RTi12 versus Onkyo 905; Bi-amping versus bridging

[Steven Menk]

So, following the theory of buying the best speakers possible and figuring the rest out later, I've had a set of RTi12 for several years. Since then I've gone from my-first-receiver to now an Onkyo 905.

Which still leaves the question. From what I've read and can attest to, the RTi12s are happiest with a lot of high current power. The more power the better for damn near anything you'd see in the home audio market. The Onkyo is rated at 140 watts/channel @ .05% THD @ 8 ohms, but with a lot of apparent headroom. It also includes the option of bi-amping, or bridging 8 ohm or higher speakers. I've read while the RTi12s are rated as 8 ohm speakers, it's best to treat them as "high current" or lower impedance speakers.

Bi-amping seems to have produced a slight but noticeable improvement in the top half of the cabinet... Or at least I've talked myself into thinking so. Given that, is it safe or advisable to attempt the bridged configuration with the hope of improving the bottom half of the cabinet?

Quite frankly well-enough is awfully damn good (did I mention the DSWPRO 500?) and on balance I probably wouldn't sacrifice the beautiful highs and mids for a little more bass.

Just curious. Thanks.

[leroyjr1]

Forget Bi-amping and bridging and get yourself a good amp

[Steven Menk]

Well of course that's the obvious solution. And I'm not opposed to spending money. I was just hoping somebody had some input on the question of the RTi12s nominal impedance rating versus the how to in practical terms handle it.

Or in other words, when somebody, say Polk, says "It's nominally 8 ohms but preferably you should use a high current amp", it sounds like "We say it's 8 ohms and it won't destroy your stereo, but really it's not..."

I don't have a problem with that, but I would like to understand in somewhat more quantifiable manor what exactly that means. High current sounds to me like low impedance. But do they simply mean it will take an assload of power which a low impedance amp is more likely to deliver (head room?)?

In other words should I take Polk at their word and try bridging my amp or take them at perhaps their implication and not?

Like I said, I'm more then happy with my Polk speakers and will certainly buy again. I just want to make sure I understand what I've got and how to make the most of it before I move on.

[Steven Menk]

Of course I can hardly say that I'm disappointed that the biggest, baddest, receiver from a well respected company such as Onkyo isn't nearly up to the task of really driving these speakers. Like I said, I bought the speakers and would figure the rest out later.

I can't argue with the theory.

[sir_lagzalot]

I don't have RTi12s, but I do have the RTi10s and I can tell you they sounded good hooked up to my receiver, now that I added high power amps they sound amazing. :)

[Steven Menk]

So there is no particular thoughts on, all else being equal, bi-amping versus total power? Or more specifically in my case, I could easily switch my bi-amp configuration to a bridged configuration which could deliver ~300 watts per channel versus bi-amping ~150 X 2 per speaker.

I'm concluding that the bridging is in fact safe and will likely try it...

[mmadden28]

So there is no particular thoughts on, all else being equal, bi-amping versus total power? Or more specifically in my case, I could easily switch my bi-amp configuration to a bridged configuration which could deliver ~300 watts per channel versus bi-amping ~150 X 2 per speaker.

I'm concluding that the bridging is in fact safe and will likely try it...

Have you tried changing the speaker settings in the amp from 6ohm to 4ohm? Not recommending that you do it, just asking if you tried it to see if it would make a difference. I don't exactly understand why the AVR has this choice or what happens under the hood when its changed, but it's there-it might be a current limiter or something.

Below are my thoughts and essentially a regurgitation of some of the things I've gathered so far from this and other forums.

I have the RTi12s and the Onk 805 and like sir_lagzalot stated-huge improvement when going to a separate amp. Its not wattage values that you're comparing here and I can't get into any of the engineering, but separate amps are built very differently, with higher current capacity, etc, etc. To the point where a 100wpc amp may outperform a 140wpc AVR(just an example).
Yes one would think that the internal amps in a higher end AVR should be good enough. However biamping with the same AVR is not really bi-amping-its just a way of providinde dedicated channels of power to the speakers drivers separately. You're still limited to the max the AVR can provide-you may get a small improvement, but not as much as you would with a separate amp.
You have to also understand that that 140wpc is not likely still a full 140wpc with all the channels driven at the same time. Where Separate amps (decent ones anyway) are usually rated with all channels driven at the same time.

My Onkyo supports bi-amping but not bridging-So I I have not tried it, but I would say that bridging would likely yield better results than bi-amping. The way I understand bi-amping with an AVR- your basically providing a dedicated channels worth of power to the highs and channel to the lows, the highs won't need as much of that power and so will likely be wasted-but may provide for better reproduction/SQ of those highs. Where Bridging is providing more overall wattage to both highs and lows-likely split as each driver will draw what it needs.

Further--Speakers are rated for 8 or 4 ohm usually, but depending on the frequency played through them the impedance will change, and can drop below 8 ohms or even higher. I'm sure there is a chart around somewhere on the frequency to impedance curve for the RTis somewhere.

Amps don't have an impedance rating itself, but they should be rated to be able to handle a certain miminum impedance load such as this ACME amp can handle down to 2 ohm loads, etc. Somethign tells me that the RTi's don't dip to much down into the 4ohm or lower territory or they would likely have rated them as such like the LSi series is (and in fact my LSi9's can dip below 2 ohms at certain frequencies). They are likely to require more current because of the number of mid and low freq drivers that have to be driven.

Hope that helps :o

[Steven Menk]

I appreciate the detailed response. However there is a significant difference in the amplifier design from the Onkyo 805/6 to the 875/6-905/6 though. That the 870+ are bridgeable is the obvious different, but current handling is the real difference.

But again, we are getting into the paper ratings versus real performance, which is kinda of the whole point of my original question.

[curved]

Are you running HT? If yes, just run them in stereo until you get a beefier amp. Yes that AVR is badass, but the RTi12's are not some simple bookshelf or 2-way tower speaker. They REALLY shine with power. Your AVR is perfect for a nice HT and will probably power your other speakers with plenty of power.

If you bridge it for HT, you'll be loosing a lot of the front soundstage.

[NewHTguy]

Steve,
I own an Onk 875 and have my Rti10's bi-amped (mainly because I don't have room for a 7.1 set-up). The reason I chose to bi-amp and not BRIDGE the fronts, was that the owners manual claims that bridging would limit me to a 2.1 set-up. I don't understand why that would be, but that is what it says. With the 905 are you able to bridge and still have 5.1?

[Steven Menk]

Nope. You're right. The 905 manual says the same thing.

[Steven Menk]

Oh well. I'm building a home theater, but in the meantime I'm in a fairly small living room. For now I'll just stick with the bi-amped configuration while keeping an eye out on Ebay and such for a good amp.

Right now: Onkyo 905, RTi12s (bi-amped), CSi5, FXi5, DSW Pro500. And I have a set of TCi80s still in the box that I'm planning on using as rear surrounds in the theater.

[NewHTguy]

Personally, I wouldn't rush to buy an amp if you have a small room. And if you do, I would think a two or three channel to be sufficient. Relative to the average HT, your set-up is pretty bad a** even without an amp. Only rarely do I turn my volume past 65-70 and it is pretty darn loud. What has never been clear to me is whether the poeple who swear by amps are listening at high volumes. Don't get me wrong, I'm sure more power is a good thing. I just wonder how much it would matter at low volumes. Guess I'll have to buy an amp to know!

[Ron Temple]

Personally, I wouldn't rush to buy an amp if you have a small room. And if you do, I would think a two or three channel to be sufficient. Relative to the average HT, your set-up is pretty bad a** even without an amp. Only rarely do I turn my volume past 65-70 and it is pretty darn loud. What has never been clear to me is whether the poeple who swear by amps are listening at high volumes. Don't get me wrong, I'm sure more power is a good thing. I just wonder how much it would matter at low volumes. Guess I'll have to buy an amp to know!

That question has been asked and answered. It depends on the individual, the speakers and the amp with associated gear. Generally, when the speakers are demanding, it's very apparent in nearly every environment. Noticable at low volume, very apparent a moderate volume and stark when cranked.

[NewHTguy]

Ron, I don't doubt your claim. It is the "nearly every" part that I wonder about. How many people who experience a difference at "low volumes" were starting out with an AVR as powerful as an Onk 905?

[Ron Temple]

Ron, I don't doubt your claim. It is the "nearly every" part that I wonder about. How many people who experience a difference at "low volumes" were starting out with an AVR as powerful as an Onk 905?

I understand and I'd hesitate in your shoes too. There are many (not on this forum) that claim all amps/AVRs sound the same when not overdriven and level matched and there's no changing their mind. I can hear significant differences in the models of each I've tried, but have never heard a high end Onk. If your speakers are an easy load, then perhaps there would be little difference. LSis, SDAs or some of the other current hungry Polk or other brand speakers would be the best candidates to experiment with separates on. Speakers that keep on giving...

[Steven Menk]

There are many (not on this forum) that claim all amps/AVRs sound the same when not overdriven and level matched and there's no changing their mind.

Having done the back to back comparison between the Onkyo and the Kenwood it replaced (same everything other then the receiver), I'm certainly not one of those people. I guess the question is more understanding the parameters of the amplifier which effect the overall performance in what way.

[xandra]

Steve - According to a tech I spoke with Onk, Bridging really does double your power. So you might try bridging just to figure out roughly what improvement you'd get from adding power - altho this might not be quite as much wattage as a dedicated 250-300w amp, it'd certainly give you a damn good idea, before you fork up for an amp.

PS recently added on Onk 875 to my arsenal, and am loving it.

[mmadden28]

---Onkyo 705 & Denon 3808ci Receiver, Onk 875---.

PS recently added on Onk 875 to my arsenal, and am loving it.

Holy mackeral--Which are you using? Do you have 3 setups? or are you using
all 3 in some fashion or another in the same setup?

[PTong88]

TO Steven:

That sounds like a great setup that you currently have. I have the "baby-brother version" of your setup as you can see and am very happy with it. I get to play with Polk Audio equipment everyday because of where I work. I have a room designated to just Polk Audio equipment and walls of receivers to plugs them up to. I get to mess with all of their current lines of speakers and all of their subs from the PSW, to the DSW, to the new micros. I wish I could take it all home.

[NewHTguy]

Steve - According to a tech I spoke with Onk, Bridging really does double your power. So you might try bridging just to figure out roughly what improvement you'd get from adding power - altho this might not be quite as much wattage as a dedicated 250-300w amp, it'd certainly give you a damn good idea, before you fork up for an amp.

PS recently added on Onk 875 to my arsenal, and am loving it.

Good idea. Will try that before I fork over the cash for an amp.

Xandra, any opinions as to whether the 875 with Rti 10's still begs for more power?

[Sherardp]

Forget Bi-amping and bridging and get yourself a good amp

I agree with this, I was biamping my 12s off my Sony 7100ES AVR and outlaw monos. I switched up and now run the 12s off a D Sonic Magnum 1000S and they sound amazing. I'd suggest a good amp also. Try ICEpower.

[leroyjr1]

Onkyo's known for running HOT. Bridging will put a lot of strain on your receiver.If you're going to do one I would Bi-Amp.

Where are you located? If your near me I'll bring over a amp to let you hear the difference

[Steven Menk]

Onkyo's known for running HOT.

I've read that in a bunch of places, but haven't experienced it. I have the receiver in a well ventilated area, but still. It gets sort of warm over the Reon video processor, but not over the heat sinks for the amp and not at all at the front panel.

EDIT: BTW, I'm in the DC area.

[curved]

We all know what excessive heat does to electronics over time....

That's why I would get another amp for your fronts. Your Onkyo will love you for it.

[mmadden28]

My Onk 805 runs hot, and I'm using an ext amp. WTF? Anyway, the suggestion to bridge was made so you can see if you hear a difference-not necessarily to be you're solution-it was a temporary thing, so running hot , etc is really not relevant here. As Xandra suggested, just try the bridging, you don't have to buy anything to try it-what can it hurt?

[xandra]

beware:following slightly off-topic response to mmadden...

Quote:
Originally Posted by xandra

---Onkyo 705 & Denon 3808ci Receiver, Onk 875---[from sig].
PS recently added on Onk 875 to my arsenal, and am loving it.

mmadden queried:

Holy mackeral--Which are you using? Do you have 3 setups? or are you using all 3 in some fashion or another in the same setup

Lets see: ...Denon in LR Setup, Onk 705 running toothbrush, Onk 875 running vibrator...

No really, my 875 is temporarily running my BR setup (5.1/RTi6 sys). while the Denon's in the LR. I'd like to try the 875 with the LR setup - but it arrived early, no one around to help move the monster, so I talked UPS guy into helping me unbox then put on shelf in my BR (didn't figure he'd want to wait for me to unhookup the Denon). I'm going out of town shortly, but plan on trying out 875 in the LR when I get back.
Unless the Onk sounds significantly better, it'll probably stay in BR, cuz the Denon's kindof a PITA to operate - can't imagine dealing with it half concious.

and the 705?...currently in the wings as back up should either monster need repair. Thought about selling it, but I really love it.

[xandra]

Good idea. Will try that [bridging] before I fork over the cash for an amp.

Xandra, any opinions as to whether the 875 with Rti 10's still begs for more power?

really don't know, since I had the 10's on an Amp before 875 arrived. But I'd run the 10's on the 705 (100w), and it really wasn't bad, particularly once bi-amped. The amp definitely was an improvement, tho can't say it was absolutely necessary. But should note that I don't listen to music particularly loud.

If you're not into blasting music, I doubt you HAVE TO get an amp. disclaimer: (I don't know spec's / needs of 12's assuming only moderately more power hungry). Since you're talking about a pretty powerful reciever only running 2 channels, There's no harm in trying for awhile without. Then if you opt to go the amp route it'll be like having a whole new system: xmas 2x a year.

In the end it's your ears. If you're happy with the way things sound, leave it alone.

[Steven Menk]

Let me try to rephrase a little bit:

Given the normal qualifications such as everybody has a different ear, every room is different, etc. etc. the question is what are the design aspects of an amplifier which determine overall listening performance given the particular qualities of my particular speakers.

For example I would describe the Onkyo as being much more clear and precise on the highs and mids then the 100 watt Kenwood it replaced. A symbol crash sounds much more detailed (or less muddled) and interesting for example. Having heard a number of cymbol crashes in person and though the Kenwood as well as having looked at one on a spectrum analyzer, I would say it's likely that the lower harmonic distortion of the Onkyo is the design aspect that results in that improvement. Further I'd expect a higher end amp with even lower distortion to perform even better in that regards since THD seems to be the parameter most of them advertise on.

The second parameter and the one would seem to have more effect on the lower end is power and power delivery. On paper at least it would seem the RTi12s together should be an par with the DSWPRO 500. I have more total power 280W (140WX2 continuous, 360? dynamic) going to a set of drivers with a similiar frequency response: 18Hz-120 (12 db/octave cross-over), 30-120(basically) 3 db points for the lower half of the RTi12s, and 23Hz - 160Hz overall, 30Hz-125 3 db points for the DSW.

Of course I'd have to figure out the efficiency of the DSW and how much power it's actually getting relative to the bottom half of the RTis... It's entirely possible (if not likely) that the sub is just plain getting a lot more power for a given volume level. Which is fine, I certainly can't complain about the overall results.

However while this is a largely a HT sort of application, I probably do end up listening to more music then I do theatring... And of course I would just like to at least know and understand my equipment... And in a completely non-scientific way I've always liked pure stero music versus stereo with a sub. No basis or logic for that, just a thought.

Thanks for the thoughts guys.

[Steven Menk]

I'd also add that the back-to-back with the Kenwood was the same everything other then speaker wires (I bi-amped the Onkyo with new cable all around). Same speakers, same, room, same sources...

Well almost. The money is the JVC Audio-DVD player (pretty good, certainly no where near the best) in direct mode from each. That's the most honest back-to-back on the amplifiers themselves.

CDs, MP3s, DVDs, and everything else are were the improvements were the most notable included not only the amp itself, but since these are digital links include the Onkyo's processing and DACs which are certainly much improved over the Kenwood. In terms of total package, there is no comparison, but that has nothing to do with the amplifier itself.

In the DVD-A comparison, certainly the symbol crashes and general clarity were much improved, including bass lines.

The question is back to what I asked before.