Darth Modula MX Monitor

[Evil Twin]

A new project for a “MaXimum Modula system is underway- actually, it has been in a low key manner for some weeks...

All Modula’s are two way systems... this will be no different... except in the scope and the results.

New waveguides sourced from vendors on the Galactic rim have been obtained for evaluation... yes, it did require the use of “rebel” transportation services on the notorious “Kessel run”.




This is also a 1.4” throat waveguide device- the plan is to test with the B&C DE990TN, one of the most advanced titanium diaphragm compression drivers on the market. This should be accomplished soon.

There is the clear possibility of a cabinet design using a modified “off the shelf” subwoofer cabinet, for those who’s woodworking skills may be out of practice. This has been sourced and is in the process of assembly.

Waveguide tests will occur much sooner, though...

There is another complimentary project which admittedly is competing for time and resources- for now this project is code named “Death Star” and the reason for this name may become apparent when I post a picture of a driver...

[Evil Twin]

DeathStar

For those who may be lacking in imagination for the nature of the other project underway, I submit these two images...

[ergo]

That waveguide borders the horn territory already (wondering where the line goes actually or if there is a consensus about it even). Looking for both the results and the Modula on steroids with great interest.

**

Such Death Star look alike subwoofer would probably sell very well to all those Star Wars fans all over the world. That might me a very viable business idea on its own

[JonMarsh]

That waveguide borders the horn territory already (wondering where the line goes actually or if there is a consensus about it even). Looking for both the results and the Modula on steroids with great interest.

**

I was wondering about that too, looking at some of these parts, and also some of Gedlee's stuff. Seems like it's almost coming down to nomenclature... or do you draw a line based on how wide the dispersion is?

BTW, there's a new Klipsch speaker that is using a horn but filling in the corner creases to almost convert it to an elliptical waveguide... or elliptical horn.

Maybe if it's a rounded profile, round or elliptical, we call it a waveguide, and if it's got flat sides, we call it a horn? Except that classic Swiss and Bavarian "horns" and horns for music don't fit that... very rounded!

Whatever, just don't call me late for dinner...

[Juhazi]

https://www.parts-express.com/pedocs/specs/294-5990--bc-15SW115-4-spec-sheet.pdf

They call it subwoofer, but look at response... A doublet might give more freedom with eq

MX means motocross to me

[Evil Twin]

How one uses a tool is always the key...

Your point about the simple box mounted response is well known... and a very typical characteristic of professional drivers, due to their very high BL product and low Qts, which are intrinsic to the goal of high sensitivity in this class. But there are other "darker" methods less well known...






which can bend the driver's performance to one's goals...

[Evil Twin]

I was wondering about that too, looking at some of these parts, and also some of Gedlee's stuff. Seems like it's almost coming down to nomenclature... or do you draw a line based on how wide the dispersion is?

BTW, there's a new Klipsch speaker that is using a horn but filling in the corner creases to almost convert it to an elliptical waveguide... or elliptical horn.

Maybe if it's a rounded profile, round or elliptical, we call it a waveguide, and if it's got flat sides, we call it a horn? Except that classic Swiss and Bavarian "horns" and horns for music don't fit that... very rounded!

Whatever, just don't call me late for dinner...

One might learn by further study of authoritative source material- chapter six of Gedlee's book is a relatively accessible treatment including the contrast between the goals of horns and waveguides, and at it's conclusion postulates an (achievable) target condition for the relatively ideal condition of a polar pattern with smooth and consistent angular variation...






How close to some devices achieve this characteristic?


ME90 from B&C




LTH142 from Faital




Of course, in the Force we trust- everything else must be measured and verified....

[Scottg]

It's ironic given that Earl never achieved constant directivity.. Because he uses a circular/"concentric" expansion you've always got that "hole" on and slightly off-axis near the height-queue region (typically around 7 kHz for most people).

Even then, constant directivity was only so "constant" down to the upper range for the woofer: which seemed at best to be about as low as 900 Hz.


Though Earl preferred a more definite definition for a waveguide, the conjunction already has meaning: placing the emphasis for the design on controlling directivity and NOT on spl-gain. In contrast, a "horn" is all about gain and only regards directivity as a means for gain. ex. you don't cup your hands together near your mouth to get a specific directivity when you shout, rather you do it to increase loudness.

A horn is necessarily a subset of a waveguide. The opposite is not true: you can achieve a particular directivity pattern with a waveguide that "guides" the wave through absorption.

[Scottg]

This is one of the better waveguide/driver combo's for a more constant result (..even if the driver itself was a bit "wobbly" on the low-end), from Brandon/Augerpro:

https://sites.google.com/site/drivervault/driver-measurements/horns-and-waveguides/qsc-pl-000446-gp

..value-wise this combo is hard to beat for several reasons:

https://www.audioxpress.com/article/peerless-by-tymphany-dfm-2535r00-08-compression-driver

-I *think* the non-uniform "dip" off-axis between about 1.4 and 2.7 kHz is the result of the measurement condition of not being on a baffle for this waveguide.

[Evil Twin]

It's ironic given that Earl never achieved constant directivity.. Because he uses a circular/"concentric" expansion you've always got that "hole" on and slightly off-axis near the height-queue region (typically around 7 kHz for most people).

Even then, constant directivity was only so "constant" down to the upper range for the woofer: which seemed at best to be about as low as 900 Hz.


Though Earl preferred a more definite definition for a waveguide, the conjunction already has meaning: placing the emphasis for the design on controlling directivity and NOT on spl-gain. In contrast, a "horn" is all about gain and only regards directivity as a means for gain. ex. you don't cup your hands together near your mouth to get a specific directivity when you shout, rather you do it to increase loudness.

A horn is necessarily a subset of a waveguide. The opposite is not true: you can achieve a particular directivity pattern with a waveguide that "guides" the wave through absorption.

This update is much closer to the complex reality than the earlier version of your post, in my own relatively unknowledgeable opinion. In fact, one can guide a directivity pattern not just by absorption but also delay, as was the principle behind the JBL slant plate acoustic lens - an item I once employed in a sound reinforcement system.

But I still find this definition somewhat facile as regards both the motivation and execution for the use of "waveguides" in home DIY speakers... the situation is not bipolar, but more like that of a complex Venn diagram.

Of course, I cannot make a statement like that without giving some justification.

My observation is that a good waveguide is intended to improve the consistency of directivity with regards to a wider frequency range-

But also a key benefit in most implementations is seeking to develop some "horn gain" in order to extend the low frequency capabilities of the driver element, and to reduce distortion by lowering the required diaphragm motion.

And interestingly, there is much variation in how well these are achieved, and some attempted solutions from commercial providers fail rather miserably at both...

[Evil Twin]

..value-wise this combo is hard to beat for several reasons:

https://www.audioxpress.com/article/peerless-by-tymphany-dfm-2535r00-08-compression-driver

-I *think* the non-uniform "dip" off-axis between about 1.4 and 2.7 kHz is the result of the measurement condition of not being on a baffle for this waveguide.

I saw this combination shortly after the review was published also, and if 1500 Hz extension at the low end had been sufficient for the design I wanted to investigate at the time, this would have received immediate attention. There are a number of horn/waveguides that this new relatively inexpensive compression driver could be paired with. A common point though, for most of these 1" class drivers, is the limited low end extension. A common point for the larger drivers is the limited "horn/waveguide" options and poor upper end extension in most cases. At a combined price for the Eminence + Peerless driver of $50, it becomes an interesting point for systems using LF drivers with a more extended top end- this pricing compares well with conventional tweeters. One also speculates that doing a custom waveguide for this driver might be a worthwhile endeavor.

[Evil Twin]

Reaching into the past for simple examples...

Even the very shallow waveguide approaches used with conventional tweeters have at the heart of the effort a dual motivation- besides directivity control, distortion reduction in the lower range of the tweeter. So, yes, the horn gain is useful and desired.

I will use an example from the 2010 Module MT MkII design for which I was able to obtain more detailed information from the original designer, Jonmarsh. This design used a modified off the shelf MCM waveguide similar in profile to many others developed in this time frame, such as the Jantzen waveguide co-developed by Troels Gravesen.

This is a comparison of the D2608 tweeter mounted on a baffle versus with the waveguide.





The gain is not "large" but it is significant...


The directivity enhancement is clear...





The distortion profile is not that dissimilar compared with constant drive for direct radiation...




Until one examines the results with the crossover filter compensation in place, reducing the tweeter drive level...





For a large number of listeners, this effect may be as important or more important than the directivity improvement.

[Evil Twin]

When an interesting solution goes obsolete...

One of the more challenging aspects for building waveguides for conventional tweeters is the sensitivity to the immediate throat shape and the tweeters own issues with performance...

One particular example that was very promising initially was a waveguide developed for the original Dayton RS28a, which has a variety of characteristics lending itself well to that role, particularly when extended LF performance is sought...






Naturally, when one is a Dark side practitioner, there are inevitable side effects- a higher preponderance of Murphy's law events probably being one...

So, shortly after developing this waveguide, the discontinuation of the RS28a was announced, resulting in a year+ wait for a replacement from Dayton Audio.

This replacement, as others have found, is in many ways quite unsatisfactory... and that was also the case for this application.






The RST28F was no more suitable, with it's own pronounced aberrations above 10kHz.

[Evil Twin]

This is one of the better waveguide/driver combo's for a more constant result (..even if the driver itself was a bit "wobbly" on the low-end), from Brandon/Augerpro:

https://sites.google.com/site/drivervault/driver-measurements/horns-and-waveguides/qsc-pl-000446-gp

..value-wise this combo is hard to beat for several reasons:

https://www.audioxpress.com/article/peerless-by-tymphany-dfm-2535r00-08-compression-driver

-I *think* the non-uniform "dip" off-axis between about 1.4 and 2.7 kHz is the result of the measurement condition of not being on a baffle for this waveguide.

Just incidentally, that is not an Eminence APT150S which the driver is mounted on, per the claim of the reviewer.

It is an Eminence SST1 constant directivity horn.

https://www.parts-express.com/eminence-sst1-1-constant-directivity-horn-90x40-2-bolt--290-556

[Scottg]

-good catch! NOT a screw-on waveguide. The commercial waveguide I'd normally recommend on a budget here is the RCF H100, but I'm not sure it's actually better in this instance (and it's still almost double the cost).


The B&C is doing quite well with an integrated (surround) metal diaphragm, both with regard to break-up (top octave) and non-linear distortion on the low-end. It looks like all of their computer modeling is paying-off. 8)

[Evil Twin]

Yes, it seems clear the performance of their engineering team is well above “average”...

And it seems clear evaluating the Peerless compression driver as well as the DE500 on both the SST1 and the ME20 might be interesting... most interesting.

[augerpro]

If I ever did a big 2-way with 1.4" CD it would be with the 18 Sound ND3ST: https://www.audioxpress.com/article/...ression-driver

[Jonasz]

If I ever did a big 2-way with 1.4" CD it would be with the 18 Sound ND3ST: https://www.audioxpress.com/article/...ression-driver

What about Celestion 3040: https://celestion.com/product/202/CDX14_3040/

And Faital HF1440: https://faitalpro.com/en/products/HF...p?id=502020185

[Scottg]

If I ever did a big 2-way with 1.4" CD it would be with the 18 Sound ND3ST: https://www.audioxpress.com/article/...ression-driver

-pretty much reference-level above 1 kHz.. but unlike their poly-surround drivers, it has higher distortion on the low-end. (..of course after eq. it might be moot.)

I almost always prefer an aluminum (alloy) diaphragm myself with a poly-surround. Subjectively you tend to trade a smidge of detail for a more "3D" result. The 1460A and the 1480A preferably. Objectivly you gain better distortion lower in the pass-band and linear "hash" is often lower until break-up.

Paul's Raptors as an example (note the smoothing condition):

http://www.htguide.com/forum/showthread.php?35812-The-Raptor-a-10-quot-MTM

[augerpro]

What about Celestion 3040: https://celestion.com/product/202/CDX14_3040/

And Faital HF1440: https://faitalpro.com/en/products/HF...p?id=502020185

Dunno. I just know when I looked at all the tests at VC the ND3ST stood out with very good frequency response and polars, but absolutely incredible harmonic distortion compared to any competitors.

-pretty much reference-level above 1 kHz.. but unlike their poly-surround drivers, it has higher distortion on the low-end. (..of course after eq. it might be moot.)

I almost always prefer an aluminum (alloy) diaphragm myself with a poly-surround. Subjectively you tend to trade a smidge of detail for a more "3D" result. The 1460A and the 1480A preferably. Objectivly you gain better distortion lower in the pass-band and linear "hash" is often lower until break-up.

Paul's Raptors as an example (note the smoothing condition):

http://www.htguide.com/forum/showthr...-a-10-quot-MTM

VC says "proprietary surround" but the pic looks like plastic of some sort. I know PaulW also preferred a soft surround in CD's.

[Evil Twin]

Another 1.4" alternative from 18 Sound

The ND3T and NDS3T are both quite interesting looking drivers, but so is the NSD1480N, with the nitride diaphragm coating for increased stiffness (raising the cut off frequency by about 25%).

They are not easy to locate for retail sales, and not inexpensive, unless one is comparing to the likes of a ScanSpeak 7140 or similar premium tweeter.











If the distortion performance is remotely similar to Kimmo's results for their premium 1" driver, the NSD1095, then this part should be interesting... very interesting!

[Evil Twin]

If I ever did a big 2-way with 1.4" CD it would be with the 18 Sound ND3ST: https://www.audioxpress.com/article/...ression-driver

I agree this is a very interesting part- though after a full review of their offerings, I believe the NSD1480 would offer even further benefits in performance, though at a 25% higher price, and with fewer distributors carrying it.

Kimmo has tested the smaller 1095 driver with excellent performance results, for those applications only needing a 1" driver. There is one experiment I have in mind for that configuration now... to test an unusual crossover configuration with low phase distortion and low group delay.

[Scottg]

The ND3ST is the newer driver vs. the NSD1480, with some technical improvements. I believe that the 1480 also has an integrated (metal) surround, so both have rapidly rising non-linear distortion nearing resonance. (..unlike the DE990TN that seems to have been "engineered" around that issue.) Gauss for those 18 Sounds is pushing the limit, and the B&C isn't far behind.

In contrast the smaller nitride-coated 18 Sound has a poly surround.

At one time 18 Sound said they would nitride coat a driver on request (..though after the purchase by B&C I doubt that's the case). My guess is that at some point B&C will dump the 18 Sound brand and just plow the talent and distribution-channel into B&C.

[JonMarsh]

Yeah, I’ve kind of wondered myself how long they would keep operations separate since the purchase in 2017. But then, I can’t really say I have any insight into the business reasons for it... market share? But 18 Sound does have some interesting stuff, but it could all be rebranded pretty easily- such as their horns like the XT1086 or the XT1464.

Thanks for sharing the info about the surround design.

[Evil Twin]

Testing continues

While the performance of the DE990TN so far seems fairly satisfactory, especially in regards to distortion....





However, though the Faital LTH142 horn may be similar in appearance to the 18 Sound XT1464, the measured results do not meet expectations...






Whereas the ME90 performed as expected...




Now a pair of the XT1464 are on the way for evaluation.

Clearly Paul W.'s Raptor project is a design direction I overlooked until it was brought to my attention- the similarity in possible configurations I have considered is very strong- though the MTM concept was considered initially more for future development, I am now most interested in pursuing that possibility, though at this time the Satori W024P-8 is the target woofer under consideration.

A preliminary target design shows potential, but several possible passive crossover arrangements will be considered before finalization, including one asymmetric configuration that is near transient perfect with low phase and group delay. There may also be some further driver evaluations...

[Dave Bullet]

Dark Lord, you're going to need a new dreadnought to carry the extra stock you are acquiring and do not immediately need. I also recommend A Sith Infiltrator for component deliveries, with an upgraded hyperdrive (using neodymium magnets). This will ensure you are not wasting your precious time waiting for test subjects. Using the force would be another option, but that is probably better utilized levitating your test cabinets for measuring.

What CTC spacing would you be targeting for a WO24P-8 MTM? Would they suit a MLTL or are you thinking of a more conventional cabinet approach?

[Scottg]

The Dark Lord might completely "turn to the dark side" :P and use an Azurahorn. It's not a *"constant" angle waveguide, but in the right circumstance that can be an advantage. Plus it's vastly more efficient and extends lower in freq.. Additionally, that round-over results in a very non-obvious "horn" sound.

*(..the "advantage" with it's more directive nature is picking an OFF-axis to listen to on a "toe-OUT" basis (from an "aimed at listener" geometry) and then eq'ing relatively to a desired "flatness" for the listener's axis. It's a little "head-in-the-vice" result (unlike a "constant" design doing the same thing past 30 degrees), though not bad, BUT it provides a wider sound-stage by virtue of having greater pressure from left channel to left ear and right channel to right ear (relative to the opposing channel). For designs like this I start with on-axis and then start turning them outward a bit at a time until I get an idea of what I'm looking for then start the process over again with the filter - usually targeting the typical "sloped power response" on-axis at 2+ meters (which the "constant" version doesn't quite accomplish).

Again, from Brandon's excellent site:

https://sites.google.com/site/drivervault/driver-measurements/horns-and-waveguides/azura-425hz-horn

Note: the poorer freq. response is a result of the driver, not the Horn:

https://www.azurahorn.com/JA6681B%20on%20425%20Horn%20(2).pdf

[Evil Twin]

The Dark Lord might completely "turn to the dark side" :P and use an Azurahorn. It's not a *"constant" angle waveguide, but in the right circumstance that can be an advantage. Plus it's vastly more efficient and extends lower in freq.. Additionally, that round-over results in a very non-obvious "horn" sound.

*(..the "advantage" with it's more directive nature is picking an OFF-axis to listen to on a "toe-OUT" basis (from an "aimed at listener" geometry) and then eq'ing relatively to a desired "flatness" for the listener's axis. It's a little "head-in-the-vice" result (unlike a "constant" design doing the same thing past 30 degrees), though not bad, BUT it provides a wider sound-stage by virtue of having greater pressure from left channel to left ear and right channel to right ear (relative to the opposing channel). For designs like this I start with on-axis and then start turning them outward a bit at a time until I get an idea of what I'm looking for then start the process over again with the filter - usually targeting the typical "sloped power response" on-axis at 2+ meters (which the "constant" version doesn't quite accomplish).

Again, from Brandon's excellent site:

https://sites.google.com/site/drivervault/driver-measurements/horns-and-waveguides/azura-425hz-horn

Note: the poorer freq. response is a result of the driver, not the Horn:

https://www.azurahorn.com/JA6681B%20...Horn%20(2).pdf

These are interesting references you bring to my attention - as well as your suggestion for choosing a voicing axis.

The Azurahorn immediately brings to mind images and reviews of Avant Garde speakers; I conducted a brief review of his web site (Australia!- but the smaller ones are feasible for international post according to him) and I must acknowledge that just knowing and understanding this possibility in detail is a compelling proposition, regardless of the difficulties in making time available... Further investigation of the development of this horn profile will be required.

My ultimate target for this application would tolerate "head in a vice" better than some, as obviously directivity control is important. But likely not to the degree you imply... this will be for a music rehearsal and recording area, and while an initial build will use conventional sealed woofers, the ultimate implementation is planned to incorporate a cardiode midoowfer/midrange with the larger bandpass woofer handling the upper bass and lower ranges- hence the B&C 15SW115.

Note: the poorer freq. response is a result of the driver, not the Horn:

This is the primary problem with evaluating any solution- the interaction of the two is just as critical as the primary design characteristics.


Note these measurements, all done by a 3rd party on the XT1464 for three drivers which individually are often considered to be fairly high performance....

[Evil Twin]

Dark Lord, you're going to need a new dreadnought to carry the extra stock you are acquiring and do not immediately need. I also recommend A Sith Infiltrator for component deliveries, with an upgraded hyperdrive (using neodymium magnets). This will ensure you are not wasting your precious time waiting for test subjects. Using the force would be another option, but that is probably better utilized levitating your test cabinets for measuring.

What CTC spacing would you be targeting for a WO24P-8 MTM? Would they suit a MLTL or are you thinking of a more conventional cabinet approach?

This is expected to be a development process, with learning steps along the way... and while a sealed MTM is initially contemplated, it is expected that the WO24P will operate in a cardiod cabinet in the final development, with the bandpass woofer concept described above implementing the bass frequencies below some yet to be determined cut off point.

Think in terms of a more massive implementation of the Dutch & Dutch 8C.

https://youtu.be/fygm3iV_odA

This so called "stand mount" speaker incorporates two 8" rear firing "subwoofers" in addition to the front firing primary woofer.


The first test case build with sealed woofers will utilize 55L volume cabinets approximately 16" wide for the woofers, with the woofers offset towards one end. These will be stacked with the WG/Horn test cabinets (I expect testing with several cabinets, retaining the ability to control driver relative acoustic origins physically).

Several crossover approaches are being considered; the primary approach which will be investigated is a quasi-transient perfect alignment using 4th order BW on the low end and 2nd order Bessel on the top end, with 1/2 wavelength at the crossover Fc rearward offset of the HF range driver. This configuration is capable of very low phase and group delay distortion, in addition to relatively optimum transient behavior (reproduction of pulses).

At this stage of things this is more a technology exploration project than a speaker development one, though there are some very specific goals and potential tools being considered to reach these goals. There is also a secondary project to take these concepts to a smaller, more living room friendly form factor. In the present form, it is more of a rehearsal/recording studio monitor target. So, in many ways, this is like the early stages of the Evil Three Way Design study, being as much a technology investigation process as an end product development- how the latter will proceed is open to changes in direction and devices as the first stage evolves.



You are quite right about the cargo problems I am in the process of generating, so making regular weekend cargo runs in a modified YT-1300 cruiser to the outer rim is part of my regular weekend agenda this Autumn.... every Friday off in September and October.

[Evil Twin]

Testing in progress for a smaller project...

Drivers and horns are slowly arriving at the evaluation lab...


One thing becoming clear is that the only test which is valid is the exact combination one is considering- evaluating a compression driver by itself is not possible.

Some interesting trends are emerging with well known brands... as well as some new comers.


Eminence SST1 with Peerless DFM2535 driver...




18 Sound XT1086 with Peerless DFM2535 driver




SDX10 woofer, XBL2 technology (higher sensitivity with long throw)





Interesting is to compare impedance curves of the same driver type on different design horns... the SST1 is something of a constant directivity diffraction horn...




While the XT1086 is a controlled directivity ellipsoid waveguide horn, quite popular with many builders, and for good reason...



Jonmarsh is too busy for this testing, but he had some interesting ideas for what he called an "Arvo Pärt Pro"... undoubtedly they would benefit from some dark side influence, though.

[augerpro]

Awesome! Will we be seeing distortion comparisons too?

[Evil Twin]

Awesome! Will we be seeing distortion comparisons too?

Most definitely... for many experienced with this generation of technology, some things will be old hat. Also on order are 18 Sound NSD1095, which according to Kimmo and others set the benchmark for low 3rd harmonic distortion in high quality waveguides such as the XT1086.

It may be interesting to see if new low cost but reasonable technology competitors such as the DFM2535 or the SST1 can offer compelling value propositions at a significantly lower price point.

And this is part of a planned concept to explore that may be less room sensitive than many conventional solutions.

[Jonasz]

Don't think these are for sale yet but have you checked out SB Acoustics new pro drivers?

http://www.sbaudience.com/

[Evil Twin]

Don't think these are for sale yet but have you checked out SB Acoustics new pro drivers?

http://www.sbaudience.com/

I have followed some articles about their intentions and examined their current web site and offerings.

It is curiously puzzling.

There are many components being offered initially, which makes me ponder where the development expertise came from to produce a wide range of offerings. Or rather, "who" it came from.

However...

There are some very questionable choices in the initial data releases and product mix. they have a wide variety of compression drivers listed with different technological features, but they present data measured on on infinite baffle, no horn? Even the lowest Rebel audiophile would know better than that- and truly useful data is obtained ONLY when evaluating a specific combination, due to the interaction of driver characteristics and the horn/waveguide loading. If you do not have a reference grade 1.4" throat horn, it makes little sense to produce a driver with horrendous measurement results on an infinite baffle. And their horn offering does not seem quite primitive, it simply is quite primitive.

[Evil Twin]

More components arriving...

Since the last update, additional parts for testing in large and small system have arrived, including the 18 Sound XT1464 horns, and the 18 Sound NSD1095 1" throat compression drivers, which Kimmo has tested with such excellent results.




Note the key physical characteristics... they are shiny... and black.

[Scottg]

Note the key physical characteristics... they are shiny... and black.

-good god, let's hope they don't wheeze in operation! :W

(..wait, am I being lifted up in my chair! :cough: :COUGH: ..can't ..seem ..to ..breeeeeee..)

[augerpro]

Jon, I was going over the VC Test Bench again, and notice the Peerless 44mm voice coil driver looks a bit better than the 35mm. Maybe test that too? Also the Celestion CDX1 1742 also looks nice. It's real new though and I haven't yet seen it show up at suppliers.

[Jonasz]

Here's a test of the Celestion: https://www.audioxpress.com/article/...ression-driver

[SoundOfNothing]

Not sure why the CSS over Dayton RSS265HF-4, very similar specs with lower Le, albeit slightly less xmax, however it has excellent extension nearly to 1k. Distortion i'd guess to be excellent, plus it looks good

[Scottg]

..hmm 6+mm is somewhat more than "slightly less xmax" IMO.

I'm not sure it's for this project anyway (..unless he's trying for cardioid into the bass region, at which point I'd recommend Rythmiks because of what the sensing coil does for the design w/ their plate amps.)

[Evil Twin]

Jon, I was going over the VC Test Bench again, and notice the Peerless 44mm voice coil driver looks a bit better than the 35mm. Maybe test that too? Also the Celestion CDX1 1742 also looks nice. It's real new though and I haven't yet seen it show up at suppliers.

Recommendations from you are quite appreciated. I will investigate further as time allows... it is definitely a step by step process.

[Evil Twin]

Jon, I was going over the VC Test Bench again, and notice the Peerless 44mm voice coil driver looks a bit better than the 35mm. Maybe test that too? Also the Celestion CDX1 1742 also looks nice. It's real new though and I haven't yet seen it show up at suppliers.

The 2544 is interesting for a lower cost solution- will be ordered shortly. Like you, I do not see the 1742 yet at suppliers I work with... but published information looks promising. I see one vendor in France carrying it that I am familiar with...

[Evil Twin]

Not sure why the CSS over Dayton RSS265HF-4, very similar specs with lower Le, albeit slightly less xmax, however it has excellent extension nearly to 1k. Distortion i'd guess to be excellent, plus it looks good

Spec sheet bench racing may be quite entertaining, and one is always entitled to one's personal preference.

This project is focused on achieving a very high level of linearity up to moderately (some might say excessively) high output levels. The NSD1095 epitomizes the realization of that goal.

For woofers, motor design is a key factor and not to be taken for granted. Properly implemented, the XBL motor is capable of low distortion to levels which conventional overhung motors achieve only at the lowest output levels - by this, I mean comparing 10% of Xmax versus 60% of Xmax. Underhung motors can offer an excellent range of THD versus excursion also, but generally suffer from a reduction of BL product due to the long gap, and a reduction in power handling due to the necessity to keep the voice coil relatively short (straight trade off between VC length and available Xmax for a given gap length). For these reasons, underhung is widely used for tweeters, and rarely for low frequency drivers. (Aurasound NS512 being an example, as used in the Three Way Design Study). For woofers, underhung construction typically requires NEO magnet structures, or truly massive ferrite motors.

As is always the case, and as the British are fond of saying, the proof is in the pudding... not all implementations of sound principles are created equal.... (pun intended).

The SDX10s are planned for boundary mode bass applications, with clean response desired to as much as 250Hz in some cases.

I have held the RSS265HF-4 in my hands, and it fulfills the primary requirement... shiny and black. But I expect more... The RSS265HF-4 is a good value and looks impressive... until you see it next to an SDX10 and test them both.

[SoundOfNothing]

^ good points and thorough explanation. Thanks. I have a pair of woofers with an XBL motor but never got around to testing them (sitting in storage the last 8 years), they were all the rage a few years back.

[Scottg]

The SDX10s are planned for boundary mode bass applications, with clean response desired to as much as 250Hz in some cases.

Multiple listeners (..maybe HT)?