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Bass response...  Tube rolling? (Read 6424 times)
alper_yilmaz
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Bass response...  Tube rolling?
12/29/11 at 09:23:33
 
Hi All,

I have an SE34I.2 which I run into Omega Loudspeakers 97dB-efficient Hoyt-Bedfords.  Volume-wise, I am not having any issues; it is more than enough.  However, I am not happy with the bass response in general.

In front of the SE34I.2, I have a CSP preamp.  I have tried both 6922's and 6N1P's on the pre.  Before the CSP, I have a Hegel HD20 DAC and a Mac Mini as the source.

On the SE34I.2, I have tried both Mullard NOS GZ32's and some Raytheon and Sylvania 5U4GB's.  As far as the output tubes, I have tried the stock Mullard EL34's and the fat bottle EH 6CA7's.  I am using 6N1P's for input tubes.

What else would you recommend for improving the bass response?  Which of the tubes (input, output, and rectifier) have the most effect on the bass?

Thanks in advance for all the responses.  Happy new year!

Alper
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Lon
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Re: Bass response...  Tube rolling?
Reply #1 - 12/29/11 at 13:26:05
 
Hi Alper!

Well, it seems to me that you should be getting pretty good bass on the Integrated as is. Have you tried 6N2P tubes at input? They sacrifice some headroom, but give a very warm sound and more bass in my experience. Also. . .how are your amps situated? I found hidden bass in my setup when I moved to using Herbie Audio Labs' "IsoCups"--these improve all aspects of the sound on my amps for me, including giving me a better defined, more audible bass spectrum.
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alper_yilmaz
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Re: Bass response...  Tube rolling?
Reply #2 - 12/29/11 at 14:40:53
 
Hi Lon,

Thanks for the quick response.  I have not tried the 6n2p's in my system.  I remember using them in my SE84s and being very happy, but when I sold them, the tubes went as well.  I will definitely give them a try next time I can have a hand on them.

I will definitely look into the IsoCups; actually this is the first time I have heard about them.

Best,

Alper
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Lon
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Re: Bass response...  Tube rolling?
Reply #3 - 12/29/11 at 14:55:29
 
They're worth checking out. The Herbie's Audio Lab "Tenderfeet" also work well and will bring out the lower end, but with tube amps I find the "IsoCups" are a better fit.

http://herbiesaudiolab.net/compfeet.htm
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Pale Rider
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Re: Bass response...  Tube rolling?
Reply #4 - 12/29/11 at 17:04:52
 
Here's another vote for the Herbie's Iso-Cups. I have those, their Tenderfeet, and the MIGs. Overall, the best results for me have been the Iso-Cups under my Toriis and Ultra, then the SE84ZS and Taboo (headphone amp only, so less microphonics and feedback). But I also got much clearer, tighter bass out of my ERRs with the screw-in dampener/slider feet. On my source boxes, all the devices help, and the differences between them are less obvious.
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Pale Rider
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Re: Bass response...  Tube rolling?
Reply #5 - 12/30/11 at 06:27:05
 
In my archives, I found this link to a DIY discussion about bass response of various 6922 type tubes.
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alper_yilmaz
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Re: Bass response...  Tube rolling?
Reply #6 - 12/30/11 at 21:43:39
 
Thanks Pale Rider...  Best,

Alper
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ski bum
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Re: Bass response...  Tube rolling?
Reply #7 - 12/31/11 at 14:19:36
 
Hello Alper, and welcome to the forum!

Not to dissuade you from shopping Herbies or trying different tubes, but it seems that the more direct way to address your problem is with speaker placement.  Have you tried relocating them closer to room boundries, i.e. closer to the back wall?  That would yield several db gain in the bass, and as a bonus, it's free!



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Pale Rider
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Re: Bass response...  Tube rolling?
Reply #8 - 12/31/11 at 19:17:37
 
I am not sure that Alper said he wanted a gain in bass. If he does, then sure, speaker placement should be able to raise or lower bass reinforcement. And you're right, it's free. But that's not the same as good bass.

Proper speaker placement is always the right place to start, but once you have that box checked off, I think you have to start asking yourself how deep you might want to go into bass management. Room treatment can be a huge factor, but effective bass traps might not be an option.

I followed a series of articles recently that convinced me I needed to start actually measuring bass response in order to understand the macro factors of the room, size and contents. Then, build (read "have built"; I am no carpenter) servo subs roughly to meet the needs of the room, then break all that in, re-measure, adjust the subs and their amps, and then start playing with tubes.

FWIW, I love the ERR bass. It is amazingly good for a speaker of its modest footprint. It is more than satisfying, but few speakers can do the full 20-20 as well as a sub-integrated system.
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ski bum
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Re: Bass response...  Tube rolling?
Reply #9 - 01/02/12 at 15:54:37
 
Let's get real here.  No amount of tube rolling or isolation devices will provide more power, extension, or alter damping characteristics from an SE34i, nor change the inherent qualities of the OP's Omega speakers, and those are the limiting factors for his system's bass response.  

Maybe the impedance load in the bass region that the Omegas present is less than ideal for power delivery from the SE34.  I know my little Zens like low impedance speakers, and if the SE34 has the same output trannys using the same taps, it's no wonder the results with a >8ohm load like the Omegas are less than spectatular.  If that's the case, and I could be wrong, the OP would be better served having Steve install the higher load friendly EX trannys or using an autoformer to cut his impedance in half than spending money on tubes and damping devices.

I think more assessment of the problem is in order, as Alper only said he is "not happy with the bass response in general", which could mean just about anything.  

So Alper, could you be more specific with the problem?



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« Last Edit: 01/02/12 at 16:11:01 by ski bum »  
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Pale Rider
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Re: Bass response...  Tube rolling?
Reply #10 - 01/02/12 at 16:55:24
 
Quote:
I think more assessment of the problem is in order, as Alper only said he is "not happy with the bass response in general", which could mean just about anything.


Agreed.
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alper_yilmaz
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Re: Bass response...  Tube rolling?
Reply #11 - 01/03/12 at 11:38:07
 
Dear Ski Bum and Pale Rider,

Thanks for the in-depth discussion; this really helps.

I have not played much with the placing of the speakers, but I think I am benefiting from some mechanical coupling as they are currently located closer to the wall, but I need to experiment more with it.

Unfortunately, I do not know the impedance curve of the speakers at bass frequencies.  I know that the vented freq is from 38hz to 18khz and they are 8 ohms, but I do not have more information other than what is provided on the Hoyt-Bedford website.

What I mean by "not being content with the bass response" is simply based on my experience with my Torii mkII, which has very good bass even with inefficient speakers at 91dB and complex crossovers.  I know that SET amps are known for their spectacular mids and highs, and because of the resolution of the amp and the speakers, every single detail including the bass is heard fine, but the system sounds a bit imbalanced, less pronounced in bass, and much more present in mids and highs.

I am not sure if this is good enough explanation though...  :(

Thanks again.  Best,

Alper
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ski bum
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Sounds like you've found the SE34's Achilles heel
Reply #12 - 01/03/12 at 18:36:05
 
I think I know what you're hearing.  Bear with me here, long post...Torii II to SE34 is a big clue.

Listen carefully in the bass.  You mentioned the slightly prominent midrange relative to the bass.  Do kick drums seem to have extra impact, punch, or presence, with otherwise laid back bass response?  

Does this describe what you're hearing?

If so, you could be experiencing the effects of higher output impedance than you're used to.  With the lower damping factor of the SE34i I would expect the bass response to be slightly reduced (maybe a couple db) compared to the midrange, and a couple small but notable peaks (that crest at levels near that of the midrange) that correspond to the cone's resonant freq and the port's resonant freq.  This is the fairly typical way high output impedance amps behave with ported/reflex enclosures.  This stands even if the power delivery from the SE34i to the Omegas is ideal.    

The port resonance point should not be too much concern, as the speaker is likely rolling off by that point, so it will tend to extend the reponse you get.  The woofer resonance is probably an octave or so higher, and non-linearity will be more noticable (for example, extra presence on kick drums for would be a peak somewhere from 70-100hz).    

On my speakers, which I can reasonably presume present a much wilder load as far as impedance/phase goes, the deviation from linearity is still only about +/-2.5db (as measured at the speaker terminals with amp connected).  I actually have a jpg of that, if I could figure out how to attach it here, it would go further than my convoluted explanation.     

I would expect a more SET-friendly purist speaker like your omegas would have much less deviation than what I use, but the non-linearity is the nature of the beast with the higher output impedance.  To cure it would require applying negative feedback, and possibly more gain stages or other complexity in the amp, which would rob it of it's uber clarity/transparency.

You also noted something I have also observed, that the SET detail and tone is all there in the lower registers, even if the response is slightly attenuated and a little lumpy/peaky.  That's the rub.  The detail and tone is addictive, and you don't want to do without it.  

One thing you may consider doing which would preserve all the SET goodness and directly help cure your bass is simply adding a decent sub.  Feed it speaker level inputs so it get's the Decware sonic signature.  You'll extend your response much deeper, and smooth out and firm up the midbass at the same time.

Check out Rhythmic for high value, high performance, well damped ('fast' sounding) subs that can keep up with your Omegas.  I think their 15" sealed job is going for only $500 right now.
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« Last Edit: 01/04/12 at 01:02:25 by ski bum »  
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Lon
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Re: Bass response...  Tube rolling?
Reply #13 - 01/03/12 at 19:47:59
 
SB,

Very interesting observations. Thanks for sharing.
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Decware:ERR,HR-1,ZP3,CSP2+,Torii Mk III,PS Audio PWT+DS,PowerBases,PPP,AC-12 pcs, Denon DVD-A1UDCI, Rega RP3 +TTPSU,white belt+Exact2, VooDoo Cable:Stradivarius, Ultra Linear+Evo ICs, Iso-Pods,Mapleshade:Double Heiix Plus,Samsonv2+v3 +4" platforms,Herbie's Iso-Cup
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opnly_bafld
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Re: Bass response...  Tube rolling?
Reply #14 - 01/04/12 at 02:00:44
 
Interesting, I have a pair of Type 1s (48hz) paired with an EL84 SET amp and I'm actually a bit surprised by the amount of bass (FWIW EL34s do have a reputation of being a little soft in the bass).

Have you considered a Type 3?

Lin
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