I am going to delve into the sound system (finally). Initially I am considering keeping the stock head unit , an MTX 5 channel amp, stock hk speakers, and a JL stealth box running off the fifth channel. Running both sides of the 6x9s and adding caps as needed to the whole system. From what I can tell the only way to get full spectrum sound without the delay is to run the HU in spatial mode. I would like your help in deciding what to do from there. If it won't work I will change the HU, and then move to speakers as needed.
OK Minihune,TacoTim,DaveBrett,Ryephille and the rest of you audiophilles, talk to me. Remember talk slow and use small words.

 

I think pooky13 replaced the amp and kept the HK speakers ...

Issues include the need for a crossover on the door mid/tweeter combination (there is a cap for the tweeter, but you need to cut the bass going to those speakers).

Also, the rear 6x9 speakers are DVC 2ohm coils; if you wire in parallel you will have a 1ohm load which most amps won't like. Wiring in series will give you 4ohm and you will need a powerful amp to get a good level of sound.

 

I'm enjoying my car so much it hasn't been in the lab yet for any objective measurements, but if I had to identify strong and weak points of the HK system based on listening impressions and experience I'd say:

Strong points: Excellent front mid-bass, midrange and treble tonality. From vocal fundamental frequencies (150-1000 Hz), to upper midrange and treble the system is very well balanced. It would be nearly impossible to match its overall balance without parametric EQ and/or custom designed speakers and crossovers. When turned up loud the bass sounds very punchy. For me this system plays loud enough unless I have windows down over 80 MPH. I have more conservative musical tastes...

Weak points: With mediocre program material bass can sound boomy, especially on FM where stations accentuate bass and use a lot of compression. 60-80 Hz seems accentuated, masking lower bass. If you turn it up it seems like it's there, just masked by the upper bass. For better recorded music I think the system is only slightly boomy, and I might (without data) venture a guess that this bass "tuning" is an optimal balance of bass level, extension, output level for most program material, windows open/closed, vehicle speed.

The rear speakers don't do a lot, but bass duty. This doesn't bother me at all, but seems to be a sore point for many. I guess they could provide ambaince fill, but I feel rear's should only "pull" and image if you fade rear 2-3 clicks anyyway...

So what would I do if I, or a good friend, wanted to upgrade the HK: Either buy or build a simple electronic high-pass crossover to insert in the line level signal between head unit and amp. This would let me filter low(er) bass from the front door speakers and 6x9s, and possibly give me enough control of the 60-80 Hz region to eliminate the apparent boom to my taste. Because I'm not replacing the HK amp, I keep all the vehicle/speaker specific equalization/filtering that makes the midrange well balanced (believe me, this can make a huge difference). I also don't add cost and complexity of re-architecting the system (once you decide to replace amp or HU, you have to replace the other, without complexity, though iancull is doing something interesting)

There is a lot of power driving the front door speakers and 6x9s. 40 watts to each 6" (seems more like a 6" than 5.25" to me) woofer and 80 watts to each 6x9. With less bass demand these can play to louder clean levels.

Before adding a sub, I would adjust the filters on the front and rear channels to give the midbass/midrange output level I want. The more bass you take out, the louder each set of speakers will play before obvious/objectionable distortion, up to a point (if you never get to that point you may need more power than the 40x4 + 80x2 of the HK amp, but then I'd advise you're really damaging your ears, or making a system for non-vehicle-occupants).

Then you need a subwoofer that will play below the frequency of the HIGHEST crossover you set for the front and rear speakers. Subwoofers that have front chambers, like bandpass designs, or those that fire into the floor may have difficulty playing up to and above 100 Hz. The car will have "cabin gain" which is a natural boost to low bass. This is good for low bass, but can leave you with a "hole" in the midbass, if your crossovers are too high, and your sub doesn't reach high enough.

The subwoofer should be driven by all 4 channels coming from the radio, so that as you adjust fade or balance, the bass remains constant. You need to get your subwoofer signal before the crossover you insert between the radio and HK amp, or you filter the bass out of your sub. I don't think a sub smaller than 10", is worthwhile. It should have 15-20 mm xmax. My personal perference is for a light moving mass woofer with a huge magnet, suited for a ported or passive radiator enclosure. The port or PR does a lot of the work in the lowest octave, requires a smaller box for the level and extension of output, and the light cone and big magnet make for a driver that has enough efficiency to produce bass above 100 Hz, to avoid holes, and give good flexibility to tweaking in the best blend.

The woofer amplifier should include an adjustable high-pass filter to filter subsonic rumble, especially if a ported or PR sub is used. This greatly improves dynamic capability and durability. A 4th order filter, or high would be desirable. It needs an adjustable low-pass as well, preferably with adjustable crossover slope.

With some preliminary crossover points chosen for the door woofers and 6x9s, add the sub, and tweak the crossovers and sub gain more until the best overall sound is achieved. The acoustic crossover points will not necessarily be the same as the electrical crossover points indicated by your controls. Try to make the system sound clean, without missing mid-bass, and without all bass localizing to the woofer. You may need to invert the phase of the woofer and/or the front or rear speakers for the best blend.

There are also improvements that can be made to the packaging for each speaker. The front door trims resonate a lot. The system tuning takes this into account somewhat, so dynamat and/or added stiffening to the door may minimize a mechanical resonance, but it may compromise overall tonality. This is where measurements and double blind evaluations can shed a lot of light, and where my advice gets more difficult. The same goes for the 6x9s, the enclosure they're in could probably use some sealing/stiffening/deadening/stuffing... ...but again, the tuning takes into account some of this. You'd have to experiment.

Upgrading any of the speakers in this car, without re-architecting the system (new HU, Amp, Filters, EQ) will be tough to do without compromise. OEM amplifiers use low voltage power supplies, so their systems develop power from low impedance speakers. So given a low voltage input, you get a lot of sound output. Most aftermarket parts are 4 ohm, single voice coil. If you aren't careful about a speaker swap, then you could deliver 1/2 or 1/4 the power. As you might expect the output is 1/2 to 1/4 as much as before. Also the front "tweeter" is really a 2-way with a midrange and a tweeter. This covers a wider range than most aftermarket tweeters. While it may not look elegant, it does solve system problems with the chosen speaker positions in the MINI.

 

Tacotim,
Very interesting discussion - especially for me :smile:
My Kenwood HU has built in filters so I could cut frequencies below (say) 100Hz to the HK amp; then I could use the "non fade" RCA output to drive a sub amp. I would not expect engine whine because its frequency would be above the cut off for the sub.

But what benefits would this give? From your writing, I might see a more "smooth" bass response?


If I have your attention - I thought of an interesting(?) wierd idea today!
The rear 6x9s are DVC; the HK schematic refers to one as bass and one as mid; and it runs heavier gauge wires to one than the other.
So (without going out to scope the signals) let's suppose the HK only uses the "mid" coil in modes which send higher frequencies to the rear (eg: the SPATIAL mode).
What if I left the H/K in "MINI HK" mode, disconnect the "mid" signal to the DVC 6x9 and fed it instead from the rear speaker output of the HU?
Then maybe I could get rear fill while staying with the clean MINI HK mode of the HK amp ...

An experiment for a less rainy day :smile:

 

It could be that each coil gets a very different signal... You're proposing to do this with your unique setup-when you say HU, you mean not the stock HU that you have slaved off in the rear with fixed output levels, but your aftermarket HU. This may be very interesting interesting. You would give up any EQ, but it may be a good trade-off.

I'm out of town this weekend, but I'll make a point of measuring at least the signals to the rear 6x9s in the next week to see how feasible this idea is. If you have a scope and test tone discs, you should be able to get an idea yourself, if you're anxious.

To answer your other question, limiting the bass from the HK speakers and installing a sub would give the potential for:
1. More overall clean output.
2. Better low frequency tonality, tuned to YOUR taste
Notice I said "potential for" this means that you're taking variables into your own hands, and the overall quality depends on largely on you (your objectivity, patience, research into components/architecture, etc), not just the parts you buy...

 

>> If you have a scope and test tone discs, you should be able to get an idea
>>yourself, if you're anxious.
No problem with a scope - we even have one at work that does FFT! No test tones though - perhaps I could create some on a PC ...
Biggest limit right now is after finally getting my car back and reassembled, I am not ready to rip out the seats and panels again yet

>>Notice I said "potential for" this means that you're taking variables into your own
>>hands, and the overall quality depends on largely on you ...
Point VERY well taken; learning by mistakes teaches a lot!

 

>>I am going to delve into the sound system (finally). Initially I am considering keeping the stock head unit , an MTX 5 channel amp, stock hk speakers, and a JL stealth box running off the fifth channel. Running both sides of the 6x9s and adding caps as needed to the whole system. From what I can tell the only way to get full spectrum sound without the delay is to run the HU in spatial mode. I would like your help in deciding what to do from there. If it won't work I will change the HU, and then move to speakers as needed.
>> OK Minihune,TacoTim,DaveBrett,Ryephille and the rest of you audiophilles, talk to me. Remember talk slow and use small words.
Darksky,
What you propose is not different from what Pooky13 installed with very good results. Except she installed a pair of Zapco amps. I think one was for the front and rear speakers and the other was to run the JL Stealthbox. You might email- PM her for her feedback on the setup. I think she had one farad cap only. She kept the HU and all of the speakers from the HK system. Having the JL Stealthbox for added bass helped alot.

My impression is that you probably will not need to do much else- best is to contact Pooky13.
There are many options with the HK system and upgrades. In general for those that own HK I would say work with the settings first and know how to adjust them first before trying to spend lots of $$$. Then ask yourself what kind of music are you trying to listen to? AM/FM radio? Then you need a good tuner- maybe a different HU would help but if you live in a place with poor reception then that is a limiting factor. Do you listen to MP3 or your own CDs? Not as good source of music make it a bit toughter to get good sound quality. Key is to get the CD recordings as high quality as possible. Some people like ipod and MD or other sources. Make you setup good for what you typically listen to.

 

It hit me as I left the house that adding a sub between radio and amp will only work for iancull's situation, or where you have variable outputs from the radio. The HK has fixed outputs, and the gain is adjusted via a message sent to the amp...

It's an interesting problem to upgrade the HK system without totally starting over, or in general scrapping a big component in the system. I guess you could have a second volume **** for your sub, and adjust 2 *****... Not for me.

I really think that the HK amp, and its vehicle specific equalization is pretty important to retain. Some argue that the need for complex filtering is due to cheap OEM speakers. My company is branding partners with Boston Acoustics, so we have 4 show vehicles that use Boston Acoustics aftermarket components. The night and day diference between an equalized and unequalized systems exists as much in the BA cars as it does in OEM cars.

 

>>The rear 6x9s are DVC; the HK schematic refers to one as bass and one as mid; and it runs heavier gauge wires to one than the other.
>>So (without going out to scope the signals) let's suppose the HK only uses the "mid" coil in modes which send higher frequencies to the rear (eg: the SPATIAL mode).

Did a quick scope check today ... looks like both coils of the rear 6x9s are driven all the time; in some modes there appears to be different waveforms on the two coils, but at no time did I see no signal to one coil.
So my idea to drive a "spare" coil from the HU is a no-go; it would lose some part of the HK sound.

 

I've had a busy week, with a Toyota and Nissan in the lab. I can tell you all about their sound systems, but sadly haven't had the MINI in yet...

I don't think your idea is a no-go. It's really the right approach, it just may be a little more complex than disconnecting and reconnecting... Your HU has some EQ capability-it may be that you can approximate the factory settings, only with more mid and treble gain... This would only require an electrical response measurement, out of the amp, and some modeling (or cut and try) of the filtering your HU is capable of. You really are on the right track, finding a focused solution (without scrapping the entire system) for your particular complaints. If you haven't given up, keep in touch, and we'll figure something out.

If you're looking to add loud low bass to the system, a good approach (given more thought) would be to sum front woofer and rear 6x9 outputs, and amplify the sum into a large woofer or woofers. This would not have the advantage of unloading the stock speakers, but you would add loud, low bass. If you selected filtering carefully, you would add to the system's low end, without further aggravating the accentuated upper bass.

 

Darksky, to your original post, if you plan to use passive filtering, of the stock speakers, I would plan on 2nd order filters consisting of a capacitor in series and inductor in parallel rather than just a cap. A cap alone never gives a textbook filter response. To get the expected attenuation, without over attenuating your mid-bass and midrange, you need a little more complicated filter. The cost is greater, but it is really worth it.

Up until now I've really only considered actively filtered solutions, because the cost of good passive filtersc an be nearly as high as re-architecting with active/electronic filters... ...but, passive filtering is generally less complex. If you go this route, and need help with passive filter design, I'd be glad to help.

 

Hey Tacotim,

The passive filters you're speaking of, can you recommend any? There's way too much bass being pushed to the front woofers in MINI H/K mode and I was thinking some inline 60Hz cutoff passive crossovers would help.

Also, how does one go about adding a JL Audio Stealthbox to the H/K system? Would it be as simple as an RCA split of the cable coming from the HU just before the H/K Amp to branch the signal off to a 2nd amp that powers the JL Audio Stealthbox? That way, the volume would be controlled by one ****. This is assuming that the connection between the HU and H/K Amp is RCA. Is it?

 

CornOnTheCob,
The HK amp gets a speaker level signal from the HU.
On top of that, the level DOES NOT VARY with volume.

Easy wiring of the subs would require you to pick off after the HK amp, probably one of the (four!) signals going to the rear speakers ...

As I and other have said here ... the HK is what it is. Listen before you buy because trying to change it later is a challenge!

_________________
Ian C. Gloucester, MA
<A href="http://www.gbmini.net">"GBMINI"</a>...uot;</a>

CWFFC member. Indi Blue / Lapis Blue MCS ... body color exterior trim, chrome grille, painted roof Union Jack, Euro shelf and rear fog switch