BX63 replacement?

I have a B460 that will eventually be put to use in a home theater setup. It was found at a junk sale (along with a B380) for $20 several years ago and the BX63 cross-over unit is long gone. So was the finish, grill, and cone... Anyway, what can replace the elusive BX63? I have the schematics but they are meaningless to me at this point. But I can brew beer so maybe I can build one or find someone that can...

Also does anyone have a suggestion for a "cheap" power amp to drive it? Cheap meaning <$400 if possible.

Thanks,

Don

Nice features of the BX63A are that it allows you to place an amp into strapped (or bridged) mode and it has an adjustable low pass filter from ~ 63 Hz to ~ 126 Hz.

If you can't find a BX63A, or don't want to build one, you can use a modified JBL 5234A or a JBL 5235 (preferred since it already has bypass capacitors installed parallel to the electrolytics).

The required modification to make the 5234A or 5235 work with the B380, B460, 4645B, or 4645C is to replace the following 0.27 uF capacitors with 0.22 uF capacitors.

C13, C14, C15, C16, C113, C114, C115, C116

The 5234A schematic can be found in the back of the manual located here:

http://www.jblproservice.com/pdf/Vin...A%20manual.pdf

C7, C8, C9, C10, C107, C108, C109, C110

The 5235 schematic can be found in the back of the manual located here:

http://www.jblproservice.com/pdf/Vin...5%20manual.pdf

In both (modified) models set the first four DIP switches to 1100. This will yield the necessary boost at ~ 25 Hz. You can then use the LFE output of an AVR to feed the 5234A/5235 and something like an Adcom, Citation, or Crown amp purchased off eBay.


Another option might be to build this and apply the necessary boost at ~ 25 Hz:

http://sound.westhost.com/project84.htm


Finally, I think Parts Express has some Plate Amps that might have adjustable high pass bump filters.

If you're looking for cheap gear I would recomend buddying up with your local JBL dealer, preferably one who does PA work. They seem to have no problem ditching "old" (read heavy) amps and such for the newer lighter models. I picked up a used BGW 750G for a $100.00 CND 'cause "I can't drag that old beast around". It had come in on a trade in and they simply had no use for it. One of many deals I've been lucky enough to have stumbled across from the same guy.
Kelly

Yes Parts Express does have an amp #300-794 with adjustable boost. From +1db to +5db. The +5 has has ranges with the boost between 20-23 hz and 24-30 hz. There are 2 more with higher frequency ranges. The sheet for the specifics is available on the Parts Express site.

Rob :)

Holy cow, first people finding brand new L100s (another thread), now $20 B380s! :screwy:

With regards to plate amps: I've used some of the same amps as the PE amps, under different names... and I have a reservation as to whether they really have BALLSY enough power supplies, to do a heavy-cone woofer such as a 2235 or 2245 justice. I've thought that the plate amps I've heard, were a little light-weight when the chips were down, on complex, loud low stuff...

There do seem to be some good plate amps out there; for one example, check with Adire Audio, I think they have a heavier amp than the PE, and one model is still less than $400, IIRC...

Regards,
Gordon.

Quote:

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Originally posted by dprice

Also does anyone have a suggestion for a "cheap" power amp to drive it? Cheap meaning <$400 if possible.

Thanks,

Don

---

I have found that the most "Bang for the Buck" amps out there are the Soundcraftsmen PM860s and PM840s. There are other models in this 800 series that I have not tried, they all have the same specifications, 205 WPC 8 ohms. They are frequently under $150 on eBay. I have three that I am currently using in my home theater. They are not the best amps ever, and I will be upgrading, but you won't find a better amp at that price point.

You can frequently find one of the crossovers Giskard recommended for under $100, and add in another $100-$150 for a PM 860 and you have something that is significantly better than any plate amp. Well excluding the plate amps Bryston is making, but they are not inexpensive.

I just did a quick eBay search.

Here is one of the other Variants, the PCR 800. This one isn't too pretty, but it could be fine.
BTW you have to look under Soundcraftsman as well as Soundcraftsmen.
http://cgi.ebay.com/ws/eBayISAPI.dll...category=39783

hello,

you will sell that cabinet of the b380?

kor

Thanks for all of the advice! Is there a simpler solution (than the BX63) for the bass boost "problem" if I am starting from the single channel LFE output (20-120 Hz?) from a DD 5.1 source? I assume there would be since (AFAIK) the BX63 was designed around a full range input...

The plate amps look great but a little weak...any chance a bass amp w/EQ (Ampeg SVT III series or similar?) would be clean enough (and quiet enough) for home theater use?

korgroenewoud - I gave the restored B380 to my little brother as a Christmas gift.

Don

"Is there a simpler solution (than the BX63) for the bass boost "problem" if I am starting from the single channel LFE output (20-120 Hz?) from a DD 5.1 source? I assume there would be since (AFAIK) the BX63 was designed around a full range input..."

Yes there is. Use a suitable high pass boost filter between the LFE output and the sub amp input.

Here is the schematic for the BX63/BX63A bump filter for use with the B380 and B460. It is suitable to place between the LFE output of an AVR and the input of a suitable subwoofer power amplifier that has it's own DC blocking.

Here is a schematic for a nice 25 Hz +6 dB bump filter with Q = 1.93 that is suitable for the B380, B460, 4645B and 4645C.

Again, it should be used with a decent power amp that has it's own DC blocking.

Gaiskard,

Thanks for the schematics! I didn't do well in my circuits class but at least I know what the resistor and capacitor symbols look like. My foggy memory tells me the triangle things are op-amps...correct? If so, is there a particular type or rating (or part #) to look for? I'll read the idiot's guide to elctronics if I can find it...

What is DC blocking? What happens if the amp doesn't have it? I'm almost certain to use a cheap ($50) power amp for testing (at low power and no audible distortion) before getting an inexpensive used pro-audio amp (Crown, Carver, QSC) with some real power.

Thanks again!

Don

"My foggy memory tells me the triangle things are op-amps...correct?"

Yeah, they're symbols for opamps.

"If so, is there a particular type or rating (or part #) to look for?"

A TL072 will do fine here for a VLF bump filter.

"I'll read the idiot's guide to elctronics if I can find it..."

Ok

"What is DC blocking?"

Just an RC filter that blocks DC. Some amps don't have them. If your amp doesn't then pop a 10uF/25V cap into the circuit just before the 180 ohm output resistor.

"What happens if the amp doesn't have it?"

Your woof could go poof if DC get's dumped to the power amp.

DC block in the BX63A.
The BX63 didn't have any... it doesn't take much of an imagination to figure out why JBL added them in the BX63A.

Quote:

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Originally posted by Giskard
DC block in the BX63A.
The BX63 didn't have any... it doesn't take much of an imagination to figure out why JBL added them in the BX63A.

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Gee, you mean people didn't actually WANT hyper-extended 2235s with their voice coils jammed all the way out, cocked and hung up on the top of the gap?? Geesh, what's the world coming to? :D :screwy:

Regards,
Gordon.
who had that happen himself once... whoa, that was a bad day...

Quote:

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"voice coils jammed all the way out, cocked and hung up on the top of the gap??"

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And THAT, is exactly why I need a recone kit for the babiest of 43xx series - babiest, but very serious in it's own right! ;)

And, it weren't my doing to have hung it! I'm on the repair team. (hey Don - we need an smiley icon for a Doctor...!! Or, er, at least a nursie ;) )

"Gee, you mean people didn't actually WANT hyper-extended 2235s with their voice coils jammed all the way out, cocked and hung up on the top of the gap?? Geesh, what's the world coming to?"

I'm sure it had more to do with warranty repair :D

http://vsdrives.com/graphics/equalzr.jpg

As you can see, it's a much superior drawing than the others. Bar napkins are that way.;)

Hi Tom,

"As you can see, it's a much superior drawing than the others. Bar napkins are that way."

Haha :)

This is for the B460 you picked up from Ron Gold right? :)

How is Ron these days?

I used to go over to his house every once in awhile many, many years ago to listen to his various creations. I lived a few blocks away from him when he was still on South Bannock.

Anyway ... I'm glad this worked out for you :)

Yep. Got it from Ron. It was in perfect condition, until he noticed a noise, something amiss in the 2245H driver. When I arrived to pick up the B460, he had a brand new 2245H still in the box for it. :) .

I was so happy to find a B460 like this. It was always the one I wanted. Thought I'd never own one. It's free from scratches, the wood is nearly perfect, well cared for. With the BX63(A) equalization, it is music to my ears, beautiful, perfect!

I don't know where he got (gets) the 2245H, but he says he stocks them. He's a very reputable guy.

He hasn't worked out of his house in years though. The house on S. Bannock is also where I first met him. We were all quite a bit younger then :( .

He's on a corner on S. Broadway now, I forget exactly, a few blocks south of Hampden.

He's got a nice shop, a couple of employees, was carrying his usual assortment of vintage stuff, but also KEF, NHT, a few HDTVs, some JBL Pro. He's frequented by loyal customers, who know him by name.

He's calm and relaxed these days...:smthsail:

http://vsdrives.com/graphics/sub2.jpg
http://vsdrives.com/graphics/sub1.jpg

The wife HATED it when I brought it home...OMG what to do? I could always get another wife, but a B460? ;)

So I set the lamp on top of it, put the plant on it. Then people started coming by, saying it didn't look bad. Once she figured she could use it as table, put pictures knick-knacks on it, she gradually came to accept it. Then my sister came out from Dallas, interior decorator. I thought OMG, I'm in trouble now. First thing she said was, "what is it? does that thing have to be in that corner?" :bomb: Before I could answer, she said "it's nice wood, looks kind of nice." And so she started blending stuff around it into the room decor. WHEW!!!!!!!!!!!!!!!:banghead:

Memo: Knick Knacks tend to get jostled about on top of a B460 :D

But here is the corner opposite. It's obviously just a family room, not a home theater, but it works. I made a 5.1 system from JBL LSR-25P. All in all, for what it is, it sounds great and blends seamlessly with the B460. The room itself is pretty good set up this way, room modes are not out of control, and swept tones show a reasonably flat room response, not perfect, but within about 7 db from 25 hz to 120 hz, the upper number being the crossover point to the satellite speakers.

The B460 is powered by a Crown K2, so if you seriously crank the volume, the LSR-25Ps can't run with it of course, peaking at around 109 db. No one has complained though...

http://vsdrives.com/graphics/michelle.jpg

Is this the same Ron Gold, of Gold Sound you guys are talking about? A friend of mine and I, used to use LOTS of his speaker parts. My friend had the first pair of JBL 2404 I ever heard, they came from there... and that's when I fell in love with JBL tweeters... :yes:

I miss the drivers Gold Sound used to sell under their own brand name... especially the 1260 and 1270 12" woofers. Man, we built some DEVASTATING car stereo systems with those, back in the late '80s, with those, the old Altec Voice of the Highway 6x9s (usually with the tweeters removed, used as midbass only), the Gold Sound 620 midbass drivers, and/or the old Sony XS-L16 6" midbasses (I still have a pair of these, waiting for the right project), Audax 12P25 and PR17 mids, and the 2404, one of the MB Quart titanium domes, or a Focal fiberglass dome on highs.

Stuff that would do 126+ dB in the car (that's all we knew, the old Radio Shack SPL meters topped out there!), but had SLAM, PUNCH, midbass SNAP and CLARITY. . Usually, triamped (subs on one amp, midbass on another, mid/highs on a third) 4-way systems, when we could get the OK to do it. Literally, like a rolling large-format studio monitor system, in many ways!

We had people stacked up for months, wanting us to sort out and beef up THEIR car systems, after they heard what COULD be done, beyond the usual "sizzle-boom" that most of the hack shops were doing... and unfortuntately, for a large part, STILL seem to be doing...

Whew, sorry for the off-topic ramble... :slink:

Regards,
Gordon.

:)

Thanks for the pictures :)

"Thanks for the pictures :) "

Yea, thanks! That B460 is a beauty - tugging at my heart strings.

Got me wondering why dang fireplaces still command center-stage and are so rarely used. Sure screws up the lay-out! Plus, they work just fine in corners...! :D

Say - is that a home video? ;)

Quote:

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Originally posted by boputnam
"Thanks for the pictures :) "
Got me wondering why dang fireplaces still command center-stage and are so rarely used. Sure screws up the lay-out! Plus, they work just fine in corners...! :D

Say - is that a home video? ;)

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You have that right about the dang fireplace :mad:

That's Michelle from HDNet, sumtuous creature :rolleyes:

Um, Yeah!

Makes me want to go down to the 16th Street Mall...

Quote:

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Originally posted by GordonW
Gee, you mean people didn't actually WANT hyper-extended 2235s with their voice coils jammed all the way out, cocked and hung up on the top of the gap?? Geesh, what's the world coming to? :D :screwy:

Regards,
Gordon.
who had that happen himself once... whoa, that was a bad day...

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OK, sorry to dig up this old thread, but this sounds exactly like what's happening to my B380. As soon as I pour the power to it that 2235 starts popping. I've got to believe it being hyper-extended.

Is there a way to add a DC block to the BX-63? Could this be my problem? The speaker sounds great until I add too much power.

Thanks, Terry

Are you still looking for a bx63?
Check your PM box.

Hello

I would like to come back on Tom rober schematic for xover .
I do not knwo a lot about electronic !

the bx 63 has one dual input and 2 dual output ( 1 filtered under 63 hz and 1 upper 63 hz ! )

The drawing has one input and one output !

Can someone give more explanations !

Gerard

http://manuals.harman.com/JBL/HOM/Te.../BX63%20ts.pdf

First thing BX63(A) does is sum the left and right channels to mono for generating the single subwoofer output.

The "two" bass outputs are the same mono output, one is merely inverted for use in converting a single stereo amp into a higher-powered "bridged" amp. Those are NOT stereo LF outputs. If you hooked a stereo amp and dual subwoofers to them, they would acoustically sum to zero bass....

If you don't need summing and don't need bridging, it's a simpler schematic, is all.

If you want stereo subs, you build two of those....

thank you !


I never saw the schematic !

Gerard

I think my schematic also omitted the "low pass" filter, since I was using it on a subwoofer channel LF output that already had a low frequency cutoff applied.

So the salient point of the simplified circuit was to give it the "boost" curve intended for the 2245H driver inside the B460 enclosure.

Thusly, I omitted the other features of the BX63A that I didn't need.

The main thing to know, is that the entire BX63A can be easily constructed from the schematic (PDF file), or just the parts you need for your own installation.

http://cgi.ebay.com/ws/eBayISAPI.dll...783056307&rd=1

The price on ebay will go up to the moon !!!!


Gerard

Usually about $200

200 $ price of an amplifier .... or a very good burgundy bottle or a night in a marrakech palace .


Gerard
http://images.google.fr/images?q=tbn...l/gfx/05_1.jpg

I wanna night in a Marrakech palace. Yup. :D

[Already gotta BX63A....]

400.00$ ; 4 night in Marrakech !!!

http://cgi.ebay.com/ws/eBayISAPI.dll...MEWA%3AIT&rd=1
gerard

http://www.travelinstyle.com/morocco...SofitelRak.jpg

Quote:

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Originally Posted by JuniorJBL

Usually about $200

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Wrong!!! More like $400.00

I got mine for $195 on ebay. Guess it's just what happens!:blink:

Of course there was no set up guide included with my recently acquired B380 and BX63A. Okay, I read this

http://www.audioheritage.org/vbullet...04&postcount=6


and I've got a number of PCR800 amps, six to be exact. However, I don't have any of the Soundcraftsmen bridging "thingees" to use.

If I use the "normal" and "inverted" LF outputs on the BX63A to the A and B inputs on a PCR800, does that preclude the need for the Soundcraftsmen bridging device? If so, then I merely run one speaker cable (two wires), one wire from A+ to red and the other from B- to black? Or did I just blow up the B380? (Figuratively speaking, of course; I haven't done anything yet.) :bomb:

http://manuals.harman.com/JBL/HOM/Ow...ual/BX63om.pdf

Thanks for the link, Lancer. Based on that, I don't need the Soundcraftsmen bridging device.

Then this is what I plan to do.

A long shot here - need some help. I am trying to build a pair of the filters shown in post #10 on this thread by "4341B", using TL072's. Trouble is, I need to have it work with balanced inputs and balanced outputs, and have no idea how to do that :confused:. Can anyone provide a clue how to modify this circuit for balanced ins/outs?

Many thanks in advance!

You could add a Balanced Line Receiver chip before the first TL072 and a Balanced Line Driver chip after the second TL072.

Links to some very fine balanced line chips:

http://www.thatcorp.com/datashts/THA..._Datasheet.pdf
http://www.thatcorp.com/datashts/THA..._Datasheet.pdf

Baron030:)

what is the cut off of the modified 5235.