This is an interesting thread as I have been thinking the time might be approaching for a new speaker project. I'm currently using Lowther EX4s in Ketil Parow's 'AllFun' BLH cabinets, having built them some 8-9yrs ago. I really like the AllFuns and my motivation for a new project is simple curiosity and 'because I can' rather than any dissatisfaction.
Scott's Vulcan design looks interesting and within my skillset, though I would really like to stick with my Lowthers. A couple of questions about the Vulcan (and its ilk); what location are they intended for with respect to corners/back walls and might my room size, about 16ft x 14ft. allow them to work well.
Cheers
Ray
Scott's Vulcan design looks interesting and within my skillset, though I would really like to stick with my Lowthers. A couple of questions about the Vulcan (and its ilk); what location are they intended for with respect to corners/back walls and might my room size, about 16ft x 14ft. allow them to work well.
Cheers
Ray
Hmm, based on published specs, the upper mass corner is much too high for some of us folks in a BLH app [nearly 2x for me], so wondering how accurate they are and/or how much, if any, series R was assumed.
TIA,
GM
I've been doing a little research into this potential project today and came across this interesting drive unit variation on a Kirishima build;
https://www.jet5.com/kirishima.php
Anyway, I also saw the Blenheim on the Woden site so perhaps a lowther project to consider but similar questions as before regarding location with respect to corners/back walls and suitability for my room.
https://www.jet5.com/kirishima.php
Anyway, I also saw the Blenheim on the Woden site so perhaps a lowther project to consider but similar questions as before regarding location with respect to corners/back walls and suitability for my room.
I can't comment about the ilk, but as far as the boxes of that type I designed, optimal is corner-loaded, about 2ft from the front wall & 1.5ft from the sides. However, this is assuming 'ideal' conditions: perfectly solid / reflective walls &c., so there is always some variability, and I designed them to be reasonably flexible -sufficiently so that you should get good results with 1/4 space (front wall) loading. Rooms being what they are (i.e. a royal pain), I would never guarantee that any speaker will give perfect results, but they're fairly forgiving.
Depends on what you mean by 'better'. They're different. Jan clearly had almost the reverse design philosophy to myself, which is fair enough. I can't speak for him, but the condensed version of my perspective runs something like this:
Back horns are no different to any other back-loaded design: they're only useful over a relatively narrow BW -about 300Hz (give or take, but suffices as a broad ROT) is the limit. If you try to run them higher, you start to run into chronic GD issues. I prefer to use the folding scheme as a functional part of the low-pass filter. Smooth curves are attractive and promote maximum efficiency over the horn's full BW. The trouble with that route is that you don't necessarily want maximum efficiency over the horn's full BW. Smooth curves tend to have their greatest effect on the shorter wavelengths near the top end of its functional range -right where you want to start rolling the thing off. The wavelengths of the LF range, by comparison, are too long to be especially troubled by sharp bends and angles. Varies from design to design of course, but that's the general principle. Makes it easier to build too.
You do? I respectfully can't agree with that. It depends on the specific design and the driver it uses. Assuming you have a driver with an effective mass-corner (once any series R is factored in) that is reasonably low, you can run the bass horn down a fair old way without having a gap between the effective mass corner roll-off of the driver and the upper corner frequency of the horn. Therein is the issue though -there is still a widespread belief that a low Q driver is required for horn loading. It isn't. That's a partial misunderstanding of the original systems -most of the attention seemed to focus on the drivers, without noting the variable output impedance of the amplifiers, which was a functional part of the system design & its OA response.
Thank you Scott, that is helpful and I appreciate there are no guarantees with this sort of project. I live in a Victorian house so corner walls are solid brick built with plaster over.
And if I were to go the Lowther route (Blenheim), the images I've seen of your similar front mouth designs suggest that they're OK closer to the wall behind them?
Ray
BTW, I was only meaning the Victor and the Valiant.
Hi!
I used to own Sachikos which are essentially Kirishimas before Scott made some improvements to them. I tried Lowther DX4 and DX3 in the Sachikos and they sounded terrible. The Fostex FE206E, FE206ES-R and FE208ES-R all sounded much, much better in these cabinets. So if I was you, I'd build Scott's Blenheim cabinets that are designed for Lowther speakers over building the Kirishimas! That's just my 2 cents worth of advice...
Thetubeguy1954 (Tom Scata)
Hi Retsel! Yes, I was referring to Paul Butterfield. I actually don't know what Paul's using these days. I haven't seen him in well over a year now! I do know that Paul's health is not good these days. Sorry I couldn't help more.
Thetubeguy1954 (Tom Scata
Can someone please explain what this upper mass corner that GM and Scottmoose are talking about when GM says "the upper mass corner is much too high for some of us folks in a BLH app nearly 2x for me" and Scottmoose replies: "And me. I assumed about 2.5ohms - 4ohms as a ballpark figure that would cover a broad spectrum of SET amps?"
Perhaps I should know about this but I'm completely at a loss! So I'd appreciate a fairly simple explanation of what "upper mass corner" refers to and how it pertains to the Vulcan cabinets I will be building to replace my Sachikos!
Thanks, Thetubeguy1954 (Tom Scata)
Perhaps I should know about this but I'm completely at a loss! So I'd appreciate a fairly simple explanation of what "upper mass corner" refers to and how it pertains to the Vulcan cabinets I will be building to replace my Sachikos!
Thanks, Thetubeguy1954 (Tom Scata)
The mass corner of a moving coil drive unit is taken as 2F0/[effective]Qt) and defines the transition from the driver's acceleration (rising response) BW to the mass-controlled (flat) BW.
Driver Qt varies depending on any series R present or the output impedance of the amplifier, hence the caveat 'effective Qt'. Most SET amps tend to have an output impedance of 2.5 - 4ohms or so, significantly raising the system Q compared to the raw driver itself if driven by a pure voltage source.
Back horns are like any other type of back load: they're only usable over a relatively narrow BW. Depending on the path length, 250Hz - 300Hz is about the limit to keep GD reasonable. So if the driver's effective mass-corner [Fhm] is higher than that you either need to get some series R on it to lower the mass-corner, or use a short front midrange horn to 'fill in' the gap between the driver's mass corner and the upper corner frequency (acoustical / mechanical low pass) of the horn (confusingly, also often termed Fhm). Ideally, you design your enclosure knowing what the effective Q will be; in the absence of that, a fudge-factor is usually worth having.
Driver Qt varies depending on any series R present or the output impedance of the amplifier, hence the caveat 'effective Qt'. Most SET amps tend to have an output impedance of 2.5 - 4ohms or so, significantly raising the system Q compared to the raw driver itself if driven by a pure voltage source.
Back horns are like any other type of back load: they're only usable over a relatively narrow BW. Depending on the path length, 250Hz - 300Hz is about the limit to keep GD reasonable. So if the driver's effective mass-corner [Fhm] is higher than that you either need to get some series R on it to lower the mass-corner, or use a short front midrange horn to 'fill in' the gap between the driver's mass corner and the upper corner frequency (acoustical / mechanical low pass) of the horn (confusingly, also often termed Fhm). Ideally, you design your enclosure knowing what the effective Q will be; in the absence of that, a fudge-factor is usually worth having.
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Thanks Tom. If I do proceed with a build it will either be Vulcans with Fostex units or Blenheims with Lowthers; best to stick along the lines of what the designer intended.
That said, I would be interested in Scott's view of substituting the Fostex FE208E Sigma and Fountek ribbon tweeters in the Vulcans, as per the link I posted above.
Ray
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I'm with Tom here, too much terminology being used without much explanation makes it all too confusing.
"the driver's acceleration (rising response) BW" - what the heck does this mean ?
Is this the frequency range below the natural resonance of the driver-suspension system - where the behaviour of the driver motion is dominated by the stiffness of the suspension since at low frequencies it's relatively easier to accelerate the small mass of the driver whereas the stiffness of the suspension has to be overcome ?
What is "BW" is it band-width ? do you mean frequency response ????
"mass-controlled (flat) BW" - and what is this ?
Is this the frequency range above the natural resonance of the driver-suspension system, where the inertia (mass) of the driver dominates it's behaviour because at the higher frequencies it gets harder and harder, relative to the suspension stiffness, to 'wiggle' the mass of the driver ?
I get that below resonance the SPL falls off, whereas above resonance its relatively flat. So you want the horn to help raise the response below resonance and hence the 'mass corner frequency' where the speaker driver response changes behaviour needs to match, in a appropriate manner, the frequency range over which the horn changes the load on the driver in order to increase the response ? - am I getting any of this right ?
"the driver's acceleration (rising response) BW" - what the heck does this mean ?
Is this the frequency range below the natural resonance of the driver-suspension system - where the behaviour of the driver motion is dominated by the stiffness of the suspension since at low frequencies it's relatively easier to accelerate the small mass of the driver whereas the stiffness of the suspension has to be overcome ?
What is "BW" is it band-width ? do you mean frequency response ????
"mass-controlled (flat) BW" - and what is this ?
Is this the frequency range above the natural resonance of the driver-suspension system, where the inertia (mass) of the driver dominates it's behaviour because at the higher frequencies it gets harder and harder, relative to the suspension stiffness, to 'wiggle' the mass of the driver ?
I get that below resonance the SPL falls off, whereas above resonance its relatively flat. So you want the horn to help raise the response below resonance and hence the 'mass corner frequency' where the speaker driver response changes behaviour needs to match, in a appropriate manner, the frequency range over which the horn changes the load on the driver in order to increase the response ? - am I getting any of this right ?
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Sound power decreases with increasing frequency at 1/f; IOW, the frequency sound 'bubble' shrinks exponentially, ditto its radiation impedance.
The driver piston's acceleration [rising response] then must decrease at the same rate to maintain a flat frequency response and at some frequency its radiation impedance matches the driver's mass [Fhm], ergo it now controls the response and decelerates at 1/f to maintain a flat response due to its mass is increasing relative to the sound power.
Below Fs then, acceleration must increase at 1/f, so at some point [Flm] it can no longer provide enough radiation impedance, ergo Fs is the mean of the Flm - Fhm bandwidth [BW].
Note that all basic T/S box alignments peters out at Fhm; IOW the box no longer has any loading control over the rear of the driver.
I think I remembered that right...........
GM
The driver piston's acceleration [rising response] then must decrease at the same rate to maintain a flat frequency response and at some frequency its radiation impedance matches the driver's mass [Fhm], ergo it now controls the response and decelerates at 1/f to maintain a flat response due to its mass is increasing relative to the sound power.
Below Fs then, acceleration must increase at 1/f, so at some point [Flm] it can no longer provide enough radiation impedance, ergo Fs is the mean of the Flm - Fhm bandwidth [BW].
Note that all basic T/S box alignments peters out at Fhm; IOW the box no longer has any loading control over the rear of the driver.
I think I remembered that right...........
GM
Hi Greg,
Hope all's as OK as possible at your end?
And me.I assumed about 2.5ohms - 4ohms as a ballpark figure that would cover a broad spectrum of SET amps, which is more or less what I know the designer of the previous E series units had in mind.
Greets!
Sounds like a plan as that's the range of just about all the old tube amps had that I either messed with or saw published specs of excluding the early matching impedance ones that required really powerful [low Qt.] motors.
I guess, seems like new 'stuff' happens on a near daily basis, so as a 105 yr old uncle warned me in my youth, 'growing old isn't for 'sissies'.
So, you all good now?
GM
Hello again Scott!
I wanted everyone here to know that after reading Dave of Planet 10's post where he stated Scott's Vulcan cabinet design was his all-out assault on developing a DBLH for Fostex FE206EN drivers. I decided I was not going to rebuild the Sachikos I sold. Nor will I be building the updated version of the Sachikos known as the Kirishima. Instead I decided to have someone local custom build a pair of Scott's Vulcan double-back-loaded horns for me! Before making my final decision I shared a couple of private emails with Scott, in which he answered all my questions in great detail and gave me the desire to build the Vulcan double-back-loaded horns. I'm so eager that I've already obtained my Vulcan plans from Woden Audio! My plan is to have the Vulcans completely finished in a very shiny black paint finish with the exception of having a beautiful wood veneer on the cabinet's two faces only! I believe that design will make for one gorgeous looking pair of speakers.
I hope this thread continues on as I'd love to read what you all have to say. I'll be sure to post some photos of the Vulcans when they're finished and set-up in my audio room. In the meantime a HUGE thanks to Scott and Dave. You two have become as good an audio friend as one can have from conversations on a website and via emails. Thanks to you both, but especially to you Scott for creating all these different plans for us out here in audio-land. You're a very magnanimous person either giving your designs away free via Frugal-horn or for an extremely reasonable charge via Woden Audio. I cannot thank you enough for all you've done for me over the years...
Thetubeguy1954 (Tom Scata)
Hello Dave!
As per your post I've just sent you an email via Planet 10. I hope that was the right way to go because I didn't know how else to contact you privately. I'll be looking forward to your reply. Thanks for helping me build and even better pair of speakers than the Sachikos I just sold.
Thetubeguy1954 (Tom Scata)
As per your post I've just sent you an email via Planet 10. I hope that was the right way to go because I didn't know how else to contact you privately. I'll be looking forward to your reply. Thanks for helping me build and even better pair of speakers than the Sachikos I just sold.
Thetubeguy1954 (Tom Scata)
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