Looking for Audax HD20B25H mid/bass Driver

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Does usual googling... :eek:

Audax HD20B25H bass unit:

http://www.audax.com/archives/HD20B25H%20-%20Catalogue%201982.pdf

Lentek S4 looks like a very well constructed closed box 8" plus 1" bextrene speaker with (yippee!) a removable front baffle.

Crossover might be this sort of thing, albeit 4th order negative polarity tweeter:

384479d1385490889-heybrook-hb2-xo-kef_cadenza_crossover_schematic-jpg


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Tended to do a little presence dip between 1 and 2kHz with bextrene units.

The awkwardness might be that though the audax has the usual 186-189mm cutout, the front plate is a narrow 203mm. Most replacement drivers are 215-230mm outer diameter.

Candidates might be the closed box SEAS P21RE and the reflex Vifa P21W0 at 215mm outer diameter. Both still around at about £40-60 a pop. You might have to make a new baffle. Crossovers can be adjusted. In fact you could gut the whole thing and end up with a good modern speaker.
 
Steve for those of us half way around the world from Europe, the P21WO20 is now called the ScanSpeak Classic and it costs $98.60 not including tax and shipping.
Also, a possible crossover might resemble the one in the Tabor.


The Audax had the really good midrange like a low budget BC1.
The price of used Spendors over here is crazy.

I've never heard the Lentek S4 (almost 0 made it to the West Coast) but it had the same tweeter as the Tabor so probably sounded similar other than the bass.



If the ScanSpeak was cheaper I would be willing to try it but not at about $250 a pair.
Any other suggestions for magic midrange?


Thanks,
Chris


 
Hi Chris, near Seattle. I am always the first to admit that I am useless at woodwork. Me and power tools tend to end up with more blood and injury than progress! :eek:

Hence I always warm to a well made box. The Lentek S4 looks like a goodie. TBH, the classic 8" bextrene polycone plus 1" Audax 12x9 soft-dome is not the last word in speakers.

I certainly wasn't tempted by the £200 Chartwell PM200 variation:

460727d1421893844-ex-kef-cadenza-kef-t27-b200-chartwell-pm200-jpg


I take your point about the price of the Vifa P21W0 in your neck of the woods. But really, the World is your oyster.

My nephew Dave has a pair of these old classics:

271191d1331481799-complete-ditton-22-rebuild-22s-original-form-jpg


What the heck are THOSE? Nobody knows about them! Paper bass. Ancient Celestion Ditton 22, as it goes. Absolutely beautiful sound. He won't part with them. :D

How's it done? Mainly a midrange enclosure:

271199d1331482287-complete-ditton-22-rebuild-front-rear-jpg


Bit of spongey stuffing for the bass:

271194d1331481799-complete-ditton-22-rebuild-jpg


Much as I love Troels Gravesen and his SEAS 3-way Classic, there is little new under the sun. :cool:
 
A bit of sleuthing reveals you are in Edinburgh, UK.

So this £50 + VAT 210mm Monacor reflex driver might be good and affordable:

Monacor SPH-210 Diameter 210mm

Closed box, the £41 215mm SEAS looks good:

Seas P21RE/P H0942-08 Woofer. H0313 2015 remake

Can you get them to fit? I think you'll want a pair...

But this project will need woodworking and probably soldering to do. And certainly a willingness to learn about crossovers, even though I suspect all that might need adjustment is a £1 ceramic resistor in the tweeter filter for level:

MurphyBlaster Productions
 
Many thanks for this.

What's the old Chinese saying? "Out of adversity comes opportunity!" :D

If I see a decent big 8" speaker box with possibly broken drivers for about £30, I usually buy it.

A version of these Wharfedale Linton are sitting unwanted and unloved over the road. I think I may give them a home... even if they don't work.

681184d1526561181-70th-anniversary-loudspeakers-briggs-wharfedale-linton-jpg


How it works is you can fix most stuff, and speakers like these cost about £500 these days, so what have you got to lose?

Get to work...

640476d1508157614-changing-audio-related-capacitor-speakers-speaker-workshop-jpg


Results can be good:

605216d1489454414-monitor-audio-r352-crossover-monitoraudio-r300-md-jpg


Everybody started knowing nothing. I certainly think those Falcon SEAS units look superb. A giveaway at £41. You'd have to go to Harbeth and spend about £3,000 for a better construction.
 
I've been doing this stuff for about 45 years now. :eek:

But these days it's all done with computer simulators.

Software | Visaton

The basic theory is mathematical. Most people do something called Linkwitz-Riley LR4:

715080d1542008118-restoring-monitor-audio-r300-bookshelf-speakers-steen-duelund-1-414-root-2-png


703136d1536790734-kef-104ab-rebuild-minidsp-dayton-drivers-system7-speaker-fr-png


What you can't see is a thing called bafflestep, which adjusts for the cabinet's bass response. I won't go into that now.

I am a bit of an authority on 8" plus 1" soft dome or 2" cone tweeters, just because I work at them.

Restoring Monitor Audio R300 bookshelf speakers.

Boxsim has an optimiser which does a lot of the work for you. You mark components in red and it just does its thing to align it all. What is for sure, is people will help you if you get bogged down.
 
Stubbs04, just take a back seat, maybe wander off to the bar for a top up, while me and cm6 yak about this crossover.

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Low inductance woofer for sure. A little breakup notch somewhere around 5kHz. All good.

I do stuff like this myself, here with a high inductance woofer.

815982d1581356040-explanation-filter-topology-phase-cross-wlm-clone-plus-ht22-circuit-jpg


815983d1581356040-explanation-filter-topology-phase-cross-wlm-clone-electrical-response-jpg


815538d1581218505-noname-loudspeaker-polite-request-help-identifying-wlm-clone-monacor-ht22-jpg


Bear with me. I think I know where I am going on this....

635880d1505673457-classic-monitor-designs-groovin-blow-jpg


Not everybody gets Jazz. The idea is you just set off, armed with prodigious talent like Miles Davis and John Coltraine in "Kinda Blue", and a tight rhythm section. But in Jazz you never know where you end up, it's less certain on the precise outcome. But it will be good! :D

I'm not even sure if this Lentek S4 is reflex or closed box. But we can fix it.
 
I found a picture of the inside of the S4. I see what you mean about the hunk of wood.


If you're any good at this, you could pull one of your crossovers and trace it out then post it.

You'll have to pull it anyway if you want to replace the Audax's. Plus it would add to the world's knowledge about Lentek's which is almost non-existant.
 
"me and cm6 yak about this crossover"


Well if the current one could just be tweeked a bit that would be cheaper.
The Seas drivers are worth the money but if you add in an all new crossover and woofers stubbs04 might as well get some other decent used speakers of which there are many in England. Less so here.



Not a Diana Krall fan but they are good recordings.
Give me Stacey Kent anyday.
Miles and Coltrane and Bill Evans what's not to like?
 
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