modding 4.1 amplifier

[lovetomod]

hello all ! I have done a stupid thing - while modding my amp from my 4.1 set , i forgot to note the order of the voltage regulators . they are the ones on the speaker terminal board . on the board they are, U2 U3 U4 .( near the red coil ) problem is one of the three is a negative regulator , not a positive - if anyone could look at theirs i would be grateful ! the three reg's are : 7815CT - :7915CT is the negative one . they are held on to the back cover of the sub with screw clips , if someone could please look and tell me which location , U2 U3 U4 the negative one goes to i would be very grateful for the assistance and if possible will help them in the future ! you guys are going to like what i have done to this thing ,you will see the end results soon , I just made a careless mistake removing the reg's . CHEERS ! patrick

[craftsman]

I just took a part my V.2-400 and the placement of the regulators are as follows:

Speaker 7915 7815 7815 AC

Connectors Line

Hopefully, you can put your BASH unit back together. I too have been working on some modifications - mostly adding decoupling Caps to almost all of the Op-Amps (in the BASH and the CP-1) as well as increasing the size of a couple of the Caps next to the three voltage regulators... I'm planning on increasing the power cables to the amp modules from a single 18 gauge wire to three 16 gauge wires (grouping the fronts, the rears, and the sub into three groups), replacing the dental floss speaker wires to the satellites with some 16 gauge wire, and replacing the wire inside of the satellites with thicker wire. What I would like to do is to add more caps to the supply lines to the amps and try to isolate them more from each other.

I'm very interested to see what your modifications are so that we can compare notes.

Thanks

[lovetomod]

Outstanding sir !!! thank you for telling me the placement of the regulators !!! i was 80% sure that was the order but didnt want to damage this awesome system! I was getting alot of static on all 4 channels . i was familiar with the heating of a couple resistors , but they were not open so i chose not to replace them at this time. however i noticed a kind of hardened black goo around 5 capacitors , the guru at my local electronics warehouse suggested that it could be leakage , or some adhesive they used to stabilize the caps - i figured what the heck , i will replace them. guess what.....PERFECT !!! absolutely PERFECT ! no static ! these things sound brand new - and these are about 3 years old . total cost was $9.00 for the 5 caps. the two caps on the power supply i upgraded to 125 volt from 63 volt, figuring they were taking alot of abuse from being the main reservoir caps . (or are they covering the demand the switch places on the supply ?) i dont know. anyway they wouldnt fit on the board, so i made some extensions for them. the whole enchilada WAS mounted on a 12"x8"x1/4" plexiglass board (i will explain later ). the regulators are now mated to a cpu heatsink - i haven't finished the enclosure yet but it will have a small 12V dc fan running off an add on 12V regulator , i had one problem though . after i replaced the caps ,to test the amp i had it spread out on my workbench , worked great - no static . so i mounted it on the plexiglass board , only to discover it had a transient static ( when the music program got stronger the static did as well- i was using unaccompanied cello to test with as well as a tone generator.) after removing the ground straps i placed between all boards except the amp itself , and removing those 1 by 1. there was no change .i went back to the drawing board. it turns out that the switch and power supply CANNOT be too close to the amp , i had them within less than a 1/4" I have since rearranged things a bit , and everything is PERFECT ! i wish i had a few pics to post right now , but i will have a few in the next couple of days. the other mods required to do what i have done are : removed the regulators from the output board and remotely mounted them .replaced the speaker output cable to something longer and larger ( 18 gauge ) the ribbon cable had to be extended , i chopped a floppy drive cable - and reused the connectors. the 5 pin cable from the power supply to the output board needed to be replaced as well as the 5 pin to the board with the large yellow coil - i removed the connectors , prefering to hardwire things. i also added a connector near the surround outputs to head to the sub box which i sealed with 1/4" plexiglass(i will replace this with 3/4 particle board soon ) as a side note - without the amp in the sub box i noticed that the port tuning is off a bit - i realised slightly deeper bass extension , but it was boomy. i placed a vinyl disney movie case from a vhs tape inside - just stuck it in to replace the lost volume and to hear the difference - it got the port tuning pretty darn close . all in all this has worked out great ! i still have static on the surround knob only if i turn it too fast but i will remedy that next. i am interested to hear what you are doing !!! also the data sheet for the 7915 says that if it is more than 3 inches away from source it needs a support cap , it does not.

again thank you for your help !!!!! there are more details to this project , but thats the gist of it off the top of my head. again THANK YOU for your help , you rock ! patrick.

[craftsman]

Wonderful. I do hope that everything goes back okay!

I've noticed that your modifications are a heck of a lot more extensive than mine. I'm what you might call a classic tweaker - nothing too far out but just enough so that everything fits back into the box.

I've looked at a few websites and reviews on these Promedias and there seems to be a couple of common issues:

1. The external speaker wire is like dental floss.

2. The subwoofer is too boomy and the bass is not very tight.

3. The horns in the satellites are too sharp.

4. Background noise on the rear channels.

Here's my thoughts on each:

1. Easily replaced. I picked up some metal 1/8" mono plugs and I'm going to replace the dental floss with the thickest wire I can get into the jack (which is approx 6mm in diameter). I'm probably looking at 16 gauge and if I'm lucky 14 gauge wire.

2. According to a lot of websites on speaker design, a boomy speaker is usually caused by the cabinet not being solid enough and having echos. So, I'm thinking of adding some sound deadening material to the inside of the subwoofer cabinet. Dynamat, SecondSkin,.... All of them seem to be good products. As for the tight bass, sometimes that is caused by not having enough reserve current for the AMP to drive the subwoofers - hence, my wanting to add some more capacitance to the AMP supply side of things.

3. Sharp horns could be caused by the cabinet of the satellites not being dense enough (like the problem in 2). I figure if I add the sound deadening material to the cabinet of the satellite, it should make the cabinet more dense and decrease any standing waves coming from the cabinet.

4. This is harder to trace. However, I do believe that the addition of the decoupling capacitors should reduce the noice of the circuit. Also, the thin speaker cable may also have something to do with it.

The resistors that I mentioned that I had replaced - I figured that I should replace them before they opened up since I could measure the value of them now rather than later. From the size of them I guessed that they were 1 Watt ones so I replaced them with 1 Watt ones... Of course, now I was able to find some 2 Watt ones! Purchased a couple of those just in case!

Have you thought of using audio grade capacitors? I've been reading a lot about audio grade capacitors and it seems that they make a difference (of course for the price of them they should). According to what I understand, the audio stuff is suppose to be able to have less noise and have a quicker reaction time so that the sound is clearer and smoother. Of course, having enough reserve capacitance in the first place should go a long way to get a smoother sound. Have you thought of replacing those capacitors that you replaced with large ones - not just higher voltage but more capacitance?

If you really want to reduce the noise between the AMPs and the switch, you can always mount a piece of grounded metal between the two sections - that should block out all of the miscellaneous RFI and EMI floating around.

As far as covering up the hole in the subwoofer, you should try using MDF instead of particle board. MDF is a lot denser, easier to work with, and easier to finish. You could also place some fiberglass inside the sub to reduce the standing waves inside - less boominess.

Richard

[007]

nice work, i'll have to come back to this thread when my 4.1's start to fade.

[InnovaZero]

Interesting, I'd love to see how this comes up. Couple things however, the sats thesmelves already have absorbing materal in them. Also the reason for it being sharp, two reasons:

1. At the time, computer users wern't used to decent tweeters, being near-field the horns made things more focused. Many previous Klipsch users, as well as people who have had experience with HT speakers, accually miss the old 4.1/2.1 sound. (Although the Ultra sats are smoother)

2. The subwoofer when placed prop. is far from boomy, infact its blending/tightness is damn good by MM standards. The problem however, which ask anyone who has been following the Promedias for years, is that placement with this thing is crazy challenging,a feat few often find. Thats not to say it doesn't sound good, however what people instead just stick too is the wall (SPL, little more punch) or in the open (Tightness, detail).

[craftsman]

Oh I realize that the sats have absorbing material in them already - I took them apart the first day I got them. However, according to a number of speaker enclosure theories that I have read (of course they could be wrong) but the best cabinets are usually the ones that sound solid when tapped. The sats do have a more hollow sound. So, adding more density to the walls of the sat should reduce the hollowness and hopefully the vibrations in the cabinet which may be causing some interference.

As far as the tweeters are concerned, I was relating the issues that other users have found. I must agree with you that the better quality Klipsch tweeters are probably the cause for the misguided judgement. I do believe that the quality of almost any product can be improved - maybe not a shiny bar of gold. My goal is to get that old 4.1 sound sounding smoother and cleaner.

As for the subs, as with almost any speakers placement is one of the most important things; yet, overlooked. But once again, I do find that the enclosure may need to be beefed up according to speaker enclosure theory.

What I find nice about this thread is that people are looking, reading, and hopefully learning (me included) about their purchase. After all, if we weren't concerned about sound quality from our ProMedia's why the heck did we spend all of that money? The more feedback and the more experience we can post here the better the Promedia community will be come!

[InnovaZero]

Ohh I agree completely. The sats thing is worth a try, however as we all know..you don't want to stuff it too much.

However stuffing the sub, I doubt will do anything, and might add more heat to the amp. The biggest (and IMHO as far *** MM subs go) flaw with the 4.1 sub is that it was underported, the port is a tad too small, or if you want to look at it anoher way, not enough flare to the edge of the ports. Then again, increasing port size may have made it boomy, but who knows. However as we all know with the HT-like Ultra subwoofer, those slot ports go a long way compared to traditional rounded ports.

I would like to see how the stuffing goes though, doesn't hurt to try.

[craftsman]

Port modification may be getting a little past my comfort zone at this moment. At least with the modifications I'm proposing, I could always rip them out if I don't like them. Then again, I would always buy a dead subwoofer and modify that....

[lovetomod]

hey guys , sorry i've been lax in my responses, work can be hell ya know. anyways , i wonder if it was misundrestood what i said about the port tuning being off a bit. what i was trying to convey was that after removing the amp , the enclosure gained volume. throwing the port tuning off. i am not inclined to change the port size to fix the added volume - quite the opposite, i would rather return the enclosure volume to what it was before. if i wanted to play with port tunings i would design a new enclosure. it would be interesting though to see how these speakers would work in a sealed box of the correct volume. i know there would be about a 3 DB drop in output, but a more linear,and deeper bass extension. lets not forget the crossover settings for the sats though....too much headache for the moment.

richard , you have me wanting more details on the decoupling caps. please, do tell !

also i think your idea on bigger power supply caps is a viable one .i am looking at the boards pretty close.... what benefit do you see from increasing the regulators caps ? i thought they were mainly providing juice to the opamps ? i dont know - just asking

as far as the stuffing in the enclosures goes...i think there will be little effect on the sats- they already have some and they are not playing alot of bass. the sub on the other hand will show a marked difference with stuffing. heres something i remember from my days of building isobaric and other types of enclosures with 15 and 18" woofers. when i added stuffing i heard less resonance in the boxes, and the box SOUNDED bigger.but they were ported boxes and the sound was alot less tight. i believe (dont quote me on this ) that when adding stuffing , you effectively add 1/2 cubic foot of volume to the box. you guys can try it , but i think you will be happier with the sound quality WITHOUT the stuffing.(you are limited by the crossover points-unless you want to change them , and the sats ability to play lower-stronger midbass with authority.) back when i built stuff i built it for maximum SPL output. sound musicality was a second consideration in car stereo competition at the time. i think to play around with the crossover points and sub enclosure dynamics may detract from the EXCELLENT work KLIPSCH has done designing the promedias. ( it just so happens that the company that builds their amps missed on some high stress components ) did i just say that ?

HEHEHE - dont blame klipsch 100%

my experience on ports..........as far as round ports not having enough flare , if you do not hear any port noise the flare is sufficient. the difference between slotted enclosures and round ported enclosures is nill. i have built both , including transmission lines .the tuning is what matters not the style of vent. ( though there are packaging benefits to both designs )

IMHO

i really love the promedia 4.1's , i wouldn't have any other speakers for my pc. ( we will not go into what high end home audio gear i own at this time) but i spend about 80% of my leisure time listening to music and viewing dvd's with my 4.1's. and i love them. alot ! ( the only exception i have to klipsch is their GMX stuff - thats their punishment for our heresy ) LOL !!

i hope this post doesn't come off as snotty , i am very tired. i am just trying to relay my thoughts. there are a few more minor mods i have done to my amp - i will have pics tomorrow night for yall. god willing and the creek don't rise

support klipsch or we will all have logitech crap , or altec lansing's crap ,or that other piece of crap.....or $2000 5.1 setups that do the same thing .....i digress. G'NIGHT !

[craftsman]

I know about work being hell - my job takes me to all parts of the States (I'm in Corpus Christi, right now) - and it's tough being away from those speakers (don't have a wife nor a girlfriend so I have to miss something).

I've been looking at the subwoofer cabinet construction and while I'm not an expert I do believe that while it may not need any stuffing, it may be able to use more stiffness and maybe more density in the cabinet itself. What do I base these observations on? Well, most high end cabinets I have seen as well as most plans for subwoofers I have seen seem to say that a stiffer cabinet is better and the thicker the cabinet the better. Since we can't make the cabinet any thicker without rebuilding the cabinet, we might we able to make it seem thicker with some sound deadening mats....

As far as the decoupling caps go, the theory is really very simple. Noise from the power lines will cause noise else where as well as wasting power as the Op-Amps will try to amplify the noise as well - we might not hear it since it's above 20 KHz. So, if you look at proper Op-Amp design, almost all designs call for the Op-Amps to be decoupled - a small non-polar (ceramic) capacitor connected between V and V- to remove the noise from the power lines before it hits the Op-Amps. Since all of the components in the amp can create noise, all of the Op-Amps should be decoupled. The smaller the value of the capacitor the higher the frequency it will filter out.

As far as the power supply caps go, I remember reading on a couple web sites about headphone amps and how most op-amps in these things don't have enough capacitance. On an Archos MP3 player that I have, it was recommend that I add more capacitance so that it will round out the poor bass response. And you know what, they were right - it did not have enough reserve power to drive the headphones with enough bass. On a set of noise reduction headphones, I did the same thing and found that quality of the sound was much fuller and the bass was much deeper and smoother.

Unfortunately, I got into the habit of thinking that every Op-Amp needed more capacitance so when I got these v.2-400 (brought them used off of e-bay a few weeks ago), one of the first things I did (after I verified that it worked) was to add the capacitors. So, I can really say for sure that there was an improvement but according to my previous experience, the sound should be better.... I believe that one of the big things about adding capacitance is the possibility of having enough power for the Op-Amps when there is a lot of load - such as repeated lows.

I don't think that you are being snotty at all. I do believe that the manufacturer's R&D engineers start off by trying their best to design the best equipment. However, due to cost cutting and trying to reduce the price of each unit to a level so that they will sell, corners are sometimes cut - thinner wires, poor connectors, thinner cabinets - by the production engineers. After all, we all know the boys (and gals) at the Klipsch R&D lab do good work. The only question is what was done to cut the cost so that the unit is affordable. What I want to do is to reverse some of these changes. I have even toyed with the idea of replacing the Op-Amps themselves with other higher price units because other articles I have read said that they are smoother and have a much better tone. At the same time, I've found some postings on the news groups stating that the current Op-Amps while cheap are pretty good. So, I've put that idea on hold, for now.

Richard

[Kyle]

I think what made the ultra sub so much better than its counterpart was the increase in voice coil and cabinet volume which allowed for a lower tuning fq. There was also definitely something wrong with the older port. The 5.1 more so than the 4.1 and 2.1 But the 5.1 THX's had some serious port noise issues when running hot (loud).

[MD1032]

I seriously believe the 4.1's subwoofer is an excellent sub, but its design is quite flawed. It's way too boomy thanks to the port noise, and the tuning kinda sucks.

Anyway, my idea: Why not just seal the dang thing? No more port to deal with. Sure, it's not as efficient, but who knows, it might get tight as heck.

[craftsman]

If I remember the information that I've read on the 'net on subwoofer construction correctly, increasing the quality of the cabinet will seem like an increase in the volume. According to the sound deadening mat people, deadening the cabinet will make it seem like an increase in volume of the cabinet. From what I read on the news groups, they seem to agree with the sound deadening mat people.

[craftsman]

If you want to try to seal the port thing, you can try it by just clogging the port up with something - sure it won't be perfect but you can see if it improves things.

[bagga]

i just read this entire thread and i'm amazed!! it's very cool you people are modding your klipsch MM systems! i think i have some really usefull information to add too.

regarding the dreaded "bOOmyness", i believe this is merely the fault of the extremely high cut-off or crossover in the sub! i'm just guestimating but i would say the crossover is around 250hz, or the low end of a guys voice!! that's waaaay high for a sub. after all, subs should only be playing the "sub" end of the sound right?

try this out: play some music that has a pretty full range of frequency in it. rock, jazz, rap, drum n bass, whatever. when it's playing disconnect the satellites from the sub and listen, you can almost hear the entire song through the sub. this is what's causing the BOOMy, muddyness! since the sub is playing the midrange too, it can't concentrate on the tight, deep punch we are all looking for! get it??

so i think all we need to do is figure out how to change the crossover so that the cut off is either variable, which would be really nice, or just modify what ever is setting the current 250hz cutoff so that it is lower, around say 120 hz.

i am 99% sure this will cure the bOOmyness we're up against. for an even easier example try to find a sub that does have a "variable crossover", and while there's music playing try adjusting the crossover as high as it goes. you will definitely notice that the music starts sound a LOT "muddier", less precise, and down right sloppier. as you turn the crossover down to around 100 - 70 hz, the sound get's nice and punchy, very clear, and sounds deep and tight!

i'm going to look around on the great wide intarweb for information on sub crossovers, i'll post again when i find stuff! Happy Modding ~zeric~

[craftsman]

Welcome to the thread! Any contribution is a good contribution!

You might be right about the crossover level. If you look in the subwoofer unit, you will notice that the subs are connected to the last "amp" module (and each amp module appears to be the same). The amp modules are "controlled" by a set of jumpers located next to the ribbon cable that carries the signal.

So, there are basically two options for adding/changing the crossover -

1. modify the existing circuit.

2. add to the exiting circuit.

If we modify the existing circuit, we would have to trace the signal back into the board and add/modify components on the board. Not the easiest thing to do!

If we add to the existing circuit, we can just add a low pass filter before the subs - simpler. The only issue is that the level of power coming out of the subs might be reduced....

[craftsman]

I just got a CP-1 off of ebay with a bunch of speakers (the satellites with the new crossovers!) so I can convert my v.2-400 to Promedia 4.1!

After using the new CP-1, I noticed lots of noise coming from the volume control, subwoofer, and surround knobs. After much additional research, I came across a spray from the people at CAIG - Cailube MCL - to "replenish & lubricate faders, switches, potentiometers, and other sliding surfaces". It seems that just cleaning the potentiometer will wash away all of the lubrication. This stuff is suppose to put it back. According to the postings I've read, a lot of the professionals use it for their industrial mixers.

After using the stuff, I noticed that controls were smoother than before and after two or three applications, the static was gone. Also, I used this stuff on the controls I treated with alcohol before, and the controls turned smoother than before.

Of course, I'll have to wait a couple of weeks before I can say for a fact that the stuff is actually any good.

At least, I didn't follow some of the advice out there to use WD-40!

[craftsman]

As a follow-up to the volume control static issue - it's been a few days and the volume, subwoofer, and surround controls are sssmmmmmoooooooottttttttthhhhhhhhhhhhh and free of static. So, at least for a few days, Cailube MCL is the answer!

A follow-up to follow in a week or so.

[craftsman]

The controls work like a charm - Definitely recommended!