Tim D

Refurbing a set of Rev 1 OLA's. Have some questions

38 posts in this topic

Hi all,

It is electrically the same, it looks a bit confusing because of the complexity around the switch.

The top pole of the switch is simply the decrease inductor that is in series with C1.  C1 can go

before or after the inductor and there is absolutely no difference in the response.

What is really special about the LA is the woofer, Henry did some clever optimizations to get the most

out of it under real world use.

Also, let me mention that I don't like the sound of any version of the Large Advents without BSC.

With it, they are very, very good, I could live with them as my main speakers as I stated in the

BSC thread.

If anyone new tries it, give it time, relisten to several of your favorite albums, ask yourself does it

sound real with or without the BSC.

http://audiokarma.org/forums/index.php?threads/large-advent-line-level-baffle-step-compensation-bsc-build-instructions.647441/

and:

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/2692-advent-experiment-mod-much-better-sound-imo/

 

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Back then, with so many purists ready to jump I suggested the 14 ga inductor simply to come

close to the original DCR.  A person has to judge for themselves if they want to spend the money

for the big inductors.  I would do it if they were my main speakers.

The system Q will go up with higher DCR, if you don't like the change add one more layer of damping

directly behind the woofer.

Also, the OLA Decrease setting is really of no use with modern recordings the intention was to cut back on

LP surface and general recording noise - it rolls off the top end far too much.  A shelf is better.  I would 

replace L2 with 1-5 ohms based on listener taste for people who don't want to use BSC.  It is not as good

as BSC but better than the stock frequency response balance.  BSC requires the normal or extended 

position.  I don't think I suggested this back in the day due to so much protest over any change.

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3 hours ago, Pete B said:

Hi all,

It is electrically the same, it looks a bit confusing because of the complexity around the switch.

The top pole of the switch is simply the decrease inductor that is in series with C1.  C1 can go

before or after the inductor and there is absolutely no difference in the response.

What is really special about the LA is the woofer, Henry did some clever optimizations to get the most

out of it under real world use.

Also, let me mention that I don't like the sound of any version of the Large Advents without BSC.

With it, they are very, very good, I could live with them as my main speakers as I stated in the

BSC thread.

If anyone new tries it, give it time, relisten to several of your favorite albums, ask yourself does it

sound real with or without the BSC.

http://audiokarma.org/forums/index.php?threads/large-advent-line-level-baffle-step-compensation-bsc-build-instructions.647441/

and:

http://www.classicspeakerpages.net/IP.Board/index.php?/topic/2692-advent-experiment-mod-much-better-sound-imo/

 

Pete,

Thanks for the response. Yes, I see it now that I've traced it out through all 3 switch positions. Electrically having C1 in either place is going to get you the same series result. 

I'll take a look at the BSC and see what is involved and what it is doing. I agree that the stock OLA's just come up a bit short and I'm willing to try some more changes to bring them to their full capability.

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I suppose I should have drawn it as built but as I see it that is what pictures or pictoral

drawings are for.

How do you plan to place your speakers Tim?

I suggest 60 -100W/ch to drive the LAs, even just to handle peaks.

200W/ch is not too much as long as you go easy on them.

I see that you're planning to use 20W/ch maybe if you never turn it up but it is really worth

trying a 50W/ch or more amp if you get the chance.

As far as Rev1 to Rev 2 goes, Rev 1 used very economical inductors (CHEAP) made with 

very fine wire.  They were known to burn up under heavy use (abuse?) and it just makes

much more sense to use better inductors as they did in the Rev 2.   I've never heard Rev2

but it just gives an example of using lower DCR inductors - I assume it sounds very close.

The 16uF for the increase on Rev1 is also too big, 8 is better, lower might be even better.

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34 minutes ago, Pete B said:

I suppose I should have drawn it as built but as I see it that is what pictures or pictoral

drawings are for.

How do you plan to place your speakers Tim?

I suggest 60 -100W/ch to drive the LAs, even just to handle peaks.

200W/ch is not too much as long as you go easy on them.

I see that you're planning to use 20W/ch maybe if you never turn it up but it is really worth

trying a 50W/ch or more amp if you get the chance.

As far as Rev1 to Rev 2 goes, Rev 1 used very economical inductors (CHEAP) made with 

very fine wire.  They were known to burn up under heavy use (abuse?) and it just makes

much more sense to use better inductors as they did in the Rev 2.   I've never heard Rev2

but it just gives an example of using lower DCR inductors - I assume it sounds very close.

The 16uF for the increase on Rev1 is also too big, 8 is better, lower might be even better.

 

Hi Pete,

I've got a small listening room of about 13x13 and the speakers are set about 18" from the wall. I have them raised about 10" on some Polk 7B speaker stands I had lying around. The room is carpeted and has a big sofa in it. I'm using 20W only because the Marantz 2220B is my favorite and its working well. With my other speakers I've never been left feeling that I want more, but of course there is the question of head-room. Still the Marantz hasn't disappointed me in my listening environment/style. I've got others that are needing repair or I just don't like that are in the stable. The HK is the highest power I have, but to me it just sounds flat. I could give it a try though. Never set it up with the OLA's.

I've got that newer HK 3390 that I just don't like.

I've got an ST-70 that needs a total restore.

I've got a Heathkit AR-17 that needs a total restore.

I've got a Heathkit AR-13 that needs a total restore.

Just picked up a Knight KU-45 tube unit tonight. It works, but is dirty and need a rebuild

I've got a Yamaha CR-420

I've got a Superscope amp something or other (I think it's 10W/ch)

I've got a Technics amp that works fine, but is cheesey its got about 40W/ch.

I had given away a NAD 7000 receiver to a buddy of mine recently. That was a nice unit and I was trying to share.

 

 

 

IMG_2470.JPG

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Nice setup there,  Worth trying the HK especially when/if you try the BSC.

If the Marantz has a line out, perhaps just use the HK as a power amp going line in.

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6 hours ago, Pete B said:

Nice setup there,  Worth trying the HK especially when/if you try the BSC.

If the Marantz has a line out, perhaps just use the HK as a power amp going line in.

 

Sounds like a plan Pete. I'll go ahead and try the HK and make plans to build a BSC. The Marantz 2220B, doesn't have preamp outs, so I'll have to use the tape monitor. The 2220 without the "B" does, but oh well. I have to admit that I never understood what the tape monitor loop does. I'll figure it out though. Thanks very much for the help and responses!

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The tape out is for recording, it comes after the selector switch so that you record whatever

is selected but before the volume control so that changing the volume doesn't change the

record level, also before tone controls.  So you'd have to use them on the HK, the phono

section from it would work.  There is a loaner BSC if you are interested, PM me your address

if so.

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Pete B

Do not want to divert this thread but I have read before about your BSC box and was wondering does it do something more or perhaps different than what can be done with a 10 band or even 1/3 octave equalizer with regard to Advents?  

Adams

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Tim, thanks for posting the Xover pic.

I just finished a BSC and will test shortly.

Pete B, if the BSC is wired incorrectly or has a cold solder joint or whatever, what are the risks to the rest of the equipment?

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Since these are passive components in the BSC and also since it is in the low power input I would suspect that the risk is low, but let's see what Pete says.

 

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I agree with Tim D, if you start with it in a tape monitor loop then the volume control

can be brought up slowly just in case it produces hum or something.  You can debug

it then move it to where ever it was intended to go.

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Aadams yes you can use a graphic EQ.

It should be +3db at 500 Hz and + 6 dB on all sliders from about 100 Hz down.

If you only want 4dB of BSC then +2dB at 500 and +4 on all sliders from 100 Hz down.

And a smooth transition in between.

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