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BSC vs Shelving


Carlspeak

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Pete Basel's Advent BSC mod thread has garnered a great deal of interest with many posts and views. Recently, I had the need to tame some 'hissiness' in a new DIY speaker project and ended up with a simple shelving network that worked out just fine.

I decided to compare the frequency response characteristics of a personally built BSC I reported on in Pete's thread with the afore-mentioned shelving network.

Background: Pete's network is designed to act like an equalizer to tame the highs a given amount (adjustable with component changes) over a given frequency band and operates at the line stage level between a receiver's pre-out and amp-in functionalities. Whereas, the shelving network is wired in series just ahead of the loudspeaker xover (after the reciever's output). The BCS circuit is a bit complicated to assemble but non-the-less, is very effective once the right combination of components is chosen.

The shelving network, OTOH, is comprised of a coil inductor and resistor connected in parallel with each other and the assembly is wired in series either before or after the positive input terminal of the loudspeakers.

Below is a response test done on a NLA loudspeaker comparing 1) no response shaping networks 2) BCS @ line stage and 3)shelving network comprised of a 0.7 mH coil with a parallel 6 ohm resistor.

The test shows both response shaping networks do indeed alter the frequency response from the 'normal' switch setting in somewhat different ways.

1) The no network test shows an elevated response in the 2 kHz to 12 kHz range. This characteristic may not be pleasing to some who desire a bit more mid-bass and midrange.

2) The BSC network I used reduces the response in the 200 to 8 kHz range with a rise up to even with the 200-300 range level at about 12 kHz. I agree with Pete regarding the more pleasing sound from the BSC altered response.

3) The shelving network doesnt affect the response until about 1 kHz and then slopes it downward and ending up with a more moderate upturn in the 12 kHz range. The start of the response change from no network is affected by the inductor value and the degree of dB drop is tuned by resistor ohm level chosen. With this circuit one can also use a L-Pad in place of a single resistor to provide more continuous adjustment of the shelf. I didn't listen to the shelving network for any extended time, but found it also pleasing at first blush.

Some might ask: Which is the 'better' network? IMO, the answer is - it depends & YMMV. Each network has advantages and disadvantages with respect to construction difficulty and performance and, as such, I recommend the hobbyist review the alternatives and find out which they'd rather build and then fine tune the response shape to suit listening tastes. If you decide to go the shelving the network route, I strongly suggest you use an air core coil and good quality resistor.

post-100237-1284753658.jpg

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  • 2 months later...

Thanks Z for the clarification. Sorry I forgot to spell out what BSC stood for :)

Yup, like I also wrote: act's like an equalizer......

Hi Carl.

Can you tell me what components you used for the BSC circuit? I'm correcting for 14.75 and 4.75 ohms. That's 6dB and a bit much I think.

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Hi Carl.

Can you tell me what components you used for the BSC circuit? I'm correcting for 14.75 and 4.75 ohms. That's 6dB and a bit much I think.

Hi Les.

See posts # 103 and 133 in this much more expansive thread:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2692&st=120

Below is a picture of my BSC build. Just be sure you correctly identify whch direction the signal flows in. If you have it hooked up backwards, it won't provide the EQ.

post-100237-0-82782700-1291254633_thumb.

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Hi Les.

See posts # 103 and 133 in this much more expansive thread:

http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2692&st=120

Below is a picture of my BSC build. Just be sure you correctly identify whch direction the signal flows in. If you have it hooked up backwards, it won't provide the EQ.

thanks Carl. Did I not see a post of yours using a 10K pot to vary the dB loss?

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Baffle Step Compensation (BSC) is the step filter you describe:

http://www.trueaudio.com/st_diff1.htm

Pete's "BSC" is more like an equalizer with the well-known "smiley face" transfer function:

Zilch, when are you going to stop your self promotion?

Do you really think that my mod competes with your Econo-wave?

I say this because the "smiley face" EQ pattern is generally

frowned upon and thought of as the disco sound - that EQ curve has

most of the HF boost full on by 7 or 10 KHz where it is highly

audible for most people.

My BSC curve has at most 5 dB of boost at 20 KHz where most adults

have strong attenuation - indeed many members say they can hear no

difference with the HF boost on or off.

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Zilch, when are you going to stop your self promotion?

Post your version of the transfer function, and we might discuss it further. Carl's measurements suggest that I've got it right, which has occurred on multiple occasions in this forum.

I don't view this as a matter of "competition," rather, merely exposition of fact. Stuff is what it is, and there is value in knowing exactly what, is all. If others believe in magic, it'll not be on my account.

You grant that it is not merely BSC, yet you continue to call it that. In the interest of your own integrity, at least put that in quotes.... ;)

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Post your version of the transfer function, and we might discuss it further. Carl's measurements suggest that I've got it right, which has occurred on multiple occasions in this forum.

I don't view this as a matter of "competition," rather, merely exposition of fact. Stuff is what it is, and there is value in knowing exactly what, is all. If others believe in magic, it'll not be on my account.

You grant that it is not merely BSC, yet you continue to call it that. In the interest of your own integrity, at least put that in quotes.... ;)

What is annoying is that you question my integrity with no basis

for such an assertion - I did all the BSC work for free, LOL!

You often suggest that there is some flaw with what I have

offered, implying that you have a better idea. I have offered

that the BSC can be built with or without the HF boost, in that

case it would just be BSC. However, there is more going on even

when you just use BSC and it involves psychoacoustics. So, don't

bother telling me what I should or should not quote simply because

you do not have a full understanding of what is going on. And, no

I'm not going to explain it to you.

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  • 2 months later...

Hi Pete

I have briefly just returned to the internet, to enjoy CSP.

What a lot I have missed in each section.

I hope that you and your's are well.

This circuit of yours is an idea that I will be looking more at as I

become more stable in my home.

I have been off most of the past few years now.

It left me reading time, time to read old literature and

various reviews.

Each pointed out that there seemed to be an issue around the crossover

frequency but never did anyone suggest an update or alteration to it.

Your simple circuit appears to have worked aqround that issue, I believe.

I look forward to reading all of your writings here when I am better able to.

Thank you very much, Pete, for all your effort.

Vern

dynaco_dan@hotmail.com

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Hi Vern,

Very nice to hear from you again and thanks for the encouragement!

All the best to you and your family also, we have 2 teens that

keep us busy!

I hope you try it and let us know what you think, either way

hope you enjoy your system!

Do you still have your LSTs?

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Hi Pete

Sadly I can only say, yes, I still have only 2 pairs of LST's.

I was extremely lucky that not one speaker in my home was even touched by

water leaking through my roof.

It was very expensive to have the proper job done with the leaking roof.

My daughter said to me recently, dad, some of your speakers must go.

My kid's do not have any interest in my stereo equipment.

I rescued way too pieces over the years to where it was time they be donated.

There were many pairs of Larger Advents, AR 14's, EPI 100's, Smaller Advents and

a few other brand speakers that I recently donated, 40 in total to be exact.

Those that really know me, know that I never bought or received as a

gift, never were they ever rescued for re-sale of any kind.

For the time being I have kept some raw drivers, also my LST's, KLH Twelves, Larger Walnut Advent's,

Dynaco A-10's, A-25's, A-35's, A-50's, a few AR's and NHT Super Zero's.

I guess I had too much idle time on my hands back a few years ago.

Recently I read somewhere that The Double Advent Speaker demonstration that was written up in,

The Absolute Sound, had the speakers cabinets vertical, one above the other, tweeter to tweeter.

Here in Vancouver I only ever saw the exclusive Advent retailer demo them side by side, vertical, tweeters up.

Sadly the AR-3A's next to them on stands as well, had dead tweeters, both of them.

To the lay person, they would not have guessed that.

The AR-3A's even without their tweeters put up quite a good battle against The Larger Advents.

I am looking forward to trying out your circuit.

Also I just read your lengthly Larger Advent article of 2008, great job, well done, Pete.

Vern

dynaco_dan@hotmail.com

Hi Vern,

Very nice to hear from you again and thanks for the encouragement!

All the best to you and your family also, we have 2 teens that

keep us busy!

I hope you try it and let us know what you think, either way

hope you enjoy your system!

Do you still have your LSTs?

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Vern it sounds like you still have a lot even after giving away 40!!!

I've actually been trying to push to finish projects here because so

many systems are piling up in just about every room in the house, lol!

I don't recall ever hearing stacked Advents but I'm sure they are

quite impressive, especially for low cost systems.

I have a loaner 6 dB fixed BSC that only costs a few bucks to ship if

you'd like to try it. It was returned from the last person many months

ago and is just sitting around so no problem if you'd like to try it.

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Hi again Pete

Yes, I would appreciate tryng out your circuit, Pete, thank you very much.

I still have way too much hifi equipment here.

A 5.1 or 7.1 speaker system for my kid's would include only

the tiny little fist sized Bose speakers with subwoofer.

AR-4x's and Dynaco A-25's are far too large for them.

In fact they think they are ugly.

I do have a small pair of Bose speakers, but they are too large

for them.

I don't have the information at hand right now, but I have seen

the Dynaco multi-speaker setups with series and parallel wiring.

I will be able to check out the differences in sound between the Seas and

Scan A-25's in the very near future, I hope.

With my lower level of hearing, I may not be able to tell the difference now.

The Absolute Sound named them the, "Double Advent" speaker system when they reviewed them

in their first issue.

I have a copy for you via email if you would like it.

Have a great day, Pete.

Vern

dynaco_dan@hotmail.com

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