TOPIC: PWR-ICE for 2 way speaker app note is confusing!

www.minidsp.com/applications/plate-ampli...ice-for-2way-speaker

this application note is confusing. How many amps are in each PWR-ICE? I thought there were only two, one for the tweeter and one for the woofer. The app note suggests that ONE PWR-ICE will power TWO speakers. Sections 4 and 5 of the note suggest that you are supposed to put the amps in "stereo" mode, which would be for two separate speakers. How can you have an active crossover for a 2 way loudspeaker with only ONE amp per channel? This doesn't make sense. See the attached figure. Each driver needs it's own amplifier in order for this to work, or you are doing something really strange that I don't understand. Please explain.

Not only that, but the above app note directs me to this one:
www.minidsp.com/applications/digital-cro...s/stereo-2-way-xover

which doesn't even list the PWR-ICE products or their software interface which is apparently different (since it is a 1x2 DSP). Please explain.

Also, the attached image, as found in the user's manual for the PWR-ICE 125, is confusing. In the lower right corner of the image there's a block that says "Left" with an arrow that points to "250ASX2". What is that?! Where is that? What connection is this on the outside of the amp? Your other diagrams show multiple PWR-ICE 125 plate amps daisy chained together via AES/EBU cables. So, what exactly is this "Left" thing connected to, and how?

Likewise, in the lower right corner is a box that says "Right" with an arrow that points to the two modes the amps can use, SE or BTL. What or where does this "Right" connect up to?

Without commenting directly about the manuals, here's the general idea on these amps: Each plate amp has two output channels so it can power a 2-way speaker. It could also power two speakers if they are single drivers or have passive crossovers, but it sounds like that's not your plan. If you have a pair of 2-way speakers then each speaker gets its own plate amp, and they are daisy chained via the AES/EBU cable. That way only one speaker needs to connect to the source. One plate amp is designated "left" and the other "right". You won't use the "stereo" setting in a 2-way speaker, when both amp modules in one plate amp are going to the same speaker (for high & low frequency drivers).

There are only two settings for the amps: "Stereo" or BTL. That is wrong. It should be "biamp" or "bridged". It is very confusing. The manual also shows one amp on the plate amp labeled as "left" and the other is labeled "right". That is also wrong and confusing.

My reply above is wrong, the "stereo" setting means two separate outputs, vs. bridged. Maybe there's a better way to put that, like "dual output" because "stereo" isn't exactly what you're doing within a 2-way speaker. But once you get what the labels mean it makes sense right?

Who ever wrote the software and the manual doesn't seem to understand audio very well, or maybe it's a translation issue, I don't know. I understand that there are two ICE amps on each plate, and they can be connected as two separate amps or bridged. That's pretty clear from some of the diagrams in the manual. There are so many other confusing parts of the manual though that I have doubts. It will be really weird and confusing in my mind when I'm in the software to have to set the amp to "stereo" mode when I really mean "bi amp" mode, in addition to the crazy idea that one amp is "left" and the other is "right". It makes no sense at all. They should have labeled them just as "amp 1" and "amp 2" or something like that.

Also, I have a real question about this amp. In the section 2.3.6 Amplifier Jumper Pads, they say that they added an analog pad, with two jumpers that can be open or closed. Since these are analog pads, do they still function if I am using the digital input? It doesn't explain that. Since it says it's an "analog" pad I assumed it only applies to the analog inputs, or what? Also, does the "master volume" control work when the digital input is used?

Even further, in the software interface for the DSP mode, section 3.1.1 as shown in the attached picture, it's not obvious that "channel mode" refers to the INPUT for the DSP processor. It took me a really long time to figure that out, even after reading the text.

Dirk, I have one of these amps and use it on a subwoofer in bridged mode, but haven't used it in a 2-way speaker, so bear with me if my answers aren't on the money. As to the jumper in 2.3.6, the manual seems to say this only affects the analog input. It's not a necessary feature because you can adjust channel levels in the DSP, plus you may have roughly the same sensitivity for high and low frequency drivers. So if this doesn't solve problems, ignore the jumper and leave in the default position.

"Master volume" is a knob on the amp, not a software setting, and it applies regardless of the input used. However, this is not particularly convenient for a 2.1 setup with multiple plate amps, because you'd have to adjust three different knobs, and in unison. So this might be better labeled as a gain control knob.

"Channel mode" refers to the input, yes. Use "mixed L+R" for a mono subwoofer, otherwise choose L or R for main speakers.

Another way to do a 2.1 system with plate amps is to use the passive version of the amp (PWR-ICE125WD) in combination with a DSP unit that has analog outputs. The 125WD has no DSP and only analog RCA inputs but the same amps as the PWR-ICE125 (note also that it's a different size so you need to choose before making cabinets). This system could be controlled with either the MiniDSP 4x10 Hd or the nanoAVR-HDA. Both of those have analog RCA outputs, and you'd have a bunch of long RCA cables. Advantage to this setup is one interface for the system, room to expand (could add more monitors or go to 3-way). Also you get a true master volume control for the system. I have ordered a nanoAVR but not received it just yet. The software interface is quite different from the 4x10 Hd, and it has only HDMI inputs, so you may need a preamp or something like the Oppo BDP-103 to sort out multiple inputs. Potentially big perk for the nanoAVR is you can control volume, source and preset selection using a smartphone app. There's also an app for the Oppo that controls media streaming, media library and various other things (have considered getting one of these).

dirkwright wrote:
Right at the beginning, the app note says:

"What you will need

Two ICE-PWR125 plate amps OR two PWR-ICE250"

The app note seems to be a little out of date, the modes in the current version are named "2-ch" and "BTL".

john.reekie wrote:
OK, I see that. Now it's even MORE confusing. EACH ICR-PWR plate amp has TWO power amps in it. For use in a two way loudspeaker, one amp drives each driver individually, so why in the world would I need TWO plate amps for ONE loudspeaker? That app note is supposed to be for ONE loudspeaker with TWO drivers (a woofer and a tweeter).

I should not have to figure out what they are trying to say. Instruction manuals and app notes are technical documents that are supposed to clearly explain everything. The documentation that I have seen is sometimes very confusing and technically incorrect so I have to figure out what they are trying to say on my own and that is very frustrating.

There is even more stuff that is confusing about the user manual for the ICE-PWR 125. Maybe people just gloss over these mistakes but trying to follow instructions from something that makes so many mistakes is also very frustrating. For example, on page 8, at the top, where it says "The PWR-DSP125 amplifier can operate in Single Ended (SE) or Bridge Tied Load (BTL) mode" - the term "single ended" is incorrect and is not consistent with the term "stereo" used in other parts of the document. A Single ended amplifier is something entirely different from the ICE power amp.

Back to the app note about using the PWR-ICE for a two way loudspeaker, they state: "If you are starting from scratch, you will need to select the drivers for your speakers. You can use drivers rated at 4 ohms or 8 ohms — 4 ohm drivers will provide greater power output from the amplifier but for most applications it's not critical." - which is misleading. A 4 ohm driver rated at 90dB/W/m will put out exactly the same sound pressure level as an 8 ohm driver rated at 93dB/W/m - (3 dB higher) when the amp is driven at the same input voltage. These kinds of misleading statements make me nervous about using the products from miniDSP and also make me wonder about the skill level of the people who made this equipment. I don't know of anyone else making DSP controlled plate amps so that's incredibly great that they came up with this idea. I can only hope that what I get in the mail will be high quality.

thomasjefferson wrote:
I need to pad the tweeter down a lot so yeah, I'll have to do this in software. Thanks.

I've attached a drawing of my plan. The OpenDRC-DI provides EQ for the room, and each plate amp provides an active crossover for each loudspeaker. So, I'm going to have to set up 4 separate DSP chips with filters but the result should be the ultimate in flexibility.

Sorry but you're not making a lot of sense. You seem to be on some sort of rampage.

Is there something in particular that are you are not understanding about how to use the amps and plugin at this point in time? Perhaps if you could say what you don't understand, some of us who already have the amps might be able to help you.

I thought I was clear. There are a lot of confusing statements in the app note as well as in the user manual for the PWR-ICE125. I'm an engineer so I expect clear and consistent instructions and I don't see them with these documents. I'm not on a rampage. I'm trying to understand what they are saying, and I want to make sure I don't misunderstand either.

I'm an engineer too... have you installed the plugin and played around with it?

No, not yet. I'm just preparing right now by studying their literature and learning as much as I can about their system. I design analog audio gear as a part time small business, so I have a lot of experience with analog audio. Specific words mean specific things to me so when they aren't used in the correct way I get confused. I'm sure the folks at miniDSP are sincere and earnest about their products but I'm worried that I may have missed something because of the confusing literature.

I really believe this is the way to go, with DSP plate amps and DSP room correction. I'm building an all digital system, which is a first for me, so I want to make sure I get everything correct. Making an all digital system solves so many very important problems that I can't see any other way of doing it any more.