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Advent experiment - mod - much better sound IMO


Pete B

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Hello Pete:

Thanks a lot for the links to the picture, it's what I needed to do this.

I should be ok now, just buy the parts and solder away.

Regards, Bill

PS: I'll let you know how I make out.

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Dear Pete B,

My Advent/1 high is a bit harsh. Can I apply the mod option for reducing the high?

Yes it should work just fine, the Advent/1 is essentially the NLA in a smaller box.

I have a pair here that I'm using with BSC.

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Hi Pete B,

I have bought C1 and C2. However the shopkeeper told me that for the R1 and R2, she got to know whether they are 10W, 5W, 2W, 1W, 1/2W, 1/4W5% or 1/4W1%. Please advise me which one should I buy

And is the green line in the photo a ground cable? Many thanks!

Your recommended info:-

Yes it is the 6 dB version from post #41 in this thread:

4.7K Version, these values are for RL = 47K or typically an EPL or tape monitor

loop:

R1 = 4.7 K, C1 = .0047 uF

6db: C2 = .068 uF R2 = 4.3K

C1 can be two .01 uF green mylar caps from Radio Shack in series.

C2 can be a .047 uF and .022 uF also from Radio Shack in parallel.

Just so happens that I have a good supply of .068 uF, .01 uF, and 4.3K resistors

here. I forgot to include them in my rush to send it to you. I'll get them off

to you soon. Figured I'd wait to see how you liked it.

post-102083-1215396342.jpg

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Hi Pete B,

I have bought C1 and C2. However the shopkeeper told me that for the R1 and R2, she got to know whether they are 10W, 5W, 2W, 1W, 1/2W, 1/4W5% or 1/4W1%. Please advise me which one should I buy

And is the green line in the photo a ground cable? Many thanks!

Your recommended info:-

Yes it is the 6 dB version from post #41 in this thread:

4.7K Version, these values are for RL = 47K or typically an EPL or tape monitor

loop:

R1 = 4.7 K, C1 = .0047 uF

6db: C2 = .068 uF R2 = 4.3K

C1 can be two .01 uF green mylar caps from Radio Shack in series.

C2 can be a .047 uF and .022 uF also from Radio Shack in parallel.

Just so happens that I have a good supply of .068 uF, .01 uF, and 4.3K resistors

here. I forgot to include them in my rush to send it to you. I'll get them off

to you soon. Figured I'd wait to see how you liked it.

1/4 or 1/2 Watt is fine.

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Hi Pete B,

And is the green line in the photo a ground cable? Many thanks!

Yes the green is ground and it must be connected.

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Guest sfox52

Pete- Please advise as to what values for R2 & C2 I should use- I have NLA's that have been refoamed & recapped w/ 13 uf film & foil caps. The level switches are still in the x-over circuit. I want to use the BSC in the tape loop of a Yamaha 70 wpc receiver- this system is in a large bedroom, against the wall ,with a cathedral ceiling. I have some parts already, & maybe enough to knock the thing together. Is there a difference between the original & the "new" when using the BSC?

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Pete- Please advise as to what values for R2 & C2 I should use- I have NLA's that have been refoamed & recapped w/ 13 uf film & foil caps. The level switches are still in the x-over circuit. I want to use the BSC in the tape loop of a Yamaha 70 wpc receiver- this system is in a large bedroom, against the wall ,with a cathedral ceiling. I have some parts already, & maybe enough to knock the thing together. Is there a difference between the original & the "new" when using the BSC?

The switch on the NLA should be set to normal to duplicate what I did with the OLA's on extended.

It's hard to say how much compensation is correct. You could go with 4.3K and .069 uF made from a .047 uf and a .022 in parallel, then if 6 dB is too much, disconnect the .022 and change the resistor to 7.5 K which will provide 4 dB.

You can also experiment with the tweeter switch to determine the best balance.

You might want to try the loaner, it only costs a few bucks to ship, to get a baseline, then see if you find 6 dB to be too much.

Pete B.

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Guest tejasrichard

Hey Pete,

Thanks for all the work you've done on this. I started on a restoration project (2 walnut OLA's, 2 utility OLA's, 2 NLA's) in march, and have spent more time reading forums than I care to say. This one has been truly informative. I will be finishing the 2nd set of OLA's this weekend, after which I'm considering trying out your bsc project. I'm not sure how much I really need it, as my room doesn't allow the speakers to be pulled out from the wall. But what the heck, it sounds like fun, and that's what it's all about, right?

Thanks again,

Richard

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Hey Pete,

Thanks for all the work you've done on this. I started on a restoration project (2 walnut OLA's, 2 utility OLA's, 2 NLA's) in march, and have spent more time reading forums than I care to say. This one has been truly informative. I will be finishing the 2nd set of OLA's this weekend, after which I'm considering trying out your bsc project. I'm not sure how much I really need it, as my room doesn't allow the speakers to be pulled out from the wall. But what the heck, it sounds like fun, and that's what it's all about, right?

Thanks again,

Richard

Hi Richard,

Excellent, I'm sure you'll enjoy them.

I would certainly try the BSC. You might want to start at 4 dB as I mentioned in the previous post,

then go up to 6 if you feel that you need more. Or try the loaner.

It is certainly worth trying.

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Hi Pete,

I have put all the components together follow exactly your recommendation. It is my first experience to having such kind of project, boght soldering gun, soldering paste, etc. Hope my skill is not laughable. :angry::P:rolleyes:

I connected the BSR to my integrated amp Technics SU-A900MK2 tape loop. Wow, very sweet and warm midrange and the bass extention is geat. No more ears piercing high and I could listen to my Advent/1 for long time.

Thank you Pete.

post-102083-1215840500.jpg

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Hi Pete,

I have put all the components together follow exactly your recommendation. It is my first experience to having such kind of project, boght soldering gun, soldering paste, etc. Hope my skill is not laughable. :angry::P:rolleyes:

I connected the BSR to my integrated amp Technics SU-A900MK2 tape loop. Wow, very sweet and warm midrange and the bass extention is geat. No more ears piercing high and I could listen to my Advent/1 for long time.

Thank you Pete.

Hi Gary,

It is nice to hear that this was your first project, and that it worked!

Your construction work looks just fine.

Did you really use a soldering gun, or a small iron?

Most guns are over 100W there's a 230W model shown here:

http://www.action-electronics.com/weguns.htm

You really want something like a 15 or 25 W iron. This is a low

cost model without temp control:

http://www.radioshack.com/sm-15-watt-solde...pi-2062728.html

Anyway, hope you enjoy it!

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I've been asked for a schematic for the version with the 3 way switch, for 4, 5, or 6 dB of boost.

I actually just built it, didn't draw a schematic, I probably hand drew a sketch for layout

purposes but honestly my hand drawings are not that clear so I'm not sure if I saved it, LOL.

The switch is a DPDT center off 3 pos switch, that is available from RS.

I found a simpler way to do the switching that allows a single DPDT, center off, 3 pos switch to be used:

Build it for 4 dB of BSC, which has a shunt R of 7.5K, C of .047 uF

Wire the center of the DPDT switch to the output terminal, one section to the Right, other to the Left.

One switch side gets 22K in series with .01 uF to ground, one for R another for L, this is +5 dB,

Other switch side gets 10 K and .022 uF to ground, one for R another for L, this is +6 dB,

Center off pos is +4 dB.

HF boost just switches in the .0047 uF cap.

Does this make sense?

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I've been asked for a schematic for the version with the 3 way switch, for 4, 5, or 6 dB of boost.

I actually just built it, didn't draw a schematic, I probably hand drew a sketch for layout

purposes but honestly my hand drawings are not that clear so I'm not sure if I saved it, LOL.

The switch is a DPDT center off 3 pos switch, that is available from RS.

I found a simpler way to do the switching that allows a single DPDT, center off, 3 pos switch to be used:

Build it for 4 dB of BSC, which has a shunt R of 7.5K, C of .047 uF

Wire the center of the DPDT switch to the output terminal, one section to the Right, other to the Left.

One switch side gets 22K in series with .01 uF to ground, one for R another for L, this is +5 dB,

Other switch side gets 10 K and .022 uF to ground, one for R another for L, this is +6 dB,

Center off pos is +4 dB.

HF boost just switches in the .0047 uF cap.

Does this make sense?

Hi Pete:

Sorry for the delay, I know you answered my request here.

Well, I think I understand your answer, but a simple diagram would help.

Maybe I'll take a stab at it and send it to you before I buy the parts and try it.

Thanks, Bill

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Hi Pete:

Sorry for the delay, I know you answered my request here.

Well, I think I understand your answer, but a simple diagram would help.

Maybe I'll take a stab at it and send it to you before I buy the parts and try it.

Thanks, Bill

Sure Bill, that's fine.

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The BSC loaner is available, was anyone waiting to try it?

Please remember that this circuit is passive and inserts a loss

into the system and therefore you have to turn up the volume

more. This is normal and it will not harm the system, the amp

is not working harder, it just needs more signal for the same

power output.

Several people have asked about this, yes the volume control

will run at a higher position than what you're normally used to.

Is anyone running LP where they run out of gain perhaps with

a low output cartridge?

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Hi Pete,

I have tried out 4, 5 and 6 dB of 4.7K version and finally settled at 5 dB and 6 dB. I also tried switchable 5dB and 6dB set with reference to your DPDT switch. When switched to center off, there is obviously some signal loss but is not an issue to me as I prefer 6 dB of boost.

I am using a 40 watt HAKKO Red No. 502 for soldering work, as this http://us.100y.com.tw/ChanPin.asp?MNo=9882 Really went through a hard time to materialize this BSR set for a chemist :rolleyes:

I've been asked for a schematic for the version with the 3 way switch, for 4, 5, or 6 dB of boost.

I actually just built it, didn't draw a schematic, I probably hand drew a sketch for layout

purposes but honestly my hand drawings are not that clear so I'm not sure if I saved it, LOL.

The switch is a DPDT center off 3 pos switch, that is available from RS.

I found a simpler way to do the switching that allows a single DPDT, center off, 3 pos switch to be used:

Build it for 4 dB of BSC, which has a shunt R of 7.5K, C of .047 uF

Wire the center of the DPDT switch to the output terminal, one section to the Right, other to the Left.

One switch side gets 22K in series with .01 uF to ground, one for R another for L, this is +5 dB,

Other switch side gets 10 K and .022 uF to ground, one for R another for L, this is +6 dB,

Center off pos is +4 dB.

HF boost just switches in the .0047 uF cap.

Does this make sense?

post-102083-1217081135.jpg

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  • 3 weeks later...
Guest archie2
I posted this to another list, for what it's worth, be interested to hear from others if they try it:

There was talk sometime back about large Advent speakers and I'm always surprised when people comment about how good they are, I suppose they might be good for their day or good for the low price point. I noticed fairly serious midrange coloration from the first listen. Still, they had the best bass and a real tweeter when compared to the competition of the day, Dyna A-25, EPI 100, AR2. The Dyna A-25 and EPI100 both had much better midrange smoothness.

I happen to have a pair of large Advents here where one was reconned about 10 years ago and the other needs to be reconned. These are otherwise original, never had any tweeter problems. I've always thought the Advent (about $250/pr in the 1970s) would be a good candidate for mods since it seems as if the basic components are good.

I hooked the good one up in my main system with an A/B switchbox to compare it to my commercial floor standing 3 way reference (about $2000/pr). The reference was 3ft out from the wall and I first placed the Advent on top. The Advent was much louder in the tweeter range, very bright sounding, there's a 3 position tweeter level control and in the "increase" position it sounds like a shrill transistor radio with bass, not even a good transistor radio, shouty sounding to an extreme. The other positions sounded better but still something drastically wrong in the midrange. My kids gave a big thumbs down for the Advent and thought the A/B switch was very cool. I guessed that the coloration was midrange peaking and there was also a boxy quality to the sound. Definitely like sound from a speaker rather than music in the room and I thought they'd need a lot of work. The A/B switch also provides line level switching so I inserted a volume control to match levels. Matching was hard due to the frequency response differences.

Next I put them on the floor which helped bring up the mid bass to some extent, still not right, not even convincing on vocals.

I happen to have a passive line level circuit that provides baffle loss compensation (6 dB) with also some high end boost, mostly above 10 kHz. Boost this high tends to add air to the sound rather than brightness and as I recall these older tweeters start to roll off above 15 kHz. I didn't think it would be this simple but now they were very close at least at moderate levels and with the tweeter switch now in the "extended" position. The Advent runs out of displacement capability with any demanding bass material and higher listening levels. Now the reference required some level reduction due to the 6 dB of loss in the baffle compensation circuit. The Advent was now heavy in the mid bass, and elevating them 10.75" was a bit too much, sounding thin, 4.75" was about right overall. The two sound very similar with this setup, the reference is a touch cleaner, smoother, and more transparent but they're very similar at moderate levels, as I said the Advent runs out of steam in the bass, and the reference also has more extended very deep bass but these are design differences. The difference is much more subtle having to listen for it rather than being in your face. I believe that the baffle step compensation is a bit too much, 4-5 dB is probably about right, still much better even at 6 dB.

I thought the speakers would require much more work, they're not perfect but the difference is dramatic. Advents have never had that disappear, music in the room quality, they do with this shaping network. I'll probably do some driver measurements, don't expect to do full measurements of the Advents, just don't have the time. Might work up crossover mods so the line level circuit is not needed.

These are bookshelf speakers that one might think should not need baffle step compensation when used in bookshelf applications but I've heard similar colorations even on the floor against a wall. Actually, on an ear level shelf they'd see only one close boundary, the wall behind. Placed on the floor out in the room should provide a similar one close boundary response and therefore the compensation is probably about right even for elevated bookshelf applications, adustments to this circuit are easy:

Here's the baffle step and HF compensation network:

--------- R 2.2 K ----------------------------

|---- C.01uF -----|.....|

...........................C.1uF

............................|

..........................R 2.2K

............................|

------------------------------------------------

ignore these: ..... they're needed because spaces are removed on this board

Pre should have < 100 ohm output Z, power amp > 22K input Z.

Has anyone tried the BSC in OLA's where C2 has been changed from 16 uF to 8 uF?

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  • 2 weeks later...
Guest archie2
Has anyone tried the BSC in OLA's where C2 has been changed from 16 uF to 8 uF?

Silly question when I remembered that later Advents were changed from 16 uF and 16 Uf to 16 uF and 8 uF. I had the earlier versions and changed them to a 16 uf and 8 uF. Better memory next time.

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Silly question when I remembered that later Advents were changed from 16 uF and 16 Uf to 16 uF and 8 uF. I had the earlier versions and changed them to a 16 uf and 8 uF. Better memory next time.

I originally did the experiment with 16/16 OLA's so your question is not unreasonable.

And I did use extended mode which includes that cap.

I'd say that you might want 1 dB less BSC if you had the 16/8 instead of 16/16, but

really the amount required depends on the room and general preference as we have

already discussed.

I'm keeping all my Advent stock internally so no I've not tried BSC with the 16/8

version. I have tried it with the NLA and see a similar improvement.

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Guest archie2
I originally did the experiment with 16/16 OLA's so your question is not unreasonable.

And I did use extended mode which includes that cap.

I'd say that you might want 1 dB less BSC if you had the 16/8 instead of 16/16, but

really the amount required depends on the room and general preference as we have

already discussed.

I'm keeping all my Advent stock internally so no I've not tried BSC with the 16/8

version. I have tried it with the NLA and see a similar improvement.

Actually I have the BSC 2 dB less for the 16/8 and it takes just enough harshness out to sound pleasing to my ears. I tried the 6dB but felt it muted the highs a bit too much. I have them stacked tweeter to tweeter. Also used electrolytic replacement caps with 0.01 uF Theta caps bypass on C2.

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  • 2 weeks later...

Don't know exactly where to put this little gem. Don't think it is worth a new topic.

Have been so pleased with my advents since I built the bsc, wouldn't be inclined to exhange them for anything. Of course, they are and remain (until now) the unheralded bargain of the 21st century. But their auction prices have been creeping upward.

See the recent A-4 result on Ebay. Item number:300254526569. Granted that the presentation was way above average, so too was the result. At first blush, the sale price of $617.67 plus shipping seems extreme. But in truth, I guess the adjusted new price of a new pair in 1978 would be around $800. Pretty interesting.

Once again, thanks Pete for all your good work!

Marty

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  • 3 weeks later...
Don't know exactly where to put this little gem. Don't think it is worth a new topic.

Have been so pleased with my advents since I built the bsc, wouldn't be inclined to exhange them for anything. Of course, they are and remain (until now) the unheralded bargain of the 21st century. But their auction prices have been creeping upward.

See the recent A-4 result on Ebay. Item number:300254526569. Granted that the presentation was way above average, so too was the result. At first blush, the sale price of $617.67 plus shipping seems extreme. But in truth, I guess the adjusted new price of a new pair in 1978 would be around $800. Pretty interesting.

Once again, thanks Pete for all your good work!

Marty

Thanks Marty, I appreciate the positive feedback.

I should probably mention that it was a surprise to me that the BSC worked so well,

that is why I posted it in the first place. Anyway, thanks again.

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  • 1 month later...

I just tried the BSC circuit with a pair of New Large Advents that I bought a couple of weeks ago. I used the RL=47K, 4db version with the tweeter switch at normal and the circuit installed into the tape monitor loop in a Marantz 1070 integrated amp. The speakers sound so much better. I was kind of disappointed when I first heard the speakers because I thought they sounded rather harsh/edgy. Luckily, I found this forum and this thread. The speakers were intended for my secondary "basement" system. Now I find myself spending more time in the basement. Thanks to you and all the contributors to this very interesting discussion.

I do have one question. Will this version of the circuit also work if installed between a pre-amp and a power amp? If I have to change it, what specifications do I have to look for in order to decide which RL version I need to use?

Thanks,

Harry

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I just tried the BSC circuit with a pair of New Large Advents that I bought a couple of weeks ago. I used the RL=47K, 4db version with the tweeter switch at normal and the circuit installed into the tape monitor loop in a Marantz 1070 integrated amp. The speakers sound so much better. I was kind of disappointed when I first heard the speakers because I thought they sounded rather harsh/edgy. Luckily, I found this forum and this thread. The speakers were intended for my secondary "basement" system. Now I find myself spending more time in the basement. Thanks to you and all the contributors to this very interesting discussion.

I do have one question. Will this version of the circuit also work if installed between a pre-amp and a power amp? If I have to change it, what specifications do I have to look for in order to decide which RL version I need to use?

Thanks,

Harry

Hi Harry, thanks for your comments!

The input impedance of the power amp or tape monitor loop is what matters.

The 47K version was intended for tube equipment that usually has an input

impedance around 470K or 1M ohm.

I was looking for an Rin for about 10X or more of the BSC circuit.

Tape loops are often 47 - 100K Zin, so the 4.7K BSC would be correct.

Solid state power amps are often 22K Zin, and the 2.2 K BSC should be used.

The BSC boost will be way off if you use the 47K version with most SS gear,

did you mean 4.7K?

Post #41 here has the values, if you need to change it:

http://www.classicspeakerpages.net/IP.Boar...ost&p=66294

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