Bi-amping Infinity Ren 80 on a tight budget

Da He Hua

Active Member
I would really like to drive Ren 80 with two amps, but I am on a tight budget. So, yes, I know a pair of Pass Lab would be ideal, but that is way out of my budget. Currently I have a B&K 4420 (200 W @ 8 ohm; 350 W @ 4 ohm). Thinking about using it to drive the woofers and find another amp to drive the tweeters. Would a 100 W or even 70 W amp sufficient to drive the tweeters of a Ren 80? Any recommendations for a used non-expensive amp to be used with the existing B&K 4420 to do bi-amping? When I say non-expensive, ideally a few hundred dollars? Thank you very much.
 
I've considered this as it would be an interesting option but am not sure being a three way that it would be easy to do at all as they are not set up for this. You would need a good active crossover to accomplish this which generally are not inexpensive especially being a three way system. Also, obviously, you would have to bypass all of the passive crossover components inside the cabinets. I do not know if the mids are linked with the woofers or tweeters on the inputs. Really this would be a tri-amp situation and would require a third set of binding posts to do properly.

If you are simply thinking of driving the different sections with individual amps, I don't think this is worthwhile and do not think you will notice any appreciable difference.
 
You can definitely biamp your 80s, without using an external electronic crossover. The internal passive crossover will still filter the signal to the proper drivers. But, passive biamping, while simpler and easier, is less flexible. So, in order to properly balance the 2 amps, one amp at least, has to have some type of volume adjustment. Otherwise, one amp could play louder than the 2nd amp, throwing off the woofer/mid, tweeter levels.

If I were you, I'd pick up a pro amp. Something like a Crown XLS1002. It's cheap and good. 215 watts into 8 ohms and 350 watts into 4 ohms. With volume knobs. Try it on both the low input posts, and high posts, to see where it sounds best. I'm sure it would be a great bass amp, at least. But, it might surprise you on the high end too.

Good luck.
 
The main issue has already been addressed--balancing the output of both amps to get the low end and mid/high end outputs equal. As mentioned, this requires that at least one of the amps have attentuation/volume controls on the amp itself. Lots of folks like to power the mids and highs with a relatively low power tube amp and use a big SS amp for the low end.

Good Luck!
 
Both amps, really, need level controls unless one can confirm the amp with higher gain has the levels controls. You can turn down an amp having higher gain, but you can't turn up an amp with lower gain to match higher gain (well, not without extra measures, anyway).

Ideally for this sort of biamping you'd use use identical amps since both set of speaker inputs expect the same signal separated as they do when strapped.
 
Got it. Thanks all! Some B&K 4420s have the optional volume control at the back. The version I have does not have volume control, but at the back, there is a little hole blocked (this is where the volume control is on the version where the optional is available). How hard/expensive is it to add a volume control (of course, I mean to let professionals do it).
 
I guess what I am trying to say is that although certainly possible to do as per the manual I am not sure what you will really gain versus a single amp of sufficient power. Obviously you can certainly try out some combinations to see how you like them. Would be interesting to hear your assessment. :thumbsup:
 
I guess what I am trying to say is that although certainly possible to do as per the manual I am not sure what you will really gain versus a single amp of sufficient power. Obviously you can certainly try out some combinations to see how you like them. Would be interesting to hear your assessment. :thumbsup:
Sure, I agree with that. In terms of the single amp route, the tricky question is what would be considered as "sufficient power" for these speakers. Something with 400 watts or more @ 8 ohm. If so, it might require more money than the budget allows.
 
I think you should reread StimpyWans post. If you think there's any benefit that is a good start. I doubt you'll loose much sound integrity trying with the crowns, as for power on the 80's more than enough......jmho.
 
Ever infinity speaker that I ever bi amped with two identical amps so that output is the same sounded like they had more detail, more woofer control but always sounded thin to me as compared to using one amp, with one amp the speakers were warmer sounding, might of had something to do with less woofer control, I would say if you play your music loud bi amp, if you play at normal listening level I like them with one amp.
 
Anytime I biamp speakers, I have always used identical amps to avoid the hassle of gain/output matching, but that is just me. I have used a pair of Aragon 4004's to biamp Kappa 9's and currently use 4 matched Krell KMA 160 monoblocks for that application. I realize that those amps are kind of wasted on the high/mid ranges, but they are identical to those driving the low end, so they are perfectly matched, and the woofers are well under control.
 
For this type of "bi-amp" I did try running two Bryston 4Bs of the same vintage into my Renn 80s and honestly couldn't detect any difference (maybe just me). Now if one wanted to try different amp topologies for tweeter/mids and woofers then possibly there might be something interesting in the experiment. As I mentioned before, if one has an amplifier of sufficient power for them I am not sure throwing more current at the individual driver sections will be something you would be able to hear. I have never really understood why certain speaker systems have multiple inputs for drivers if the passive crossovers can't easily be bypassed. With the ability to adjust crossover points actively with an external crossover you might have something. Although I do feel Infinity did a good job with the crossovers in this series...
 
I am not sure throwing more current at the individual driver sections will be something you would be able to hear.

Big Infinitys (many, not all of them) tend to have seriously low impedance dips in the lower frequency ranges, so current (rather than power) is critical and audible differences can be heard in terms of bass "tightness" or "woofer control". If using a single amp that begins to "struggle" with a 1 or 2 ohm load in the lower octaves, the mids and highs will suffer as well. I am not intimately familiar with the Ren series, but I have Kappa 9's, (at one point, 3 pair of them), and RSIb's, so I can attest to their current demands.
 
For any given load you can't have more current without also inherently having more power, and for any given load you can't have more power without inherently having more current. Not sure why it is these things are viewed as separate in the context of a given load.
 
With all these debate aside, the practical question is whether B&K Ref 4200 (225 watts @ 8 ohm) as a single amp is a good match to drive these speakers, if you are familiar with this amplifier. Thank you.
 
I'd buy a different amp just because once you get to this point of doubt you will always have some doubt remaining until you try something different yourself. I know...been there, perhaps part of the reason I have acquired 15 or 20 amps, give or take, over the years. LOL.

If the speakers have nasty low impedance dips then you want to look, at least, at amps having 2 ohm rating showing a material increase increase in power over 4 ohms. I don't believe it is necessary to have amp that "double down", but a nice progression of power increase with lower impedance show that at least there isn't super heavy handed current limiting.
 
I have never had any clipping issues when running My Renn 80s, I never got the impression they have some of the major impedance dips other Infinities exhibit. Ran my with a single 4B which provided plenty of power...
 
Well, clipping isn't inherently an amplifier issue (unless it's broken) it's an operator/operation issue.
 
Sandstrom, I agree with your sentiments. The 80's have a great factory crossover. To the OP, if your looking to step it up I'd toss a good subwoofer in with these if you have not tried yet. I've owned 2 pairs and i stupidly sold both :/ before I understood what I do now.
 
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