Anyone want to guess what my spider-robot does?

[tim eh?]

no hints it's too easy...

http://www.bimmernut.com/forum/attachment.php?attachmentid=6735&stc=1&d=1241300094

[632 Regal]

Knocks out high frequency for your boom box?

[tim eh?]

Knocks out high frequency for your boom box?

dammit that was too easy. ok bonus points if you can guess the xover point. (-6dB)
http://www.bimmernut.com/forum/attachment.php?attachmentid=6738&stc=1&d=1241303063

these things are so cool, i am lovin' this stereo install check out what's next...

http://www.bimmernut.com/forum/attachment.php?attachmentid=6737&stc=1&d=1241303063

while i was there i secured the factory amp guts properly, looks even better with the trunk panel back on.
http://www.bimmernut.com/forum/attachment.php?attachmentid=6739&stc=1&d=1241303063

[632 Regal]

Looks like a pretty cool setup, So this is just to feed the amp for the boom box?

[tim eh?]

Yeah so actually you were really only 'close enough'.

The spider robot actually kills low frequencies going to the factory crossovers.
One capacitor for each speaker group.

The other thing is what will knock out the high frequencies going to the sub - it will sit (somewhere) between the power amp (that you haven't seen yet)and the sub.

[632 Regal]

well my son shed no light on the spider, I thought sound system as there was no other purpose for it so I guessed. had this been any other forum I would have had no clue.

The MFD does nothing for me but my son recognized it but still had no clue.

What are you doing with all this so I can somewhat try to understand it?


Yeah so actually you were really only 'close enough'.

The spider robot actually kills low frequencies going to the factory crossovers.
One capacitor for each speaker group.

The other thing is what will knock out the high frequencies going to the sub - it will sit (somewhere) between the power amp (that you haven't seen yet)and the sub.

[tim eh?]

Yeah I shouldn't have given it to you, you were actually wrong:). kids won't know, they use active crossovers now - he'll have a better chance identifying an 8 track!

I'm installing a sub (u knew that...) these doodads I'm putting in are basically an extension of the crossover system I ripped out of the amp.

http://www.bimmernut.com/forum/attachment.php?attachmentid=6649&stc=1&d=1238283842http://www.bimmernut.com/forum/attachment.php?attachmentid=6648&stc=1&d=1238283446

See how it works? The coils block high frequencies and the capacitors block lows.

My new 'PAC's block the low frequencies to the factory speakers. This is for 2 good reasons.

1-Bass waves are what kill speakers. Those bitty 5.25 factory woofers (which are great spkrs btw) are trying to create soundwaves 3 metres long. Pop a cover off on the rears one day and put something bassy in - you can see they want to just about jump out of their mounts, while the tweeters barely move. So the more you increase power (ie with aftermarket amp) the more you have to cut the low frequencies to the factories - I noticed a lot of people have had the rear speakers blow (happened to me) after an a/m stereo install. Really it only affects the woofers as the other factory speakers already have the bass cut with the factory capacitors.

2-My subwoofer is going to be playing those low frequencies. If I left them in the factories too I would get a spike in low hz output. It's more complicated but basically you want all the bass in the sub or you are still limited in (quality) low hz output because of the factory woofers. Basically I'd rather listen to bass from an 8" vifa without the 5.25" nokias trying to keep up.

The really cool subwoofer crossover cuts high frequencies to the sub. Same reason, the factory mids and tweeters will do a better job with those frequencies.

The goal of a good audio system is first to get a good even flat response at all levels and THEN you can crank the bass if you want to.



*- here is the theory... these are frequency response charts. The first one is the factory system (1 front 3-way group... 2-way works the same but is more demanding on the woofer, which is why they blow). Each speaker has its own range of frequencies to take care of. The second chart is what happens when you add a sub without filtering the factory system. The third one is with spider-robot added. With a nice flat (if i could draw) response like this you can pump up the volume and it will sound good. BTW- what is MFD?

[BMWDriver]

MFD = µfd = Microfarad, the capacitor's rating.

Can't wait to see your sub.

[tim eh?]

MFD = µfd = Microfarad, the capacitor's rating.
oh ok I see where you got that from Jeff.




Can't wait to see your sub.

here it is (http://www.bimmernut.com/forum/attachment.php?attachmentid=6663&stc=1&d=1238618175):D

here's the amp...
http://www.bimmernut.com/forum/attachment.php?attachmentid=6741&stc=1&d=1241385885

don't hold your breath tho... car looks like this at the moment...
http://www.bimmernut.com/forum/attachment.php?attachmentid=6742&stc=1&d=1241385885
sunroof drains all screwed up again wtf. gives me a chance to paint the floor with POR-15 this time... still waiting for heater core pipe...

[BMWDriver]

So, how many watts? What brand? If I recall, you said you had two 8 inch Vifas. Are you using both? Are you boxing it?

[tim eh?]

So, how many watts? What brand? If I recall, you said you had two 8 inch Vifas. Are you using both? Are you boxing it?

"560 watts" JVC LOL, I hope it still works. = 200W rms but since the speaker is 8ohms it will run at 100W. I'm using a single 8" home theatre woofer, it's not even a subwoofer really and I am building a box for it, maybe porting into the cabin and crossing over at a ridiculous 125 hz. I would suggest something more traditonal for folks at home, I'm being a bit silly but I am in love with this speaker and I have watts to burn. This could end up not working, it depends on cabin acoustics, but if it works like I think it should I'll be pretty pleased. Factories still sound pretty good with the bass cut out... maybe it's the wet carpet... tbc...

[pingu]

Nice work! Just thought I'd mention that strictly speaking, the inductors (i.e. the coils of copper wire) should be kept separated from each other.

Normally, you'd keep the coils about 3 diameters spaced apart from each other. Or, each coil is arranged orthogonally (i.e. one along the hardboard, one across and one up). Also, you should try to keep the coils away from the steel bodywork (or the bodywork will act as a core and will change the inductance of the coils). Did you use brass bolts to hold the coils down to the wooden board?

If the coils aren't orthogonal, or aren't kept a reasonable distance (a few inches) away from the steel bodywork then the coils interact with each other (this is known as 'mutual inductance' and is the principle underlying a transformer) and slightly degrade performance. But any theoretical degradation may not actually be enough to be noticeable - certainly no need for you to rebuild but something to remember if ever you do this again.

Anyway, well done!

[tim eh?]

I was kind of wondering about that - I was thinking of double-coiled guitar pickups, but the coils are placed close to each other inside the factory amp so I didn't worry.



Did you use brass bolts to hold the coils down to the wooden board?

no

Well it is sounding pretty good though, sounds very clean to my ears I am happy.
Thanks very much for that info!

[BMWDriver]

I've got a 40W woofer with a 4 inch 4 Ohm kicker by Labtec I'll be using. It's encased and drives an 8 inch membrane by compression. It really kicks bass big time. Do you think I might use the same capacitors and the woofer's crossover you have? I'm sure to go for a different amp. Although it looks like I'll have to use different capacitors since I have a 4 Ohm driver. Any suggestions or link for calculations?

I understand the Hz bandwidth phenomenon, but could you say why cutting off at 125Hz is "ridiculous"?

BTW, my fading and balance are not working too well after further testing. I have worked out why, and I will have to modify my board. However, I will modify it to accomodate the bass crossover on top of that.

Naturally, the bass crossover goes between the amp and the woofer.

[tim eh?]

Get the amp first. My amp (like most I think) has a low pass filter on it (80hz, which would be 40hz with my 8 ohm speaker so I don't use it) already - then you can get your bass blockers to match. 125hz is quite high compared to what most people use but I am not an authority on that. At a certain point (something like wavelength=4x space between yer ears) bass loses its audible directionality and below that is where subs are generally set to play.

The difference between 80hz and 125hz is about 5 white keys on a piano-> http://www.drewdaniels.com/FREQ.pdf
Notice the wavelength of the bottom A on a piano is 40 feet long and the top C is only 3 inches!

40W sub eh? ...careful with that... :D

So what's the deal with the balance/fade? ... is it the speaker grounds or something else?


*** - this site is handy... punch in your desired xover point and it will tell you which capacitors to get for your bass blockers. should be around 500MFD for 80hz.
http://www.diyaudioandvideo.com/Calculator/XOver/

[BMWDriver]

An overdue reply but...
This is the schematics of what goes on. There's the addition of resistors and capacitors between positive and negatives as you will see. Those are polarized capacitors btw.

I've only done the left channel to illustrate, and omitted the rest of the crossover for simplicity. Strange that the negatives and positives should be linked directly, but that's how it is. The resistors have a much higher Ohm value than the speakers though.

Where'd you get your capacitors? The highest I can get my hands on from Addison (as far as neutral ones) is 280µF.

[BMWDriver]

Hm. Looks like I'm wrong. This could be part of the crossover as well as a notch filter... albeit no inductors this time around. Mind you the capacitors throw me off a bit since they are polarized instead of the usual non-polarized you should use in a crossover.

Anyway, when I "fade" and "balance" the speakers, there is a dramatic loss of power. I wonder that the capacitors make up for it.

[tim eh?]

Hm. Looks like I'm wrong. This could be part of the crossover as well as a notch filter... albeit no inductors this time around. Mind you the capacitors throw me off a bit since they are polarized instead of the usual non-polarized you should use in a crossover.

Anyway, when I "fade" and "balance" the speakers, there is a dramatic loss of power. I wonder that the capacitors make up for it.



I would guess the circuit is designed to bleed a bit of the signal straight back to the ground depending on your fade setting and that the factory head is designed to work with this circuit (and the dashboard fader switch) but your a/m head doesn't work the same way ....because it was designed not by aliens but by real human beings! It would explain a lot, I could never figure out how the fading would work with only a single ground for each side. There is no purpose for a notch filter there... why would there be a notch filter anywhere? So anyway I've got good news and bad news... you don't need that s%!t, but you do need (4) new speaker grounds. :)

Wait... what side of the amplifier (i mean the amp inside the 'factory amplifier') were they on?

I bought the 4 bass blockers from 'juicy robot' on ebay.

http://stores.shop.ebay.ca/juicyrobot__W0QQ_armrsZ1

***-you should get the amp first, really you should.

[BMWDriver]

Yeah, I've got my eye on this Kenwood KAC-5203 for 90$ at Addison's. It drives 55W per channel, and cuts off at 80Hz if I want to drive a woofer with it, which I do. It can also do 150W for a woofer.

However, since I have a 40W speaker, I worry it may be too much power for it. Though it seems speakers have a higher tolerance than what they are rated as I have found out while shopping a bit for speakers.

Here's a link to the PDF :
Kenwood KAC-5203 (http://inform3.kenwoodusa.com/manuals%5CKAC-5203.pdf)

This circuit is right at the "entrance" of the amp.

[tim eh?]

don't worry about getting too powerful an amp unless you are going to turn it on with it set to 10 which would be very foolish with any amp. a more powerful amp ought to send a better (ie flatter) signal to the speaker than a weaker amp at the same volume. I'm guessing the 150hz is for if you run an 8ohm sub (at 75hz) ... you should look for 'bass blockers' with a cut of -6dB at 80hz with that amp or you will get spikes between 80 and 125 hz and things will start to buzz all over the place.

but are you sure it is a 40W sub? I don't really understand how they can assign a Watt rating to speakers but I think that is really weak, is it made of rice paper or something? i don't understand this at all, is it a computer speaker?


I've got a 40W woofer with a 4 inch 4 Ohm kicker by Labtec I'll be using. It's encased and drives an 8 inch membrane by compression.

anyway - that circuit is pre-amp and part of the whole setup you wanted to bypass. it is designed to let a tiny bit of the (line-level!) signal out from the factory head to be shorted directly to the grounds. 48ohm would hardly let anything through i don't think but you are running speaker-level signals through it so it won't work the same as with the factory head line-level signals.

easiest to remove trunk left side panel, back seat, rear of centre console, shifter panel and of course the stereo. 16 ga, about 25 feet ought to do...
this was the job that got me going towards the heater core.

[BMWDriver]

Well, an oversight on my part. Where and how can I hookup the woofer since, unfortunately, my HU only has 4 RCAs, none for the woofer specifically.

Either the amp of the HU is on, and no output through the RCA (I think...), or the HU amp is off and then the output only goes to the RCA and turns on the external amp.

Yeah, it was a Logitech Z-540, useless for the past few years. The driver has 4Ohm 40W stamped on it. And it really makes noise.

I think you read wrong. The Kenwood amp can cut at 80Hz (switch) and can give 150Watts if bridged.

[BMWDriver]

Right. Two amps.

[tim eh?]

Right. Two amps.

?


Well, an oversight on my part. Where and how can I hookup the woofer since, unfortunately, my HU only has 4 RCAs, none for the woofer specifically.

Either the amp of the HU is on, and no output through the RCA (I think...), or the HU amp is off and then the output only goes to the RCA and turns on the external amp.

Yeah, it was a Logitech Z-540, useless for the past few years. The driver has 4Ohm 40W stamped on it. And it really makes noise.

I think you read wrong. The Kenwood amp can cut at 80Hz (switch) and can give 150Watts if bridged.

the rcas should be active, i would use the rear outs - the good news is you can run the line same time as you do your grounds.

yes i read it wrong... 80 hz then.

[BMWDriver]

2 amps: some amplifiers have a pre-amp out to link up to a second amplifier. Polk Audio has some of those.

I'll test to see that there is something coming out of the RCAs then. Cross my fingers...

[tim eh?]

2 amps: some amplifiers have a pre-amp out to link up to a second amplifier. Polk Audio has some of those.

I'll test to see that there is something coming out of the RCAs then. Cross my fingers...

ok good luck that ought to work no problem.

i dunno about your speaker tho... audio isn't really the same deal in a car, it has to be way stronger than in a room with drywall and 90' angles everywhere. that vifa i am putting in is a pretty serious speaker made in denmark... good for a very very big room... massive overkill for an apartment. maybe your sub can handle a car... ? i'm not saying don't do it - noone will ever know unless you try it...

*- btw here are my speaker specs more or less, it is a similar model.
http://www.oregondv.com/Vifa_Speakers_P21WO-20-08.htm

[BMWDriver]

Naturaly, if the woofer don't do, I'll go with a different one. Right now I'm saving on the cash and using something that was useless. The Z-540 Logitech really lacked in mids, and the bass was too much even at the lowest volume setup, for an appartment that is. No big loss there.

Well, I have most of the necessary gear and ran some wires from front to under the rear seat. The rest will wait.

[tim eh?]

cool well if you don't care about maybe killing it anyway it's worth a try - speakers are like automatic transmissions, you never know how much abuse they can take until you actually give it to 'em but i read up on it it runs on 20W.

i am in no hurry for the sub either, the am head/factory speakers setup sounds pretty good it is easy to procrastinate... i'm not sure i'd even put one in if i didn't already have an amp already that matched the trunk interior and with all the power wires already there i kind of feel like i have to :D.