WMcD

It is tough to diagnose from a distance. This is particularly so because we can't listen to the audio! Trey will probably have some good suggestions, but he might have the same problem. Two things to try. First, make sure the mid range is working. Playing some music or hissy noise, put your ear up to the midrange and make sure it has output. This should identify a blown midrange. (Though this should show up a more a treble problem.) Second, it may be that because of a partial mechancial failure, the bass unit's voice coil is hung up or out of alignment. If you can, try pushing the woofer diaphragm gently. It should have a nice spring action, rather than a bind. Comparing one bass diaphragm to the other will give you some appreciation. Best I can do from a distance. Let us all know. The bbs serves as an improvised data base of problems. Gil

PWK wrote an article on this. His gripe was that "pads" made up of resistors, similar to a fixed L-pad, causes anomalies in the frequency response. The use of resistances results in a condition where the speaker is no longer "seeing" an amplifier with a low output impedance. I've improvised "real" autotransformers using the voice coil connection side of 70 volt line transformers. I was expecting these to have altered frequency response. This was because I thought they'd exhibit some inductive effect. However, they were remarkably flat. So I assume that because of the good coupling, there is little inductance. To answer something that Jerohm (Ohm?) was getting at, the actual inductors and capacitors supply frequency tailoring functions, as usual, not the 'former. (The latter is at least from what I can tell. Master Al K. might be able to explain his findings!) One application is where the midrange of the K-Horn is about 3 dB more sensitive than the bass or tweeter and the 'former knocks it down by 3 dB. The Heresy uses a 'former in a similar way. The bass unit has much less sensitivity and both the midrange and tweeter output is reduced using the 'former. I don't have a schematic for the non-Heritage units but I assume the same technique is used. In one patent, PWK used a 'former to increase the output of the tweeter. It seems that there the bass and mid were okay but the tweeter was a few dB down. This is "step up" voltage application. I won't go into specifics of impedance matching here. But generally, when the 'former is used in a step down mode, the amplifier "sees" a high impedance in that portion of the auto spectrum. PWK and D.B. Keele showed this can result in lower amplifier distortion when the amp is pushed close to its limit. There is an AES Preprint on it. Of course, pushing an amp to the limit is rare given the efficency of our speakers. Regards, Gil This message has been edited by William F. Gil McDermott on 06-17-2001 at 08:10 PM

I make a test some years ago on three Pyramid woofers. I measured the T-S parameters on a test box using a Linear-X LMS system. Then I ran them with good excursion at resonance overnight which put them through more than a million cycles. Then I ran the measurements again. The results were about as close to no change as you can get. Gil

Samuel, It is not a silly question. There are no silly questions. This is particularly so when the manual is unclear. My guarded answer is that you don't have much to worry about. My understanding of your situation is that you have a concern about whether running multiple speakers off the amp at the same time is going to do any harm in the short run, or the long run. The amp manufacturer give some non-specific warnings. Your question alludes to some setting on your amp about one set of rear for music and another for music. Yet it seems you can run them both by some switch settings. That is a bit of a puzzlement. Let us know more. Others on the bbs may be able to advise. Amplifier manufacturers are probably not going to give you any advice about what is absolutely safe. They might have to honor a guarantee. My understanding of modern consumer amplifier design is that they typically have two types of protection. The first is an insantaneous current overload. This is when the user inadvertently, perhaps because of miswiring, shorts the output. The current protection circuit takes over and shuts things down before the output transistors get fried in a few milliseconds. The second is a thermal cut out. In our hypothesis, if the two speakers are causing too much current, things heat up over a period of time, usually minutes or hours. A thermisor (temperature sensing device) recognizes that this is dangerous, and shuts things down. As you can appreciate, these are circuits which are placed in the design of the amp to protect against two different situations. The first is analagous to "blow the fuse right now, we have a short" the the second is "overheating, working too hard." If you haven't had a problem so far, it is probably safe to keep on doing it. Usually, rear speakers are not playing very loud and they're not a challenge to the design parameters of the amp. The above is independant of whether it will sound "good". Designers are just trying to keep things protected. I'll throw this up for discussion. Has anyone brought an amp to the shop after a melt down blamed on parallel speaker connection? I have not heard of such. Samuel has a ligit concern which has intuitive merit. If the transistors are pulling more current, isn't the mean time to failure going to be lower? Sure. But is this a matter of minutes, days, weeks, months, years, decades? My experience is the same as Mr. "bensib". We have some very old transistor amps which haven't conked out despite parallel connections and years of service. Regards, Gil

Nice work attaching the pfd Dolby info. I think it fails to make somethings clear. First of all, they are talking about Dolby Digital encoding and storage. In that set-up the media, i.e DVD or the film, has six discrete audio channels. The 0.1 there in the storage media is the LFE channel which the engineer mixes in. (That is not true of the analog matrix system on VHS, which has just two discrete channels for storage, left and right.) The output of the Dolby Digital decoder in the HT receiver or whatever, has six discrete channels corresponding to what is recorded in the six discrete channels. We then feed that to the audio processor at home. If you have a sub at home, the LFE channel should find its way to the sub via the processor. However, if no sub, the LFE channel is being sent to where ever the "normal" bass is going. That is usually the mains set to large. But per the pdf post, the LFE channel goes up to 120 Hz. I question may be, "But what happens when my sub only starts working at 80 Hz? Where does the range from 80 to 120 Hz go?" This I don't know, and it may depend on the processor. I'll look some things up. Gil This message has been edited by William F. Gil McDermott on 06-15-2001 at 07:41 PM

My read is that once you get a damping factor higher than the single digits, it should not make a big difference. A damping factor of 60 at 8 ohms indicates the internal impedance of the output of the amp is 8/60 ohms. That is a pretty small number. 0.13 ohms. It is getting close to a dead short. A damping factor of 600 would indicate 0.013 ohms. Granted a better short circuit. But what is the big issue? It is that we may (see infra) want to have some mechanical resistance to keep the excursion of the diaphragm controlled at resonance. Where does that mechanical resistance come from? We usually think of the driver as a type of elecrical motor. We put in a signal and the magnet and voice coil are a motor to drive the diaphragm back and forth. But the magnet and voice coil can also act as a generator. If the diaphragm has mass and is oscillating, the system creates current. The current flows into the output stage of the amp. We assume the impedance of the amp is quite close to a dead short and thus it is hard for the diaphragm to crank our generator and load. That is the mechanical resistance created. This seems well and good, but what actually is limiting the amount of current the generator can create? Answer: It is not only the internal impedance of the amp; rather we have to consider all the resistance in the loop. A big factor is the voice coil resistance itself. Let's assume it is 8.0 ohms. Taking that into account, the resistance in the loop overall, given our two examples, is 8.13 ohms and 8.013 ohms. (Resistances add in series.) Thus in practice that is practically no change. Of course a damping factor of 1 would indicate an internal impedance of 8 ohms. Now the total resistance is 16 ohms. So this could adversly lower the current and the speaker diaphragm would be more free to oscillate. You can see the math. If there is damping factor of 10, we have 8.8 ohms in the loop. This is just 10 percent away from the effect of a perfect short which would cause 8.0 ohms. In some ways, it is good for us that the speaker voice coil resistance is the dominating factor, and that changes in the "damping factor" are a minor factor, once you get up to higher numbers, as shown above. In the design of the speaker / box combination, the amount of resonance is an important factor in creating bass response. In fact, "over damped" drivers have poor bass response. We want the electrical resistance in the loop to be predicatable from amp to amp. This is related to the Qts of the speaker which has a major factor in T-S design parameters. I can't explain why Tom saw no excursion with one amp and a lot with another. Maybe the second one did have a very small damping factor. Also possible is that the program had different bass notes. If you feed the acoustic reflex speaker with a note at its resonance frequency, it should move quite a bit. That's what I think. But my knowledge is imperfect. Gil This message has been edited by William F. Gil McDermott on 06-13-2001 at 08:29 PM

Mr. B and Bob G. support something that I discussed in another area. Perhaps the spikes do transmit vibration into the floor and walls. Maybe there is some better radiation in the listening room and others nearby. Gil

Ray, pardon my ignorance, which is boundless. FAPP? Gil

In my mind, I'm waffling on the vibration issue. I see claims that "spiking" does wonderful things for floor standing speakers by keeping them from moving. I can't really buy that they move that much give the relative masses of the box and the speaker cone. The argument is that the tail (bass diaphragm) is wagging the dog (speaker box) by some effective amount. On the other hand, maybe the vibrations are transmitted into the floor and makes it vibrate a little, so the sound changes. But that is a little contrary to my own theory. I shouldn't be such a non-believer in every little tweek, particularly since I haven't done the experiment. I get even a bit more wishy-washy over "spiking" tall stands. Maybe given the long leverage arm of the pedistal, the speakers would rock and vibrate. I dunno. It makes more sense that there is a potential problem which spikes would solve, if there is a problem to begin with. Let us know if you hear anything. BTW. There are those people who get $20 worth of enjoyment out of building something they could buy for $5. If it costs $10 in parts to do that, they consider it a bargain. I'm that type of guy. Perhaps you are too. The rest of the world considers it over- spending and a waste of time. That is not a dig at TalktoKeith. Just an apologia. Regards, Gil This message has been edited by William F. Gil McDermott on 06-11-2001 at 12:50 AM

I don't have any information on comparison. But let me clarify. There was the K-400 horn made from cast alumium. There was the K-401 horn made from "plastic". The drivers connected to the horn are a different issue. They were at least the K-55V and the K-55M. If you give me (via e-mail) your postal address I will send you, by mail, an article describing the various changes over the years. Regards, Gil

The real answer is a bit complicated but I'll give it a go. Amplifiers do multiply in strings. Each may have a voltage gain of 10, stringing two together will give a gain of 100. But that is really not what you are talking about, and when amplifiers are strung together in gain stages, there are special considerations. In most of OUR applications: If you have a CD player, it has a line level output. This at max is about 1 volt when the program is loud. The output circuit is designed in a certain way and it doesn't supply much current. So there is little power output of the RCA jack on the back under any condition. But not to worry, voltage alone is the analog of the music, at this point. The "pre-amp" stand alone component usually does not supply very much "gain" in a strict sense. For the most part, its function is to switch between input (CD, VCR, DVD) and allow the user to mostly turn down the voltage gain. (This is why you hear of people using "passive" pre-amps, which are just attenuators; the CD output is enough voltage, often, to drive the power amp input.) The output of the stand alone pre-amplifier is also "line level" of about 1 volt max. You usually turn this down to something less. Now, could you drive a loud speaker with 1 volt? Yes. But an 8 ohm speaker would require 1/8 amp. A pre-amplifier line level output can not deliver that level of current. Now, here, we have to talk about power or energy. What to do? Well, you need a power amp. It is designed to provide voltage gain (in case you want more than one volt) and will provide enough current to drive a speaker. In an 8 ohm speaker, if you apply 1 volt and the power amp can keep up the current drawn, there is 1/8 amp of current. In a very general sense, if you want to deliver 1 watt to an 8 ohm speaker, you must put in 2.83 volts. This assumes the amp will deliver 1/2.83 amps. That is the type of current available from a power amp. There is something to consider. Your boom box headphone out may well be simply a direct connection to it's own power amp. Headphones don't draw much current because they have a high impedance, probably around 200 ohms (some guess work). The current is 1/200th (in amps) of the applied voltage and not much power. You don't get blasted. However, turning up the volume of the control on the boom box does increase the voltage to the headphone out. Not much power is delivered to the Pro-Medias because it has a line level input which has a high impedance of say 5,000 ohms (wild guess). It takes 1/5000 of an amp if there is a 1 volt input. This is the same as most pre-amp inputs, high impedance. Very little power in a strict sense. Then, the Pro Media's has its own pre-amp and power amp to drive the speakers. But on these amps I don't know details. Gil This message has been edited by William F. Gil McDermott on 06-11-2001 at 12:18 AM

From your description, the orange colored component is a 3.3 microfarad capacitor. The strange symbol should look like a u and should in reality be a Greek mu. This serves as a simple, first order high pass filter. Meaning that only the higher frequencies are passed to the speaker. There should be another terminal on the butt end. You hook the plus (red) input to the dangling end of the capacitor and the negative input to the other terminal (the one without the orange thing). I didn't see a picture in the link. However, this is a common arrangement, if crude. It is difficult to predict how well this will work with your bass unit. If it has a 93 dB sensitivity, you might find them well matched as to level. However, the tweeter may sound "bright" if the woofer is less sensitive. If so, you'll have to get a RS "L-pad" and wire that into the tweeter circuit. One guess is that the overall combination will have a sensitivity in the area of 89 to 93 dB per watt at one meter. This makes it less sensitive than the Heresy. Doing an A-B switch to compare will probably reveal it sounds about half as loud as the Heresy, if not more. Cross over points on the Fisher is a more complicated issue. It is tough to figure out what might be wrong and how to correct it, without pretty fancy equipment. But, in any event, welcome to the world of home built speakers; horn loading to boot. Congrats. Regards, Gil This message has been edited by William F. Gil McDermott on 06-10-2001 at 11:31 PM

As a better writer than I said, "this is the sound of Padora's Box opening." So, welcome to the wire debate forum. I take the position that zip cord (lamp wire) is good enough for long runs to the speaker. I just have never seen any objective evidence to the contrary. On the other hand, credible witnesses report improvements in the context of (long) wire runs from the amp to the speaker. What you're asking about is a slightly different issue. Can the one or two foot run of "thin" wire within the speaker cause a problem, which needs a solution. To some extent it similar to a situation where the run to the speaker system input is very short. I don't think there is a problem, here. Others may disagree. From an engineering point of view, the voice coil and cross over components are recognized as having the qualities of inductance, capacitance, and resistance - - - and there are other similar factors resulting from the interaction of the box and speaker. The amount of these qualities are far, far in excess of those same exhibited by the wire by several orders of magnitude. (Mostly 100, or 1000 times more.) Really. The following is a crude example. Suppose you wanted to make your back yard lawn sprinkler work better where there is a 20 foot run of garden hose. Hooking up fire hose of three inch diameter instead of the regular old vinyl green one inch diameter hose is not gonna help. Note this is the "long run" issue. Within the speaker, it is an issue of whether putting two feet of fire hose near the sprinkler, is going to help anything. I don't think so. Heah, I read that Klipsch has a deal with Monster Wire. Nothing wrong with that. But I'd like to see a documented problem which needs a solution. So far, I've not seen it. The bottom line: Don't monkey with wiring of the interior. There is no engineering reason to do so. Also, trying to mate thick wire to small terminals is a real bear. Let me add an emote =8^o so no one takes this topic too seriously. We're all friends. Regards, Gil

Nice purchase. I had wondered whether ceiling speakers would work for "surround". Certainly something worth experimenting with since they are already in situ. I'm a big fan of a center channel. A Heresy would certainly be one good choice. In the far distant past, the Heresy (then Model H) network was set up to match the K-Horn mid and tweeter. In a regular Heresy they must be padded down to match the lower efficency of the direct radiating woofer. But originally, the mid and tweeter were running full out, with the bass driver a few dB down and not matched in level. If you get the Heresy, you might want to investigate such an atavistic approach. Perhaps the factory will help. Others have used subs with LaScallas and report very good results. Your going to have a lot of fun. Gil

No one else has stepped up to the plate. So I will. My guess is that a lot of the talk in adversing of stands is just hype to distinguish one manufacturer's design from others. The big issue is getting the speakers up higher, and you should have no problem with accomplishing that with home carpentry. At least it will get you 90 percent of what anyone else is doing. Wood should work well enough and there is not a resonance issue that I can see. Normally you think of a metal structure "ringing" more than a wooden one. On the other hand, I think there is a ligit issue about keeping the speakers relatively still. This is more an issue of mechanical stability based more on design than material. Therefore, if you build at platform on a pole to sit the boxes on, there should be some mechanical means to fix the boxes to the platform. Maybe a recess and perhaps some sort of clamping. You'll have some sort of bottom platform. You should consider making some design so it will not rock or tip. If you have a hardwood floor, probably some rubber feet will do well. If you have carpet, some thought should be given. There is a school of thought advocating the use of pointy conical feet. These penetrate the carpet so the unit gets mechancial contact with the underlying floor. Of course this is dangerous to carpet, much less orientals. One alternate solution might be to build a boxlike platform at the bottom and fill it with sand or the like just to give it some weight. This would also help the issue of top heavy-ness. A bigger base extending outwards a farther distance would do the same, naturally. Overall these structural considerations are pretty intuitive. Your own solutions should do as well as anybody else's, if not better. If you want to get fancy, consider how you are going to run the speaker wire. Maybe use a hollow pole, or just have a some means of tying the the cable in the back for the run down the pole or other supports. Kids, pets, and parties are a worry. Will someone use the speaker and stands as a handhold, a scratching post, fire hydrant, or cocktail table. Something to think. What could ruin the installation, or how could the stands hurt a member of the household if they are tipped over. Such are my thoughts. Gil

Well, maybe we can conclude that: Bass really is non directional, electronic metering would detect problems our ears don't hear, Klipsch speakers sound great under adverse conditions. Makes sense, Gil

Well, I'll be stickler and point out that a room has eight and not four 1/8th space corners. Of course I'm counting the ceiling. This observation does no good for Q-Man's project though. Am I reading the spec for the Jubilee theater speaker correctly? Tests are run in 1/2 space. If so the output could be better in 1/4 space at a floor wall intersection. That makes a good argument for center placement. On the other hand, the theater Jubilee can probably be considered two half Jubilee's stacked on top of each other. So, arguably, you could chop one in half, put it in 1/4 space, and get the same bass response as advertised for the full theater unit in 1/2 space. Something to ponder. Gil Gil

After sleeping on this, I think I'm only partially right. There is probably an inductor or auto transformer acting as a pick up coil. The tweeter's own magnet might be shielding the voice coil. I'll experiment and let you know. Gil

Nice work guys. I have built a pair from the Speakerlab plans from scratch too. So I can appreciate the effort. Let me open up a real can of worms. It seems to me that reverse engineering a Jubilee from the AES article would be a far easier woodworking project than making a K-Horn "close copy". Any thoughts out there? Gil

Tom was really great with the Yooo Hoo. Funny. It seems like we're getting into deep water with the new, versus old run off. Perhaps this can be a contest at an Indy convention match up. Ha, Indy engineering versus Hope engineering. I'll bet on the big old corner horns. Regards, Gil

I haven't done this specifically. However, I do believe think that folks are overcautious about making a mistake which will lead to ruination. Nope. If you can change a light bulb and swing a wrench, this operation is not too much more. Have fun. Of course, do keep track of what nuts came from where, what wires go where. Gil

How very, very, very interesting. I'm gonna try to recreate this. The answer is pretty obvious though. The TV has a cathode ray tube. In it, "rays" (actually electrons) are boiled off the hot cathode at the back of the tube. The high voltage between the cathode and the front of the screen (anode) attracts the electrons to the front of the tube. The front of the tube is coated with phosphor. It phosphoreses when the electrons hit them, throwing off light or photons we see. However please also know there are coils of wire at the yoke of the tube. These are fed with a video signal. The current in the coils create a magnetic field which alter the path of the electrons so they "paint" a picture on the anode/ front screen. This is how TV works. However, please note that the windings on the yoke are creating a magnetic field in time to the video. How far can these fields go? Normally not a problem, unless you have a sensitive "receiver" to detect them. The tweeter has windings on the diaphagm (actually the "former" cylinder which makes up the "voice coil") and a magnet. An audio signal is fed to the tweeter windings. Now you have sort of an electomagnet sitting in the field of the permanent magnet, and the former and diaphragm move in time to the audio signal. Magnets attract and repel. Hence, sound. This is how speakers work. However (this is your problem). The magnetic field from the CRT is inducing a current in the winding of the tweeter. So it is becoming an electo magnet from that influence, rather than the audio signal. Hence it is "transmitting" the video signal. Klipsch speakers are sensitive, or efficent. Gosh, this is very interesting. If the tweeter has a "bucking magnet", the latter narrows the location of the tweeter's magnet's field. This is good, since it prevents the tweeter magnet from interfering with the work of the windings in the CRT yoke. A bucking magnet doesn't act as a shield, though. It just localizes the magnetic field created by the magnet so it doesn't interfer with the crt. Notably, the bucking magnet (if that is the technique used) doesn't keep the magnetic field from the yoke/video from getting into the tweeter windings. On the other hand, suppose a mu metal shield had been used to prevent the magnet field of the tweeter from escaping. That would also have shielded the tweeter from the magnetic/video field created by the crt. Wow. It doesn't seem like this is a big problem. If the problem needed to be "solved" you'd have to have a shield for the tweeter. I don't know whether copper is going to do it. Ferrous mu metal might. Ask Trey Canon at Klipsh. Drive him nuts =8^o. Regards, Gil This message has been edited by William F. Gil McDermott on 06-01-2001 at 08:52 PM

It seems to me like you're picked two potentally good locations. However, just about everyone on the forum has agreed that experimentation is necessary. One additional thought comes to mind. Do you need some floor standing lamps at your listening location? They could serve as stands. I have a two floor standing lamps manufactured by Holmes. They have an "urn" firing at the ceiling and a gooseneck for direct lighting. Very nice units for lighting. I bought them at Lowe's, a home improvement center. No, I'm not trying to sell you mine. And I don't use them as stands. However, small surrounds could be rigged to such units. That way you have the surrounds high and wide. It could work. Gil

I'm with Malcolm. Err. I just can't believe that 12 inches of wire creates a problem, or solves a problem. Gil

I think the issue here is distance between the magnets in the speaker and the cathode ray tube itself. In projection TVs the crts are down at the bottom and the light is bounced of a mirror at the back, then forward to the screen. So a speaker sitting on top of the set is about three feet away from the crts. That is a fairly good distance. Ha. Speaker manufacturers shield the magnet with mu metal or bucking magnets. Does anyone know whether tv manufacturers have shielded their crts with mu metal? That would solve a lot of potential problems. Gil Gil