Pioneer PAX-25B Coaxial drivers

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Hi,

Does anyone out there have any experience with the Pioneer PAX-25B vintage drivers, or others from the Pioneer PAX range. I have just come across a discarded pair with cabinets that look like they were produced yesterday, not nearly 40 years ago, and wondered if anyone has done anything 'interesting' with them? Not including putting them in the rubbish bin of course!

Can't find a heap about them on the net, but it seems they were for the DIY market, and designed to be used in various sized infinite and bass reflex enclosures designed by Pioneer. The 102dB efficiency and Alnico magnets make them an interesting find.

Hooked up the rather large bass reflex boxes and was greeted with a nice forward midrange and sweet top-end, a bit muddy in the bass (but I think some changing over from the fibreglass bats for some acoustic foam and a bit of cabinet bracing will help that). I'll also change over the 'bell' wire used to connect the drivers and look at replacing the crossover electrolytic (?) capacitor mounted under the cone (?) tweeter for something else.

Simon
 
Some images of the Pioneer PAX-25B's.
 

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Unfortunately, no.

Pioneer Australia responded to an enquiry, but said Pioneer Japan no longer had any documentation about the drivers on file.

From looking around the internet it appears that the cabinets I found them in were the DIY bass reflex design put forward for the drivers by Pioneer. I've assumed this from finding very similar designs from Pioneer for other PAX drivers. see attached plans for the PAX-A20. I believe the PAX speakers were designed mainly for the DIY market.

I don't know the exact dimensions of the cabinets I found the drivers in as they are not in my possession at this moment, but I know they are slightly larger than the attached bass reflex plan here. I can measure them if you'd like.

I have replaced the electrolytic caps (3uf) with some polypropylene M-caps and have coated the rather soft paper cones with Visaton LTS 50. Sorry, I can't really tell you how (un)successful this has been as I haven't had much of a chance to listen to the speakers since I found them due to their largish size being less than ideal for my 'allowed' listening room. Still to 'play' with the cabinets.

regards,
Simon
 

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Hi Simon,

Thanks a bunch for the info, if you do ever get a chance to measure your cabinets I'd be interested, but no hurry, I suspect these things will be floating around in the workshop for some time.

I'm not sure how changing dimensions but keeping the same volume affects them but a taller/ skinnier cabinet would be better suited to my use and have a better WAF 🙂
 
I have found the PAX line to be very good. I also found that the caps that Pioneer used have for the tweeters have been universally good and changing them out for Russian PIO caps made no improvement.

My recommendation: Try them in a JELabs open baffle.

Erik
 
Hi Simon,

yes, it has been a while. And yes, I'm hooked on OB. The only reason I would ever use a box speaker now would be because of the inquisitive and questing fingers of my 2yearold. No going back.

I think that the JELabs is a good place to start. The way that you mount the driver makes a huge difference in my opinion.

Check these out. They are rare. I have a pair of them as well as a pair of PAX30G's and a pair of PAX30F's on their way from Canada. The PAX25 seems to be a bit of a rare bird, although you wouldn't know that looking at eBay the last couple of weeks. I've watched for years and haven't seen them turn up. A very good compromise between good bass response of the 12" and the speed of an 8" driver. Oh, and I have quite a few other Pioneer drivers. My wife thinks I'm ill.

The bottom line: Pioneer drivers like what you have are amazing machines. Highly underrated. The Pioneer PAX30F Coaxials with horn tweeter are at least as good as Altec 604's. Strong statement, I know. You just can't believe how these drivers load a room in OB. The room really does become the box.

I've listened to a lot of drivers now in OB and there is something special about what the Japanese were doing during this period.

I'm wandering, but don't believe everything that is claimed about OB. Some go on and on about how the driver Qts needs to be higher to gain enough Bass. Rubbish. My 30G's have very low Qts and little travel(paper surrounds) and in a small OB they generate amazing bass. The best quality I have ever heard. High Qts in OB gets bass, yes, but not the best. I like very tight and well defined bass. Texture.

Another thing. I've tried digital amps. Pro amps. SET amps. PP tube amps. Guess which amp has the best cone control and bass quantity and quality? An old Fisher X101 gives me loads of bass with almost no EQ in OB with less cone movement than anything else I've used. I was absolutely incredulous but had to believe my eyes and ears. Not only that, that stinkin' ugly amp sounded better than anything I've ever heard playing through those PAX(excepting the Maggie SEP amp, but that's a different animal). A real synergy. I would compare them to Altec A7's a friend of mine has. But, um, better. The bass is better.

Experimenting with baffle shape and size is worth the effort. These old drivers sound so good I just can't stop listening. Liquid gold. Candy for the aural senses. You just can't believe how sweet the treble is from these Fukuin tweeters. Your paper cone tweeters should still sound great.

Whatever, I've just come off of a huge amount of overtime at work. Storm damage. Sorry, I'm rummy, but wanted to reply.

People will read my claims and say I don't know what I'm talking about. Who cares.

I'll write more when I'm more coherent. That is, if anyone cares. Sure I'm biased. But I've also heard some hi-end audio that made me want to run screaming from the room. I don't listen to any claims any more. I just buy it and try it. If it sounds like crap it gets sold. I'm sure that a driver shows you its real worth by hooking it up and letting it play naked just holding it in your hand. MOST drivers sound like crap that way. Thin sound, awful. A few sound good and then you just coax the best out of it with a properly sized and shaped baffle.

I bought a pair of pipes that the guy said sounded amazing. Single driver, you know. They are crap. gathering dust in my shop. Once you really hear OB it ruins you for everything else.

I think the JELabs baffle is just way too big. It'll get great bass, even on a low Qts driver like the PAX, but the imaging suffers.

I just really like to listen to beautifully reproduced music. 60's Pioneers sing.

Erik
 
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Hi Erik,

Thanks so much for your inspiring reply. I can't wait to play with the PAX's further. I found them sitting on a local neighbourhood street ready for the rubbish collection a year ago.

I listened to them briefly in the cabinets I found them in. The cabinets look to be the larger bass reflex DIY cabinets Pioneer recommended for the drivers, from plans I've seen on the net.

I liked the sound of the drivers from what I heard, but thought the bass was a bit flabby. On further inspection I put some of that down to possibly the boxes and their construction/stuffing. Also, the drivers were hooked up with some old, very thin bell wire that may not have helped their cause.

I have since taken the drivers out of these boxes in expectation of doing something with them. Unfortunately, my wife also thinks I'm a combination of ill and stupid when it comes to my audio fetish. For this reason I had to get the rather large boxes out of our not so large livingroom before she returned home that fateful day.

I have noticed that the paper cones on these drivers are rather 'soft' with a very 'rough' undulating back-side to them. Is this similar to the other PAX models you have? Especially, the 'rough' back to the cones. I don't have much experience with older drivers of similar construction so maybe this is not a unique quality to the PAX (25B) drivers. Made me think though about what Planet10 are trying to achieve with their EnABL cone treatment process. Did Pioneer make the back of the cones rough to break up cone resonances naturally, similar to what Planet10 are trying to achieve with the artificial 'texturing' of the cone front? Hey, what would I know.

I have to agree with you re OB. I haven't really made a serious attempt at an OB speaker yet, but all my quick and simple efforts with OB's have left me fairly convinced that it is the way to go one-day soon. I have only really ever put smaller fullrange drivers onto simple baffles, except for one attempt at a very cheap copy of the "Bastanis Atlas" just for fun. One common thing though that I've always found is that the resulting sound gets the foot tapping and that the music is eerily realistic with the ability to clearly hear into the recording environment. It's almost like putting a room inside your listening room. And, although my attempts at OB have never really worried too much about the lower bass region, I have never failed to be flawed with the reproduction of strings, female voices and music that doesn't require those missing lower registers.

I'm interested to read your comments re the "Maggie SEP amp" as I have just finished winding my first output transformer 😱 which is intended to be part of a Parallel SET EL84/6P15 amp I'm yet to build. But that's another story...

One thing before I go though, could I ask what size baffle you would suggest I start playing with for the 25B's? I assume it would be in the style of the JELabs?

Thanks again for your inspiring reply, and anything further you may feel like adding to this conversation.

regards,
Simon
 
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Hello again Simon,

Well, I'm finally almost through my insane week of overtime. I'll be so glad to get caught up on sleep.

I only have time to respond to your question about baffle size. The links below are good info, but keep in mind that they are only one source.

Hawthorne Audio • View topic - Introduction to the Art and Science of OB speaker building

My First Baffle - 10 Pre-Fab Baffle Kit (each) [HA-MFB-10] - $42.50 : Zen Cart!, The Art of E-commerce

I have built the small baffle shown and it does sound very good. I have a suggestion or two for augmenting the design, but it is so very simple. I can tell you how to assemble the separate pieces as it is not obvious from the item pic. Dimensions are given. The only downside is that the sound source is pretty low on the floor. But then you also get good boundary gain from the floor for bass. There is quite a bit of action on that forum for OB experimentation. And a fellow in your nape of the neck, MrContent, has been active on there and he is a master of pragmatic OB theory.

BTW, your drivers are jewels. Compare the woofer to a PE16 or PE20 and you will see what I mean. The pedigree is first-rate. I'll bet the build quality of those things is extraordinary.

Offline I would really like to hear about your pset amp. I think you can pm or email me.

Cheers,
Erik
 
I have been a longtime lurker, but now I feel compelled to contribute.
Firstly I am a bit of a compulsive collecter of drivers, I'm sure my partner thinks I have an issue.
I have two pair of the PAX series drivers.
PAX-25B
PAX-A20
Both are fantastic to my ears, the treble is sweet, the mids are well integrated and the bass is solid enough for me.
I am using the PAX-A20 in large(ish) folded voights at the moment.
This is their construction thread
Can I Get Away With It? Rhino! - AudioEnz Forums
I have a pair of PAX-25B in the shed at the moment. Both pairs came in cabinets made by Jansen (a pro-audio outfit who made a brief foray into hifi). more detail here:
Pax-25b - AudioEnz Forums
The 25B sounded very nice in their cabinets, But I felt that they could be better yet, so I am very interested to read about Erik's open baffle, and may follow this avenue myself (I'm sure SWMBO will not be impressed, but I can blame Erik for that 🙂).
 
Papa Hemi,

Wow, that's some pretty cool stuff you have going on.

Just wanted to say that I will post a link to my picasa album where I have pics of a vintage Pioneer driver brochure. Pretty interesting stuff. I couldn't find much info online for PAX so I succumbed and spent $25 for the brochure from a guy in Turkey!

More soon.

Erik
 
Hello Erik and Papa Hemi,

Sounds like we all have wife/partner restrictions imposed upon us in our audio pursuits!

Erik, thanks for posting your Pioneer Brochure, that's the most I've read about the PAX range and the 25B itself in one place.

The Hawthorne Audio site has a lot of interesting information, thanks. I've read about the Hawthorne's, but for some reason had never gone to their site before. Remind me of the Bastanis, but without the subs.

The 'Spud' amp looks very interesting as well. As far as my PSET(P) amp, I haven't decided on exactly what output valve/tube to use yet (I have EL84's lying around so will probably start there) or which of the myriad of circuits I've collected to use/modify. I wonder if the circuit/link below is anything like the spud - this is one circuit I'm thinking of paralleling for its sheer simplicity.

Tube power amplifier

I also like the 'sound' of what I've read about the Decware SV83 amps and the variations/modifications others have come up with.

Unfortunately, things don't happen at a great pace around here, I'm just at the 'final' stages of putting together a pair of monoblocks based on the Williamson PP Triode Connected 807 circuit. This amp project was started 15years ago BM (Before Marriage) and has slowly come together over the years - note to self: I have got to focus more, so many things to play with, yet so little time to do it.

Papa Hemi, your project looks great and I bet sounds just as good. Is that a Triton Workbench shading itself in the back of photo there? I love mine, we've been together 20 years now, and she's coming to live with me if there's ever a break-up in the family! Did you ever try and smoke that mould on your 25B's surrounds, you might have been onto something - NZ's audio equivalent to the magic mushroom 😉 My 25B's were in emaculate condition when I found them, as are your A20's, so much so that I was a little disappointed when I opened up the mystery speaker box to find an unknown driver of obviously recent replacement - oh how wrong I was after a quick search on the net.

Thanks guys for keeping the thread active, I'm now off to read your links more thoroughly and learn lots more.

Simon
 
these are on trademe at the moment, they have been up a few times without a sale, some people just don't realise what classy wee units they are:

PIONEER PAX-A20 full range coaxial drivers for sale - TradeMe.co.nz - New Zealand

Simon - no I did not try to smoke the mould, I'd be reluctant to roll up that paper cone. They are quite strange, quite felt-like. I have removed as much as I could with a 50-50 IPA water mix, and have tated with the idea of doing the dammar varnish thing, but due to the strange nature of the cone material I am reluctant in case I alter the characteristics too much. They don't look that good but perform very well.
It is a Triton bench you see - a great tool - if only my woodworking skills could do it justice.
Thanks also to Erik for posting the brochure, I am having a jack at it now.

Keep on rockin
PH
 
Hey you guys,

I'm certainly enjoying this thread. I'm no expert for sure, so keep that in mind.

As far as the paper of the cones, when you start looking around at Japanese drivers of this period you will notice that all the better ones have paper that looks this way. The back is textured. Not sure if it contributes to the sound at all but i am sure that the process of making that paper is no accident. The proper ingredients for really good sound that I have found so far(much of it as a direct result of tutelage from DMason of the "gravity well of a darkstar" OB thread) are NOS DAC source, Alnico magnets, paper cones and tube amplification.

Simon, I would pause before adding anything to your cones. I can't believe you scored those from someones garbage. Seriously good story there. if I were you I would seal those cabinets and see what that does to the sound. Bass should be better I would think. I know more about OB than cabinets, but it seems worth trying.

I think that drivers prior to Pioneer's FB cones sound better. A paper or accordian surround seems better in OB than a cloth roll surround. I have not been able to make a cloth roll surround driver sound good in OB. That's just me.

So, the Hawthorne Audio minibaffles are a good place to start. But, I was thinking that with your drivers being 10" you might want to be reasonable in your expectations of bass. After all, there is no replacement for displacement. Anyhow, those are so easy I would try them first. The WAF should be pretty good for those. The biggest thing that I would advise there would be to add a 2" roundover to the 3 edges or just make the baffle 2" thick with rounded edges. That seemed to give real weight to voices using my drivers. Oh yeah, don't use MDF. Use real wood. I tried MDF the first time around and was so underwhelmed....dead sound.

My biggest beefs with the JELabs baffle are the size and the wings. There is just no way I can have something that big set up in my house. The other thing is that the wings, whatever people may say, made a sort of cavity resonance that I didn't like. So, what I did was to trim the baffle and then to add a quite big wing only on one side. I then biased the driver toward the short side to improve imaging. I doubt I would do that again. The big wing creates quite a bit of separation between front/rear wave and gives some good bass support. I call it an L baffle and it doesn't give any resonances that I can hear.

The other thing I haven't mentioned but that has at least as much effect is how you mount your driver. Why would you mount your driver from behind a 3/4" hole that pretty much makes a tunnel for the sound to pass trhough. My PAX only allow for rear mount so that makes it a bit tricky. What I did was to cut a 2" wide "bezel" 1/8" thick that I attached to the front of the baffle. Then the driver can mount from behind and end up pretty much flush mounted. My experience showed that this really improved the sound.

I've burned up quite a bit of plywood testing sizes and shapes for all kinds of drivers. My present baffles are just test mules but I haven't taken the time to make the final copy. I don't really care how they look so much as how they sound. YMMV.

The next thing I want to try is a dipole waveguide using a pair of full-range Pioneer PE-12's that I have laying around. They would end up being 15" square and 12" deep.

Erik
 
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Hi guys,

Erik, it's too late! I've already treated my cones with a thin layer of Visaton LTS 50 that I had in the house. Papa Hemi/Erik, I read somewhere, and it sounded authorative at the time, that stiff cones should/can be treated with Dammar, C37 type treatments and that soft cones should/can be treated with Latex type treatments. The reason I did it was I thought the cones, why after 40 years I don't know, might be susceptable to moisture. I can't say that it has helped or hurt the drivers as I was quite unfamiliar with them when I did it. Talking about treatments and stuff, if you're interested in such things have a look at the 'Mother-of-tone' website - can't vouch for it all, but it makes sense and interesting reading. Just a hint - Try following some of the links and names mentioned on the MOT site and you can really end up in the 'mystical corners of audiophile-dom'.

Inspired by 'our' thread I took the 25B's out for the afternoon yesterday. I simply placed them on our polished wooden floor using their baskets for support and upward angle, I then faced them in slightly and sat back for a listen. I put on Disk 1 of 'Jazz at the Pornshop' and have to say I was quite stunned. Obviously the Drums and bass were a little shy, but the Vibes, Sax, Clarinet, and Piano all sounded fabulous and natural. The dynamics were very impressive, and the audience chatter and their incidental noises were frighteningly real on occassions. My wife and 10year old daughter also commented favourably on the sound - a first for my wife when it comes to my OB experiments. 😀 I can't wait to get them into some real ply baffles. I think I will try something like the Hawthorne single or duets. There is a company in Australia, Etone, who sell some 10" and up bass drivers that might be suitable for a duet like setup. I like the Eminence drivers but with the weight the cost of shipping to OZ pretty much doubles the price of the drivers.

Erik, thanks for the tips on driver mounting. It seems some manufacturers prefer rear mounting (Bastanis - http://www.bastanis.com/pdf/Mandala_cutting_plan.pdf) and others flush mounting (Hawthorne). I think I will try the flush mount first, possibly trying to isolate the driver from the baffle using a rear mount on the driver as I've seen elsewhere (Linkwitz and others). Has anyone here tried this?

Erik, the dipole waveguide sounds interesting. Is this anything like bass units on the Linkwitz Orion (W frames?) or the Bastanis Bass Cabinet for 18" drivers? (see link above)

I hope to have more to add soon, and look forward to reading all of your further contributions to this thread.

Just a thought, what happens if you smoke hemp cones 😎

Simon
 
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Hi Guys,

Simon, hey, it looks like you've done quite a bit of reading there. I used to do that but the last couple of years I've pretty much stayed off of the fora. I only got back on this one because I guess I had ticked the box to notify me if anyone else replied.

I've never done any cone treatments so I'll defer to your experience. I'm just hesitant to screw with these drivers without a good reason. The doped paper surrounds, as long as they are still pliable should be fine. I've read that some peeps have found the paper surrounds to have hardened on their PIM20's. Mine are still fine. Another thing is that people assume that the caps in the crossovers are no good. I've replaced caps on Coral coaxials with good quality Russkie PIO caps and found no difference sonically. The Pioneer PAX horn tweeters I have sound so dang good I just don't see the point. Whatever Pioneer were doing, they were doing a good job of it. I don't know if it is possible for a cap to last 40 years and still work properly but mine seem to be doing fine. I read a lot about the eNable process but haven't had the guts or the time to try it out.

I haven't looked at the Mother of Tone site for quite some time. However, if I remember correctly, the Pioneer PAX have what the doctor ordered. Paper cones and formers, etc. That is the thing with these drivers, the tone. The only other drivers I have tried that had that kind of tone were some German 12" FR's that had a very soft, velvety almost felt cone. Those were special and I wish I hadn't sold them, although they were pretty power hungry and I like the sound of a very low powered amp. And then, I've got too many speakers anyhow.

So, you have now experienced OB. Good for you. You won't go back, you know. When your brain gets used to that sound every box speaker from then on will just be sound coming from a box. My friend, Dan Mason, is STILL listening to his speakers without a baffle of any kind. Just naked. He snagged a pair of Pioneer PE-16M's that are just unreal build quality and apparently killer sonically. He just props them up against a door or something available. He's helped to convince me that a lot of what is accepted as "conventional wisdom" can be challenged. Like isolating the driver from the baffle in order to eliminate any vibrations. I know that there are arguments against having any vibration transferring to the baffle and they make plenty of sense. However, actually using the baffle as a sort of soundboard needs to be tried before discounting it out of hand. I do think that a sort of magnet mount could be good for the driver, however.

I'll try to dig up a pic of the dipole waveguide so that you can see what I mean. It is not a W frame. I am two cuts and some glue and screws away from a pair of W frames using Pioneer 15" Alnico woofers that came out of CS-63dx's. The project has been taking a long time. There are two drivers per side. I think it will work well and relieve the PAX of their bass load. The plan is on the GR Research site, I think. I'll have to look. Anyhow, with the W-frame woofer setup I can mount just about any FR driver above it on a very small baffle(advantages!) and biamp and match levels via my Pro crossover. I'll try to put a pic of the 15" drivers here. Please let me know if it doesn't show up.
An externally hosted image should be here but it was not working when we last tested it.

The driver on the left is one of a pair of Coral triaxials that simply sucked. Ahem. Perhaps I should not say that before listing them on e*ay.
The W-Frame looks a little like this one by GR Research, just the angles are different:
v2nude.jpg

Well, that is about it for me today. I'll try to locate the pic of the dipole waveguide that JohninCR made and which I want to try. John isnt' very active any more as far as I know. He is a guy who had a very firm grasp of the theory and was crazy into trying new things. He was committed to OB but when he made his waveguides he stopped fiddling with speakers. He had found the sound he wanted. Power response was better, a lot of things were better. My only beef was with his choice of driver. Visaton B200's. But that is because I'm prejudiced. I think that anything but alnico sounds dead and wrong. I'm an audio bigot. BUT, the hemp cone does intrigue me. That is why I keep looking at these. The Alnico San Rafael's look really intriguing and cheap. By all accounts the hemp cones are just killer for tone. I may try them yet.

Oh, and thanks Simon for the Bastani's link. I'll look that over for any ideas to glean. But, like I've said, I mostly don't frequent any forums any more. The best things I found were just from my own experimentation. And some of those experiments sounded horrible, let me tell you. But over time I began to realize what sounded good to me and I developed a bit of a sense of what it might take to get there. I don't use any measuring equipment other than the ones attached to my head, which many would say is a real crapshoot. It's been fun. Even funner is having a friend over with $$$ in Audio and seeing the expression on his face when he hears my ugly and cheap system. My system sounds alive and his sounds dead, harsh, dead, lifeless, dead. Did I mention that it sounds dead? And that he spent lots of $$$ on it and countless hours setting it all up? I say fooey on all that. We got sold a bill of goods with all the solid state, hi-tech garbage. There probably haven't been too many advances in audio that matter since the 1950's.

Asta,
Erik
 
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