Bass problem eludes CAR TOYS installers

[Mark97213]

Gary, you HAVE to be correct! Thank you so very much for your knowledge on this. When we first selected the system, I was pretty Leary of their suggestion of throwing a 3 ohm in the box but I was limited on box depth and it was the only option at the time. I think another trip to Car Toys is out of the question at this point as I fear they are simply in disbelief at any issue even existing. Without some outside influence such as that from an Alpine rep I think my complaint will fall of def ears.

 

[garychoffmann 10+ year member]

I agree with you on this one except for the pdx. I had some old titanium eclipse that were supposed to be d4's but the coils commonly were 2.7 to 3.2 on those. I had a resting load of 2.8, could not figure out why I couldn't get it to play well on a pdx. As it was described to me the pdx's power management processor takes input voltage, load, output, temp, signal and a few other things into consideration. It's initial response was to cut 6db, then .1 db until the problem was stabilized, then it would start to add power and then sensing a problem it would cut back a final 3db until it came back up and it would start the process over. I fixed it by dropping my subs down to around 1.4-1.5 can't remember exactly.... and it played fine. I have no real idea why it did this, just after many talks with an alpine developer I dropped my ohm load further and it stabilized. If ohm load doesn't effect his amps performance I'd have to say its the power management processor going goofy. Just my 2 cents cuz i've been there.

 

[bbeljefe]

I agree with you on this one except for the pdx. I had some old titanium eclipse that were supposed to be d4's but the coils commonly were 2.7 to 3.2 on those. I had a resting load of 2.8, could not figure out why I couldn't get it to play well on a pdx. As it was described to me the pdx's power management processor takes input voltage, load, output, temp, signal and a few other things into consideration. It's initial response was to cut 6db, then .1 db until the problem was stabilized, then it would start to add power and then sensing a problem it would cut back a final 3db until it came back up and it would start the process over. I fixed it by dropping my subs down to around 1.4-1.5 can't remember exactly.... and it played fine. I have no real idea why it did this, just after many talks with an alpine developer I dropped my ohm load further and it stabilized. If ohm load doesn't effect his amps performance I'd have to say its the power management processor going goofy. Just my 2 cents cuz i've been there.

I didn't say ohm load doesn't affect amplifier performance. The fact that it does affect performance is the very reason why most people want an amp that can deal with a near dead short. But impedance is a lot more complicated than just a reading on a meter and box rise, whatever that actually means*, has been around for as long as loudspeakers and the amps that drive them have existed.

* I know what the term means, but frankly, all drivers present a rise in impedance to the amplifier driving them, even in free air. I suspect, however, that box rise is another myth that goes hand in hand with amp clamping, which is basically using a DC power formula on AC power. It isn't accurate and it doesn't tell you what the amp is doing or what impedance it's seeing, because its the wrong formula, lol.

And I'm saying you didn't have the problem you did. But let's face it, if Alpine built an amp that can't handle a load that's between 2 and 4 ohms, you weren't talking to an engineer... you were talking to a PR person... aka, spin doctor.

 

[Side Show 10+ year member]

spin docker = bullpoo artist

 

[garychoffmann 10+ year member]

Lol, I hear ya and I had to track the engineer down on one of the forums. I asked around enough to find him. I doubt our knowledges are equal so no need to fro back and forth. I retain information and I know enough to do alright and trouble shoot. I don't bother calling places and being told about how the unicorns and rainbows will fix my problems lol. I found the whole ordeal with my pdx frustrating and downright silly because I shared the same view as it should be able to do any load in its range. As explained to me, it does have a processor, the fault with a processor is its inputs and outputs are user(alpine) defined. So it acted a little goofy. It really is beyond me at that point. I've seen the knowledge you spout so I know better than to try and argue a point I can't back up. I can just try and help with the stuff i've dealt with.

 

[Side Show 10+ year member]

^^ well said.... hope captain alpine can shed some light for us lol

 

[ahardy17 10+ year member]

I'm on my phone so I can't type a whole lot. But the pdx is a constant power amplifier. It is rated at 2 and 4 ohms. A 3 ohm load is skirting its high power vs high current switch over point. The amp draws back power as it switches from high power to high current. The amp is getting confused and that is why you are getting a low power output and then a surge before it settles back down and then the cycle continues. The problem is what is called box rise. Your ohm load changes as music plays. I forget which forum an alpine engineer frequents, but you could probably hunt him down

since you seem to know a few things about PDX amps, maybe you can help me. I blew my sub a few months ago and have been running 4 channels ever since. In that time I have developed a dreadful pop not only at turn-on but when I change songs/stations, etc. Does not having anything for the 5th channel to output to affect the outputs in a way that would induce pop, orr is something broken inside the amp? It pops with or without RCA's connected. BTW I'm running Infinity Kappa speakers which are 2.5 ohms if it matters

 

[hispls 5,000+ posts]

Go to car toys in the morning. Ask them to throw a prefab in the seat that rests at 2 or 4 ohms and play it full tilt. If it doesn't have issues, you know your problem 

---------- Post added at 10:53 PM ---------- Previous post was at 10:53 PM ----------

 

Beat me to it.

Implying that ANY woofer won't vary between DCR and up to 20-40 ohms or more....

That sounds like a cold solder joint and it's not at all uncommon for the RCA assemblies. However, when they have a cold joint, they make gawd awful screeches, pops or hums. I would think it's the power inputs or some other part of the power circuit. And if they did in fact replace the amplifier with another one they had on hand, both could have come from a batch of amps that suffered a manufacturing malfunction on the assembly line or, they could have gotten a bad batch of caps, op amps, et al.
I would be more inclined to try a different brand amplifier than a different driver. All amplifiers are designed to operate properly with a constantly changing impedance, because all loudspeakers are variable impedance devices.

This or some other internal fault in the amp is my best guess. You could rule out the source unit by using the RCA's from the front or rears (known working I'd assume) into the sub amp for a quick test.

 

[hispls 5,000+ posts]

using a DC power formula on AC power. It isn't accurate and it doesn't tell you what the amp is doing or what impedance it's seeing, because its the wrong formula, lol.

Ohm's law doesn't work with AC? That's news to me, please elaborate.

 

[bbeljefe]

Ohm's law doesn't work with AC? That's news to me, please elaborate.

Yes, Ohm's law does work for AC power but it is not the same formula. Voltage and current on an AC wave form are not in phase with one another and that phase difference must be calculated along with the power formula. When you apply Ohm's law to AC signals without accounting for the power factor (phase difference between voltage and current) you are calculating volt amps (VA), not watts.

To properly clamp test an amplifier you need a scope with two inputs so that you can measure both wave forms. When you don't do that, your calculations can be 50% off or more.

 

[hispls 5,000+ posts]

Yes, Ohm's law does work for AC power but it is not the same formula. Voltage and current on an AC wave form are not in phase with one another and that phase difference must be calculated along with the power formula. When you apply Ohm's law to AC signals without accounting for the power factor (phase difference between voltage and current) you are calculating volt amps (VA), not watts.
To properly clamp test an amplifier you need a scope with two inputs so that you can measure both wave forms. When you don't do that, your calculations can be 50% off or more.

http://hyperphysics.phy-astr.gsu.edu/hbase/electric/powerac.html

Which begs the question, do manufacturers use an average or instantaneous power when making "ratings" on amplifiers? Good catch, hadn't considered phase angle.

 

[BrownVanMan 10+ year member]

Maybe the amp is switching from high power to current mode due to the odd imp?

 

[bbeljefe]

Power in AC Circuits
Which begs the question, do manufacturers use an average or instantaneous power when making "ratings" on amplifiers? Good catch, hadn't considered phase angle.

My guess would be... depends on their level of integrity.

 

[hispls 5,000+ posts]

My guess would be... depends on their level of integrity.

My guess is instantaneous power only. Really there's too many variables to figure out any accurate "average".

 

[Mark97213]

Well, at this point, I'm about ready to scrap the Alpine amp and opt for something... anything, similar in size.