Eminent Technology 8b Speakers - Amp/wattage Recommendations

There are many ways to integrate your subs.  None of them, however are ideal. 

I am not a fan of using a L & R of mini DSP units as active cross overs between the subs and the mid LFTs. As you indicate, that requires A/D and D/A conversions. 

I will probably do a mix of analog and digital. My preamp has RCA and balanced outputs. The RCA outs will be fed through an analog HP filter and then to my main amp. The balanced outputs will go to a QSC amp with DSP and LP filter. A plate amp can be used as well. Although I have not tried it yet, my understanding is the A/D and D/A conversions really do not matter at the lower frequencies. 

I will probably call Bruce T tomorrow.  Besides discussing amps, I would like to learn more on how he implements the 8c subs, crossover frequencies, etc. 

Now that the 8c is available, I would be inclined to use Bruce's solution over the GR Research subs, assuming you can bi-amp and avoid the A/D and D/A conversions for the mid and high LFT drivers. 

ledoux1238 can you talk a bit more about your experiences of using a 20 watt amp with the 8bs?

Are you bi-amping. Is the Mactone driving only the mid & high LFTs or also the sub drivers as well? 

Are you hearing any noise or distortion of the amp at 95 dB?

Are their any compromises in your view of using a lower watt amp with these speakers?

Do the 100 watt amps do some things better? 

I don’t yet know anything about the new ET woofer system for the LFT-8, but unless it’s a dipole design I can’t see how it will be as good a mate as is any dipole sub (including the Rythmik Audio/GR research OB).

Magnepan is working on a "concept" model which will include dynamic (cone) woofers of OB/dipole design to augment their well-known magnetic-planar midrange/ribbon tweeter panels. Their MG30.7 model uses very large panels to reproduce bass frequencies, those panels sharing with OB/Dipole subs the same acoustic properties.

I own a pair of the Magneplanar Tympani T-IVa loudspeakers, which is basically a 30-year old version of the MG30.7. The Rythmik Audio/GR Research OB/Dipole Sub comes closest to equaling the outstanding sound of the T-IVa bass panels as I have yet to hear. Remember when Harry Pearson created his own "Super Speaker" by using the Tympani bass panels with the midrange/tweeter panels of Infinity?

OB/dipole woofers share with dipole planar loudspeakers the same drop off in SPL output as speaker-to-listening position distance changes. Omnipole subs (sealed and ported boxes) do NOT, so the sub/speaker balance is "correct" at only one speaker-to-listening position distance. That is imo a major flaw, one inherent in the mating of dipole loudspeakers with omnipole subs. Dipole subs also load the room the same way dipole loudspeakers do, very differently than boxed loudspeakers and subs. Mating omnipole subs with dipole loudspeakers is doomed to failure: it can’t be done, at least not to perfectionist standards.

@jwr159 I am going to change amps this weekend, give a more considered A/B and report back next week regarding 100w vs 20w amps' SQ on the 8b.

@bdp24 New 8C upgrade consists of dipole woofers, front firing 8" and back firing 6", but in a closed box, not OB+ DSP / plate amp.

One thing to consider is the added gain from a preamp...

The power amp drives the loudspeakers, the preamp drives the amp, there is no additional gain to the loudspeakers from the preamp. As long as the preamp provides enough voltage to drive the amp to full power that is all that happens. Maybe I'm missing what you are saying?