Frugel-Horn Mk3

Thanks for the input guys,
Im not sure what you mean by a Butchers block Dave,I have some stair treads made from strips of wood glued together ?about 2 inches x 1 inch thick) to make the tread. These do not move !!No opening of the joints etc. Im thinking solid wood would give a better and easier finish,but I dont want to compromise the sound at all !!
 
strip or even block core lamination of solid wood

An externally hosted image should be here but it was not working when we last tested it.


or for real "butcher" work


butcher-block.jpg
 
I'm trying to figure out if the Frugel-Horn Mk3 would be a good choice for the amp I am building at the moment. I would probably buy the recommended Fostex driver.

It will be a 20W or so push-pull tube amp without a global feedback loop. The thing I am concerned about is that the output transformers are small and have somewhat high DCR in the windings. The secondary is about two ohms, so I am guessing that the amp will have a 3-4 Ohm Zout when all is said and done if I follow my current design plan.

Will the Frugel-Horn Mk3 work well with this amp or do I need to re-work the amp design for a lower Zout if I want this combo to work well?
 
I think there are 2 separate issues here - with that much P/P power, you have options of a wide range of drivers that have been quite successful in the FH3 - the Fostex FE126 and Alpair7.3 are the two with which I'm most familiar. While more costly, if your budget can be stretched, I'd strongly recommend the A7.


As for the damping factor question, there are other experts that can address that one.
 
Since I haven't built the speakers yet, I am flexible on those things. What I want to determine here is whether or not I need to alter the amplifier design in order to make some combination work.

So what I want to determine is, can I get good results with this speaker design and one of the driver options with an amplifier that has a 3-4 Ohm Zout? Or should I change the amplifier design to get that Zout lower by using some sort of feedback loop around the output transformer?

I need some guidance on this to determine the design approach on the amplifier. I am flexible on damping and driver choice.
 
Ah yes, the interface between a FR driver and tube amps can be quite a delicate slow waltz - which I vaguely remember as being quite enjoyable, once the two partners establish their embrace and rhythm. " No, honey my phone is in my jacket pocket"

There are lots of folks driving Alpairs with SETs of lower power than your planned design, so while the Fostex FE126EN might make most sense in terms of matching to amp's damping factor, with additional damping below the driver, the Alpair will work perfectly fine. Unfortunately, there aren't precisely calculated values of acoustic damping that can be guaranteed to yield optimal results for all systems / rooms.
 
frugal-phile™
Joined 2001
Paid Member
If the amp has a high output impedance you are usually looking to use a speaker with high mechanical damping and a flattish impedance curve. The other factor is that the final system output has the amplitude of the source convolved with a function of the impedance curve -- the magnitude of that function largely determined by the size of the output impedance.

So one can add damping to the box to increase the mechanical damping of the system. And one can also consider that the rise of impedance at LF & at HF combined with a highish output impedance amp can raise the system amplitude in those places where it would normally fall off (if driven by a low output impedance amplifier)

dave
 
I'm not Dave, but my personal favorite driver in the FH3 is the Alpair 7, and particularly its special edition version the MAOP7 - which very few folks outside of Japan have experienced.

While I don't play any of my tube amps that much these days, the one that does get the most use is an EL84 P/P pentode, using vintage Scott LK48 OPT- no issues of over- ripe bass with either if the 7s on that combo
 
They will no longer be Frugel-Horns -- you are on your own. Likely lessbass and more ripple.

An Irish firm has completely removed the final part of the mouth after the choke and it seems to work OK (at least according to the review)

dave

Getting the feet wet with speaking building and the FH3 has piqued my interest for a few reasons. 1. seemingly relative ease of build, 2. interesting design (maybe similiar to some designs but different in aesthetics from what I have seen) 3. a dedicated community following its progress and 4. committed designers.

I, like a few members have mentioned before, have space restrictions in the listening room. And I understand that the design was intended, as-is, for a particular speaker(s) and if altered will not perform the same. Speaker design and theory is a new subject for me and I've been trying to read up and comprehend everything available but this head is only slowly absorbing the information.

So I have a few questions. Firstly, I too would like to "shave off" a little depth. What would be the net effect of shortening the depth by say 1.50-2.00" but widening/flaring out the mouth base accordingly to compensate for the loss of depth of the mouth? Or is the volume of the mouth not as important as the shape with respects to the bass and ripple? Secondly, I read how the FH3 was designed to utilize a corner or wall behind the speaker. What kind of minimum distance are we talking about? Also, if a corner increases the mouth size 8 fold (from the original FH introduction page), could one build a "corner" behind it? Where the diffuser protects from sound waves bouncing back into the mouth, how about a 90 degree "corner deflector" facing the mouth to act like a real corner? How much does the flat wall aid the mouth?

I plan on getting Markaudio CHR-70As and I'll be running them with a Dynaco SCA35. Will those speakers work nicely with the design (I imagine the plans are for an earlier series CHR-70 since the plans date back to 2012.) If this combo is not up to par, I would appreciate a suggestion of another design. I saw the Pensil being mentioned. And the CHR-Ken look appealing. Perhaps the Coniston; would they even work well with the CHR70A? I was eyeing that speaker first but can't really find a pair of the CSS EL70's.