Pioneer HPM-40s

[Donald K]

Hello everyone,

This seems to be an extremely helpful forum, i've been getting a lot of hits when searching various speakers.

So, I have two hpm-40s that I was given and I went to test them out, but their tweeter (not super tweeter) are broken. I took them in to Stereo Rehab in Chicago, the owner was more than helpful and gave me some back story on the speakers as well.

My question is: can I get away with replacing them with the "copy cat" tweeters here? They are 6ohm instead of the 8ohm that are inside of them currently.

Are they worth replacing? Should I just invest the money into a different set of speakers?

TIA!

 

[HPMguy]

OEM tweeters appear on eBay fairly often, I'd go with those.

Note that the "super tweeter" if present appears open to an ohmmeter..

Check the suspension foam on the woofers, if at all dubious (as it will be if not replaced yet), DO NOT power them up until you get the cones re-suspended. Burned voice coil is almost certain if the foam is bad. My original HPM 500's had the foam die in less than ten years. Replacements seem to last longer.

 

[kryten79]

^^^ what he said. Buy a matching pair of tweeters, recap and refoam and try them out for a few months. I still have my 40s bought new. They're not audiophile flat perfect, but they are fun and still crank.
As you may have discovered, there are two versions these,
HPM-40, Crossover SWN-108, Tweeter 45-710A
HPM-40 /u1 (or gen 2), Crossover SWN-154, Tweeter 45-711B
The two tweeter versions are so similar it doesn't matter if you replace one pair with the other, you won't hear a difference.
I use soniccaps and mills but everyone has their preference. You may want to check resale prices to put a "cap" on your expenditures for parts if you think you might move them along.
You should be able to hear the supertweeter with a paper towel roll or stethoscope, turn the bass all the way down and the ST pot up. The transformer in the circuit makes the ST un-ohmable as HPMguy stated.

 

[TimF]

I always will have a soft spot for HPM 40’s, they were my first “real” set of speakers somewhere around 1979 or so. Always liked the nice veneer, not to mention the overall sound of them. Solid buggers too.

 

[HPMguy]

I bought a pair of HPM 500's in 1982 or so, still have and use them with new surrounds. Still sound great. Probably the equivalent of the 60's I think (three way). Very rarely hear anything I like better.

 

[Thorsten R.]

HPMguy, the HPM-40 (and also the HPM-50) did not have foam as material of the suspension. They had woofers made from "natural" materials that in my experience lasted a lot longer. The HPM-500 had membranes from polymer graphite with foam suspension very alike the related S- series (S-510 as direct successor). The foam e.g. in my own S-1010 literally transforms into dust.

In the times those speakers were new I sold and repaired them in my father´s shop. The series from HPM-40 to S-510 was in my ears extraordinarily good (especially when you looked at the price) and real fun.

 

[bigx5murf]

I bought my HPM-500 with both tweeters missing. I found an original pair of replacements on eBay for what your single copy cat cost.

 

[HPMguy]

That would make the HPM 40 a better buy as far as I'm concerned! My 500's were bought new in 1982, and by 1992 the foam was starting to fail. Fell apart completely after I moved home in 1993.

Wonderful sound though, and they are still very nice now that I've replaced the foam.

 

[FluxT]

HPM40’s are arguably the sweet spot of the HPM lineup. Nice punchy clean sound, without the shrillness or dispersion issues of the HPM100’s, or the foam issues of the earlier/later models. Not the best for critical listening, but extremely fun once you dial ‘em in.

 

[Donald K]

^^^ what he said. Buy a matching pair of tweeters, recap and refoam and try them out for a few months. I still have my 40s bought new. They're not audiophile flat perfect, but they are fun and still crank.
As you may have discovered, there are two versions these,
HPM-40, Crossover SWN-108, Tweeter 45-710A
HPM-40 /u1 (or gen 2), Crossover SWN-154, Tweeter 45-711B
The two tweeter versions are so similar it doesn't matter if you replace one pair with the other, you won't hear a difference.
I use soniccaps and mills but everyone has their preference. You may want to check resale prices to put a "cap" on your expenditures for parts if you think you might move them along.
You should be able to hear the supertweeter with a paper towel roll or stethoscope, turn the bass all the way down and the ST pot up. The transformer in the circuit makes the ST un-ohmable as HPMguy stated.

By recap them do you mean recap the crossover board capacitors that are for the tweeters? Or are there capacitors on the actual tweeter itself?

Also, by refoam do you mean refoam the tweeter? I thought you would only refoam the sub, but I'm also a novice to this.

 

[Donald K]

I bought my HPM-500 with both tweeters missing. I found an original pair of replacements on eBay for what your single copy cat cost.

Whoa, that's a steal. I found one OEM tweeter on eBay for around $45, but haven't found a second OEM as of yet. I might pull the trigger and buy that one and wait for another one to pop up.

Do you know of any other pages that sell parts other than ebay or something like a facebook marketplace?

Excuse my ignorance, I'm just very new to this. My mom gave me these awhile back and I just got around to hooking them up for listening to records.

 

[Donald K]

HPM40’s are arguably the sweet spot of the HPM lineup. Nice punchy clean sound, without the shrillness or dispersion issues of the HPM100’s, or the foam issues of the earlier/later models. Not the best for critical listening, but extremely fun once you dial ‘em in.

How would you go about dialing them in? Are you saying on the receiver or pre-amp you're putting them into? Or changing out parts such as caps?

 

[bigx5murf]

Whoa, that's a steal. I found one OEM tweeter on eBay for around $45, but haven't found a second OEM as of yet. I might pull the trigger and buy that one and wait for another one to pop up.

Do you know of any other pages that sell parts other than ebay or something like a facebook marketplace?

Excuse my ignorance, I'm just very new to this. My mom gave me these awhile back and I just got around to hooking them up for listening to records.

For very specific parts like this, eBay is still the best bet. Save your searches, with notification. Also make sure to do so for other HPM models that use the same tweeters. There have been stuff I waited years before a notification suddenly came that part was listed, and I jumped quick.

 

[kryten79]

okay.....
Oaktreevintage does not have the tweets at the moment. Like smurf said, set a search on the auction site for the part numbers (45-710A, 45-710B, 45-711B or 45-711C), or Pioneer HPM Tweeter (the 60s and 100s use the same tweeter) post WTB in AK (need to be a subscriber to post) and USaudiomart. I don't believe you would hear the difference if you have two different P/N but most of us would try to find a matching pair with close ohm readings

Crossovers are built from resistors, capacitors and inductors to split or filter the frequencies going to each of the drivers. The crossover board for the 40s is dead simple with lots of room to work. Inductors don't go bad until the wire breaks, capacitors generally do age poorly, resistors usually don't go bad but most people replace them as well. The crossover diagrams can be found many places but you need to know whether you have the regular 40s or the overseas /u1 version. HiFiEngine should be bookmarked as a source for manuals and schematics. Plan to replace the binding posts while you're in there. Use 3/8" foam weatherstrip behind the drivers when you reinstall. Rotate the woofers 180 degrees/upside down when they go back in.
The insulation in the cabinet is stapled to stay behind the ST and Tweet. You should not need to replace the internal wiring.
Assistance on soldering and component mounting to the crossover board is out there or AKers will help.
Mouser, Parts connection, parts express, madisound or Soniccraft are a few sources for parts, equipment and materials. Your choice depends on your budget and taste - lots of opinions

Refoaming is the replacement of the material around a driver between the frame and cone. Visually inspect for rips, tears or disintegration. Many Tweeters have pushed in or dented dust caps, the center of the cone. Doesn't affect the sound and can be replaced or repaired (sometimes).

search crossover solder for guidance, 1st few links going to audiocircle or diyaudio look right to help you build out your toolbox and skillset. Lots of youtube vids are out there too. Or you can just ask here.

 

[FluxT]

How would you go about dialing them in? Are you saying on the receiver or pre-amp you're putting them into? Or changing out parts such as caps?

I meant just turning the tweeter knob down a few clicks, since it’s way too hot in the “0” position. I liked it best around -3 or so, but I’ll let your ears be the judge-I mostly listened to them when I had a very bright, reflective space. However, recapping and amp pairings will also help bring the best out of them.

 

[Donald K]

So for right now, I ended up buying this Midwest Electronics tweeter to test it. All of the other tweeters 45-711A/B/C had dented cones for $35-70 so i opted for a new one. I will test this and see if it works as well as measure the impedance across it. If it works, I might as well buy a second from them as well. I don't see why there should be much of a difference, but I'd prefer not to have a dented cone for aesthetics.

If I can get them both working, i'd love to discuss improvements that could possibly be made to these speakers! Thank you guys for helping me thus far, this has been an awesome experience researching into these pioneers.

 

[Thorsten R.]

Most important is a sensible placement of these speakers (well, when I think about it this is crucial for all speakers...).

 

[FluxT]

So for right now, I ended up buying this Midwest Electronics tweeter to test it. All of the other tweeters 45-711A/B/C had dented cones for $35-70 so i opted for a new one. I will test this and see if it works as well as measure the impedance across it. If it works, I might as well buy a second from them as well. I don't see why there should be much of a difference, but I'd prefer not to have a dented cone for aesthetics.

If I can get them both working, i'd love to discuss improvements that could possibly be made to these speakers! Thank you guys for helping me thus far, this has been an awesome experience researching into these pioneers.

One mod that some folks do with these is adding a resistor across the tweeter to pad it down. I never did it, because turning the tweeter dial down a few notches accomplished the same result and can be adjusted to taste. Aside from that, not much else to do but enjoy them for what they are-punchy mid-sized speakers that still sound very modern despite being 40 years old now. They're not ideal for sitting back with an aged scotch and picking apart the nuances in a Miles Davis record, but feed them good rock, pop, or electronica, and you'll be grinning ear to ear for years to come.

 

[moebuster]

HPM40’s are arguably the sweet spot of the HPM lineup. Nice punchy clean sound, without the shrillness or dispersion issues of the HPM100’s, or the foam issues of the earlier/later models. Not the best for critical listening, but extremely fun once you dial ‘em in.

Agreed. The HPM40 impress me with solid punchy bass.

 

[crdm6]

All this talk about HPM-40's made me dig mine out and hook them up. I have the /U1 model with the cast frame woofer and tweeter. Tweeter set to -3, on platforms about a foot of the floor, fire up Steely Dan Aja and I'm transported to a third row seat. Lately I've been listening to classic KLH's which sound like you're about half way back in the auditorium. Not bad but I would differ on the "solid punchy bass". Reminds me of the HPM-100's and JBL L-100's. Hmmmm. But first they should be recapped. So I opened one up to assess the situation.

No gaskets on the woofer or tweeter which is ??? but the precision of the cast metal and front board makes for a tight fit.
Both the woofer and tweeter are things of beauty. Everything is very high quality. Thanks Bart Locanthi!
Whatever glue they used was also high quality. I may have to disconnect the old caps and leave them in there and solder the 2 new ones over them. Eh.
L-Pads OK but if I can find my De-Oxit I'll hit them. I may change the woofer coil out for a same value, lower resistance one at some point.

So, time to test the drivers for T/S parameters. Frequency response tests later.
Skipping the tech stuff, the box is too small for the woofer just like the HPM-100's and L-100's. Gotta get that bass sound!
Actually the boxes are even too small for an optimum acoustic suspension alignment.
Aperiodic to the rescue. I decided to follow the lead of someone smarter than me.

http://www.troelsgravesen.dk/JBL_L100_08.htm

I took some low density fiber-fill, rolled it up and stuck it in the ports. Probably not optimum but a very fast feasibility test.
Do they have "punchy" bass now? No, but it is much more realistic. I can now hear string sounds from stand up bass and I would say "tighter" rather than "punchy". Much better I think.
I also might put a bit of fiber fill behind the tweeters to see if it improves the mid-range any.

For now, the recap and optimize the port stuffing. Maybe later more monkeying with the crossover.
Moving on up to the first row.