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Is this crazy? AVR bi-amp

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  • Is this crazy? AVR bi-amp

    I was looking at my Sony AVR . It allows 6 ohm speakers. It also has Speaker A, and Speaker B connections that can be played simultaneously. (They are connected in parallel.) So, I would conclude that I can run a 4 ohm speaker easily if I'm just using Speaker A connections. (Unless the manual is wrong.)

    I also see where I can select 5 channel stereo, and the same sound goes to the back speakers. What I'm considering is a a 3-way with the mid and tweeter on the front outputs, and the woofer on the rear output. I should be around 90dB on the mid/tweeter, and 87dB on the woofer. On the AVR, I can adjust "speaker level" by 3 dB to pad the mid and tweeter to match the woofer. The x-over might get "interesting", but that's OK. This could also work for a 2-way. I have some tweeters that I think are about 94dB. The AVR has decent power already. This setup would improve on that with the trade-off of additional complexity.

    Has anyone tried this? Is it worthwhile, or just silly for a small headroom improvement?
    Last edited by rpb; 11-13-2022, 05:07 PM.

  • #2
    People do this, but remember, you still just have one transformer and power supply. Delve into your AVR's power ratings, particularly two channels driven vs all channels driven.

    An electronic XO inserted via Pre Out/Main In might yield benefits. I'm really out of my depth here.

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    • #3
      Originally posted by djg View Post
      People do this, but remember, you still just have one transformer and power supply. Delve into your AVR's power ratings, particularly two channels driven vs all channels driven.

      An electronic XO inserted via Pre Out/Main In might yield benefits. I'm really out of my depth here.
      I'm mostly looking at this option because it will cost me very little. I've owned an active DCX2496 system before. It quit working, and I prefer passive. My preference is to have something a little bit simpler, but maybe with a slight sonic advantage over a normal connection to the Speaker A outputs. Padding a 94dB tweeter to 84dB this way, would pretty much eliminate any chance of clipping the tweeter. Using drivers I already own in a 3-way would have less advantage, but maybe enough to be worthwhile. Most are 89dB or less.

      Power ratings are pretty good even with all driven I think. Also, current to the mid, and tweeter would be much less than the woofer. especially without any resistors padding them down.

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      • #4
        Chances are the 6 ohm rating applies to either A or B alone and to A and B together, so 4 ohms is out no matter what. Most receivers of this sort have A+B series wired, to be sure that it won't see less than 6 ohms. Bi-amping is useful with an electronic crossover, but I can't see how one could be used with a 5.1 receiver.
        www.billfitzmaurice.com
        www.billfitzmaurice.info/forum

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        • #5
          My old AVR (maybe Denon) I think was 7.1. You could actually set bi-amp in the settings to the Rear Surrounds/"Assignable" speakers.

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          • #6
            Originally posted by billfitzmaurice View Post
            Chances are the 6 ohm rating applies to either A or B alone and to A and B together, so 4 ohms is out no matter what. Most receivers of this sort have A+B series wired, to be sure that it won't see less than 6 ohms. Bi-amping is useful with an electronic crossover, but I can't see how one could be used with a 5.1 receiver.
            The owners manual states that A&B are connected in parallel, and that both can be played simultaneously.
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            • #7
              Originally posted by a4eaudio View Post
              My old AVR (maybe Denon) I think was 7.1. You could actually set bi-amp in the settings to the Rear Surrounds/"Assignable" speakers.
              I saw that feature on a Yamaha AVR recently, and that's what got me thinking about this.

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              • #8
                The plot thickens! This AVR has pre-out for surrounds. I can use an external amp for 2 of the channels if I want. This would allow me to use an active low-pass between AVR and amp. I have one collecting dust in the closet. Moving away from simple though.

                It's 6 channels! I can tri-amp. Now it's getting interesting. I can use my 94dB tweeter, 87dB mid, and 88 dB woofer.

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                Last edited by rpb; 11-13-2022, 04:59 PM.

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                • #9
                  Power specs.

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                  • #10
                    I fiddled around with this setup last night. It was frustrating getting the AVR to do what I want, but t's just an issue going through the menu, and figuring out the AVR settings. I attempted a x-over using front, and surround amps built into the AVR. There's a chance that I damaged one of the surround channels. I don't think the AVR liked powering a cap, and tweeter. The output level of this channel was not consistent, almost like the AVR was making changes. It might be a bad wire connection. I did get signal out on the pre-out to my amp. I'm going to try it with the tweeter today, If nothing else, maybe I can determine if this AVR makes a good pre-amp for use with my amp.

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                    • #11
                      I was able to make a xo work, but......it seems that something is causing the tweeter level to drop by 6dB after a few sweeps. I'm not sure if it's a wiring issue, a tweeter issue, or AVR iscsue. Seems like AVR based on how precisely the drop is. I'm going to try this with the external amp next. The tweeter was padded 10dB with the AVR, and a little more with a series resistor.

                      This xo has a good reverse null, but still would need work. This xo was primarily for testing the AVR padding. The hump at 3k sounds like it looks.

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                      Last edited by rpb; 11-13-2022, 05:01 PM.

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                      • #12
                        Some notes, and thoughts.

                        The pre-outs are marked wrong. L is R, R is L.
                        The effect from padding the tweeter 10dB should be very significant.
                        This setup is only suitable for 2-ch stereo. No surround, or center channel.
                        This setup might be good if it is set up, and not fooled with. I change stuff all the time, so maybe that's an issue for me. It would be easy to foul things up.
                        I only listened to one speaker, cause I don't have a second that matches. I may try this down the road with a pair.
                        At this point, I would not encourage anyone to try this. It could be hazardous to your equipment. The impedance presented to the amps is different than a complete speaker. I'm not sure if the AVR likes that. My external amp sounded better powering the tweeter. (I think.) The xo is still not optimum. I might tweak some more, and see if I can smooth out the lower treble.​




                        Revised xo sounds better!




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                        Last edited by rpb; 11-13-2022, 09:29 PM.

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                        • #13

                          Reverse null.


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                          • #14
                            The AVR shouldn't care about just driving a cap and tweeter. It has no clue about what's hooked up, it only knows the impedance of the load. I've made my old Sony AVR do some pretty stupid stuff and it just keeps going.......

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                            • #15
                              Originally posted by devnull View Post
                              The AVR shouldn't care about just driving a cap and tweeter. It has no clue about what's hooked up, it only knows the impedance of the load. I've made my old Sony AVR do some pretty stupid stuff and it just keeps going.......
                              Yesterday, I saw a used Sony at a thrift store. I researched it a little, and found comments that it ran very hot, and had other problems . One comment was that it sometimes sounded muffled, and sometimes sounded fine. My amp may be dropping 6dB on occasion, and "sounding muffled". So, it may be the amp as much as connecting individual drivers. I'm not going to push my luck with this AVR any further. I like it, but it does get a little warm.. Hopefully, it will continue to work without issue.

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                              • HappyGene
                                HappyGene commented
                                Editing a comment
                                Hi rpb,

                                I've done something similar with amps in general and with Sony 100's thru 130's.

                                The tweeter as the main load on a driven leg works fine to me _provided_ the tweeter has the obligatory cap in series to at least protect it from transients (on/off) _and_ a zobel on it. I feel like this can be affected by the output stages, too.

                                If the cap is well below the xover point, that's fine; but you can also move it up towards the proposed xop to change phase somewhat and/or steepen the slope, if you can hear well enough to sense those changes. Mostly, I insert one I think "shouldn't interfere" and then swap polarity to see if I care.

                                The Sony's always seem to be warm, hot with 4 ohms so I mostly avoid it, but don't skip a beat and drive a zobeled singleton just fine

                                I've only seen once where a friend and I had to put a ~1.6 ohm ladder of non-inductive resistors in series with a horn tweeter because we couldn't easily make the right zobel to solve a narrow, but apparently well-trodden, dip to dcr. Maybe cavity or throat treatments might have lessened it, but...we were in a hurry...and it worked just fine...yeah.

                                You're a long standing member and if you already know this, I don't mean to imply otherwise, I just find it incredibly interesting to approach a system (especially when multi-amping) as a collection of independent elements instead of an interdependent network (which it really is.)

                                Eugene

                              • rpb
                                rpb commented
                                Editing a comment
                                For some reason, my sweeps were inconsistent. I like this avr overall. I hope it continues to work well. The local thrift stores often have really good deals on these older avrs. Maybe I'll try again with a different one.
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