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PostPosted: April 22nd, 2017, 12:57 pm 
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Location: Parkville, Maryland
A lot has been said in this forum about electronic crossovers and yet I still cannot understand how additional electronics comprised of I.C.s and digital processing improves anything other than the bottom line of the manufacturers selling those devices. Then to add insult to injury you have also additional interconnecting cables of variable pedigree from bad to somewhat better. Even the high $$ cables, and there are many to pick from, are nothing to brag about. This brings me to a request from a guy I met at the CAF two years ago that had the same needs as you DIY’ers yet not having the training or skill base to do upgrades for himself.
To make a long story short he contracted SoundMods (me) to upgrade his speaker’s passive crossovers. WHAT?! PASSIVE?! Yep! As with anything there are ways to provide exceptional performance when one does not follow convention. As some of you that know me, I have no use for so-called “audiophile” parts when in my experience they just do not serve the music as some of the U.S. and Russian military and aerospace goodies that were not designed for “audio” yet surpass and beat the audio stuff at their own game.
The speakers upgraded were the B&W 802 series 80 F models with a complex fourth-order Butterworth crossover network that B&W bragged about using a computer program to optimize.
WOW! Yet – they used polyester capacitors for the tweeter networks (tizzy and edgy sound), bipolar aluminum electrolytics for the mid-range networks (muffled and indistinct), and aluminum electrolytics for the woofer networks -- and to add insult to injury they capacitively coupled the woofer networks to the drivers through 1,000-ufd electrolytics (grungy and muddy sound).
Additionally, it seems that they were a bit too aggressive with the crossover points because I presume that when you take into account the series and parallel L/C reactance combinations there were numerous resonances that could be mistaken for mechanical issues created by the drivers.
Yet B&W used high-quality inductors , PC boards with nice thick traces, and their drivers are probably the best available even compared to now.
The attached photos are of the speakers and the component and foil sides of a crossover prior to the upgrades.


Attachments:
B&W 802 series 80 Stock Crossover B.jpg
B&W 802 series 80 Stock Crossover B.jpg [ 405.14 KiB | Viewed 17444 times ]
B&W 802 series 80 Stock Crossover A.jpg
B&W 802 series 80 Stock Crossover A.jpg [ 361.27 KiB | Viewed 17444 times ]
B&W 802 Series 80  F.jpg
B&W 802 Series 80 F.jpg [ 611.41 KiB | Viewed 17444 times ]

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PostPosted: April 22nd, 2017, 3:24 pm 
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Location: Pikesville
Obviously, to each his own....
I start biamp in 1994 passively, but before the power amps. About 4 years ago, I switch to digital crossover and never looked back!
Now, I am listening to digital only....
Im 100% agree with you about B&W. Its easy to drastically improve them just by changing parts...

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PostPosted: April 22nd, 2017, 3:47 pm 
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Right now I'm in the process of building my next set of speakers that are loosely modeled after the old waveform mach 17 "egg" speaker. One of the reasons for this project which will be written up in AudioXPress is to have a set of high performance speakers that are passively crossed over. All my other competent speakers are tri-amped which limits my ability to test amplifiers full range. As I get into this project and work on the passive crossover, I have been painfully reminded why I have not build a passive speaker level crossover in over 40 years.The reasons for active are way too numerous for this blog. I would suggest that this become the subject of one of our get togethers. And, if you do not want to go active for reasons of your own, you can still get many of the benefits of active by putting the passive crossover components before the amplifiers that will then drive the reactive drivers without all the problems of passives between the amps and drivers. Those passive devices will not have to work into complex impedances, and will cost far less than speaker level components, making changes where necessary much less costly and painful.

Tom


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PostPosted: April 22nd, 2017, 7:08 pm 
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Joined: January 15th, 2015, 7:19 am
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Location: Baltimore MD
Tomato.......Tomato


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PostPosted: April 23rd, 2017, 9:56 am 
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I agree with Walt (not the first time, he knows what he speaks, I have heard his stuff)

Two pictures
Maggy llla rebuilt xcover. I went for low DCR and I believe I gained a lot of efficiency. Large ga coils, caps in parallel to lower DCR and the Maggys sing with as low as 100 watts.
Attachment:
mag_llla_worked.jpg
mag_llla_worked.jpg [ 283.35 KiB | Viewed 17420 times ]

The second pic is the Carver ALS stock filter, and as you can see tiny ga wire in coils, 10 cent film caps and electrolytic caps.
This is typical of stock xovers. My 200 watt SS amps(400 into 2ohms which is where the Carver are) would not do much.
I replaced th passive xover with Litz-Riley and the Carvers are exciting, not very Amazing but exciting. I do not run out of steam at 110db at 20hz, but my house cannot take much more
Attachment:
Carver_ALS_worked.jpg
Carver_ALS_worked.jpg [ 236.87 KiB | Viewed 17420 times ]


Tomato....Tomato


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PostPosted: April 23rd, 2017, 11:09 am 
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Amazingly enough most DIY'ers go for the air-core coils yet past tests has shown that laminated core (and 2nd place ferrite core) coils can have very low DCR and lower overall distortion. Wilson Audio recently learned a very old lesson learned almost 60-years-ago by Western Electric and its alter-ego Altec. Their new products sport laminated core coils and the stereo rags have a noticed a global improvement in Wilson speakers' performance.

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PostPosted: April 23rd, 2017, 1:38 pm 
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The inductors I am us for the bass section of the project are 9 mh and are made by Erse. The specs look very good.

http://www.erseaudio.com/Products/IXQCo ... 56-16-9000

http://www.erseaudio.com/Products/IXQCoils

Tom


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PostPosted: April 23rd, 2017, 3:40 pm 
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That's what I am talking about. Nice!

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PostPosted: April 23rd, 2017, 7:40 pm 
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If you are going to use passive you have to use good components. Very, very expensive and restrictive compared to going active. But as with anything else it is all about the execution. Any technology properly executed yields good results. Any technology poorly executed yields s--t.

Tom


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PostPosted: April 23rd, 2017, 9:21 pm 
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As I did -- as I do. The capacitors that I used in the B&W crossover, although never intended for "audio" by the manufacturers, serves the music in ways I could not have imagined 20 years ago. Even the largest -- 50-ufd -- has a self-resonance out past 150-kHZ for use in mil-spec switch-mode power supplies. And who knows what the hermetic stuff was intended for. The polycarbonate caps have the musicality and transparency that even the very best polypropylenes can't match because of the penalty of glare and hardness that comes with polypropylenes. The late Walter Jung found out about Electronic Concepts in his job and was so protective of that find that when he used them in his POOGE modded CD players he painted over the information on the caps.

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