Crazy idea for a budget biamp setup?

[whtboy]

I've been reading a bit about the complications caused by complex passive crossover networks and the benefits of active crossovers combined with bi- or tri-amplification. I'm not an electrical engineer, so please let me know if any of my reasoning here is off.

I've got a Yamaha 5 channel A/V receiver. The amp on each channel is rated to 75W rms but the power supply is only rated to 210W so I'm guessing my max simultaneous rms output is closer to 50W if I run 4 channels at the same time. This receiver has individual preamp-ins for each of the amp channels so you can hook it up to an external decoder.

I was thinking... I already have a PCB for a stereo 2-way 24dB/octave Linkwitz-Riley active crossover that I bought from ESP a couple years ago - http://sound.westhost.com/project09.htm

For just a little bit of cash I could build this crossover and use it to split a line-level stereo signal into L-high L-low, R-high, R-low. If I set the crossover point to be the same as the stock cutoff between the woofer and squawker, the woofers can be driven from 2 of my Yamaha's amp channels without any passive crossover components at all. From what I have read, passive low-pass filters are bad because they interfere with an amplifiers ability to damp some sort of feedback from the woofer, meaning the amp has a harder time controlling how the cone actually moves, which results in sloppy, muddy bass.

I'm guessing I would still need a passive network to split the signal between the squawker & tweeter, but whatever I do there will have the benefit of the signal already having come through a steep, active high-pass filter lower in the spectrum (which won't interfere with the math of the passive network). Given that, I'm hoping I might be able to get away with a simple network here, which I've read is a good thing except for the amount of signal that bleeds over the gentle slopes.

Granted, this would completely ruin my ability to use my receiver to switch between sources (which at this point is a DVD player & a CD player) but if there is a big gain to be hand in sound quality I could probably build some sort of mechanical input selection into the crossover box.

If this sounds like a decent plan, I think I could do it all for under $100 plus my existing hardware.

EDIT: and of course I would be giving up the ability to do any sort of multi-channel HT stuff with my existing hardware, but I think music is generally better for a person than movies anyway so...

What do you guys think?

-jacob

[steamer]

Hello,

Welcome to the forum.

I have recently went to a triamp configuration with an active xover to split signals at 500hz-20khz for my Altec 511b/902 horns and below that to the bass bins on my LaScala's/BagEnd subs.

If you have level controls for each channel and passives to protect the tweets it should work.You may be able to use your existing passives to divide the higher signals with some simple modifications.I cant give advise there but others on this forum can.You might be able to use what they call a L-pad in the signal line to the tweeter.

In my recent expierience the biggest hurdle was matching the levels of the various drivers and amps.

BTW what speakers are you listening to?

Greg

[whtboy]

1976 Cornwalls, born the same year I was =)

[Dan1045]

If you want to avoid all the building, use a car crossover, some are quite good these days. All that you need besides taht is a power supply to provide the 12v dc to power it.

Dan

[DrWho]

I think you would notice better improvements by simply moving to a higher quality amplifier - the quality of your reciever's amplification is probably going to mask any improvements you might otherwise achieve.

[whtboy]

Honestly, I've just been reading a bunch of articles on Rod Elliot's site and am curious what the difference between active and passive will really be. Of course, I'd love to have a real amp too, but that's a bit more expensive than putting together this network =)

EDIT: That brings up a question that's been on my mind for a little while though - what makes a "good" amp good? Large amounts of capacitance available to each amplifier channel (related to headroom?)? Enough transformer to keep the caps charged? Some magic related to the output impedence being well-suited for your average driver? The "quality" of the amp circuit design and components used? Low distortion?

Everyone seems to believe in the sonic superiority of good amps (I'm not suggesting there aren't differences) but I have yet to see a complete and concise analysis of the issue. It seems to me most people just mix a little science with a good measure of folklore and just try different things to see what sounds best.

[Dan1045]

I can tell you the difference between passive crossover and active is dramatic. I used to have a set of jbl L200 speakers that I biamped. They had a 15 inch woofer and a 1 inch horn driver for the highs. I bought a decoursey crossover (it also had volume controllers for each band) speced at 800 hz with a 24db/octave crossover rate. Using a hafler amp (100 watts for the bass) and a rotel amp (70 watts for the highs), it totally changed the character of the speakers. One change I did make was to take the driver out of the cabinet and put it on a jbl 2370 biradial horn while still using the passive crossover. Going to a modern horn helped but not as much as when i bi-amped. This setup was done in lieu of the pair of carver 1.0ts that I had been using with the passive crossovers. On mono they were good for 1000 wpc, but were never as good sounding as the active crossover setup with much less power.

However, after installling the active crossover the detail you could hear was amazing. Female vocals especially. Imaging was much tighter and you could actually place instruments exactly where they should be. The vocalist was out front, the guitars were behind and to the sides, and drum dead middle and you could follow where the drummer was moving between drums. The bass was much more controlled and powerful. I attribute this to the amps being directly connected to the voice coils and able to control them much better. On a really well recorded piece of material, it was almost like being there. Subtleties were revealed that I had never heard before except on a high dollar pair of headphones. This was better in that the impact was visceral...if there was deep bass, you could feel it explode while still getting everything that was recorded. No high dollar audio interconnects, 12 gauge electrial wire between amps and speakers.

The only setup I ever heard that was equal to this was a set of Klipschorns setup with mcintosh equipment in a room built especially for them and equalized to the room. In 1982 it was 50k worth of equipment...

I am currently building a set of belle enclouses and will be tri-amping them. Crossover points will be 500 and 4500 hz with a 30db/octave slope. After reading ALK's piece on extreme slope crossovers, I believe that will be the way to go. For the mids I will be using jbl 2482 horn drivers on jbl 2380 horns and a jbl 2404 horn tweeter. Efficiency for the mid is 117 db/watt and the tweeter is 105 db/watt. Woofer will be BEC's version of the k33e. Although I am tempted to use a jbl pro woofer and interchange to see what it will do too.

Dan

[whtboy]

I was initially looking at triamping options, but even building it myself a 6 channel amplifier would have run around $300 with a proper power supply - not a lot compared to commercial audiophile grade amplifiers, but a lot of money to spend on a DIY project that might fizzle =)

If I can actually get this crossover built (my first DIY audio electronics project) it will go a long way to build my confidence in that arena.

-j

[Jeff Matthews]

Honestly, I've just been reading a bunch of articles on Rod Elliot's site and am curious what the difference between active and passive will really be. Of course, I'd love to have a real amp too, but that's a bit more expensive than putting together this network =)

EDIT: That brings up a question that's been on my mind for a little while though - what makes a "good" amp good? Large amounts of capacitance available to each amplifier channel (related to headroom?)? Enough transformer to keep the caps charged? Some magic related to the output impedence being well-suited for your average driver? The "quality" of the amp circuit design and components used? Low distortion?

Everyone seems to believe in the sonic superiority of good amps (I'm not suggesting there aren't differences) but I have yet to see a complete and concise analysis of the issue. It seems to me most people just mix a little science with a good measure of folklore and just try different things to see what sounds best.

Well, you must have missed all thoise headroom threads. I think we tend to agree its the power supply and capacitance. I can't say I have the science down enough to read specs and buy blind. But I can darn sure lift an amp and tell you I'll bet this one's good. []

Let me know when you're ready to compare my Crown to your Yammy. In terms of price, I think my Crown can be found used for $400-500. The money up front might be better spent than 3 or 4 $100 DIY projects that never really made that much of a difference.

[whtboy]

No, I read a good amount of the headroom threads. It just seemed to me like "a little science with a good measure of folklore" =)

Using my existing Yamaha amp in a biamp setup will actually cost less than $100, definitely a reasonable amount I can part with without making special budget considerations.

What I will probably do when I rebuild my existing network is move it outside the cabinet and mount individual terminals for each driver on the cabinet so I can switch between the active and the passive networks without having to open the cabinets each time.

-j

[tigerwoodKhorns]

Greg,

I have heard a few say that matching levels was a long process. It is probably the divider network that I used (a Yamahe D2040) but I was able to dial my system in in less than an hour. I have a 200 wpc QSC for my woofers and two teac l700P's for the mids and tweets (30 wpc @ 6 ohms). The yamaha has digital and analog attenuation. I set both of the Teac's volume pots to full and the QSC to 26 out of 32 db.

Here is where it was so easy. The yamaha lest you mute any indivikdual channel, so I can tun any individual driver off. I just listened and turned off drivers to isolate what I thought was too high and made adjustments. It was a very quick process that has required no further adjustment. I did one channel than matched the other. I know its silly, but the really cool part is watching the ananlogue volume controls move by themselves to match the other side (they are motorized). I did have to make an adjustment after tube rolling btu that has been it.

I really need to run pink noise to check everything but have not gotten to it because it sounds so good the way it is.

Chris

PS - the steep crossover curves and time delay do seem to widen the sweet spot.

To the person who started the thread, I saw an auction on eBay for an Ashley *2004 (or 4002??) three way stereo analog active for $250 in mint condition. I know that you have 5 channels of amplification, but Teac L700's are cheap and if you can get one of the Ashleys, this looks like a really nice crossover. The Yamaha is awesome, but a bit more. You may be able to find a deal on eBay, but again, over your budget if you are sticking to it.

[steamer]

Greg,

I have heard a few say that matching levels was a long process. It is probably the divider network that I used (a Yamahe D2040) but I was able to dial my system in in less than an hour. I have a 200 wpc QSC for my woofers and two teac l700P's for the mids and tweets (30 wpc @ 6 ohms). The yamaha has digital and analog attenuation. I set both of the Teac's volume pots to full and the QSC to 26 out of 32 db.

Here is where it was so easy. The yamaha lest you mute any indivikdual channel, so I can tun any individual driver off. I just listened and turned off drivers to isolate what I thought was too high and made adjustments. It was a very quick process that has required no further adjustment. I did one channel than matched the other. I know its silly, but the really cool part is watching the ananlogue volume controls move by themselves to match the other side (they are motorized). I did have to make an adjustment after tube rolling btu that has been it.

I really need to run pink noise to check everything but have not gotten to it because it sounds so good the way it is.

Chris

PS - the steep crossover curves and time delay do seem to widen the sweet spot.

Chris,

I actually thought getting the levels set was't bad,I just got hung up on the sensetivities and gain of the bass amps in comparison to the 4watt SET for highs.I had the input level controls for the Brystons wide open,and was tring to match everything with the rane 2way.I could get evrything sounding good then have to readjust everything for the next disc.I chased my tail for a day or so,then it dawned on me the the Scala bass bin was vibrating like crazy,more than normal!.I noticed this early on but it didnt connect in my mind.Before I put the SET's and new horns in the system I was powering the Scala's with my Shannling 50watt PP monos and had to set the volumes for it at -12db and the Integrator for the BagEnds at +10 to get a balance,this was stuck in my head so I started out with the bass levels maxed on the Bryston amps.Well after I got those backed off everything fell into place and now I havent touched anything except for a minor tweek to the bass levels on some recordings with the Rane and that being only 1db or so.

Here is a link from a post I did on the Decware forum describing my first impressions and the stages I put the system together:

http://www.decware.com/cgi-bin/yabb/YaBB.cgi?board=zen;action=display;num=1134436661

Greg

[tigerwoodKhorns]

Greg,

I have been considering using SET amps for my midrange. I am replacing my midrange and tweeters with JBL 2404's and Altec 511b's and JBL 2470's.

I listen at low volume levels and love detail and accuracy. I really like the Teac's and QSC's but will add SET for midrange if I will see an improvement.

What do you think about the Angela design amp?

Chris

[steamer]

Greg,

I have been considering using SET amps for my midrange. I am replacing my midrange and tweeters with JBL 2404's and Altec 511b's and JBL 2470's.

I listen at low volume levels and love detail and accuracy. I really like the Teac's and QSC's but will add SET for midrange if I will see an improvement.

What do you think about the Angela design amp?

Chris

Chris,

I am not familiar with Angela design(guitar amp?).

I think you would like an SET design for your midhorn setup,and it would be a big improvement IMHO,as far as low power SET's hooked directly to the efficient 511/2470 combo its plenty.

I have been listening at low levels lately(more than ever before)and am amazed with the clarity,detail and accuracy,I have the power consuming lower freq. covered with SS and find that 4watts gives me plenty of headroom on my 511/902's.

Your selection of SET topology will play a big role in your enjoyment,but in general SET rules.I am new to SET and would like to try other tube/circut designs like 2a3 and 300b with a kit I can build myself.

Greg

[tigerwoodKhorns]

The Angela circuit is a SET design that I hear is highly regarded DIY. Check out their site.

My only fear with SET is that I live in the desert and a space heater is not a good idea here. I probably would not use it in the summer (electric bills can be really hight here).

The power would probably be plenty as I do not turn it up much.

Chris