dogbaker

May I ask your opinion; on the rather new to north america DEX-P99RS as a source unit. Quality of components, bang for buck $1400 msrp. Scale 1-10.[/QUOTE]
Sure...

I'll look into it and get back to you...

DeadlySones

iTrader: (4)

I have a question...

My Atomic 7K was going into protect for no reason. Even @ cold temps first thing @ startup. If I reset it with my deck it would work fine or cut out a second time, then work for several days before doing it again.

About an hour ago, it popped, and I have one blown FET on each side of the amp. They do not look fried, or melted... rather "popped". Any thoughts on what is causing this? Things to check for?

dogbaker

I will answer you later if that's okay... As I would like to provide you with a full and sound answer and I am a little typed out after answering AAAAAA's question(s).

But I will answer you.

dogbaker

Has the amp been repaired before or was it purchased used or as a refurb?

What brand and model number is the deck?

How old is all the gear?

I do have some thoughs for you, but wouldlike you to anwser these questions for me first...

Thanks

While I am wating for your answers, I have noticed that you list Pioneer - if you have a Poineer head, I think I know what the problem is...

I was speaking with Hector, an engineer from Atomic a few years back, after I had one of their amps blow virtually every component while on my bench... and we got to talking at length, and he mentioned to me that for some reason unknown at that time, they were seeing a lot of amps coming back with symptoms and failure like yours...

He later determined what the issue was - however, I can't recall if I am free to share what it was/is with you...

At any rate, your easiest fix may be to change your head unit after you get it repaired, or put a differential circuit between the head unit and the amp...

I bet if you email Atomic in the US, that they will help you!

At any rate, please answer my questions and I will offer more insight...

It's clear that you were suffering current over runs and finally one got past the protection, there are a few common reasons for this...

DeadlySones

iTrader: (4)

Yes, it was bought used and has been used in competition for a little while. It's seen some low loads and I use it for a daily amp.

fresh1

iTrader: (2)

Do you mind if I ask what the issue with the Pioneer head units is? I run one as well and I believe its the cause of my problems, but I'm not 100% sure.

dogbaker

If it has been repaired in the past, and the drive transistors weren't replaced at the same time as the outputs - that could cause this - Gate/drive FET's and related circuits could also be malfunctioning, or it could something in the power supply causing current over runs and that's what I suspect, because Pioneer and Atomic have had electrical incompatible reported between them, which cause these types of problems...

Do you know how to test outputs and transistors?

I would have atomic repair it and I would build a differential and interconnect it between your head and amp after the repair...

Make sure that they replace every output and all drive transistors!!! And ask them to check the gate drives etc... and definately mention that you are using a Pioneer Head unit, as there is a strong potentail that your power supply was able to find a path to ground through the RCA's...

Without having it infront of me, there isn't much more I can do...

dogbaker

I think that it has something to do with common-mode rejection issues - and it's not necessarily just a Pioneer thing - it's somewhat more common then you think - but don't quote me...

Balanced is always the best policy!

fresh1

iTrader: (2)

no idea what it means so I won't hit the button

dogbaker

As promised!

So you were told that by separating your tweeters from your mids and so-on, that such can lead to some loss in fidelity...

Regardless of where you came across this data, it is in fact true. The fact is, we are striving to create a single driver that can accurately reproduce a bandwidth from 20Hz to 20KHz, and as a point of fact, there are already several that to some extend meet this goal, but they don’t handle much power and they are very box picky and are weak at the top end of the bandwidth...

In the 12-Volt world, we have the coaxial driver which is in fact; two drivers mount one in front of the other, on the same axis – hence the term coaxial. Now in fact, coaxial have many sonic advantages over separates, but haven’t been touted as having such, because for the most part, while the mounting is superior, the drivers used are often not... But for those in the know, if you will, strive to find high-end, high quality coaxial variations of their favourite separates or simply take their favour separates and make a custom mounting system, which arranges the driver in a coaxial fashion – then strive to install them either on or in the dash, in the kick panels or as a last resort – in the stock door locations.

While there are many things occurring hear, all of them are related to phase and the resulting constructive or destructive interference patterns that occur. When a multiple of drivers are utilised to radiate a bandwidth, inherent phase errors occur, which are commonly referred to as Lobing. When a single driver, a coincidental driver or a coaxial is implemented, Lobing mitigated.

Understanding Lobing

Lobing occurs when sound waves are radiated from two or more driver locations, creating an irregular off-axis frequency response.

Picture yourself sitting an equal distance between two individual drivers, now as identical tones begin coming from each, they will all arrive at your ears at the same time, adding together, summing their outputs, creating a prescribed frequency response, increasing the overall volume, while simultaneously creating an ambient sound field, which in true high fidelity system, would possess a transparent 3-dimensional sound field, producing a strong image of instrument placement etc...

Now picture that you have moved one speaker back a distance equal to twice that of its previous distance, from where you are sitting. This time, as the tones reach your ears, they are out of phase; where some tones are at the peak of their phase (90-degrees – 250ms), the others are at their trough (180-degrees-500ms), so they cancel completely and you hear nothing. Now this is an extreme occurrence, but what normally occurs, is a degrees of summing and a degree of cancellation...

Along with these effects, as each driver becomes further and further apart, they become more beamy and easy to localize and discern as a separate sound sources – less or no unity in radiation – not a desirable occurrence in higher quality systems...
In this way, frequency response and sonic stereo fidelity is altered, negatively.

So what can be done about it?

1. Use less drivers – positioning them as vertical as possible
2. Place drivers as close together as possible & as on axis with the listener as possible
3. Use coaxial or other similar drivers
4. Extensively rework a passive cross-over – very tuff and expensive to get right
5. Incorporate a completely active, multi-channel DSP & Amplification network – with manual time alignment features and tweak it up!

In your case, if your mids are in the door and you drop your tweeter to meet them, your sound stage will drop as well, because 75% of your bandwidth is radiating out of your tweeters... move your tweeters -move your sound stage; however, if you’re able to modify the doors and angle both the tweeter and mid-range upward, you will probably enjoy the new sound over your old...

Perhaps you could use a little 3M (yellow) double sided tape and temporarily move/ adhere your tweeters at various locations on the door to: a) determine the best location and b) to determine if you’re likely to like the new sound...

As a tip get creative - I put mine under my seat aiming upward and in this way, they are closer to my mids, the radiation pattern is aimed up and the location is difficult to discern because the tweeter are down low and back, but their radiation sounds as if it's coming off the glass.