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TOPIC: 2 Subwoofer in one Box with PWR ICE 125

2 Subwoofer in one Box with PWR ICE 125 2 years 10 months ago #16489

  • Sabcoll
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i just bought a PWR-ICE 125 because folks at some other place told me it was awesome.
But i think they didnt get my setup right, so i hope you guys can help me:

I'm building a TML right now, here you can see the original one:

So what I'm gonna do is: I will put 2 Subwoofers @ 4Ohms into one box. I want the subwoofers to play exactly the same, since they're in one box!
And my problem is: I don't know how to wire them correctly with the PWR ICE.

If i wire them parallel, then they're gonna be @ 2Ohms and the specs of the PWR ICE say it's not 2 Ohm stable.
If i wire them one after another, they're gonne ba @8 Ohms and it's the same problem.

So what am i gonna do? Just wire one Chassis into "Right" and one Chassis into "Left" ?
This sounds really strange to me ...

i really really hope you can help me!

best regards,
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2 Subwoofer in one Box with PWR ICE 125 2 years 10 months ago #16491

  • Jim the Oldbie
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Hey Sabcoll,

It does sound a bit strange, but it would be OK to connect one amplifier output to each driver. I do this with 3 dual-voice-coil subs; each 4-ohm voice coil is connected to its own channel of an Outlaw Audio 7075 7-channel power amp. However, as you might guess there is one _important_ detail: any amp outputs connected to the same driver (or enclosure, in your case) must have exactly the same signal on them! In my setup this is simple; I just use RCA 'Y' connectors to connect 2 amp inputs together for each driver. There are no input level controls on this amp, and the channel gains are matched very closely, so it works fine with no additional fuss. Unfortunately for your PWR ICE 125 it's more complicated.

As I see it in the user manual, it looks like you'd have to make sure to duplicate every _single adjustment_ (gain, EQ, crossover, comp/limit, etc. etc.) on both Output Channels 1 and 2 in order to make sure the drivers aren't fighting with each other in some way or another. Since there doesn't seem to be any way to link the 2 sets of channel adjustments together, you'll have to do them both separately (and check them carefully) in the plugin software. Kinda clunky, but doable. BUT! There may be a trick you could use to simplify this a bit. Unfortunately there isn't enough info in the user guide to know for sure if this will work. Hopefully DevTeam will read this and let us know. Here's my idea:

When a 2-channel power amplifier is operated in Bridged or BTL mode, the speaker load is connected across the 2 'hot' output terminals. One of the amplifiers then has its input polarity reversed internally. This provides a single output with double the voltage, which would of course produce 4 times the power into a given load impedance (2x for each output). Note that the amplifier is usually _not_ capable of this much of an increase in output power, which is why the minimum load impedance rating for a 2-channel amp operating in bridged mode is typically doubled - to put things back in safe operating range. I don't know why this is not the case in the PWR ICE product specs; they are rated into 4 ohms for both stereo and BTL operation. It may have something to do with the fact that these are digital power amps. (Perhaps DevTeam can shed some light on this.) But as usual, I digress.

My idea assumes that when the PWR ICE is operated in BTL mode, only one of the 2 sets of Output Channel adjustments is active, and the other must be greyed out or something. (It wouldn't make any sense to have one complete set of DSP adjustments on each terminal of a single driver!) Unfortunately, the user guide makes no mention of how this aspect of BTL mode is handled; it only describes how to connect and switch the amplifier sections between Stereo and BTL modes. But IF this is correct, it would eliminate your need to duplicate the adjustments on both channels. THEN, here's what you could do:

1. Connect woofer # 1 to the + and - terminals of amp channel #1.
2. Connect woofer # 2 to the + and - terminals of amp channel #2 WITH ITS POLARITY REVERSED.
3. Set the unit to BTL mode in the plugin.
4. Use the DSP adjustments on whichever single Output Channel remains active in BTL mode.

This scheme should allow you to eliminate the redundant DSP adjustments, while still allowing comfortable power amp operation with a 4 ohm load on each output by using the conventional speaker hookups instead of the BTL wiring. The reversed polarity on one driver would 'undo' the internal polarity flip introduced by the plugin's BTL mode, and make both woofs move in the same direction again.

Last but not least: PLEASE DON'T TRY THIS until someone from DevTeam checks in and says it's OK, OK? :o)

Good luck,

-- Jim

P.S. EDIT: Actually, I just realized that you could also just connect your 2 woofers in series using the BTL wiring (i.e. using both "+" terminals), and probably achieve the same results, power-wise. This would not be unstable; the (total) 8-ohm load across the combined BTL output would appear to the amplifiers the same as a single 4 ohm load connected normally to each individual channel. Just make sure when making the series hookup to connect the "-" terminal of the first driver to the "+" terminal of the second. There still remains of course the question of how the DSP adjustments behave in BTL mode, but you should be able to determine this yourself by firing up the plugin and having a look. It might be helpful if you could let us know how this part works when you have time.
Last Edit: 2 years 10 months ago by Jim the Oldbie.
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2 Subwoofer in one Box with PWR ICE 125 2 years 10 months ago #16494

  • Sabcoll
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Awesome, i never expected such a great answer.
Thanks a lot for your explanations!

I just got one cable from the LFE OUT of my AVR to give signals to the woofer. I will, just like you, just split it up using a Y-cable adapter. Or, using BTL Mode, putting it into one of the analog plugs should suffice. But i got the adapter already and i can do some testing, just in case.

I think it would be perfect to put the speaker in series.
I was unsure if the AMP was able to handle 8 ohms, but thinking about physics back in the days in school i guess it should not be a problem.
With 8 Ohm, the AMP would give 450/2 = 225 Watts to the speakers, right? So 112,5 per Speaker, which would just fit perfectly to my Chassis.

On the applications menu of the site, they wire a subwoofer in bridged mode, so i guess DSP adjustments should just work fine (at least i hope so).

Any other suggestions?
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