Advent crossovers and schematic

[Wally]

Has anyone designed or bought a new crossover for the Larger Advents that will flatten the response and reduce that mid range?

Also does anyone have a schematic for the Large Advents.

Last, has anyone compared the Large Advents, Dynaco A25's, McIntosh ML1C's and similar sized AR's like an AR5 for example. How would you describe the sound of each?

regards, Wally

[Guest russwollman]

Hi, Wally. As an indirect answer to your question about the Advent's response, you might try making the little circuit Pete B descibes in his earlier post on this board, titled "Advent experiment - mod - much better sound IMO".

It doesn't require much to make and it may do the trick for you.

I have given up comparing speakers for the 50-60 odd years remaining in my lifetime.

There's a looney bin somewhere in Britain full of guys who spent 'way too much time comparing speakers. I heard they allowed nothing but Advents!

[Guest palomar]

Wally,

I've never heard the McIntosh, and I've never compared the Large Advent directly to the AR2ax or AR5. And I've never owned any of them. Now that I have totally disqualified myself as a reliable judge, let me nonetheless chime in with my two cents worth.

The ARs (both the 2ax and 5) have always sounded smoother in the midrange to me than the Advents. At low volumes, the ARs and Advents can sound a bit dull. But when you turn up the volume, the ARs seem to come alive, whereas the Advents seem to start getting too bright in the upper middles.

The Advents, as I recall, did go deeper than either of the two ARs mentioned. (I believe it went about as deep as the AR3a, although Tom Tyson mentioned in another post - Tom, please correct me if I am wrong - that the Advents were no match for the 3a's woofer at high volumes.)

I did own a pair of Avent 1's (I think that was the model). It was basically the Large Advent drivers in a slightly smaller cabinet. (I don't know if the crossover was the same. I don't recall mine having the three-way tweeter-level switch, but I don't know if there were other differences.)

I found that I could smooth out the middle and tighten up the bass a bit by discarding one or two of them foam blocks, and re-arranging the rest of them so that they simply lined the cabinet. The other thing I did was bypass the coil in the crossover.

The tradeoff was that the low-end was not quite as deep and clean. It was still quite good, but there is never any free lunch.

Gay

[Wally]

Hi Russ,

Found the article. I'll try it as soosn as I get the parts.

Thanks and I'll report back on reults when it's done.

Wally

>Hi, Wally. As an indirect answer to your question about the

>Advent's response, you might try making the little circuit

>Pete B descibes in his earlier post on this board, titled

>"Advent experiment - mod - much better sound IMO".

>

[Wally]

Gay,

I have the Large Advents, Dynaco A25's and ARLST's among others.

The Advents have the deepest bass right now but the AR's woofers were subber with 10's on an adapter ring so they're not quite right.

The AR's definitely have the smoothest mid range and high end. The Advent is a bit peaky in the upper mids and the Advents have a bit of a harsh high end ..... observations so far.

Working on the AR's to get them sounding up to snuff....

regards, Wally

>Wally,

>

>I've never heard the McIntosh, and I've never compared the

>Large Advent directly to the AR2ax or AR5. And I've never

>owned any of them. Now that I have totally disqualified myself

>as a reliable judge, let me nonetheless chime in with my two

>cents worth.

>

>The ARs (both the 2ax and 5) have always sounded smoother in

>the midrange to me than the Advents. At low volumes, the ARs

>and Advents can sound a bit dull. But when you turn up the

>volume, the ARs seem to come alive, whereas the Advents seem

>to start getting too bright in the upper middles.

>

>The Advents, as I recall, did go deeper than either of the two

>ARs mentioned. (I believe it went about as deep as the AR3a,

>although Tom Tyson mentioned in another post - Tom, please

>correct me if I am wrong - that the Advents were no match for

>the 3a's woofer at high volumes.)

>

>I did own a pair of Avent 1's (I think that was the model). It

>was basically the Large Advent drivers in a slightly smaller

>cabinet. (I don't know if the crossover was the same. I don't

>recall mine having the three-way tweeter-level switch, but I

>don't know if there were other differences.)

>

>I found that I could smooth out the middle and tighten up the

>bass a bit by discarding one or two of them foam blocks, and

>re-arranging the rest of them so that they simply lined the

>cabinet. The other thing I did was bypass the coil in the

>crossover.

>

>The tradeoff was that the low-end was not quite as deep and

>clean. It was still quite good, but there is never any free

>lunch.

>

>Gay

[Pete B]

Hi Wally,

Just wondering which version of the Large Advent you have?

Do yours have the woofer with the masonite ring?

I was very interested in the Large Advent when it first came out but never followed the changes and history. I was not aware that there were several versions of the Large Advent until coming to this site. There is a schematic on this site that seems to be correct for the 8 uF (not sure what to call these) Large Advents, the only difference from the earlier version is that the "increase" cap is 16 uF in the earlier version rather than 8 uF as shown. Both of these versions have the masonite ring woofers and say designed by Henry Kloss on the back. I have the version with 16 uF cap which were used in the listening test with the BSC circuit.

I now also have a pair of the later Large Advents which do *not* say designed by Henry Kloss on the back and do not have the woofer with the masonite ring. These newer woofers have the foam edge facing out. There were quite a few changes to this later Large Advent. The tweeter is still the redish orange color but flush mounts and does not have the prototype look with the masonite board. The new tweeter has ferro fluid, and probably a shorter voice coil former since less area is needed for cooling. It sounds more extended to me in direct A/B comparisions probably as a result of the lower moving mass. I've taken a quick look at the crossover and it is completely different. The box is stuffed with what looks like foam rubber pading which I believe should be replaced with fiberglass. I plan to work on these as soon as I find the time.

The baffle is set back 1 1/8" in the early Large Advents and only .5" in the newer version. This is allowed by the flush mounting of the updated tweeter.

These are the versions I know of that all use the redish orange "donut" tweeter. I don't know if there are any other versions.

Regards,

Pete B.

[Guest palomar]

Wally,

I have to apologize for mis-typing my name. I'm Gary. I make my share of typing mistakes, but this is the first time I recall messing up my own name. I just hope my hearing is better than my typing.

Incidently, I've also listened to Dynaco A25s. I never owned them, but I did own a pair of A35s. I felt both of them were also smoother in the midrange than the Advents. However, I felt that the A35 lacked deep bass. (My recollection - which is dimming with time - of hearing the A25s is that I preferred their low end. Maybe not as tight as the A35, but deeper.)

I think that the on-axis midrange of the dynacos was in fact superior to that of the ARs, but that the ARs had better low end (especially the 3a), and a more extended and well dispersed high end.

There was probably a near-field effect going on here which tended to favor the dynaco midrange, in that the dynaco woofer and tweeter seemed to blend together better than the other speakers, but my listening room was only about 12 x 10 with an 8 foot ceiling, so I wasn't that far from the speakers.

Gary

[Wally]

Pete, Gary,

The Advents I have are the larger wood veneer cabinets with the rounded front not bevelled. The Woofer is the allsteel frame and the orange tweeter is indeed flush mounted. No mention of Henry Kloss on the back. A pair of utility cabinet models I just sold had metal frame woofers but the tweeters were indeed raised off the front baffle. Don't remember any Henry Kloss on those either.

These have a decent low end but I find something exaggerated in the upper mid range so I would like to build a xover or equalizer to flatten that peak out.

The Dynacos I revcently acquired have no model number on them and I believe they are A25XL's because the tweeter is center mounted and slightly smaller dome than the original. The back only says DYNACO Blackwood New Jersey. The tweeter control is a pot, not a switch and the grille cloth, which looks original is brown, not beige linen.

Thes I find a little harsh in the high end when the pot is in the 'normal' position. The bass is clean but much leaner than the advents.

regards, Wally

[Pete B]

>The Advents I have are the larger wood veneer cabinets with

>the rounded front not bevelled. The Woofer is the allsteel

>frame and the orange tweeter is indeed flush mounted. No

>mention of Henry Kloss on the back. A pair of utility cabinet

>models I just sold had metal frame woofers but the tweeters

>were indeed raised off the front baffle. Don't remember any

>Henry Kloss on those either.

It's in small print near the input terminals - easy to miss.

>These have a decent low end but I find something exaggerated

>in the upper mid range so I would like to build a xover or

>equalizer to flatten that peak out.

I think you might like the BSC circuit that was mentioned earlier, you might want to experiment with the tweeter level, "normal" was better with the later Large Advents that you have as I recall. I'd be very curious to hear what you think of the difference.

I considered designing a crossover change to incorporate the BSC but was looking for more feedback on the line level circuit before investing the time. Still waiting on feedback.

Regards, Pete B.

[Wally]

I will try that circuit. Waiting till I need more parts before I place an order to reduce shipping costs. Your BSC circuit... does it do the same thing as the MQ 101 1nd 102 equalizers did with the first series of McIntosh speakers?

regards, Wally

>

>I think you might like the BSC circuit that was mentioned

>earlier, you might want to experiment with the tweeter level,

>"normal" was better with the later Large Advents that you have

>as I recall. I'd be very curious to hear what you think of

>the difference.

>

>I considered designing a crossover change to incorporate the

>BSC but was looking for more feedback on the line level

>circuit before investing the time. Still waiting on

>feedback.

>

>Regards, Pete B.

[Guest russwollman]

Wally, I was listening tonight to Sylvia McNair, a soprano, along with a piano accompaniment.

With the BSC circuit removed from the signal, the piano was annoyingly harsh, almost unlistenable.

Pete can explain in technical terms what his creation does. What I notice is that it makes the Advents more refined and subtle, nicely reducing the irritating harshness that becomes noticeable at higher volumes. I have a double Advent system and lots of amp power (150/ch), but it was all wasted power until I added the BSC circuit.

The good things about Pete's idea are:

1. It is very inexpensive and easy to make.

2. It creates no permanent change to your existing system.

3. It is switchable, so you can make the choice.

4. It produces no adverse effects that I have noticed except for a wee bit of hum with the volume control 'way up with no audio signal.

The great simplicity of the BSC circuit is impressive (although it does require the use of one of the preamp's tape loops or external processor loop). I like simple, inexpensive solutions, and I balk at the price of high-end audio.

I just wanted to give you some idea of the effects of the circuit and what I see as its unique advantages.

[Wally]

Russ,

Thanks for the feedback and impressions of this mod. I'm anxious to try it. Unfortunately I sold one pair of Advents to friend. I remeber when we had a pair in the 70's so we both wanted to recapture some of that old nostalgia.

When i get it done, I'll give you my impressions and comparison to the dynacos, AR LST's and Celestion Ditton 10's.

I agree with you. I like the idea that it's an external circuit that can be switched in and out through the processor loop.

regards, Wally

>Wally, I was listening tonight to Sylvia McNair, a soprano,

>along with a piano accompaniment.

[Pete B]

>I will try that circuit. Waiting till I need more parts before

>I place an order to reduce shipping costs.

Last I checked the parts are available at most Radio Shacks as an alternative. Film caps, mylar is fine, should be used.

>Your BSC circuit...

>does it do the same thing as the MQ 101 1nd 102 equalizers did

>with the first series of McIntosh speakers?

This is an interesting question, basically no.

It's interesting that if you take a bookshelf speaker and bury it in the ground facing up so that it radiates into half space and compare the frequency response to it under anechoic conditions, it will gradually roll off by 6 dB from 1kHz down to 100 Hz. The minus 3 dB point is usually around 400 to 500 Hz. Most of this loss is also seen when the speaker is pulled out from the rear wall and elevated to about ear level for the typical audiophile listening position. The BSC provides 6 dB of compensation to flatten the response. The system will see boundary reinforcement at very low frequencies where the distance to the boundaries is small compared to the wavelength, this boost usually starts around 80 Hz.

The MQ 101 and 102 EQ units are designed to fix or realign the overdamped LF response of the speakers that they're used with. They made the amount of boost adjustable claiming that this would correct for room placement. This adjustment will probably help in some situations but the amount of baffle step should also change and is more important.

The Advents are not an overdamped system so those EQ units would not be a good fit.

[Wally]

PETE,

DID YOU EVER DESIGN AN ACTIVE VERSION OF THIS CIRCUIT TO COMPENSATE FOR THE FILTER LOSSES?

WHAT IS THE FUNCTION OF THE PARALLED RESISTOR AND CAP? I'M GUESSING THAT THE SERIES ONES TO GROUND DO THE BSC COMPENSATION BY FILTERING OFF THE MIDS/HIGHS?

DOES YOUR CIRCUIT COMPENSATE FOR THE UPPER MID BOOST THAT NEW ADVENTS SEEM TO HAVE?

SORRY IF YOU COVERED THIS IN YOUR ORIGINAL LETTER ABOUT THIS CIRCUIT.

REGARDS, WALLY

>This is an interesting question, basically no.

>It's interesting that if you take a bookshelf speaker and bury

>it in the ground facing up so that it radiates into half space

>and compare the frequency response to it under anechoic

>conditions, it will gradually roll off by 6 dB from 1kHz down

>to 100 Hz. The minus 3 dB point is usually around 400 to 500

>Hz. Most of this loss is also seen when the speaker is pulled

>out from the rear wall and elevated to about ear level for the

>typical audiophile listening position. The BSC provides 6 dB

>of compensation to flatten the response. The system will see

>boundary reinforcement at very low frequencies where the

>distance to the boundaries is small compared to the

>wavelength, this boost usually starts around 80 Hz.

>The MQ 101 and 102 EQ units are designed to fix or realign the

>overdamped LF response of the speakers that they're used with.

> They made the amount of boost adjustable claiming that this

>would correct for room placement. This adjustment will

>probably help in some situations but the amount of baffle step

>should also change and is more important.

>The Advents are not an overdamped system so those EQ units

>would not be a good fit.

>

[Pete B]

Hi Wally,

No I did not design an active version, it would be a simple almost trivial design. The cap in parallel boost the very high end above about 10 to 15 kHz to compensate for rolloff in the early tweeter (with masonite board). You can leave out the parallel cap if you have the later flush mount tweeter. Yes the series connection to ground is the shunt leg of the BSC, you also need the input resistor. It provides a shelved down response of the mids and highs if that's what you meant and yes it compensates for the "upper mid boost" that most large Advents seem to have.

Pete B.

>PETE,

>

>DID YOU EVER DESIGN AN ACTIVE VERSION OF THIS CIRCUIT TO

>COMPENSATE FOR THE FILTER LOSSES?

>

>WHAT IS THE FUNCTION OF THE PARALLED RESISTOR AND CAP? I'M

>GUESSING THAT THE SERIES ONES TO GROUND DO THE BSC

>COMPENSATION BY FILTERING OFF THE MIDS/HIGHS?

>

>DOES YOUR CIRCUIT COMPENSATE FOR THE UPPER MID BOOST THAT NEW

>ADVENTS SEEM TO HAVE?

>

>SORRY IF YOU COVERED THIS IN YOUR ORIGINAL LETTER ABOUT THIS

>CIRCUIT.

>

>REGARDS, WALLY

[Wally]

>Hi Wally,

>

>No I did not design an active version, it would be a simple

>almost trivial design. The cap in parallel boost the very

>high end above about 10 to 15 kHz to compensate for rolloff in

>the early tweeter (with masonite board). You can leave out

>the parallel cap if you have the later flush mount tweeter.

>Yes the series connection to ground is the shunt leg of the

>BSC, you also need the input resistor. It provides a shelved

>down response of the mids and highs if that's what you meant

>and yes it compensates for the "upper mid boost" that most

>large Advents seem to have.

>

>Pete B.

Thanks Pete. I'm putting together parts list for a few projects and I'll include these mod parts. I have some op amps kicking around here.. have to find some little boards like Radio Shack used to have for making small circuits. Ha... maybe I'll make this mod a switchable part of one of the IC-150's that I'm modding...

regards, Wally

[Pete B]

Hi Wally,

I remember the IC-150 never saw a schematic though.

I was intending for the BSC to be a test circuit, but building it in is also fine. I'm starting to think that an EQ unit with variable BSC, high pass (subsonic filter) filter with adjustable boost, and a Linkwitz transform (LT) filter might be interesting.

Might want a few parametric channels also.

Pete B.

>

>Thanks Pete. I'm putting together parts list for a few

>projects and I'll include these mod parts. I have some op amps

>kicking around here.. have to find some little boards like

>Radio Shack used to have for making small circuits. Ha...

>maybe I'll make this mod a switchable part of one of the

>IC-150's that I'm modding...

>

>regards, Wally

[Wally]

>Hi Wally,

>

>I remember the IC-150 never saw a schematic though.

THE IC150 IS NOTORIOUS FOR BEING VERY HARD AND BRIGHT SOUNDING. I HAVE MODIFIED AN IC150 AND AN IC150A SUCESSFULLY IMHO. I REPLACED ALL THE ELECTROS WITH NEW UNITS. INCREASEDTHE PS CAPS X10. REPLACED TANATALUMS WITH LOW ESR ELECTROS. REMOVED CERAMIC CAPS. REPLACED THE LINE LEVEL IC'S WITH BURR BROWN OPA604'S. THE LINE SECTIONS NOW SOUND AT LEAST AS GOOD AS MY HAFLER DH110. ANYWAY I JUST GOT MY 3RD IC150 AS A PARTS UNIT BUT IT IS COMPLETE BUT HAS A POWER SUPPLY PROBLEM. IN ANY CASE I WILL BE UPDATING IT AND MODDING IT AND WILL INSTALL YOUR ADVENT CKT. THE BEAUTY OF THESE PRES IS THAT THEY ARE WELL MADE AND THE CHASSIS HAVE PLENTY OF ROOM FOR MODDING ETC. THEY HAVE AN EXTERNAL PROCESSOR LOOP BUILT IN.

THAT WON'T HAPPEN NOW TILL LATER IN THE SUMMER AS I'M IN THE PROCESS OF MOVING. LOOKING FORWARD TO TWEAKING WHEN IGET RE-ESTABLISHED.

REGARDS, WALLY

>I was intending for the BSC to be a test circuit, but building

>it in is also fine. I'm starting to think that an EQ unit

>with variable BSC, high pass (subsonic filter) filter with

>adjustable boost, and a Linkwitz transform (LT) filter might

>be interesting.

>Might want a few parametric channels also.

>

>Pete B.

[longdrive03]

Pete and all,

I know this is an old thread but thought I would ask some questions.

I've replaced crossover components on LA and NLA in the past along with veneering the cabinets and finishing for resale.

I just bought a pair of Advent 1 speakers at an estate sale.  Everything works except the woofer surrounds are toast which I will refoam tonight.

I understand the woofer and tweeter in Advent 1 are the same as in the NLA???  The Advent one only has one coil, a 13uf NPE and a 1Ohm resistor.

I will recap and replace the 10 ohm resistor.  Not sure what the value is on the coil or the dcr but may replace those as well.  

Looks like I could go with one of the early versions of the crossover with the switch and more components.  Or should I stay with the current plan and replace the cap and resistor and maybe the coil?  

I plan on building a LA size new cabinet and veneering with ribbon mahogany  or walnut with solid front trim and new grills and cloth attached with magnets.

Thanks.

 

Longdrive03 (Ken)  

[Pete B]

The only "correct" crossover is the "New Large Advent" NLA crossover on this page:

http://baselaudiolab.com/ADVENT_LA_XO.html

The Advent/1 is an NLA in a smaller box.

If you build the version with a switch you might want to up each resistor by 1 ohm or

try the BSC circuit.

[Analogman]

On 4/29/2005 at 3:54 PM, Wally said:

Has anyone designed or bought a new crossover for the Larger Advents that will flatten the response and reduce that mid range?

Also does anyone have a schematic for the Large Advents.

Last, has anyone compared the Large Advents, Dynaco A25's, McIntosh ML1C's and similar sized AR's like an AR5 for example. How would you describe the sound of each?

regards, Wally

Install a couple of L-pads on the back for the mids and tweeters

(I also realize this is an ancient thread as well! : - )

If that doesn't solve your complaints you can always fill the holes with dowels and let the speakers remain (put them back by just moving a few wires) as designed, i.e. 100% reversible with no damage whatsoever to your cabinets

Low time and materials cost, may make you happy and the L-pad approach is a minimally intrusive, cheap, no harm no foul approach

Will also allow for tuning "around" your room's limitations/impositions as well as your own personal preferences - same as any good monitor

I'd try that first (and have, many times) before I re-invented the wheel and started rolling dice on "new and improved" networks and "mods" sound unheard

[Analogman]

On 5/7/2018 at 11:07 AM, longdrive03 said:

Pete and all,

I know this is an old thread but thought I would ask some questions.

I've replaced crossover components on LA and NLA in the past along with veneering the cabinets and finishing for resale.

I just bought a pair of Advent 1 speakers at an estate sale.  Everything works except the woofer surrounds are toast which I will refoam tonight.

I understand the woofer and tweeter in Advent 1 are the same as in the NLA???  The Advent one only has one coil, a 13uf NPE and a 1Ohm resistor.

I will recap and replace the 10 ohm resistor.  Not sure what the value is on the coil or the dcr but may replace those as well.  

Looks like I could go with one of the early versions of the crossover with the switch and more components.  Or should I stay with the current plan and replace the cap and resistor and maybe the coil?  

I plan on building a LA size new cabinet and veneering with ribbon mahogany  or walnut with solid front trim and new grills and cloth attached with magnets.

Thanks.

 

Longdrive03 (Ken)  

Replace your surrounds, change the electrolytic for a film type and leave the balance of the parts alone

There is absolutely no need to change either the cement wirewound or the coil

None

Craig