because a passive crossover on the helper woofer is a compromise.

    Ian

  7. #37
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    I have the Yamaha SACD feed into a Yamaha DSP-A1 Integrated home theater system (110WPC @8 ohms). The preamp outputs go to the electronic crossover. The HF goes back to the Yamaha to the amplifier inputs (jumpers removed). The Yamaha then feeds the HF contour networks and subsequently the horns.

    The 604 woofer and aux woofer outputs from the electronic crossover feed the four channels of the Soundcraftsmen 300x4 power amp. A 604 woofer and aux woofer are on each of the "stereo pairs" so as to "distribute the load equally side to side." The Soundcraftsmen is giving me a problem with a hum when connected to the crossover, though I've tried a cheater plug and grounding the chassis together to no avail. The Yamaha has no such hum and is dead silent.

    OK, this is the Super Big Reds doing the requisite "Tin Pan Alley."


    Not bad for a pair of 45-50 year old speakers that I paid $700, including the custom made electronic crossover, high frequency contouring units, and cables with dual bananas, delivered to my living room. When I recorded on Super Big Reds in the early 70's, this is what I remember.


    Again, no subs, eq, or processing is being used.

    https://youtu.be/OJaH9vz8y5E

  8. #38
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    Really loving these things! Imaging puts the JBLs to shame and they don't suffer from the "veil." Maybe room/seating placement plays a part in this, but I'm really lovin' what I hear even just using the level settings that were already set in the crossover (i.e., not accounting for their amp sensitivities relative to my amp sensitivities).

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