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Is it possible to get Bass control with Tubes and A7 Speakers?

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Is it possible to get bass control from a tube amp into an Altec 416A driver? Would love to hear your thoughts. Have tried a number of system set ups with my A7 speakers and needless to say the only thing thus far to have control on bass is a old Accuphase E 202. Looking at possible biamp set up with SET for horns and solid state for 416 drivers and using either Hiraga, Accuphase or Marchand crossover. Comments are most welcome.
Thanks,
Ramon

Edits: 10/13/09 10/13/09

Follow Ups:

RE: Is it possible to get Bass control with Tubes and A7 Speakers? - nl 11:55:34 10/16/09 (1)
Below the cutoff of the front horn around 125hz, the bass from an A7 is basically coming from a huge helmholz resonator peak around 70hz, augmented by a lot of boxwall resonance. It's a big fartbox. That is not necessarily such a bad thing, and many people enjoy their A7 systems despite their fuzzy, inadequate bass. However, if you want something a little more serious, I think you'd have to look into something like a sealed sub at least. Of course, this would also mean you don't need such a big cabinet, which then leads to a dedicated fronthorn midbass something like the Edgar midbass. For really serious bass, I'd look into the Danley tapped horn subs, particularly the TH50 which is designed for home use.
- RE: Is it possible to get Bass control with Tubes and A7 Speakers? - Monte Verdi 20:03:48 10/16/09 (0)
  Frankly, I am confident the Altecs can do bass well. In fact I have heard them do it well with large Accuphase power supply's. The question was can they do it well with tubes. I believe they likely can, they're will simply have to be some augmenting with cabinets, crossovers and proper damping on amps. After this years RMAF I will not let go of Altecs as they still smoke most everything else on market today.
  
  Thanks,
  
  Ramon
For starters, what have you done to the cabinets? - eso 19:52:06 10/13/09 (1)
Altec 825/828 cabinets are flimsy and dissipate a significant amount of the bass energy the drivers can produce.

Install extensive internal bracing, i.e. 2x4 glued and screwed diagonally on the sides, top and bottom, 2x2 glued and screwed in the corners. Caulk all of the corners and anywhere that may leak. Seal off the midbass horn flare sections and either extensively brace them or stuff them until they are dead and solid: I filled mine with sand, but that adds about 150 lbs per cabinet. Re-size the vent to 100 sq. in. and make sure the front of the cabinet at the vent is well braces as well. Finally make sure the cabinets are sufficiently damped internally, at least the back, one side and the bottom to kill standing wave resonances.

Having done that you should have an A7 system performing to it's designed specs. The midbass will be much clearer and blend with the upper horn better. The bottom will be much tighter, more defined.

Having said that, even of you were to install "wings" as prescribed in VOTT theater installations you will get good output down about 3db at 45Hz and falling rapidly below that. That is what they do.

With those mods even a sonic impact T-amp will have decent bass. Without the mods the cabinet is highly resonant in all the worse ways and producing a veritable sonic sludge.

eso
They were a carnival of American decay on parade, and they had no idea of the atrocity they had inflicted upon themselves–Henry Chinaski
- RE: For starters, what have you done to the cabinets? - Monte Verdi 20:39:26 10/13/09 (0)
  Yeah, I have damped outer parts of horns with mortite but have not followed "Sound Practices" other recommendations of reinforcing cabinets. Thanks for reminder, I will pull article out. I must say I do like some of the cabinet anomaly's though. But if adjusting cabinet will tighten bass up I'm all right with that.
  
  Edits: 10/13/09
If by bass control you mean damping... - LineArrayNut 17:15:01 10/13/09 (6)
...and not true lower register ability, yes. I gave up trying to get my VOTT's to do "bass" ie, 20 hz fundamentals and used them as they were meant to be used. Actively Electronically Crossed over at 80 hz 12dB/ octave and run by a 100 watt OTL amp they had as much bass control as you'd want. And even run full range by the OTL amp they did respectably well. But I'm a basshead and ALWAYS want a true subwoofer run by lots of big, highly damped SS watts in all my systems - so YMMV, etc...
I *like* the loudness button!
- RE: If by bass control you mean damping... - Monte Verdi 17:45:19 10/13/09 (5)
  I currently get plenty of bass with (Accuphase) control. SET bass tends to be slow and undefined. Perhaps amps I have used? Mid-range of course does not get any better than with SET. This is why I am considering a marriage of SET with solid state.
  
  Listen mostly to Classical, Jazz and Krautrock.
  - RE: If by bass control you mean damping... - CliffC. 18:32:29 10/16/09 (2)
    Shindo Cortese.
    It will do it all--all by itself.
    I know,I have one(for over 3 years now).
    - RE: If by bass control you mean damping... - Monte Verdi 19:56:07 10/16/09 (1)
      What speakers are you running Shindo gear on?
      - RE: If by bass control you mean damping... - CliffC. 23:35:23 10/16/09 (0)
        
        In Reply to: RE: If by bass control you mean damping... posted by Monte Verdi on October 16, 2009 at 19:56:07
        
        I use the Solovox and of course the Cortese is a great match and really controls my massive 8 inch woofer--it should,the Solovox was voiced with the Cortese.
        I have not used the Cortese with your speakers but have used it with a few different designs including one that I was about 5 years of very familiar with at the time;thus I am fairly confident in saying that it would probably give you the closest approximation to ss bass control and SET-like,300b-like(-ish) midrange in a single stereo amp that you are going to find.
        That's why I love it.It just plays music without the typical SET limitations,as long as 10 watts is enough for the speakers.
        It is an all-rounder,not the best in any one area probably,just really damn good across the board,in all areas and just plain fun to listen to.
        Not many SETs(if any) will have the bass control of the Cortese.
  - RE: If by bass control you mean damping... - drlowmu 20:40:09 10/14/09 (1)
    Hi MV,
    
    You state this: "SET bass tends to be slow and undefined. Perhaps amps I have used?"
    
    YES !!, almost all SET amps have problems doing bass with real life dynamics - and good ole fashioned "slam".
    
    There is an answer, and its the ONLY one I am aware of.
    
    Build an SET amp with a ultra powerful and "fast" power supply, and you will have almost ALL the life and dynamics that was recorded in the original event. I know of NO other good way to reproduce this. It is an AMPLIFIER design problem, and not a speaker problem.
    
    One very low powered SET amp, on a A-7 moded speaker, can and should "do it all". I know how to build them. A few others have done so also. Contact me off-Forum and I can provide details.
    
    Amps, not necessarily speakers, are the biggest audio TURKEYS of all !!
    
    If you biamp, there are problems : you have an extra active stage (crossover) which ROBS your transparency, and unless both amps are identical, you will HEAR the time constant anomalies, or mis-timing, and differing signatures, between differing amps, on ANY real good high resolution system.
    
    The best answer is to build a GREAT SET amp! It is actually possible to do so, now a days. How refreshing.
    
    Jeff Medwin
    - RE: If by bass control you mean damping... - GM 08:58:55 10/15/09 (0)
      Agreed, I've periodically been a 'broken record' that it's the typical SET amp's weak/narrow BW power supply that's the culprit, but when folks price out the components required any discussion grinds to an abrupt halt.
      
      GM
      Loud is Beautiful if it's Clean! As always though, the usual disclaimers apply to this post's contents.
RE: Is it possible to get Bass control with Tubes and A7 Speakers? - Paul Joppa 15:20:14 10/13/09 (3)
Can you define or identify "bass control" more precisely?

I can see four technical issues that may be involved:

1) Power. The Accuphase can deliver 50-100 watts, which if you needed it would severely limit your choice of tube amps.

2) Damping factor. The Accuphase offers a choice of 1, 5, or 50. Which one works in your setup? Or does it make any difference? This will give a lot of guidance in choice of tube amp.

3) Equalization. The A-7 is neither flat nor uniform in directivity in the bass, though the quality of the bass is widely admired. The Accuphase offers four different controls that adjust the bass response. Do you use or need any of them? If so, that will affect your choice of tube amp or preamp.

4) Power bandwidth. Tube amps have output transformers which limit how low a frequency can be delivered at full power. While most amps will adequately drive most speakers with most music, most of the time, it may be that for your music and your speakers you would need a tube amp with a greater inductance than the average. These are available, but you might need to be selective.

Not knowing which of those criteria (or others I haven't thought of) are important, it's hard to respond usefully.
- RE: Is it possible to get Bass control with Tubes and A7 Speakers? - Monte Verdi 17:37:44 10/13/09 (2)
  1. Do not need Accuphase as part of biamp.
  
  2. Accuphase is currently set to soft on rear damp switch.
  
  3. Sound enhancement Bass and Treble RIAA EQ is engaged set flat.
  
  Hope this helps.
  - RE: Is it possible to get Bass control with Tubes and A7 Speakers? - Paul Joppa 22:32:24 10/13/09 (1)
    Big help - thanks!
    
    "Soft" is unity damping (according to the specs I found through google) at 8 ohms, i.e. an 8 ohm output impedance. An SET on the 16 ohm tap would provide about that much damping. This high output impedance will increase the bass output at certain frequencies (where the speaker impedance is high) by several dB and would be quite an audible difference. You can try the Accuphase at different damping settings to confirm that this is an important parameter in your setup (or discover if it is not).
    
    Most push-pull amps will be pentodes with feedback, and will have a much higher damping factor. There are a few with an adjustable damping control or switch - the Heathkit UA-1 comes to mind. And there are a very few push-pull triode amps with no feedback that would behave similarly to SETs in this respect.
    
    Otherwise you may find a series resistor of up to 8 ohms is needed to get that kind of bass behavior - note this will raise the speaker impedance even higher.
    
    Hope that helps!
    - RE: Is it possible to get Bass control with Tubes and A7 Speakers? - Monte Verdi 07:28:15 10/14/09 (0)
      If I understand what you are saying, is that I should use amplifiers with a 16 Ohm tap and if possible a damping control. I must say I do like damping control on Accuphase and of course there are plenty of 16 Ohm tap amplifiers available. Anymore tube amplifier names would be appreciated with damping control, thanks.
      
      Edits: 10/14/09

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