Altec Bolero 890c experiment incoming

Hey guys - it's been a minute since I posted. All I can tell you is newborn human children and highly involved audio projects tend not to mesh well. Especially when those children are ones that being to you.

Anyhow, with the dust starting to settle and something approaching regular sleep schedules on the horizon, I thought I'd document some essperimenting I have in mind for a pair of 890c Boleros I may or may not need to snuggle into the garage in a stroller in the dead of night.

The objective here is to get a compact shelf mount type enclosure for a 13x14 lounge. Assuming we're all on the same page regarding calling all systems other than our primary system a "second' systems, then that's what this is.

Said enclosure need to be efficient enough to run the low watt amp projects that seem to multiply all on their own, originating around my lab bench and spreading through the garage like something outta Creep Show.

Another objective is not to (for now, anyway) build any new enclosurs, because you can't make that kind of racket in the garage with a baby sleeping mere feet above you.

And finally, they need to sound kickass and not cost a fortune. So the above parameters left me casting about for a suitable platform, preferably of the Altec Alnico variety that my addiction cries out for.

Enter the Bolero with its 406-8Y 10" midrange driver, which uses the 414 motor assembly and a 3" voicecoil, being 1" and 1k shorter at crossover fq than its predecessors - the 406z/a, in the other Bolero.

So being short on 414s at the moment, and soon to be long a nice pair of Bolero 890c on a trade deal, I'm going to see what I can do with this driver and enclosure platform.

Having seen the original crossover components, they're an obvious place to start. But even more tempting to me is a setup along the lines of what @je2a3 and @Salectric have long advocated - letting the 406-8t run free and bringing in a more substantial FR arrangement on top.

Fortunately, the WE/Altec 32ish RCF h3709 horns I've got collecting dust in the garage are short enough to fit on top of horizontally placed Boleros.

Until I get a pair of the 808s or 802s that are "loaned" out back home, I'll try running the RCFs atop the Boleros, driven by the underappreciated (in my book) and cheap as dirt (in all our books) phenolic-diaphragmed RCF N480.

I've already got a pair of model 15 crossovers, which let the 12" mystery drivers (manufactured by RCA I think) in the M15s run full range.

I understand that, run full range, the 406 drops of around 3-4k. Wil be interesting to gather results of all this relative to the stock Bolero.

After that, the sky's the limit. I'll eventually get the Altec 8xxes up top. I could get rid of the inductor like I first tried on my 9844s, using only a cap on the compression driver, after reading a @Salectric post about it several years ago over on another forum.

Has anyone ever tried running the Bolero with dual 406s per side? Is such an arrangement even feasible in a sealed box? Am I trying to craftily introduce an optimized, shrunken form-factored 9844 into the domestic environment? Ok maybe I've thought about it....

Amps on hand for testing purposes include Allnic A1500 300b, a restored Scott 299b (but with bigger 222c/d power and OPTs), Golden Tube 300b monos, various test mule/console amps. I'm really liking this tiny Sylvania console amp that shipped as a 6V6 SEP (basically a Febder Champish circuit). I've converted it to triode and made some improvements. I'll eventually swap Sony TC-500a iron into it on a new chassis. Maybe something like the @je2a3 revised darling amp running 6v6.

Love to hear your thoughts on all this. I should have the Boleros in the house this weekend.

Pardon the typos - I'm on mobile and it's late.

More to come if you all are interested.
 

je2a3

Senior Member
755Ex2.jpg

414Ax2.jpg

Through the years, I've experimented with double LF drivers (755E x 2 and 414A x 2) in a mono set up. Each time I was disappointed. In spite of the gains in scale, low frequency extension, dynamics and higher SPLs, I couldn't live with the muddled midrange and lack of overall purity. But that's just a reflection of what I want out of my hifi set up and my preference to keep things simple.

If I were in your shoes, I'll bypass the Heppner horn, run the -8Y in wide range mode in the original box w/ passive radiator and mount the RCF horn combo on top using the M15 XO as a starting point. The RCF H3709 is a nice horn! If mounted free standing, it might (?) need a bit of damping since the metal used was relatively thin. Since it's a straight horn, make provisions for greater attenuation vs. the 90 degree bent Altec 32 horn.

My gut feel is the 406Z and 406-8Y will give more bass in a bigger box like the 614. Something I've been wanting to try.
 
Why stick with the Altec driver? (I know, blasphemy round these here parts) They seem to just drive cabinets large.
 
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Plus 1 on the congratulations. I can relate a lot, we’re basically in the same boat. I have two girls, a three year old and a five month old which takes priority over fun vintage audio experiments.
I’m currently sitting on parts to build something similar to the JElabs Altec 2way as well as two turntable projects, a Dynaco ST35 project, etc, etc.

Good luck on your experiments!
 

marantzfan

Administrator
Staff member
I’ve got a pair of 890B Boleros and they are fantastic. Classic Altec sound in a small package.

I attribute a lot of what I’m hearing to the 3000 series tweeter. Not sure how the Hepner horn stacks up to it.
 
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View attachment 37126

Through the years, I've experimented with double LF drivers (755E x 2 and 414A x 2) in a mono set up. Each time I was disappointed. In spite of the gains in scale, low frequency extension, dynamics and higher SPLs, I couldn't live with the muddled midrange and lack of overall purity. But that's just a reflection of what I want out of my hifi set up and my preference to keep things simple.

If I were in your shoes, I'll bypass the Heppner horn, run the -8Y in wide range mode in the original box w/ passive radiator and mount the RCF horn combo on top using the M15 XO as a starting point. The RCF H3709 is a nice horn! If mounted free standing, it might (?) need a bit of damping since the metal used was relatively thin. Since it's a straight horn, make provisions for greater attenuation vs. the 90 degree bent Altec 32 horn.

My gut feel is the 406Z and 406-8Y will give more bass in a bigger box like the 614. Something I've been wanting to try.
Great info here. The photos of your experiments are wild! There's no doubt the dual driver arrangement - at least in the vertical orientation I tried with modded 9844 has accuracy 'issues.' Somewhere I've got RTA grabs of running the 9844's dual 414s stock vs running only one vs running one as a 'helper' woofer as was alluded to below.

The results were not ambiguous. Lots of weird phasey things happening in the low mid band with dual drivers that were NOT happening with the other two approaches. Maybe I can find them. They're not pretty.

Despite all that, I found myself going back to dual use more often than not even I had the 9844s. I think primarily because: a) I had 4 of them, just...staring me in the face, b) it's what I used to in the room, and c) that scale and weight you referred to was... hard to let go of. Especially in an a/b type situation where you're dropping the weight out, which made the single driver sound light by comparison. And in fairness, at the time I didn't give my ears adequate time to adjust to the new scale of the single driver setup. Regardless, single driver 414 is on the project list. Love that driver!!

I'm looking forward you trying the RCFs with the Boleros. Any suggestions re: dampening? Those things ARE ringy and thin. I cringe at the nose they make at the slightest touch. They're like audio nerd cattle bells announcing to the house that yes, he's playing with speakers again. EDIT: Ibmn the past, I've used 3M Professional Grade Rubberized Undercoating spray. Seemed to work somewhat ok for the 811 ringing, but not the ringing that particular horn causes in my ears.

If don't get detoured with other projects, after the boleros get sorted I'm going to refinish my 614s and get some 414s into them. They're currently housing a pair of the little Corals, where they make surprisingly good bass tuned to somewhere between 70 and 80hz if I remember correctly.

Not sure what to do with the Corals - I was gonna put them in enclosures and give them to a musician friend with a reworked Maggie amp, but the more I play them the more I'm thinking i'll have to find a second pair for that project!
 
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First and foremost, congratulations on the new addition to your family!
i take it you mean the speakers. ;) What color balloons on the mailbox should I consider?

Kidding. Thank you!! She's healthy, better looking than me thank heavens and not usually averse to sleep, The baby hat trick!
 
Plus 1 on the congratulations. I can relate a lot, we’re basically in the same boat. I have two girls, a three year old and a five month old which takes priority over fun vintage audio experiments.
I’m currently sitting on parts to build something similar to the JElabs Altec 2way as well as two turntable projects, a Dynaco ST35 project, etc, etc.

Good luck on your experiments!
I totally feel your logjammed project pipeline issue. Yes. yes. the kids take priority.... but maybe there's a tiny sliver of prioroty left over, completely unused at the end of the day....Can't just let it go to waste can you?
 

je2a3

Senior Member
I'm looking forward you trying the RCFs with the Boleros. Any suggestions re: dampening? Those things ARE ringy and thin. I cringe at the nose they make at the slightest touch. They're like audio nerd cattle bells announcing to the house that yes, he's playing with speakers again. EDIT: Ibmn the past, I've used 3M Professional Grade Rubberized Undercoating spray. Seemed to work somewhat ok for the 811 ringing, but not the ringing that particular horn causes in my ears.

If don't get detoured with other projects, after the boleros get sorted I'm going to refinish my 614s and get some 414s into them. They're currently housing a pair of the little Corals, where they make surprisingly good bass tuned to somewhere between 70 and 80hz if I remember correctly.

Not sure what to do with the Corals - I was gonna put them in enclosures and give them to a musician friend with a reworked Maggie amp, but the more I play them the more I'm thinking i'll have to find a second pair for that project!
I'll start with baffle mounting the RCF3709. That's what I did when I played with it in the attic.

I have a pair of CalRad 12" wide range drivers that look like EV Wolverine clones that seem to have potential. They might be Coral OEMs.
 

je2a3

Senior Member
I’ve got a pair of 890B Boleros and they are fantastic. Classic Altec sound in a small package.

I attribute a lot of what I’m hearing to the 3000 series tweeter. Not sure how the Hepner horn stacks up to it.
AFAIK, the 890B uses the 406Z which uses a similar sized magnet but slightly smaller voice coil than the 406-8Y. To my ears the Z has better midrange snap at the expense of slightly less LF extension, vs. -8Y. I like the 406Z + 3000H combo very much!
 
What types of caps have you l liked in that position?
I’m using PIO motor run with film caps paralleled to adjust value/crossover. You can see a picture of the back of my speaker at the end of the 802/32/414 pinned thread. Not married to any flavor of caps, at this point, with all films the next step at a slightly different value (measured value). I work slow...listen to music more than I change things. I’m not sure of the crossover frequency...I’m using a online calculator with 8 ohm on high pass and 16 ohm on low pass, then adjust frequency until I match cap value.

My goal is simplified...nothing between wide-range 414z and the tube amp but wire. And no resonator box to tune therefore the open back. I’m bringing the 32c/807 in slowly to help the top end, but not to step on the 414z. I’m using the less sensitive Altec CDs thinking they would be a better match to the 414z without the need for a L-pad. On bottom, I’ve got the same goal, but haven’t done much critical experimenting. I’m using a 605B in a H-frame cabinet with only the woofer powered by some plate amps with crossover fq at 40hz. Really like the sound of bass guitar and drums with this setup. MiniDSP may be the best solution here, but then, I got to learn how to use it. I have a Nakamichi TA3A with Nelson Pass designed stasis amp I would like to use here.

je2a3 is the man for help. His blog got me started down this road.

I almost forgot, I bought 2 pairs of 414Z’s to do the dual 414 thing, but one pair arrived damaged. Your thread has me thinking I need to get the damaged one repaired and....a never ending road!! But it’s fun
 
I’m using PIO motor run with film caps paralleled to adjust value/crossover. You can see a picture of the back of my speaker at the end of the 802/32/414 pinned thread. Not married to any flavor of caps, at this point, with all films the next step at a slightly different value (measured value). I work slow...listen to music more than I change things. I’m not sure of the crossover frequency...I’m using a online calculator with 8 ohm on high pass and 16 ohm on low pass, then adjust frequency until I match cap value.

My goal is simplified...nothing between wide-range 414z and the tube amp but wire. And no resonator box to tune therefore the open back. I’m bringing the 32c/807 in slowly to help the top end, but not to step on the 414z. I’m using the less sensitive Altec CDs thinking they would be a better match to the 414z without the need for a L-pad. On bottom, I’ve got the same goal, but haven’t done much critical experimenting. I’m using a 605B in a H-frame cabinet with only the woofer powered by some plate amps with crossover fq at 40hz. Really like the sound of bass guitar and drums with this setup. MiniDSP may be the best solution here, but then, I got to learn how to use it. I have a Nakamichi TA3A with Nelson Pass designed stasis amp I would like to use here.

je2a3 is the man for help. His blog got me started down this road.

I almost forgot, I bought 2 pairs of 414Z’s to do the dual 414 thing, but one pair arrived damaged. Your thread has me thinking I need to get the damaged one repaired and....a never ending road!! But it’s fun
This sounds like a great approach. I use the same mix n match method - mainly using GE Dielektrol motor runs - for crossovers. I've been using the same 20 or so caps for years now and, leaving the wonderful sonics aside, I love the durability. Unbeatable for the money.
 
Quick update on the Boleros. Picked them up over the weekend - drivers and PR appear to be in great original condition.

Gave them a quick spin on the Allnic 300b and original crossovers. Wow. You guys weren't kidding about the psychedelic richness and tonal depth of the 406-8Y. They had that dull/tired cap sound for sure though.

So step one was to recap the original crossovers to get a feel for the stock sound.

I'm running low on crossover value caps, so I had to use the dregs of my GE 97F series motor run cap supply. That left me short a pair of 3 uf caps. Hmm....

I tore down an early 1950s organ that was destined for the junkyard a few weeks ago. I netted around 40 6SN7s of various manufacture, some boat anchor sized PTs, and lots of other stuff for the parts bins.

Among the parts were a good number of the Sangamo Type 30 paper/foil in molded plastic capacitors. There isn't a ton of info out there regarding these caps for hi-fi applications. They're sold occasionally as tone caps for guitars. I should restate - they're *for sale * occasionally. I've only been able to find one or two first person mentions of folks using these for guitar or hi-fi applications. The 1960s manufacture Type 33 seems to be better known, albeit of a similar construction. Yes, they're likely somewhat leaky, although nearly all I tested (not under voltage - just DMM) were within tolerance. Anyway, I was desperate to get the Boleros running and I had no intention of waiting a waiting a week for new caps to arrive.

So in the Sangamos went at the 3uf position, which is the capacitance portion of the upper MF (I think) attenuation filter on the horn.

Finally got the recapped Boleros back in the system this afternoon and I am loving these Altec-sized 'bookshelf' speakers. Utterly gorgeous depth and texture in the midband which, yes, sounds quite a bit like my dearly departed 414z.

From memory, the 414 are clearer - especially from ~400-1600hz - and more articulate for sure. But the 406-8Y + passive radiator in the sealed enclosure, with stock networks make fantastic low-mids, perhaps even a bit richer than my recollection of the 414z.

Hard to discern the impact of the 3 uf Sangamo Type 30 caps. With the recap, the HF section sounded fantastic. Not grab you by the collar as with the 80X compression drivers we're used to, but it definitely fits the fun sonic vibe of these speakers. And honestly, I was so enthralled with the midband, I wasn't overly concerned.

Really blown away by how much music these speakers make. Stock, they crush other similar sized speaker systems I've heard or owned (sorry Harbeth C7-es3) and really do live up to the praise owners have for them.

Can't wait to try some network variations. I tried the Model 15 networks for just a moment, but they need a recap also, so I didn't bother with further listening on the 15 networks.

So the recapped Model 15 network will be up next.

I've done a good bit of reading and have seen a few posts on the DIY forums that seem to indicate the T/S parameters of the 406-8Y suggest an enclosure of ~5.6 cu ft(!)

That's near to 612 territory. Has anyone ever considered going this big with the 406-8Y?

869F124E-7EA8-473A-87B8-28758516B883.jpeg
 
They fit well on top of the primary speakers. Did you mirror image the woofers?
Good question and no, I was so focused on not damaging the drivers I didn't think to mirror image them when I removed the stock crossovers...it's been driving me nuts for a few days now!
 
Quick update. I still haven't gotten around to recapping the Model 15 crossovers. However, after running these speakers on the stock recapped crossovers for a few days, I finally got around to running the 406s full range.

Tonallly, it seems the stock network was designed to get the max LF impact out of the 406s in the small Bolero box.

I have to say the stock network succeeds at this objective, as running the 406 wide open does result in a loss of some of that Bolero low-mid density.

But the tradeoff is that the 406 full range sounds phenomenal in the higher registers. You get another octave plus, and the 406 retains that rich texture and warm yet detailed delivery up to roll off.

Comparing the two side by side, the fully stock side sounded closed in, with a darker voicing than the full range side. The stock Bolero has a clear emphasis on the low mids, compared to the wide open 406, which was more 414-like: midrange forward, articulate, somehow both rich and open.

The two things that surprised me the most about running the 406 wide open were the increase in overall output/sensitivity of the 406, and how drastically different the driver's 'natural' voicing is from the sound imparted by the network.

It occurred to me that this is the first Altec system I've heard that was likely developed from start to finish as a consumer product. You can really hear how purposefully the network was designed to deliver a certain (very pleasing) sound. It's very to the Altec sound, and it walks all over other 'hi-fi' products i've hearts and owned, but it's slightly domesticated compared to the professional and professional-derived Altec systems I'm familiar with.

I really like the stock Bolero sound, and it seems clear the network was optimized for the Bolero enclosure. Getting the most out of the raw 406 would surely involve new enclosures.

I miss the low end authority the stock Boleros make, but the 406 sounds awfully good running wide open. For now, I left them that way. Need to do some more listening. Probably in different/smaller rooms too.
 
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