How to improve the HPM-100/900 cabinet

[Mark W.]

For those who know the Pioneer HPM-100 or HPM-900 speakers a question.

First the back story.

Kelly an AK member decided that I should be the guy to receive a pair of HPM-900's he was playing with. They have as virtually all of these do destroyed cones in the woofers.

I'm thinking seriously about having GordonW (another AK member) rebuild the woofer with a special paper cone he has figured out.

BUT the cabs on the 900's are not only beat but lack even the structural design of the 100's. So I'm thinking about building my own cabs for the HPM-900 drivers and crossovers.

Due to the requirements of our system and living room the cabs will have to be exactlyt he same size as the HPM-100's cabs they would be replacing. 15.5" X 15" X 26"

So do I try to duplicate the 100's better cab? Or do I try to improve on something? heavier walls? more internal bracing? Different Porting?

I will be doing the cabs with either real veneer over some type of particle borad or Plywood (do I want a stiffer cab?) or I have thought about layering particle board with 1/4" Walnut plywood over top using solid walnut corners and edges.

So anyone who's into speaker cab design got any ideas on how to improve a HPM-900's cab?

So you know I have pretty much any woodworking tools or skills needed to do almost anything.

 

[kfa888]

WOW, Kelly gave you free HPM900's, that's one hell of a guy

Boooohaaaaahaaaaaa

I did purely because I figured the good Karma would land me some Magnepan Tympani's he he he. No one has called me to pick them up yet :tears: I guess no instant Karma.

 

[Zilch]

Mirror-image.... :yes:

 

[Gibsonian]

Bracing is what you need to improve the HPM 100/900 cabinet. Maybe some internal damping material (vinyl, asphalt, etc) with a more generous supply of polyester than Pioneer supplied orginally on top of that to boot. Hopefully you can enlarge the cabinet a bit to account for any bracing you put in, otherwise volume changes as does speaker performance.

I have a pair of Pioneer DSS-9 speakers and the walls are super dead when you rap your knuckles on the side, much different than the HPM 100 cabinet -it is quite lively. The DSS-9's internal bracing is main reason why, even though the rest of the cabinet construction slightly favors the HPM 100. Thicker walls are good as well but not as good bang for buck as internal bracing. Since you are making new you could countersink the drivers to the driver board if you wanted to as well. Hope you post pictures when you are done.

 

[dc270]

Speaking from experience- the HPM 100's have real nice 1" thick baffles! That is a great start, I am a proponent of a sand filled (AKA Wharfedales) back baffles with good 2" x 2" internal cross bracing. I take the circle cuts from the drivers cut outs ( I save them for this reason) and glue them inside to brace the 2" x 2" to. The cabinet regidity is much improved. Like the DSS 9 mentioned above, the DSS 7's I just got are also well made cabs, but could use a bit more for my tatse.

I have buit custom cabs with full 1" thick walls using 3/4" and 1/4" MFD with heavy felt paper between them that worked pretty well. IF you use plywood use a good marine void free grade other wise rattles and buzzes will plague. you. Old Klipsch 9 ply was good at one time.

You ARE on the right track with an improved cabinet, wished more builders were aware of this. Good luck!
DC

 

[JBN]

I vote to sell them and buy a new speaker!

 

[dc270]

For those who know the Pioneer HPM-100 or HPM-900 speakers a question.

First the back story.

Kelly an AK member decided that I should be the guy to receive a pair of HPM-900's he was playing with. They have as virtually all of these do destroyed cones in the woofers.

I'm thinking seriously about having GordonW (another AK member) rebuild the woofer with a special paper cone he has figured out.

BUT the cabs on the 900's are not only beat but lack even the structural design of the 100's. So I'm thinking about building my own cabs for the HPM-900 drivers and crossovers.

Due to the requirements of our system and living room the cabs will have to be exactlyt he same size as the HPM-100's cabs they would be replacing. 15.5" X 15" X 26"

So do I try to duplicate the 100's better cab? Or do I try to improve on something? heavier walls? more internal bracing? Different Porting?

I will be doing the cabs with either real veneer over some type of particle borad or Plywood (do I want a stiffer cab?) or I have thought about layering particle board with 1/4" Walnut plywood over top using solid walnut corners and edges.

So anyone who's into speaker cab design got any ideas on how to improve a HPM-900's cab?

So you know I have pretty much any woodworking tools or skills needed to do almost anything.

Are these those graphite ceramic cone woofers? If so what size? I just sent my DSS 7, 12" woofers to Simply Speakers to get a full recone for the broken ones I had- maybe they can do yours as well! They were pretty reasonable to do them. They were the ONLY one I could find that had a few cones left to do the recone with.
DC

 

[Mark W.]

I like the mirror image idea, I also like the more internal bracing idea. And after thinking about it a bunch today (when you drive a dump truck 452 miles you have a lot of time in a day to think!) I can increase the internal volume by making the speakers deeper front to back. I can increase them almost a full inch which would give me an additional 340-345 cu inches of volume to use for bracing or what ever.

And Tom you need to understand the rules of the test before you write out your answer. Sorry 0 credit you can retest anytime.

DC I have thought about the idea of exact replacement cones but given their history of being fragile and have two grand daughters coming over a LOT. I think GordonW's treated paper cones will suit me very well.

 

[dnewma04]

Mark, Is there any chance that you can keep them same footprint and increase the height? If so, I'd be tempted to actually rebuild cabinets from scratch and stack the drivers vertically, with some offset from center position on the baffle. Beyond that, bracing/mass loading are pretty effective, as pointed out by many others. I also wonder what improvements going over the crossovers might make for you.

 

[Mark W.]

The height is one thing that would be hard to increase due to the speakers position in the room. With the left speaker actually sitting on the bottom step of our stairs and there being a stub wall on the other side. It makes the bottom two steps very narrow. Right now at 26" it's about the limit of lifting a laundry basket etc. over the speaker to go up stairs.

The right speaker is almost in the opening for the SHRINE so to increase it's height would block the view of the system Granted not as big f a deal but since the left can't change the right won't either.

As to the cross overs I could be interested in refreshing them when I get near that step I'll be asking a lot of questions. I do know the 900's improved cross over is a big part of the sound improvement over the 100's.

 

[needforspeed]

When I have the covers off, It always strikes me the baffle looks "Crowded". Like the drivers are to close together. The cabinet seems very solid, All the corners are braced, The sides are tied togather. Maybe increasing the depth is the answer. I think the sound between the two speakers rests with the midrange driver. The second gen speakers have a much bigger magnet, And the voice coil looks slightly bigger (wider). If I can ever find a hpm 700/900 midrange, There going straight into my speakers. Just have to enlarge the opening about a 1/4 in. For the most part Bart Locanthi, Had it right, IMO.

 

[dnewma04]

If you get a chance, measure the drivers and see what it would take to align them. It almost looks like the mid and tweet could be done as is, then maybe make a small pod housing the tweeter on top of the enclosure. Wouldn't add much to the effective height of the enclosure.

 

[rushfan]

When I have the covers off, It always strikes me the baffle looks "Crowded". Like the drivers are to close together. The cabinet seems very solid, All the corners are braced, The sides are tied togather. Maybe increasing the depth is the answer. I think the sound between the two speakers rests with the midrange driver. The second gen speakers have a much bigger magnet, And the voice coil looks slightly bigger (wider). If I can ever find a hpm 700/900 midrange, There going straight into my speakers. Just have to enlarge the opening about a 1/4 in. For the most part Bart Locanthi, Had it right, IMO.

I could be wrong, but I think that the midranges are the same size in the 100/700/900. I bought a pair of 700/900 mids on E-Bay and they dropped right into my 100's. They are a little different cosmetically, but fit perfectly.

Are the mids from the 700/900 supposed to be better than the 2nd generation HPM-100 midranges? I thought that it was the tweeter that was the most improved part.

 

[needforspeed]

I could be wrong, but I think that the midranges are the same size in the 100/700/900. I bought a pair of 700/900 mids on E-Bay and they dropped right into my 100's. They are a little different cosmetically, but fit perfectly.

Are the mids from the 700/900 supposed to be better than the 2nd generation HPM-100 midranges? I thought that it was the tweeter that was the most improved part.

I read on this forum it made a difference, It's worth a try. Also have read changing the tweeter was also worthwhile. I used an eq to tune my speakers, So there set for me. The consruction of the 700/900 drivers seem better, Except for the woofer. I've also read the supertweeter actually accomplishes something, Vice the 100 driver. I have all these drivers collected, Except 1 midrange. There all going into my speakers asap.

 

[Mark W.]

As to the idea of lining up the drivers I'll take a look when I get into it what if I angled the mids and the tweets towards one corner that would give me a little more room to work with. And Dave I need to keep a flat top on the cabs since they end up getting used as tables! The right one is the only place I have near the SHRINE to open an LP and the other I allow the wife to set things headed upstairs. I know I know but we all have to make a few concessions to keep the home a happy one!

 

[Gibsonian]

The tweeter on the HPM100 is it's weakest link, no doubt. The HPM 700/900 tweeter/supertweeter combo is much sweeter sounding.

 

[Mark W.]

OK working with a couple of ideas as to driver alignment I did a couple of rough sketches.

The first shows the smaller drivers lined up along a 45 degree line which will fit within a 28" tall cab (2" taller then stock and within Wife approval spec's)

The second shows the drivers lined up vertically along the centerline I would need to stretch the cab to at least 30" I think to make this work. That would end up getting into the problem area of access to the stairs when carrying stuff and seeing the right half of the SHRINE while sitting in the sweet spot.

Pretty sure unless there would be a noticeable advantage to the vertical alignment I won't be going that direction.

 

[Zilch]

There is an extensive section of Dickason devoted to driver alignment on baffles.

I don't believe your layouts would make the cut, alas....

http://audiokarma.org/forums/showthread.php?t=128981

 

[e2e4c7c5]

The tweeter on the HPM100 is it's weakest link, no doubt. The HPM 700/900 tweeter/supertweeter combo is much sweeter sounding.

Absolutely correct, IMO.
I had both speakers at the same time and I thought the HPM900 was better in the high-end while the HPM100 had a better bass sound to it.
Both are terrific speakers and they made a nice combo but for looks the HPM900 was a plain jane while the HPM100 was hot girl next door.

 

[Mark W.]

OK I did some serious thinking and came up with a possible way to have vertically aligned drivers within the 28" max height I have to work with.

By trimming the aluminum plate around the tweeter I can gain about 1.25" of vertical room just enough if I space the drivers close to each other. See the following photo's.

NOW if someone can tell me why trimming the tweeter flange as shown with the cropping in the photo would effect the sound I'll rethink.