PE Dayton Reference Series

[Hank]

Yes, the mode is disappointing. I gues we were hoping for a perfect 8". The PE .pdf impedance plot is smooth for the RS180S, so I "hope" it will hold true in production units.

BTW, what's the price delta between the Hales Transcendence and Excel Millineum tweets?

[JonMarsh]

Yes, the mode is disappointing. I gues we were hoping for a perfect 8". The PE .pdf impedance plot is smooth for the RS180S, so I "hope" it will hold true in production units.

BTW, what's the price delta between the Hales Transcendence and Excel Millineum tweets?

Steve,
Yeah, if I didn't have a lot of travel coming up, I'd probably pop the RS170's into my X1 cabinets and see how they look. I'm hoping for better behavior with the smaller cone. It looks clean on paper to at least 2 kHz, maybe a dip at 3.5 (reading between the lines). If that's the case, it would work out fine with what I want to do with it.

I think the crossover for the RS225 may still be doable at 1 kHz with good results- but a very narrow range of tweeter choices.


The Hales is not an item that you can buy- I bought several pairs last year, from someone who was closing out their stock when they went bankrupt, and the assets were acquired by QSC- these actaully came through someone who's a designer at Aurasound, though. I paid around $140 a pair, a reasonable price for a driver close in performance to an SS98000. I do modify them a little, though, as shown in the M8ta thread.

The Seas Millenium Excels are ~ $300 a pair. Not inexpensive, but probably the finest soft dome tweeter in the world, partly in my opinion, because they maintain pistonic behavior to beyond 20 kHz due to dome shape and treatments. Also an excellent motor. Will they hold up with my Cauer elliptic to 1 kHz? I think so, given that with a conventional 4 order L-R Linkwitz gets good results to 1400 Hz crossover frequency.

What I think I can do is design a crossover for nominal 4 ohm, and use zobels and impedance termination networks that would make either of these tweeters look like a four ohm load to the network.

Something to do in my spare time on planes next week, since I've got all the CLIO data uploaded to the laptop.


~Jon

[Mark K]

Glad to know my measurements are independently confirmed.


I agree this driver probably would work best as two 8"'s in a three way, though, if you can get a 1k xover, well, that would work.

I have unposted 7" measurements comparing the RS180 to an SS8545 and PL18, though not as detailed as the others, that I'll try to post.

[JonMarsh]

I'd be very interested in seeing those, Mark, as it will be a couple of weeks or slightly more before I can look at the RS180's myself.

I also have a couple of pairs of the RS270's on the way, so I'm curious to see how those stack up- no two ways with them! (uh, well, unless you count a minimalist two way that might be possible paird with the RD50's. Wouldn't be full range on the bottom, but might be fairly respectable. But I'm not planning on stopping at two way- that will be a four way dipole system when it's done).


I think you may be correct about the "best" application for the RS225 - two on the bottom end, mated to the 7" or 6" around 200-250, then around 1500-2 kHz to a good tweeter could be a very nice moderate cost system to build. Sounds a lot like a Watt puppy Klone. I'm not sure I'd want to go with that shape head unit, though.

It will be interesting to see what the next six months or so turns up in projects with these drivers- I fully agree with you, they seem to be real bargains as regards the value proposition. Thomas thinks I'm a little crazy pairing up $75 to $140 tweeters with $30-40 midwoofers, but I think they justify it, especially as they reduce the "pain of ownership" for the complete system.

~Jon

[Mark K]

Hi Jon and anyone else. I updated my page with the SS8545/RS180/PL18 results.

http://206.13.113.199/ncdiyaudio/mark/index.htm

See the 7" woofers subheading on the testing page.

[Hank]

Mark, thank you for your work. Yes, the Dayton does hold its own agains the $$ SS competition, and I look forward to possible MTM applications, and of course, applicability in a line array :W

[JonMarsh]

Thanks for doing all these measurements, Mark, and sharing them with the "community". I still wouldn't use these above 1500 or so, but that's about what I was hoping for, anyway.

That 4:1 cost difference is something of marvel, especially considering the RS180 is shielded, a big deal for folks with direct or rear projection CRT.


Thanks again...

Regards,

Jon

[JonMarsh]

The RS270's are here, the RS270's are here!

They're pretty solid looking, cone seems pretty inert, good size magnet and sheilding. The interesting thing will be getting some curves on these when I'm back from Denver.


Film at 11.

[Brian Bunge]

Jon,

I was wondering what you thought of the aluminum dome tweeter from Vifa. IIRC, it's the D25-35 or something like that. The one with the rear chamber. I know it's only a $30 tweeter, but I've heard good things about it before. And, from what I remember, the Fs is around 850Hz. Could it work as a low cost alternative until I'm "in the money"? Or would you suggest that LPG or the Vifa ring dome as the best bang for the buck?

[JonMarsh]

I think you're thinking aobut hte D25AG series, probably the D25AG-35-06, the chambered version. I remember looking at it; it looks close, but have some roll off starting about 1.5 kHz. It isn't nearly as flat and extended as the Vifa XT25, which is why I ended up with it for the "value" designs. It might be workable, or even the D27TG-05-06. This is going by published curve, mind you; never having tried out the other Vifas.

If you check out the LPG26T curve, it's pretty promising; I'm going to get a pair to evaluate with my next order to Madisound this month. Some folks they aren't impressed with the build quality of the 26T, but I have to think that any tweeter that's this smooth, with a titanium dome, double magnet, AND an aluminum, not plastic, front panel, may have something going for it. I believe this tweeter is used by Totem and Aerial.


~Jon

[Hank]

aobut hte

After-effects of a tequila newbie having too many shots on vacation :boozer:

Welcome back to reality, Jon.

[Brian Bunge]

Jon,

Yes, that's the tweeter I was referring to. Aluminum dome with rear chamber. I've been interested in the LPG units as well. I actually listened to the Totems that use this tweeter and the HiVi woofer you used in your daughter's speakers. I thought they sounded pretty good, but not worth $3K. I'm sure if you used it with the Dayton's it'd smoke the Totems!

[JonMarsh]

Possibly....

The crossover is the real "secret sauce" for making a lot of these drivers play well together, except that, it's not secret! Well, not to anyone that asks, anyway!

I built the speakers for my daughters with the D6.8 and the Vifa tweeter and used a more conventional crossover; I wouldn't do that again, it just didn't work as well as my Cauer-elliptical for managing the transistion and keeping the tweeter happy, and any nasties from the midwoofer out of the picture.

It had pretty remarkable deep bass, as that driver does have some Xmax, but the Dayton's should do very well, and cost much less. Leaves more money for the tweeter and crossover, right?

I'm also planning on ordering some of the 6" Dayton's in just to check, though my feeling right now is that they're a bit masked from the rear by the magnet assembly, which could make for problems with conventional front panels.

Had some Seas 5" drivers like that, and it took making an aluminum front plate for mounting the drivers on to get extra rear clearance. Worked well, but was expensive....

~Jon

[Brian Bunge]

Jon,

How do you model the Cauer-elliptical XO in LspCAD? Do you just start with a 4th-order LR electrical and then add in more components to make the slope steeper? I've just now started playing with LspCAD's filter modeling capabilities but do not have a decent measurement setup yet. So I've been just using the measurements that PE has for a lot of their drivers to get something to play with.

Is it possible for you to send me the SPL and impedance files for the Dayton 7's as well as maybe the Vifa XT25 so I have some real measurements to load into the program? I assume I'd need to know what the measurement axis was and that kind of stuff. I know nothing I come up with will be as sophisticated as what you use but maybe it could get me on my way to working with LspCAD and actually knowing what I'm doing.

[ThomasW]

Brian,

Jon's attending a conference in Chicago this week, so his 'net' access maybe limited as well his access to his personal files.

HERE's a link to the schematic for the M8a-MTM box, that should give you some idea as to how Jon's XOs are designed.

[Hank]

Me too. When you get time Jon, I'd also like some "real" measurement data to play with, as I finally got LspCad loaded on my computer.


Thanks, Thomas.

[TacoD]

I just copied the electrical layout of one of Jon's filters. Then the real fun started. Changing components values to get a feel of what's happening. In this way I was able to tune the curves for my projects.

I used my own measured impedance and frequency plots. This is very important, as is the off-set paramters of the seperate drivers in lspCAD. I make a combined measurement of all woofers and play with dZ parameters so that the simulated summed frequency of the seperate drivers falls together with the measurement. I measure the value of dX and dY with my ruler.

I would refer to the tutorial of lspCAD .

[AndrewM]

I don't know if this is similiar to the filters Jon uses, if so there is some good info, if not then just disregard - http://ldsg.snippets.org/FILTERS/Cuadra/elliptic.php3

[Brian Bunge]

Thanks Thomas. If I'm looking at the filter correctly, the cap and resistor across the + and - leads are the zobel and the other components act as the "filter". I must admit that it's rather strange looking.

If anyone has anything to add please feel free!

[Steve Goff]

Brian, in the schematic Thomas provided, C2041 and C1031 are the added elements that make it a Cauer filter. It is basically a fourth order filter with a series capacitor added to the last element of the high pass filter and a capacitor parallel to the last inductor on the low-pass side.

[Hank]

Andrew, that's it.
Brian, yes, deceptively simple, BUT many, many hours of sweat equity on the part of the Poohbah's. Steve's succinct description says it.

[Davey]

The Zobel is interesting on this design because C1061 is such a large value...I'm not sure why this is. The 100uF would certainly compensate the rising inductance of the M8a, but it's effect would be felt all the way down at low frequencies as well.

Davey.

[JonMarsh]

It's more than a zobel. Along with the first series inductor, the RC network helps determine the baffle step compensation.

Mr. Caudra sort of has the right idea, but if you look at the response profiles of his networks, especially the pass band and stop band ripple, he hasn't fully optimized them.

A single stage cauer-elliptic filter willi have equal amplitude pass band and top band ripple. Minimizing that ripple is important, in both areas, because it's a non-ideal component in the main response area, and also is an equal amplitude "bounce back" in the stop band, or attenutaion region, where, ideally, you want to keep the driver pass through at a minimum.

I did a lot of investigation into cauer-elliptic filters back around 1990-91, when I was developing some Class D power stage circuits and output filters using cauer-elliptic filters. Especially, I was concerned about "non-ideal" behavior of filters with real world components, and did a fair amount of modeling and analysis of the impact of ESR (equivalent series resistance) and ESL (equivalent series inductance) inherent to available components, and the impact on the actual filter transfer function. Mind you, these were filters tuned to optimize the stop band behavior at the amplifier carrier frequency, which was 500 kHz. Another factor was variation in loudspeaker load impedance, and how this affected the filter response. I came up with some modified versions of the filter, with additional components, which stabilized the filter characteristics for component parasitics and load impedance variations. Along with all the other gory details, this was presented at an AES conference, and subsequently re-published with some updates in the AES journal. I also discussed SMPS architectures and issues for class D amplifiers in that paper, as well as complete SPICE modeling of the feedforward Class D amp I developed and built.

If anyone is curious, I do have scans of the original article, coverted to a PDF file; since they're bit maps, it's a bit large.

The Cauer-elliptic filters I use in speakers like the 8" two way bookshelf, the Arvo Part, and the M8ta are "hybrid" filters in that they're based on a two stage 4 section design (like any standard 4th order ladder filter), with an additional series or parallel reactive element. The filter coefficients are tuned to produce a corner knee and roll-off rate corresponding to a specific acoustic transfer function target (such as 8th order L-R, or 6th order L-R), INCLUDING the transfer function of the driver. Outside the transition region and stopband region, they're intended to be maximally flat, excepting any contouring for the cabinet/driver response, such as baffle step compensation.

Mr. Caudra basically has a good idea, he just needed to take his understanding of the filters and how to implement them to a specific transfer function target (chosen for specific acoustical properties) a bit further.


~Jon

[ThomasW]

Gees Jon, post something we don't already know .... :roflmao:

[Hank]

I think I need a tequila. :E

[morbo]

Hi Jon, I'm new here after stumbling across a link to this forum on diyaudio.com. I saw this thread and wanted to thank you for sharing your work with these drivers!

I have been modelling these in a slightly smaller and slightly higher tuned box, but I noticed that several times you made reference to using the alignment above IF the boxes can be a good way out from the walls. The speaker I'm designing is going to be used near a wall (back of speaker is 2" or so from wall, drivers are 17-19" from wall).

Should I be aiming for a different response curve (maybe sealed?) for a speaker this close to the rear wall, or is the gently sloping overdamped ported response still a good choice?

[JonMarsh]

Welcome to HT Guide!


My "normal practice" is this lower tuned alignment, generally a bit below the driver FS, because in combination with room lift, you can get a smooth, deep, but articulate sounding in room response.

If the cabinets are on the wall, then in principle, there is no transition from 4 pi to 2 pi room response, and there is no additional LF room lift. In this case, the arguement might be to go for maximally flat alignment. Both box size and port tuning have their affects; depending on the driver Qts, you can sometimes keep a relatively low tuning, but using a smaller box; the response won't be maximally flat, the Q will be lower, as will the output level at the box Fb, but the subjective response is fairly tight, clean bass, and of course some cone travel reduction from the port. I still prefer this.

The original M8 "bookshelf" is perhaps suboptimal on enclosure size (40-44 liters for the M8a 8" driver), but tuned it 32 Hz, it has a slow roll off in the box until the Fb, then dies more quickly. This sounds cleaner and tighter in most situations than going for a B4 alignment to the box Fb, with the sharp 24 dB/octave drop below that. If you look at the predicted transient step response in Unibox, it also settles faster than the normal B4 alignment.

Just some things to think about...

So, my recommendation (based on personal taste and experience) would be to go for the lower tuned, gently sloping alignment, or go sealed, if you're crossing to a sub. But then, I'm not a fan of speakers with extra punch in the kick drum area, or a fat midbass on standup acoustic bass- some folks are, and for them, this alignment might not be preferred... my reference for bass quality is dipole systems, and for a ported box, this is as close as it gets.

~Jon

[morbo]

Thanks Jon, I think I will go with about 60-65 litres, tuned to 22-25hz. I guess worst case scenario I can stuff the ports if things are too boomy in-room.

Do you see any problems crossing this woofer to a small widerange driver using a 1st order slope at say, 500hz? The small driver is the 3" TB-871, in its own sealed subenclosure it will have an f3 of ~ 150hz. I know this driver is frowned on in these parts (did a search last night), but this speaker is intended as a budget full range system, to be driven with a bottom of the line reciever, used for watching TV, movies, video games etc. I've used the little TB extensively and IMO it is adequate for this application, low cost =! low quality, just look at these Daytons! I am having a little trouble deciding how to crossover though. I have little in the way of measuring equipment (Ratshack SPL meter), though I do have access to a friends unopened copy of LSPcad 5. Any ideas for a relatively simple way to proceed?

[JonMarsh]

Well, at the minimum, you could use the measured data which PE supplies from CLIO to get a crossover in the ball park with LspCAD. The minimum crossover I'd suggest, based on reasonable roll off rates and suppression of out of band stuff, plus general power response behavior, is a 2nd order Bessel. Any slower roll off and you won't suppress the cone break up stuff from the Dayton's adequately, even for a low cost design, IMO.

LspCAD 5 std will work fine for this kind of project; expect to read the manual a few times to get familiar with the concepts. Especially the installation stuff, as you have to install the program, then navigate to the program directory and run the program which installs the copy protection software interface, and only then should you run the program itself. Otherwise, the file which sets up the copy protection interface so that LspCAD will run actually gets erased. And you have to re-install, or copy it from the CD. Ingemar's web site used to have pretty good info on this setup, but now he's switched over to supporting LspCAD 6- which is quite nice, but uses a USB dongle for copy protection.

~Jon

[morbo]

*oops! double post*

[morbo]

I took your advice and loaded in the sample files from the PE site into LSPCad. Although the graph I get in LSPcad for bass response doesnt look much like the ones you posted earlier, I do see what you mean about the filter... first order isnt an option, those peaks >1k are not down far enough. Now if I can track down similar measurements for the 871, I'll be in business. Thanks again for your suggestions :T

[Brian Bunge]

Jon,

Speaking of the CLIO files from PE, I've been using those to get the feel of the filter program from LspCAD. I'm getting pretty good results with it but am not sure how the actual measurements are taken for the PE stuff. Do you happen to know about this? I just wonder if they are taken at 1m with the driver mounted on an infinite baffle or something different. If it is on an IB, how do you deal with baffle step? I've been using the optimization tool with 200Hz as the lowest frequency to be optimized but I don't have any idea how this will sound once I mount the drivers in say a 8" or so wide enclosure.

[JonMarsh]

The PE measurements seem to be taken with a fairly short sampling window (based on lack of low frequency detail) and some smoothing. There's no meaningful data below 200-300 Hz. (I have CLIO, both DOS and Windows versions, so I'm pretty familiar with what the plots look like based on settings). They do appear to be done on an IB, based on comparing them with my own measurements.

If you don't have a measurement setup, one way to work around it would be to use BDS (from the FRD consortium) to estimate the baffle loading effects (an 8" baffle is pretty narrow; will move baffle step up to 1000-1200 Hz), and add in a compensating LF gain/mid attenuation. Depending on where you plan to use the speakers ultimately, somewhere between 3 and 6 dB total will be right. Where do you plan on placing your speakers? This will affect the degree of baffle step you may want to use. I'm a little old school, and use nearly a full 5-6 dB in most cases; it's better to have a speaker sounding a little warm or full on the bottom end than the other way around, IMO.

As inexpensive as a Behringer 8000 mic is, I'd recommend picking up one of those; in combination with an MAudio preamp, you can be up and running with Just MLS with almost any kind of computer.


~Jon

[TacoD]

As inexpensive as a Behringer 8000 mic is, I'd recommend picking up one of those; in combination with an MAudio preamp, you can be up and running with Just MLS with almost any kind of computer.


~Jon

That is what I am using, Just MLS with a Behringer 8000 mic + Behringer UB802 as preamp. Measuring the drivers in the actual cabinet, really helps with designing the x-over (bafflestep and acoustic centres).

[Brian Bunge]

Jon,

I've looked at the BDS a couple of times and even followed along with one of the tutorials. I do alright at the beginning where the tutorial shows how to set everything up and then somewhere along the way I just seem to get a bit confused. I think it's when I start trying to modify the baffle dimensions by dragging the corners of the shapes that mucks me up. Maybe I just haven't looked at it in the right state of mind yet.

Concerning speaker placement, the front baffle will probably be right around 2' out from the front wall and a 3'-5' from either side wall. This places my speakers just forward of the TV and the audio rack and just inside the doorways on either side of the front wall. One doorway leads into the kitchen and the other into the dining room. Oh, the joys of an open floor plan house.

I assume if I were designing a small monitor sized speaker that would be mounted within a few inches of the wall with some sort of bracket or placed on a bookshelf then I could probably get away with not using any sort of baffle step compensation. That's what I've been playing with so far with LspCAD so I could get a decent idea of how to use the program. If I can figure out BDS then I think I'll be in business.

Concerning a measurement setup, I have a mic from Kim Girdian (sp?) and a preamp that a friend of mine built for me that works with that Panasonic mic capsule but this doesn't work well at all with my laptop. I need some sort of pre that can work through the USB port as my mic and and headphone out jacks don't seem to be cutting it.

morbo,

Hank and I are very fond of the 871 drivers, at least for what they are. I have been toying with the idea myself of using a side firing 8" woofer in a tall, slender cabinet with an 871 handling everything from 200Hz up. I just haven't had the time to play around with that. I think the original Dayton 8" woofer would work pretty well. Hank and I built a few small subs using this driver and were getting great results down to 30Hz or so. As a matter of fact, port chuffing seemed to be the limiting factor for me using a single 2" port. I was hearing it from 10' away when I cranked up the sub a bit. If you do find some sort of frd and zma file for the 871 please let me know.

[JonMarsh]

Brian,

BDS is a real pain to use... in fact, I think I found the only way that worked consistently for moving the box edges and drivers was the arrow box settings on the lower left- same with moving the drivers around and so forth. Had a bit of a learning curve, it did, but then I tend to like to just jump into things and perhaps didn't pay enough attention to details in the operating maual.

What kind of laptop do you have? I'm also messing with my Compaq A64 laptop, and running the line output of my MAudio DMP3 into the "mic" input, with the gain turned down, worked fine. Same with using the headphone out as a line out. This is for when I'm too lazy to break out my B&K mic and HP preamp and my tower measuring PC with CLIO. The problem I've seen and heard about with some of the digital or USB out preamps is latency- delay. Would probably be better to get a good total outboard solution for USB2 (at least the with full line in/line out), and connect the mic preamp/electronics to it.

Later in December I'll have some measurements of the 7" RS180 on the PE MTM cabinets, which are about 9" wide- that might be helpful for you, as at least the baffle width is comparable.

At 2 foot out from the wall, you'll need some baffle step comp. I'm looking at the same situtation with designing some RS180 cabinets for HT (my HT FPTV in a "nook" setup, with new home organization), so what I'm planning on doing is measuring them in that position and using that data to decide on final baffle step. I've got no problem sharing data if you're not in a hurry, as the PE cabinets are just ordered and won't be here for a week or so.

~Jon

[Brian Bunge]

Jon,

I've got a Compaq Armada E500 laptop. I tried for quite a while to use it with TrueRTA and never could get a decent calibration when looping back the output to the input. I did buy some tiny little unit from M Audio that I think one of you guys recommended for a good line out option. I can't remember what the damned thing is called right now but it looks very similar to the M Audio Transit both in appearance and discription. For whatever reason I never tried to use it so maybe it would work for me if I gave it a shot.

Another issue is that my laptop needs a new battery as it won't even power up without being plugged into the wall. If I ever get back in decent financial shape maybe I can get all these issues taken care of!

[JonMarsh]

Yeah, it's scary what they get for batteries these days, especially companies like Sony. At least the big 6600mA hour battery for my Compaq actually runs the machine for 4-5 hours.

I've used True RTA without any problems on my Compaq- using the Maudio DMP3 preamp. It even seems to work pretty well down in the low end. But I'm looking around at the outboard solutions (things like the Transit) or even an M-Audio Audiophile USB (I like the full size connectors and better A/D - D/A, and AC powered is not an obstacle for me). I've got one of the latter on order from a local vendor- Central Computer- even with sales tax in CA, they're cheaper than the other online sources I could find.

[capslock]

RS 125, 150, 180 construction thoughts

Just received a surface (sea) parcel from PE with RS125, RS150, RS180. Had to pay loudspeaker duty on the item "shipping". ARRGLL! It's not worth to write a letter of complaint to fight for a refund of a few bucks, but this is the third times this happens.

Haven't gotten around to doing measurements yet. Build quality is good, except for the RS150 where the VC former is bent (to the outside, luckily) in several places on both drivers. I know one should not judge a driver by its appearance only, but here are a few thoughts:

- Cone shadowing is terrible on the RS125 and 150, still not too good on the 180. I wonder if it is possible to cut a groove into the shielding cup and remove it. On the 125, the cup overlaps the tope plate considerably. So grinding this overlap off might already help. A non-shielded version would really be a treat (and would save shipping cost, also).

- Surrounds are synthetic rubber, not real rubber like even the humble Vifa TC series. This might account for some of the cone edge issues.

- Spiders have about four rolls, some are even half-cupped. Just as a tendency, flat spiders with many rolls are the most linear and resonance free.

- The cones are relatively thin and slightly curved. Only the RS180 has the edge of the cone angled backwards at 90°, like the Seas L series, which makes the cone stiffer in the tangential direction. All cones can be bent quite easily in the radius direction, i.e. one would expect concentric modes. The 125 and 150 feel also pretty soft for tangential bending (i.e. bending between three fingers), but by for not as soft as a HDS or Vifa paper cone.

(- The RS225 does not seem to have this angled edge according to Jon's pic. Maybe the 180 is quite different from the 225?)

- I found Jon's results on near field vs. 1 m that he measured on the RS225 interesting. I don't think Darren uses too much smoothing. He captured the sharp 4 kHz dip in the Euro 7 that is missing in some magazine measurements. So it must really be due to far field addition that the dip at 1.5 kHz can no longer seen. It makes me wonder what kind of nasties are hidden in other, highly respected drivers that measure flat at 1 m. If it is all about addition, on would expect some of those nasties to turn up in a 30° farfield measurement, right?

[JonMarsh]

Just received a surface (sea) parcel from PE with RS125, RS150, RS180. Had to pay loudspeaker duty on the item "shipping". ARRGLL! It's not worth to write a letter of complaint to fight for a refund of a few bucks, but this is the third times this happens.

Haven't gotten around to doing measurements yet. Build quality is good, except for the RS150 where the VC former is bent (to the outside, luckily) in several places on both drivers. I know one should not judge a driver by its appearance only, but here are a few thoughts:

- Cone shadowing is terrible on the RS125 and 150, still not too good on the 180. I wonder if it is possible to cut a groove into the shielding cup and remove it. On the 125, the cup overlaps the tope plate considerably. So grinding this overlap off might already help. A non-shielded version would really be a treat (and would save shipping cost, also).

- Surrounds are synthetic rubber, not real rubber like even the humble Vifa TC series. This might account for some of the cone edge issues.

- Spiders have about four rolls, some are even half-cupped. Just as a tendency, flat spiders with many rolls are the most linear and resonance free.

- The cones are relatively thin and slightly curved. Only the RS180 has the edge of the cone angled backwards at 90°, like the Seas L series, which makes the cone stiffer in the tangential direction. All cones can be bent quite easily in the radius direction, i.e. one would expect concentric modes. The 125 and 150 feel also pretty soft for tangential bending (i.e. bending between three fingers), but by for not as soft as a HDS or Vifa paper cone.

(- The RS225 does not seem to have this angled edge according to Jon's pic. Maybe the 180 is quite different from the 225?)

- I found Jon's results on near field vs. 1 m that he measured on the RS225 interesting. I don't think Darren uses too much smoothing. He captured the sharp 4 kHz dip in the Euro 7 that is missing in some magazine measurements. So it must really be due to far field addition that the dip at 1.5 kHz can no longer seen. It makes me wonder what kind of nasties are hidden in other, highly respected drivers that measure flat at 1 m. If it is all about addition, on would expect some of those nasties to turn up in a 30° farfield measurement, right?

Interesting comments...

I've seen this with some ScanSpeak driveres I've measured, and MarkK has seen it in some of his tests. This is why I don't trust the published response curves of anyone- though if they include impedance curves also, I'm a little more comfortable in making an assemssment about whether I want to evaluate the drivers.

In a couple of weeks I hope to get testing of the RS180 done, and by the end of the month, perhaps the RS270, also. For the latter, I'll have to build a test enclosure, as I don't have anything on hand.

The rear masking is something which bothered me about even the RS180, but in my mind was very quesitonable with the smaller drivers. I've fought that problem with some other 5" woofers in the 80's, and so for me, the Adire Extremis 6 is a real breath of fresh air...

~Jon

[morbo]

Brian - Thanks for the vote of confidence about the TB! I know its not a proper 'hi-fi' driver, but it does a lot of things right if implemented correctly. I will in fact have measurements of the TB on a 10" baffle and if needed, a 8" or 6" baffle as well sometime around the new year; I decided if I'm going to do this I'm going to do it right, so I am ordering a Behringer ECM mic and preamp. I'll let you know when I get them and find out what measurements would be most useful to you.

I have been reading the LSPcad and JustMLS manuals, wow there is a lot to learn here 8O But I'm looking forward to it, I'm pretty young and if I get the right equipment & some knowledge now I hope to be able to make a lifelong hobby out of this. Who knows, one day I might actually get good at it

For now I've been playing with a theoretical in-box response for the 871 and the Parts Express measured FR and IMP data. It seems 2nd order somewhere around 500hz should work. I have been making changes manually, trying to get a feel for what the various parameters do. A couple of questions for anyone who uses LSPcad:

1. Do you use the crossover optimizer? It seems to me that the optimizer tries to get the flattest possible on-axis reponse, is there a way to make it optimize for other parameters, say, flat impedance or minimal group delay?

2. I have modelled several 'theoretical' crossovers now, and I almost always end up with a dip in off-axis response around the crossover frequency. Is this unavoidable? I can get it to the point that the off axis response falls off evenly, to a maximum of about -7 db at 90deg, and the off-axis curves looks fairly similar to the on axis curve, just lower in that region. I didn't think that dispersion would be a big issue when crossing this low.

3. Is there resource somewhere that tells you what you should shoot for? By that I mean, something that would show you what a 'good' group delay curve, a 'good' impedance curve, or 'good' impulse response should look like?

[capslock]

Jon,

I have some Extremis 6 on preorder also, but I am worried about the poly cone. But $69 is a good price for the motor alone, and I have been thinking to salvage the motors and use them on the Seas L18 (H1142 with the straight cone).

I seem to remember you are a big fan of the HiVi midwoofers. Some of those have been tested for FR, CSD and distortion in the German magazines Klang & Ton and HobbyHifi. While the K&T CSDs are worthless and the distortion results sometimes hard to understand, I have found the HH results quite conlcusive.

If you have specific models you are interested in, I can try to find and scan a review. Most of those HiVi drivers were average at best, though. It also surprised me to see how poor nearly all Tang Bands are, as they seem to be everybody's darling. Actually, I have a pair of mini speakers using W3-881S that I find pleasing.

What you wrote earlier on about penny wise and pound foolish is all too familiar. We have been through this a couple of times. I am sure, though, we are not working for the same company, as we don't have a Livermore office.

My real favorite is that we do a travel planning at the beginning of each year, announce and plan our travels about two months ahead of the actual date. Then along the line of people who have to sign the travel request, each of them will procrastinate the decision and then ask the guy on the lower level if the journey is really necessary. By the time the journey is approved, it is usually 1-7 days before departure, the pre-reservation for a reduced price ticket has run out, and a ticket at twice the price is purchased. Make sense?

Greetings,

Eric

[JonMarsh]

- The cones are relatively thin and slightly curved. Only the RS180 has the edge of the cone angled backwards at 90°, like the Seas L series, which makes the cone stiffer in the tangential direction. All cones can be bent quite easily in the radius direction, i.e. one would expect concentric modes. The 125 and 150 feel also pretty soft for tangential bending (i.e. bending between three fingers), but by for not as soft as a HDS or Vifa paper cone.

(- The RS225 does not seem to have this angled edge according to Jon's pic. Maybe the 180 is quite different from the 225?)

I can confirm this is the case. It's a curious difference, I'll agree. I'm looking forward to getting the RS180's mounted and tested. I have a smaller Woodstyle enclosure which I use to test 6-1/2" drivers (like the carbon fiber MCM, or the Peerless HDS) which it may fit into; otherwise, I'll test in the X1 cabinets or the new PE's when they get here and I can route the front panels.

I have some Extremis 6 on preorder also, but I am worried about the poly cone. But $69 is a good price for the motor alone, and I have been thinking to salvage the motors and use them on the Seas L18 (H1142 with the straight cone).

I'm suspicious of their behvaior over 2 kHz, and anyone (Adire inlcuded) that thinks they're a good candidate for a 3 kHz crossover must be smoking something other than Marlboros... maybe they're from Amsterdam.

Besides the driver cone modes, there's the issue of wavelength separation- shouldn't be over ~ 4.5" ctr to ctr, at 3 kHz, and that's the charitable criteria, not the strict criteria. Not going to be doing that with a standard 7" driver and standard tweeter, are we?

In the main application I bought these for, a diople line source, they'll be crossed over at no higher than 600 Hz - maybe as low as 400 Hz. They'll be going down to about 50-75 Hz on the bottom end. In the planned dipole panel, at 50 Hz 8 of these can do about 107 dB. That may not be loud enough for Hank, but we'll see. More on that later...

I seem to remember you are a big fan of the HiVi midwoofers. Some of those have been tested for FR, CSD and distortion in the German magazines Klang & Ton and HobbyHifi. While the K&T CSDs are worthless and the distortion results sometimes hard to understand, I have found the HH results quite conlcusive.

Mark K has done some good non-linear distortion and energy storage measurements on the M8n, along with several other 8" drivers, including SS, Seas W22, some Vifas, and the Dayton RS225 prototype- this is when the excellent performance of the Dayton came to light. The M8 tested in the middle overall in performance- wouldn't quite run with the top dogs, but still pretty respectable.

I evolved into using the M8 when developing an 8" two way system for a friend which required realtively low cost drivers and good wideband performance- the M8a cone is one of the best behaved 8" diaphragms out there (most have serious problems starting below 1 kHz). The W22 is good, at much greater cost, but it has energy storage issues which manifest in the dip right after 1 kHz, and really shouldn't be used any higher than I use the M8a (1.2 kHz crossover). At less than half the price of the W22, the M8a is fairly compelling. The goal was low cost balanced with good perforamnce, especially total power response, and the folks at AudioXpress were pretty happy with how that turned out- so have been most of the folks that build them, though they think I'm a little crazy when I urge them to drop in a big bucks SS 98000 to upgrade the high end. This driver works very well as the midrange in the Arvo Part, as crossed over at ~175 Hz, two are not stressed at all.

But now I'm going to see if I can make a good two way work at 1 kHz with the Dayton. The LF performance (non-linear distortion and energy storage) below 400 Hz is excellent by any measure. A steep 1 kHz crossover may just be too high, though. We'll see. Of course, some would say it's too low, citing the IM products of the Avalon Eclipse, but I'm using a very different crossover approach and driver.

What you wrote earlier on about penny wise and pound foolish is all too familiar. We have been through this a couple of times. I am sure, though, we are not working for the same company, as we don't have a Livermore office.

My real favorite is that we do a travel planning at the beginning of each year, announce and plan our travels about two months ahead of the actual date. Then along the line of people who have to sign the travel request, each of them will procrastinate the decision and then ask the guy on the lower level if the journey is really necessary. By the time the journey is approved, it is usually 1-7 days before departure, the pre-reservation for a reduced price ticket has run out, and a ticket at twice the price is purchased. Make sense?

Well, the concept sounds famaliar, though we haven't gotten bogged down to that degree yet. There are expected to be more restrictions on travel this year, but since they made choices the previous year to de-centralize a number of operations in our group, and since customer face to face contacts are essential, I don't see the possibility of changing that- not for me. I had 39 customer visits last fiscal year, and three internal "workshop" trips, one to Europe, two to Singapore.
Approvals for mundane things like IT or PC equipment now have to be routed back to Europe- there's no one smart enough or capable enough to make a decision about a new PC in the US? Give me a break....

BTW, I work for a German Semiconductor company....

I hope you can keep us informed of what you find and do with your Daytons, as well as your experiments with the Extremis 6. Looks like the Extremis won't ship before around mid December.

~Jon

[JonMarsh]

I have been reading the LSPcad and JustMLS manuals, wow there is a lot to learn here 8O But I'm looking forward to it, I'm pretty young and if I get the right equipment & some knowledge now I hope to be able to make a lifelong hobby out of this. Who knows, one day I might actually get good at it

For now I've been playing with a theoretical in-box response for the 871 and the Parts Express measured FR and IMP data. It seems 2nd order somewhere around 500hz should work. I have been making changes manually, trying to get a feel for what the various parameters do. A couple of questions for anyone who uses LSPcad:

1. Do you use the crossover optimizer? It seems to me that the optimizer tries to get the flattest possible on-axis reponse, is there a way to make it optimize for other parameters, say, flat impedance or minimal group delay?

2. I have modelled several 'theoretical' crossovers now, and I almost always end up with a dip in off-axis response around the crossover frequency. Is this unavoidable? I can get it to the point that the off axis response falls off evenly, to a maximum of about -7 db at 90deg, and the off-axis curves looks fairly similar to the on axis curve, just lower in that region. I didn't think that dispersion would be a big issue when crossing this low.

3. Is there resource somewhere that tells you what you should shoot for? By that I mean, something that would show you what a 'good' group delay curve, a 'good' impedance curve, or 'good' impulse response should look like?

1. The optimizer is only a tool, who's usefulness is a great as the insight you bring to it. I do use it, and in the Pro version, you can specifically set impedance minima, which gives it a further constraint. I often save several net versions as a work through optimizing the design, using the save/recall function. I also don't let it work willy nilly on every component.

I'm a little OCD, perhaps, so in doing a design, first thing I do is develop the impedance control zobels, and I normally don't optimize them, except as a final tweak for slight slope adjustments in the passband.

Then I build up the main network, define the acoustic transfer function target, import the driver data, set the driver radiator diameter (critical to off axis simulation), and set the driver positioning relative to each other mimicing the actual cabinet. Then I'll use the optimizer to get the actual acoustic transfer function in place.

Horizontal off axis response is generally a function of using the drivers in the range for which they have broad dispersion. (assuming vertical stacking of drivers) For an 8" driver, a crossover no higher than 1250 Hz should be used. For a 7" driver, ~1500 max. Most driver selections and crossover frequency combinations I see people using will have inherent off axis power response problems.

Vertical off axis response is a function of driver size, driver spacing, crossover frequency, and filter function/target. The quasi LR8 network I use has rather good vertical dispersion, which is often difficult to get. I say "quasi", because the transition band region is modified a little in order to optimize the power response and phase through the crossover point. Unpatented secret sauce, you know.

One of the guys over at the Mad board and some friends did an experiment to evaluate crossovers by using two identical drivers, and making a crososver point well within their working range, and listening for differences between the different network types- BT, DT; very illustrative, and I recommend the exercise for anyone who wonders how different filter behaviors are perceived acoustically.

Last, your item 3, how important do you think the impedance curve is to the final loudspeaker response, if your amp is comfortable with it? If you use non feedback solid state amps or tube amps, you want to take more care, because the impedance curve variations can cause power transfer variations due to the output impedance of the amplifier. I genearlly shoot for controlling the impedance curve within a 1:3 or 1:2 range. If you don't use full zobels on drivers, you'll never hit that target, but in many cases, it's just not necessary.

Group delay is a function of crossover filter order and Q, as well as driver behavior. Best to do some reading in studies about audibility of group delay. Many folks (myself and SL included) have assumed rather stringent criteria for this factor, only to find experimentally that it just wasn't so, within reason. Also, audibility is different for different frequency ranges. 20 msec group delay in bottem end may not be as bothersome as in the midrange.

Impulse performance is a function of driver energy storage and risetime, as well as network design. I think the former are much, MUCH more important than the latter. I spent the 70's building time coherent speakers that reproduced pulses very well. I don't do that anymore. But now I build 8" two ways that out perform 10" four ways.... except for that square wave business. Tradeoffs...


~Jon


~Jon

[Davey]

Jon,

I picked up a set of RS180 drivers and mounted them to my spare dipole MTM baffle. I've done a series of measurements and they generally look pretty good with regard to polar response. In spite of how the photo makes them appear they are essentially just as well "vented" as the Seas drivers. Of course the huge bucking magnet and shield cup create quite a different "look." I think I will have to back off my statement in that other forum that these drivers (RS180) are not suitable for dipole usage. They look to be just as suitable as the W18/CA18/L18 series of drivers from Seas. They would present some additional crossover issues that the CA18 driver wouldn't, but probably not unsolveable.

Best,

Davey.