Kurosawa Koncept System

[JonMarsh]

Manly, Bob! A known design, or something you've cooked up?

I've got plans for what I believe I recall is a 5U version, the deep style, for a roughly 80W class A design... Sort of on the back burner, but I'm starting to acquire more parts- I should probably finish the simulations and design before ordering chassis, though!

[BobEllis]

I'm a copier - although I could probably come up with something that works, I'll follow others' designs for the good stuff. Preferably with a proven PCB. I've already completed a 5 output pair Leach amp and a DIY Audio "Honey Badger", in work a Pass Aleph-J (jfet inputs, 30W into 8R single ended) and a Pass F5Turbo - a push pull design that should hit 50W in class A. I've also got a pair of Pass/Thagard A75s that I run as heavily biased class AB - about 15W class A and 125W in AB. Idling at 225W per channel they are winter amps.

[JonMarsh]

Idling at 225W per channel they are winter amps.

I know what that is like- the Cambridge Audio 840D I have that sits at 200W idle, and my Aragon Palladiums mono blocks that pull 250w idle each. Definitely not for the summertime blues...

that's why I've got some of these Class D things these days, and has such a love affair with my friend's Benchmark AHB2's. They don't seem to have the real grunt on the bottom end, according to him, compared with his Halcro DM88's, but Geez, that's $40K versus $6K... maybe we should cut them some slack?

[Evil Twin]

The testing droids at Seinar Labs have been earning their keep for a change, today.

There is some interesting data to review, but not without undesirable complications due to a possibly flawed test setup.

The lesson learned? Never send a droid to do a Sith Lord's work.

The key question to address was the capabilities of the Transducer Lab N26 Beryllium tweeter. Unfortunately, the witless test droid took the first test baffle with the approximately correct dimensions and used it- the test baffle for the ScanSpeak 7140.



The clear problem is that while the 7140 has a front plate which is 6-7 mm thick, this is not the case for the N26 BRG. So, palliative measures were taken by applying blue tack to smooth the transition to the actual baffle, but the differences in on axis measurement achieved at Seinar labs versus out going quality control at Transducer Lab is quite clear. None the less, a complete polar set was taken as these issue tend to average out off axis, and measured behavior at 20-30 degrees and more off axis should still be informative.


This is the complete polar plot group at 10 degree increments from 0 degrees to 50 degrees...




The 20 degree plot shows a fairly high level of correlation with the supplied outgoing QC plot:




With these issues there may be some cause to question the distortion results, measured at 90dB, both in magnitude and percentage:







Do we come to the point of judgement now? Reviewing the polar behavior of the 7140 is necessary...





The Polar response for both is reasonable for a hard dome tweeter out to 30 degrees not using a waveguide. Measurements are still needed for the N26BRG without the diffraction setup issues.

The 7140 has somewhat lower HD3, the N26BRG has lower HD2, and is fairly close with HD3.

now, a key point- there is a 2:1 difference in cost. That difference will go much of the distance towards paying for a crossover with high end components for the tweeter. That is not a trivial matter- the Imperial treasury is not bottomless in these trying times.

At this point, it would not be unreasonable to develop crossovers for both, and evaluate a final choice at a later date.

Another factor might be system pricing and slightly down market models. While this three woofer with six passive radiator variant should have exceptional sensitivity and performance, and the name "Dai Katana" has been proposed for that variant, it may be wholly justifiable to develop and test a dual woofer with with four passive radiators- that system might be simply the "Katana" variant.

Naturally, this progression can be carried further, into a single 4 ohm woofer variant, and even a single 4 ohm woofer with a different midrange and crossover approach, possibly using the Dayton RS56 in a somewhat higher frequency range. Then, the question becomes the optimum choice of tweeter, as it would be preferred to keep HD3 in the -60dB range if possible, and with a slightly higher crossover point, their might well be other possibilities at yet lower cost, including Transducer Labs magnesium or ceramic models.


Our manufacturing technologies director and CAD system manager Stephen Manning has been highly motivated this week, and considering issues of manufacturability posed by some concepts using six PR's on the back of the enclosure, and the difficulty of avoiding column resonances if a shared woofer space is used, has come back with an intriguing if initially unassuming proposal for the cabinet configuration...

I have sensed a disturbance in the force, as his frustration with learning the newly mandated CAD tool system has caused anger and despair to swell in his heart, increasing his strength and presence in the dark side. This is clearly revealed in this render he prepared...




This is not an whimsical concept drawing, but rather an arbitrary and constrained proposed based on the actual Panzerholz materials under consideration for the inner and outer front panel and sides and top of the enclosure. It is possible to change the concept somewhat to a more heavily baffled version, if 11-1/2" LBL boards are selected for the front panel material- this is a starting point for development, not yet a final cabinet build plan.


One last investigation was completed- examining in more depth the curious response characteristic of the AS190 with regards to conventional baffle step characteristics. These measurements were made on the same test cabinet as previously, with a baffle only 10" in width. It was measured near field, at 1M, and at 2M. As we are more interested in the general trends between 200H and 1kHz, as shown in conventional baffle step behavior for an enclosure of these dimensions, additional smoothing was made in order to reject room reflections and modal issues. The graphing has been adjusted to overlay the curves.

I must say that I find the results most curious, but with interesting implications for the system design.

[TacoD]

As usual very elaborate project! I was just wondering is it possible to buy "Panzerholz" in the US, also isn't it even harder to machine than Bamboo?

[Steve Manning]

As usual very elaborate project! I was just wondering is it possible to buy "Panzerholz" in the US, also isn't it even harder to machine than Bamboo?

Found a place that has two varieties of it as a matter of fact.

[Evil Twin]

Indeed, it is feasible to procure either beech or maple ply Panzerholz in sizes feasible for the project at hand. The maple is less expensive, and uses a fewer number of plies. It may be quite adequate for the task at hand, though.

Unquestionably carbide tools in top flight condition will be required, with reasonable adjustments of feed rate expectations. Unquestionably, this will also be another learning experience, with hopefully not to many painful lessons to write off to experience.

[neuro]

I'll just leave this Super Star Destroyer here as possible inspiration for form.

[Evil Twin]

As usual very elaborate project! I was just wondering is it possible to buy "Panzerholz" in the US, also isn't it even harder to machine than Bamboo?

We shall soon have more detailed answers to these points, as a material order has been placed and stock is confirmed; shipping details should be confirmed within 24 hours.

Now it remains to properly motivate the "CAD monkeys" (I am told this is the correct local vernacular..) to complete the layout proposals and design verification, and narrow down some other material choices, as well as follow up on tooling issues.

There are several design concepts in development, and numerous issues to resolve before making the final decisions.

[Evil Twin]

I'll just leave this Super Star Destroyer here as possible inspiration for form.

[ATTACH=CONFIG]25955[/ATTACH]

Do you have any idea what the upkeep is on one of these? These days?

Completely impractical...

[TacoD]

We shall soon have more detailed answers to these points, as a material order has been placed and stock is confirmed; shipping details should be confirmed within 24 hours.

Now it remains to properly motivate the "CAD monkeys" (I am told this is the correct local vernacular..) to complete the layout proposals and design verification, and narrow down some other material choices, as well as follow up on tooling issues.

There are several design concepts in development, and numerous issues to resolve before making the final decisions.

What thickness are you considering? I don't have the skill/ tools to machine the material, very interested how things come together. Looks like both Kharma/ Kaiser Kawero prefer it over Alu now a days. If I am not mistaken Kharma used phenolic (paper based) material before in their exquisite range.

[Evil Twin]

Panzerholz in some forms is used for piano pin blocks, and in this form it comes in standard sizes for this application- 59" long; thicknesses of 1-1/4", 1-3/8", and 1-1/2", and widths of either 9-1/2" or 22". I ordered 5 pieces of 1-1/4" double wide 22" planks, and 4 of 1-1/2" 22" wide.

The helpful assistant named Kelly asked if I was planning to build a house with this... I assured her I would not do that without the necessary building permits.

The 1-1/4" will be used for side panels and top and bottom panels. The 1-1/2" thick pieces will be used for exterior front panel pieces, back panels, and interior front panel pieces.

Unless I change my mind or find that the plan is not without faults... of course, there is always that homily that no plan survives contact with the enemy... possibly that should be modified to say that no build plan survives unmodified after contact with the work bench...

[sdl2112]

Of which quadrant was this precious material found...

[Evil Twin]

The vendor is from the USA, Vanda King Piano Showcase, undoubtedly a well known supplier of construction materials to DIY speaker hobbyists...

http://www.vandaking.com/s-490-delignit-beech-pin-block.htmlhttp://www.vandaking.com/s-490-delignit-beech-pin-block.html

[flamethrower1]

I about fell over after seeing the price of the panzerholz.

[Face]

It's not terrible if you compare it to the price of a similarly sized piece of exotic wood.

[JonMarsh]

Quite true, quite true. Just try pricing out phenolic like they use in Wilson Audio speakers...

[Evil Twin]

Now, this matter of vendors and the preferred sourcing quadrants has become something of a vexing topic. Though I have located in what is claimed to be the most technologically advanced nation-state on this backwater planet, curiously I find that I am often having to select and work with vendors from that loose confederation of states known as the "European Union", a most unlikely oxymoron to describe a region of your planet most often fraught with internecine warfare...

In this case, it is again a sourcing issue based on availability and pricing- just today ordering more Accuton AS190-9-252 from a very professionally organized vendor, even though their business title suggests a playful laissez-faire approach to matters-

http://www.hobbyhifiladen.de

while "Hobby" implies a non work oriented effort or activity, their professionalism with regards to in stock status of advanced Accuton drivers, including the Cell AS190-9-252, and attractive pricing put them on a more professional footing than North American vendors for the same products.

We shall see if their follow through and delivery matches the promise of their web site... it would be most disappointing if that is not the case.

[TEK]

We shall soon have more detailed answers to these points, as a material order has been placed and stock is confirmed; shipping details should be confirmed within 24 hours.

Now it remains to properly motivate the "CAD monkeys" (I am told this is the correct local vernacular..) to complete the layout proposals and design verification, and narrow down some other material choices, as well as follow up on tooling issues.

There are several design concepts in development, and numerous issues to resolve before making the final decisions.

I got this spy photo of you and the Sith inspecting the build of the Death Star. I can only assume that the kind of material and construction to use was being debated here.



As your Death Star seems to most likely be built from Panzerholz, a hard material, I can only assume that the purpose of this is that it will ensure that the ships firing system will not impact the body of the ship - causing unwanted vibrations from the ship to be received by the enemies fine tuned listening systems.

Has the Empire evaluated other solutions to address the problem with hiding ship vibration from the enemies?
For example principals using double bodies with air or soft material between them, to let the inner layer absorbs the impact from the firing systems, while the hollow (or sand filled) area prevents the impact from being transferred to the outer body of the vessel, and thus also from causing vibrations that might be detected by the enemies fine tuned listening systems?

[Evil Twin]

I got this spy photo of you and the Sith inspecting the build of the Death Star. I can only assume that the kind of material and construction to use was being debated here.



As your Death Star seems to most likely be built from Panzerholz, a hard material, I can only assume that the purpose of this is that it will ensure that the ships firing system will not impact the body of the ship - causing unwanted vibrations from the ship to be received by the enemies fine tuned listening systems.

Has the Empire evaluated other solutions to address the problem with hiding ship vibration from the enemies?
For example principals using double bodies with air or soft material between them, to let the inner layer absorbs the impact from the firing systems, while the hollow (or sand filled) area prevents the impact from being transferred to the outer body of the vessel, and thus also from causing vibrations that might be detected by the enemies fine tuned listening systems?

These would seem to be reasonable lines of inquiry- in fact, were size and expense not a limitation, constructing an audio transducer in the manner of a double wall vacuum jar might be most effective.

in other cases, reading the history of your quadrant, and efforts such as sand filled enclosure walls between relatively weak structural members, I believe there is a phrase in the local vernacular (sometimes difficult to master in it's varied idiom) of "putting lipstick on a pig" which seems suitable.

In general, considering practical methods of construction, using the stiffest material available and driving the panel resonant frequency well above the pass band of frequencies for that driver and providing some additional damping to lower the Q of the panel resonance is relatively simple to implement and evaluate by direct measurement. And is less elaborate than many of these alternative proposals. But no less effective.

Beyond this, I would suggest reading this review... comparing panzerholz and aluminum.

https://www.lessloss.com/page.html?id=80

[Evil Twin]

More data for the CAD monkeys to digest...

Further component measurements have been completed, in this case for the C90-6-724, with the expected results.


Quasi Infinite Baffle



Distortion check



I force choked the first test assistant who brought me this result, for what I believed was sloppy work, as it seems highly implausible based on the performance characteristics of most audio transducers- Upon examining the results and repeating the measurements myself, I was forced to conclude that this C90-6-72 driver has most unusual characteristics... interesting... HD2 is actually substantially lower than HD3.


The polar response at distance is in the range of what is to be expected for a pistonic driver of that size...



Although the first breakup mode is at a commendably high frequency for a driver of this diameter, the off axis capability limits the upper crossover frequency selection to around 2500 Hz to 3000 Hz. As the 0 to 30 degree response is within a fairly reasonable window even at 5 kHz, there should be some flexibility for choosing crossover slopes and frequencies if one is only concerned about on axis or near axis SPL. However, keeping resonance amplification of distortion products at a low level would suggest a lower crossover point and a tweeter that is comfortable in that situation.

[Navy Guy]

Great looking performance. I've had a pair of the Transducer Labs aluminum oxide domes for over 2 years now waiting to be put into a project. I can't wait to finally get started. Mine are going to be paired with an Usher Audio 8945a as a mid and 8955a for the woofer.

[flamethrower1]

Just to throw this out to you guys, I found this while doing a search on piano pin blocks.
I am trying to source some of the "panzerholz" for some turntable plitnhs.
I spoke with Tim from Great Lakes Piano Supply and he said he has sheets of " Falconwood" that is made by the same German company that makes the "Delignit" but is actually denser.
He said he has 48x60 inch sheets in 25mm and another around 1 3/8", he will cut to what ever dimension you want.

http://www.greatlakespianocompany.com/services/

[Steve Manning]

Just to throw this out to you guys, I found this while doing a search on piano pin blocks.
I am trying to source some of the "panzerholz" for some turntable plitnhs.
I spoke with Tim from Great Lakes Piano Supply and he said he has sheets of " Falconwood" that is made by the same German company that makes the "Delignit" but is actually denser.
He said he has 48x60 inch sheets in 25mm and another around 1 3/8", he will cut to what ever dimension you want.

http://www.greatlakespianocompany.com/services/

Cool ..... thanks for the link, this stuff is hard to find.

[flamethrower1]

Here is another link to forum discussing some comparisons, FYI

http://www.pianoworld.com/forum/ubbthreads.php/topics/2275098/2.html

[JonMarsh]

Wow. Definitely some esoteric discussion there...

[flamethrower1]

Sorry Jon, while the topic was piano tuning/set up and not speakers, I thought it was at least a little informative.
Anyway, just trying to help.

[JonMarsh]

No apologies needed, it was interesting- especially as I am a keyboard player, including pianos, which I started on. But rebuilding one is not something I would likely tackle- it's interesting how much discussion or disagreement there is about what are the most important things about rebuilding a pin block, and which is the best material and techniques.

[Evil Twin]

With basic measurements completed for now, it is time to explore crossover options...

An initial pass using the Duelund concept seems very promising... though some shaping is needed with shunt networks to deal with driver issues, given the net sensitivity, we will save the cost of padding resistors on the midrange and tweeter.

[NyxOne]

Is the downward slope between 100hz and 1khz part of your target curve of just a measurement artifact ?

[Evil Twin]

It reflects a combination of target voicing curve and measurement artifact for the data used from the AS190-9-252. About 3 dB at 100Hz will go away due to the latter. Overall target is a 3-4 dB down tilt between 100Hz and 10khz far field.

Also, these were sealed box measurements without the passive radiators; a test cabinet for the proposed configuration with Wavecor PR223BD02 is nearly complete.

Some additional attenuation of high frequency woofer artifacts is also under consideration. The woofer network follows the required LF transfer function quite closely up to 2500Hz, with a notch trap on the first break up mode, but there are secondary breakup modes that may require attention. Also, the midrange driver is lacking 1-2dB of sensitivity to hit the target function in the 700-900 Hz area, and that is being filled in a bit by the woofers.
Also, to maintain transfer function control in the mid bass it is necessary to use a conjugate network with regards to the woofer impedance; this will need to be adjusted for the final LF configuration.

Everything considered, it does appear to be on track to reach a finished system sensitivity of about 90 dB/2.83VRMS, though that capability comes with a 3 ohm impedance curve in much of the bass and lower midrange. A robust AB or Class D amplifier will be required; many Class A designs may not maintain that mode of operation, and it will be a rare Tube amplifier or non-feedback design that will have the current capability and output impedance in the low frequency range.

[NyxOne]

It reflects a combination of target voicing curve and measurement artifact for the data used from the AS190-9-252. About 3 dB at 100Hz will go away due to the latter. Overall target is a 3-4 dB down tilt between 100Hz and 10khz far field.

So a bit of both then! That explains a few things.

I've been following Mission DIY for quite a long time even though I don't talk much and you guys seems to like this kind of downward curve. Jon's seems fond of it too if I'm not mistaken. I've not design anything in a long time but when I did I've always targeted for a flat FR which always felt too bright! I think I'm going to try this kind of target curve next time I work on a design.

Is this to follow a target DI/Power response like pictured in the "Minerva Monitor" thread or just a personal flavor ?

Thanks for the clarification!

Edit : Just let me know if I'm going to off topic for your taste!

[ergo]

Everything considered, it does appear to be on track to reach a finished system sensitivity of about 90 dB/2.83VRMS, though that capability comes with a 3 ohm impedance curve in much of the bass and lower midrange. A robust AB or Class D amplifier will be required; many Class A designs may not maintain that mode of operation, and it will be a rare Tube amplifier or non-feedback design that will have the current capability and output impedance in the low frequency range.

Seems AS190-9-252 is actually even a bit favorable in this regard as it has tiny bit more than 8ohm impedance. I've been pondering some ideas along the lines of using 3 woofer row for a speaker for family room, but checking around - most every woofer is at max 8ohm and will mean impedances even lower than 3ohm... which I'm not sure I want to do.

This project is getting more and more interesting, but the feeling about the share cost of all the part seems to move in wrong direction at equal speed.

[JonMarsh]

So a bit of both then! That explains a few things.

I've been following Mission DIY for quite a long time even though I don't talk much and you guys seems to like this kind of downward curve. Jon's seems fond of it too if I'm not mistaken. I've not design anything in a long time but when I did I've always targeted for a flat FR which always felt too bright! I think I'm going to try this kind of target curve next time I work on a design.

Is this to follow a target DI/Power response like pictured in the "Minerva Monitor" thread or just a personal flavor ?

Thanks for the clarification!

Edit : Just let me know if I'm going to off topic for your taste!

Your experience is not at all uncommon, including with some pretty experienced people in the speaker design area, such as Sigfried Linkwitz, the developer of the Orion dipole speaker and it's successor. You might be interested in a PDF I put together on this topic as well as a concept for simple passive piece of line level hardware to address this. If so, PM me with an email address I can send this to.

[NyxOne]

Your experience is not at all uncommon, including with some pretty experienced people in the speaker design area, such as Sigfried Linkwitz, the developer of the Orion dipole speaker and it's successor. You might be interested in a PDF I put together on this topic as well as a concept for simple passive piece of line level hardware to address this. If so, PM me with an email address I can send this to.

PM sent!

Thanks Jon.

[JonMarsh]

Seems AS190-9-252 is actually even a bit favorable in this regard as it has tiny bit more than 8ohm impedance. I've been pondering some ideas along the lines of using 3 woofer row for a speaker for family room, but checking around - most every woofer is at max 8ohm and will mean impedances even lower than 3ohm... which I'm not sure I want to do.

This project is getting more and more interesting, but the feeling about the share cost of all the part seems to move in wrong direction at equal speed.

Yeah, I get where you're coming from. If I total up the component costs for what this must be running, it's something pretty similar to the Isiris with it's diamond tweeters, but looks like this will "just" be using Be.

you know, there's probably no reason this couldn't be done with just two woofers and matching sets of PR's per side. It would drop the sensitivity about 3 dB, but that still isn't chump change.

I suppose what should be remembered is that this is targeting a similar concept to the Mingus Quartet or Tidal Akira, with some compromises, and those are just insanely expensive speakers... €160,000 for the Akira! Of course, no diamond tweeters or midrange here...

[TEK]

It reflects a combination of target voicing curve and measurement artifact for the data used from the AS190-9-252. About 3 dB at 100Hz will go away due to the latter. Overall target is a 3-4 dB down tilt between 100Hz and 10khz far field.

Also, these were sealed box measurements without the passive radiators; a test cabinet for the proposed configuration with Wavecor PR223BD02 is nearly complete.

Some additional attenuation of high frequency woofer artifacts is also under consideration. The woofer network follows the required LF transfer function quite closely up to 2500Hz, with a notch trap on the first break up mode, but there are secondary breakup modes that may require attention. Also, the midrange driver is lacking 1-2dB of sensitivity to hit the target function in the 700-900 Hz area, and that is being filled in a bit by the woofers.
Also, to maintain transfer function control in the mid bass it is necessary to use a conjugate network with regards to the woofer impedance; this will need to be adjusted for the final LF configuration.

Everything considered, it does appear to be on track to reach a finished system sensitivity of about 90 dB/2.83VRMS, though that capability comes with a 3 ohm impedance curve in much of the bass and lower midrange. A robust AB or Class D amplifier will be required; many Class A designs may not maintain that mode of operation, and it will be a rare Tube amplifier or non-feedback design that will have the current capability and output impedance in the low frequency range.

The impedance curve on this seems to limit the number of amps that will be usable quiten a bit, and give the ones that does manage to drive this quite a challange.
High sensitivity is of course a plus if you need to play very load - but is there any other advantages with this crossover/driver selection that justifies the limitations forced upon amplifier selection?

[JonMarsh]

you would be surprised how many speakers have this kind of "issue"- look at the Stereophile review of the Avalon Indra, using only two woofers in parallel, a very common approach. Note, most so called 8 ohm drivers are 6 ohms RDC, and in the region between 80Hz and 300-400 Hz, so you'll find this problem a lot more often than you might realize. Even the NatalieP's are 3 ohms in a significant part of the mid bass and low midrange.

At least the AS190 drivers are rated 9 ohms by Accuton, and that's their RDC, not their averaged AC impedance, which is higher.





With the Ardent and Isiris I took specific steps to avoid this, by using 4 ohm drivers in series- which often gives more favorable T/S parameters for the LF system, too.

[Evil Twin]

With some additional review in another tool, there are some small but useful updates- taking things to the point where further refinement will require measurements in the target cabinets and driver mounting.

Though the mentioned adjustments to the woofer for level compensation for the midrange impair the phase tracking slightly, one can clearly see how in general the drivers all track in the same phase, and only one phase rotation is present from bottom to top.


Schematic and SPL




The crossover network is slightly updated from the previous LspCAD files, and uses standard E24 component values in most locations.


Directivity and polar response to 50 degrees



Phase response



It can be seen that the phase response of all drivers track each other fairly closely through out the frequency range.


It is a working theory that the bump in the response of the C90-6-724 in the 1200-1500Hz area may be due to the outer ring motor structure, which leaves a cylinder behind the radiating dome. Additional damping material in this area may reduce it. Furthermore, while the test cabinet was loosely stuffed with fiber glass, it was not treated in the manner normally used for a high performance midrange enclosure. This will need attention in the final design.





The next step must be to complete the 3D cabinet model and piece part documentation, then commence construction of this technological terror once all materials are on hand- that is scheduled to happen this week, but we do not anticipate construction starting before July 1. We have some captive labor from the Tantoonie slave market which is expected to arrive then via a known smuggler, and this may prove helpful to the cause.

Design data must be taken one more time in the actual cabinets and checked against the results to date- then a crossover component order may be placed.

[Matt M]

It is a working theory that the bump in the response of the C90-6-724 in the 1200-1500Hz area may be due to the outer ring motor structure, which leaves a cylinder behind the radiating dome. Additional damping material in this area may reduce it. Furthermore, while the test cabinet was loosely stuffed with fiber glass, it was not treated in the manner normally used for a high performance midrange enclosure. This will need attention in the final design.

The people behind the german DIY-club Hifi-selbstbau.de investigated the c90-6-724 and theorized that the rear tube behaves like a very short transmissionline, thus showing severe resonances at higher frequencies. This could clearly be shown in an acoustic measurement from the rear. Overlaying rear-response and front-response gave an idea of the effect. After testing several approaches, they recommended a foam cylinder (4" length, ~3" diameter), shoved 40mm into the motor. In general, reducing the discontinuity of impedance was considered beneficial.

The public part of the article can be found here (google translate version).

The other part of the article is "members only", but the foam-plug is the essential take-away. One has to wonder, why accuton isn't giving any advice on the issue.

Another interesting article addressing the issue can be found here (xen/Avalon clone, pdf file).

-Matt

[Evil Twin]

I came across both of these articles in doing research, but thank you for the forum for linking to them- in the case of the first, I muddled through with my limited command of Deutsche.

Clearly the damping employed in the rear of the driver will be fairly critical to obtaining the best response; perhaps fortunately more recently shipped drivers have an additional mesh installed which would likely prevent unintentionally damaging the ceramic cone with damping materials pushed too far forward.

Curiously, the Xen article showed a rather different set of issues with the midrange frequency response, but it seems apparent that a large factor was the design of the mid-range enclosure in that case - and their use of shunt RLC networks is noted.



Picking the optimum acoustic foam or damping material may still be a matter of some experimentation before finalizing the midrange enclosure and damping. Currently some schedule 80 PFC tube is on hand which is planned for use for the actual enclosures; eBay most certainly has it's uses. An additional baffle and enclosure test fixture is already planned, to mimic the final enclosure configuration.

[Face]

Picking the optimum acoustic foam or damping material may still be a matter of some experimentation before finalizing the midrange enclosure and damping. Currently some schedule 80 PFC tube is on hand which is planned for use for the actual enclosures; eBay most certainly has it's uses. An additional baffle and enclosure test fixture is already planned.

http://www.homedepot.com/p/UltraTouch-16-in-x-48-in-Denim-Insulation-Multi-Purpose-Roll-6-Pack-60306-16482/202710055

[Matt M]

The addition of those rear meshes makes a lot of sense. At the very least providing some peace of mind. Anyway, a most fascinating project - looking forward to where this is going!

[Evil Twin]

http://www.homedepot.com/p/UltraTouc...6482/202710055

This looks like it might have properties similar to ATS Acoustics Applegate Acoustical Cotton Batts, which have been procured for enclosure lining. The value proposition of the HomeDepot version may be quite high, given the pricing- curious that it is only sold online. One package has been ordered for evaluation. You are to be commended for sharing this information...

[Evil Twin]

The addition of those rear meshes makes a lot of sense. At the very least providing some peace of mind. Anyway, a most fascinating project - looking forward to where this is going!

That, indeed, is a good question- one certainly hopes to avoid the fate of other massive construction projects for which I have had to provide motivation...

more status updates later today, regarding activities in progress this week.