Bi wiring VSA VR4-Jrs with Ref 9.02s

capfacsurf · « **on:** 23 May 2006, 09:07 pm »

I have a pair of Von Schweikert VR4-Jrs. Each speaker has a seperate mid/tweeter cabinet and bass cabinet with seperate binding posts. When I got my Ref 9.02s a couple of months ago, I connected two speaker cables to the Ref 9's binding posts, one spade and one locking bannana, and conected the other ends to the speaker's mid/tweeter binding posts , and the other to the speakers bass terminals.

Last night, on a lark, I changed my speaker configuration by setting the VR4-Jr's to small, with an 80hz crossover, letting my sub do the "heavy lifting". The change was remarkable. My soundstage widened considerably, to the point that voices were emanating from somewhere above and behind me to the left. I had to double check my pre/pro to ensure I was still in 2ch mode, not some surround format.

I do not know how to account for the change. My only hunch is that since the sub is now handling the bottom end, more of the Ref 9's energy was available for the mid/tweeter drivers. Is my hunch correct? If not, how could such a simple configuration mod, one that would go against most audiophiles' recommendations, make such an improvement?

John Casler · « **Reply #1 on:** 24 May 2006, 12:07 am »

Hi Capfacsurf,

Welcome to AC.

Likely the "improvement" you heard is due to the positioning and phasing of the Sub.

Adding a sub, or subs can add a great amount of "increased size" and limitless presence to the soundstage. It allows the bass frequencies up to 80 (and actually well beyond depending on slope) to disperse and interact with the room a bit more.

I have 4 subs, in my listening room, and have found that to be the case.

And my system is currently powered by (you guessed it) NuFORCE Ref 9s.

Since you're in the neighborhood (we've talked on the phone before about NuFORCE) feel free to call and come by to take a listen sometime.

mfsoa · « **Reply #2 on:** 24 May 2006, 12:58 am »

Hey Capfacsurf,
I'm taking a wild guess here, but are your VSRs on a suspended wood floor? When I got mine (already broken-in demo units from Dusty), the bass was very tubby and overblown with reticent highs and no sense of immediacy at all -Snare drums completely lacked bite and were just bogged down inside the speakers. Very much NOT what I expected based on reviews and a friends opinion etc. (BTW powered by CIA D-200s)
Then I made the most astonishing improvement I have ever heard in a stereo by bracing the floor with two 12' 4x4s supported by 4 columns. (I did more than this, but that's the basics). Also centered the spikes (happen to be 16.5" spike to spike - on purpose Albert?) directly on floor joists. This absolutely transformed the sound of the speakers, not just in the bass but all the way up, which of course caused the imaging to improve big time. There is no amount of speakers/EQ/cables/absorbers that could cause this degree of improvement, for a few hundred $$ and a weekend of work.
Anyway, I never noticed my B&W CDM7NTs to have this mushiness problem (pre floorbracing) - I think the VSRs are putting so much more bass energy into the floor, or putting it there in a different way, that the entire sound spectrum was mucked up.
So perhaps the change in the physical room interaction with "small" vs. "large" speakers has opened thing up like you hear.
Or, I'm completely wrong - But STRONGLY incourage anyone with a suspended wood floor to investigate adding bracing. I'll give more details if anyone interested.

capfacsurf · « **Reply #3 on:** 24 May 2006, 02:20 am »

Mfsoa,
You nailed it: my VR4 Jrs are on the third floor of a stick built townhome! But beneath my speakers there is a bathroom, sink area and walk in closet, so there is a bit more support than if it was just out in the middle of the plywood "trampoline". I have battled the suspended wood floor monster before, and added an Auralex Subdude beneath my big M&K sub. I wonder what would happen if I put the same iso platforms under my Jrs?

Your idea of bracing the floor is a good one. But there is just no way I could pull it off, given the floor plan beneath my speakers. I will find my floor joists though, and center my speakers as you have suggested.

So you don't think using the sub and an 80hz crossover is freeing up more watts for the mid/tweeter module? Do you think the speakers would benefit from bi-amping? Enough to justify the cost?

capfacsurf · « **Reply #4 on:** 24 May 2006, 02:55 am »

John,

I have always been running a sub. It was getting all the bass that the "Large" speakers were being fed, so I figured it was like a multi-sub setup. Haven't changed sub position or settings at all. It will be interestng to see how the new settings graph.

mfsoa · « **Reply #5 on:** 25 May 2006, 12:21 am »

Cap-
Now, I don't own Ref 9s, and I haven't heard my VSRs with any other amps, so I can only guess from what I've read...
It seems hard to believe that the Ref 9s don't have enough poke to drive those speakers to the extent that there would be such an improvement by limiting the bass freqs. Especially since you are using a sub to handle some of the duties.
I thought that the NuForces were supposed to have good bass control, and while not gobs of bass, plenty of power for the load that the VSRs present (4 ohm min?) Or do you listen at ungodly levels?!

Perhaps the amps can't adequately deal with these speakers, but that's not the impression one gets from the reviews.

Opinions from NuForce owners on their ability to do bass?

Alex_G · « **Reply #6 on:** 25 May 2006, 01:05 am »

According to my measurements (at the binding posts), the VR-4JR's Impedance vs. Frequency is:
(Freq.) (Z)
30 Hz 3.88 Ohms
40 Hz 4.62 Ohms
50 Hz 4.83 Ohms
60 Hz 3.59 Ohms
70 Hz 2.62 Ohms
75 Hz 2.40 Ohms
80 Hz 2.38 Ohms
85 Hz 2.49 Ohms
90 Hz 2.64 Ohms
95 Hz 2.84 Ohms
100 Hz 3.09 Ohms
110 Hz 3.61 Ohms
120 Hz 4.16 Ohms
150 Hz 5.74 Ohms
200 Hz 5.15 Ohms

All the best,
Alex

Alex_G · « **Reply #7 on:** 25 May 2006, 01:18 am »

I was never able to get my VR-4JR's sound right with their included cross-link cables. Bi-wiring or bi-amping will completly change their sound.

I don't understand why VSA provide these cables?

mfsoa · « **Reply #8 on:** 25 May 2006, 02:42 am »

Alex,
I always wondered this myself - Why the extra expense when you're not even supposed to use it?
Maybe for people with $$$ cables so they can't afford to biwire, only to make their speakers sound worse than with cheaper cables biwired?

capfacsurf · « **Reply #9 on:** 25 May 2006, 05:16 am »

I guess it will just remain a mucking fystery. But a fine sounding one!

So if the Ref 9s have ample power to control the VR4-Jr's load (nice impedence table, thanks!) bi-amping would be a waste of then, yes? I am going to the Home Entertainment Expo in Los Angeles this weekend. Nu Force is exhibiting, and I don't want to do anything (else) stupid. So I would love some feedback on bi amping the Jrs.

As for that crazy umbilical cord, it has to be a stop gap measure 'till new owners get their cabling needs sorted out. I never had to use them, but they look rather cool. Pretty over the top for a stop gap.

Alex_G · « **Reply #10 on:** 25 May 2006, 07:09 am »

Some people don’t believe in passive bi-amping others do. In theory, I believe it should improve the sound quality and dynamic headroom for the following reasons:

About 50% of amp’s power is dissipated by the woofer at around 350Hz, and almost 75% at 80Hz.

With only 25% of available power, simultaneous complex musical passage may tax our amp and force it to go beyond its linear operating range. This may case severe intermodulation distortion and or clipping.

Low impedance of speakers such as VR-4JR’s will strain most amps and may compress their linear dynamic range.

Some musical passages may have between 20 to 30dB of peak to average ratio. For example, if you’re playing your favorite CD at 1Watt 9 feet away from the speakers and all of the sudden your amp may be asked to deliver 20dB (100W) or 30dB (1,000W) of dynamic power, the chances are you may overdrive your amp and hurt your tweeters.

However, I believe we can lower overall intermod distortion via passive bi-amping. For example, assume that a bass amp is being overloaded and begins to generate excessive intemod distortion. This distortion will never be seen by the midrange or highs due to the fact that:

#1 The VR-4JR's crossovers are completly independant and are not subject to near-field influences caused by bass or mirdrange amps.

#2 The 200Hz low pass filter will attenuate the intermod products above the rollover frequency, and therefore acoustically output minimal distortion in the midrange range area and in turn improve the midrange/highs clarity.

#3 The 2nd amp that’s driving the midrange and highs will not be taxed by the enormous bass demands and therefore have enough dynamic reserves even by the most demanding passages.

-Alex

capfacsurf · « **Reply #11 on:** 25 May 2006, 03:51 pm »

Alex_G,

Thanks for your response. Your explanation is pushing me towards bi-amping, and supports my initial hunch that a pre/pro80hz crossover setting was making more Ref 9 power available to the mids/tweeters.

If I have the 9.02s now, which amps should I add to bi-amp? Ref 8's? Another pair of 9.02's?If I went with 8's, would they be better served powering the bass or the mid/treble?

mfsoa · « **Reply #12 on:** 25 May 2006, 05:18 pm »

You probably already know this, but I wanted to check for myself - The NuForce web site says that the 9.02s make 160, 300, and 350 watts continuous and 338, 676, and 1352(!) watts (20 mSec burst) at 8, 4 and 2 ohms.
That seems like it should be plenty of power to lift those speakers off the ground!
IFAIK the VSRs aren't known to be super power-hungry, and I sure haven't heard the typical very happy NuForce owner complain of a lack of power.
Who knows, maybe if I tried the same thing with my amps I might come to the same conclusion. But I would think that if these amps were truly incapable of driving a speaker like this, especially when it is augmented by a subwoofer, that the audio world would know about it (what did NuForce say, they sold 1000 amps in the last 6 months, I think?) and it would be common knowledge.
It would be pretty neat to hear the VSRs with 2700 watts of peak power pumped into 'em though!

Alex_G · « **Reply #13 on:** 25 May 2006, 05:45 pm »

I believe both amps should have identical gains. Otherwise the lows or the mids/highs will stand out too much.

I was driving the lows with NAD 2200 and the highs with Dynaco ST-70 which I've modified and the NAD's bass response was overpowering my mids.

I need to replace NAD because its reliability sucks. The output relay issues as usual.

John Casler · « **Reply #14 on:** 25 May 2006, 06:05 pm »

Capfacsurf,

I am going to try that in the next few days with my RM30's.

I will be biamping with 2 pair of Ref 9.02.

You're welcome to stop by and hear it, or I might even be open to "lending" a pair to you to try on your Jr's.

Alex_G · « **Reply #15 on:** 25 May 2006, 06:44 pm »

Capfacsurf,

Please let me know your results If you do decide to bi-amp the JR’s with 2 sets of Ref 9.02 or other alternative amps. At this point I’ve an open mind and would like to try as many amp combo’s as possible to get the best sound out of the JR’s.

All the best,
Alex

capfacsurf · « **Reply #16 on:** 26 May 2006, 01:59 am »

Thanks for the suggestions and advice, all. I too am anxious to wring as much out of the Jr.'s as possible. At SOME point, the law of diminishing returns will be coming into play. While I had no qualms about dropping coin for my first pair of 9.02s, the second set is going to be a tougher call. Especially since, as Mfosa points out, the Ref 9s theoretically are powerfull enough to easily handle the VR4-Jrs. I might have to press John on his offer of a pair of loaners. But who knows what temptations await at the Home Entertainment Expo?

To bi-wire, I use two seperate wires per speaker, one connected to the Ref 9,s bananna plug socket, the other via spades. Is that the way to do it? The spread between the VR-4Jr's binding posts is too wide for any of the off the shelf bi-wires I saw. Any better ideas?

Thanks again everyone.

I just replaced some mid level Audioquest interconnects with a pair of Au 24's which arrived today from the UK via E-Bay. Big improvement. I think these cables work really well with my amps and Pre/pro.

Alex_G · « **Reply #17 on:** 26 May 2006, 06:42 am »

Capfacsurf,

I feel your pain, it is expensive to add a 2nd amp… However, only you can decide if it’s worth an extra expence.

VSA wire hook-up instructions can be somewhat overwhelming. Here’s what did.

For bi-wiring, I’m using (2) Canary 4S11 speaker wires per speaker. At the amp’s end, I’m using crimped Audioquest bananna connectors. At the speaker’s end, I’m using Orchards Supply’s gold plated O-ring connectors. These connectors are cheap and are easily crimped.

I’ve removed the crosslink cables and the shorting plates which were originally attached between the Sub Input and the Mid/Tweeter Input.

And finally I’m using the shotgun approach. One of the O-Ring connector’s is attached to the Sub Input binding post on the bass module and the other O-Ring Connector is attached to the Mid/Tweeter Input binding post located on the upper module.

All the best,
Alex

capfacsurf · « **Reply #18 on:** 26 May 2006, 03:08 pm »

Sweet! Thanks Alex_G. That is basically how mine are wired. Just wanted confirmation.

John Casler · « **Reply #19 on:** 27 May 2006, 08:09 pm »

Finally got a chance to "biamp" the RM30s as intended, and although they sounded "stunning" single amped, the BI-AMP sound it just another level higher.

Of particular note was the additional and more palpable detail and texture. It as just hard to describe.

Here is the "look" of the "stacked, biamp" set up on the stands I now give to all my NuFORCE clients (as long as supply lasts)