HPM-60 How to check cones & surrounds
- Thread starter c3conv
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There were two versions of the HPM-60, although the differences are likely to cause a debate.
You can see what Pioneer has on their service site for each:
http://parts.pioneerelectronics.com/model.asp?modelNum=HPM-60
http://parts.pioneerelectronics.com/model.asp?modelNum=HPM-60/U2
I have attached photos of each.
If the carbon fiber woofer has been replaced, you will be able to tell. It may be difficult to get replacement carbon fiber cones, if not impossible.
Doc
You can see what Pioneer has on their service site for each:
http://parts.pioneerelectronics.com/model.asp?modelNum=HPM-60
http://parts.pioneerelectronics.com/model.asp?modelNum=HPM-60/U2
I have attached photos of each.
If the carbon fiber woofer has been replaced, you will be able to tell. It may be difficult to get replacement carbon fiber cones, if not impossible.
Doc
Attachments
yamahammer
mikiesmadness continues
nice stuff doc and very helpful
BTW, the first photo is of the second version, and the second photo is of the first version (just hover over the attachment).
The crossover frequencies for each are:
1.20 4.00 12.00 (version 1)
1.90 3.00 12.00 (version 2)
Doc
The crossover frequencies for each are:
1.20 4.00 12.00 (version 1)
1.90 3.00 12.00 (version 2)
Doc
natedogg643
Active Member
yamahammer
mikiesmadness continues
and it will discolor a little bit with age
Fred Longworth
audio fanatic
Be very careful with those cones. They are incredibly fragile!
Engineers consider it a design ideal that a speaker cone have a high order of stiffness and minimal mass. The stiffness makes it resistant to standing waves and other parasitics. The low mass makes the cone both easy to accelerate and easy to decelerate.
Generally, these two factors work against each other. You can stiffen a cone with high mass, but this makes it hard to move around and requires a hefty suspension system -- and this in turn requires a HUGE amplifier. You can make a speaker "sensitive" with low mass, but this makes the cone receptive to secondary vibrations.
On top of this, you want good damping. In other words, if you removed the driving current instantly, you would want the cone as well to stop moving almost instantly.
* * * * *
Historically, the problem with super-rigid-super-low-mass cones is that they were fairly brittle leaving the gate, but became incredibly brittle after a few turns around the track. (Historically, Pioneer used polymer graphite and similar formulations. Now Pioneer features Interlaced Aramid fiber.)
* * * * *
I have repaired cracks in these brittle cones with special speaker glue, but I know in my heart that this did not bring the sound back to spec.
So..............be real careful. And, if the woofers require new surrounds, find someone with a real gentle hand. To refoam a woofer you have to strip off most or all of the original surround material. You can toy with a Cerwin-Vega all day and not worry the cone material; one slip and the Pioneer cone cracks.
Best,
Fred Longworth
owner
StereoTech Classic Audio Repair
http://www.repairaudio.com
Engineers consider it a design ideal that a speaker cone have a high order of stiffness and minimal mass. The stiffness makes it resistant to standing waves and other parasitics. The low mass makes the cone both easy to accelerate and easy to decelerate.
Generally, these two factors work against each other. You can stiffen a cone with high mass, but this makes it hard to move around and requires a hefty suspension system -- and this in turn requires a HUGE amplifier. You can make a speaker "sensitive" with low mass, but this makes the cone receptive to secondary vibrations.
On top of this, you want good damping. In other words, if you removed the driving current instantly, you would want the cone as well to stop moving almost instantly.
* * * * *
Historically, the problem with super-rigid-super-low-mass cones is that they were fairly brittle leaving the gate, but became incredibly brittle after a few turns around the track. (Historically, Pioneer used polymer graphite and similar formulations. Now Pioneer features Interlaced Aramid fiber.)
* * * * *
I have repaired cracks in these brittle cones with special speaker glue, but I know in my heart that this did not bring the sound back to spec.
So..............be real careful. And, if the woofers require new surrounds, find someone with a real gentle hand. To refoam a woofer you have to strip off most or all of the original surround material. You can toy with a Cerwin-Vega all day and not worry the cone material; one slip and the Pioneer cone cracks.
Best,
Fred Longworth
owner
StereoTech Classic Audio Repair
http://www.repairaudio.com
Fred Longworth
audio fanatic
Paper cones are generally not as good.
If I wanted to recover original fidelity, I would either reedge the original woofers or go searching for a spare pair, say, from cabinets that were damaged in shipping.
Fred
If I wanted to recover original fidelity, I would either reedge the original woofers or go searching for a spare pair, say, from cabinets that were damaged in shipping.
Fred
