Advent BSC switch?

[Carlspeak]

I'm working with a st'd Advent metal frame woofer and no internal XO. So, I can do whatever is needed externally to affect BSC. The original Advents simply use a 1.6 mH coil in series and no paralleled resistor. Was that to tame a 1-2 kHz peaking? or for BSC? or both?

I've played around with a 1.5 mH air core coil with a paralled 4 ohm resistor. It rolls off the response above 1 kHz like I would expect but I don't see any impact on the response below 300 hz using Holmimpulse.

I may try today using PE's acoustic meas. system where I can add & subtract the woofer's BSC circuit and see in real time the impact on FR.

What I'd really like to do is not have ANY coil in series with the woofer but am concerned I'll sacrifice some of the bass response due to a loss of BSC.

[Pete B]

I'm working with a st'd Advent metal frame woofer and no internal XO. So, I can do whatever is needed externally to affect BSC. The original Advents simply use a 1.6 mH coil in series and no paralleled resistor. Was that to tame a 1-2 kHz peaking? or for BSC? or both?

I've played around with a 1.5 mH air core coil with a paralled 4 ohm resistor. It rolls off the response above 1 kHz like I would expect but I don't see any impact on the response below 300 hz using Holmimpulse.

I may try today using PE's acoustic meas. system where I can add & subtract the woofer's BSC circuit and see in real time the impact on FR.

What I'd really like to do is not have ANY coil in series with the woofer but am concerned I'll sacrifice some of the bass response due to a loss of BSC.

I'm able to measure the electrical transfer function so that's what I'd do to figure out what's going on. The inductor alone gives some BSC assuming the driver does not have a rising response that counteracts it and it adds to the VC inductance to lower the natural roll-off of the woofer. We know that the LA has too much output at 1 KHz even with that inductor so I'm not sure what to say. I did design a completely new crossover for the NLAs but it was a quick afternoon project and I don't remember the details. I don't even remember where I put the schematic for it and I'll have to open it up and trace the crossover. I did not simulate, just did it iteratively with measurements. I'm probably going to make it public at AK soon.

I used an inductor and R-C to ground to the woofer, this gives roughly 2nd order electrical combined with the acoustical response probably ends up roughly 4th order. If you have to wire the drivers in phase to not null then it is probably about 4th order, out of phase for no null then about 2nd order. I ended up with in phase as I recall.

[Carlspeak]

I spent some time yesterday with my P.E. Omnimic system. The FR curve I got was quite similar to the Holmimpulse FR. The advantage of the Omnimic is that is plays a repeating signal whilst I can examine the resultant FR changes, if any, on my computer in real time as opposed to the H.I. system that does one scan and I essentially get a 'snapshot' of the FR.

With my wife's help switching the BSC circuit (virtual XO box in use) in and out, I wasn't able to detect any significant difference in the overall FR using the 1.5 mH coil w/paralleled 4 ohm resistor, much to my surprise. With the tweeter out of the circuit the upper end of the woofer's respose was visably affected but still no apparent BSC was noted. I went as far as patching in a huge 2.75 mH coil with paralleled 10 ohm with not impact.

So, the question remains, how is the woofers FR affected by the BSC circuit (e.g. coil and parallel resistor)? I can't seem to measure it. My concern here is bass extension.enhancement via BSC.

Am I measuring wrong? mic is about 1/2M on axis for most of the trials I've described. I did try at one point moving it back to beyond 1M and again didn't notice any BSC changes switching it in and out of the circuit.

I fully understand how the woofer's FR dips in the 3-6 dB range below 300 hz with baffle step loss with generally narrow front baffle boards. That loss is prevented with wide BB designs like those used by Snell, Audio Note and others. However, I'm still struggling with how that loss is recovered with the use of fairly high mH inductors in series with the woofer.... can't measure or hear it.

[Joel]

Ok, I give up. I've looked all over and followed this thread. What is a BSC switch?

-Joel

[Carlspeak]

Ok, I give up. I've looked all over and followed this thread. What is a BSC switch?

-Joel

The OP said he was going to buiid one of Pete's Baffle Step Compensation circuits but realized with his system he needed to be able to essentially turn it off from time to time. The basic BSC design does not include a switch. So, therein followed the others suggestions on how to put a switch into the circuit.

[Pete B]

Ok, I give up. I've looked all over and followed this thread. What is a BSC switch?

-Joel

Read here: http://www.audiokarma.org/forums/showthread.php?t=647441

[Pete B]

I spent some time yesterday with my P.E. Omnimic system. The FR curve I got was quite similar to the Holmimpulse FR. The advantage of the Omnimic is that is plays a repeating signal whilst I can examine the resultant FR changes, if any, on my computer in real time as opposed to the H.I. system that does one scan and I essentially get a 'snapshot' of the FR.

With my wife's help switching the BSC circuit (virtual XO box in use) in and out, I wasn't able to detect any significant difference in the overall FR using the 1.5 mH coil w/paralleled 4 ohm resistor, much to my surprise. With the tweeter out of the circuit the upper end of the woofer's respose was visably affected but still no apparent BSC was noted. I went as far as patching in a huge 2.75 mH coil with paralleled 10 ohm with not impact.

So, the question remains, how is the woofers FR affected by the BSC circuit (e.g. coil and parallel resistor)? I can't seem to measure it. My concern here is bass extension.enhancement via BSC.

Am I measuring wrong? mic is about 1/2M on axis for most of the trials I've described. I did try at one point moving it back to beyond 1M and again didn't notice any BSC changes switching it in and out of the circuit.

I fully understand how the woofer's FR dips in the 3-6 dB range below 300 hz with baffle step loss with generally narrow front baffle boards. That loss is prevented with wide BB designs like those used by Snell, Audio Note and others. However, I'm still struggling with how that loss is recovered with the use of fairly high mH inductors in series with the woofer.... can't measure or hear it.

I would try a continuous test tone at about 1 KHz, this is a free software generator:

http://www.marchandelec.com/fg.htm

I think you are aware that actually BSC cuts the highs/mids so that relatively the bass is boosted.

With 1 KHz tone playing you should hear it being attenuated as you go from 0 to 1.5 mH or more

to the woofer. Leave out the resistor to start, then add the resistor back in if you end up needing

it. If you set the generator to 500 Hz you should hear less of a change and hardly any at 100 Hz.

We are off topic by the way to everyone else.

[Joel]

Pete,

Thanks for the link- I think I'm up to speed now.

-Joel

Read here: http://www.audiokarma.org/forums/showthread.php?t=647441

[Carlspeak]

I would try a continuous test tone at about 1 KHz, this is a free software generator:

http://www.marchandelec.com/fg.htm

I think you are aware that actually BSC cuts the highs/mids so that relatively the bass is boosted.

With 1 KHz tone playing you should hear it being attenuated as you go from 0 to 1.5 mH or more

to the woofer. Leave out the resistor to start, then add the resistor back in if you end up needing

it. If you set the generator to 500 Hz you should hear less of a change and hardly any at 100 Hz.

We are off topic by the way to everyone else.

Yes, my apologies for going OT. So, the attenuation is solely at the upper end of the woofer's FR in the 1 khz range.

Now that does make sense and I was able to measure that.

thanks

[Pete B]

Keher, did you get the BSC box, please let us know.

Here is the new thread on AK: http://www.audiokarma.org/forums/showthread.php?t=647441

Note that it is normal to have to turn you volume up higher completely normal and

not a strain for your amp. The extra voltage comes from the preamp.

[kehern15]

I apologize for the late reply, I have been busy with work. Yes I received the BSC and have been listening to it the past few days, it is excellent! I'm not too good at describing sound, but I will try.

Overall I found the speakers to become much more balanced with the BSC. The highs are more audible and clearer, but not ear piercing as they could have been before. For me that has been the best improvement. The bottom end seems to have gotten louder and a bit looser, but that is probably because 6dB is a bit much for me, my speakers are only 8 in from the wall, so I am getting a lot of room boundary enhancement. The mids seem more seemless now, before I could sometimes tell when a song was around the crossover point of the two drivers, but with the BSC it is more natural and effortless.

I'm probably going to build the 4dB version then, seems appropriate given the speakers current placement.

Has anyone measured the frequency response with the BSC and compared it to stock speakers? Would just be curious.

One question Pete, where do you recommend the HF switch to be when using the BSC? I had it to extended, but normally I have it to Normal or Decreased.

[Carlspeak]

Has anyone measured the frequency response with the BSC and compared it to stock speakers? Would just be curious.

Check out post #133 here.... http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2692&page=7

[Pete B]

I apologize for the late reply, I have been busy with work. Yes I received the BSC and have been listening to it the past few days, it is excellent! I'm not too good at describing sound, but I will try.

Overall I found the speakers to become much more balanced with the BSC. The highs are more audible and clearer, but not ear piercing as they could have been before. For me that has been the best improvement. The bottom end seems to have gotten louder and a bit looser, but that is probably because 6dB is a bit much for me, my speakers are only 8 in from the wall, so I am getting a lot of room boundary enhancement. The mids seem more seemless now, before I could sometimes tell when a song was around the crossover point of the two drivers, but with the BSC it is more natural and effortless.

I'm probably going to build the 4dB version then, seems appropriate given the speakers current placement.

Has anyone measured the frequency response with the BSC and compared it to stock speakers? Would just be curious.

One question Pete, where do you recommend the HF switch to be when using the BSC? I had it to extended, but normally I have it to Normal or Decreased.

I also usually run it Extended with the full 6 dB, you might find Normal to work better when you run with 4 dB.

The switch gives you some adjustment range so that helps match it to your room.

I'll try to get the amp-speaker level build instructions up soon.

I've never measured Large Advents acoustically, I just tried it and it was obvious to me that it worked and I

had never intended to spend so much time on Advents.

[kehern15]

Has anyone measured the frequency response with the BSC and compared it to stock speakers? Would just be curious.

Check out post #133 here.... http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=2692&page=7

Ah yes I thought I saw it somewhere! Just wasn't sure as I have read a lot of frequency graphs recently learning about speakers and headphones. If I'm reading that correctly, it's +/-5dB from 20hz to ~13khz? Pretty great for a 40+ year old speaker!

I also usually run it Extended with the full 6 dB, you might find Normal to work better when you run with 4 dB.

The switch gives you some adjustment range so that helps match it to your room.

I'll try to get the amp-speaker level build instructions up soon.

I've never measured Large Advents acoustically, I just tried it and it was obvious to me that it worked and I

had never intended to spend so much time on Advents.

I see, thanks for the advice. I think that I'd probably prefer it in the Normal position myself, I am fairly young (24) and have pretty good hearing (up to 18khz), those advent tweeters can be harsh.

Hm, in your little background story about creating the BSC and not being able to distinguish them from your reference speakers, did you not find yourself listening to the advents more? Just personally curious.

I probably won't be building the speaker-amp line BSC soon, but it would be very helpful for me (and others) for general reference (in the future I'll probably make one).

I'll be ordering the parts from Mouser soon, to build my own. Will make a quick post here and have you/whomever check my cart to ensure I am buying the correct parts before I order them.

Thanks again for creating this and all your help Pete, I am sure that many of us a very grateful!

[kehern15]

Alright I created my shopping cart, should be the same as the one JKent so kindly provided, with the values adjusted for 4dB. Could someone quickly double check to make sure I made no silly mistakes? Thanks again.

Slightly related, I was going to buy some banana plugs and some sort of terminal to use on the advents (ring, spade, etc) Does Mouser have any nice gold plated ones? I tried searching a few times, but couldn't find much. I was hoping to get speaker "quality" components (just meaning that they are heavier duty, gold plated, and attach via screw, not needing solder or crimping). Not sure if I just missed them or they don't have any.

[JKent]

Looks good to me, but then I've made mistakes on this before so I hope someone else (maybe Pete) will look it over.

I don't think Mouser caters to the "audiophile" market. For something like gold-plated bananas and terminals, check Madisound, Parts Conexxion, etc. or try ebay--there are several Chinese sellers who have that sort of thing at low prices.

-Kent

[Pete B]

The last person who had the BSC seems to have gotten a good selection

of parts. I'll ask him to post his list of parts.

Keher, you say that that response is +/- 5 dB? If you look at Carl's measurement each

division is 5 dB, and the top curve is without BSC, the redish curve is with and it fits within

one large division so that would be +/- 2.5 dB and if you take the 2 to 4 KHz dip as being

deliberate, then you might say that it is +/- 1.5 ignoring the deliberate response shaping.

But we are just playing with numbers here.

Normal vs. extended will depend on how strong your room's absorption is, depends on a

lot of things, right your young ears are a factor also.

If you read on the AK thread there is some high frequency boost also, that you can remove

by taking out a jumper inside the box, open the back and it should be obvious. It does not

make a huge difference at 10 KHz but if you have good hearing well above it might be too

much, I'm curious to hear what you think.

You ask about LA vs. our reference, I left the A/B setup connected for about a week, and I'd

just randomly leave it on A or B, then I'd work at my desk where I would listen and try to

guess which was playing, it was 50/50 I really couldn't tell. I'm sure if I only played some

very demanding tracks with very deep bass I'd probably have a much better chance of

picking correctly but it really was a toss up otherwise.

How would you compare the Overnight Sensations balance as compared to the Advents

with BSC?

[kehern15]

Looks good to me, but then I've made mistakes on this before so I hope someone else (maybe Pete) will look it over.

I don't think Mouser caters to the "audiophile" market. For something like gold-plated bananas and terminals, check Madisound, Parts Conexxion, etc. or try ebay--there are several Chinese sellers who have that sort of thing at low prices.

-Kent

Thanks! I'll give it a double check and order everything. Yeah I just figured I might as well order a few more things as I was already paying for shipping, was just making sure that I wasn't missing anything in their massive inventory of everything. I'll probably order from Monoprice soon. I remember you having some advents for a bit, did you ever use some sort of non bare wire termination? Not sure what to use as banana plugs don't fit on advents, and most angled spade adapters are $30+ (1/3 the price of the speakers!)

The last person who had the BSC seems to have gotten a good selection

of parts. I'll ask him to post his list of parts.

Keher, you say that that response is +/- 5 dB? If you look at Carl's measurement each

division is 5 dB, and the top curve is without BSC, the redish curve is with and it fits within

one large division so that would be +/- 2.5 dB and if you take the 2 to 4 KHz dip as being

deliberate, then you might say that it is +/- 1.5 ignoring the deliberate response shaping.

But we are just playing with numbers here.

Normal vs. extended will depend on how strong your room's absorption is, depends on a

lot of things, right your young ears are a factor also.

If you read on the AK thread there is some high frequency boost also, that you can remove

by taking out a jumper inside the box, open the back and it should be obvious. It does not

make a huge difference at 10 KHz but if you have good hearing well above it might be too

much, I'm curious to hear what you think.

You ask about LA vs. our reference, I left the A/B setup connected for about a week, and I'd

just randomly leave it on A or B, then I'd work at my desk where I would listen and try to

guess which was playing, it was 50/50 I really couldn't tell. I'm sure if I only played some

very demanding tracks with very deep bass I'd probably have a much better chance of

picking correctly but it really was a toss up otherwise.

How would you compare the Overnight Sensations balance as compared to the Advents

with BSC?

Thanks Pete. Ah excuse me, I quickly glanced at that. +/-2.5 is more accurate, and I see where you got +/-1.5, though from what I understand about the BSC, making mine with 4dB will make the 2-4kHz dip less dramatic? (ie less of a dB dip). Just trying to better understand how the BSC works/effects the speakers.

I saw the little snippet of info on the back of the BSC box, I didn't hear much of a difference. Admittedly, I didn't play with it for more than a minute or two, and probably not with music with many high notes, I'll give it a more thorough listen soon.

I found it hard to compare the OS and the Advents, after I had both working. The Advents just give off such a wider soundstage (the OS's do have a very surprisingly large soundstage themselves, they just aren't advents), and the advents have much more depth/weight in the deeper notes, so it nearly always sounds better to me. That being said, I do get surprised at how deep the OS's can get, from such small drivers/enclosures.

Those are the things that immediately notice, A/Bing back and forth I usually prefer the advents, but I have not taken much time comparing the balances of the two, was too busy enjoying the advents to compare! For what it's worth, I choose the advents 90% of the time, only really using the OS's later at night, as to not have deep bass notes disturbing my neighbor.

[JKent]

The Advents, like AR and KLH, used 8-32 machine screws with thumb nuts. The best connection for a fairly permanent installation is #8 ring terminals, which ARE available from Mouser--just not gold plated. For those who like banana jacks, you can make dongles with parts from Mouser, as discussed here http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8257&page=8

Here is a ring terminal for stud size 8, wire size 16 - 14 http://www.mouser.com/ProductDetail/Molex/19070-0071/?qs=sGAEpiMZZMvz8LftK4jersSbDVyEnl6qBwRnsSNNXRw%3d

Of course if your speaker wires look like garden hose it would be hard to find crimp connectors big enough but for regular 18, 16, 14 or even 12 AWD wire there are crimps that will work fine.

According to my technician and many others, the gold plating, while it looks nice, is really just cosmetic.

-Kent

[Pete B]

See next post.

[Pete B]

If your preamp can drive very low impedance loads then Kent's version will work.

If not you'll want to use a DPDT and do it like this:

The output goes to the center, then switches directly to the input without the shunt

to ground, or with it in the other direction:

[Pete B]

Are these the type of post you're asking about?

http://www.parts-express.com/dayton-audio-bpa-38g-hd-binding-post-pair-gold--091-1245

I prefer the hex head type but I don't see them at PE, like these:

https://www.madisoundspeakerstore.com/yung-binding-posts/posts-hg-postr-binding-post-red/

Be sure to space them properly if you want to use dual plugs with them and check the

thread length when you buy them to get the right ones.

[JKent]

If your preamp can drive very low impedance loads then Kent's version will work.

If not you'll want to use a DPDT and do it like this:

The output goes to the center, then switches directly to the input or what was

the old output:

Thanks Pete.

That's a better solution.

So you'll need a DPDT switch. This one should do http://www.mouser.com/ProductDetail/E-Switch/100DP1T1B1M1QEH/?qs=sGAEpiMZZMvudeGI7i40XHGaLhqsrql1BOBK5Q5Fgls%3d

-Kent

[Pete B]

Note that I updated post 46 with the switch, that is the best way to do it.

[kehern15]

The Advents, like AR and KLH, used 8-32 machine screws with thumb nuts. The best connection for a fairly permanent installation is #8 ring terminals, which ARE available from Mouser--just not gold plated. For those who like banana jacks, you can make dongles with parts from Mouser, as discussed here http://www.classicspeakerpages.net/IP.Board/index.php?showtopic=8257&page=8

Here is a ring terminal for stud size 8, wire size 16 - 14 http://www.mouser.com/ProductDetail/Molex/19070-0071/?qs=sGAEpiMZZMvz8LftK4jersSbDVyEnl6qBwRnsSNNXRw%3d

Of course if your speaker wires look like garden hose it would be hard to find crimp connectors big enough but for regular 18, 16, 14 or even 12 AWD wire there are crimps that will work fine.

According to my technician and many others, the gold plating, while it looks nice, is really just cosmetic.

-Kent

I mainly wanted gold plating for corrosion resistance, not fr any magical audio effect. I was going to pick up some simple ring terminals, but I also stumbled across this, do you think it would work/fit the advents? Couldn't find the equivalent ring size. http://www.amazon.com/Ariic-Adapter-Marantz-Mcintosh-Amplifier/dp/B00CRSQZF2/ref=sr_1_1?ie=UTF8&qid=1427141622&sr=8-1&keywords=banana+fork

If your preamp can drive very low impedance loads then Kent's version will work.

If not you'll want to use a DPDT and do it like this:

The output goes to the center, then switches directly to the input without the shunt

to ground, or with it in the other direction:

My preamp is a USB powered DAC, the Behringer UCA202. I am unsure if it can drive low impedance loads, for what it's worth, the only specs I could find on it's RCA outputs are: 400 ohms, and 2dBV max.

Are these the type of post you're asking about?

http://www.parts-express.com/dayton-audio-bpa-38g-hd-binding-post-pair-gold--091-1245

I prefer the hex head type but I don't see them at PE, like these:

https://www.madisoundspeakerstore.com/yung-binding-posts/posts-hg-postr-binding-post-red/

Be sure to space them properly if you want to use dual plugs with them and check the

thread length when you buy them to get the right ones.

No, I wasn't going to do anything extreme like replace the advents binding posts. Was just seeing if there was an easy way to terminate the speaker wire for attachment, I'm probably going to use a ring terminal, or those banana plug adapters I linked to in this post.