[jonywalker]

I have been looking for a suitable high-end 4-channel amp for quite a while, it shoud be: high SQ, solid, balanced input and small in size. I found it finally, it is the Steg QM75.4x, and I ordered it today. It will drive my front and rear speakers. Actually the Alpine PDX could be quite interesting too, but I don't trust class-D amp very much. The Stegs are those comparable to Audison (both are made in Italy, nice design ) but with balanced input, power management, precise xover within 1% toleranz. The QM75.4x is just so small I could put it into the place where the oem amp is siting. Something negative is I have to tell them what a xover point I expect to have. The xover will be set via AXQM2-Module. The first point is free, any additional points have to be paid. Is it the marketing .
I read in couple of hifi forums, it was quite high rated, belongs to top model, and has warm SQ.
Another drawback is the sensitivity between 0.1 - 3.5 v. The max HU output is 4V, could it be potential problem for clipping? Sure, DQSX will solve the problem, but I don't have this expensive box yet.
Is there anyone experienced with Steg amps?

[VP Electricity]

exmaxima over on bimmerforums is a big Steg fan as I recall. No importing into US for last few years, butif you are a member of bf.c you can ask exmaxima.

Not marketing, they just don't trust cheap potentiometers... more accurate, but poor user design.

Have to look for EU members on the experience, i'm afraid.

[jonywalker]

I see, although they are also available in Japan and China. But at least I have the opportunity this time to compare it with my JL slash. I will be back.

[ksquare]

I have Steg 105 X 4 to drive the fronts and 75 X 4 to drive the rears (in bi-amped config).

Am very satisfied with it. One comment though, using just the 75 X 4 to push the rears and fronts may not get the best out of the speakers, depending on what speakers you are using.

[jonywalker]

Originally Posted by ksquare

I have Steg 105 X 4 to drive the fronts and 75 X 4 to drive the rears (in bi-amped config).

Am very satisfied with it. One comment though, using just the 75 X 4 to push the rears and fronts may not get the best out of the speakers, depending on what speakers you are using.

You are using bridged system to get 210x2 for front and 150x2 for real effectively, right? So as my same question, ist that not too much for driving just highs and mids? There is even another discussion launched for rattling problem, I am getting liitle scared to turn right loud at the moment . I am told the Stegs have real constant speaker output for a power supply ranging from 10,6v - 16v, so I think the real 4x75w should serve my needs. For subs I keep using the JL. It's a little pity that I didn't realize the Stegs have the balanced input too, otherwise I would use all of them, especially my speaker system comes from the same vender who is also responsible for Stegs.

[ksquare]

Originally Posted by jonywalker

You are using bridged system to get 210x2 for front and 150x2 for real effectively, right? So as my same question, ist that not too much for driving just highs and mids? There is even another discussion launched for rattling problem, I am getting liitle scared to turn right loud at the moment . I am told the Stegs have real constant speaker output for a power supply ranging from 10,6v - 16v, so I think the real 4x75w should serve my needs. For subs I keep using the JL. It's a little pity that I didn't realize the Stegs have the balanced input too, otherwise I would use all of them, especially my speaker system comes from the same vender who is also responsible for Stegs.

No. I did not bridge them. the 105 X 4 is used to drive the front in bi-amped configuration. 2 Channels (for left and right) used for the mids and high whereas 2 Channels used to drive the woofers underneath the seats. This is easy especially when I use the crossovers.

For the rears, 2 channels used for the highs and the other 2 for the mid woofer.

I have also installed a REAL subwoofer in the trunk. And yes, you right, the subwoofer does give me rattling problems. The rattle seem to come from the rear panel. I'm thinking of using some dampeners to make sure it doesnt rattle and the panel fits tightly.

[jonywalker]

I am still waiting for the shipment of the amp. How are you satisfied with the whole system? assumed you also replaced the OEM speaker system. Are there still any frequencies missing in the spectrum, especially those between sub and mid-bass? My front and real are still driven with the OEM amp up to now and those frequences are missing or at least inadequate. If this is due to the HU preprocessor then only an EQ DSP could recover it. Did you add an EQ in the system? I would be grateful for your info.

[ksquare]

Originally Posted by jonywalker

I am still waiting for the shipment of the amp. How are you satisfied with the whole system? assumed you also replaced the OEM speaker system. Are there still any frequencies missing in the spectrum, especially those between sub and mid-bass? My front and real are still driven with the OEM amp up to now and those frequences are missing or at least inadequate. If this is due to the HU preprocessor then only an EQ DSP could recover it. Did you add an EQ in the system? I would be grateful for your info.

Having each amp channel driving each speaker driver, I can say I am very happy with my current setup, safe for the subwoofer rattling which I intend to have it fixed.

My car had the basic 6 speaker setup without an oem amp. This system's rear signals has its low frequencies cut-off. I basically used rf360 to sum the frequencies to enable a full range frequency for the rears but it somehow didn't do a perfect job, there's a small section of the mid-low bass frequency still missing.

The rf 360.2 has summing capabilities, flattening the original signals and has eq functions as well.

So, if your oem system is the same as mine, suggest you focus your upgrade attention more on the fronts. I probably overinvested on the rears.

Apart from the steg amps, I replaced the oem speakers with a 3-way morel elates system whereas the rears have 2-way morel elates.

The subwoofer is powered by a steg K2 amp driving a 10" elate woofer in conventional rectangle box.

[Technic]

Originally Posted by ksquare

Having each amp channel driving each speaker driver, I can say I am very happy with my current setup, safe for the subwoofer rattling which I intend to have it fixed.

My car had the basic 6 speaker setup without an oem amp. This system's rear signals has its low frequencies cut-off. I basically used rf360 to sum the frequencies to enable a full range frequency for the rears but it somehow didn't do a perfect job, there's a small section of the mid-low bass frequency still missing.

The rf 360.2 has summing capabilities, flattening the original signals and has eq functions as well.

So, if your oem system is the same as mine, suggest you focus your upgrade attention more on the fronts. I probably overinvested on the rears.

Apart from the steg amps, I replaced the oem speakers with a 3-way morel elates system whereas the rears have 2-way morel elates.

The subwoofer is powered by a steg K2 amp driving a 10" elate woofer in conventional rectangle box.

Your basic OEM sound system speakers (front and rear) frequencies are filtered at the 4" speakers itself, not at the OEM HU outputs. So I don't understand why you need to sum any inputs into your aftermarket amp if the full range OEM HU outputs are used.

You can see a graph of the OEM HU frequency response thru the RF 3SIXTY.2 if you use the "OEM" setup procedure (a before-normalization and after-normalization graph), so it should show a full range signal (and fairly flat itself) before normalization.

Thus, you will not notice too much of a change in sound quality if you go "OEM" or "New Setup" at the 3SIXTY.2 initial setup procedure because of that fairly flat OEM HU output.

[ksquare]

Originally Posted by Technic

Your basic OEM sound system speakers (front and rear) frequencies are filtered at the 4" speakers itself, not at the OEM HU outputs. So I don't understand why you need to sum any inputs into your aftermarket amp if the full range OEM HU outputs are used.

You can see a graph of the OEM HU frequency response thru the RF 3SIXTY.2 if you use the "OEM" setup procedure (a before-normalization and after-normalization graph), so it should show a full range signal (and fairly flat itself) before normalization.

Thus, you will not notice too much of a change in sound quality if you go "OEM" or "New Setup" at the 3SIXTY.2 initial setup procedure because of that fairly flat OEM HU output.

Thanks technic for your input. But this now makes me confused. I did see the graph. Only the fronts are full range, not the rears. That's why I had to sum it. Also, the OEM signals are NOT that flat and has a big hump in the high frequency range

I could have easily just used the front signals to drive both the front and rears, but then I will lose my rear PDC, which I dont.

Somehow, my experience with yours is quite different. It should not.. Different Headunits?

[Technic]

Originally Posted by ksquare

Thanks technic for your input. But this now makes me confused. I did see the graph. Only the fronts are full range, not the rears. That's why I had to sum it. Also, the OEM signals are NOT that flat and has a big hump in the high frequency range

I could have easily just used the front signals to drive both the front and rears, but then I will lose my rear PDC, which I dont.

Somehow, my experience with yours is quite different. It should not.. Different Headunits?

We do not have that basic system in the USA, however according to the OEM description of your system the OEM HU should be outputting 4 channels of full range signal.

Are you tapping these OEM HU outputs immediately at the back of the radio or somewhere else?

If this is not correct in your system, then it seems to me that this is another set mode in the OEM HU when it is part of the basic system, as all the OEM HU -regardless of sound system, basic, HiFi or Top HiFi- are the same unit, but set differently by software depending of application.

[jonywalker]

Originally Posted by Technic

if the full range OEM HU outputs are used.

I think it is true although I have the non-logic7 hifi. The OEM amp sums front and real channel to build the subchannel, it is proved by turning the balance to real you still have the bass.

Originally Posted by Technic

Thus, you will not notice too much of a change in sound quality if you go "OEM" or "New Setup" at the 3SIXTY.2 initial setup procedure because of that fairly flat OEM HU output.

I am afraid the HU output is not flat, but to say 100% I have to install the Steg amp at first which will arrive today or tomorrow.

Does the HU have a hidden EQ that is only accessible for logic7, or is the EQ located in logic7 amp?

[ksquare]

Originally Posted by Technic

We do not have that basic system in the USA, however according to the OEM description of your system the OEM HU should be outputting 4 channels of full range signal.

Are you tapping these OEM HU outputs immediately at the back of the radio or somewhere else?

If this is not correct in your system, then it seems to me that this is another set mode in the OEM HU when it is part of the basic system, as all the OEM HU -regardless of sound system, basic, HiFi or Top HiFi- are the same unit, but set differently by software depending of application.

I tapped the signals from all the speaker wires, so it is certainly not full range for the rears. If the ones in US are full range, then it is wise to spend the money on the rears, if one has the luxury.

If both of us are right, then, bmw must have cut the lower frequencies somewhere in the middle of the signal transmission to the speaker.

[Technic]

Originally Posted by jonywalker

I think it is true although I have the non-logic7 hifi. The OEM amp sums front and real channel to build the subchannel, it is proved by turning the balance to real you still have the bass.

Yes, the HiFi amp have a 6 channel output from a 4 channel input.

I am afraid the HU output is not flat, but to say 100% I have to install the Steg amp at first which will arrive today or tomorrow.

Does the HU have a hidden EQ that is only accessible for logic7, or is the EQ located in logic7 amp?

That's the reason I say fairly flat...

The adjustable EQ is part of the Top HiFi amp.

[Technic]

Originally Posted by ksquare

I tapped the signals from all the speaker wires, so it is certainly not full range for the rears. If the ones in US are full range, then it is wise to spend the money on the rears, if one has the luxury.

If both of us are right, then, bmw must have cut the lower frequencies somewhere in the middle of the signal transmission to the speaker.

It is not going to be the first time that an OEM document is not accurate or has missing information...

[VP Electricity]

Originally Posted by Technic

We do not have that basic system in the USA, however according to the OEM description of your system the OEM HU should be outputting 4 channels of full range signal.

Are you tapping these OEM HU outputs immediately at the back of the radio or somewhere else?

If this is not correct in your system, then it seems to me that this is another set mode in the OEM HU when it is part of the basic system, as all the OEM HU -regardless of sound system, basic, HiFi or Top HiFi- are the same unit, but set differently by software depending of application.

Please be aware that US-spec E60 HUs in non-Logic-7 systems have internally high-passed deck-power amps running the 4 door speakers. There is a single mixed-mono balanced signal output running the sub-only amp which has its own low-pass xover in it. Wouldn't be surprised to see something like it in EU E90s...

[jonywalker]

Originally Posted by VP Electricity

Please be aware that US-spec E60 HUs in non-Logic-7 systems have internally high-passed deck-power amps running the 4 door speakers. There is a single mixed-mono balanced signal output running the sub-only amp which has its own low-pass xover in it. Wouldn't be surprised to see something like it in EU E90s...

does it mean the basic system HU has no lower frequencies on front and real channels, but only on the 5th subchannel (mono)?
Since the basic, Hifi Standard and Logic-7 all have the same HU, how many audio output connectors does the HU provide?

-Basic System: 4 + 1 speaker level (4x15w + 40w) output?
-Hifi System: 4 balanced higher level (4v) lineout.
-Logic 7 System: Digital output (optical wave cable) or analog 4 balanced higher level lineout with digital sound process control cables

Does anyone have a photo of the back of the HU?

[Technic]

Originally Posted by VP Electricity

Please be aware that US-spec E60 HUs in non-Logic-7 systems have internally high-passed deck-power amps running the 4 door speakers. There is a single mixed-mono balanced signal output running the sub-only amp which has its own low-pass xover in it. Wouldn't be surprised to see something like it in EU E90s...

I thought that all USA BMW sound systems are HiFi (external amp) since at least 2003...

[VP Electricity]

Originally Posted by Technic

I thought that all USA BMW sound systems are HiFi (external amp) since at least 2003...

Can't shoot a man for thinking...

But I've read the BMW wiring diagrams AND worked on the car that matched.

I downloaded a bunch of PDFs from bmwtechinfo today and will be reading them...