Years ago I promised myself to post this at Audioholics
first before I was ever to disclose it in any other forum. Since I am about to do this to help a fellow at the Audio Asylum, I had to come here first. It has to be here first because it was Gene DellaSala and Clint DeBoer who went beyond the mere obvious. They discovered and revealed an option for bi-amping [passive at speaker-level] some earlier Denon AVRs which lacked such ability from factory. [I have not posted enough times in this forum to be allowed to include links here. Look up Audioholics' review of the Denon AVR 3805 in 2004. See the bi-amping section in the page "First Impressions" towards the bottom.]
This is about a
hybrid bi-amping xover option that can allow for a set of the speaker drivers (in my case the tweeters) to be
driven DIRECTLY from the Denon power amps. In the process, the extra purity of the tweeter signal allowed me get a much improved, harmonics-rich and extended treble, as delivered by my SACDs and other hi-rez sources.
The posting is more for the benefit of the DIY-techies gang. Yet, it is not unduly complex. In fact it's so easy...a caveman...or cavelady
could do it [with common sense caution and some coaching]. It works with any Denon AVR that I have tried it on so far: AVR-2106, AVR-3105, AVR-3106, AVR 4306, AVR-5308CI; and probably any Denon in the AVR series. I've kept this as a secret trick until I made sure that it was safe on a variety of Denon models.
Four years ago, while buying a used AVR-3805, I came across the Audioholics review. I was not intending to bi-amp at speaker-level. Instead, I had plans to build an active electronic xover for my Magnepan MMGs. Yet, it never hurts to do SOME kind of bi-amping in the meantime. Speaker-level bi-amping could be a placeholder while I designed the "real thing". Thus, the review input was welcome and appreciated.
However, based on what Gene and Clint did, I developed the hybrid variation that served me extremely well for quite a while. This is because the Denon AVR allowed me to mix the bottom part of a normal xover (or "passive at speaker level") with the top part of a PLLXO* (or passive line-level xover) filter.
I can expand further if there are any inquries but here's an outline of what I did:
1. The mid-bass panel in each MMG remained driven at speaker-level by the normal power amp channels (Denon mains) going to the
low pass of the regular xover. This is the ordinary connection.
2. The tweeters were disconnected from the normal speaker-level xover.
3. Along the lines of what the review proposes but with a variation or two, I took the L/R signal from the pre-amp or "pre-out" and:
-- instead of sending it directly to a spare analog input, FIRST I inserted it into a high pass filter. [This can be as basic as just 1 capacitor chosen for a tuned 1st order slope on the tweeter signal.]
-- the output from this filter was then fed to the spare analog input to be used. In my case, it was the "DBS".
-- In the receiver's setup, the "DBS" signal was assigned to Zone3
-- I hooked up the tweeter drivers directly to the speaker outputs of Zone3 (Caution - this is only an outline of the steps. If you lack experience on the subject PLEASE ask for details....don't blow good tweeters )
- On playback, the volume of the tweeters can be adjusted in Zone3 for a level match with the woofer (mid/bass panel in my case). In reality, I use REW and measure with a calibrated mic.
I chose to benefit the tweeters with the direct signal because that was my priority. However, the same concept can drive a woofer directly for improved control (and it shows). Then, the tweeter gets the signal via the mains, filtered at the speaker's xover.
I hope to have included enough information for some of you figure out the rest by yourselves. In any case, I am perfectly willing to help everyone I can. To be sure, there are downsides like the loss of surround channels and automatic EQ calibration. There are also some risks if you are not the careful type, particularly it the tweeter is the one driven directly.
That said, for some people it may be the key to a truly affordable enhanced sound. This method is something that audiophiles on a beer budget, like me, may find most appealing.
* A sketchy definition of typical crossovers (or xovers):
1. What we all know is the
Speaker-level xover aka "passive" (though in reality they should be called "passive at speaker level"). This is the common crossover. One power amplifier channel enters the speaker. The frequencies are then divided by the passive filters in this rather bulky xover device. So, there is ONE amplifier channel for ALL the drivers in that speaker.
1b. The xover above can be mechanically split into two or more parts to do bi-amping (or multi-amping). In fact, several speaker manufacturers include such an option. However, each part
still includes the filter for the speaker driver it handles. For example, many receivers include the ability to dedicate some of their power amps for bi-amping in this manner. It "ain't" the best way to multi-amp because the filters still are right before each speaker driver. But, hey, it still is better than nothin'!
2. The
Line-level crossovers (two variants) are less known. They divide the frequencies much earlier, usually as they leave the pre-amplifier. After this crossover, the divided frequencies ranges go each to one of several power amplifier channels. For example, in a stereo two-way speaker system (tweeter/woofer), four power amplifier channels are needed.
Each of these power amplifier are connected DIRECTLY to each of the respective drivers. With properly tuned values, a direct signal to the drivers, from each power amp, just can't be beat.
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Variant #1 is the "Active" line-level xover, aka "electronic crossover". The main difference from variant #2 is that this crossover is made of some components that require a dedicated power source. It is called "active" because it uses discreet devices, such a transistors and opamps. It is expected to have either "no insertion loss" or to provide some output level gain.
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Variant #2 is the passive line-level xover aka PLLXO. Even those who know about it tend to call it "active" because it is easier to lump them together on the basis of their function:
"line-level filtering". However, a full PLLXO is totally made of passive elements, namely small capacitors and resistors. It does not use external power. Therefore, it creates "insertion losses" or a degree of attenuation. However, when it can be used (which is not always) it can potentially deliver the best purity of all xover alternatives.
This, is what I am using on the tweeter side of the hybrid alternative described above.