Spectral DMA 400s arrive in New Jersey

devert said:

Marty,

Are you still using the TacT 2.2XP in your system?

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Yes I am. Much of what I might have to say on the subject is found in the thread I referenced in the opening post. But a few more thoughts are appropriate to share as my thinking continues to evolve there as well. To begin, I think we can agree that almost every audio engineering choice has strengths and weaknesses. The use of DSP to perform a difficult job of implementing a crossover between disparate components and for performing EQ is no exception. It is worth noting that DSP is almost a de facto standard in today's production of almost CD/SACD so there are certainly professional as well as lay folks like me that find it solves a number of audio problems effectively. It's not really worth having a discussion over whether there are attributes there that are beneficial.The answer most assuredly is yes and those are likely to be application specific. Similarly, we all know that any device also brings baggage with it, whether it is an inherent coloration or a failure to execute its use to optimum advantage. So pick your poison. In my case, the most effective solution for dealing with the crossover/EQ issues was such that I thought DSP as implemented by a highly modified TacT 2.2XP unit solved more problems than it created, and in fact, does so rather well. But let's put this into historical perspective. My Pipes/sub system is about 10 years old and the DSP technology for how to "glue" these together were implemented about 8 years ago after I realized that analogue solutions were plainly disappointing. But much as changed since then.

What I am considering now is an alternative approach that just may allow me to consider using a speaker system capable of true seamless full-range 20Hz-20KHz performance that is satisfying for full orchestral SPL reproduction, but potentially arrived at without DSP. When the Wilson X2 Alexandria's came out, I was disappointed to hear that they really were devoid of the bottom octave of bass in several systems in which I heard them (and these were in very good rooms with great associated gear). However, by running the speaker full range, and augmenting them with JL subwoofers, I found newfound respect and optimism for the overall performance such a system could achieve. I have heard this approach used successfully in Steve's system (both in Danville as well as his current So Cal home) and in Brian Flower's excellent system in DFW. What I always tried to emulate after hearing their systems was the phenomenal performance of the Wilsons in the area that was my weakest link- the dreaded 80-200 "valley of death". Try as I might, there was, and still is, no way I can capture the pristine linearity in which the big Wilson's traverse this range which covers mid bass to upper bass so seamlessly into the lower midrange. Both Steve and Brian use their JLs rolling in steeply (24dB/octave) below 42 Hz with minimal gain so as to now make their Wilsons extend into the nether regions of bass which was simply non-existent without the JLs. So here we have very different ways to approach a problem, with two very different solutions. I'm aspiring to create a system capable of truly deep base that add to the Pipedreams excellent attributes elsewhere by crossing my Pipes into JL Gothams by fine-tuning a DSP crossover and EQ to get a seamless transition in that critical 20-200 area and the results ain't bad at all. But you should see the bizarro DSP EQ curve that's required to pull this off. It's so non-linear that it would make you reach out for dramamine because you would get nauseated from looking at that curve. More than that, it has taken several hundred hours of listening to get there since changes of 0.1dB can make the difference between good and really bad performance. That's right, 0.1dB. But forget the DSP curve. Its the results that count and the end result as I mentioned is actually quite good. But there is no way on god's green earth it has the linearity, and the performance of a full range speaker such as the Wilson in this area. The Wilsons of course are supremely well engineered using a hi level speaker crossover to yield truly excellent performance. Despite my best efforts, my use of a bastardized line level DSP crossover/EQ just won't match the Wilson's in this area for sheer seamlessness and here's that word again, linearity, in that part of the frequency range. Yes, the augmentation of the JLs to the big Wilsons also requires some art to make the transition to deep bass seamless, but I've heard done it to good effect in both Steve's and Brian's systems such that the liabilities are nominal and the overall sonic effect is extremely rewarding. Most important for consideration is that this solution was something simply not available to me, or anyone, 10 years ago.

So as I look to the future, I now see the emergence of speakers that I think are truly superb in most of the audio spectrum such as the Alexias, but have some limitations in the very deep bass regions that might be easily amended by running them full range and supplementing them with JL subs to yield overall system performance that I could live with. And such an approach would do so without the need for DSP. Such possibilities remain attractive for me to explore and I will continue to do so. In essence, the bottom line is this. What do you think the best way might be to build a fully full range speaker system? Do you want a talented speaker designer to do it using high level crossovers which yields a speaker that might have to be supplemented by the addition of a subwoofer without corrupting the integrity of the main system? Or do you want to try doing this yourself using some bastardized cockamoon DSP system that takes hundreds of hours to set up correctly to sound good and will still have some inherent non-linearities that can never be overcome without the proper laboratory equipment a true engineer might use to improve upon such a system? I can tell you this. The latter approach is not for the faint of heart and in fact, I truly think you have to have a screw out of place if you really want to pursue this exercise to begin with.

Let me close by saying I am encouraged that some folks are now trying to make genuine SOA speakers using DSP technology with very sophisticated engineering such as the Legacy Aeris (a speaker I have not heard). So it could be that advances in speaker design using DSP properly might further alter my thinking down the road. But now that conventional speaker design has reached new heights as manifest in such speakers such as the Alexia, or perhaps the new affordable "reference caliber" speakers like Paul Barton will supposedly debut at CES this year, one thing remains as true as ever. When it comes to choosing what you want to use in your home, there's vanilla, chocolate, strawberry and more. As my old friend and audio mentor Paul Heath used to say "You pays yer money and you takes yer choice".

Al,
Wonderful and thoughtful remarks. I like your approach very much. As Steve noted, the room is heavily treated but the idea was to make it a functionally looking "family" room rather than an audio nerd lair. Sound considerations were built-in from the ground up but are not necessarily visible . To begin, the walls are double sheet-rocked (the single best sonic benefit per dollar there is), the floor is concrete, and the wall treatments have specific acoustical properties in both the visible layer and underlayer, as do the drapes. Pictures have selected Dow Corning material behind them and the under-carpet floor padding was chosen with sonics in mind as well. The oval recessed ceiling contains Helmholtz resonators under the fabric on the beveled walls that serve as bass traps. Sprayed open cell foam was used to fill any cavities behind the walls (i.e adjacent to the fireplace) or between walls to make the room resonant free. Fortunately, because the room is large, one can get away with more "sins" but fortunately, the overall sound is quite good and pleasing. Of course, the proof is in the pudding. Attached is the on-axis room response, which was taken at the listening position 14 feet from the speakers (thus the LF and HF roll-offs appears significantly more attenuated than if you took a "typical" frequency response measurement at 1 meter). Although DSP allows for almost infinite adjustment in order to achieve this response, the speakers themselves above 150Hz require hardly any tampering. The vast majority of the action is below that, which of course is where room boundary effects are their most invasive.

I don't really know the Genesis speaker (at least the current ones) but I sure do know about Arrakis. Fabulous speaker. Got to hear it in Maine at Andy Payor's place about 2 years ago. (The guy also knows how to BBQ lamb like you wouldn't believe). But those are big ticket items. When the time comes, if I were shopping in that price range, I'd consider the big Wilson's, Raidho 4.1 and Gryphons as well. At close to 1/2 of that, the Sonus Faber Aidas are also very attractive. But lets get real. I'm probably shopping in the price range of Alexias, which, at 25% the cost of the big Wilsons, Arrakis etc, are more in my ball park. I also wouldn't be surprised to see Andy Payor leap frog the Alexia with something priced in between the Alexia and the Maxx's that could well be worth considering. My real hope is that Paul Barton will knock one over the center field fence soon by unveiling his SOA assault for a very affordable price (20K?). 2014 CES debut? Wouldn't that be something!

puroagave said:

looking at VTL's site your pre likes to see a higher load than the spectral (20k or more).

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Hi Rob,
I'm not sure I would agree. The VTL 7.5III specs are clear. They say nothing of the input impedance requirements of the gear it is driving.. Its OWN input impedance is 50K ohms (20K min). But very clearly it will deliver full output, 30V, into "10K or above". I've also confirmed that they will drive a 10K load with Luke Manley.

Output Impedance 25 Ohms (Max 150 ohms at 10Hz)
Input Impedance 50K Ohms (20k ohms min)
Maximum Output
Voltage < 1% THD
30V into 10K or above 10Hz – 200kHz +/- 1 dB
10V into 600 ohms

As far as low bass, I would say I find myself easily tempted to have too much bass, which necessitates a tweak to my DSP curve. I have system weaknesses, believe me, but bass thinness is the least of them!!