The New Advent Loudspeaker Review (Vintage Speaker)

[anmpr1]

... I immediately concluded that all this could actually accomplish is to allow the enclosure to be smaller than a tightly sealed enclosure would need to be with the given driver, thus raising the question of why a different driver weren't used.

We have to understand that Dynaco was not a driver manufacturer. In fact, from Hafler's words, it seemed as if his decision to sell loudspeakers was primarily a push to sell a total consumer package at a high profit margin. Design parameters? I doubt that Dave had much interest in doing that math, but was happy to have it 'worked out' for him. In any case he states that the port stuffing sounded OK, so they went with it. From memory the Dynaco seemed to me to be a middle point between the muffled AR acoustic suspension sound and the more forward JBL port sound. Plus, the speaker was easy enough to drive with Dyna amplifiers. The Advent sound was less AR, but more AR than Dyna. I think Advents probably had better dealer incentives than AR, which management left dealers cold, or that's the scuttlebutt. Advents also got pretty good press in Harry Pearson's mag, so that helped.

How did it go down? Dave likely asked the B&O people about loudspeakers, and was introduced to the SEAS folks. He drove over and auditioned some already made prototypes, and chose the one that fit in best with his existing product line. By the early '70s my impression is that Dave was really out of the 'design' end of it, but concentrating on marketing (and thinking of selling the company). By 1970 Hafler had hired Erno Borberly and Jim Bongiorno who were responsible for engineering some of the solid sate amps and tuners. Dave wasn't primarily involved in that anymore.

Like many (if not most) loudspeaker outfits of the day, Dyna bought off the shelf components, shipped them across the Atlantic, then completed the process by stuffing components into a box they either constructed, or had constructed for them. So the choice of drivers was also dependent upon non-audio factors such as initial cost of acquisition, how many could be produced in a given time to meet expected demand, ease of manufacture, expected dealer margins, etc. Hafler states that the SEAS supply chain was stretched due to Dyna's large quantity orders.

My guess (and it is only a guess) is that SEAS was able to promise enough of that particular ready made item, and since it was 'good enough' in the context of a price point, that's what they went with. It would have surprised me if Dyna ever did any in-depth and in-house loudspeaker R&D.

 

[Keith Conroy]

It is good to point out that these speakers were all designed 50+ years ago. For those of us who were around back then, looking at these speakers today is analogous to what it would have been like in 1970 to comment on speakers that were designed back around 1920.

That said, when Dennis used the descriptive phrase "nothing burger" to characterize the aperiodic thing, this was on the mark. When Aperiodic took umbrage at the characterization, I was motivated to second what Dennis said and explain the reasons. The aperiodic thing has bugged me since the first review of the A-25 I read in Stereophile so many years ago. It was apparent to me even then that it was hokey. Even then, I immediately concluded that all this could actually accomplish is to allow the enclosure to be smaller than a tightly sealed enclosure would need to be with the given driver, thus raising the question of why a different driver weren't used. When there is a question this obvious and it isn't ever answered or even mentioned, something smells fishy.

Something that has long been common with entrepreneurs in the audio field (and similarly in other areas of applied technology), is the practice of exaggerating the significance and uniqueness of any attribute that will potentially differentiate the product that someone wants to promote, from the competing products. This practice is pervasive, and we take it for granted. But I've never discerned a reason why other people should be expected to play dumb and refrain from pointing out when a claim that someone has made doesn't hold water. Are we supposed to continue playing dumb fifty years later? Should we continue indefinitely to bite the lip, or does a time eventually come when it is appropriate to say plainly what the thing truly is?

Other than the convenience of the small size of the enclosure, what advantage does the aperiodic approach have over a larger speaker using the same driver and with the same Qtc? There is no advantage other than the convenience of small size, while there is the significant disadvantage of destructive interference between the wavefront directly from the driver and the wavefront exiting the big opening.

Wow............I was just trying to point out that none of us were there at Dynaco during the design process.? So again, was trying to point out there might be more to the story internally. I can say 1st hand engineering is trade offs. There are sometimes where sales wins over engineering. This does not mean the company is not engineering driven! I have a degree in electronics and a physic's background. I have spent over 25 years working for many different Audio Companies. I have worked as a Acoustic Design Engineer, for Oaktron, MTX and Gefco. I have worked as a Mfg. Engineer and a Test and Measurement Engineer for Electro-Voice. I also owned a small OEM speaker mfg. company. This when speakers were still made in the USA. I have consulted for a dozen more companies. I have designed over 25 different raw drivers in my career. I have looked at and measured many more. I have also designed dozens of systems. Several of these over the years were Aperiodic loaded. They worked based on the driver I was using at the time. It was not meant to be magic, just a means to an end! I bring up my background only to say I sat in many design meetings over the years. Sometimes sales or a manager wins out. That does not mean the whole company is crap.

Again this was a time in history when raw drivers were measured differently. TS data was very new. Companies were working with the equipment and knowledge they had at the time. I'm just amazed how brutal the attacks has become on Dynaco the company and the A-25. Was it just snake oil produced to make money. I have no way of knowing. Nor do any of the other posters I have read to date? Dynaco the company had a very solid reputation in the industry during this time!

Many of the statements not just yours could use a lot of supporting data behind them. There were compromises made on many of the raw drivers of the time to fit a true air suspension profile. There have been some recent engineering papers written that claim the air forces in a box are not truly linear? I would not want to label this as true without reading a lot more about the subject. Just like I try to at least stay open on Aperiodic loading. Not so much the concept, but why Dynaco chose to use it in the A-25 system????

I'm just not sure what point your trying to make in several of your posts? Aperiotic venting is just snake oil? Dynaco is a terrible company? To me, Aperiodic loading is just one of many means to an end for a final design target. If I chose to really publish something at an engineering level I would want to do a lot more research. To say its a "Nothing Burger" would not work in an engineering paper, without detailed supporting data. I have no way of fully knowing more about the A-25's complete design choices without being in the design group during that time.

This will be my last post on this subject. We are getting way to far off fact based criteria & science for my liking........!! I'll try to embrace the positive fact that we all love audio here and the USA is still a free country. So everyone can post what they want!

 

[Robin L]

As I recall, the Dynaco A-25 was a comparatively small speaker, more AR 4 than AR 3, and priced accordingly. So it doesn't have as much bass as a Large Advent. This should come as no surprise. Comparing the small Dynaco to the Large Advent is comparing oranges to pomelos, sharing a few traits but still radically different. Maybe Dynaco could have made a sealed speaker with a smaller driver, but they didn't.

 

[mhardy6647]

As I recall, the Dynaco A-25 was a comparatively small speaker, more AR 4 than AR 3, and priced accordingly.

Didn't we do this already in this thread?

source: https://worldradiohistory.com/Lafayette_Catalogs.htm

 

[Robin L]

AR-4, 18" v 9" x 9", Dynaco A-25 20" x 11" 1/2 x 10", Large Advent, 14" x 11 1/2" x 26"

 

[bethslave]

Thank you Amir for this review. I do think reviews of vintage equipment are valuable when the equipment is performing close to the original specifications [as I believe this Advent likely is]. It is so hard these days to listen to speakers/headphones/earbuds before buying them that ideally these reviews are a great guide in replacing older equipment. In other words, if you like the sound of the New Large Advent you'll probably like newer speakers designed and manufactured by [insert relevant manufacturer here].

I thought my Advent Legacy III's had more in common with the NLA than they actually seem to. After reading this review and the comments it seems like the Legacy III perhaps corrected many of the quirks associated with the pre-Jensen Advent line. I was always a huge fan of Julian Hirsch's reviews and purchased my Legacy III's based on his tests and write-up for Stereo Review:

https://worldradiohistory.com/hd2/I...X/90s/Stereo-Review-1993-10-OCR-Page-0046.pdf

https://worldradiohistory.com/hd2/I...X/90s/Stereo-Review-1993-10-OCR-Page-0055.pdf

I lived in a large city back in those days and did get to audition quite a few speakers before making my purchase. One very kind dealer spent a lot of time with me demonstrating a rather expensive showroom system he had set up. It's been too long to remember a lot of the details but it involved Polk tower speakers and a Sunfire power amp. The Polks sounded better than the Advents to me, but not thousands of dollars better.

I still enjoy my Legacy III's very much but I do sometimes wonder what the next step up would be. I previously used a graphic equalizer and the typical 'rock and roll smile' tweaks. Likely for that reason the slight dip measured in the midrange between the woofer and tweeter doesn't bother me as it's approximately how I was adjusting other speakers to be anyway. After getting the Legacy III's I stopped using an equalizer and with my current amp just slightly boost the higher end with the treble control at approximately the 1:00 position.

Anyway...a fascinating review and comments.

 

[6sigma]

Solid review, Amir! Still have the original shipping cartons, doc & NLA (Walnut) from 1976. New surrounds & connected to the Advent 300 receiver. Under-powered, but haven't yet found an amp to use the receiver as a preamp.

For those who were Advent fans back in the day, what speaker is your go-to today?

 

[rdenney]

Solid review, Amir! Still have the original shipping cartons, doc & NLA (Walnut) from 1976. New surrounds & connected to the Advent 300 receiver. Under-powered, but haven't yet found an amp to use the receiver as a preamp.

For those who were Advent fans back in the day, what speaker is your go-to today?

For me, "back in the day" was a few months ago, when I replaced my stacked Advents, the first pair of which I bought in 1977, with Revel Concerta F12's. Better in most ways, but I need to work on the bass, which booms a bit.

Rick "never owned an amp that was too big for Advents" Denney

 

[6sigma]

For me, "back in the day" was a few months ago, when I replaced my stacked Advents, the first pair of which I bought in 1977, with Revel Concerta F12's. Better in most ways, but I need to work on the bass, which booms a bit.

Rick "never owned an amp that was too big for Advents" Denney

Totally agree. With four of them I was using 250W per channel. After way too much component/speaker swapping the last 18 months, I'm ready for things I can live with for the next 10 years.

 

[Robin L]

For those who were Advent fans back in the day, what speaker is your go-to today?

The a/d/s L400e came out in 1990, I had Large Advents back then, pretty sure they were the original model, but there's no way to be sure. They wouldn't work in my current space, there's not enough room.

But I do have a/d/s L400e speakers now [12" x 9" x 9"], and a powered sub. The a/d/s speakers require a sub, cut off very neatly below 100hz. Dialing in my Sonance "Son of Sub", I can get deep bass with no boom. The speakers have more clarity and focus than the Advents, produce a hard center mono image when streaming old movies. Not the ultimate in "focus", but generally smooth and easy to listen to.

ADS L400 Speaker Review (kenrockwell.com)

 

[mhardy6647]

The ads/Braun loudspeakers -- especially the earlier ones (IMO) are mighty fine indeed.

As a not entirely off-topic aside, I am workin' on a surplus pair of Dynaco A25s here (albeit slowly). I am semi-seriously thinkin' about boxin' one up and sending it Westward for a ride on the Wall of Death Spin-o-Rama.

 

[Dennis Murphy]

I've wrapped up my work with the A25, including a revised crossover that I think is a significant improvement. I don't think we're going to reach a consensus on the aperiodic loading issue. My read is that it was a stop gap measure that allowed Dynaco to use a readily available and affordable 10" Seas woofer that otherwise would have required a larger cabinet. I've compared the A25 with virtually every speaker I could lay my hands on, and I can't hear any advantage to the quality of the bass. If anything, it's more "one note" that any of the modern ported designs I listened to. But this is hardly a an urgent issue. Overall, the A25 holds up quite well and I prefer it from a tonal standpoint to most of its contemporaries.

The biggest problem with the sound is a hollow character to the lower treble that's due to an on-axis diffraction dip in at the low end of the tweeter's operating range. Most tweeters show this same dip, but it's exacerbated on the A25 by the sharp raised edges on the cabinet. I could flatten everything out on axis, including the woofer peak, with elaborate trap circuits, but the response got pretty wild and wacky off axis. You just can't make "modern" steep slope crossovers work with these vintage designs. The large woofers have to overlap widely with the tweeter in order to avoid severe directivity issues. It worked with the acoustic suspension woofers of the era because they had surprisingly even and wide response profiles. Although there was nothing I could do to avoid the tweeter dip on axis, I was able to smooth things out a little off axis, and that pretty much filled in the sound. See below for before and after plots at 15 degrees off axis. At angles wider than 30 degrees or so the stock and modded versions are a toss up.

 

[Jim Matthews]

The biggest problem with the sound is a hollow character to the lower treble that's due to an on-axis diffraction dip in at the low end of the tweeter's operating range. Most tweeters show this same dip, but it's exacerbated on the A25 by the sharp raised edges on the cabinet.

Is the tweeter parked dead center in the baffle, or offset?

My A26 variant was specific about tweeter placement.

 

[Dennis Murphy]

Is the tweeter parked dead center in the baffle, or offset?

My A26 variant was specific about tweeter placement.

It's offset to the left, which means the off-axis response will depend on the direction you move the mic. But the dip is there with the mic either placed directly on the tweeter axis or above the woofer center.

 

[eddantes]

Thanks @Dennis Murphy . I, for one, found this exploration of the old classics fascinating. And, I might say, eye opening, about just how good some of this old gear is! Advents and the A25s are probably two of the best selling speakers of all time - and both seem to have qualities that are worthy of those records. I'd been disapointed to find out that vintage speaker lore was built on junk.

 

[MrPeabody]

Wow............I was just trying to point out that none of us were there at Dynaco during the design process.? So again, was trying to point out there might be more to the story internally. I can say 1st hand engineering is trade offs. There are sometimes where sales wins over engineering. This does not mean the company is not engineering driven! I have a degree in electronics and a physic's background. I have spent over 25 years working for many different Audio Companies. I have worked as a Acoustic Design Engineer, for Oaktron, MTX and Gefco. I have worked as a Mfg. Engineer and a Test and Measurement Engineer for Electro-Voice. I also owned a small OEM speaker mfg. company. This when speakers were still made in the USA. I have consulted for a dozen more companies. I have designed over 25 different raw drivers in my career. I have looked at and measured many more. I have also designed dozens of systems. Several of these over the years were Aperiodic loaded. They worked based on the driver I was using at the time. It was not meant to be magic, just a means to an end! I bring up my background only to say I sat in many design meetings over the years. Sometimes sales or a manager wins out. That does not mean the whole company is crap.

Again this was a time in history when raw drivers were measured differently. TS data was very new. Companies were working with the equipment and knowledge they had at the time. I'm just amazed how brutal the attacks has become on Dynaco the company and the A-25. Was it just snake oil produced to make money. I have no way of knowing. Nor do any of the other posters I have read to date? Dynaco the company had a very solid reputation in the industry during this time!

Many of the statements not just yours could use a lot of supporting data behind them. There were compromises made on many of the raw drivers of the time to fit a true air suspension profile. There have been some recent engineering papers written that claim the air forces in a box are not truly linear? I would not want to label this as true without reading a lot more about the subject. Just like I try to at least stay open on Aperiodic loading. Not so much the concept, but why Dynaco chose to use it in the A-25 system????

I'm just not sure what point your trying to make in several of your posts? Aperiotic venting is just snake oil? Dynaco is a terrible company? To me, Aperiodic loading is just one of many means to an end for a final design target. If I chose to really publish something at an engineering level I would want to do a lot more research. To say its a "Nothing Burger" would not work in an engineering paper, without detailed supporting data. I have no way of fully knowing more about the A-25's complete design choices without being in the design group during that time.

This will be my last post on this subject. We are getting way to far off fact based criteria & science for my liking........!! I'll try to embrace the positive fact that we all love audio here and the USA is still a free country. So everyone can post what they want!

I have not made any "brutal" attacks on Dynaco the company or the A-25. I am perplexed that this is what you think, and I am perplexed by why you would have thought it appropriate to say such a thing. I am also perplexed by your apparently having difficulty understanding what I have tried to explain about the so-called "aperiodic" approach to speaker design. To be frank, anyone who has a rudimentary understanding of the interaction between the driver and the enclosure should have come to the early realization that the "aperiodic" approach isn't anything more than a sort of kludge that permits using a driver that inherently needs an enclosure much bigger than the enclosure that is used. I have no qualms about stating obvious truths, and this particular truth is about as obvious as they come. Personally I would not characterize it as a "means to an end", because this characterization only serves to obfuscate the truth about this design. It is far more truthful to simply call it a kludge, because this is exactly what it is.

As you may know, Seas presently offers a kit that is based on the original A-25 design. Seas calls this kit the A26. The frequency response plot Seas provides indicates an F3 point of about 55 Hz. The theoretical F3 point for the driver, if mounted in a sealed enclosure twice as large as the enclosure included in the kit, is around 45 Hz. The bass rolloff rate of the A26 is about 18 dB per octave, which is steeper than the theoretical rolloff for a speaker using a sealed enclosure. The cabinet included with the kit is a very lovely cherry veneer. Well, it would be lovely except for that big rectangular hole below the woofer. The driver is the Prestige A26RE4. The proper enclosure volume for the driver is right around two cubic feet. The volume of the enclosure supplied in the kit is about one cubic foot, about half as large as what the driver requires. Sticking with the same enclosure but without the big opening and with a different driver that calls for a 1 cubic foot enclosure, the theoretical F3 point can be lower. This depends on the driver's characteristics, but likely would be lower since the destructive interference would be avoided. The driver would be less efficient than the A26RE4, which means that the speaker would not be as sensitive, however in spite of the lower efficiency, bass response would be stronger owing to the avoidance of the destructive interference.

The A26RE4 has one feature that I especially like: the near-absence of sharp peaks and dips in its response at upper frequency where it begins to roll off and needs to perform well in order to reach high enough in frequency for the tweeter to take over. Because of this property, which I deem very desirable, I would be inclined to consider using this driver as a replacement driver for the woofer in the Large Advent speaker (the enclosure is roughly two cubic feet). There is however one aspect of the A26RE4 that makes me hesitant to suggest it as a replacement for the Large Advent woofer: the Xmax, or linear excursion of the cone, is only 8 mm, peak-to-peak. The reason the linear excursion is this small is that the voice coil is only 14 mm in "height" (length) while the gap height is 8 mm. The voice coil is barely 1/2" long. I don't know how this compares to the voice coil in the woofer in the Large Advent. The mechanical limit of excursion (which is determined by the suspension and by the distance from the back of the coil former to the back plate) is 35 mm peak-to-peak. This is quite good. But because the linear excursion is so short, distortion in bass will be comparatively high even when playing at moderate volume. Athough, distortion might not be any worse than what it is in the Large Advent and other speakers of that era, as evidenced by Amir's distortion measurements of the Large Advent. When I poonder this, I am inclined to suggest this driver as a replacement for the woofer in the Large Advent.

But would I build the kit? No. I would not use this woofer (or any woofer) in any enclosure that is only half as large as what the driver requires. Performance will be compromised if I do that, whether I do or do not cut a big hole in the front of the enclosure. If I don't cut a big hole in it, the resulting system Q will be excessively high, with a pronounced resonance and response peak in the mid-bass. I can keep this from happening by putting a big hole in the enclosure, but then the bass will roll off early and more steeply, owing to the destructive interference between the sound wave coming directly off the front of the cone and the sound wave exiting the enclosure through the big hole. I can choose which drawback I find more tenable, but the only way to avoid both drawbacks is to use an enclosure as big as what the driver inherently requires, or to use a driver that is suitable for use in an enclosure the size that I want to use.

https://www.madisoundspeakerstore.c...6-10-2-way-kit-pair-based-on-the-classic-a25/

 

[MrPeabody]

We have to understand that Dynaco was not a driver manufacturer. In fact, from Hafler's words, it seemed as if his decision to sell loudspeakers was primarily a push to sell a total consumer package at a high profit margin. Design parameters? I doubt that Dave had much interest in doing that math, but was happy to have it 'worked out' for him. In any case he states that the port stuffing sounded OK, so they went with it. From memory the Dynaco seemed to me to be a middle point between the muffled AR acoustic suspension sound and the more forward JBL port sound. Plus, the speaker was easy enough to drive with Dyna amplifiers. The Advent sound was less AR, but more AR than Dyna. I think Advents probably had better dealer incentives than AR, which management left dealers cold, or that's the scuttlebutt. Advents also got pretty good press in Harry Pearson's mag, so that helped.

How did it go down? Dave likely asked the B&O people about loudspeakers, and was introduced to the SEAS folks. He drove over and auditioned some already made prototypes, and chose the one that fit in best with his existing product line. By the early '70s my impression is that Dave was really out of the 'design' end of it, but concentrating on marketing (and thinking of selling the company). By 1970 Hafler had hired Erno Borberly and Jim Bongiorno who were responsible for engineering some of the solid sate amps and tuners. Dave wasn't primarily involved in that anymore.

Like many (if not most) loudspeaker outfits of the day, Dyna bought off the shelf components, shipped them across the Atlantic, then completed the process by stuffing components into a box they either constructed, or had constructed for them. So the choice of drivers was also dependent upon non-audio factors such as initial cost of acquisition, how many could be produced in a given time to meet expected demand, ease of manufacture, expected dealer margins, etc. Hafler states that the SEAS supply chain was stretched due to Dyna's large quantity orders.

My guess (and it is only a guess) is that SEAS was able to promise enough of that particular ready made item, and since it was 'good enough' in the context of a price point, that's what they went with. It would have surprised me if Dyna ever did any in-depth and in-house loudspeaker R&D.

I suspect that this pretty much hits the nail on the head. The actual engineering, beyond trial and error with the crossover, likely consisted of figuring out how to make it sound good using the small enclosure they wanted to use and using the driver that Seas made available to them. They may have first tried stuffing the enclosure with fiberglass, but they would have quickly come to the realization that the only way to avoid a sharp response peak at the system resonance point would be with using a large opening in the enclosure.

 

[dasdoing]

back in the days noone toed speakers in. could it be that designs were itentionally compensated for that?

 

[rdenney]

back in the days noone toed speakers in. could it be that designs were itentionally compensated for that?

Doubtful. That was the era when on-axis performance was the main target and directivity was not as well understood.

Rick “who never felt the need to toe in Advents” Denney

 

[Dennis Murphy]

back in the days noone toed speakers in. could it be that designs were itentionally compensated for that?

The response of the stock A25 doesn't start to smooth out until angles greater than you would encounter at a normal listening position with the speakers aimed straight ahead. What's interesting is that the rear tweeter control panel is positioned for a horizontal mounting--literally a bookshelf orientation. I haven't measure them that way--I'll have to check it out.