How to Train Your PM180-8

[jbruner]

The Dayton PM180 is a pretty decent midrange driver, but let's see if a little corporal discipline can make it more civilized.



The slit method is described in this thread-Scan-Speek 4" for 49 cents?
A wooden plug is fitted to the pole piece. Here is before and after on a 11.5" baffle with 1.5" roundovers. On-axis-



Blue is original, Red modified. You can see that everything below 2k is the same, which is true for all the measurements to follow, but they will be separated by 10dB for clarity.

30 Degrees off-axis-



45 Degrees-



60 Degrees-

[jbruner]

Re: How to Train Your PM180-8

Below we will examine the drivers with crossover in place. Each driver is matched to LR2 acoustic targets at 350 and 2300 hz, just like I would use them in my 3-way. The stock driver takes 4 more components than the modified. Additional notch filters can make the stock driver a little better on-axis, but I kept this test as simple and practical as I felt necessary.

On-axis-



30 Degrees-



45 Degrees-



60 Degrees-

[caleb]

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?

[Face]

Re: How to Train Your PM180-8

The PM220 could also use these mods.

Awaiting more details.

[killa]

Re: How to Train Your PM180-8

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

[Pete Schumacher]

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?

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.

[fatmarley]

Re: How to Train Your PM180-8

not to mention running into patent problems with the slit cone.

Do Scanspeak have a patent for the slit cone? I think that slit cones were used on a commercial product before Scanspeak.

[fatmarley]

Re: How to Train Your PM180-8

The PM220 could also use these mods.

Was thinking that myself. Not sure if I'd have the courage to risk it though...

[Pete Schumacher]

Re: How to Train Your PM180-8

Do Scanspeak have a patent for the slit cone? I think that slit cones were used on a commercial product before Scanspeak.

You could be right. Still, adding that step to the process would just drive costs up for limited benefit. Yeah, it looks better above 2KHz, but you wouldn't use it up there anyway.

[monkish54]

Re: How to Train Your PM180-8

Pete,

How low is it crossed in your Vapor offering?

[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.

[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.

[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.

[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."

[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?