[walterslw]

Hello Everyone,


Can someone post what the efficiency and impedance is for the M/T module on the VR5 Annie MK II?   I am currently bi-amping, and am wondering if I could get by with a 300B on the top?   I think they are 96dB W / M into 8 ohms on the mid/tweet but would prefer someone confirm if my understanding is correct.


Thanks in advance!
Lou

[kernelbob]

Hi Lou,

My VR5-annis were 8 ohms at the mid/tweeter terminal  and the 4 ohms to the woofers.  If I remember correctly, they were spec'ed around 92 db, but I'm not certain.  The VR6's, which I still have, were around 96 dB.

Robert

[walterslw]

Hi Rob,

I always thought the 92dB was the nominal sensitivity for the entire speaker...  Who knows, I am starting to forget things ... I am sort of hoping Albert can chime in.    My EL 34 amp sounds fantastic on the mid / top, and I have no desire to get rid of it but I am thinking to also get a 300B based amp which will be between 8 - 12 watts just to play around and have some variety.   If it is 92 on the top I probably wont go forward with a 300 B amp.

Lou

[JackD201]

I have a client using 300Bs up top with SRs. I don't see any problems with 5 SEs or 5 Annies unless one routinely goes on torture percussion binges.

My guess is the midrange is padded down a bit, going by the 2904's sensitivity and that of doubled up 8.5 inch MG Excels, my conservative guess is 91dB/w/m  (8 ohms). The amp won't be seeing any big impedance swings or back EMF so it should be just fine for even spirited listening in an appropriately sized room.

[walterslw]

Mine were what Albert calls the Mark 2.5 - I think mine may have a different midrange unit in them.   Would need the Wizard to chime in

[Albert Von Schweikert]

The midrange used in the VR-5 Anniversary has a raw sensitivity of 99dB, while the tweeter has 93dB.  Both of these drivers need to be padded down to match the woofer sensitivity, since the woofers in parallel have a combined sensitivity of 92dB when you factor in the port boost and room gain.  We don't  worry about the anechoic sensitivity since very few of our customers have bass absorption traps in their listening rooms.  A 300B amp will drive the 8-ohm upper module unless you're  playing loud sustained percussion as Jack mentions above.  You'll need quite a bit of power to drive the woofer module, though, since the woofers need high current to drive the 4-ohm load with punch and tightness.  One or two hundred watts of solid state power is recommended, and the amp should be stable into a 2 to 4-ohm load.

[walterslw]

Thanks Albert.

I am actually staying with my customized upgraded Assemblage EL 34 tube amp for the top @ ~40 W/channel  and my Bryston 7b SST mono blocks for the bass @ ~ 900W into 4 ohms / channel.  I had parts connexion do a complete rebuild and signature upgrade on the assemblage,  in addition I had them match the input sensitivity and Gain of the assemblage to that of the Bryston.  Quite frankly with the brand new PSVANE 6CA7 (el 34 type) power tubes in the assemblage this combo is absolutely killer!

[musicalal]

Can I ask if it is preferable to Bi-amp rather than Biwire the VR5 anniversaries?

[SundayNiagara]

Can I ask if it is preferable to Bi-amp rather than Biwire the VR5 anniversaries?

If you use amps with identical sensitivities, otherwise you'll end up with discontinuities, (timing errors)  between top & bottom.

[Mountainjoe]

If you use amps with identical sensitivities, otherwise you'll end up with discontinuities, (timing errors)  between top & bottom.

The propagation delay through an amplifier is not a direct function of gain (or sensitivity) so it's not a given that amps with different gains will have different propagation delays. In general, the propagation delay through an amp should be minimal (10s to 100s of nanoseconds) and the difference between any two amps should not contribute significantly to timing errors in the audio across the drivers.

In fact, it's quite possible to have two amps with identical gain but different propagation delays - the delay is more a function of the amp architecture than it is gain.

What you want is to match the gain between the amps - this can be done with some resistors and Albert can help with this.

[walterslw]

In addition to what Mountainjoe said, if you are lucky enough to know the gain, and input sensitivities of both sets of amps then you can calculate how much input voltage generates 1W of output and if you have a good service technician you can have the less sensitive amp modified to match the other amp, thus avoiding the need for external resistors, pots, and extra interconnects.  I happen to live 25 minutes away from Parts Conexxion, so I had them change my Assemblage ST 40, in addition to heavily upgrading the amp, its gain is matched to within .3 of a db of my Brystons.  The sensitivity is the same, and let me say, I do not hear any anomalies between where the top end ends and the bottom begins.   What is weird is that my Bryston sounds much better just driving the woofers than driving the speakers full range.    There are definitely better amps out there than the assemblage, but on the top end it sounds magical.   I have been without music since last Friday as my Brystons are at Bryston getting a full rebuild and update-to-current spec.  I am hoping to have them back in time for the weekend .   Bi-amping IME is the way to go if you can match sensitivities and gain of the two amps.

[Mountainjoe]

What is weird is that my Bryston sounds much better just driving the woofers than driving the speakers full range.

Hi Walter - any power amplifier will achieve best linearity over a certain load impedance locus (region of complex impedance) so it may simply be that the load presented to your Bryston's driving just the woofers is more in the amp's sweet spot than driving the impedance of the full speaker stack.

As an aside, interestingly enough, in most cases, an amplifier's preferred load for maximum power transfer is not the same as its preferred load for best linearity - this is something to keep in mind when pairing amplifiers with speakers (or drivers).

Cheers, Joe