How to Train Your PM180-8

[dustinbagby]

Re: How to Train Your PM180-8

The results are certainly there, but I couldnt bring myself to take a knife to a ~$100 driver for what could have been a bust. Kudos to you

[Rory Buszka]

Re: How to Train Your PM180-8

The Scan-Speak cones and dust caps are die-cut. There are actually two layers of paper on the cone, and they are glued together with a rubber-type adhesive (the same stuff often used for attaching dust caps; it's a solvent-borne rubber cement that dries black.) The slits in the lower paper cone run the opposite direction from the slits in the upper cone. But anytime you apply adhesive (including damping compounds), it's a major opportunity for inconsistency from unit to unit. The adhesive needs to be carefully metered and evenly spread.

What has worked for me in the past when using the PM180's brother, the PS180, was to employ a contouring filter to tame down the midrange to taste. No modification of the cone was necessary. With the PM180, you can cross over lower and with a higher order filter slope, and achieve something similar, but I think it could be employed to a higher frequency if a contouring filter was used to shelve down the midrange rise. When I heard the Derecho, what I heard was extremely dynamic and had very good resolution, and the PM180-8 was complementing the RAAL ribbon quite well as both are fairly low-mass drivers (though the ribbon much more so). As I recall, it was more dynamic sounding (IMO) than any of the other smaller Vapor models I've heard, though the Perfect Storm is also a very dynamic speaker. When you can compare a $99 midbass favorably to units costing several hundred dollars, that's quite a coup in my opinion.

That Enjoy The Music review is quite short, and doesn't seem very thorough to me. If that pair of Derechos is still kicking around (not sold yet), then I wonder if Srajan at 6moons would be interested to finally review a Vapor speaker.

[dcibel]

Re: How to Train Your PM180-8

I don't think its an overpriced driver. Its an excellent performer. Putting something like this cone cutting into production screams QC consistency issues to me because its a completely manual process. Revelators are as expensive as they are for good reason IMO.

[Pete Schumacher]

Re: How to Train Your PM180-8

Yes, it would be nice to see a 5" version of the PM180. $40 would be a good price range.

Pete, you mentioned cost for the 3rd time here, but this is DIY. All it cost me was 3 cents worth of caulk and a few minutes of sadistic joy with a knife.

I realize you are defensive because you have a commercial design that uses this driver, but it's pretty obvious that others have discovered it's sonic weaknesses as evidenced in this review. By the way, I saw that review for the first time just now while looking for the Vapor Derecho link.

You've been very helpful, and I'd love to help if you and Ryan want to take that mid to the next level. Think of all the expensive crossover components you will save while providing your customers a more enjoyable listening experience. I'm quite serious, but I would expect to be paid in RAALs.;)

I was responding to someone early on who wondered why the driver was so expensive already. Not defending our design but trying to explain to the original query that adding those steps to the process of making the driver would drive up costs even more.

And attempting LR2 will require a recessed tweeter to shift it back. A nice shallow waveguide would be very beneficial.

[Pete Basel]

Re: How to Train Your PM180-8

I have done slightly different angles and patterns, but I don't see the need to deviate from prior experiments, since it works so well. S-shaped slices would probably work too, but I like the current look. The important part is to have enough slits.

Here is the progression from baseline(blue) to 5 slits(navy) and 10 slits(red). This is before the pole cavity plug was added.

[ATTACH=CONFIG]57896[/ATTACH]

Nice work, excellent, thanks for explaining further.
I really prefer smooth response drivers.

Have you seen this guys work, he also posted a lot on DiyAudio:
http://madspeaker.com/page17.html

http://madspeaker.com/page18.html

He goes by MarkMck on DiyAudio:
http://www.diyaudio.com/forums/full-...band-mods.html

I remember him doing mods to the Vifa P17 but can't seem to find them.
His methods are different but he seems to also get excellent results.

[jbruner]

Re: How to Train Your PM180-8

These drivers seem really overpriced at this point. I wonder if the performance before modification justifies the asking price. At this point would you even consider owning these if you were somehow prevented from modifying them?

Tough question. I do think they are overpriced, especially since the driver's design is incomplete. It looks like they just removed the pole extension from the PS180 and slapped on a dustcap. The resulting pole cavity is a glaring problem visually and acoustically. I hate it when pricing is based on market positioning rather than value.

I would not have tried them, but, a) They were on sale, b) Ryan and Jeff both thought they were good, and, most importantly, c) I knew I could fix them if I needed to.

I really wanted to design a high-output speaker that could deliver realistic dynamics with high fidelity. I concurred with most of the design choices in Vapor's Derecho, and even used the same B&C woofers.

[jbruner]

Re: How to Train Your PM180-8

I'm not against the mods that have been done, don't get me wrong. But to incorporate them into the design of the driver doesn't really produce any benefits under normal use for a 7" midrange. It would only drive up the cost.

It would be nice to see a 5" version of that driver.

Yes, it would be nice to see a 5" version of the PM180. $40 would be a good price range.

Pete, you mentioned cost for the 3rd time here, but this is DIY. All it cost me was 3 cents worth of caulk and a few minutes of sadistic joy with a knife.

I realize you are defensive because you have a commercial design that uses this driver, but it's pretty obvious that others have discovered it's sonic weaknesses as evidenced in this review. By the way, I saw that review for the first time just now while looking for the Vapor Derecho link.

You've been very helpful, and I'd love to help if you and Ryan want to take that mid to the next level. Think of all the expensive crossover components you will save while providing your customers a more enjoyable listening experience. I'm quite serious, but I would expect to be paid in RAALs.;)

[jbruner]

Re: How to Train Your PM180-8

Nice work, I like it. Did you experiment much with the angle of the slits or do they just need to be roughly placed?
Is there a guide written up somewhere?

I have done slightly different angles and patterns, but I don't see the need to deviate from prior experiments, since it works so well. S-shaped slices would probably work too, but I like the current look. The important part is to have enough slits.

Here is the progression from baseline(blue) to 5 slits(navy) and 10 slits(red). This is before the pole cavity plug was added.

[Pete Basel]

Re: How to Train Your PM180-8

Nice work, I like it. Did you experiment much with the angle of the slits or do they just need to be roughly placed?
Is there a guide written up somewhere?

[jbruner]

Re: How to Train Your PM180-8

It's interesting that the slits make an even bigger difference off-axis.

I can't see any negatives really. Lower distortion, easier to crossover and a smoother on/off-axis response - What's not to like?

The big question is; What do they sound like subjectively?

I would agree, no negatives. It looks better and sounds better. I lived with the stock driver in my 3-way for many months and finally decided I had to do something about it. I'm really glad I did. The sound is simply amazing. In the words of my very critical wife, it is now a world-class speaker. She said she could see the individual players in the orchestra. For me it went from, " wow, this is loud and clear, I think this will be a good speaker if..." to "luxury, I just want to listen some more." No more worries about what complicated crossover trick to try next. I saved 6 components per side!

[fatmarley]

Re: How to Train Your PM180-8

It's interesting that the slits make an even bigger difference off-axis.

I can't see any negatives really. Lower distortion, easier to crossover and a smoother on/off-axis response - What's not to like?

The big question is; What do they sound like subjectively?

[caleb]

Re: How to Train Your PM180-8

I can not find anything to indicate that Scanspeak has a patent on the sliced cone. Scanspeak always points out patents like the Symmetric Drive SD-1 so if they had one on the sliced cone I think they would say so.

The following is from Scanspeak at no point do they say patented.

"The sliced paper cone technology represented a breakthrough in midrange clarity and overall smooth frequency response characteristics. The slices are filled with damping glue, which dramatically reduce break-up modes in the diaphragm.

The design of the Revelator sliced diaphragm has also been attempted to be copied. The lack of an application of damping to other designs keeps the copycats from providing a quality driver."

[jbruner]

Re: How to Train Your PM180-8

Did you test it with just the plug? Wondering which mod had the most affect.

The plug makes an audible difference. The slits have a greater effect, but that cavity resonance really needs to be taken care of. Many woofers have problems in this area. I zoomed this in so you can see with(red) and without(blue) the plug.

[jbruner]

Re: How to Train Your PM180-8

If you use it in a "normal" band for a 7" driver, the stock performance is just fine. You don't typically drive a 7" woofer past 2KHz due to off axis directivity problems. So if you focus on the performance below 2KHz, it's really an excellent driver with very low distortion and smooth response. While the mods do improve the performance higher up, doing so will wind up making the driver cost even more, not to mention running into patent problems with the slit cone.

Just because you cross a driver at 2k doesn't mean you are not hearing it higher up. Especially if you like LR2 crossovers, and I know you do. Filtered measurements are now up in post #2.

[Pete Schumacher]

Re: How to Train Your PM180-8

2KHz. Any higher and you get into narrowing directivity problems, like any 7" woofer.

I'm not against the mods that have been done, don't get me wrong. But to incorporate them into the design of the driver doesn't really produce any benefits under normal use for a 7" midrange. It would only drive up the cost.

It would be nice to see a 5" version of that driver.