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-   -   Bi-amplification and Fostex 168e Sigma (http://www.diyaudio.com/forums/full-range/180234-bi-amplification-fostex-168e-sigma.html)

jaylgordon 2nd January 2011 02:08 AM

Bi-amplification and Fostex 168e Sigma
 
I am wondering if this set-up will be fubar or really sweet:

First, I have a pair of Fostex 168e Sigmas in the following recommended cabinets:

https://www.madisound.com/pdf/fostex...ez_enclrev.pdf

I run these with an Acurus A150 (150 wpc), which I know is not a great match. So I've ordered a T-amp through Sure Electronics (15wpc):

2*15W @4? TA2024C Tripath Digital Class-D Audio Amplifier with Case & 12V PSU Free Shipping (AA-AB341)_Audio Amplifier and other Audio Boards_RF and Audio, Video Equipments_Sure Electronics' Webstore

Now, I have a pre-amp with two outputs (Melos MA111, which I love, esp. for its phono stage), so I was thinking I could run the T-amp and the Fostexes from one output and the Acurus and a pair of woofers from the other output. For woofers, I was thinking of these, perhaps in the corresponding open baffle kit:

Silver Iris OB 15 Augie [SI-OBA-15] - $165.00 : Zen Cart!, The Art of E-commerce

My worries:

1. Mismatches due to the amp differences and/or the vastly different efficiencies of the speaker drivers (Fostexes-- 94.5, Augies-- 88.7).

2. Crossover issues (do I want crossovers for both the Fostexes and the woofers here, or just one or the other, or neither?)

3. Aural dissatisfaction. I like 1950s and '60s jazz. I like bass "snap"-- plucking of the string bass, bass drum thumps, etc-- but I don't care for the earth-shaking-but-muddy sound of most subwoofers. I like "presence." I feel like I'm missing some of that since the Fostexes just do not have much bottom.

Thanks for any suggestions or advice.

Jay

Bemopti123 2nd January 2011 03:08 AM

SS amps usually have too much damping for things such as Sfullrange drivers on horns. I say try a tubed amp and see whether that missing bass returns. I myself have a 208Sigma based horns that had not given me too much pleasure until I put a SET amp to drive it.

I did read somewhere in the LansingHeritageSite that a member had decided to put a component in the amp end (SS) when driving vintage (1950s-60s) JBL amps due to what I have had described.

chrisb 2nd January 2011 05:40 AM

Quote:

Originally Posted by Bemopti123 (Post 2418196)
SS amps usually have too much damping for things such as Sfullrange drivers on horns. I say try a tubed amp and see whether that missing bass returns. I myself have a 208Sigma based horns that had not given me too much pleasure until I put a SET amp to drive it.

I did read somewhere in the LansingHeritageSite that a member had decided to put a component in the amp end (SS) when driving vintage (1950s-60s) JBL amps due to what I have had described.


Since you're already thinking about changing the amp, I second the vote on trying at least a couple of tube amps with almost any Fostex, and most particularly a Sigmas in a BLH before confusing things by adding woofer(s) & additional amps - get the "wide-range" part of the system dialed in first. If you're game to try a DIY/Kit, something like Decware (EL84 "family" ), Bottlehead Stereomour ( 2A3 / 45 DHT)or Tubelab Simple SE - much wider range of output types optional.

Decware:
Amp kits

Bottlehead:
Stereomour Stereo Single Ended 2A3/45 Integrated Amplifier Kit

Tubelab:
Simple SE

sreten 2nd January 2011 03:36 PM

Hi,

With 150W on tap its very easy to simply try series resistors of various
values to hear the effects of having valve like high output impedance.

rgds, sreten.

jaylgordon 2nd January 2011 05:17 PM

Thanks for the tips about damping, and the advice about tube amps. When I built the Fostex speakers, I'd planned to build a 2A3 amp, too, but I never found the time to do it. I was sort of hoping the T-amp (based on the famed, or maybe fabled, Tripath 2024 chip) would deliver the tube-like sound at a rock-bottom price (I've got a family now, so it's harder to justify shelling out $750 for a tube amp kit, appealing as it may be otherwise). The T-amp wouldn't necessarily address the damping issue, though.

sreten 2nd January 2011 08:12 PM

Hi,

You can also modify the feedback loop of any amplifier to give output resistance.

rgds, sreten.

chrisb 3rd January 2011 05:35 AM

jay;

if it's not too late, take a look at the Virtue amps

Virtue Audio. We make audio lovers audiophiles. Better sound by design.

my son bought one a few months ago to drive a pair of Mark Audio CHR70s bookshelf cabinets in a small bedroom system, and it's by far the best of half a dozen or so class T amps I've heard

danerius 3rd January 2011 09:15 AM

Quote:

Originally Posted by sreten (Post 2418924)
Hi,

You can also modify the feedback loop of any amplifier to give output resistance.

rgds, sreten.

Even a T-amp?

Regards /Bo


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