I ordered a 950/770 package today with two M Blocks and I have a question regarding how to set up my main speakers.
I have a pair of JBL L7's that are currently bi-wired through two channels (A/B) of my existing amp as my main speakers.
If I split the premp output from the 950 and run one lead to the M Blocks and one lead to the 770, then have one set of wires from the 770 and one from each M Block, will this work as an effective bi-amp set up?

Second question - Is it possible to bi-wire the main speakers using only the 770?

Final question - I lost the brackets provided with the speakers to run single wires. Where can I find a replacement brackets to eliminate the need to bi-wire?

I appreicate any help in advance of receiving the equipment.

Thanks,

John

The arrangement you described (M-200 plus one channel of 770) would bi-amp them, but I'll leave the potential benefits to some of the local gurus -- the absence of an external crossover in the bi-amp arrangement is going to do the most to reduce the benefits. As for bi-amping using only the 770, you could use two channels of the 770 to drive a single speaker (just substitute an unused channel of the 770 for the 200 in your original arrangement), with very similar benefits and limitations. You could also bi-wire with the 770 -- connect the 950 pre-amp output to the 770 without splitting it, then connect both speaker cables to the binding posts on that channel of the 770 (I do this for my mains and center using spade connectors).

If you lost the jumper plates to connect the low and high binding posts, you can use a short length of speaker cable instead and eliminate the bi-wire/bi-amp cabling.

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gonk -- Saloon Links | Pre/Pro Comparison Chart | 950 Review

I have read numerous posts supporting the use of external crossovers, but I have not understood the significant sonic advantages compared to internal (inside the speaker) crossover networks. I would be interested in anyone who could fill in the blanks due to my ignorance on this topic...

In the case of internal crossover speakers... The full bandwidth low-level signal is sent to the amplifier. The entire signal is amplified, with the voltage gain being applied to the full bandwidth of the input signal. The speaker circuit, however, will only demand current flow from a specific frequency bandwidth dictated by the crossover. The amplifier, therefore, is not required to provide power beyond that which the speaker demands.

In the case of an external crossover... I would suppose that the crossover network is placed between the pre-amp and the amplifier. Each amplifier channel will only see the specific low-level signal intended for amplification. This would clearly eliminate the possible interaction (inside the amplifier) of signals above and/or below the intended frequency bandwidth of that channel. I am not aware that there is any significant interaction of low-level signals of differing frequency inside amplifiers or any other associated negative impact.

I assume that the advocates of external crossover networks have determined that an amplifier that would produce a full frequency bandwidth voltage gain, will somehow create distortion in the limited frequency bandwidth current flow demanded by the speaker circuit in a internal crossover configuration. I have not read this. It may be true, or something else... Is there someone out there in Outlaw territory that could please fill me in???

I have a sound processor with a low pass filter for my Low Frequency (LF) bi-amp channels so I suppose I do have a semi-external crossover. I primarily rely on the internal crossovers of my speakers, as the HF channels of my amplifier are fed the full bandwidth signal.

As for the quality of the crossover network... I am sure that it will vary between speaker manufacturers. I would guess that custom built speakers (DIY) that have drivers assembled from various manufacturers will probably benefit from external crossover networks that are optimized for the each driver’s characteristics.

Some speaker manufacturers, such as Bowers & Wilkins (B&W) have designed and built all of the drivers in the speaker, and the cabinets as well. They have developed a highly optimized crossover network for their speakers that would probably be difficult to match in an external crossover configuration.

Allan

[This message has been edited by AGAssarsson (edited July 09, 2003).]

Woops... wrong button...

[This message has been edited by AGAssarsson (edited July 09, 2003).]

Basically, a passive in-the-speaker crossover network has inductors in addition to capacitors, where a low level active network only has capacitors. Inductors in series with a woofer introduce resistance from the wire - it can't be eliminated, and this effects damping. There is interaction between the passive filter sections for in-speaker crossovers - this is supposedly the reason for "passive bi-amping" to eliminate this interaction.

An active crossover can have much more complex slopes with more precision than a passive network. The capacitors can be very high quality polystyrene or polypropolene with close tolerances. They are also a much lower value of capacitance.

A specific amplifier can be used for each function, such as a tube for the highs and solid state for the lows.

If one amplifier clips, the other one is not effected by that clipping, and keeps playing cleanly.

It is easy with a variable crossover to change the crossover frequency.

I'm sure there are advantages I've missed, but these are what comes to mind now.

Regarding the use of external, active crossovers with consumer speakers; I'd suggest caution. Remember that crossover slopes are additive; that is, they can be superimposed on one another. For instance, say you've got a loudspeaker that's designed to sum flat (frequency-wise) with a second-order (12dB/octave) crossover. If you were to insert and active crossover using the same frequency and another second-order slope, you'd esseentially end up with a fourth-order (24dB/octave) crossover and a big frequency dip at the crossover frequency.

Active crossovers are usually used for pro applications. In most cases, they replace parts of the passive crossover- that is, pro speakers designed to use an active crossover will have few, if any, high-level components (coils, caps, etc.) built into them and they cannot function properly without the external crossover. Some consumer speakers are designed to use active crossovers, and we'll see more in the future; but using one on a speaker designed to operate passively is, I'd argue, a mistake.

[This message has been edited by gw10nt (edited July 09, 2003).]

At least in my system, I don't have passive crossovers at all in my speakers.

soundhound,

I undestand that, but most here own speakers that do. I also understand that AGAssarsson was posing a theoretical query. But with the confusion that seems to be prevalent in the three or four recent strings about biamping/biwiring, I'd hate to see someone run out and spend a bunch of money on an active crossover and, not only fail to see a benefit, but actually do damage to their system's performance in the process.

[This message has been edited by gw10nt (edited July 09, 2003).]

[This message has been edited by gw10nt (edited July 09, 2003).]

I very much agree with your observations. Thanks to you and SH on shedding some more light on this often murky subject.

Soundhound's ability and professional experience allows him to play ball on a field that I have seen, but only as a spectator.

As an architect, I have designed performance spaces and studios, working in concert with the same audio/recording engineers who will operate the environment. As has been said many times, the interaction between the speakers (monitors) and the room is most critical to the overall success of the performance space. While there are some basic rules of thumb that should be observed, the best attempts to model the actual dynamics of a room can only put you in the acoustic ballpark, but usually far from hitting a homer.

There are always compromises that must be made, but the most important lesson I have learned is to provide as much flexibility as possible for positioning the equipment, and options for introducing acoustical panels and/or treatments. I am always amazed by the impact that small changes can have on a room's acoustic profile. The introduction of sophisticated audio spectrum analysis and equalization has made it possible to fine tune the environment even further; after the reasonable passive design strategies have been exhausted.

The Vienna Concert Hall (Wiener Konzerthaus) has been analyzed using the most detailed computer models available; and it is most often predicted to be an acoustic disaster. Parallel walls, bad proportions, and lots of other sophomoric blunders... despite this, it's sound is considered the reference standard for concert halls throughout the world.

soundhound hit all the benefits of external active crossovers. I can’t think of any others that need saying.

I don't think you will see much gain to just bi-amp, and most consumer speakers don't allow you to bypass the internal crossover. If yours allow you to then you may want to try it. Set up can be fun if you are new to doing this sort of thing, you can end up making things sound far worse than what they were.

I tri-amp and bi-amp my pa gear but I don’t bother to bi-amp or bi-wire my HT set up, I just don’t see any gains in doing so. Maybe I could do it just to say that I did.


(Dang it, I promised myself I wouldn’t post in one of these bi-wire / bi-amp threads).

[This message has been edited by Dr.Spike (edited July 23, 2003).]

I have Norh 9.0s actively bi-amped with active crossovers. This was allowed for by a specific design by the manufacturer.

They originally had passive crossovers in them but had extra posts for active biamping. I had to open them up and rearrange the wiring to 2 posts per driver.

This setup is for my 2-channel listening and I can really hear a difference. But remember each driver is getting its own 100w amp! And the crossover points are set for optimum performance of these particular drivers.

In the near future I will triamp with a 3-way active XO and bring in a set of sub woofers.

I am going to all this trouble and expense for 2-channel, and HT will get some benefit from it. Not sure I would do this if I didn't have high end audio sources, and especially for just DVDs. I am not convinced that the DVDs that we have are of high enough audio quality (compression and all that).

unless you can defeat the internal crossovers in your speakers and use an external crossover, biamping does nothing more than add twice as much power. you can sometimes see more headroom (as it is typically called) by using two amps of equal quality as one that is 2x as powerful though.