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Advent experiment - mod - much better sound IMO


Pete B

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Hi Steve,

The 2.2 ohm reading is just fine, mine measured 2.35 and Advent says approximately 2 ohms. If your curious it is good to also measure each of the drivers to see if they match and far off readings can indicate a problem. One thing to note is that the tweeter connections, on those old tweeters go through screws that you might want to make sure are clean and making good connections. You might have also noticed my comments about the switch:

http://www.classicspeakerpages.net/dc/dcbo...g_id=&page=#707

Remember that cleaning all these connections will bring the tweeter level up if there was corrosion and high resistance.

The most likely issue is that the ESR of the electrolytics has gone up with age and it is likely that the polys make the system sound more like it did when new.

First I suggest that with the speakers as currently wired you put your system in mono, put the speakers side by side, and use your balance control to switch between the two.

Do they sound the same?

If they do we can leave one as is and wire the poly back up but with a 1 ohm resistor in series to simulate the ESR that you prefer. It would be best to bring out the connections so that you can try different resistor values in order to match the reference speaker. Use music that your familiar with, interstation FM noise, or test CDs. Try the poly alone but this time compare against the other speaker with the electrolytic still in place - do you still hear a large difference?

New electrolytics typically have about .2 to .3 ohms of ESR and this is just about 10% of the 3 ohm decrease resistor, so it is not that significant but probably is barely audible.

I'd be willing to measure the electrical frequency response of the network with the electrolytic, and the poly in order to determine the best way to address your question, are you in CT or nearby by any chance?

Let me comment that you now have a hybrid of Rev1 and Rev2, to complete the Rev2 upgrade you need a low DCR, .45 mH inductor in place of the old 2.2 ohm red dot type. It is true that the difference is only in the extended position and even the hybrid is better than the original.

Pete B.

>Hi Pete,

>

>I replaced the capacitors in my large Advents with Bennic

>polys from Madisound: 16uF for the C1 capacitor and 8uF for

>the C2 “increase” capacitor that was previously 16uF. While I

>was in there I disconnected the tweeter and measured the DCR

>of the L2 shunt inductor. It read 2.2 ohms in each speaker.

>Note: I don’t have the most accurate DMM so that could be off,

>but L2 is definitely not shorted.

>

>I replaced the caps in one speaker first and thought I liked

>the sound so I did the other speaker. After that is when my

>ears started to hurt. The speakers were incredibly harsh in

>all 3 switch positions. This setup truly sounded like a

>transistor radio with a subwoofer. And, if I was listening to

>a weak FM station, i.e., one with a little background static,

>it was unbearable.

>

>Undaunted, I left the caps in place over the weekend to see if

>it was just me being overly sensitive. By last night my

>soldering iron couldn’t heat up fast enough. I put my original

>16uF electrolytics back in. I left the 8uF caps in place for

>now since I usually listen to these speakers in the “normal”

>position.

>

>Anyway, I’m at a loss. I don’t have a capacitance tester so I

>can’t verify the Bennics but they are marked as 16uF and

>physically they are about twice the size of the 8uFs. Further,

>after heating up the electrolytics twice now to

>desolder/solder them I’m really concerned about their

>reliability.

>

>Ideas and comments are appreciated.

>

>Thanks,

>Steve

>

>

>

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Guest esmachers

Hi Pete,

I think I'm taking this thread off track. I think the cap upgrade issue is useful information in itself so I'll start a new thread so this doesn't get buried.

Please keep an eye out for my new thread.

Thanks so much,

Steve

>Hi Steve,

>

>The 2.2 ohm reading is just fine, mine measured 2.35 and

>Advent says approximately 2 ohms. If your curious it is good

>to also measure each of the drivers to see if they match and

>far off readings can indicate a problem. One thing to note is

>that the tweeter connections, on those old tweeters go through

>screws that you might want to make sure are clean and making

>good connections. You might have also noticed my comments

>about the switch:

>

>http://www.classicspeakerpages.net/dc/dcbo...g_id=&page=#707

>

>Remember that cleaning all these connections will bring the

>tweeter level up if there was corrosion and high resistance.

>

>The most likely issue is that the ESR of the electrolytics has

>gone up with age and it is likely that the polys make the

>system sound more like it did when new.

>

>First I suggest that with the speakers as currently wired you

>put your system in mono, put the speakers side by side, and

>use your balance control to switch between the two.

>Do they sound the same?

>

>If they do we can leave one as is and wire the poly back up

>but with a 1 ohm resistor in series to simulate the ESR that

>you prefer. It would be best to bring out the connections so

>that you can try different resistor values in order to match

>the reference speaker. Use music that your familiar with,

>interstation FM noise, or test CDs. Try the poly alone but

>this time compare against the other speaker with the

>electrolytic still in place - do you still hear a large

>difference?

>

>New electrolytics typically have about .2 to .3 ohms of ESR

>and this is just about 10% of the 3 ohm decrease resistor, so

>it is not that significant but probably is barely audible.

>

>I'd be willing to measure the electrical frequency response of

>the network with the electrolytic, and the poly in order to

>determine the best way to address your question, are you in CT

>or nearby by any chance?

>

>Let me comment that you now have a hybrid of Rev1 and Rev2, to

>complete the Rev2 upgrade you need a low DCR, .45 mH inductor

>in place of the old 2.2 ohm red dot type. It is true that the

>difference is only in the extended position and even the

>hybrid is better than the original.

>

>Pete B.

>

>

>>Hi Pete,

>>

>>I replaced the capacitors in my large Advents with Bennic

>>polys from Madisound: 16uF for the C1 capacitor and 8uF for

>>the C2 “increase” capacitor that was previously 16uF. While

>I

>>was in there I disconnected the tweeter and measured the DCR

>>of the L2 shunt inductor. It read 2.2 ohms in each speaker.

>>Note: I don’t have the most accurate DMM so that could be

>off,

>>but L2 is definitely not shorted.

>>

>>I replaced the caps in one speaker first and thought I liked

>>the sound so I did the other speaker. After that is when my

>>ears started to hurt. The speakers were incredibly harsh in

>>all 3 switch positions. This setup truly sounded like a

>>transistor radio with a subwoofer. And, if I was listening

>to

>>a weak FM station, i.e., one with a little background

>static,

>>it was unbearable.

>>

>>Undaunted, I left the caps in place over the weekend to see

>if

>>it was just me being overly sensitive. By last night my

>>soldering iron couldn’t heat up fast enough. I put my

>original

>>16uF electrolytics back in. I left the 8uF caps in place for

>>now since I usually listen to these speakers in the “normal”

>>position.

>>

>>Anyway, I’m at a loss. I don’t have a capacitance tester so

>I

>>can’t verify the Bennics but they are marked as 16uF and

>>physically they are about twice the size of the 8uFs.

>Further,

>>after heating up the electrolytics twice now to

>>desolder/solder them I’m really concerned about their

>>reliability.

>>

>>Ideas and comments are appreciated.

>>

>>Thanks,

>>Steve

>>

>>

>>

>

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  • 4 weeks later...

I don't know if this question has been asked yet or not, but is there someone that will make these circuits for the electronically challenged? Time, effort and materials would gladly be compensated. Thanks. Or are they are fairly easily made with a soldering gun? I have two pair of New Large Advents that I want to stack.

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Thank you Russ for offering to help jackfish.

jackfish, it's not too difficult to build, I think it is a good soldering exercise if you like this sort of relaxing work. Let us know if you need more help or prefer to have someone else build it.

Pete B.

>I don't know if this question has been asked yet or not, but

>is there someone that will make these circuits for the

>electronically challenged? Time, effort and materials would

>gladly be compensated. Thanks. Or are they are fairly easily

>made with a soldering gun? I have two pair of New Large

>Advents that I want to stack.

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Russ recently asked me a good question in private e-mail as to why the original values for the 4.7K version are not the same as the values in the new tables that I posted.

This was my answer:

Basically, I did a back of the envelope calculation the first time and remember I said that the step would be slightly less than 6 dB. The chart values are derived from simulation where I take into account source and load impedance. If we look at the chart and do a rough interpolation we see that 4.7K for R2 falls between 5 and 6 dB just as we expected.

The cap value from the chart would be about .062 uF and I mentioned that the new values offer a slightly lower center for the step, 400 Hz vs. about 500 Hz IIRC, which explains why .047 uF was used in the original circuit.

You should be fine if you like the step size as it is.

You could experiment with .047, .056, .068 etc. if you like, to move the center of the step, I expect that the change will be very small since it is a gradual slope.

I'll just mention that I built the BSC for using AR-2ax's a few feet out from the wall behind them and elevated for better image height. It was a first cut and I was going to adjust as needed. There are no correct values since it is placement dependent. I should probably revisit this since I used early Advents with the 16/16 uF crossover and the extended setting was required with BSC. I didn't know that the Large Advent went through several revisions.

Based on what I know, I've not tested this yet, I'd build a new BSC from the tables as 5 dB for 16/16 uF Rev1 Advents used in the Extended position, and 4 dB with 16/8 uF Rev2 Advents also in the Extended position. Use the cap value in the chart but feel free to experiment with different values.

The "correct" value will depend on placement and many other factors, however any one mentioned above will be far better than the stock speaker, IMO.

Pete B.

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  • 4 weeks later...

Dave (Daveshel) writes:

>Pete, your baffle mod sounds interesting, and I my have to

>experiment with that. My preamp has an EPL that needs

>something to do. Although I may have accidentally achieved

>good baffle with my setup. My Advents (4 larges is 2 stacks)

>sit on stands that are 6" off the floor in the front and

>sloping down toward the back so that the speakers are at a few

>degrees off from vertical. And they are placed roughly

>20" from the wall. I have always loved their sound and

>was amazed at the synergistic effect when I added the second

>pair. Not boxy at all.

>

>Thanks, guys.

Yes there should be some synergy, the larger total baffle area should reduce the amount of required baffle step. There's also an efficiency gain when pairing up drivers.

Anyway, I'm wondering how your driving them, are they in parallel driven by a high current amp?

Have you tried the BSC circuit, I believe that it will help anyway and I believe Russ runs doubles with BSC and likes it.

You could try 3 to 4 dB if you prefer less or place them closer to the wall.

What version are your Advents, 16/16uf, 16/8 uf, or the New Adevent with a 13uF?

Have you tried any crossover upgrades, that we've talked about here?

Pete B.

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Guest daveshel

>Yes there should be some synergy, the larger total baffle area

>should reduce the amount of required baffle step. There's

>also an efficiency gain when pairing up drivers.

>

>Anyway, I'm wondering how your driving them, are they in

>parallel driven by a high current amp?

>

>Have you tried the BSC circuit, I believe that it will help

>anyway and I believe Russ runs doubles with BSC and likes it.

>You could try 3 to 4 dB if you prefer less or place them

>closer to the wall.

>

>What version are your Advents, 16/16uf, 16/8 uf, or the New

>Adevent with a 13uF?

>

>Have you tried any crossover upgrades, that we've talked about

>here?

>

>Pete B.

My amp is the AVA OmegaStar 170EX. The speakers are wired in parallel. I haven't gotten around to trying anything along the lines of a BSC or crossover upgrades (still digesting the science in this thread). I have three pairs (my original 'New' U4 that I bought in 1978, a U3 masonite ring and another U3 in the newer style).

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I'm fairly familiar with AVA but not by model number how many watts is that unit?

I don't follow your U4, U3 designation?

Masonite would be the early model, do you know if you have the 16/16 or the 16/8?

Newer style, do you mean The New Advent Loudspeaker ,what I call a Rev3 or 13uF?

I've given a strong recommendation above for Advents with BSC, it is easy to build and try seems the choice is obvious. However, you'd be wise to go over your Advents and at least replace the old caps.

Pete B.

>My amp is the AVA OmegaStar 170EX. The speakers are wired in

>parallel. I haven't gotten around to trying anything along the

>lines of a BSC or crossover upgrades (still digesting the

>science in this thread). I have three pairs (my original 'New'

>U4 that I bought in 1978, a U3 masonite ring and another U3 in

>the newer style).

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Guest daveshel

>I'm fairly familiar with AVA but not by model number how many

>watts is that unit?

>I don't follow your U4, U3 designation?

>Masonite would be the early model, do you know if you have the

>16/16 or the 16/8?

>Newer style, do you mean The New Advent Loudspeaker ,what I

>call a Rev3 or 13uF?

>I've given a strong recommendation above for Advents with BSC,

>it is easy to build and try seems the choice is obvious.

>However, you'd be wise to go over your Advents and at least

>replace the old caps.

>

>Pete B.

The 170EX is the upgrade for the Dynaco ST-120, and has 85 w/ch.

U3 and U4 are the first digits of the serial numbers. I don't know what you mean by 16/16 and 16/8.

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Can you tell us for each pair, do they have the masonite woofers, or all steel?

Do they have the orange tweeter with masonite, or are they the orange flush mount?

If you open them up, you should find:

Two 16 uF caps, early Large Advent, my Rev1

One 8 and one 16 later Large Advent, my Rev2

One 13uF cap, The New Advent Loudspeaker, my Rev3

Do any of them have "Designed by Henry Kloss" printed on the back?

Pete B.

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I don't expect you to open them if it wasn't in your plan, the rest of the info would help to determine what you've got.

>Can you tell us for each pair, do they have the masonite

>woofers, or all steel?

>Do they have the orange tweeter with masonite, or are they the

>orange flush mount?

>If you open them up, you should find:

>Two 16 uF caps, early Large Advent, my Rev1

>One 8 and one 16 later Large Advent, my Rev2

>One 13uF cap, The New Advent Loudspeaker, my Rev3

>Do any of them have "Designed by Henry Kloss"

>printed on the back?

>

>Pete B.

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  • 1 month later...

Here is a link to the frequency response of the Small Advent as measured by High Fidelity in the 1970s. Please note that Advent claimed that the Large and Small Advent were designed to have the same voicing, however the Small Advent was less efficient:

Please note that I did not scan this, the Small Advent is the first curve, the other two are unrelated:

http://members.aol.com/Debertin/spktwo.jpg

Pete B.

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  • 7 months later...

Some here ask about the large Advent sounding harsh:

The peaking in the dotted lined response starting at 500 Hz, peaking at 1.2 kHz, continuing to 5 kHz is one reason for harshness in the Advent sound. BSC helps to correct the response below 500 Hz, and combined with tweeter level adjustment makes a significant improvement in improving the FR balance.

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  • 1 year later...

Several people here have asked for a pictorial view of how to build the BSC.

I'm finally building one that looks nice, but it will have a few switches so

here's a pictorial layout that I've drawn in before wiring up the switches.

I built it from low cost parts from Radio Shack so that they'll be easy to

obtain.

Gold jacks, and a 1" X 2" X 3" plastic project box. Ground wiring is in green,

right channel in red, left in white:

http://baselaudiolabs.googlepages.com/BSC_PICTOR_CR.JPG

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Here's a loaner version of the BSC that I just built. Top and bottom

(for right and left) switches are 3 position BSC boost switches for 4, 5,

or 6 dB. Center switch allows for Flat or Boost on the high end. Boost

is more for the original Advent and Flat for new, however many listeners

will probably prefer Boost.

Here's a picture: http://baselaudiolabs.googlepages.com/BSC_SW_CR.JPG

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Here's a loaner version of the BSC that I just built. Top and bottom

(for right and left) switches are 3 position BSC boost switches for 4, 5,

or 6 dB. Center switch allows for Flat or Boost on the high end. Boost

is more for the original Advent and Flat for new, however many listeners

will probably prefer Boost.

Here's a picture: http://baselaudiolabs.googlepages.com/BSC_SW_CR.JPG

Hi Pete;

You did a very neat construction job of it.

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  • 2 weeks later...

Pete B, got your BSC hooked up today. First impressions are that this is a definite improvement. I have my bass, midrange and treble controls flat and the speakers set at normal. Voila! The bass is much improved, sounds better than when I had my bass control at 3 o'clock. The midrange is also much improved; smoother sounding yet very revealing of the nuances of the human voice or instruments like saxophones. And I think you are right about the high frequency boost you applied to this unit. Things also sound better with this boost employed. My ears need all the help they can get with high frequencies.

What is the schematic for this unit, with I believe the -6dB BSC and whatever high frequency boost you used? I don't need the switch to defeat the high frequency boost. Thanks much! As soon as I build mine (this weekend I hope) I will return it or pass it on if someone here expresses an interest to try it out next.

Stacked double New Large Advents rock with 200 watts per speaker and Pete's BSC!!!!!

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Pete B, got your BSC hooked up today. First impressions are that this is a definite improvement. I have my bass, midrange and treble controls flat and the speakers set at normal. Voila! The bass is much improved, sounds better than when I had my bass control at 3 o'clock. The midrange is also much improved; smoother sounding yet very revealing of the nuances of the human voice or instruments like saxophones. And I think you are right about the high frequency boost you applied to this unit. Things also sound better with this boost employed. My ears need all the help they can get with high frequencies.

What is the schematic for this unit, with I believe the -6dB BSC and whatever high frequency boost you used? I don't need the switch to defeat the high frequency boost. Thanks much! As soon as I build mine (this weekend I hope) I will return it or pass it on if someone here expresses an interest to try it out next.

Stacked double New Large Advents rock with 200 watts per speaker and Pete's BSC!!!!!

Good to hear! For me Advents just "lock in" with BSC.

Let me offer a bit more about my motivation here. My parents bought a pair

of the early Large Advents around 1972 or 73. We did some detailed spec and

review comparing, my brother being highly analytical (2 years into an EE degree

at the time) and having an excellent ear.

We got them after a listening demo, because of the good price and excellent

performance. My brother pointed out the flaw in the midrange when we got them

home after we did some extended listening. And I reluctantly agreed with him,

eventually strongly agreeing. I thought as a young teen that someday I'll try to

figure out what caused the problem. I expected it to be a complex woofer cone

resonance problem or serious crossover issue, that most likely couldn't be fixed

without a new driver. It was logical to think that the smart guys at Advent would

have fixed it if it was possible.

Now years later, I intended to dig into them when I took my parents' speakers to

refoam them. I decided to quickly try the BSC (I had built the BSC for AR-2ax's

that I was listening to out in the room) and was shocked by how it seemed to

completely fix the midrange issue. It was hard to tell the difference between the

Advents with BSC and my commercial reference system at moderate listening

levels, very hard.

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.

Have you tried different settings of the tweeter control? Where do you like it best?

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Good to hear! For me Advents just "lock in" with BSC.

Let me offer a bit more about my motivation here. My parents bought a pair

of the early Large Advents around 1972 or 73. We did some detailed spec and

review comparing, my brother being highly analytical (2 years into an EE degree

at the time) and having an excellent ear.

We got them after a listening demo, because of the good price and excellent

performance. My brother pointed out the flaw in the midrange when we got them

home after we did some extended listening. And I reluctantly agreed with him,

eventually strongly agreeing. I thought as a young teen that someday I'll try to

figure out what caused the problem. I expected it to be a complex woofer cone

resonance problem or serious crossover issue, that most likely couldn't be fixed

without a new driver. It was logical to think that the smart guys at Advent would

have fixed it if it was possible.

Now years later, I intended to dig into them when I took my parents' speakers to

refoam them. I decided to quickly try the BSC (I had built the BSC for AR-2ax's

that I was listening to out in the room) and was shocked by how it seemed to

completely fix the midrange issue. It was hard to tell the difference between the

Advents with BSC and my commercial reference system at moderate listening

levels, very hard.

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.

Have you tried different settings of the tweeter control? Where do you like it best?

As I may have mentioned somewhere posting here that I've had my New Large Advents since 1980 that I purchased when I got a new stereo after several years without. What influenced me was a trip to the stereo store in 1974 with a friend when he bought a new stereo and got original Large Advents, an amazing 30 wpc Sony receiver and an AR XA turntable. With his setup I never really noticed the midrange problem perhaps because he had them almost flush against the wall so there were less baffle issues. Of course all I had it to compare to were my own BIC Venturi Formula 4 speakers driven by a 28 wpc Sansui reciever and sourced from an old Fairchild turntable with Thorens arm, a friend's Bose 901s powered by Phase Linear 400 and another's Altec Lansing Voice of the Theaters powered by Dynaco tube stuff. Then I worked with a guy who introduced me to stacked double original Advents driven by a Phase Linear 700. I thought then that that had to be about the ultimate. In 1980 I bought New Large Advents with some new Harman Kardon gear and they have stuck with me all this time. It was just within the last couple of years that I decided to put together a kickass vintage stereo around stacked double Advents. I ended up refoaming my Advents and getting four more pairs, one pair of U4s to match mine, two pairs of U3s that needed some work, and a pair of beautiful mint A4s. I had never really identified the midrange issue until I decided to put Advents out into the room. Over all this time I've always considered the Advent a pretty flat speaker and have treated it that way by setting the tweeter switch on Normal rather than Extended or Decrease. As I listen to more varied sources on my system with the BSC in place I am amazed that it could make such a difference. Whew! Sorry about the longwindedness.

Pete, I will gladly accept your spare components and will wait to build my circuit until they arrive. I found a deal on some very nice gold plated RCA jacks at the local Mom and Pop electronics store and have had the box for several weeks. The place is pretty funny, looks like he has stuff in there about as old as he is. Thanks again Pete.

Is this right?

bscpictorcrer6.jpg

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Is this right?

Not even close huh? I think I might have the capacitors and resistors mixed up.

Yes, the long skinny things were meant to be the resistors

but it doesn't really matter, they are electrically in the same

position. Just swap Rs and Cs and it's fine. Parts are on the way.

Here are pictures of the fixed version that I sent you:

http://baselaudiolabs.googlepages.com/BSC_FIXED_TOP.JPG

http://baselaudiolabs.googlepages.com/BSC_FIXED_BACK.JPG

This is a really poor perspective as it makes the ground and center RCA terminals

look connected, they are obviously not:

http://baselaudiolabs.googlepages.com/BSC_FIXED_CLOSE.JPG

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