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Post by JKCashin on Aug 20, 2020 20:37:47 GMT -5
I have four XPA 1L, which as you may know are fully differential. I'm using three of them for L/C/R off of my XMC-2, and one is stored away.
My main towers are a pair of Polk audio RTI-A9's, and my centre is an Emotiva C2. All of these are capable of being bi-amplified.
I also have an XPA-10 with two unused high power modules, so I've been thinking of re-configuring, and I have a number of options.
Option 1 - use the four XPA-1L to bi-amp the towers, and mono or bi-amp the C2 off the XPA-10. This would mean I lose full differential path on my center.
Option 2a - use one XPA-1L for my center, and two XPA-1L for the bass half of my towers; running the mid/treble half of my towers off the XPA-10s.
Option 2a - similar to option 2a, still using one XPA-1L for my center, but swapping the bass and treble so the two XPA-1L run the mid/treble half of my towers; and the bass half of my towers off the XPA-10s.
The question is, is there even a measurable--let alone audible--difference between differential amplification and non-differential?
I am not even completely sure what my goal is here... I am mostly doing this for increased dynamics/headroom... but also because I have the extra channels of amplification so I may as well use them... right? But then... the XPA-1L, with 90,000mfd per channel should have plenty of dynamics on it's own... so maybe I should just leave well enough alone? My headroom gains might simply be marginal.
There is also the issue of impedance... as you probably know impedance is not the same as resistance... it varies by frequency. If it were like resistance, then if the speakers with the bars on the posts presents 8ohm, it would mean I would essentially be creating two 16ohm loads (since they are technically in parallel) but my understanding is that the impedance graph for the speakers with the strap in place will not be the same as the two impedance graphs for the low/high. I have a 100Mhz oscilloscope so I am wondering if I could use it with a signal generator to measure impedance with some DIY interface.... anyone?
So many questions.... so many possibilities.
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Post by JKCashin on Aug 20, 2020 20:42:33 GMT -5
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Post by JKCashin on Aug 20, 2020 21:08:00 GMT -5
Watching some videos on this now... seems I might want to use less power on the tweeter side... your thoughts?
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Post by garbulky on Aug 20, 2020 21:22:12 GMT -5
I have four XPA 1L, which as you may know are fully differential. I'm using three of them for L/C/R off of my XMC-2, and one is stored away. My main towers are a pair of Polk audio RTI-A9's, and my centre is an Emotiva C2. All of these are capable of being bi-amplified. I also have an XPA-10 with two unused high power modules, so I've been thinking of re-configuring, and I have a number of options. Option 1 - use the four XPA-1L to bi-amp the towers, and mono or bi-amp the C2 off the XPA-10. This would mean I lose full differential path on my center. Option 2a - use one XPA-1L for my center, and two XPA-1L for the bass half of my towers; running the mid/treble half of my towers off the XPA-10s. Option 2a - similar to option 2a, still using one XPA-1L for my center, but swapping the bass and treble so the two XPA-1L run the mid/treble half of my towers; and the bass half of my towers off the XPA-10s. The question is, is there even a measurable--let alone audible--difference between differential amplification and non-differential? I am not even completely sure what my goal is here... I am mostly doing this for increased dynamics/headroom... but also because I have the extra channels of amplification so I may as well use them... right? But then... the XPA-1L, with 90,000mfd per channel should have plenty of dynamics on it's own... so maybe I should just leave well enough alone? My headroom gains might simply be marginal. There is also the issue of impedance... as you probably know impedance is not the same as resistance... it varies by frequency. If it were like resistance, then if the speakers with the bars on the posts presents 8ohm, it would mean I would essentially be creating two 16ohm loads (since they are technically in parallel) but my understanding is that the impedance graph for the speakers with the strap in place will not be the same as the two impedance graphs for the low/high. I have a 100Mhz oscilloscope so I am wondering if I could use it with a signal generator to measure impedance with some DIY interface.... anyone? So many questions.... so many possibilities. I’ve used four xpa1l in bi amp config. The upgrade you are looking for is to get two xpa 1 gen 2. Which is what I have. |
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Post by Boomzilla on Aug 21, 2020 2:48:52 GMT -5
Unbalanced vs. balanced? In my system (fairly complex, constantly changing, and a rats' nest of wiring), the difference between the two is hum. With unbalanced connectors, some hum is almost ALWAYS audible. With balanced ones, never. But my system is NOT a typical system. And when I simplify; for example, run my Emotiva TA-100 (integrated DAC-preamp-amp) instead of separate DAC, preamp, equalizer, crossover, and power amps, then the unbalanced system does NOT hum. So my advice to you would be: If you can get hum-free performance with unbalanced circuitry & interconnects, then don't worry - be happy! But if you DO have hum problems, and they're not conveniently solvable by routing interconnects away from power wires & transformers, then balanced is a good way to reduce hum. By the bye - I also agree with garbulky that the XPA-1 (generation one, two, or three) are a HUGE upgrade from the XPA-1L amplifiers. ( HUGE!) I'd also mention that if you're using a stereo amplifier to "vertically-bi-amplify" a pair of speakers (one channel of the stereo amp drives the woofers, the other channel drives the midrange/tweeters), then you need not worry about "wasting" current on the treble, nor worry about "starving" the bass for current. Why? Because both channels typically run off a common power supply. Whatever amperage capability is not being used for the treble channel is available to the other channel for bass. This "advantage" disappears if you're using two separate amplifiers (such as two mono XPA-1Ls) to bi-amplify the speakers. Cordially - Boomzilla |
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Post by repeetavx on Aug 21, 2020 11:17:35 GMT -5
I am a strong proponent of passive bi-amping, but I believe that you must be careful how you do it.
Early proponents of bi-amping experimented with your number two option, which is called horizontal bi-amping. Most of us have concluded that this causes more problems than it fixes. Try it if you like, that is why this is called a hobby.
My recommendation is that you try option 1. Vertical passive bi-amping. I believe this brings out the most nuances in the stereo field. Remember in stereo, you are creating a phantom sound stage which is dependent on both sides matching perfectly. As opposed to a surround sound channel, which is designed to anchor a sound at the speaker's position .
Since your center speaker is 2 db more efficient than your stereo pair, you can use a lower power amplifier to achieve the same sound power level.
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Post by 405x5 on Aug 21, 2020 12:00:15 GMT -5
“Unbalanced vs. balanced? In my system (fairly complex, constantly changing, and a rats' nest of wiring), the difference between the two is hum. With unbalanced connectors, some hum is almost ALWAYS audible. With balanced ones, never.” Not true. Maybe, it’s time to get rid of the “rats nest”! |
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Post by creimes on Aug 21, 2020 12:44:31 GMT -5
Hey Jamie,
I don't want to sound like the party pooper here but I think you are over thinking it, if anything bi-amping your mains could be an option, that is if you think you are needing more power for the A9's, if it was me I would just run it as is and sell the extra 1L or keep it as a backup in case one of them needs service in the time you own it.
Chad
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Post by JKCashin on Aug 21, 2020 16:15:49 GMT -5
I’ve used four xpa1l in bi amp config. The upgrade you are looking for is to get two xpa 1 gen 2. Which is what I have. Eventually..... will want to upgrade my mains first |
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Post by JKCashin on Aug 21, 2020 16:18:43 GMT -5
Unbalanced vs. balanced? In my system (fairly complex, constantly changing, and a rats' nest of wiring), the difference between the two is hum. With unbalanced connectors, some hum is almost ALWAYS audible. With balanced ones, never. My entire system save for my subs is balanced |
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Post by JKCashin on Aug 21, 2020 16:19:52 GMT -5
Hey Jamie, I don't want to sound like the party pooper here but I think you are over thinking it, if anything bi-amping your mains could be an option, that is if you think you are needing more power for the A9's, if it was me I would just run it as is and sell the extra 1L or keep it as a backup in case one of them needs service in the time you own it. Chad It's a matter of experimentation, for the hobby really. I don't "need" to do this... just wondering if there's any perceivable benefit that would justify doing the experiment. |
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