TOPIC:

Hello, the specifications for the ICEpower125 vs the ICEpwoer250 are confusing. On page 9 of the ICEpower125 data sheet it shows:

Continuous power output without thermal shutdown, BTL mode, 8 ohm load = 200watts

but, for the ICEpower250, page 8 of the data sheet:

Continuous power output without thermal shutdown, BTL mode, 8 ohm load = 180 watts

Why is the ICEpower250 less powerful than the ICEpower125? I don't understand! Please explain!

The continuous/thermal rating is governed by the ability of the amplifier to dissipate heat. In the short term power rating, the 250 is more powerful. Where "short term" is defined in the spec sheet as less than either 50 or 80 seconds. There's some more information in the "Thermal Design" section of the datasheet. However as to why the 250 doesn't have a higher continuous/thermal rating... I don't know. My guess is that they felt the tradeoff (larger/heavier module) not worth it for their intended market.

So, I have an 8 ohm subwoofer rated for rms power handling of 350 watts. I suppose the 250 would put out more intermittent power than the 125, but is it worth an extra 80$ to get the 250 instead of the 125? I'm building these to sell them, since no one seems to want this subwoofer (or the market is just really slow these days). I thought that maybe it would be easier to sell a fully made subwoofer with DSP than just a driver. I'm sure the 125 would probably be loud enough, but would a buyer be impressed with only 200 watts? These are the things I need to consider.... I could also just get a cheaper ordinary plate amp and call it done...

I believe most plate amps / subs with plate amps will be advertised with the short term power rating, not the continuous thermal rating. They just don't have enough heatsinking for thermal rating to equal short term rating. When I look at plate amps on Parts Express, they are 1:3 or 1:8. Stereo Class D amps are 1:8 too I've seen. I don't think I'd be comfortable with 1:8 in a sub but 1:3 is OK. Just a "seat of the pants" feeling

For a subwoofer, I'd be looking at the excursion, not just its power handling.

Whether your target market can handle a DSP subwoofer... you can work that out

This isn't a "market" product. I thought I was clear about that. I just have 2 subwoofers that I don't know what to do with, that's all. They are Dayton Reference 12" subwoofers. No one seems to want to buy them even at $100 each.... sigh. I think I'll just get a BASH 300 watt plate amp and call it done. Hopefully, someone will want to buy a complete subwoofer.

This topic is interesting to me, as I mulled it over for quite a while ... before pulling the trigger on the ICEpower250. I think the short answer is, the issue is thermal limiting in the bigger amp. But it's a little complicated.

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BACKGROUND

I'm a lifelong EE, and a semi-pro musician. I'm using the ICEpower in a subwoofer for a keyboard amp system. I neither represent the opinions or expertise of ICEpower nor miniDSP; in fact, all I have to go on are the specifications of the products, and some experience with high-power audio in a commercial environment. YMMV and all that.

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THE SYSTEM

Calling my speaker a 'subwoofer' is a bit of a stretch. I have a sealed stereo keyboard system with coaxial speakers that is driven by a Crown XTi-1000. As with any sealed system, it's possible to boost the bass to compensate for cabinet roll-off, and I use the Crown's DSP to provide a system that is flat from 50-55Hz to 28kHz, sufficient for most of my gigging needs, especially with room gain. However, the laws of physics have been stretched to the hilt: the smallish box has surprising, accurate bass ... but only until the boost causes the woofer excursion hit Xmax, which is about enough SPL to satisfy 100 people on a dance floor. In 90% of my use, that's enough. In the last 10%, I find myself glaring at band members -- particularly, the bass player -- for 'pushing the envelope,' SPL-wise. I set out to make a box that would fill in the bottom, allowing the main box to crossover at 100-120Hz, where it can easily handle the low-mids to highs in a large venue. For esthetic reasons, the sub box has to be the same size as the main speaker (long story). It's not very big: about 2.5 cu. ft. total, with 2 12" speakers. But Eminence makes a nice 12" bass speaker that works in a 0.8-2.0 cu. ft. enclosure. In principle, the PWR-ICE line is the last piece in the puzzle.

One concern that I have is that the power needs in a band context may exceed the average needs of say, a home audio system. The amount of acoustic power that a bass guitar or organ provides may only amount to 15-20% of a band's SPL, but that output must be maintained throughout a song. So for my purposes, peak output power might not mean quite as much in the big picture. Is the ICEpower a good amp for this need?

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THE CHOICE

The reason for the PWR-ICE125 vs. PWR-ICE250 spec discrepancy is simple: The basic ICEpower amps -- 125ASX2 and 250ASX2 -- are specified that way. Is it a mistake? One might look at it so, but I'd argue it's more a case of two different approaches to amplifier performance.

When I look at the two ICEpower amps from a distance, one thing immediately jumps out: the pass-transistor module on the '250 is much larger than the '125. The capacitors, toroids, and other components look bigger, too. And it might have more power transistors, can't tell for sure from the photos. All of those things generally transfer into more output power -- not just peak power, but long-term output capability. So, why don't the specs declare the '250 as a clear winner?

I think they do -- if one understands where the long-term numbers come from. Let's look at the ones that match up. In SE Mode, the '125 is rated at 105W/chan @ 1% THD @115V, while the '250 is rated at 200W/chan. Similar results are seen in the unbalanced (2 ohm + 8 ohm) configurations; and in BTL Mode at comparable loads. The '250 can provide more clean power than the '125.

So, why doesn't this translate into better continuous numbers? Probably because of thermal limiting -- i.e., the plate-amp design can't pull more than 180-200W out of the transistors without overheating the thermal systen. Note that the '125 is generally rated at 4-ohm loads, but the '250 is pushed back to 8-ohm loads for some of the really high-power tests; probably why the '250 provides numbers for "200W output power" (550sec.) and "1/5 of maximum rated output" (650sec.) -- it can produce a lot of power, just not forever. (I notice a 4-ohm BTL rating of "630W" on the PWR-ICE 250 product brief, which didn't make it into the 250ASX2 specs. Maybe that was the goal, but it gets too hot?)

The thing is: lots of clean power is good for clean bass. If overheating is the only issue, it can be addressed by 1) a bigger heat sink; 2) fan cooling; or 3) big bass ports shuffling a lot of air in and out of the box. I think the '250 is worth the extra $80, because I think the '125's ratings are a bit optimistic for heavy-duty applications. I'm counting on being able to solve the heat problem, if it rears its head. I'll update this forum when I know for sure.

Regards,
-BW

The continuous/thermal rating is with the ICEpower module mounted vertically in free air. So forced air (fan) cooling would no doubt increase the thermal rating a fair bit. It might be interesting to build a separate subenclosure and use a fan to force air up past the module.

The 250 module doesn't have a spec for assymetric loading (not that I can find anyway )

The 630W rating is with an 8 ohm load (not 4), at 10% THD and 240V supply, it's in the 250ASX spec sheet under "General Audio Specifications (BTL-mode)"

I don't really want to deal with a separate amp in this situation. I actually have a second XTi1000, if it comes to that, but the first one + a rack mixer + effects fits in one small (4U) rack. Adding a second power amp either means a second rack, or a heavy 6U version. (I actually have a thought in the back of my head of putting another PWR-ICE in the main cabinet, if it works out well in the bass cab.)

Thanks for pointing out the 630W spec. The 250ASX2 has specs for 2.7/8 ohms and 2/8 ohms on page 8 of the ICEpower (not PWR-ICE) datasheet, which can be directly compared to the '125 datasheet. I know those aren't continuous specs, but I don't think the '250 was intended for bi-amping in a typical main or center speaker, so ICEpower probably didn't bother testing that scenario.

Evaluating the performance of Class D, H, etc. amps is very confusing, IMHO. Even the 'pro' guys like QSC and JBL play the specmanship games with their '1500W amplifiers.' Most of them live without fan cooling, though, so maybe I will be able to as well. Bass porting should help a lot: every pulse of 'sub energy kicks a lot of hot air out of the box, and pulls a bunch of cooler air back in. At least, that's the theory!

drawbars wrote:

I don't really want to deal with a separate amp in this situation.

I meant isolating the plate amp from the rest of the internal volume, so air is forced pver the heatsinks.

You will most likely be fine anyway I look forward to seeing the results, I used to play keyboards a loooong :o time ago.

The 250ASX2 has specs for 2.7/8 ohms and 2/8 ohms on page 8 of the ICEpower (not PWR-ICE) datasheet

Ah, my bad. I was looking at the version 1.1 datasheet which I had on my computer, the site has 1.2 now which does have that spec.

air would be forced over the entire internals of the plate amp if it were in a vented enclosure. i used this idea in the last 18" subwoofer i made. the only problem is that the plate amp is leaky, so the total vent area would be slightly larger than planned.

That's an interesting point (leaks). I was a little disappointed that the plate only has four mounting screws. Has anyone tried adding 2-4 more? A gasket? Silicone RTV?

I suspect the xlr connectors are the primary source of leaks.

I suspect that they are a source of leaks, but I'm not sure about them being the *primary* source. Certainly, an 1/8" thick piece of aluminum can flex, as can the wood of the speaker cabinet. I've been building musician cabs for years, and the rule of thumb for anything that has real bass is a screw every 4-6" around boundaries. At the very least, I plan to replace the screws that come with the PWR-ICE with bolts and T-nuts. But I'm also thinking about adding another pair of bolts at the midway point of the panel.

it's in some of the documentation for the plate amps. yes it is the connectors that are leaky.