Brad,
Were you at JBL when they were making the XPL series of speakers mostly for the Japanese market? I worked with JBL at that time on developing the front baffle for those speakers and molded all of them for JBL. They were really terrible in the wood shop though, so many mistakes that we had to correct before we could mold those baffles. I think I made more money designing the tooling for that project than we did making the actual baffles, they were crazy about quality as they were destined for Japan.
Were you at JBL when they were making the XPL series of speakers mostly for the Japanese market? I worked with JBL at that time on developing the front baffle for those speakers and molded all of them for JBL. They were really terrible in the wood shop though, so many mistakes that we had to correct before we could mold those baffles. I think I made more money designing the tooling for that project than we did making the actual baffles, they were crazy about quality as they were destined for Japan.
Around the time of the XPLs I was an employee of Harman Electronics, which was an internal supplier to JBL Consumer, Harman-Kardon, and Harman-Motive. I wasn't all that close to the JBL consumer or pro speaker people, and after 1994 I did most of my consulting work for various incarnations of the computer-centric and later aftermarket-Apple-centric divisions. Of course I knew some people personally.
I guess I'm not too surprised about the wood shop
Thanks Brad,
To bad we didn't cross paths back then, it would have been interesting. On the wood shop side it was a series of errors time and again, they would miss something or cut something wrong, luckily we had our own shop that could fix their errors and just charged them for the service. I had some designs floating around inside JBL at the time and showed them some stage monitors I was working on molding and I am sure that gave rise to the EON series of enclosures. They just wouldn't pay the price to make those out of structural urethane and went with a much cheaper plastic for those enclosures. My next door neighbor was a very good friend of Sidney Harmon and his wife. A major entertainment lawyer who had two floors in Century City's main towers.
To bad we didn't cross paths back then, it would have been interesting. On the wood shop side it was a series of errors time and again, they would miss something or cut something wrong, luckily we had our own shop that could fix their errors and just charged them for the service. I had some designs floating around inside JBL at the time and showed them some stage monitors I was working on molding and I am sure that gave rise to the EON series of enclosures. They just wouldn't pay the price to make those out of structural urethane and went with a much cheaper plastic for those enclosures. My next door neighbor was a very good friend of Sidney Harmon and his wife. A major entertainment lawyer who had two floors in Century City's main towers.
You mean the alumina will replace the metal in the entire thickness of the layer from place to place ? I see.
Thank for this warning, Richard, you are a real master when it is about caps.
I will have to measure all my filters to see what happened with time.
Richard,
When I watched them making film capacitors after they were assembled the end caps were encapsulated with epoxy resin. So you have measured decay of this type of cap over time or are we talking about another method of construction? I always was under the impression that if you stayed under the voltage range of this type of capacitor that they were fairly well stable for decades. I didn't observe the film and fold type of construction so I can't comment on their construction.
When I watched them making film capacitors after they were assembled the end caps were encapsulated with epoxy resin. So you have measured decay of this type of cap over time or are we talking about another method of construction? I always was under the impression that if you stayed under the voltage range of this type of capacitor that they were fairly well stable for decades. I didn't observe the film and fold type of construction so I can't comment on their construction.
As aluminum oxide almost instantly on contact with air, I guess there are assembled in a neutral atmosphere?
The caps with stranded leads can get air into the interior via the air gap/space between windings resulting in oxidation of the met-film and the epoxy fill does not change that condition. I have seen met-film Caps of popular audiophile brands with the plate layer so thin you can actually see thru the met-film. The outer wrap is another potential entry..... what is your wrap made from... mylar? Often it is no matter what the dielectric is. The other condition which will cause C to be lowered over time... is over-voltage.
Many speaker XO caps are 50 volts on low-mid level speaker systems. 100v is a little better..... but that limits it to amps with less than +/- 50dc supplies. The metalized film layer will burn off some plate area each time it is over-voltaged.
In coupling cap apps with tube circuits the voltage rating of the coupling cap should not be the operating voltage on the cap..... but the B+ supply voltage.... this is because the full B+ is applied to the cap until the tube heater comes up and current thru the tube is established.
The cheaper caps are competitive on price....... to get a lower price, a thinner dielectric is used. This gives zero voltage margin for over-load. The better caps (REL etc) use high pot testing to 2x and 3X rated voltage.
THx-RNMarsh
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I did see some caps made with stranded leads, they were made that way by order of the customer, a high end audio cap company! The owner of the company made all sorts of audiophile caps for these guys but that is what they wanted. For his normal caps he didn't do any of that stuff. Some of these were very well know audio companies who had him make caps to look like something special while the truth was they were bog standard caps with a fancy wrapper. All the caps were made with German film for the caps, the owner told me he didn't use anything else. When he was around he sold me some of his surplus for a couple dollars for bags of caps, many were 100v and some were 250v caps and he also sold me some that were 1% cap values. His real customers would never ask for this silly stuff, they were sold to the military and very large electronics companies. Audio caps were just a sideline where he could charge these guys for the special packaging that they demanded.
I have used a lot of 100 volt Film and foil Relcaps for crossovers and haven't lost 1 yet, is the failure mode for the film and foil a more dramatic shorting of the cap rather than the degradation of the value of the metalized film ?
So I would be in trouble with 100 volt caps with 200 or 300 watt amplifiers.
100 volt electrolytics are the most common voltage rating on most mid to low end speakers I've taken apart . Bennic was selling 35 and 63 volt AC caps for crossovers recently - seems like they'll be due for replacement rather quickly
So I would be in trouble with 100 volt caps with 200 or 300 watt amplifiers.
100 volt electrolytics are the most common voltage rating on most mid to low end speakers I've taken apart . Bennic was selling 35 and 63 volt AC caps for crossovers recently - seems like they'll be due for replacement rather quickly
So we are discussing about how to make a cabinet resonance free? The information is all there on the net.
But there is a question whether or not we should allow the vibration. This is very basic IMO, but most people don't understand the situation hence the debate.
Basically what we need to be able to understand this (and many audio issues) are to build things and to listen things. So, we need to have experience building various things, and we need good ears to validate or draw conclusion.
Building good speakers is not about getting the flattest response or the most non-vibrating enclosure. WHY? Because most of the time we cannot get all that we want, so we need to sacrifice things to get the highest overal quality score. We need to understand the imperfect world that we are dealing with, so that we can accept/appreciate the value/concept of making proper sacrifice.
Here is a very basic analogy. We are building a 2-way system. The woofer doesn't have low enough Fs to produce sound that we want. So what is our option? Get the enclosure/vent to produce the low frequency for us!! Is it right or wrong?? (Think about open-baffle).
Now stop talking, do this: Build an enclosure from concrete to replace your current speaker. What will you hear? A stupid subjectivist with good ears will say "Oh, hell! This is not what I want. MDF is better!!". A stupid objectivist will say "Hmmm... this sounds different. Clean, dark background. The enclosure doesn't produce sound at all so this must be hi-fi!!"
The truth is that we want low distortion, flat response, non-resonating enclosure, along with all the other necessary properties to
make a perfect sound. But we cannot have that. I often think that, the more expensive the speakers, the more effort the designer should give to achieve perfection, especially in enclosure resonance. But in reality, many expensive speakers still utilize excessive enclosure vibration to get good sound. This shows how difficult it is to achieve all-perfect loudspeaker so that such sacrifice has to be done here and there, including using vibrating enclosure.
Now the question is, how a vibrating enclosure can make a good sound??? You find the technical answer by yourself. I know from my ears that it is true. With deader enclosure, it is harder to get a certain sound that is very good. At some point when dead enclosure (in combination with our expertise) cannot give that, then we have to make a decision, whether to sacrifice and throw away the benefit of having non-resonated enclosure.
I don't want to mention at this very moment, what sound that could be "produced" from resonating enclosure. But it seems that this resonance should be "controlled" so it doesn't interfere with other frequencies (HF) and (along with XO design) doesn't interfere with LF! (I guess in term of phase?). This "good" resonance is useful only for certain LF, may be below 200Hz (just a guess). The higher the frequency, the harmful the resonance. We are fortunate here because the higher the HF, the lower the power, the smaller the panel size. If one panel is used, I guess the perfect enclosure size is a piramid. But this is aesthetically bad. But in my last speaker, I solved the issue with separating each driver's enclosure. Tweeter with its own enclosure was lifted above the midwoofer, and so was the midwoofer above the woofer. This way, each woofer is given the room to vibrate(!!) at their controlled "SPL". The foundation for each enclosure is positioned at the edge where resonance is minimum. The key point here is that the top panel of the woofer enclosure is not in contact with tweeter enclosure so is given a chance to "vibrate". I have seen some other used dual panel to separate enclosure with unique foundation. Goldmund did it with its own way. I think my approach is similar to a speaker, which I think is a Kondo.
Clearly, what you need is a timbre box
(also available in an IKEA salad bowl version)
Timbre by Running Farm Labs
(also available in an IKEA salad bowl version)
Timbre by Running Farm Labs
It depends on the mfr how much over voltage they can take. Most anything IMO from China et al will be marginal with little to no margin to go over the parts voltage value. REL caps are very conservatively rated for long life.... get tested at 2-3X the part rating. (the exact amount of high-pot voltage depends on dielectric used). You will, luckily, have no problems using their 100V rated parts.
Met-film will open or clear away film... burns it off (reducing plate area). The film and foil is too thick and the result of over-voltage is a short circuit. So, F&F must not be over-voltage. But why over voltage either/any type?
I guess the caps of 35-50-63vdc etc are used a lot with receivers of modest power (voltage). My power amps use +/- 75vdc PS rails or p-p of 150v. So I wouldnt use anything less than 200Vdc rated C part for long and stable life.
THx-RNMarsh
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Jacco,
I think those students need a few more classes if they think that piece of steel is going to produce a flat frequency response and have any kind of fidelity. Having worked on and consulted on a flat panel speaker I will say the issues are very hard to overcome and have a decent sounding device.
Richard,
When I built crossovers and used Polypro caps I always used multiple caps in parallel to get the exact cap values I was after. I had up to 6 caps in parallel many times and each was rated at least 100v rating and those were American made cap. Could you ever damage a cap under those circumstances or would the DF make that impossible with that many parallel caps?
I think those students need a few more classes if they think that piece of steel is going to produce a flat frequency response and have any kind of fidelity. Having worked on and consulted on a flat panel speaker I will say the issues are very hard to overcome and have a decent sounding device.
Richard,
When I built crossovers and used Polypro caps I always used multiple caps in parallel to get the exact cap values I was after. I had up to 6 caps in parallel many times and each was rated at least 100v rating and those were American made cap. Could you ever damage a cap under those circumstances or would the DF make that impossible with that many parallel caps?
Bcarso, Kindhorman
For what it's worth, my wife's pair of JBL Ti600 floorstanders, uses 2 6.5" bass units, 4" midrange cone and 1" titanium tweeter, vintage 1997, made in Denmark, using Son Audax drivers (just peel off the JBL sticker), actually sounds rather good for its price range. I believe one of the reasons for that is nicely damped, well assembled cabinet. POssibly their last series, or at least one of the last series of midrange speakers with real wood veneer. No ground breaking sound, but nicely controlled and in my view well balanced speakers well worth their price. They demonstrated that two smaller bass units can actually perform rather well. The downward extenstion is no big deal, but it is clean and coherent. All in all, I'd say a very good buy.
Then I bought the biggest (at the time) control monitor pair, those plastic moulded things, and Sub 10, the active subwoofer. The sub is a job nicely done, no grand performer, but no obvious faulty either, and convincing when adjusted well. Very well thought out. Unfortunately, totally let down by the two plastic jobs, which didn't sound even barely good, Chepaset drivers on the market, sort of slapped together and hoping for the best. Got rid of them real fast.
For what it's worth, my wife's pair of JBL Ti600 floorstanders, uses 2 6.5" bass units, 4" midrange cone and 1" titanium tweeter, vintage 1997, made in Denmark, using Son Audax drivers (just peel off the JBL sticker), actually sounds rather good for its price range. I believe one of the reasons for that is nicely damped, well assembled cabinet. POssibly their last series, or at least one of the last series of midrange speakers with real wood veneer. No ground breaking sound, but nicely controlled and in my view well balanced speakers well worth their price. They demonstrated that two smaller bass units can actually perform rather well. The downward extenstion is no big deal, but it is clean and coherent. All in all, I'd say a very good buy.
Then I bought the biggest (at the time) control monitor pair, those plastic moulded things, and Sub 10, the active subwoofer. The sub is a job nicely done, no grand performer, but no obvious faulty either, and convincing when adjusted well. Very well thought out. Unfortunately, totally let down by the two plastic jobs, which didn't sound even barely good, Chepaset drivers on the market, sort of slapped together and hoping for the best. Got rid of them real fast.
dvv,
I think that two 6 1/2" drivers can do a very nice job if done correctly. I have some drivers I have designed that easily get down to 35hz and get up to 2.5Khz with a nice flat FR and very benign impedance curve, so I know it can be done. It is a shame that Harmon bought all these other companies such as Audax, they made some very nice devices. I've used many European made speakers and I did like some of the Audax tweeters. I've ised the Audax TWO25AO soft dome tweeters and though they were really inexpensive they measure extremely well and sound better than many more expensive soft dome tweeters. I guess those are no longer available if Harmon killed all of that off?
I think that two 6 1/2" drivers can do a very nice job if done correctly. I have some drivers I have designed that easily get down to 35hz and get up to 2.5Khz with a nice flat FR and very benign impedance curve, so I know it can be done. It is a shame that Harmon bought all these other companies such as Audax, they made some very nice devices. I've used many European made speakers and I did like some of the Audax tweeters. I've ised the Audax TWO25AO soft dome tweeters and though they were really inexpensive they measure extremely well and sound better than many more expensive soft dome tweeters. I guess those are no longer available if Harmon killed all of that off?
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