Nice, thank you.
The drivers arrived yesterday and I'm hoping to source the timber tomorrow so I can get started this weekend!
I've been having trouble determining from photos whether the driver should be slightly sunken in to the baffle or mounted on top - I suppose the primary resulting factor here would be the distance from cone to rear of the cabinet (albiet small). If it's on top I'm considering using a thin (~3mm) facing material for a nice face finish.
The other topic I'm looking for guidance on is the cabinet stuffing as it's not easy to source in Australia. Is it really any different (or different at all) from polyester filling material for cushions, etc.? ei Excel Fibre Hobby Fill
While during my active building days I personally got a bit too anal about rebating all FR drivers for flush mounting, including Fostex FE / FF series with thin stamped metal basket frames, it’s probably a bit OC to insist in applying that to any make / model with a thin and tapered profile external flange such as these. But considering the very shallow overall depth and profile of cone, and the efforts extended to reduce restriction of airflow around the mounting legs and motor assembly, chamfering or radiusing the the rear side of driver opening - particularly with baffle material any thicker than let’s say 12mm (1/2”) - should be considered mandatory.
I’m about to start a frugel-horn build Using the Fostex FE126nv - but have a quick amp question. A KT88 SET amp just became available to me at a great price. The thing puts out about 60wpc. I was intending to use my existing 3.5w TubeCube 7 with these speakers as I’m already using it to drive some BiB speakers I’ve built. Is the 60w too much horse power for these frugel/Fostex speakers?
Sounds like a push-pull amp to me, not single ended.
Well, definitely too much for the little FE126.
jeff
That was my immedite reaction too. A pr of 6550 in PP typically can do 60w, it would take some 8 in parallel for 1 channel SE to have that much power.
The SE EL84 flea watt amp is probably a better match. The Fostex really wants an amplifier with a high output impedance. The KT88 might need t=some circuit tweeking to raise its Rout.
dave
Sound - I built some BiB speakers earlier this year and learned from that experience how important the right amp is for full range, sensitive drivers. Class D was terrible, vintage solid state at 15w was acceptable, and 3.5 watt SET is amazing.
I will want to drive my frugel horns with the best match in terms of amplification and have a great deal on a Jolida amp available. The Fostex is my first choice. However believe the alpair are a little less sensitive and need more to get up and go. Historically I never thought (or heard) that too much power was a bad thing but this step into sensitive speakers has turned that notion on its ear for me. Thanks!
If you’re not already committed to the drivers, I’d heartily endorse the Mark Audio over the Fostex. Depending on which Jolida amp, power would be more than sufficient. FWIW, although it’s been quite a while since it was in my own stable of amps, the 302 can easily be modified for triode operation. Still not the luscious seductive midrange of a DHT such as 300B, 2A3, or for the true hairshirt masochist 45, etc.
You would be surprised at how well even 10 nice watts will do, and if the room is smallish and you don’t push hard you can get away with less. They are somewhat amplifier agnostic but do beenfit from high quality amplication.
TheFFxx5wk are close in that respect, FExx6 prefer a high output impedance amplifier Iike your little SE).
dave
Yeah, you put me over the edge. A set of Alpair 7 MS are on the way from Madisound. I've gathered all my supplies and just need to buy a sheet of MDF as soon as the weather clears. I'll try to document my frugal horn build for posterity and post the results here. I've culled through as many finished photos as possible and think I have my aesthetic design nailed down. I'm hoping for a painted finish... but if it turns to crap, some wallpaper will be my fall back. This thread has been awesome for gleaning tips and ideas. The amazing plans do the heavy lifting though - I'm really looking forward to this build... and the final product.
FWIW, I missed out on the Jolida amp. Currently eyeing the MP-301 from Musical Paradise. But first, I'm going to focus on getting the speakers built and see how they sound with my TubeCube7. I'm happy with my BiBs, but my fingers are crossed that these quality drivers and this type of rear-facing horn work better in my main room. The BiBs were my gateway into high sensitivity horn loaded speakers... so I'll relegate them to the office or bedroom. I'm not so sure about the Dynavox drivers used in that build being able to hold a candle to the Alpair drivers based on the things I've read.
Happy Holidays!
Hey Dave - From what I’ve seen, it seems like a toss up between MDF and Ply. I am not convinced either is better than the other. Since I don’t intend a stained wood finish and MDF is nearly $40 less, I planned to go with that. Sounds like you recommend ply. What are the advantages of ply (or pitfalls of mdf). Thanks.