dBspl

I would recommend searching Tom Nousaine, Dave Clark and Stanley Lipschitz. I believe they have all published reports/papers on blind A/B (A/B/X) tests they have performed. I don't think it's correct to say that non-believers are out to prove that people that claim they hear differences are being delusional. On the contrary, I believe the most professional test administrators would welcome a blind test that statistically proved an audible difference. Under these circumstances it gives the technicians and engineers something to go back and analyze and assess. That's really the only way I see to make some headway and maybe lead us out of this stalemate. Unfortunately, whenever these tests are given, the results almost always seem to come out negative, or at least inconclusive. This could be why people that believe they can hear these differences appear to be the target of the people administering the tests. I might also add that I really don't think the burden of whether something is audble or not should be placed on the non-believers. I mean, why should they have to prove something is audible when they don't claim to be able to hear it. That really doesn't make any sense. Isn't the burden more appropriately placed on the person making the claim? I've taken a lot of these tests, and while I don't claim to be a particularly well trained listener, I have had a lot of listening experience. I can't tell you how many times I taken an A/B/X test, and when switching between A & B, I thought I could hear a subtle difference. But as soon as I selected X, any difference I thought I heard simply evaporated. dbspl

I wouldn't recommend connecting both channels to the same speaker. The L&R amplifier channels won't like looking up each others output impedance. It's essentially a dead short. You could damage the amplifier. dbspl

"Amplifier power" really has no room in the discussion when you're talking about "amplifier voltage gain" or "amplifier sensitivity". They're really two different things (nor does it have anything to do with amplifier efficiency). Voltage gain is more analagous to the force required to push the gas pedal on a car (or the force required to pull the trigger on a gun). The pedal may be very sensitive (not much force), or takes quit a bit of force to move the pedal, but neither really effects the maximum power availalbe from the engine (or a gun). The manufacturer can change the sensitivity of the gas pedal to anything they want. In the same way, amplifier gain can be set anywhere you like, and in many cases is as simple as changing the value of 1 small resistor. Amplifiers are constant voltage sources, not constant power sources. All this means is that the amplifier power delivered to a load will vary as the impedance of the load is changed. Higher impedances draw less power, lower impedances draw more power. The only thing that stays the same is the voltage. Within reason, the gain of the amplifier never changes, although the power delivered can change radically. In an integrated amplifier or a receiver, the volume control is doing nothing more than changing the voltage sensitivity (or amplification) of the system (pre-amp+amplifier). In other words, the volume control is an attenuator that is controlling the overall voltage gain. A decibel is simply a ratio, and unless you specify a reference, it doesn't even tell you a lot. Many references are implied (dBSPL, dBv, dBm, etc). However, it is customary that the decibel reflects a power ratio. And thus voltage is converted into a power relationship as DrWho pointed out. There are lots of reasons why someone would want to control the voltage sensitivity of an amplifier. S/N is certainly a good place to start. In pro audio it's not unheard of for amplifier manufacturers to adjust voltage gain differently on each model model with a different power rating. They will do this because when sound companies use amplifiers with different power ratings in the same venue, they are interested in each amplifier reaching it's maximum power output at (about) the same time. dBspl

The link is correct. The 1 watt specification is basically a misnomer. Because loudspeaker impedance varies widely with frequency, it's almost impossible to establish what 1 watt really is. And even if you could, it really wouldn't be worth very much (it's not exactly sensitivity and it's not exactly efficiency...it's something in between). Amplifers are constant voltage sources, not constant power sources. dbspl

I should have been more clear. I'm referring to the equalization performed in the passive crossover. It directly affects sensitivity. It's also worth mentioning that horn loaded speakers do not behave in the same manner as direct radiators. A direct radiator speaker is a mass controlled device. The mass and the radiation resistance work against each other to yield a somewhat flat frequency response. It doesn't require a lot of equalization. A horn loaded device is resistance contolled. The mass of the moving assembly works against a relatively pure resistance. This results in a frequency response that rolls off at 6 dB per octave above the mass break frequency. As a result, it requires some form of equalization to realize a flat frequency response. dbspl

I doubt this will end the controversy, but PWK was opposed to the idea of using EQ in the reproduction chain. As a matter of fact, the mere suggestion of EQ being applied to any heritage product would likely result in a flash of the little yellow button under his lapel. Yes, it is true that EQ is a part of the function of the passive network, but that correction is applied under reasonably well controlled measurement conditions. At that point, the design integrity of the loudspeaker is “built in”; and the use of EQ, after the fact, would just compromise that. I suspect that if he believed there was a flaw at the end-use side, then the first solution would be to go back and look at the loudspeaker / room integration and try and solve the problem from that end. There are plenty of “Dope from Hope” articles that address listening room issues. The listening room, of course, has a huge influence on the perceived sound quality of a loudspeaker. In my opinion, PWK’s opinion of EQ was simply a reflection of his era. At that time, the Eq’s in use were of poor quality and almost never used properly. They generally introduced more problems than they corrected. PWK also didn’t like active filters because he didn’t believe there was a benefit. He felt if a passive filter was designed properly, it would sound just as good as an active filter, and wouldn’t be nearly as complex or expensive. One final point; adding EQ doesn’t affect the efficiency of the individual drive components, and if done properly, only has a mild affect at the system level. The EQ affects the sensitivity. Sensitivity and efficiency are not the same thing. dbspl

It's probably worth mentioning the garage needs to be well ventilated to remove the humidity in the space. Otherwise you could end up with condensation forming on the walls. You don't want a mold problem. dbspl

Sensitivity is simply the ouput of the loudspeaker in decibels given some (constant) voltage input. In most cases that voltage is 2.83V. It is only loosely associated with efficiency. If you have two drivers where the only difference is that one is 4 ohms and the other is 8, the efficency is the same, but the sensitivity of the 8 ohm driver will be 3 dB less. The reason for this is that the 8 ohm driver is excepting only half as much power from the amplifier as the 4 ohm driver. Efficiency is much, much harder to determine, and it is also varies widely with frequency. In a loudspeaker system the efficiency (barring any losses in the network) is based on the individual efficiencies of the components in that system. In a Klipschorn, for example, the midrange compression driver efficiency is more than 20%. The tweeter is about 10%, and the woofer horn is only about 8%. Of course, a typical direct radiator loudspeaker will be less than 1% efficient. dbspl

Assuming you're right that “stocks and crude are almost always lowest in December”; suggest we might be on a nice little run-up of oil prices next year. As we do recover from this recession, increasing world oil demand (and decreasing production from mature fields) should be able to off-set any additional oil supply that comes on-line. As for alternativ energy...I guess we'll see. dbspl

The KP-600EC used fourth order (24 dB/oct) Butterworth filters.

There was a Klipsch factory located in Hot Springs, AR from about 1991 to 1996. The factory was originally set up to build vinyl enclosures (Hope built wood veneer enclosures). In 1993, the woofer & tweeter build departments from Hope were moved there. Given the company's size at that time, it was very expensive to support & operate two factories, and the vinyl business for Klipsch was still very small. The factory was sut down around the 1996-1997 timeframe. PWK (& Valerie) did have a lake house in the area, though. dbspl

When we were still building the Forte...they were often referred to as "Phantom Forte's" for this very reason. dbspl

Yes...this is correct. For two closely located woofers operating in-phase, the pressure generated by one driver basically works as an acoustical load on the other, and therefore inceases the radiation resistance each driver sees compared to if it were operating by itself. An increase in radiation resistance increases the driver's efficiency (essentially doubling it). This is generally known as acoustic coupling. This generally works with any combination of components (a woofer & tweeter, for example), as long as they are located very close to each other, operate at the same SPL and are in-phase. dbspl

This is basically correct, except two in-phase drivers (operating at the same output level) will acoustically add 6 dB. If the two drivers are down -3 dB and in-phase at the crossover point, the result is a + 3 dB bump. The drivers don't have to be completely in-phase to sum well. As you can begin to see in this chart, a phase angle difference of less than +/- 45 degrees is close enough to effectively give you + 6dB. 0 degree phase difference + 6dB 45 degree phase difference + 5.5 dB (approx.) 90 degree phase difference +3 dB 120 degree difference 0 dB (approx.) 180 degree phase difference - infinity Electrically, two in-phase signals would only add 3 dB. dbspl

Adding a boundary theoretically will increase the Sound Pressure Level (SPL) by 6 dB. The Sound Power Level (PWL) will only be increased 3 dB. Of course this would have to be a perfect boundary and present an ideal mirror image to the loudspeaker. This is usually only realizable at low frequencies (long wavelengths), but in half space (and under the proper measurement conditions) it works fairly well throughout the bandwidth of the loudspeaker. In 1/8th space, the SPL can increase as much as 18 dB compared to free field! dBspl

I thought many of your points were fairly accurate. US oil consumption in 2008 was off 6.4%. China and India were up a few percent despite a global recession. World oil consumption was only down .6%. This is very surprising considering the US was off as much as it was, and we consumes 25% of the world oil consumption. I'm sure 2009 consumption will be down even more. The US may even decline by another 10% compared to 2008. But despite all this, world oil consumption will probably remain flat. Crude prices are still relatively high, hovering around $70 a barrel. I suspect you're right that we'll test $50 oil this Fall, but I also have no doubt $100 plus barrel of oil will be right around the corner as soon as US consumption starts to return to normal. I don't know if anyone has posted this already, but here's the link to BP World Energy Review. It one of the best resources I've found concerning energy. The pdf file is about 50 pages. http://www.bp.com/productlanding.do?categoryId=6929&contentId=7044622 dbspl

If you have an ohmmemter, I would check the DCR of the tweeter voice coil. I'd be willing to bet the impedance will be around 8 ohms (6.5 ohms DCR). If I remember correctly, old KHorn's were recommended to be used with 16 ohm amplifier taps even though the impedance of the speaker was much less than that. I could be wrong about that...but the best way to make sure is to measure the impedance of the voice coil. dbspl

Power Compression is primarily to blame. At high sustained input power the voice coil heats up and the impedance of the coil rises. This reduces the amount of power the speaker will accept from the amplifier. At continuous levels (using something like pink noise), the reduction is in the neighborhood of 2 to 4 dB. This is typcally how measured "maximum SPL" is determined. Under normal music conditions this usually is not a problem. The dynamics are such the voice coil never really gets that hot. dbspl

The original Klipschorn had a woofer baffle opening of roughly 6" X 12". The baffle opening was cut in half at some point (probably in the 50's) to improve the upper frequency response of the bass horn. I believe the first horn section in the Klipschorn (between the baffle opening and the first bend) does flare faster than the last two sections, but I can't be sure. My understanding of the purpose of a "rubber throat" was to control the horn resistance in a way such that it results in a flatter passband repsonse, but I've never seen any experimental evidence to suggests that it actually works. dbspl

Since Chavez nationalized the oil in Venezuela...the principle now at work is subsidies. dbspl

So it's okay for OPEC to make TRILLIONS of dollars a year selling the rest of the world oil, but it's not alright for this country to develop and use (or export?) it's own oil resources? We're not going to reduce our reliance on oil any time soon. It's as simple as that. Developing our own oil resources while developing alternatives is the only answer. dbspl

Marvel, The 3.5 million I refer to is refined petroleum. The point I wanted to make is that the US is a net importer of refined petroleum too (not only oil). In other words, more high paying jobs that we're outsourcing. Business does have a lot to do with the fact this country exports refined petroleum, but there's also some very logical reasons. For example, many refineries are located in Texas. Mexico is a net importer of refined petroleum. We sell refined petroleum to Mexico because it's easier and cheaper to ship there than most of the northern states. We also export a small amount of Alaskan crude oil to Canada for the same reason. BTW, Mexico is a net exporter of crude oil. So they sell us oil, we refine it and sell it back to them. I'm not sure, but I suspect this might have something to do with NAFTA... dbspl

Let me get this straight... Exxon Modil = Bad Oil Company Chavez/CITGO = Good Oil Company SWEET!!! So when Chavez limits oil exports to the rest of the world and drives up prices he's really helping everybody out...right? dbspl

I would refer you to the post Mark made in the Oil Bubble thread, pointing out that the U.S. exports 1.6 million barrels a day of refined petroleum products. That would go a LONG way to serving our needs if it stayed here, but the oil companies obviously make more by exporting. I'm not exactly sure what this point has to do with drilling for oil. But since it was brought up a second time (in a different thread), it's important to point out the US also imports 3.5 million bpd. It's also worth mentioning that all the refineries in this country are not US owned! Do you believe Chavez/Citgo really wants to sell us cheap gas because he really cares? dbspl

So if we're "dependent on oil for as long as it's 'available'", why can't we simply develop the reserves we have rather than depend on foreign governments? Oil prices are high because, currently, the demand is higher than what can be pumped out of the ground. And there's no signs that will change anytime soon. The days of cheap oil are over. But, as prices increasee, that will encourage conservation and competitive alternative energy sources. You can see it happening now. I doubt we'll ever see crude oil prices much below $100, and it will probably be more like $200 or $300 dollars in a couple of years. We'll know that conservation and alternative energy is working when we see a reduction in consumption, and alternative energy embraced on a much larger scale. dbspl