Taking the B&W 683 Active

[amo]

Finally got a pair of 683's into my house the other week. After hooking them up to a decent 2 ch amp, fed directly off of a CD player, I was impressed with the sound. A week later i added a second, identical 2 ch amp, in a bi-amp configuration. The sound improved considerably, especially at lower volume levels, which is a common issue for the 683's.

I then began contimplating taking out low end signal from the hi freq amp channels and vice versa, via a behringer digital xo or similar, especialy since i have a AES/EBU signal via XLR avaialble to me from my source. Soon after, I discovered freq resp and imp measurements for this speaker. The imp ranges from 3.2 ohms to over 8 ohms i think. The freq resoponce measurement is insane at the higher midrange frequencies, where the FST midrage combines with the tube loaded tweeter via the passive 1st order network, with a considerable dip at 2Khz, no wander i always want to listen louder and louder...

So.. I realized that i might as well bypass the passive XO and go with something like AES/EBU signal -> behringer -> Adcom or ATI mutlti chanel, directly to drivers. I got more excited when i figured out that the new rubberized "beuty rings" around drivers on the 683 simply snap off (not sure on the tweeter yet, but can probably access it through mid openning). This will give me access to the inside of the cabinet to bypass the xo and change the wiring.

So stay tuned for pics and results as i undertake this fun experiment.

Some questions:

1. I was looking at some decent pre-amps for the purpose of remote controlled source switching and volume control. How can i integrate this now that one of my sources is AES/EBU?

2. Should I begin by recreating the factory passive XO in the digital domain, plus some digital eq?

3. How do I account for phase and polar responce? Should I even worry about this?

4. Any other digital XO i need to consider besides Behringer, without spending Accuphase type money?

5. Do I even need to go digial? How about a decent line level device from Bryston or something?

6. Am I insane? Is there an official diagnosis for this?

[amo]

Ok its been a while, but much has been done. Will post photos later today. The speaker is taken apart, with drivers and 2 crossovers pulled out (2 xo per tower). Here is what I can tell you about the new B&W 683 made in china: You get ALOT for the money. Nothing in this price range compares to what else you can get in terms of parts and construction. This started out as a "rewire" project, where I felt like adding some nice cables and of course modifying the wiring to suit an active set up.

I can safely tell you now that rewiring alone will do nothing here. The cables used may not be the pinnacle of high end, but are certainly sufficient in quality and gauge. They look like a 12 gauge high quality copper, even to the tweeter. The passive XOs are great as well, perhaps they could use a part or two replaced... The drivers are wonderful, especially the mushroom bass. The FST midrange is of course not the identical twin of the 800 series, no its not that shiny wonderful looking contraption they have on their website. But its a close cousin with a stiff magnesium (or aluminum) basket. The only item that surprised me was the tweeter. It is definitely smaller then I expected compared to the other drivers, and to the sound the thing produces, but then again, its crossed over at something like 4khz...

In conclusion, this speaker will benefit from the effort I am putting into stiffening the enclosure with large amounts of oak hardwood, sometimes as bracing and many times as additional thickness on the internal walls. I am also lining all internal surfaces with very high grade acoustic foam. Still out on whether I will dampen all surfaces with heavy vinyl.. It will benefit from the demolition of its cute port to become a sealed enclosure, to better integrate with a small sub (same range) next to each tower. The sub will handle up to 40 or 50 Hz max.

The main benefit will come from an active configuration using LR XO built into amplifiers, sitting close to the towers (this is what I have been doing for so ling, researching which direction to take with xo...) The current passive XOs use first order slopes between tweeter and mid, and increase in slope further towards the bass drivers. This sounds great on some material, but to be completely honest, my gut feeling tells me that higher order XOs, if properly integrated, will benefit these speakers which tend to choke on complicated and overloaded passages (although they are angels on female vocals, think Sade). Will post pics as soon as I get home

[amo]

[amo]

Finalized XO choice to R Elliott's LR kit with XLR input (might borow the likes of a digital behringer for the design phase to test slopes and xo points before setting in stone with parts). I realized that I would prefer to maintain the signal in analog once it leaves the 2 CH DAC, whatever it may be. Volume control can be emphesized in the analog pre-amp.


Finalized amp topography to P Daniell's kits (8 of them, all mono, perhaps with fewer then 8 trafos, will see).


Still working out the details on wiring geometry and configuration, but one thing is for certain, the gainclones will be wired directly to drivers (located close to the cabinet in a superstructure), no termination junctions, only soldier. This will only be done once the all parts are in right places. This will put high importance on line level interconnects and the preamp config due to distance from each amp facility. During movement, the tower and amps will have to be moved simultaniously, perhaps with the benefit of a disconnected power supply and traffo section.


Soon to come are photos of the cabinet inside fortification with solid oak, crossbrasing strengthening, addition of high density acoustic foam (studio grade) to most internal serfeces, cable construction and installation.

I am still somewhat dissapointed with these tweeters. I know they are crossed all the way at 5KHz (although with only first order slope), but there just might be a missmatch between them and the rest of the drivers (in quality, maybe not directly audible performance).

The midrange turns out to be far more important then I recognized, given that it plays such a wide range, with high fidelity, using second order slopes. I am betting on improvement with LR 4th order slopes all around. (for my material anyway)

Still reluctant to demolish and erase the cute ports. Probably should wait untill the low bass section is in place and configured properly. (its just an issue of mony, I realy don't feel like building every single thing, especially this time around. All out insanity will come a bit later, when I have more time and money and.... TIME)