v3spitfire Posted June 12, 2003 Share Posted June 12, 2003 I'm considering an active dbx crossover for biamping RF-7s. Currently, I'm running a Y from the preamp to 4 channels of an adcom power amp, then running 2 channels to each speaker. I under stand this is not the optimal way to bi-amp, and maybe is closer to biwiring since they're identical amps - just 200 watts per channel instead of 100. Not sure if this is a good analogy or not. Anyway, anybody familiar with dbx crossovers model #223. Its for 2 way stereo, with a low pass filter at 40 if I ever want to run the sub thru it (which I may as my preamp only has a 100 crossover). The pdf literature on the web says: "All the inputs and outputs are TRS differentially balanced 1/4" jacks that are bolted down to the chassis. All dbx crossovers all feature Linkwitz-Riley 24dB per octave filters, the professional standard." First question, what are TRS differentially balanced 1/4" jacks? My preamp and amp have regular RCA jacks - are these even compatible? Also, does anybody no anything about dbx, I know they used to be well known for dynamic range expanders, noise reduction. Would this crossover work with an RF7 set up? www.dbxpro.com/223.htm Thanks for any advice! Quote Link to comment Share on other sites More sharing options...
TBrennan Posted June 13, 2003 Share Posted June 13, 2003 You're doing the right thing, using an active crossover is REAL bi-amping. You should hear a decrease in distortion and an increase in dynamic range over using passive crossovers. The unit in question simply use 1/4" jacks, what are called "phone" jacks. Radio Shack has adaptors that go on RCA plugs to convert to 1/4" plugs, piece of cake. Never used a DBX crossover, the stuff had a good reputation. If buying new I'd get a DOD, you can get a new DOD under $200 and they work well, are reliable and sound good. Quote Link to comment Share on other sites More sharing options...
TBrennan Posted June 13, 2003 Share Posted June 13, 2003 Just thought of a problem. When doing real bi-amping you discard the passive crossover and connect the amps directly to the drivers. But some speakers have passive EQ built into the passive crossovers; the RF-7 may be such a speaker. If you discard the passive with such a speaker you'll change the frequency response and basic voicing of the speaker, not good. Quote Link to comment Share on other sites More sharing options...
v3spitfire Posted June 13, 2003 Author Share Posted June 13, 2003 If I find a crossover that has a 2200hz crossover point, which is where the RF-7 crosses over, and connect the amps thru the 2 sets of speaker terminal (as I do now without the crossover), do I avoid the problem of passing the EQ? I think I do, because this is what bi-wiring would do as well? Thanks for your advice. Looks like DOD and DBX are both owned by the same company (Harmon Kardon). I'll look at them as they may have an exact 2200 hz xover. Quote Link to comment Share on other sites More sharing options...
TBrennan Posted June 13, 2003 Share Posted June 13, 2003 Del----Since the speakers appear to be setup for biwiring I think that the high frequency terminals connect to the high-pass section of the passive crossover. If you can open the speaker you can see if there is an EQ circuit between the terminals and the driver. Actually, the more I think about this, I'd just leave the speakers alone and drive them with a single stereo amp. Real bi-amping is best left to DIY speaker builders and "fools bi-amping" where you use the speaker's passive crossovers is a waste of time and 2 channels of amplification. Quote Link to comment Share on other sites More sharing options...
Trooper Posted June 13, 2003 Share Posted June 13, 2003 Whoa there! You are biamping already - two amp channels to the same speaker (one to the tweeter the other to the woofers). You're also using the passive crossovers built into the RF7. First of all, the active crossover you mention (as well as most others) are designed for pro/studio use that's why they are balanced. This is probably not how the rest of your system works. It's also not impossible to overcome and make everything work together if you really want. The bigger problem is you will totally change the voicing/sound of your speakers. Nowadays virtually no professionally designed speaker uses stock crossover slopes (i.e. 24db Linkwitz/Riley @ 2kHz). The Q of the filter is probably different. Also the high-pass filter (for the tweeter) and low pass (for the woofers) may not "meet" at the same point electricly. I.e. it may be @ 2100Hz for the tweeter and 1950Hz for the woofer or any of an infinite number of such combinations. But because of the "irregular" response nature of speaker drivers the acoustic crossover appears at 2000Hz. It can be very complicated - that's why only the pros (with lots of equipment) are much good at it. Quote Link to comment Share on other sites More sharing options...
v3spitfire Posted June 13, 2003 Author Share Posted June 13, 2003 Thanks both of you. Maybe I'll leave it alone. It sounds excellent the way I have it now. Tbrennen, I've heard the term "fool's bi-amping" before, but it seems logical that even this would have some benefit over a standard 2channel amp. Since I have 4 identical channels, at worst, isn't this type of biamping providing 200 watts per channel, instead of 100 watts. This alone seems that it would be worth doing (since I already have the amp). Essentially, at any given volume level, the amps would be working less. I know that they're both having to amplify the whole signal range, but instead of 1 amp having to put out 100 watts to get a certain volume, 2 amps would only have to put out 50 watts each to get the same volume. This seems beneficial, just not to the tune of biamping with active xover. Is your comment more related to advising not to go out and buy a second amp for this purpose? If I already have a 5 channel amp, does it make sense in your opinion? It does sound phenominal, and I have a large room to fill. I don't want to hurt anything though. Thanks again both of you. Del Quote Link to comment Share on other sites More sharing options...
TBrennan Posted June 15, 2003 Share Posted June 15, 2003 Del---You're not hurting anything, just be aware you're not getting the dynamic and distortion benefits of real bi-amping. Your amps still have to work almost as hard and each amp channel will still need the same power to hit a certain volume as if using a normal amplifier setup. The woofer still has the same sensitivity and will reqire the same power for a given volume. And the tweeter still has the crossover's attenuation in front of it. But like I said, though you may not be gaining much you're not hurting anything either. And since you already have the amp channels why not? Quote Link to comment Share on other sites More sharing options...
v3spitfire Posted June 15, 2003 Author Share Posted June 15, 2003 Thanks for the education. I'll leave as is for now, maybe I'll use a crossover after I really understand more about how the RF7 is put together. Thanks again. Quote Link to comment Share on other sites More sharing options...
Al Klappenberger Posted June 16, 2003 Share Posted June 16, 2003 Hi guys, Here a soure for good active crossover networks. I use their smallest one for my sub-woofer crossover at 70 Hz. http://www.marchandelec.com/ Al K. Quote Link to comment Share on other sites More sharing options...
Steamengman Posted June 17, 2003 Share Posted June 17, 2003 I don't know about biamping the RF7s, but my Belles are set up to be biamped by just disconnecting two wires on the crossover. Please note that the factory crossovers are retained and still active. If you want the factory info on biamping your speakers you can call Steve Phillips at Klipsch tech support. The phone number is 1-800-554-7724 and I beleive the extension is 8530. I hope to biamp my Belles in the next two months and according to Steve Phillips, I will notice a big difference in the quality of sound. I have to say that I'm biased towards Klipsch speakers, I have a pair of Belles, 4 Heresy IIs, a set of Quints, a Kv2 center channel and a KSW15 powered sub woofer. I hope this helps. Paul Quote Link to comment Share on other sites More sharing options...
lovemyhorns Posted June 18, 2003 Share Posted June 18, 2003 When I used to biamp my K-horns, I used an active crossover by a company called Ace Audio (no longer in business), and the device had insertable modules to select the frequency. It worked very well and I recommend the box if you can find one with the correct xover freq. Quote Link to comment Share on other sites More sharing options...
v3spitfire Posted June 18, 2003 Author Share Posted June 18, 2003 Paul and Lovemyhorns. Thanks for the extra info. I'll call klipsh and check out Xovers with plug in modules, if klipsh give the recommendation that I hope they will. Paul, the wire you disconnected, was it more than the typical "jumper" found on speakers? Thanks again. Quote Link to comment Share on other sites More sharing options...
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