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Nice score, MCP! And kudos for grabbing the Crown, too! She's got several of their proprietary features, I think the Grounded Bridge is pretty neat. Good grief, all those horns and a Macro-Tech 2400 to power them? I bet they can hear your system loud and clear two zip codes away!

Beautiful work! Where did you get the big Carver rug? "Powerful - Musical - Shaggy"

Good eye, Matthew! Definitely an error. You'd think the black and red wire colors would've helped... Oh, and for some reason the top ("High F") amp has its right channel feeding the left speaker, and the left channel feeding the right speaker. But at first glance, the diagram gets the basic idea across.

Funny story: on Wednesday, the crew from Carverfest Cabin 5 (Travis, Kev, LT, and I) rode into town to scour the pawn shops and thrift stores for gear and music. Largely unsuccessful with the former (nine years of CF have probably picked the vicinity clean), we did score some tunes. We went into one place that had "the best deals in town", and looked promising WRT military surplus. Kev pointed out a rusting rare J10 Jeep pickup outside, and I snapped a pic. I seriously considered buying from their impressive selection of fireworks to add to our speaker roast, but I didn't want to become "the guy that burned down the log cabin". I also already had most of the military manuals in the rack. Several aisles of tools, but most were just cheap flea market junk. No good artillery shells for the collection. I was going go ask about the SAPI plates in a carrier, but there was no price tag. I pondered the irony of possibly dying later from having a blown woofer penetrating my sternum... So what did our brave band of audio warriors end up getting at the big military surplus/redneck supply store? I bought a used Liza Minnelli CD.

Welcome to theCarversite, armstrong! I like the PM-1.5a myself, a little less refined than the PM-1200, but with the anthracite. Please show us some pics, we love pics.

listening to local commercial radio on the factory stereo in a 2004 Nissan Sentra with only the right channel working, with my ears popping as I drive up and down the foothills of the Appalachians. Oh joy.

Technically, an L-pad is a *potentiometer*, a 3-terminal device. If you only use it as a variable resistor, that's a rheostat. You should use all three terminals on the L-pad, to minimize impedance differences seen by the crossover. There are conflicting design criteria for choosing the resistance value: set at full driver voltage(max volume), the crossover will see the full value of the L-pad in parallel with the driver, which combined will always be lower than the impedance of the driver alone. Set at minimum driver voltage(no volume), the crossover will see only the resistance of the L-pad. Set anywhere in the middle will of course present an impedance somewhere in the middle. The crossover's cutoff point will change with the impedance it sees as a load. In theory not good, but seems to be no big deal in practice. But you do want to use an L-pad resistance that's not too different from the driver impedance to minimize these effects. If the L-pad has too small of a power rating, its resistance will change with high volume and time spent there, perhaps by a factor of two or more, affecting driver volume and again crossover response. All that said, L-pads are usually of wirewound construction, which means they are capable of excellent precision and accuracy. If the L-pads are of identical part number, anywhere near appropriate value and application, and installed correctly, they should have no difference in audible effect when set to the same position. Even using just the ol' Mk 1 Eyeball. But for a sanity check, turn them both to the same setting, then measure their resistances. They should be within 10%, if not 5%. As Maddmaster noted above, speaker placement can have a huge effect. Distance from the speaker to the nearby walls, differences in wall materials and coverings, reflection paths to the listener, distance from other speakers, angle of toe in, and proximity to other objects can all affect the sound volume, tonal balance, and quality. Luckily, with those stands, both your speakers should have the same height, tilt, and ceiling/floor reflections. The passive orientation, however, should have near zero audible effect. PR's are much like ports, but better in several ways. Like ports, they're tuned below driver resonance, and have a narrow bandwidth. But they don't suffer from turbulence, and thus are less localizable at high output. A PR will drop off its output around 12dB/octave, and so one tuned at 40Hz would be down at least 20dB by 160Hz. You're not going to localize anything from the PR's, unless you drove them really hard to generate significant distortion. Hearing that there's something wrong coming from the PR would be a good thing at that point, so you could prevent disaster... What do you mean by "do a simple speaker reverse"? I would definitely trust your ears! OTOH, the simplest explanation is that your hearing is not the same between your ears, which is a common condition. Do you notice a difference if you listen with your back to the speakers? Always a possibility. Might want to check if there are current-limiting bulbs, fuses, or polyswitches that might have degraded or blown. Probably not easy for you to check, except by swapping crossover components and drivers between speakers. A good quality graphic EQ in good condition should add negligible distortion. If you don't mind the computer interface, you might look into a MiniDSP unit. You're not alone, many people feel that sound quality has gone steeply downhill on more recent releases, for a variety of reasons. You might want to look into a Carver Digital Time Lens unit, or Carver CD player with DTL.

The main advantage is that it's parametric, i.e. you can change the crossover point(s) with jumpers instead of having to buy different FMOD attenuators. Some models of that PFMOD also have parametric high-pass filters for your main amp and speakers. It takes a stereo signal from your preamp. From there it depends on the model, but it looks to me like all the low outputs are summed mono. So even if they have two output jacks for the lows, they're both sending the same signal. Yes, thats where this would go, same as the FMOD attenuators mentioned previously, or any other line level crossover. These PFMODs are adjustable, and some models can also cross over the high frequencies to another amp. Which is often desirable, as it lets your main amp and speakers work less hard if they're not trying to reproduce the lows that your sub is taking care of.

I would advise this approach regardless of connections, because the divider will stiffen and strengthen the box. And if one driver (or amp channel) fails, the other driver won't suddenly see twice the effective box volume with a lousy passive radiator (potential over excursion). Since you're going sealed, I don't think it'll make as much difference as to divided or not if you wire in series, which I still think is to be avoided. Any issues from series wiring will still be there. I still think better to drive each woofer with its own channel. But hey, it's very easy to try it both ways and see for yourself, if you bring connections out for each driver (two pair of speaker terminals on the side of the cabinet). With those woofers, a relatively big sealed box is as good as you'll get for lowest bass extension. Unless you're willing go go Infinite Baffle, which these woofers would also do well at. Magnet weight isn't everything, just look at the woofers in Amazing Loudspeakers. Or neodymium magnets. I would put more trust in the specs for an expensive driver than for a very inexpensive one. Testing costs money, there's more room for profit after testing in extensive drivers, and folks who spend more money usually have a higher expectation of performance and agreement to specs. But assuming the power handling spec is trustworthy, it means the driver is capable of handling more power than your amp can put out, even at full clipping. This is not a bad thing for toughness, but if you put the woofers in a much smaller than optimum box, that amp might not be able to drive those woofers to full excursion for full output on the bottom end. Again, not bad for the safety of the drivers, though. Power specs like those usually mean the amp has a marginal power supply or current capability. Shell probably be struggling with those woofers, either 4 ohms stereo or 8 ohms bridged. Not much you can do about that without changing woofers or amp, but try and see! It may sound terrific! Depends on the music, the room, where you place the sub, your preferences, and how well the amp tolerates clipping, Sounds like something's not right. Do you get the same hum if you use a different amp, but keep everything else the same? Considering that you can find used but working 5.1 receivers on eBay with 100W/channel for $60 or less, I'd say you've got almost limitless options. The nice thing about dedicated sub amps ("plate amps") is that the usually have features like auto-on, adjustable low-pass frequency, and phase adjustment. See the one kev777 was offering above... No worries, it's been a busy holiday weekend! The majority of them are less than that, and there are a few where a pair would cost you less than $200: SUBWOOFER PLATE AMPS AT PARTS-EXPRESS.COM

No worries, Steven! Yes, the inline low pass RCA devices (Harrison Labs FMOD) should work fine. The 100 Hz low pass ones at Parts-Express HERE . The drivers you're using really want a large sealed box, like 3 or 4 cubic feet *each*. If you put them both in the same enclosure, that enclosure should be 6 to 8 cubic feet. If it's much smaller than that, you'll lose more low frequency, and you're already starting high for a modern subwoofer. Plus your amp won't have the power to force more out of the low end with EQ, even though the speakers might handle it. Glad you're bringing that old speaker back to life!

Cool project, Steven! Got pics? +1 to what RobertR suggested. You definitely need a low-pass filter... You'll get 120W out of that amp with the two 4 ohm drivers in stereo, vs. the 150W bridged into both in series, but the difference in power will be inaudible. As another good reason for running in stereo, it's generally a bad idea to run (sub)woofers in series. Differences in driver parameters can make them share the load unequally. They also couple to each other acoustically, i.e. the sound from one can affect the other. Not a problem with *dual voice coil* drivers interacting with themselves, because the coils are mechanically linked together. Have you done any calculations for optimizing the volume of the cabinet with the drivers you're using? What's the Parts Express part number for your woofers?

Well, 14" is darn *short* for most modern subs with low tuning! What kind of bracing did you use for the box? Interesting, they must tune at the factory. The newer version adds another spider, inverted near the bottom one, and I think eliminates the bias adjustment.

Thanks for the pics, Travis! That's a very serious driver! Not as much excursion by today's standards, but that's OK because of the relatively high Fs. LLT tuning would be around 35Hz optimal, so a convenient relatively short port? She wouldn't benefit much from a bigger box, so CV's suggested size is probably optimal. That thing must have some insane output around the tuning frequency! Is the adjustable suspension bias to reduce 2nd order distortion?

"WE ARE ALL NUTS... If we weren't we'd be collecting something cheap like bottle caps." - Zumbini, in THIS POST

Interesting to replace mostly non-electrolytics with $100+ of boutique film caps, but leave all the carbon composition resistors. But I guess the proof's in the pudding, whatever sounds better!

There is actually a big difference between the III and VI EQ's. I had both back in the day. Previously posted Series VI EQ curve: From the Spatial Control Receiver service manual: So Series III and IV have identical EQ. Compare the Series IV and Series VI (middle curve) EQ's above. About 3dB difference at the 35Hz and 14kHz peaks, definitely significant. But less so in view of the adjustability of the controls.

While the idea of using the yellow wire to change the impedance of the speaker is intriguing, that purpose is completely undocumented, AFAIK unprecedented, and IMHO generally impractical. The answer I gave IN THIS IMMEDIATE FOLLOWUP POST is the widely documented and accepted purpose and use of the yellow wire. The Bose Spatial Control Receiver has four amp channels. They can be set to series bridged in pairs, but for Spatial Control with 901's, the "yellow wire" goes to ground, and a separate amp channels drive the + and - terminals. The Spatial Control scheme only affects frequencies above 1kHz. Now, I'm no expert, and we're all here to learn. So I'd love for you to provide info showing that yellow wire was intended to be used to trim impedance. Or how anybody ever did so. Like I said, intriguing! However, I think it's generally impractical. There are only so many ways to add impedance to the system, and none of them make sense. First off, the 901 uses full-range drivers. Any impedance you added would have to cover the full audio range, or it would change the speaker's frequency response. Granted, you could cut the mids to help even it out, but that's a waste of amp power in passives and a drop in efficiency, and the active EQ does this far better. A full-range passive network would be big, expensive, a harder amp load, and wasteful of power. Plain resistors would be much smaller, cheaper, and easier. So what can you possibly do with resistors? With three speaker terminals, basically two possibilities: 1. Put resistance across the normal + and - terminals. This has no effect on the speaker's performance. All it does is make the amp see a *lower* impedance load, never a good thing. The amp works harder to maintain the same voltage at more current, the extra current just goes into heating the resistor. This gets significant as the resistor's value drops near or below the speaker's impedance, it could dissipate the hundreds of watts (or more!) the speaker is consuming. Let's add "dangerous" and/or "bulky" to the disadvantages. Using rheostats or switch networks only makes things worse. Putting resistance from both the + and - terminals to the "yellow wire" (terminal marked " * ") accomplishes the exact same thing, if the two resistances are kept balanced to the driver groups they parallel. Which leads to the only other possibility: 2. Put resistance from the * terminal to the + and/or - terminal in a manner that doesn't balance the driver groups they parallel. In other words, put 100 ohms across * to +, and 10 ohms across * to -. This changes the voltage division between the two groups of drivers, and their relative volume. You'd effectively be doing some of what the Bose Spatial Receiver did. However, the effect would only be significant when the resistance approached the impedance of the driver groups. So again you'd have the drawbacks of #1 above. In the extreme case of zero resistance (short * to + or -), there's no resistor necessary, but now you've got a ~4 ohm speaker- more sensitivity, but the radiation pattern is radically different from design, and you're wasting half the drivers. If you short the group containing the front driver, it's *really* not going to sound good! If you're suggesting using the yellow wire as one terminal, and tying the + and - together as the other terminal, think about polarities, and what the resulting impedance would be... Do you have any info on whatever device or accessory Bose or anybody else made to accomplish this "impedance trim"? FWIW I've never heard of anything like this for the pro 802's either, where impedance adjustment might make more sense. BTW I wonder if the whole Spatial Control Receiver concept died because nobody could find 3-conductor speaker cable...

Yeah, that would be the way the rest of the world does it.

Oh wow, that schematic in the AV-806x manual *is* the page from the Marantz MA-500 manual! The MA-500 manual is much more legible than our copy, and fills in a lot of blanks elsewhere. They really complicated setting the bias, do they expect you to use a stopwatch? Bob was long gone by the time the AV-806x came out. Who knows who licensed from who? It's a pretty conventional design, after you take away all the specialized chips that run everything. It certainly didn't have anything to do with the AV-405 of the year before, nor the AV-705x of the year after.

FIFY! Thanks, Peck! $390 for all six slave modules, same seller has slaves singly for $75 each. What's this about "Marantz MA-500"? Ah! It's a single one of the *same* AV-806x slave modules in a little monoblock chassis! Maybe a service manual for the MA-500 would help? Might explain why the module schematic in the Carver service manual looks like it's from a completely different manual...