PDX4.150 Class D Midbass against Soundstream Class A/B Midbass

[Polkemon]

I know there are some that think all quality amps of the same power are equall but I have a 2000 Mustang with Alpine SWX-17REF Front Stage Powered by Alpine PDX4.150, Alpine 9886 Head Unit, 2- 10" Alpine Type R's powered by an Alpine PDX1000.1.

I decided to Swap out the PDX4.150 for the Soundstream VGA400.2 that has the same rated power as the PDX4.150 and I must say my Midbass came alive. I read about the lack of midbass in Car Audio with the PDX amps and they were not kidding because on Full Range Mode on the PDX it put out very little but clean Midbass but with the Soundstream in Full Range I had a ton of clean Midbass and AWESOME sound clarity coming from the front.

I am not saying that amps are the reason for Midbass but it sure seemed like it when changing the amp out. The Soundstream is a Class A/B versus a Class D Amp.

Thought some would find this interesting!

Note: I have no EQ in the car as of yet.

[killerb]

it probably has something to do with the damping factor of the amps. class d amps have lower damping factors. i dont know if that is the reason, but it could be.

[MacLeod]

Rated power dont mean squat. In home audio, ratings are drastically overrated. In car audio however, theyre usually underrated. The Alpine amps, from what Ive seen in tests, meet their rated power but dont exceed it by much. Thats still cool - as long as it does what it claims to do. Soundstream however is a little more underrated so a 150 watt amp from them Id wager would do more like 175 or so. Thats not a ton more power but it is more power.

Also, if you look at the frequency response graphs from both amps, I will wager theyre ruler flat from 20-20KHz as 99.9% of all the amps Ive EVER seen tested in magazines are. This being the case, how could one amp have better midbass if it puts out midbass frequencies at the same level.

One last thing, you went into this with a predisposition that the Alpines were weak on midbass - so naturally when you swap them out, you hear a difference. If you were to BLINDLY compare them next to each other at the same level, you would NOT hear a difference. Nobody ever has in ANY of the millions of double blind tests done over the last 3 decades.

[Polkemon]

The Soundstream Amps are 168 on the Birth Sheet and The Alpine I think is the same or very close, as for the going in to this thinking that the Alpine Amps are weak on midbass is true (Reading Car Audio Test) but the difference was very noticeable with both amps running Full range. The doors went from not rattling much to rattling quit a bit more.

The frequency response graphs for the Soundstream are unable to be found since they are 5 year old amps.

Mac, I am not saying your wrong by no mean. I just cant figure out why such a big increase in the midbass plus backing that up with the report done on the PDX in Car Audio. Now as for an amp being warmer sounding I do not find true being that I have had Mcintosh, JL Audio and so on. The Mcintosh has been my favorite amp but with there size I am limited otherwise they would be in all my cars. I think it is the looks that get me and I guess I would have to say that the sound that come from them is outstanding but put them next to the PDX, JL, Polk and I would say blind folded I could not say what one would sound better! The only amp I have had that I was not thrilled with was the POLK C400.4 Amp. I had replaced a JL Slash Amp with it and after a few days went back to the JL amp do to it just not sounding as good to me or a few other that heared it when I changed it out. It might of had problem but didnt seem to.

[MacLeod]

Well then you should definitely take Richard Clark's amps challenge.

Take your amps up there and you could easily win $10,000.

Both amps will be hooked up and level matched. You will listen to some music, you control the volume and the switching between the amps. All you have to do is pick out which amp is which and youll win. Should be easy with one amp being so flat in midbass and the other so rich. Or you could take the harsh Polk with you which should be easy to distinguish between it and the much smoother JL. You could be the first person in history to do it. But I want a 10% commission for sending you up there. That Panasonic plasma TV I want is on sale right now for $1000. :D

http://www.talkaudio.co.uk/vbb/showt...threadid=18815

[eloplayspolo]

panasonic plasma.... stick to car audio, go get a sharp sony or hitachi..... panasonic... come on.

[Polkemon]

I just bought a Sony 52" XBR5 TV. It has a much warmer sound! Damn MAC did I hit a soft spot in you heart???? I do not have time for no AMP Challange with running my Landscaping business working 75 hours a week. All I was stating was it seemed to have a bit more Midbass and I would be happy to meet anyone in the area an switch them out and if they could not hear it then they must be deaf. Maybe one of the amps has a problem causing it. The Polk amp might of had a problem as I stated in the post. JL was a good sounding amp but YES it sounded better than the POLK if nothing was wrong with the POLK. MAC get some rest because you are getting to up tight over a simple post. Yes, If I use the two amps I have and set them both on Full Range with Gains mattached I could easily pick them out. Maybe the gains are off a bit causing one amp to be driving the speakers a bit harder. Not sure!

[MacLeod]

This is nothing. You wanna see me get worked up start talking about how different brands of RCA's sound different! :p :D

[1996blackmax]

The warmer sound that some people talk about usually comes from an amp that does not have a flat frequency response.

If you are getting more midbass it might be that that either the Alpine has a dip in that area of or maybe the Soundstream has a bump in it.

I do remember when that PDX amp was tested, the reviewer mentioned that it was lacking somewhat in the lower range......I do not really know what he meant by that...heck maybe I knew when I read it and don't remember... I myself would not have an issue running one of the newer Alpine amps. Lots of power in a very small footprint ftw. I like small amplifier that pack a punch...mine are a tad under 7" wide.

[Polkemon]

LOL! Hey now MAC, I just posted about the RCA thing because of the finding from Focal website. I think the Blue Lights on the Mcintosh help with the warm sound that comes from them but for some reason the fans on the amp dont cool the sound down. STRANGE!!! I am far from a Car Audio Pro that is why I have so many questions but really love doing car audio and have learned alot from most of the posters on here. I am the Owner of Landscaping Company that builds Water Falls and Ponds and Full Property Maintenance not a Pro Car Audio Shop.

[1996blackmax]

A good family friend of ours is a landscape designer. She does some very nice work.

[killerb]

my brother is a landscaper and does great work, just not when i hire him! ha! ha!

[killerb]

The warmer sound that some people talk about usually comes from an amp that does not have a flat frequency response.

If you are getting more midbass it might be that that either the Alpine has a dip in that area of or maybe the Soundstream has a bump in it.

I do remember when that PDX amp was tested, the reviewer mentioned that it was lacking somewhat in the lower range......I do not really know what he meant by that...heck maybe I knew when I read it and don't remember... I myself would not have an issue running one of the newer Alpine amps. Lots of power in a very small footprint ftw. I like small amplifier that pack a punch...mine are a tad under 7" wide.

some say the warm sound comes from a low output impedances. Bob Carver used a 1 ohm resister on the outputs to mimic the sound of some very high end amps with great success. that might affect the freq. response, who knows.

[killerb]

blackmaxx you were right, read below. tube amps with there warm sound have freq. irregularities.

Postscript: The Sunfire has a unique feature I didn't mention earlier because I don't consider it to be serious. It has a second set of output terminals labeled Current Source, which is a euphemism for the insertion of a 1 ohm resistor in series. Biwiring with the tweeter attached to these will attenuate the tweeter output, which in many speakers will be all to the good, but in others not. Otherwise, the Current Source terminals will induce all the response irregularities of a 1 ohm output impedance tube amplifier, turning the elegantly neutral Sunfire into a coloration machine. (You can form your own opinion of reviewers who have preferred this degradation of performance without even a careful description of its cause.) Maybe Carver wanted people to hear for themselves how important it is for an amplifier to have low output impedance. (If so, the trick seems to have backfired a bit.) Little jokes are the privilege of genius: Beethoven liked them, Ives is full of them. Theirs, and Carver's, are all right with me. But a perceptive listener won't use the Current Source taps for long, unless, strictly by chance, the associated intrinsic inaccuracies compensate in part for those of your speakers.

[Kinetic]

i have an Alpine 9887 and the PDX4.100 with my polk front stage and running now just 2 channels.

i used to have the amp bridged, and may gains on a 1/4 (100W)

now i have them on just 2 channels and the gains at 1/2 (100W)

i hear better performance on the lows having the gains at 1/2, but im not an expert on car audio, actually im a begginer.

as far as the lack of mid bass, i dont really hear it, but i have a parametric EQ, and maybe the EQ is solving that problem.

but try your pdx amp on a 1/2 of gain (if you have 4V), maybe it works different for you

[MacLeod]

They dont have a frequency response graph for that test report for the PDX but the article does state:

Alpine conservatively states the frequency response to be 20Hz to 20kHz, but I measured it to be 5Hz to 32kHz at -1dB,

That means there was NO MORE THAN 1 db difference from 5-32 KHz. Thats not only virtually ruler flat but a difference of 1 db is virtually inaudible.. So if its ruler flat from 5-35 KHz how can it be weak in midbass? I guarantee you that the Soundstream amp is ruler flat from 20-20KHz as well so both amps having the same output at the same frequencies CANT have different outputs.

Ill even go ya one better and say youre right, the Alpine has a dip in the midbass and the Soundstream has a bump - why would you want either of these amps??? An amplifier's ONLY job is to amplify the source signal as transparently as possible. Why on God's green earth would you want to add boost here and cut there? Thats what EQ's are for. a 3 db bump at 100 Hz might sound good in an Accord with 6.5" drivers but not so good in a Tacoma with 6x9's.

Some tube amps DO have a warmer sound but this isnt due to any magic. Its actually a response error that causes the frequency response to roll off at the high end. The same effect can be created with an EQ.

[1996blackmax]

Just wondering here...... if the amp is pushed will the response stay the same? I would guess that a quality amplifier would.


Bottom line is if that you like the way it sound with the other amp, stick to what works for you.

[MacLeod]

Just wondering here...... if the amp is pushed will the response stay the same? I would guess that a quality amplifier would.

Good question. I honestly dont know but if I were to hazard a guess I would say that the response wouldnt change much when pushed. I doubt it would be much more than .5 db or so which is essentially inaudible plus I would think that once pushed hard enough, the audible distortion would drown out any changes in frequency response anyway.

I believe the mags test the amps at 1% THD which is pretty stout so Id feel pretty safe in saying that the test results you read in the magazines are definitely what youd get in the real world.

Also, this would come more under the heading of power rather than tonal characteristics. You can take a 50 watt amp and stack it up against a 200 watt amp and youll hear all kinds of differences. Nobodys saying smaller amps dont sound different than bigger amps. All Im disputing is tonal characteristics like tighter midbass or cleaner highs. These are characteristics of speakers - not amps.

[Polkemon]

All I was stating in this thread was about the midbass difference other than that both amp sound outstanding with the clarity. I did not act like I new what the problem was just posted it to see what thoughts could be.

MAC does the H701 up the Volts from the preamp? The W205 is 2.5V preouts and from what it sounds like the H701 brings it to a 4V. I can defeat everything but the Crossover Correct? I want to start off with getting the Crossover in the unit set then work on the EQing. I know it says that with each feature expect the Crossover you can hold the button down and it turns it off now is the main defeat button on the controler do the same but turns all off but the Crossover?

To the Members that mentioned the Landscaping. I Love my line off work and the time off cant be beat with crews working ran by my my three brothers working for me as crew foreman I can trust that accounts and money is handled properly. I also added house painting on as of last year and we have 5 homes lined up within the last 4 weeks WOW! I have one Paint Crew Now and another being set-up that will handle all the painting jobs. I stay busy but it beats working at Fruit of the Loom as I did for 6 years untill everything went overseas and all I had to turn to was my wife saying what about statring a Lawn Care Company. 8 years later and a total of 5 crew with 14 Employes I could not be any happier. I do get more headaches but everything comes at a price.

[1996blackmax]

Here a post I just came across at DIYMA about the 4.150 .....

This was from post #2 by FoxPro5:

"Love the 1.600. Does what it's supposed to quite nicely and you cannot beat the footprint.

Used the 4.150 on my midrange (SS Revs) and tweeters (Lotus RT7f). Amp was unimpressive and absolutely nothing special. I hate to use "SQ" when it comes to amps, but if I was forced to...I'd give it a straight "C."

All other variables aside, I level matched the 4.150 to a pair of LP's which do 1/3 the rated power and it was no contest as to which amp was more capable. IMO it comes down to the design (power supply maybe????). Seems Alpine tried to get too "cute" with these things.

Just my extremely critical feedback, so take it for what it's worth and no more. "




Link

http://www.diymobileaudio.com/forum/...ad.php?t=34317

[Polkemon]

WOW! Now I ask myself is the PDX a good amp or not?????

[MacLeod]

MAC does the H701 up the Volts from the preamp? The W205 is 2.5V preouts and from what it sounds like the H701 brings it to a 4V. I can defeat everything but the Crossover Correct? I want to start off with getting the Crossover in the unit set then work on the EQing. I know it says that with each feature expect the Crossover you can hold the button down and it turns it off now is the main defeat button on the controler do the same but turns all off but the Crossover?

When you flip the switch on the bottom of the HU, all the EQ's and crossovers are disabled. The only thing that will work is treble and fader. As for output voltage, its 4 volts out to your amp.

One last thing on the PDX amps - the highest score at MECA world finals in 2006 was done with Alpine PDX amps. He didnt seem to notice any weak midbass or poor SQ.

[Polkemon]

Thanks MAC! I do love the SQ of the PDX amp and will continue to run them in my setup. As for the H701 I want to use the Crossover on the H701 but not use any of the other features of the H701 until I here all off then adjust from there so I would need the switches on on the Head Unit so that I can use the Crossover. Right??

Thanks Again!
Donny

[MacLeod]

No. You wont use the HU at all - youll use the 701's remote control unit.

You dont turn off the EQ, just set everything to flat (0 db) and its essentially off. Then set the time correction to 0 ms on all channels and its off. Then make sure media expander and all the crap is off as well. Then youre set.

[Polkemon]

One more question to clarify. I do need to flip the switches on the bottom of the unit telling it I am running the H701 even though I am using the controler. Right??? The reason I am asking is becasue if I am not using the controls on the 205 then do I still nedd the switches fliped over to processor or will the 701 not work if the switches are fliped to normal?

Thanks

[MacLeod]

If youre using a 701, yes, flip the switch over to EQ.

[Thom]

A more likely cause of the difference in midbass you heard is that the crossovers aren't set exactly the same between the two amps. Unless you're running both amps full range, which is unlikely. If the Alpine's high- pass was set to an even slightly higher frequency that would make a difference. Even if the crossovers "look" like they're at the same frequency, they may be different designs or slopes.

The C400.4 amp you had issues with- any chance you had the "Polk EQ" button pushed in?

[Thom]

...and if you have a W205, why run the controller for the 701? The W205 makes it super easy to control the 701.

[1996blackmax]

A more likely cause of the difference in midbass you heard is that the crossovers aren't set exactly the same between the two amps. Unless you're running both amps full range, which is unlikely. If the Alpine's high- pass was set to an even slightly higher frequency that would make a difference. Even if the crossovers "look" like they're at the same frequency, they may be different designs or slopes.

Good point Thom....

[Kinetic]

Good point Thom....

i was playing with my settings and recently found good sound overlaping the crossovers, so i put the HPF at 63 and the LPF at 80 with 18 slopes and 24 slopes

try that

i also have pdx but i use the crossover on my HU alpine 9887