# Alpine PDX4.150 Review



## shinjohn (Feb 8, 2006)

First, before I get started, some other reference links to browse if interested in this amplifier:
Car Audio and Electronic's Review of the PDX4.150 
zfactor's pdx review thread 
zfactor's pdx 4.150 review thread 

Instead of regurgitating other's comments, I plan to focus my review on my observations while installing this amp, and then some of my own subjective assessments on performance, etc...

Out-of-the-Box Impressions 
OK, I gotta say it just one more time. This sucker is dang small!!!! It's footprint is about the same size as the H701 processor:









It's got the size and weight of a small two channel tweeter amp, but it truly is a mightly little 4 channel powerhouse! I don't think people will really appreciate the size until they see it in person. It's just compact. IMO, other manufacturers really need to get on this miniaturization bandwagon and I'd like to see more competition for smaller amps, and for prices to accordingly fall. 'nuff said.

Personally, I think this amp has a very high class, clean, and high quality look to it:
(picture linked from Crutchfield)









It looks like it's mostly brushed aluminum/metal, but the reality is almost every cosmetic panel is plastic. Look at those silver hex head caps on the four corners. Looks like they have machining marks on them, right? Nope. injection molded plastic. Alpine did a nice job on the cosmetics, IMO.

Installation
I think the install is pretty straighforward for just about anyone. Ergonomically, I love that all inputs/connections are layed out cleanly on one side of the amp: (picture courtesy of Crutchfield)









and all the adjustments are on the opposing side, behind a removable panel: (image from CAE review)









I like the screw terminals for the power, ground and remote turn on, but notice that the terminals have a 45 degree insertion angle, which is different from most amps. It's not a problem or installation issue though. I also thought the speaker cable connectors were quite innovative: (CAE picture)









They do give the amp a clean look, and keep you from having to contort or work in a small space to connect 8 speaker wires, since you can insert wire while holding the connector in your hand. If you look closely in the picture above, there is a small hole for a _tiny_ hex key on the knurled surfaces of these connectors. That's how you clamp down your wire. These things will hold up to 8 gauge!  Personally though, I would have preferred standard screw terminals for spades/wire. I don't think it will ever be a reliability issue, but you now have to count on the contact spring force of the connector to amp interface for your output stage. I like hard screw clamping force over a contact spring! 

Moving on, you're probably wondering how this thing attaches to its mounting surface, huh? Well the mounting holes are under the decorative screw caps in the corners..... Here's a picture of the amp installed (screwed down), with the corner screw caps removed:









Pretty simple, but with the screw buried inside the amp, I'd advise magnetic tips on your drivers. Basically you are mounting though very deep, blind holes.

So how do you stack things up? If you look at the picture above, there are some *tiny* screws at the bottom of the picture, and some silver painted metal caps on the black floormat. Basically, once you've mounted your amp to it's mounting surface, you install those four caps on top with the tiny little screws. For more detail, look at the owner's manual.

*One important bit of info if you plan to stack things:* Take your drill and drill out the tiny holes in the end caps with a slightly larger (clearance) size. These end caps are cast, and the tolerances are not so great. Those holes were toleranced too small, and as a result of the tight fit, I ended up cross threading a couple of these tiny, tiny screws. I hope someone learns from my experience!!!!!! Do it first before trying to insert the screws!

After that, it's pretty easy to either mount another PDX on top, or make your own custom mount for other gear. You just screw in a standard M4 screw into the center of those caps. Simple. I made a custom mount for an H701, using black acrylic:
















You could easily make mounts out of metal, MDF, whatever. This is the coolest feature of the amps, I think. Stacking. If you have the height, it's an awesome, space saving feature!

OK, this is getting long... subjective comments coming in the next post...


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## zfactor (Oct 19, 2005)

what condition were those small "machined" plastic pieces on top .... 2 out of 4 of my amps brand new out of the box they had some good marks or scratches on them.and according to alpine they are not available yet to buy new ones of.. i wish they were actually metal imo. just curious.. very nice so far and i agree with everything till this point.. lets get some listening in... lol... see if we agree on things or not i know im curious...and yeah i would have never believed how small they really were till i actually saw one if you havent seen them go check one out you will be shocked when you see it physically!!!


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## shinjohn (Feb 8, 2006)

zfactor said:


> what condition were those small "machined" plastic pieces on top .... 2 out of 4 of my amps brand new out of the box they had some good marks or scratches on them.and according to alpine they are not available yet to buy new ones of.. i wish they were actually metal imo. just curious.. very nice so far and i agree with everything till this point.. lets get some listening in... lol... see if we agree on things or not i know im curious...and yeah i would have never believed how small they really were till i actually saw one if you havent seen them go check one out you will be shocked when you see it physically!!!


Those caps were in perfect shape on my unit. I wish they were metal too, they'd be more durable, and also cooler. 

I did some good listening, more thoughts coming very soon!


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## shinjohn (Feb 8, 2006)

OK, review continued....

One last nitpick on the crossover: I'd have expected a x10 switch for frequency on an amp at this pricepoint. Not a big deal though if you've got an H701. 

Subjective Evaluation
So this (quick) eval is based on about 30 minutes of listening time with the system, so take it for what it's worth. Also, since I could not A/B with another amp in the same system, and I changed multiple variables in a short period of time (amp & processor) I can't say definitively that everything I perceived is solely due to the amp.

I have, however, used alot of different car amps in the past, and do fall in the camp of belief that there are some (although often subtle) differences in SQ between amps. I've used a/d/s, Phoenix Gold, Soundstream, McIntosh, Nakamichi, Alpine, and PPI in the past. (mostly old school, though) At home, I use Adcom as my baseline/reference.

To sum things up:
- Based on birthsheets, this amp makes rated power, no problem. Based on sound/SPL, it definitely seemed to make it for me; in other words, I didn't feel it was under what I'd expect for its power rating, in terms of dynamics/SPL.
- I thought the amp was as clear/clean as what I would expect from an Alpine amp. Very clean and respectable performance. I've always thought Alpine amps in general were very good values; great amps for the $$. In this case, this amp is a little more pricey because of the form factor, but worth its price tag. I think most people would not be able to distinguish the SQ with any other Class A/B amp Alpine has produced.
- If I get really nitpicky/anal, my assessment is that it's a fairly smooth sounding amp, and not as "brutally honest" as some other amps I've used, such as my Phoenix Gold. It kinda reminds me of an old a/d/s power plate; very smooth and listenable, with great dynamic range, punch, and depth of staging.
- I didn't notice a lack of low end control in my session. I think this may be for 2 reasons: 
1) the Seas CA18s are 8 ohm drivers, and it seemed like the amp didn't work very hard to get them moving or keep them in control. I found the amp to sound pretty tight, all the way down to the mid bass region (~80 Hz). If you read my other review, I still think my complaints on mid bass were more speaker related than amp related, but could I be wrong? Sure, I leave room for that. The amp sounded pretty effortless to me. But then again, this amp is a 4x150!! It better be effortless on a 2-way front stage!!!
2) I only ran the CA18s full range for all of 5 minutes, before I put the 80 Hz high pass on them. If there are subtleties down below 80 Hz, I didn't have enough time to really critically evaluate that. To me this is a total non-issue based on the fact that most should be high passing around that frequency anyway with their mid basses. I'd hope that people aren't looking to run the PDX4.150 on subs. I'd think there are better (higher) current options.
- Overall, I think it's a very solid performer. I'd highly recommend this amp. If you are looking for an articulate amp that isn't too much of a "zinger" in it's overall presentation, I'd say this is a great option for you. Air on the top, great dynamic range, great package size, and innovative technology. If you are looking for the ultimate in honesty and presentation and SQ, I think you'll have to look beyond this model; I'd probably say a top notch A/B design would probably suit you better. That would, however, leave your wallet lighter, and your trunk with less space too!


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## lv_v (Aug 24, 2005)

Does this amp get hot? I am researching anew system for a new car coming soon and I need to get rid of my US Amps A/B cuz they get too damn hot (for the way I plan on installing the new amps).


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## corrado (Jun 15, 2005)

can ch1/2 and ch3/4 be bridged?

????


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## shinjohn (Feb 8, 2006)

lv_v said:


> Does this amp get hot? I am researching anew system for a new car coming soon and I need to get rid of my US Amps A/B cuz they get too damn hot (for the way I plan on installing the new amps).


Not in my install, but z said his got a bit warm, I believe. If you use it to run components I don't think you could possibly get yourself into thermal issues....



corrado said:


> can ch1/2 and ch3/4 be bridged?
> 
> ????


Absolutely yes.


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## niceguy (Mar 12, 2006)

I was also disappointed to see the amp's xovers could not run higher....for those w/a 2-3way capable HU or external processor it's not an issue...still, a little disappointing.

It and the new Pioneer 'ICE' amp are very nice looking IMO....

Nice review BTW...


Jeremy


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## DS-21 (Apr 16, 2005)

shinjohn said:


> One last nitpick on the crossover: I'd have expected a x10 switch for frequency on an amp at this pricepoint. Not a big deal though if you've got an H701.


Also, the crossover is 2nd order only, right? The 400Hz thing is great from my perspective, but I prefer not to see Whisper smoke so I want a steeper slope. So it looks like a great idea, but perhaps it's not quite a Jello Slash replacement for someone who wants a one-external-box system.


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## shinjohn (Feb 8, 2006)

DS-21 said:


> Also, the crossover is 2nd order only, right? The 400Hz thing is great from my perspective, but I prefer not to see Whisper smoke so I want a steeper slope. So it looks like a great idea, but perhaps it's not quite a Jello Slash replacement for someone who wants a one-external-box system.


Yep. 12 dB/oct.
Whisper smoke... Haha!


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## bernardo (Jan 31, 2008)

guys i have the PDX-4.100 and since i bridge it to 200x2 it has a wierd noise when i turn on the HU, then when you set the volume up to 12 or more, the noise completely disappear.

also when you leave the volume at 12 or more, and turn off the HU, when you turn it on again the noise stays for a few seconds until the music starts, and then disappears.

the bridge is positive on channel 1 and 3, and negatives on channels 2 and 4

i already check the battery, the hu, the speakers, the conecctions the rcas, and everything..

what could it be?


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## placenta (Feb 2, 2008)

great review, thanks. my purchase decisions now become even harder.. size has always been an important issue to me. (NO silly comments!!)


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## placenta (Feb 2, 2008)

I'm sure this has been posted before, but heres another review:

http://www.caraudiomag.com/0607_cae_alpine_pdx_4150_amplifier/index.html


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## placenta (Feb 2, 2008)

Anyone know when the 5 channel is coming out? I am considering it vs a 2.150 and a 1.600.


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## supra400hptt (Aug 11, 2005)

When I called Alpine the guy said March. I got a crutchfield catalog yesterday and they have it listed.


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## placenta (Feb 2, 2008)

supra400hptt said:


> When I called Alpine the guy said March. I got a crutchfield catalog yesterday and they have it listed.


ya its online too, but out of stock. ah i'll prob go with a 2.150 for my front anyway.. I wouldnt use active in front and rear doors would be a waste.


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## tyroneshoes (Mar 21, 2006)

bernardo said:


> guys i have the PDX-4.100 and since i bridge it to 200x2 it has a wierd noise when i turn on the HU, then when you set the volume up to 12 or more, the noise completely disappear.
> 
> also when you leave the volume at 12 or more, and turn off the HU, when you turn it on again the noise stays for a few seconds until the music starts, and then disappears.
> 
> ...


Are you using passive crossovers (component set)?


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## bernardo (Jan 31, 2008)

tyroneshoes said:


> Are you using passive crossovers (component set)?


yes i do, i have a set of polks DB6500


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## ms6625 (Dec 29, 2007)

I have the DRZ as my HU and the pdx 4.100 for my tweets and mids and a pdx 1.600 for my sub. I'm running them active from my DRZ. My question is, will the crossovers of the pdx amp affect the outcome of the DRX x-overs?
Will turning off the filter switch on the pdx amp also turn off the crossover?


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## OgreDave (Jul 13, 2005)

Yes your xovers are currently combined. If you want it to be accurate, basically set the PDX ones way way way out of bounds, or turn to full pass through.


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## bernardo (Jan 31, 2008)

tyroneshoes said:


> Are you using passive crossovers (component set)?


 any ideas?

im really worried


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