TOPIC:

dirkwright 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).

Ok, let's back up. If you are building a 2 way system, you will be building two cabinets (unless you plan on listening in mono). So that's where the 2 plate amps comment comes from. If you look at the product page you will see that one amp has 2 channels of output in stereo mode or 1 channel in bridged. These are 2 channel amps. www.minidsp.com/products/plate-amplifiers

dirkwright wrote:

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.

Many of the terms they use are also used by sound engineers and recording studios. "2 channel", "stereo", "dual-channel" and even "dual mono" are all terms used to say the same thing. Please don't take this personally but sometimes you have to sit back so you can see the forest for the trees. While I agree that some of the write-ups do not use consistent terms, know that they are all saying the same thing.

dirkwright wrote:

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.

If you look right below in section 2.3.1 you'll see the statement, "SE configuration for stereo mode / 2x 125W Max @ 4Ohms ". Single ended is another technician's term for saying the the outputs of an amplifier are wired direct to the input and not bridged. It's another way of saying "stereo", "2 channel", etc.

dirkwright wrote:

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.

That's not what the manual is saying. It is saying that you get more output from the amp in 4 ohm mode than you do in 8 ohm mode. With 4 ohm drivers, you will get twice the power out of the amp than you would with 8 ohm drivers. 4 ohms = more watts...

The scenario you mentioned is in regards to SPL output of the drivers. True, the higher efficiency driver will create more SPL with the same input power but that's not what the manual is saying. The manual is saying that you draw more power from the amp with lower ohm speakers. It mentions nothing about SPL output of the speakers. Again, please don't take this personally but I believe you are over complicating things.

dirkwright wrote:

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.

I have seen very good quality out of the products I own. MiniDSP as a company is geared toward the DIY and OEM community. They are not geared toward consumers. Some of the terminology they use may be inconsistent at times but the terms are correct when you consider that they are writing toward a varied spectrum of clientele. They are using terms that are used across the recording industry, and OEM providers, not just engineers. There products assume that you have a background in sound engineering, which you do. Just know that sometimes different terms are universal in the trade...

sly wrote:

dirkwright 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).

Ok, let's back up. If you are building a 2 way system, you will be building two cabinets (unless you plan on listening in mono). So that's where the 2 plate amps comment comes from. If you look at the product page you will see that one amp has 2 channels of output in stereo mode or 1 channel in bridged. These are 2 channel amps. www.minidsp.com/products/plate-amplifiers

In the context of audio, a "2 way system" refers to a single loudspeaker with 2 drivers. The term "2 way" does NOT refer to stereo. Those are completely different concepts.

sly wrote:

dirkwright wrote:

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.

If you look right below in section 2.3.1 you'll see the statement, "SE configuration for stereo mode / 2x 125W Max @ 4Ohms ". Single ended is another technician's term for saying the the outputs of an amplifier are wired direct to the input and not bridged. It's another way of saying "stereo", "2 channel", etc.

Not that I know of, ever. Single ended is not the same as stereo or 2 channel. It is a completely different concept. I have never, ever, in all the years that I have studied audio, seen this term used that way.

sly wrote:

dirkwright wrote:

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.

That's not what the manual is saying. It is saying that you get more output from the amp in 4 ohm mode than you do in 8 ohm mode. With 4 ohm drivers, you will get twice the power out of the amp than you would with 8 ohm drivers. 4 ohms = more watts...

The scenario you mentioned is in regards to SPL output of the drivers. True, the higher efficiency driver will create more SPL with the same input power but that's not what the manual is saying. The manual is saying that you draw more power from the amp with lower ohm speakers. It mentions nothing about SPL output of the speakers. Again, please don't take this personally but I believe you are over complicating things.

They are suggesting that it is better to use a 4 ohm driver because you get more power out of the amp and that is plain wrong. It is not "better" to draw more power out of the amp. In fact it is worse because the distortion goes UP as the load impedance goes DOWN.

It also is completely obvious and self evident that cutting the load impedance from 8 ohms to 4 ohms causes the amp to put out double the power, assuming the amp is capable of twice the current output. That is so obvious that it isn't even worth stating if they are trying to talk to professionals, or knowledgeable DIY people.

sly wrote:

dirkwright wrote:

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.

I have seen very good quality out of the products I own. MiniDSP as a company is geared toward the DIY and OEM community. They are not geared toward consumers. Some of the terminology they use may be inconsistent at times but the terms are correct when you consider that they are writing toward a varied spectrum of clientele. They are using terms that are used across the recording industry, and OEM providers, not just engineers. There products assume that you have a background in sound engineering, which you do. Just know that sometimes different terms are universal in the trade...

If they are directing their products at professional people and knowledgeable DIY folks, then I suggest that they get their terminology correct and consistent. I'm not a consumer. I'm actually now considering the idea of producing a loudspeaker product using their technology. I think that would be very unique in the consumer market. Only the professional market has DSP controlled loudspeakers right now, as far as I can tell.

That is good to know that you have good experience with their products. Thanks.

dirkwright wrote:

I understand that there are two ICE amps on each plate, and they can be connected as two separate amps or bridged

No. There's one 2-channel amp module on each plate, not too separate amps.

dirkwright wrote:

They are suggesting that it is better to use a 4 ohm driver because you get more power out of the amp and that is plain wrong. It is not "better" to draw more power out of the amp. In fact it is worse because the distortion goes UP as the load impedance goes DOWN.

It also is completely obvious and self evident that cutting the load impedance from 8 ohms to 4 ohms causes the amp to put out double the power, assuming the amp is capable of twice the current output. That is so obvious that it isn't even worth stating if they are trying to talk to professionals, or knowledgeable DIY people.

First, distortion either way is low enough that it's a non-issue.

Second, most amps don't actually double power with halving of impedance, but the 125asx2 is close.

DS21 wrote:

dirkwright wrote:

They are suggesting that it is better to use a 4 ohm driver because you get more power out of the amp and that is plain wrong. It is not "better" to draw more power out of the amp. In fact it is worse because the distortion goes UP as the load impedance goes DOWN.

It also is completely obvious and self evident that cutting the load impedance from 8 ohms to 4 ohms causes the amp to put out double the power, assuming the amp is capable of twice the current output. That is so obvious that it isn't even worth stating if they are trying to talk to professionals, or knowledgeable DIY people.

First, distortion either way is low enough that it's a non-issue.

Second, most amps don't actually double power with halving of impedance, but the 125asx2 is close.

Well, they use 1% THD as the reference level for maximum power, which in my opinion is high and for those in High End audio, too high. So, basically I take the spec at 3 dB less power as something I would be willing to listen to. It's good that they provide curves in the manual. I like that. Given that these amps are not driving a complex impedance like a crossover, then they should perform pretty well directly driving the loudspeaker driver.

Most of the amps in High End audio do indeed double power with halving of impedance, but if we're talking about ordinary consumer grade amps, then yeah, they usually don't do that.

Please stop with the noxious "High End" audio crap. Very little in the so called high end is engineered worth a damn, unfortunately. And stuff that is is usually commodity parts in fancy casework.

Well, you're entitled to your opinion. I disagree however. A lot of it is very thoroughly engineered. Meridian loudspeakers, for example, have been DSP controlled for a very long time now. They are High End. They are awesome. They are very expensive.

Even further, if I were to produce a DSP controlled loudspeaker using a miniDSP 250 plate amp and just two very good drivers, I would probably have to charge over $3,000 each for them in order to make any kind of profit. That's how expensive this can get very quickly.

dirkwright wrote:

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 would suggest using the plugin, you'll get much further than all this energy spent complaining. You now know that "2-ch" is being used in the plugin instead of "stereo." The use of the term "single-ended" is correct, btw.

Well, I'm upset because I have been recommending miniDSP to everyone I know in audio, talking about innovative, unique and brilliant their products were and then I read deeper into their literature and find all of these silly mistakes! I'm embarrassed for recommending them so highly and that's what upset me.

Look, no offence, but most of these "mistakes" you seem to be just making up. Single-ended, for example - usage is correct. That's also the term B&O uses in the datasheet for the amp module You say the app note implies one amp powers two speakers - I pointed you to the text that specifically says you need two amps. You say that "4 ohm drivers will provide greater power output from the amplifier" is misleading - but it's absolutely true.

Think about it. Why would you need TWO plate amps for a 2-way speaker? It doesn't make sense.

You don't understand my point about the 4 ohm speakers either. They suggest that a 4 ohm speaker is better because it draws more power from the amp. That is NOT true, as I have stated before.

I suppose B&O mean "bridged balanced" mode vs. "single ended" mode for their power amp, but it's not conventional terminology, which makes it confusing.

Based on reading the ICE document in detail, it appears that since this amp module was originally designed for stereo applications, then that terminology was used again in the documents for the plate amp (which is not a stereo amp). This is why it's confusing.

These are technical documents. They are supposed to be technically accurate.

@ Dirk,

That's quite a lot of posts here to read and not 100% sure we want to get into it here..
Some comments (e.g. Single Ended being incorrect) are actually very common for amplifiers and will be an argument to open with all amplifier manufacturers (e.g. see TI website for all their datasheets like here: www.ti.com/product/tas5721?keyMatch=tas5...Search-EN-Everything). So that's an example of maybe why we're not sure where we'd go with this argument. :-)

As usual with all our customers, we're happy to clarify on a misunderstanding for a specific setup you have. If you're doing a 2way active speaker, you indeed need 2 plate amplifiers. One for the left side (Left Low, Left High), one for the right side (Right Low, Right High). The app note is a good start and already countless miniDSP customers did very well setting up the system so I'm sure that with all your knowledge, you'd be fine once you start playing with the software/unit.

Hoping this clarifies.

DevTeam