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Advent Evolution

75.185.134.22
Posted on June 25, 2015 at 11:10:31
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 It has been a while since I posted here; so I thought to bring you all up to date on what I have been doing.

I have gotten very tired of replacing foam surrounds on my Advents and those of my relatives. So I have searched for an alternative woofer that's as good or better. Also, over time, I have replaced the original Advent tweeters. First, with the New Advent tweeter; and later with the SEAS 27TBFC/G.

The woofer that did the trick was the newer SEAS A26RE4. It's T-S parameters make it suitable for an Acoustic Suspension cabinet; and like the Advent woofer, it rolls off smoothly and naturally without needing a low pass filter. The earlier SEAS 25F-EW woofer is not suitable for Acoustic Suspension. All well and good; but the Advent woofer cut out is too large for the SEAS, the Advent woofer being built on a 12" pincushion frame. Since I wanted to be able to return to using Advent components, I needed to adapt the SEAS woofer to the mounting holes for a 12" pincushion frame. My solution was to cut the magnet structure off of a pair of derelict Advent woofers I had. The Masonite ring bonded to the frame is almost the right diameter to act as the mounting flange for the SEAS - all I had to do was notch the ring to clear the legs on the SEAS frame and transfer the six mounting holes. The result is an assembly that bolts in like an Advent woofer.

The crossover for the speaker is a simple first order high pass filter for the tweeter. For that I used a 10 uF Clarity PX capacitor and an 8 ohm adjustable L-pad. Although there is no low pass filter for the woofer, I did add a 0.47 ohm resistor in series with the woofer to get the desired Qts in the low bass, and to extend the bass a little. The cabinets were each filled with 2 lbs of Acousta-stuf. That much filler gives too low a bass Q; but prevents internal reflections and standing waves in the midrange, so the series R was needed.

OK, so how does it sound? Very smooth and natural. Vocals are very life-like, and all instruments are accurately presented. Transients and percussives are noticeably better than the Advent drivers. That's often accompanied by edgy highs in many speakers; but that's not the case here. The sound stage is wide with excellent imaging - partly due to the cabinets having mirror image tweeter locations. Bass is very similar to the Advent woofers, although mid-bass is a little fuller and that shows up as a better "groan" on bowed bass and cello. Baritone voices do not get chesty.

The idea behind this project was to build a speaker using the same sort of minimalist construction as many speakers of the '60's and early 70's (Advent, Dynaco A-25, EPI, KLH, Bozak, JBL's L-100, etc.); but using modern drivers.

I now have 3 pair of speakers like this. The Advents described above, a pair of 38 liter ported cabinets using the SEAS 25F-EW woofers and SEAS 27TBFC/G tweeters, and a pair of KLH 17's with the original woofers and Morel MDT-20 tweeters. In all three there is no low pass filter on the woofer and only a series cap for the tweeter. Later this year, the KLH 17's will receive SEAS 27TDFC tweeters, the soft dome version of the 27TBFC/G metal dome model.

Anyone wishing to try this needs to realize that there are almost no modern woofers that are suitable. Madisound claims the SEAS A26RE4 is the only current one they know of that can be used without a low pass filter. A number of older 8" and 10" woofers work well (Advent, EPI, KLH, etc.).

There are several suitable tweeters - the requirements being a low resonant frequency (650 Hz on the SEAS I used), high power handling, enough stroke to prevent overload, and very smooth response. There are several choices here.

Is it worth the effort? I think so. There's something about the sound from speakers like this that I don't get from newer speakers with complex crossovers and especially with several smaller woofers with severe breakup modes.

Jerry

 

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RE: Advent Evolution, posted on June 25, 2015 at 15:26:13
Diogenes
Audiophile

Posts: 315
Joined: February 17, 2014
 I have a hammer that my Father bought in 1940. Every few years I replace either the handle or the head.

 

Good to know...., posted on June 25, 2015 at 15:29:50
Uncle Mike
 Glad your back.

 

RE: Advent Evolution, posted on June 25, 2015 at 18:46:48
tedk.
Audiophile

Posts: 401
Location: chicagoland
Joined: July 7, 2004
Wow!
You must be a real hammerhead!

 

RE: Advent Evolution, posted on June 25, 2015 at 19:48:44
Satxhifi
Audiophile

Posts: 185
Joined: July 4, 2010
 Jerry,
Really good post. Like you, i like the sound of 2-ways. Just something about them. I have some AR 7s and like them very much. Ditto the A 60s and A 70s (SEAS tweeters)I have. I've had some other 2-ways too, but one that really stands out for e was the Audio Physic Step. They were an original pair. Suffice it to say an amazing speaker. Kicking myself I let them go.

I am interested in what you think of the soft-dome when you try them. I am partial to soft-domes myself. In fact I could say I prefer the sound of paper, silk, etc. cones/domes, anything made with a naturally occurring substance, over that of metal, plastic, etc. Am I a granola? :0)? NOT to say there are not metal, etc. speakers that don't sound good. I can certainly appreciate both. Just have noticed this to be the preference if I have my druthers.

Pretty good solution for the mounting problem. Keeping the original integrity a plus. I certainly do not possess the knowledge and experience you have, but I would like to build some speakers. Certainly go to learn more, but something I'd love to do!

Thanks for a great post and making me think about this.
Best,
Dave

 

RE: Advent Evolution, posted on June 25, 2015 at 19:53:52
Satxhifi
Audiophile

Posts: 185
Joined: July 4, 2010
 Something I forgot to ask, is there a replacement rubber surround with the same properties as the foam surrounds suitable for acoustic suspension? You probably would have tried it if it was the case.

 

RE: Advent Evolution, posted on June 26, 2015 at 06:30:37
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Maybe too lazy; but no, I have not researched that. Now that I am where I want to be, this might be a good time to check that out, as I have nothing to lose if it doesn't work out well. I do have a spare pair of Advent woofers I could try it on.

Jerry

 

RE: Advent Evolution, posted on June 26, 2015 at 06:41:10
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 In the SEAS tweeters, the 27TDFC (soft dome) and the 27TBFC/G have very similar properties and are pretty much interchangeable. I have tried the soft dome version in the Advents with the Advent woofer and thought it lacked a little "life". If you look at the SEAS data sheets, the metal dome has a little flatter response, and a little better dispersion. The"/G" on the metal dome denotes a guard over the dome, and on the inside of the guard is a clear plastic dot that acts to increase dispersion. It does have a dome resonance; but it's well above 20 kHz and should not be audible.

I'll try the soft domes with the A26RE4 woofers and post my results.

Jerry

 

RE: Advent Evolution, posted on June 26, 2015 at 06:42:23
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Right on! LOL

Jerry

 

Now you need a name for your creation!, posted on June 26, 2015 at 08:00:04
E-Stat
Audiophile

Posts: 37666
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 I think I related the story that HP heard my double Advents about ten years ago and wished they had addressed some of the basic problems with the design.

You have effectively created a Twenty First Century Advent keeping the inherent goodness of a 10" two way while addressing the challenges:

1. Brace cabinet to reduce resonances
2. Eliminate the edge diffraction
3. Modernize and simplify wiring and crossover
4. Extend usable response at the top another half octave

I trust you kept the New Advent crossover spec (and the Seas recommendation) at 1.5 kHz?

 

RE: Advent Evolution, posted on June 26, 2015 at 08:18:20
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Welcome back Jerry. I am familiar with that woofer as the latest iteration of the replacement woofer for Dynaco A-25. It is great that it works for the Advent cabinet too. It may be time for you to DIY a cabinet. (I am not sure if you are into that!) I was wondering what would be optimal for that driver. I know your not into tubes, but your resulting speaker should be an easy load for a tube amp. Vintage transistor amps should work great. Have you created the Asylum speaker?

Dave

 

RE: Now you need a name for your creation!, posted on June 26, 2015 at 08:27:07
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 5. Sell the Advents with their original drivers and build you own cabinets.

Dave

 

I think they are custom!, posted on June 26, 2015 at 08:38:03
E-Stat
Audiophile

Posts: 37666
Joined: May 12, 2000
Contributor
  Since: April 5, 2002
 It's been years since I visited his lair, but I seem to recall that they were not stock. Hence his having addressed the diffraction issue.

 

RE: Advent Evolution, posted on June 26, 2015 at 10:00:40
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Dave,

It's nice to be back! I missed you guys; but I was into other hobbies and didn't have a lot to say.

No, I'm not into woodwork. In fact, I can't be. First, I live in a condo with no place to work; and secondly, I discovered about 30 years ago, that I'm allergic to sawdust. So, I repurpose good quality, existing enclosures. My Advent cabinets are actually replicas made for me by Kirby Gaal. The madisound web site says 1.5 cubic feet for a sealed box. That's based on a Qts of 0.7. I prefer a little peak in the bass with a slightly higher Q of around 0.8 to 0.85. The Advent cabinets are 1.6 cubic feet, and I wanted heavy fill to kill reflections and standing waves. That would reduce the Q to less than 0.7, so the series resistor was added to raise the Q.

I found that removing the small inductor in a New Advent actually reduces the bass a little too much, and I needed to add the value of the coil's DCR back in to get the bass right. Use of super low DCR coils can be a negative thing, depending on the bass tuning. The JBL L-110 uses an air core coil with a DCR of 0.6 ohms. Going to an iron core coil with lower DCR torpedoed the bass.

As configured, the speakers are optimized for my Rotel RB-1050 & NAD C350, both direct coupled SS amps. With tubes, I'd first take out the series R on the woofer, as the source impedance of a good tube amp is about that value. I'd probably also have to fiddle around with the cap on the tweeter.

Jerry

 

RE: Now you need a name for your creation!, posted on June 26, 2015 at 10:16:37
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 I had to raise the crossover slightly as the SEAS woofer rolls off a little higher than the Advent woofer. I also used an L-pad for adjustment instead of the Advent's switched resistors and that lowers the total circuit impedance, so the cap value needs to be changed for that as well. So, instead of the new Advent's 13 uF non-polar electrolytic, I used a 10 uF film cap. Anything larger than 10 uF causes a bump in the midrange and makes the sound too forward.

Normally, that would cause the woofer to become more directional; but the A26RE4 woofer has a curved cone that decouples the outer part of the cone below roll off and effectively reduces the radiating diameter at the crossover point. That makes the transition smoother, and the little higher frequency makes it a bit easier on the tweeter. The Advent cone is straight sided.

My impression is that the SEAS/SEAS system is more coherent than the New Advent.

Jerry

 

RE: Now you need a name for your creation!, posted on June 26, 2015 at 12:59:57
FRG7SWL
Audiophile

Posts: 2109
Location: NorCali
Joined: March 26, 2003
 Welcome back, Bold Eagle! Glad you're enjoying your New Millennium Advents. Still rockin' Utility Advents, with Brown Soun-reconed Masonite woofs, for nearly a decade now. Replacement stock tweets were $125 each, compared to $75 per for updates. Replaced tweet x-over caps with Dayton 12 uf poly-props. 16 gauge wiring, with no chokes or coils. Simply sounds delightful with music-n-home theatre presentation. ... If you'd like to experiment with relatively in-expensive hemp coned drivers, try Jensen's Jet Falcons. Bought a 10" pair to replace some Mesa/Jensen P10RIs moi oopsed. Was surprised to hear how they damn near replicated P10RIs when broken in. Read of a similar alnico-esque experience on a guitar blog concerning 12" Jet Falcons. ... For in-expensive 8" replacement drivers for auld-skool wood cabs, try either Jensen's 8-ohm Mod 8-20 or Celestion's 8-ohm G8C-15(Eight-Fifteen). 73s para Sactown

 

RE: Advent Evolution, posted on June 26, 2015 at 13:51:19
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Hi Jerry,

You solved the DIY issue. You had someone else do it themselves. You talked about using a series resistor to raise the Q of a speaker many times. It sounds like you really have this one fine tuned.

Dave

 

RE: Advent Evolution, posted on June 29, 2015 at 09:27:49
spons
 I really like the idea of re-using vintage Advent or similar cabinets.

What other makes and models from the 60's and early 70's would work well with the SEAS A26RE4 and 27TBFC/G? Is the only requirement an internal volume of about 1.8 cubic feet for a sealed box?

 

RE: Advent Evolution, posted on June 29, 2015 at 10:09:10
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Madisound calculated 1.5 cubic feet to get a Q = 0.7. Anything close to that would be OK. The Advents are 1.6 cubic ft. So various AR's using the 10" woofer, KLH 6 or 23, Advents up into the 5002, models from ADC, Fisher, Scott, Marantz, etc. Lots of solid boxes with older drivers around. You could also use a ported cabinet if you close the port and fill the cabinet with Acousta-stuf or fiberglass.

A bigger box will lower the Q, a smaller one will raise it and raise the Fb, the in-box resonant frequency.

The frame on the A26RE4 is a little bigger than the usual 10"; so it won't fit into the recess for a standard 10" and you'd need to be handy with a router. If the original woofer mounted to the front of the baffle and the hole is close, it would be a lot easier. Adapting the SEAS woofer is where ingenuity comes in.

Jerry

 

RE: Advent Evolution, posted on June 29, 2015 at 10:55:38
mark.korda@myfairpoint.net
Audiophile

Posts: 1253
Location: Maine
Joined: August 16, 2011
 Hi Bold Eagle, I know Advents were beautiful and sold thousands,but when you look at the Advent tweeter side by side with the Seas it's like looking at a Ferrari and a Yugo, the Seas being the Ferrari. Glad you went with the better innards...Mark K.

 

RE: Advent Evolution, posted on June 29, 2015 at 12:18:35
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Mark,

Thanks. It took me a while to break down and spend the money. The fact is that tweeter technology was still not very good in the late 60's and early 70's. Laser holography was the tool that finally allowed them to see what was happening. Before that, everyone was trying different approaches to try and get smooth response, good power handling, wide dispersion, and that could reach low enough to make a good two way. Henry Kloss's Advent tweeter was one of the better ones at the time. A lot of companies were still using cone tweeters.

I don't know if it's still true; but by the later '70's, the Advent had the largest sales volume of any speaker in terms of number of units. The JBL L-100 had the record for dollar volume. They sounded good, they measured well, they had nice looking cabinets, and they didn't cost a lot. The utility model was $102 each in 1970 and the walnut veneer was $114.

But time and technology move on and I have decided not to fight it any longer. I think I pushed what was possible with Advent drivers about as far as was practical. Advents first hit the stores at the end of 1969. That was 46 years ago this coming Fall.

Jerry

 

Gonna build a pair for my office..., posted on July 7, 2015 at 07:19:19
spons
 I want to put a pair of these together to replace the Fisher XP-1's in my office.

I have been on the lookout for vintage cabinets to re-use, but all the good cabinets I have found contain speakers too nice to sacrifice.

So I have decided to build my own cabinets. Do you have plans that your cabinet guy works from?

 

RE: Gonna build a pair for my office..., posted on July 7, 2015 at 07:37:55
Bold Eagle
Audiophile

Posts: 6936
Location: America's Heartland
Joined: May 27, 2001
 Sorry, I don't have plans. I loaned him an Advent cabinet to measure and duplicate. He made an exact copy from that.

Jerry

 

RE: Gonna build a pair for my office..., posted on July 7, 2015 at 08:22:17
spons
 Thanks for the reply. I'm sure there are plans out there somewhere in some DIY forum.

 

RE: Gonna build a pair for my office..., posted on July 7, 2015 at 08:24:51
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001
 Do you live near Washington DC? There was a pair of large Advents in the NAMI thrift store in Rockville, the last time I was there. Dynaco A-25 cabinets should work great too.

Dave

 

RE: Advent Evolution, posted on July 7, 2015 at 17:07:36
ejman
Audiophile

Posts: 403
Location: SW Oregon
Joined: October 3, 2006
 So if I understand correctly, this is a write up about a speaker that uses a non Advent cabinet, that uses a non Advent woofer and a non advent tweeter, with a non Advent crossover. What exactly is the the relation to Advent speakers?

 

The starting point! (nt), posted on July 23, 2015 at 09:00:05
Crazy Dave
Audiophile

Posts: 14371
Location: East Coast
Joined: October 4, 2001

 

RE: Gonna build a pair for my office..., posted on September 21, 2015 at 07:36:20
spons
 I have decided to use my XP-1 cabinets. Can you recommend a source for the SEAS drivers and other stuff (caps, wire, pots, resistors, binding posts)?

 

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