Lowther Fidelio MkII

fasterbyelan

Member
Paid Member
2009-10-01 4:36 pm
Towcester
I am considering building a pair of speakers using a pair of Lowther PM2A’s. Having spent some time looking at various designs, which would meet my physical and visual requirements, the Lowther Fidelio MK II looks to be suitable. I do have some questions about the design and with reference to the drawings below, can anyone answer the following –

Location Ref A – What is the purpose of this channel?
Location Ref B – What purpose does this (trap?) serve?
Location Ref C – There is a square hole in this panel, what does it do?
Horn Construction - Is there anything to be gained by putting a radius on the sharp points?

Has anyone experience of using this speaker, it is difficult to get any info on the web? It does seem to have a reasonable low end response (50Hz) from what I have read. And how close to the rear wall does it need to be located?





Thank you,
 
Having no experience with Lowther cabinets at all, here is my opinion on Area A. Since none of the interior pieces of A appear to be flush against the top, front, or back walls, apart from providing additional bracing and further defining the horn path, it is the channel for your speaker wire.
 
The various Empty spaces could well be Hemholtz traps to deal with the lowest resonances in the too small a horn.

I have not heard these, but it is hard to get bass out of Lowthers, and this horn, by all reports, is no exception.

If one is going to add woofers to get bass, then one has to consider what is “housing” the Lowther. There have been great results (again reportably), with 2-way OBs.

dave
 

fasterbyelan

Member
Paid Member
2009-10-01 4:36 pm
Towcester
Thank you all for your replies and thoughts on the questions I raised. In response –

Ref A – Why is a vent required?

Ref B – This does seem to be an absorption chamber (ref AJ Horn). I need to better understand why this is needed.

Ref C – Would this be an addition absorption chamber designed for a specific band of frequencies?

And rounding the corners is not recommended as they help attenuate the higher frequencies!

I’m getting up to speed with speaker design, as such my present feelings about the Fidelio is that it is overly complicated (most Lowther cabinet designs are!). Hence, I would be better placed to either look at simpler design or, as Dave suggested, design my own. Martin King’s Quarterwave web site is a terrific resource and my understanding of rear horn design has been greatly enhanced; it’s a shame the MathCad worksheets are no longer available. Hence, what speaker design software is recommended?

Regards,
 

fasterbyelan

Member
Paid Member
2009-10-01 4:36 pm
Towcester
Some investigation into the above questions has resulted in an answer to Ref A.

Lowther used the second passage in several designs; it is what they called the ‘Bicor’ effect. This is described by the manufacture thus –

"Another Lowther exclusive. Its application to Lowther's labyrinthine horn formations has been to eliminate the barrier effect of standing waves in horns completely, leaving cleaner, clearer musically transparent sound as a consequence" - sound like sales talk to me! (See here for further discussion)

It is also mentioned on this thread, Scottmoose providing a more technical response –
Regarding what Lowthers are up to with their Bicor cabinets, they're presumably employing a tuned Helmholtz cavity / resonator to fill in a harmonic null; probably F3 or F5.
 
I should have added 'or damp' to that remark.

There's no real mystery in terms of broad physics; I haven't got any measurements of the design itself, but the principle of using QW stubs and / or Helmholtz resonators to acoustically address a given frequency or frequencies is in itself sound. Internal chambers of various types are nothing new; plenty of examples of those, although it's rarer that they vent to the outside.
 
I’m getting up to speed with speaker design, as such my present feelings about the Fidelio is that it is overly complicated (most Lowther cabinet designs are!). Hence, I would be better placed to either look at simpler design or, as Dave suggested, design my own. Martin King’s Quarterwave web site is a terrific resource and my understanding of rear horn design has been greatly enhanced;

As an example, designed for PM4A is the only (finished) Woden Horn down for Lowther and it is for the PM2A. You will note that it is much simplier, is longer, bigger, and the mouth size is much, much larger. It is much less compromised than the Fidelio. And it is modeled, not guessed. I suspect that the next ones will follow the Vulcan/Avebury model and gain from the rear mouth loaded into a wall or corner.

Blienheim-c-3D.gif


Woden Design | Blenheim

dave
 

fasterbyelan

Member
Paid Member
2009-10-01 4:36 pm
Towcester
I should have added 'or damp' to that remark.

There's no real mystery in terms of broad physics; I haven't got any measurements of the design itself, but the principle of using QW stubs and / or Helmholtz resonators to acoustically address a given frequency or frequencies is in itself sound. Internal chambers of various types are nothing new; plenty of examples of those, although it's rarer that they vent to the outside.


Yes, the venting was the unusual aspect hence the question

Anyway thanks for your responses, I have a better understanding of this speaker (and its possible shortcomings!).
 
One can likely do better with a good modern modeler. Still at this size getting bass is an issue.

+1

It would be nice to see the new Lowther owner (I read somewhere it changed hands) publish a 2-way modern design. I guess their reluctance is partly due-to having no supporting bass driver (yet ?).
 
I suspect it's more likely that nobody has asked them to, rather than reluctance. And in fairness, Lowther is a very small company with finite resources, so they'll likely have to prioritise on the core product, at least initially. Designing an LF driver is also rather different to designing a wideband; AFAIK Lowther have never really done one, and even for a low-volume, high-margin business model, they'll need to carefully consider whether the returns will match the investment.
 

Randolf

Member
2021-02-05 9:15 am
Hi,

I have been using Lowthers for many decades. Last year I switched to the Fidelio MKII cabinet. From my perspective it is one of the best reasonable sized cabinets for a single Lowther drive unit. I had some problems to get it to work well in my living room but finally I succeeded. On Lowther Fidelio in my living room - homeaudios Webseite! I have summarized my results with lots of measurements and comparison to a Quad Z-1.
 

tarnhelm5

Member
2018-07-30 5:26 pm
‎Hi,‎
‎ ‎
‎ I've been using Lowthers for decades. Last year, I changed it to a Fidelio MKII cabinet. From my point of view this is one of the best sized cabinets for a single Lowther drive device. I had some issues getting it working in the living room, but it finally succeeded. ‎‎Lowther Fidelio-homeaudios website in my living room‎‎! I summed up my results with a lot of measurements and comparisons with quad Z-1.‎
‎Hello Randolph! ‎
‎ I went into the link you were linking to and took a closer look. ‎
‎ A notch filter is a part that connects directly to the driver. ‎
‎ Using bad quality also damages the sound quality. ‎
‎ Impedance calibration circuitry has little impact ‎
‎ . The resistance that goes into the notch filter, the quality of the capacitors and coils is fatal. ‎
‎ Start by upgrading the cement resistance you used. ‎
‎ You'll know that it's starting to come out of Keddock or Mundorf on the heatsink. ‎
‎ Good luck. ‎
‎ Hi,‎
‎ ‎
‎ I've been using Lowthers for decades. Last year, I changed it to a Fidelio MKII cabinet. From my point of view this is one of the best sized cabinets for a single Lowther drive device. I had some issues getting it working in the living room, but it finally succeeded. ‎‎Lowther Fidelio-homeaudios website in my living room‎‎! I summed up my results with a lot of measurements and comparisons with quad Z-1.‎
 

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