Pioneer PAX-25B Coaxial drivers - diyAudio
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Old 26th October 2009, 02:08 AM   #1
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Default Pioneer PAX-25B Coaxial drivers

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
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Old 26th October 2009, 03:36 AM   #2
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Some images of the Pioneer PAX-25B's.
Attached Images
File Type: jpg PAX_25B_A.jpg (90.1 KB, 890 views)
File Type: jpg PAX_25B_C.jpg (54.0 KB, 812 views)
File Type: jpg PAX_25B_D.jpg (50.6 KB, 794 views)
File Type: jpg PAX_25B_B.jpg (55.7 KB, 783 views)
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Old 12th April 2010, 09:15 AM   #3
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Greetings,

Did you get anywhere with these, I just picked up a NOS pair as well but cant find anything about them either.
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Old 12th April 2010, 10:59 AM   #4
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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
Attached Images
File Type: jpg pax-a20(2).JPG (17.4 KB, 707 views)
File Type: jpg pax-a20(3).JPG (17.0 KB, 141 views)
File Type: jpg pioneer1.JPG (26.2 KB, 144 views)
File Type: jpg pioneer3.JPG (23.2 KB, 177 views)
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Old 12th April 2010, 09:14 PM   #5
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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
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Old 13th April 2010, 03:18 AM   #6
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WAF - tell me about it!
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Old 18th April 2010, 02:29 AM   #7
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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
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Old 25th October 2010, 12:53 PM   #8
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Erik, Apologies for the late reply. JELabs sounds like a great idea. Have you done this yourself? If so, can I ask which PAX driver(s) have you tried OB?

Thanks,
Simon
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Old 26th October 2010, 04:56 AM   #9
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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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Last edited by Viridian; 26th October 2010 at 05:02 AM.
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Old 27th October 2010, 03:35 PM   #10
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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

Last edited by gapmedia; 27th October 2010 at 03:40 PM.
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