Author Topic: Question about WTP900 and Compatible Cabinets  (Read 1020 times)

Offline RayOwen

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Question about WTP900 and Compatible Cabinets
« on: March 29, 2017, 11:41:44 PM »
I want to purchase the WTP900.  My current cabinets (which I would like to keep) are:

Ampeg PN 210 HLF:

550 watts RMS power handling @ 8 ohms
1″ Eminence APT:50 HF driver w/L-Pad level control

Ampeg PN 115 HLF:
15″ custom US-made Eminence LF driver
575 watts RMS power handling @ 8 ohms
1″ Eminence APT:50 HF driver w/L-Pad level control

My question is ... are these cabinets compatible with the WTP900?  If I run them both in it will be a total load of 4 ohms so will I realize the 900 watt rated power in mono or stereo.  I am a bit confused about the "bridging" of the amps.  Can someone explain this to me and tell me if my cabinets are compatible? 

Offline Rip Van Dan

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Re: Question about WTP900 and Compatible Cabinets
« Reply #1 on: March 30, 2017, 01:50:07 PM »
Hi RayOwen,

Welcome to the Garden!

The WTP900 is a dual power-block amp, so it has two discrete power channels in it.  Each channel can be run down separately to a minimum of a 4 ohm load and will deliver 450-watts RMS into a 4 ohm load.  You can also run it bridged, which combines the two power sections to double the power (900 watts RMS).  But you can only bridge it into an 8 ohm load.   You can plug in a single 8 ohm cab into that and it will deliver all the power (total of 900-watts) into that single cab in bridged mode. 

Normally, hooking both of your cabs into it using the standard parallel connection and running it in bridged mode would produce a 4 ohm load though, which would overheat the amp and could easily damaged it.  So this amp has some protections built in.  When you plug in your 8 ohm cabinets into the appropriate output in the back it will automatically light up the other output sockets to use.  Then, with two 8 ohm cabs plugged in, instead of using the normal parallel connection (would lower the ohms load to 2 ohm and melt everything), it uses a serial connection, which adds the two 8 ohm loads together to make an 16 ohm load.  It is safe to run your two cabs this way, but since it is putting a 16 ohm load on the amp instead of a 4 ohm load, the power will drop to about 450-watts or 225-watts per cab.  You would get the same amount of power out of this amp if you just plugged both of your cabs into one side of the amp and did not run it bridged.

Now, if you plug your two 8 ohm cabs into separate sides (we call this dual-mono), you will not only get more power (240 to 280-watts?) per cab, but you also can use the balance knob on the back of the amp to control the mix of sound you get from the two cabs.  If you want more of the 115 sound in the mix, you turn it a couple of clicks towards the 115 cab.  If you want more of the 210 sound, you move that knob a couple of clicks towards the side the 210 is plugged into.  This is a really nice feature.  For a while I used a 410 and 115 cab and the GK115 cab I used was a very boomy cab.  My older WT500/800 is also a dual power-block amp and with that balance knob (on the front of my amp)  and turning it two clicks towards the side with my 410 cleared up the boomy sound in the bottom end without any need to mess with the EQ settings.  I liked to call it the "magic" knob.  So that would be the best way to run your cabs with the WTP900

If you want to get a full 900 watts out of the amp running bridged you can either get a single 8 ohm cab like the D410XST (full 900-watts into one cab), or run two 4 ohm cabs into it (450 watts into each cab).

Dan
Rip Van Dan
Dan Gracia
'82 US-made Fender Jazz Bass with maple neck
5-string Rogue LX405 Pro (Surprisingly good "no-name" bass)
WT500/800 Highwayman (signature model)
D.N.S 410-8, Eden EX112 x2
Line6 G10s wireless
==
spares:
Eden RS400, GK BK250, BPX115 cab, acoustic B410 cab, Sunn Beta 202 (2x12)

Offline Rip Van Dan

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Re: Question about WTP900 and Compatible Cabinets
« Reply #2 on: March 30, 2017, 02:06:30 PM »
You know RayOwen, another option would be to buy one of the previous WT800C amps used.  It will go down to 2 ohms per side and will bridge to 1100 watts into a 4 ohm load.  You can plug both your 8 ohm cabs into the bridged output and it will deliver 550-watts into each cab.  HOWEVER, you have to be a little more careful with this amp than the WTP900.  One thing you have to do is be sure you turn it off before you put it into or take it out of bridged mode.  Not a big deal actually as I have to do the same thing with my amp.

Also, you have to be sure you get a model C and not a "version B, C, or D" of the WT800 model A.  If the WT800 you're looking at has banana plugs on the back, it is an "A" model which can only be bridged into 8 ohms.  You would need to run your cabs in dual-mono and can't run them bridged.  If it has Speakon connectors on the back AND has a backlit Eden logo on the front (we call it the "porch light"), that is a "C" model which can safely bridge down to a 4 ohm load.  There are also some "B" models that can run to 4 ohms bridged and they will say on the back "4 ohm minimum bridged" right next to the bridged output.

To make things more confusing, when Marshall bought Eden, they decided they didn't feel safe saying the WT800 could bridge down to 4 ohms, even though that it had been run that way by lots of folks for about 6-7 years at the time.  So they changed the writing on the back by the bridged output to say 8 ohm minimum ohms load.  They didn't change the amp at all, just the writing on the back - same amp, same capabilities.

This can be confusing, so if you are considering purchasing one and you have any questions, post pictures of both the front and the back of the amp here and we can help you identify it.

Dan
Rip Van Dan
Dan Gracia
'82 US-made Fender Jazz Bass with maple neck
5-string Rogue LX405 Pro (Surprisingly good "no-name" bass)
WT500/800 Highwayman (signature model)
D.N.S 410-8, Eden EX112 x2
Line6 G10s wireless
==
spares:
Eden RS400, GK BK250, BPX115 cab, acoustic B410 cab, Sunn Beta 202 (2x12)