Upgrading the JBL-S26 Crossover (long)

Discussion in 'Speakers' started by dean_g, May 15, 2003.

  1. dean_g

    dean_g Agent

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    Well, I suppose the thread title could have also been called 'LeMarcus at the mercy of a two-channel loon".

    I wanted to put this post in the DIY section -- but it appears it's mostly subwoofer related, and so I decided just to stick it in here figuring it would get more exposure anyways.

    I work with LaMarcus, or "Marcus" as I know him. We cross paths on the weekends as I am heading out the door and he's heading in. I'm pretty much a solder slinger, and since the weekends can be kind of slow -- I'll usually bring in something related to my latest project to help keep me busy. Marcus noticed my newly rebuilt Dahlquist DQ-10 crossovers sitting on the desk, and the next thing you know -- I'm toting one of his JBL S26's home for a little experimentation. Trusting soul isn't he?

    A little about myself: I'm two-channel only. My system consists of a pair of Klipsch RF-7's, Quicksilver M-60 mono-blocks (parallel push-push pull, ultralinear EL-34 tube amps), Cary SLP-94 tube preamp, and Sony 9000ES DVD/CD/SACD player. I have another system, but it changes so often it's not worth going into. It's the "test" system -- the one that is most subject to my tortures.

    I would do multi-channel if I could afford it. Maybe someday. Right now, I'm happy squeezing as much out of two channel as possible. To do multi-channel at the level of performance my 2-channel system has -- I would go bankrupt.

    I also like vintage gear. You know, the stuff you wanted while you were in high school -- but there was simply no way you could afford it.

    One of my favorite all time speakers is the Dahlquist DQ-10. I have just finished restoring my third set. The first set was hell -- because I knew what I wanted to do, but had no skill-sets for doing it. I spent a month reading about circuits, and studying the crossover boards. It is without a doubt one of the strangest crossovers ever put on a board. More time was spent learning how to solder. At some point, it all clicked -- and I got to work. I took them down to the last screw and built them back up. Surrounds, crossovers, wiring, wood work -- every part was restored or replaced.

    Having been around the DQ-10 most of my life, I was very familiar with the sonic signature, and the thing that struck and startled me -- was how much smoother and refined mine sounded than the stock rendering. I had chosen the RelCap Multi-Cap PPMFX metallized polypropylene capacitors to replace the worn out mylars on the stock boards -- not because I thought they would improve the sound all that much, but simply because they would fit on the boards the best. The experience was quite a revelation.

    This led to quite a bit of research on the parts themselves, and of course more experimentation. Insanity set in and I decided to rebuild the boards in my RF-7's -- a speaker I was already happy with. When I pulled the original boards out, which had parts mounted on a PCB -- I knew there was no way I was going to get what I wanted to use on them. So, I built new ones.

    http://forums.klipsch.com/idealbb/do...-02E02476A8B7}

    Again, easily heard improvement in every area: Tighter bass, better retrieval of ambiant information, no grain, sparkly treble, decay on the cymbals, etc. Of course, these boards were near cost no object boards.

    Next, I took on my Dad's old JBL Aquarius S109's -- which had been sitting in storage for 10 years. I pulled them out and gave them the complete workover. Same result. Almost got to see my old man cry.

    So -- now I'm a believer. Take almost any commercial speaker, yank the crap -- and you are going to get a much better speaker for very little investment.

    What are some objections to this line of thinking?

    You didn't make them "better", you just made them "different".

    A valid statement in part. Yes, they become "different". However, there is not a change in signature. They don't take on a totally "new" sound. There is a slight shift in signature because of the additional clarity and dynamics. A welcome trade off.

    The engineers know what they are doing, and that speaker was designed to sound a certain way. The parts chosen contribute to that "sound".

    This is actually true, and why modding can be dangerous. It can be hit and miss. However, my personal experience so far has shown improvement each time I've done it. The speaker sounds cleaner, and can play louder before distortion artifacts draw attention to themselves.

    If it could have been done better -- it would have been.

    This one connects to the objection before it. Something to keep mind is that the best engineering department is constrained by the marketing department, heh? Hey man, it's all about demographics, price points, WAF, etc. These folks know you just sunk $3000 - $4000 on your big screen, and you're scraping together every last cent you can find for the sound system. Trust me on this -- corner cutting is the name of the game in most consumer mass market products.

    Let me show you:

    The JBL S26

    Not a bad sounding speaker. Quite good actually considering its size. I'm kind of old school. I like bigger drivers, and the more the better. Large drivers have less IM distortion at any given volume. The JBL S26 6.5" woofers look itty bitty to me.

    I pull one out of the cabinet and I'm surprised by the weight. JBL makes nice drivers. The driver exudes quality. Nice cast frame, well made through and through. The tweeter is sweet too -- I dig the phase plug. So, this is where the money went. This is good -- because crossover components are much cheaper than good drivers. The cabinet material is partical board, though the fit and finish is very good.

    So, what's left?

    [​IMG]

    What you are looking at are the parts I replaced from the PCB crossover I just rebuilt for Marcus. If you know something about crossovers, then you'll notice there are no inductors. I do not mess with inductors. The combination of mH and DCR are critical in relationship to the drivers. If I were completely rebuilding these boards from scratch, and not using the original PCBs, I would probably replace the inductor for the woofer with a 14AWG Solen Perfect Lay. Besides, this is primarily a HT system with an SVS sub bringing up the bottom -- so we can let this go.

    At any rate, what do we know about the parts in the picture? Well, we have two electrolytic capacitors, two cement resistors, and two 'do drop in' bypass caps (there is only one in the picture because the other one is MIA in my work room [​IMG]

    Total cost of these parts (retail mind you)?

    electolytic #1.....40 cents
    electrolyic #2.....45 cents
    resistor #1........39 cents
    resistor #2........39 cents
    bypass cap #1......11 cents
    bypass cap #2......11 cents

    $1.85

    There are two inductors, each costing about $2. Throw in the PCB and the wires -- and you have a board that's worth less than $10.00 Don't laugh, even you guys with the high priced stuff might be surprised to find out what's in your speakers. I can safely bet they're not film and foils [​IMG]

    End Result

    [​IMG]

    The picture shows the completed board with two of the old parts for scale. I had really wanted to use Audience Auricaps, but they are kind of fat, and there was simply not enough room on the board to fit them. I consider the Auricap the best metallized polypropylene there is, but it was apparent I was going to have to use something different. I had to find a decent metallized polypropylene that would fit.

    Bottom of the board -- big cap for scale.

    [​IMG]

    I was also somewhat indecisive as what to do about the small bypass caps. I'm not a big advocate of the principle. The idea behind it is to run a very good quality, small value, high voltage cap -- in parallel with a low quality, large value cap. In theory, the signal will pick up the signature of the high value, high quality cap, and mask the sub-par signature of the low quality cap. I say use the right cap to begin with -- and you don't have to deal with the issue. Many people do not agree with me. Many people actually prefer the sound of bypassing, and reason that it is not necessary to spend the money on a large value quality cap if you can get the same signature with bypassing. Since I'm basically a hard head, I'm not about to budge on this -- even though I have no experience with bypassing -- until now. [​IMG]

    JBL boxed me in. The PCB is designed for the bypass caps, and I can't use the big caps because of the space limitation on the board.

    I decide that maybe Marcus can have his cake and eat it too. If bypassing really works (and JBL certainly seems to think so, since they employed the principle in an attempt to "bypass" the electrolytics)-- then I'll take it to the highest level possible.

    Once I find the polypros I know will fit -- I then order a batch of the AudioCap Theta film and foils. These are considered by many (including myself) to be the best caps on the planet. They are expensive, but the bypass values are small enough, that in conjuction with the polypros -- I was able to keep the cost at about the same as the Auricaps would have cost without the bypass caps. If the principle really works -- I will have been schooled by JBL, and Marcus will have some dyamite sounding monitors.

    Also notice in the pic that I like hot glue. I like it a lot. I damp the crossover parts with it as much as possible without inhibiting heat dissipation. The inside of a speaker box is a violent place.

    The Cabinet

    Worth doing anything here? You bet!

    I talked Marcus into the Deflex Panel mod.

    Deflex is the bomb. It's simply the best single tweak you can do to a speaker. I'm serious -- it's that good. TV should line one of his SVS subs with this stuff -- I think it would blow him away.

    JBL makes you pay the price for getting into their speakers. I reach in and pull out what I believe to be the standard fare -- and end up with fiberglass all over me. I may charge Marcus extra for "pain and suffering".

    At any rate, there is plenty of stuff on the net about Deflex, and it's the last thing I have to do before I put the speaker back together. Looks like total time spent on the speaker mod will come in at about an hour and half. Marcus will have around $50 into each speaker.

    I will not be making any comments regarding my impressions relating to the sound of the modded S26 until after Marcus has had an opportunity to assess for himself what he thinks. I did tell him that if he doesn't like it -- I will change it back for free (which means I'm out $1.85 [​IMG]

    Dean
     
  2. David_Stein

    David_Stein Second Unit

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    well, this thread certainly has me interested in hearing how well the mods sound...
     
  3. David Lawson

    David Lawson Screenwriter

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    It's a shame he didn't host the meet before these mods were done. I would have been really curious to hear a before-and-after comparison. I guess we'll just have to be content with him raving about how much better everything sounds now. [​IMG]
     
  4. MikeMcGrew

    MikeMcGrew Stunt Coordinator

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    Tell the truth, are you going to bill him for the time it took you to write this thread??? [​IMG] And, can you do this to mine??? [​IMG] MM
     
  5. LaMarcus

    LaMarcus Screenwriter

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    I tell ya, Dean knows his stuff. He's a network engineer here at work, and he's always into something dealing with electronics. Be it a router, switch, server or some speakers Dean is the man. He tells me about all the stuff he's doing to these speakers, 7 times out of 10 it just shoot right over my head. I just trust his judgment. But what really intrigued me to let him go ahead and do the mod is when I researched the Delfex pads like he suggested, from the sound graphs I could see the differences and I wanted to hear them.

    David, I guess it would have been nice to hear what my system sounded like before the mods, but I guess I just want my sound to be all that it can be by the time we have our next meet at my house.
    [​IMG]
     
  6. dean_g

    dean_g Agent

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    I wish I was half as knowledgeable as you think I am. I'm just a very small fish in really big pond. I'm still pretty much a "wanna be". I can trace a PCB, make a schematic, copy a circuit, and for the most part not screw anything up. I have decent soldering skills, just take my time and pay attention to detail. Other than -- I'm dangerous as hell.[​IMG]

    I do read a lot, and just like you -- most of it goes right over my head. I gleen what I can.

    I do have a cap tester and multimeter, and test the parts before I put them in. I also compare the values of the old parts to the new. Most OEM parts are + or - 10%, and though that doesn't sound like much -- it can be huge swing between parts sometimes. My caps are + or - 5%, and the Mills resistors I use are + or - 1%. So, in the end, there is less variance between speakers.

    Crossovers are complex, or rather -- speaker systems in general. The math behind it all gives me chest pains. This is where I'm at right now -- really trying to understand what goes on in these circuits in relationship to the box and drivers that are used. I know people that can do this crap in their heads -- it's frightening.

    I have good mentoring at the Klipsch 2-channel Forum. You might want to come over and check it out. Some of those guys are giants.

    Actually, most of you guys amaze me. I look at the front of a HT receiver and it looks like the dash of the space shuttle. My amps have a power switch, my preamp has selector switch and a volume control, and hell, half the time I get those two knobs confused.[​IMG]

    I got the S26 finished last night. I'm pretty sure I got stoned out of mind putting the Deflex Pad in with the contact cement. Yeesh -- wicked stuff. I waited about an hour and put her back together and fired her up. I thought it sounded...oops...I forgot -- can't say anything until Marcus checks it out.[​IMG]
     
  7. LaMarcus

    LaMarcus Screenwriter

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    OH MY GOD!!! This thing sounds amazing, the clarity is unbelievable!! I can't believe it, I didn't really know what to expect, so I don't know if not expecting has helped or not.

    I hear the most difference in the high end, the best way I can think to describe it is it sounds spacious. I mean the sound from that speaker sounds wider than the speaker that is not modified. I will stress the word clearer, the other speaker sounds muddy or muffled I should say, but the modified speaker sounds very, very clear. The tweeter has come alive!
    I will say that the bass is not as deep sounding as the regular speaker (but just a little). Maybe jbl made these speakers muffled on purpose to make them sound like they have bass response. But I don't need these speakers for bass, I have SVS for that.[​IMG]

    Dean said give these mod'ed speakers a week for them to actually bloom. But as of now I can definitely tell a difference in the vocal and the highs.[​IMG]
     
  8. EarleD

    EarleD Supporting Actor

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    Mind if I ask, but what is a Deflex Pad?:b
     
  9. dean_g

    dean_g Agent

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    If you tried to call me at work today after you took the speaker home -- you probably figured out I wasn't there. I bailed at noon. My fun meter was pretty much pegged out.

    Now, don't fall too much in love with that slightly tipped up treble because it will settle down some. I am surprised you could actually hear the additional 'air' and clarity right off the bat. Like I told you -- new caps are kind of cranky, and initially, they usually sound a little grainy and hot on top. Believe it or not -- it gets better! In another week or so -- those speakers should literally disappear -- leaving nothing but a wall of sound.

    The issue with the bass is easy to explain. There are three things going on here. 1) The slightly tipped treble is de-emphasing the bass a little. 2) The Deflex Pad has reduced harmonic distortion in the woofer. Backwave energy is being absorbed instead of firing into the back of the driver. What you are hearing is cleaner bass. 3) The midrange is cleaner. Since the woofer is under better control -- the driver will be able to produce the midrange better. When you get all of the speakers done and back into the system -- you'll be astonished at how much louder you'll be able to play it before it starts distorting. Nothing sounds worse than a woofer dancing all over the place while trying to spit out the midrange.

    So -- what sounds like 'more bass' in the other, unmodded speaker -- is really some distortion of the fundamental bass notes being caused by uncontrolled backwave energy from the driver inside the box, and resonances from cabinet vibration riding on top of the bass signature.

    Cool huh?

    I'm glad it worked out. I sure didn't want to here, "Hey asshole -- what the hell did you do to my speaker!"[​IMG]
     
  10. Chris Tsutsui

    Chris Tsutsui Screenwriter

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    Thanks a lot guys, You just put my S38s at risk with this enticing post.

    Now if I could just find the right key to get them open. [​IMG]

    I too have noticed a slightly muffled sound from them and that's beause I've compared them to better speakers.

    Earle,

    Deflex Power Pads are a revolutionary new waterproof advanced polymer damping pad specially designed to prevent speaker cone break-up due to standing waves and enclosure resonances. This allows higher sound volumes with a minimum of distortion.

    Ranging from $20 for a 5" diameter circle pad, to $40 for an 8x11" sheet. The Red power pads can be found at parts express.

    http://www.deflex.co.uk/cgi-bin/defl...deflexshop.cgi

    Of course there's other dampeners, like using the famous "blackhole 5" viscoelastic sound dampening material which runs for about $50 per 24x27" sheet.
     
  11. dean_g

    dean_g Agent

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    Brett,

    Just saw your PM. Yeesh, I need to read through that a few times and will probably have some questions.
     
  12. LaMarcus

    LaMarcus Screenwriter

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    Well, Dean called me at work to say he finished the rest of the speakers, IN ONE DAY mind you! He's a fcukin machine! I can't wait to hear all the speaker at the same time I don't know if I'm ready for this awesome sound in my room[​IMG] [​IMG] [​IMG]
     
  13. Ben Ale

    Ben Ale Auditioning

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    Wow! I also have JBL Northridge speakers. You've got me interested in working on my crossovers (N38, n24, and n-center) to see if I can find a cost-effective way of improving my HT performance. Please, let me know how these mods turn out.

    Also, how difficult is it really to change out the crossover parts? I read somewhere on the net that it can be difficult to determine the values of each part that's being replaced. Dean, how did you figure that out?
     
  14. Ben Ale

    Ben Ale Auditioning

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    thanks, Brett. Haven't had a chance to crack open my speakers, yet to see what the crossovers look like. So the challenge appears to be centered primarily on one's sodering skills?

    If the values are labeled, then it should be a simple matter to track down better quality parts via partsexpress.com or Radio Shack.

    The tweeters are the same for the N26 and rest of the Northridge series, so I might even be able to use the same stuff Dean used.
     
  15. Phil Iturralde

    Phil Iturralde Screenwriter

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  16. Ben Ale

    Ben Ale Auditioning

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    Oops, I see now. Read the post too quickly.

    thanks.
     
  17. Ben Ale

    Ben Ale Auditioning

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    any news on how the upgrade sounds with all speakers?
     

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