The HK amp has been blown for a while now, a friend proposed to give me an Alpine MRP-F300 and a pair of diamond 362.5 speakers to stop me from whistling in harmonics with the supercharger whine... it is definitely not a good scene along with the "music" as the weather is getting cold in the mid west... I think he got a valid point.

I have searched on this forum, and still need help to get the thinking started:

1) Can the MRP-F300 be run as a replacement of stock HK amp? leaving HU and speakers alone?

2) If so, can it be fitted in the boot where the stock amp used to be? What need to be done?

3) If not what need to be done to make it work? Other options?

I am not looking for superb sound (shame that I used to be a pro in music), just something casual.

All inputs are welcome, thanks in advance!

-X

PS. This forum provided great info for the Mini, the wealth of information here enabled me to replace the supercharger along with pulley installs. Though I have followed the forum for a while now, this is my first post, hope to get some guidance!

 

I don't think there is any amp that is plug-n-play compatable. Best bet is to find a used but working h/k amp from someone upgrading their system. I recently bought an h/k amp and head unit from someone who had totaled their car. Paid $125. Its on my shelf in case my system fails.

 

Without getting an HK, how to make a 4 channel amp to work with stock HU and speakers? Anyone done this?

 

JAB67: you really got a good deal on the HK amp, I have not been able to find one for less than $350. Thanks for your reply, though I hoped people may have a quick patch scheme figured out with the HK.

Alright, the weekend is coming, here are some random thoughts and hope to get some buying from people, especially I have no experience in car audio yet. The goal is to get acceptable sound with minimal effort. I only plan to swap in the MRP F300 and a set of coil overs, use factory wiring, HU and speakers, and may cut and solder if need to.

1) Split the speaker level output from HK HU at the boot, and solder a y to split the 2 channel into 4. I hope this works with no issues - People loads the HU output at 2 ohms directly to the door speakers, I would imaging the 2K input impedance at the amp for speaker level would hold, given a split, I am fine with 1 K, hope I don't have to match nothing.

2) install the cross overs and get to the mid and twitter on each front channel. The amp is 2 ohm stable. The cross overs are merely LP and HP? No "out of range" spots, right?

3) if things work, the rest is tuning on the amp side. I am still not sure about volume adjustments, assuming this still depends on the speaker level output from the HU, and the amp is merely applying a constant gain per say?

Does these sounds reasonable? Please let me know if I am talking crazy.

I really really hope to fit the amp in a stock location. I have checked with magic mini's work and think his amp is a bit larger F600? Anyone fitted the F300? If it doesn't fit, that may be a show stopper for me. Also, I will be very curious to tear apart the HK amp, and check for corrosions as many others have pointed out.

Please share your thoughts. Thanks!

-X

 

I don't know anything about how the MRP F300 functions, but let me pass along just a few things about the HK and perhaps that may help you with your decisions.

The HK amp is a digital processing amplifier. The HU talks to it using a serial "K-Bus" and ALL of the setup information is passed to the Amplifier via the K-Bus. This includes volume, tone, fadder, left-right info. When you adjust your HU controls, all you are doing is sending data across the K-Bus to the amp, there is no control that is being done in the HU. The good news is that the HU does send audio as separate analog signals and my guess is that it is a "flat response" at a fixed level. So if the MRP F300 can't respond to K-Bus control data, you are not going to be able to adjust anything using the HU. Finally, the speakers in the HK system are rather unique in that they are extremely low impedance speakers (lower than most normal amplifiers are designed to work with) and a couple of the speakers are dual coil units. And the crossover network for the speakers is built into the HK Amp.

Just a few data points for you that may assist you in your decision making.

 

Hey, Liquid Yellow!

I have been following your posts for a while. First, great work you have done! Admirable. I have entertained with the thoughts of following your work and dissect the HK amp sometime.

The amp was in last night, and everything went well. The HK amplifier was replaced with the Alpine MRP F300 only, with the help of two cross-overs for mids and tweeters - maitaining the 2 ohm on front channels. Stock harness was preserved and used with my home made pin connectors.

Here are some notes:

1) Volume works.
2) The HU acts like a basic radio without the spatial/characteristic pre-sets, I wonder whether an Ipod or any sound player via AUX may compensate lightly.
3) Since the 4 channel output is tuned from 2 channel, there is no back fades, this is the only item that it does not have full control as a basic radio, and this was addressed using the gain setting on the amp to set a front-and-back preference. Minor tuning was done on the build in cross-overs on the amp also, note that the cross over on the 4 output channels may be set in a way to enable semi front and back fades via base and alto adjustment in the HU.
4) Amp is 2 ohm stable, and everything sound fine per my casual expectations. On this regard, the cross-overs need to be re-tuned/modded to match the 2 ohm loads. The reduction from 4 ohms typical to 2 ohms reduced the cutoff frequency by half given a 2nd order cross-over expecting 4 ohm loads.

5) The amp is pretty compact, but a little thick to be inserted behind the liner, it is mounted on the removable cover.

Liquid Yellow, thanks for the knowledge sharing, I may tear apart the HK sometime and have fun per your findings.

-X

 

Hi CC,
So from your above comments can I assume that you are saying the MRP F300 has an input for the serial K-Bus and responds to the control data that is being sent to it from the HU?

 

The only outputs from the stock HK HU were, L R and remote. I never experienced a working HK - long story. It is operating as a basic stereo without HK features.

Amp wise, I would think anything takes high inputs and four channel output would work. BTW, The Alpine MRP F300 (installed here) is a very typical amp.

-X

 

I can't speak from experience because I never got to the point of taking my HU out of its mounting, but I can tell you that it has a 3 wire K-Bus connection somewhere on it's chassis. That is the only way "I thought" that it could set the HK volume, tone controls, etc. You are blowing my mind when you tell me that you are able to adjust these controls on your HU and your Alpine is responding to these changes. My understanding was that the HU had NO EFFECT at all upon the audio that it sent back to the HK amp.

So lets take this one step farther. Do you have control from audio OFF up to what most people would call FULL VOLUME?

And although I can understand the differences you hear in the speakers due to the cross over, do you have a reasonable amount of control over the tone control for the audio?

I have no idea how this can be, but it's great news. This means for approx. $230 (you got me to go out on the web and search for the MRP F300) I can have audio again!

 

Yes to all of your questions.

Volume adjustment is functional. I did not crank up the volume too much by tuning the HU ***, it got pretty loud with the "norm" gain setting on the amp - this is a small car, the fronts are right at you! Via remote, the amp is off when the HU is off too.

LR balance works, as well as base and alto adjustments (forgot how to spell the right word). Let's see, I think that is basically it. Radio works too. Let me play with it for a little - I am going to do an AUX install, need to search for the recipe somewhere here

Any amp with the above-mentioned capacity should work. This one was randomly (now) sold to me.

-X

BTW, the work you have done is amazing, requires skills, efforts and tools, and resulted in tremendous amount knowledge that is hard to obtain publicly. Have you got the amplifier chip and tried that out? What is the current findings? Again, that was great work.

 

Well, this is great. Please keep me in the loop regarding your progress and when you have the time, I would greatly appreciate it if you would diagram up your system and how you interconnected it to the MRP F300 including the remote wire coming from the HU. I believe from the way you describe it this must be the "radio on" line that the HK monitors to wake it up. I was going to ask you how much current the Alpine draws at idle, but apparently you are using the remote line to shut it down.

I look forward to hearing from you as you progress with your project.

 

I will put things together then. It is very simple, pin connected everything off black and grey HK harness. Two things I think worth noting.

Each channel of the LR from the head unit was splitted to have a high level 4 channel input - no worries with the 2K input impedance on the amp.

I need to find out more on this one, and make sure about my understanding on the rear channels. If each coil (2 on each side) is 2 ohm, then I need to redo/mod the setup a bit. As I was typing, this is what I was thinking "The left and right "double" rear speakers (4 ohms each coil, 2 on each side) are wired in parallel to the two corresponding output channel on the amp to have a 2ohm load within spec of the amp". But now, I am not sure and the specs ... anyone knows? I don't have a fluke right now.

-X

 

Sorry, I missed the last part of your post. If I am reading your question correctly, you are referring to the audio power out circuitry in the HK Amp. I have no reason to believe that this part of my HK amp isn't working. Trouble shooting to this point is indicating that my HK amp is unable to either read the incoming K-Bus commands, or is reading them and is unable to respond to them. Basically it appear to still be in the "OFF" state (which would prevent the power amplifier from turning on). I built up the K-Bus monitor circuit and downloaded the S/W for reading and sending K-Bus commands. I can see my HU send out a broadcast command when it is turned on (and it's the right command), but that is supposed to cause the HK amp to respond with a download of data to the HU. No K-Bus data ever comes out of my HK amp yet all of the input circuitry appears to be receiving the commands and sending them to one of the internal CPUs. That is where I was at when the work load increased an order of magnitude at work.

 

The same headunit is used for HK and standard systems. The headunit only goes into "HK mode" if it detects the HK amp on the bus. If you disconnect the HK amp, the headunit behaves like a standard headunit. So it is relatively straightforward to replace the HK amp with an aftermarket amp, but you'll also need to replace speakers or add crossovers since the HK system has crossovers built into the amp.

You might find this pinout list from GBMINI (Ian Cull) useful: http://www.gbmini.net/downloads/HKconnections.pdf. Ian studied the HK behavior and developed the HK Enabler for connecting an aftermarket headunit to an HK amp. He has posted a lot of information about how the HK operates but unfortunately it's hard the find using the forum search.

 

Thanks rkw, good info, the same head unit enables those I thought "missing" rear channels if diligent people decide to run wires to the amp, or use the existing Kbus wire and something to get the rear channel routed to the back.

Both Ian and Liquid Yellow did fantastic job on getting inside the Kbus from different angles. I learnt quite a bit from them both especially Ian's blog, every well documented. LY's threads are technically rich, I was going to ask whether he is a digital guy in EE.

I believe now from slight readings, the rear coils are 2 ohms each instead of 4, this warrants corrections in my connections, as I am running these coils to each rear side in parallel, thus 1 ohm!!!!! :D Yeah, did I hear bass??

The current bandage on top of this patch is straightforward (one coil at 2 ohms and crank up gain, series connection the amp takes 4 ohms typical, 6 channel amp ... what not) each with its own limitations, but at least there is sound and is workable and can tuned if minimally with the amp.

On another thought, I am tempted to make some passive cross-overs from scratch, for both rear and front with proper impedance match. In that case, fronts are simple since the tweets and mids are supposed to do different things, but the the rear, hmmmm, really depends on how I want it to sound, it probably wouldn't sound right as they are meant to be doubled up.

So, I think I will series connect the rears on each side for now, and will update.

Well, I am writing this post and thinking along here ... time to get going and continue the fight with pulley tensioner now, cheers.

Update: Connected the rear in series on each side works well, sounds even cleaner than the previous incorrect parallel scheme. If the cross-over for the fronts are correctly tuned, I am happy.

-X

 

Hi rkw,
I want to thank you for posting the above piece of info. Although I read the part about the HU "going into HK mode" when it received the K-Bus response from the AMP, I didn't know that the HU was also used for the standard (non-DSP HK Amp) system, and therefore would revert to local front panel control. This was becoming somewhat obvious based upon the efforts that CooperCooper had put into the repair of his system. This is going to be a tremendous plus to those Mini owers with the HK amp upgrade who have experienced failure of their amp. I did a little searching on the web last night after CC and I finished our posting and found that the Apine MRP F300 is available for as low as $135 (e-bay had one for $85). This is a very reasonable price range when you look at the going price of a used HK Amp, which in all likelyhood will fail like all the others.

I fully recognize that this in no way will presently provide the full functionality that the HK Amp provides for the other services in the Mini such as the Nav system, Blue Tooth, voice commands, etc, but at least for a very low cost we can get back the use of our radios...it is a very lonely trip to and from work each day without my radio!

 

My understanding is that the HK amp facilitates the additional digital processing of the "upraded" HK system (meaning the HU is just an HU). This thread seems to be supporting that. CC- did you lose function of the wave alignment for the driver position after the switch?

 

Super,

I have not experienced a functional HK, and can not confirm, I have not found any "wave alignment" adjustment anywhere on the HU. It sounds to me that this is a signal processing feature that provided by the HK amp, from its name I guess it is a kind of spatial manipulation/beam steer/phase tweak of sounds orchestrated via multiple sound channels, this I believe is quite unique to the HK system. Maybe that would be Ian's or Yellow's next project - whip together an adjustable delay circuits for those channels prior the inputs to the amp, or better yet take a Netbook and resample the sounds and do processing that way :D (yes, I am kidding)

On another topic, during a trip to HomeDepot today, I learnt that volume gains with speed as well as all the buttons on the steering wheel works too. It seems to me that all that was lost from the HK is some kind of signal manipulation or "enhancement" specific (if) to the Minis.

-X

 

The option is called "driver" in your tone control menu. It aligns the sound to the drivers position (more or less). My suspicion was that all the digital processing was occuring in the amplifier, knowing that the HU is used in both systems, it makes sense that the steering controls and other basic HU funtions remain intact (including analog output of the audio signal). It seems between the posts on this thread that my suspicion is confirmed. You experiment has been very helpful. Thank you. Some of the DSP setting In the HU change the rear 6x9"s from full range to low pass. I just wasn't sure where that processing was taking place. Thanks too all who posted in this thread.

 

Update: These caps and inductor set up the cross-over just fine, I would recommend people wanting to do this, to get good inductors particularly with little series resistance, air core is a must to stay free from hysteresis! Caps, polyester is fine. So, for now, the HK amp replacement is pretty much wrapped up - you can get by safely with a 4 channel amp and two caps and inductors and leaving the rest stock, HK amp removal via the method documented on ShankRabbits site without taking part the plastic liner - all together the cheap and lazy recipe.

I did a some simple calculation on a first order passive cross-over for the front assuming a constant 2 ohm resistance.

For a cross-over frequency at 3KHz.

The cap for the tweeter channel (highpass) is about 26 uF.
The inductor for the mid channel (lowpass) if I remember correctly 106 uH.

I particularly liked the overall flat response in magnitude feature of the first order, and thought I would test it out and see whether I mind about the slow fall off. From my calculation there is still a +3 dB hump centered about the cross-over frequency which is contradictory with the "feature" (my bad, did not add phase into the picture).

Just now I implemented the cap (25 uF) and the inductor (100 uH) on one side (parallel) by twisting the wires together, and clearly more mids are brought out and the tweeter is more relieved compared to the other side which still has the typical crossover hooked up. Though I thought I did not enjoy the clarity (I have lousy caps and metal core inductors...), but maybe it is just placebo.

Anyone, please feel free to chime in!

-X

 

This is just AWESOME!! Reading you two guys (CC and LW) was kind of like reading ****, just over audio. I am so disgusted over my POS H/K amp problem I just put ear plugs in and listen old school.
I have tried and failed to get the amp repaired but no one will touch it. I am beating a dead horse, for sure.
So after all of your technical intercourse, what I would like to find is a unified theory of amp replacement.
Any other parts that would be needed?
I would bring them all to an audio guy to assemble.
This is kind of l ike an "idiot's guide".
Without too much technical jargon, could y'all make a list of what all I would need?
I am sure there are dozens and dozens of H/K owners that would find this a great help!

 

[SIZE=3][FONT=Calibri]Has anyone looked at other BMW HK amps other than MINI for compatibility? I happened to be searching ebay and there are a lot of HK amp for BMWs that look the same as ours and a lot cheaper. Even the connector looks the same. The way our amps are assembled the connector is mounted to a board which plugs to the main board. I was wandering if all of these amps are basically the same other than the connector and HK just plugs the appropriate connector board based on vehicle model it is installed either MINI or BMWs (Z3 or 3 series 323/325/328/330/M3 …)[/FONT][/SIZE]
Juan

 

Sorry for not keeping up with the thread. My HD crashed and I lost everything, troubleshot, reconfigured, and went back to sweet Linux ( struggle between Fedora and Ubuntu) and back online now.

I do not have a write up anymore, I sent a rough and brief write up to Yellow.

About the other BMW amps, I remember seeing someone talk about it and some people swapped his wifes amp into his Mini and thing "did not work right".

I guess, it would be interesting and see whether other BMW amps can be modified by swapping the interface board with the one came with the Cooper. Per Yellow's finding, the processing circuit may be the issue, since no response was captured from the processing end of the Bus. I may revisit this project after some other priorities are taken care of.

Good luck!

-X

 

ok so i am pretty much an audio n00b, i put a HU, speakers, amp, and subs in my truck 3 years ago, but it was a single cab truck without any prewiring. plus i replaced everything.

With the mini, and correct me if im wrong, i dont need to upgrade my HU? that it goes into a normal mode when it doesnt find the hk amp? and that if you hook up an aftermarket amp, you can keep the same speakers if you use a crossover??

 

Well , if you want to upgrade you should know if you have a h/k or Harman Kardon system, you need to re-wire all the speakers , you can keep all speakers but need to be re-wired,second option is a h/k enabler , really spensive , but effective, you can find that on ministuff web page , either way harman kardon speakers sounds really cool with an after market stereo, since you control the sound not the system by itself, I ran all connections to the amplifier and do the connections there at once, using 1 crossover for the tweters( not necesary but better be safe) for clear sound, plus add an jl amplifier with a punch power sub, could be not the best sound but a least make some heads turn over when volume goes up....