PE Dayton Reference Series

[JonMarsh]

I've had a few inquiries from folks about Parts Express new Dayton Reference series, with aluminum cones, sheilded magnets, phase plugs, cast frames, etc., especially since Mark K got some very nice test numbers on an early prototype he evaluated.



Specifications: *Power handling: 80 watts RMS/120 watts max *VCdia: 1.5" *Le: 1.0 mH *Znom: 8 ohms *Re: 6.4 ohms *Frequency range: 30-2,000 Hz *Fs: 29 Hz *SPL: 88.4 dB 2.83V/1m *Vas: 2.37 cu. ft. *Qms: 1.80 *Qes: .47 *Qts: .37 *Xmax: 7 mm *Dimensions: A: 8-3/4", B: 7-3/8", C: 4".
Long-excursion motor and suspension for strong bass performance
Subtle yet high-tech look makes a bold cosmetic statement
Ultra-low stray magnetic field allows extremely close proximity to CRT's
Designed and engineered in the U.S.A.



SO, just for the record, I have ordered a pair to evaluate. There's not a lot of info posted on PE, just the T/S parameters, no sweeps. But it is pretty promising; for example, Xmax is 7 mm, while it still has pretty decent sensitivity, 88.4 dB. And that's for an 8 ohm driver (RE of 6.4 ohms).

The 64 dollar question, is would it be adaptable to an M8a based design with a little effort? Mark K measured some VERY respectable distortion numbers; in the area below 1 kHz, this puppy runs with and past the big dogs. Forget your Seas W22.

So, in our never ending quest to bring excellence for cheap, I'm going to take a closer look. This pair may wind up in my M8ta's.


~Jon

[TacoD]

Very nice specs indeed, but to me the Le looks a bit high. It's a shame those drivers are not available in my country...

But if I don't want to cross that low (1 kHz), is 1500 Hz feasable?

[JonMarsh]

The HF impedance curve is very comparable to SEAS W21 and SS 8" drivers, surprisingly, so the spec may be off.

Why use this driver? Mark found the distortion below 100 Hz to top the SS and SEAS Excel drivers, with about 5 dB more headroom before things got really ugly. Mid band linear and non-linear distortion was also excellent.

Because of cone behavior (a common problem with 8" drivers), a 1500 Hz crossover would be too high, especially with conventional crossovers. I'm thinking I may even have to go lower than with the M8a, which I usually use at 1200 Hz, with an 8th order elliptic crossover; probably will drop to 1 kHz. May try a Millenium Excel tweeter, in addition to the Hales I have on hand.

~Jon

[TacoD]

I was thinking of a cauer filter, I've tried one in a 7" Eton (with Heatpipe) setup. And it works very well, it sounded more open than a 1st order x-over with a couple of notches. The x-over is around 1300 Hz coupled to a Eton ER4. I find it difficult to create these x-overs, hard work in lspCAD , but they sound very good. Although for SS and AT woofers I prefer more conventional x-overs.

p.s. I saw some measurements from a Avalon Eclips (made by Stereophil) and the freq. plot showed the same sort of bumps as in a caucer filter. So can I conclude its a cauer filter ?

[Brian Bunge]

Jon,

Have you run any sims on the 8's based on the specs on the PE site yet? I'm getting ported enclosures around 45-50L tuned to 30Hz for them. IIRC, the 10's need around 100L. I'd almost say that sealed enclosures would be more appropriate for the 8's and 10's, especially for dual woofer designs.

[JonMarsh]

Yeah,

If you wanted a bessel sealed alignment (Q of 0.566), it works out to about a 22.5 liter net volume; F3 before room gain is about 60 Hz, but with 5-6 dB of room gain and positioning out from the walls, you could get roughly flat to 40 Hz with -4 dB at 30 Hz- nothing to sneeze at. But max excursion limited output at 30 Hz (before room gain) is about 92 dB; not quite blowing the doors down. Drops to 84 dB at 20 Hz.

Now, in my M8ta enclosure, things look pretty interesting; this sucker comes on like a mini HE 15, for being an 8' driver. With box tuned to 24 Hz, the F3 is 22.9 Hz before room gain. The max output at 30 Hz before room gain is 100 dB, at 24 Hz about 104 dB, and at 20 Hz is still about 92 dB. Factor in room gain, and these numbers only get better.

If one is willing to give up a skosh in the lower mid bass, IMO a 22 Hz tuning looks even better, as it give a more controlled roll off, F3 at 39 Hz, but then a nice flat plateaur below that almost down to 20 Hz. Would make room position optimization fairly easy. Max output at 30 Hz drops slightly, to 98 dB before room gain, but at 20 Hz it picks up to 96 dB before room gain.

I can see a good arguement for a sealed dual driver box, Q of 0.5; Fb at -6 dB of 40 Hz, 25 Hz is down only another 4.5-5 dB, and you could hit about 94 dB at 25 Hz before room gain, 100 dB at 35 Hz. And this only takes about 40 watts.

It also occurs to me that six of these per side might be fairly nice for a line array to match up with my RD50, would offer comparable net swept volume to 8 of the the longer throw but smaller cone Extremis midwoofers, and would cost a whole bunch less - less than half as much. No XBL2 motor, though. But would work great with a 600 Hz crossover.


Hmmmmm. So many things to think about!

~Jon

[Ten 99]

x-over limiting the tweeter options?

Jon,

Did I read you correctly, when you stated that using this new PE Dayton Reference speaker, you feel that crossing it at 1k will be necessary. You spoke about using the hales and the Seas Millenium tweeters as options. Does this mean that it would pretty much exclude using tweeters like the Vifa XT25?

Using the Hi-Vi M8a ($63) and the Vifa XT25 ($59) keeps the driver cost of the M8Ta down to about $125 or less. Using the Dayton 8" Reference ($44) and a Seas Millenium ($200) bring the cost to pretty much double ($245) for the drivers cost. I know that preference is to use the SS 2904/9800 to the XT25, with an increase to about ($183). The nice thing is that since the XT25 and SS9800 are so close electrically, it is easy to upgrade later to the nicer tweets.

Please let me know if I'm off base on this? I really liked the option of upgrading the tweeters later and being able to keep the initial cost down. I figured I could recycle the XT25's into another project later (like my car).

By the way, how do those SS2904/7000 tweeters perform and sound?

Chris

[JonMarsh]

Well, now, the big Seas Millenium is "only" $155 or so, USD. Kinda pricey, but it's got a really great motor, lots of Xmax for a tweeter.

The problem with the Dayton is that it starts getting into trouble around 1.5 kHz. The M8q starting getting into trouble around 2.3 kHz. Hence, the difference in crossover capability and requirements.

The attraction for the Dayton is the high Xmax and low linear and nonlinear disotortin. But, I wouldn't try to pair it up with a Vifa XT25. That would be pushing it too low. It's specific characterisitcs make it harder to work with on paper, and until I get something measured, built, and tested, I don't want to say whether I think it will really work out. Unfortunately, it will NOT be possible for an 8" two way to make the two interchangable- at least not for a tweeter less capable than the SEAS Millenium, I think. And since the woofers cost the same, there's no point using the M8a instead.

If you're budge constrained, then the M8a with the Vifa to start is the better choice; then upgrade to an SS9800 with no crossover mods, if need be. The M8a bookshelfs at home are run that way. Everything is close enough it works quite well, though an optimized from scratch LF zobel (as I use in the Arvo) has different values due to a different Q in the resonsnce. It only makes a small difference in the impedance characteristic in the roll off region (around 600 Hz). As the tweeter is well down there in response, there's no impact worth talking about in performance.

I'm only considering the Dayton right now with either the Hales tweeter or the Millenium. It MIGHT probably work with the SS9800, but that might be pushing the SS9800 a little too low, also. It's great down to 1200 with my funny crossover, but taking that a little lower will up the distortion somewhat. It's so clean as it is, I'd rather not do that.

BTW, the SS9800 also benefits from using film and foil caps in the crossover; I did that with my Arvo crossover, using Theta AudioCaps. Recommended, if it fits in the budget. Or a future upgrade; I use 10 uf film and foil and the balance of the value in metalized foil. OK, so I'm cheap. So sue me!

Understand where I'm coming from, I'm using pretty elaborate enclosure techniques, even with the bookshelf version, and trying to wring every bit of transparency out of the components used. A lot of times folks don't spend this effort on speakers short of something in the 10-15K range and up. But Avalon showed that you could get worthwhile improvements in transparency and musicality with a lot of attention to detail with just 8" two ways, or 11" three ways- it's a quality thing, not just quantity. Even on my bookshelfs, you can here a definite difference between my Kimber 8TC speaker cables and my Cardas Golden Reference. That may not be the case for all 8" two ways.... :^)

~Jon

[Steve Goff]

Jon, you seem to be trying really hard to stay with a two-way, despite the difficulty finding a woofer that works well both high and low. Have you thought about a three-way, perhaps using two of the Dayton Reference drivers as woofers, the 9800 as the tweeter, and a suitable metal midrange with low distortion in its pass-band. One of the reasons I'm thinking about this is the possibility of making three-way monitors all around in a surround sound system crossed over at about 40Hz to multiple front and back subwoofers. The three way would also work for a horizontal center channel, with the woofers flanking the midrange and tweeter. A three-way design might also lower distortion in the midrange, something you may ahve mentioned in connection with the Arvo. In fact, might the Arvo work in sealed enclosures, for those situations where a dipole design won't work?

[Mark K]

Jon,

One thing you might want to check out is Darren's FR curves. The breakup seems a little higher than the prototypes I tested. In the case of the 10, the impedance blips are clearly higher up than my prototype. It's hard to tell from Darren's impedance graph, but it may be higher than the prototype I tested as well.

Which is good news since you might be able to go up on the xover frequency.

P.S. How come no one wants to use the 27TDC as a budget companion. Now that rumor has it, it's no longer a production tweeter, it must even be better :W

P.P.S. I will be testing an Excel non millenium, non ferro soon, the -003.

mark

[Brian Bunge]

Steve,

I'm with you on the 3-way. I'm foaming at the mouth just thinking of an MTMWW using the 8's for the woofers and maybe the 6's for the mids. And yes, I'd really like a budget tweeter with possibly the ability to upgrade later.

Maybe we can get Jon to add this to his "to do" list?

[Dennis H]

Well, hell, if we're talking 3-way, Jon has shown us the way with the Arvo. Start at the bottom with a TC 12" (or two). Then add your favorite mid and tweet combo. The choices get a lot broader when the mid only has to go down to somewhere in the 2-400 range. As I used to say as a young racer wannabe - there's no replacement for displacement.

[Hank]

Brian, how are you? I miss trading smart-ass barbs with you.
I must say, a three-way here is tempting in order to wring out the absolute best, purest mid-range (where the soul of music lives, right, folks?), BUT, I have a Psycho-like fear of the large number of Xover components involved in three-ways. There, I've admitted my fear, and I'm proud of it.
Dare I suggest three-way ACTIVE??

Tweets: I've posted before, but I'll say again that the only tweet I've ever "heard" that stopped me dead in my tracks and had me thinking "the high notes are accurate!", was at the 2002 CES high-end hotel Joseph Audio suite. The tweet in his speakers was the Millenium.

[JonMarsh]

Jon, you seem to be trying really hard to stay with a two-way, despite the difficulty finding a woofer that works well both high and low. Have you thought about a three-way, perhaps using two of the Dayton Reference drivers as woofers, the 9800 as the tweeter, and a suitable metal midrange with low distortion in its pass-band. One of the reasons I'm thinking about this is the possibility of making three-way monitors all around in a surround sound system crossed over at about 40Hz to multiple front and back subwoofers. The three way would also work for a horizontal center channel, with the woofers flanking the midrange and tweeter. A three-way design might also lower distortion in the midrange, something you may ahve mentioned in connection with the Arvo. In fact, might the Arvo work in sealed enclosures, for those situations where a dipole design won't work?

Those are interesting suggestions, Steve. I used to do scads of three and four ways in the 70's and 80's, and 90's. The Arvo is the first three way since 1999; that last one was my X1 Klones.

In that regard, I'd say I've been influenced a lot by the thinking behind the original Avalon Eclipse, which though certain possessed of some faults (especially distortion in the tweeter from the low crossover point with a conventional crossover), nonetheless had a lot of interseting qualities. So, maybe what's been happening is that I've gotten tunnel vision on "perfecting" or taking to it's illogical extreme (all a point of view) the basic two way concept.

Three ways, done well, do get rather complicated, especially if you intend to have the speaker out a ways from the wall boundaries, and have to deal with baffle step. Doing that properly across two drivers can be tricky. That's why one of the last three ways I did was with MB Quart dome mids crossed over at about 800 Hz on the bottem, so that the mid driver wasn't really involved in baffle step. With a cone mid, and lower crossover, it gets more complicated. And while I'm not worried about production costs myself, part of why I do this is so those interested but not possessed of Croetious bank vault might be able to build them, too. I sort of stray from that idea with things like SS9800's, but gee, they sound so good! That's the best metal dome tweeter I've ever heard... handily beats my old favorite, the TC120, in shere musicality, while still being quite transparent.

But then, doing a three way, I don't like crossing over very high from the mids, for all the same reasons as for a larger midwoofer- related to driver spacing and breakup modes. Some of the Seas metal midwoofers could certainly change my mind; witness what Joseph Audio has done in their flagship. I don't think the crossover to a mid cone should be higher than about 2 kHz. Then there's the old rule about at least four octaves covered by the mid... which four? 250 - 2 kHz? 500 - 4 kHz? An Excel 7 can do the former. There's not many 5's that can do the latter- maybe the newest version of the 5-880 from Eton could cut the mustard; I think that's a little close to the resonant peak for the SEAS. 350 - 2800? But then there's that baffle step problem- which the dipole does away with nicely.

I haven't seen Darren's curves on the reference series; last time I checked, I didn't see anything posted. If the cone problems start even higher up than for the prototypes, that's really good, as long as they're consistent. How about the smaller ones, too? I wonder if they have one that would work for the mid to upper in the Arvo, or for a sealed system?

OK; just checked the site again; I have seen the light, er, the curves. Definitely looking good. :T

See, I have no common sense- I'd be curious what the 6" one would do, as the mid for a Watt Puppy sort of gig- use two of the 8's for the bottem end; the six looks like one could be pretty flexible on tweeter choice- NorthCreek D28, the less expensive Excel's, even Mark's favorite out of production Vifa!

My mental attitude about this isn't very practical- I tend to treat this too much like art- just because you have a few pictures on the wall, you don't stop playing with the paints and looking for new things to do.

Well, between these and Adire's new offerings, and the new sub drivers with XBL2 coming out this November, we're sure going to have a lot of new options to play with this fall!

~Jon

And Mark, how have your 3 ways turned out- are they done now?

Last comment- my current standard bookshelf two ways, the M8 MkIV with the 9800 have overall midrange performance that spanks my old X1's in clarity and timbral purity and accuracy. Of course, the whole system is better, and it even get's better in the Arvo setup - probably because the midwoofers just aren't trucking at all. So, I'm pretty happy with how the crossover choice and approach has worked out - but think about it, other than the slopes and driver cone materials, the true antecedent is probably an Advent speaker. Which got a lot of things, including the mids, more right than most of it's contemporaries.

[Steve Goff]

The 6 inch Dayton does look good, and is the one I was thinking about, having looked at the new data. It could be used as either a single-driver midrange or a two-driver midrange, in a WMTMW or WWMTM configuration. I'd think it would work well crossed over at about 200 Hz, with the 9800 crossed in at about 1200 to 1400.

[JonMarsh]

Sounds very solid, Steve.

So, are you going to go for it soon? The six doesn look like it would be OK up to 1400 or 1500 Hz, though it would be good to see linear distortion results.


One of the things about the Watt Puppy thing, is that it helps get around the baffle step bugaboo in a clever way; you just have to have a "woofer" that's clean enough to roll off nice and slow and easy, up to 800 Hz or so, and then kill it fairly quickly; the intial slow slope provides the baffle step. It's the old first order to third order trick (top module sealed, with LF zoble, and single capacitor to change 2nd order box high pass to 3rd order). It's kind of "cheating" for a three way, because the component count is kept down, and you wind up having a tall source from 100 Hz to 500 Hz plus, which helps deal with floor bounce, by having multiple sources. I guess that's not "cheatig", but engineering. :B

[Steve Goff]

If only I had time these days, but stuff like painting the interior of our house come first, unfortunately. And I don't even have proper tools anymore, so have to coordinate with my brother to use his shop. Maybe someday.

[Brian Bunge]

Dennis,

I just don't really have the physical space to go with something as wide as the Avro. I'd really like to have a cabinet no wider than 10"-12", although my old "stereo" subs were 15" wide with monitors sitting on top. I guess I could do that again, but I really want to do something a little more conventional.

Old Ma...errr..I mean Hank! How's it going? I'm sending you an email to let you know the latest.

[Hank]

Watch your mouth, kid! :M
I recieved your e-mail and replied. Hang in there and I hope the job possibility turns out positive for you and your family!

[JonMarsh]

If only I had time these days, but stuff like painting the interior of our house come first, unfortunately. And I don't even have proper tools anymore, so have to coordinate with my brother to use his shop. Maybe someday.

Greetings from Singapore,

Yeah, isn't it a hassle when real life get's in the way of DIY Dreams? I went through a period like that in my 30's, when I didn't have much in the way of tools at home (after moving to CA with family for Siemens), and the only times I could work on projects was visiting ThomasW.

I remember my first Xmax holiday in Livermore was spent steaming and scraping wallpaper off several walls of the new house. Just tons of fun!

Hand in there. and gool luck with the painting.

~Jon

[JonMarsh]

Waiting for me when I got home...

A nice box from PE was waiting for me when I got home....


Very solid, nice build quality, and quite dead cone when you tap it...












And they fit perfectly in the M8ta cabinet hole for the woofer!



With any luck I'll find some time for basic testing tomorrow...

~Jon

[Mark K]

I'm very curious what you think. Really, for the money, these are very, very impressive....

Good looking driver, dare I say, sexy (I know, I need help). Only thing is that little bit of VC former sticking out. Still, I'll take it for the money.

[JonMarsh]

I agree completely, Mark. At almost any price below $100, it's reasonable- at the actual selling price, I'd be a bit worried if I was some of the European biggies.

It would be even cooler if it had a Neodymium magnet and a smaller rear shadow on the cone, but that's the only thing I can think of off the top of my head! Let's face it- while most of the stuff coming out of Taiwan and China in drivers has been cheap knockoffs, when you do get someone doing a good design, at the low production prices possible, the results are scary, if you're in the business and located somewhere more conventional.

~Jon

[Andrew Pratt]

Have you had any time to test it yet Jon? how close to the M8a is it?

[JonMarsh]

Have you had any time to test it yet Jon? how close to the M8a is it?

Had to order some more connectors and wire to be able to test it! I forgot that I'd tossed out my old test enclosure for 8" drivers when garage cleaning last May. So, I won't be finished with testing until I can drop it into the M8ta enclosures, probably next weekend.

The RS225-8 doesn't have as extended a top end as the M8a, but it has greater Xmax and lower distortion (more linear motor). It may require a lower crossover point to work well, in which case I figure the only thing left is a Millenium Excel tweeter. We'll see.

I also ordered some 7" reference series to evaluate. Should be in by the end of the week or early next week.

~Jon

[Andrew Pratt]

Why the Millenium Excel tweeter over the Scanspeak one you were suggesting for the M8a box?

[ThomasW]

The lower safe XO limit for the SS9800 is the XO point we use in the Arvo design 1250Hz.

For the new woofer one needs to use a crossover point even lower than the SS9800 can tolerate. Hence the change to the Millenium Excel tweeter. It can tolerate a lower XO point, probably something in the 1kHz range.

From 1.25kHz to 1kHz may seem like a small change, but we're pushing the physical limits of what these tweeters can do with Jon's high order XO designs. So 250Hz is a significant difference.

Note that most standard 2-way designs are using XO points in the 2.5kHz or higher range.

[JonMarsh]

If a revised design using the Dayton RS228-8 requires a lower crossover frequency (say, 1 kHz instead of 1.25 kHz), even with the Cauer-elliptic filter, that will probably be a bit too low for the SS9800. Distortion in tweeters is determined by motor linearity and Xmax, and while the SS9800 has very good linearity, the Millenium Excel has greater Xmax. Not usually discussed for tweeters, but still a factor!

The first proto samples of this driver displayed problems in the 1.5 kHz area. The production ones seem to be better, and so may be able to use a crossover similar to the M8a. Because the T/S parameters and impedance aren't the same, an optimized crossover will be different, as regards component values. Also, there still seems to be a rise in the 1.5 kHz region due possibly to reflections off the large rear maget structure.

We'll just have to see.

~Jon

[JonMarsh]

The other point, with regards to the M8ta, is that the enclosure was setup for the Hales Transendence tweeter (which I may still use, but I have another possible project for those, also, requiring multiple pairs); frame size is the same as the Millenium Excel, so mechanically, that's the "compatible" alternative. for the M8ta.


~Jon

[Steve Goff]

I've been thinking a bit about my proposed three-way WMTMW, with two Reference 10-inch woofers, two Reference 6-inch mids, and the 9800. I'd like to keep the crossover to the tweeter low, so would likely try out one of your Cauer filters. Can LpsCad Pro or another program let you model and optimize such filters, or are you on your own?

[JonMarsh]

Hi Steve,

I use LSPCAD Standard 5.25, in the advanced mode; it will model these filters just fine. I've also used it for my Arvo system which is passive three way with the Cauer filter on the midwoofer to tweeter.

What do you think you want to do on the woofer to mid? 3rd order Bessel or Butterworth, or 4 th order L-R? Or asymetrical? (for example, sealed 6" = 2nd order, add a first order electrical high pass, = 3rd order, use 1st order on low pass. Done right, you can even get the low pass overlap to provide BSC. The 10, by PE's measurements, looks pretty flat to 1 kHz).

I've got a pair of 10's on order, in addition to the 7's, so I'm curious to see how they look.

If you'd like me to email a sample LSPCAD file with M8 style crossover, just PM me with your email.

Regards,

Jon

[Steve Goff]

I was thinking of doing the Watt/Puppy thing: a single cap for the high pass to the 6-inch mids in a sealed enclosure, for an overall third-order response, if the distortion is not too high. As you suggest, the 10-inchers initially would be rolled off at 6 dB per octave, providing some overlap and baffle step compensation, then steeper before they get nasty.

I had a pair of Dunlavey III's once, and I think they did something similar. I though the midrange was kinda smeared, and the highs could get distorted, but the bass to midrange transition was quite nice. I ran them full range, with a Velodyne ULD 18 II crossed in underneath, at about 35 Hz. The whole bass and midbass range of that combination was very nice.

I'll look into LpsCad, and will probably take you up on your generous offer.

[JonMarsh]

Just for reference, yesterday I modeled both the RS-225-8 and the RS270 in dual woofer setups, both sealed and ported. Both have parameters which are a bit like some subs, with Q around 0.38 to 0.4; they should work OK in sealed boxes, but if you have the room for a larger ported box tuned low, then some fairly prodigous deep bass is possible. Depends on your goals and available space.

The 8's actually make more sense for a Watt puppy sort of thing, but an "optimum tuning", (IMO), would be an alignment which is similar to the M8ta, in that there's a gradual slow downtilt from 100 Hz to ~25 Hz, overall response being down ~ 5 db at 24 Hz, then starting to roll more quickly after that. For the RS225-8, that would be a 120 liter net box for two drivers, tuned with a 3" flared port to 22 Hz. Max output per cabinet at 1 meter, before room gain, is just under 104 dB down to 21 Hz. It would be a rather deep box to have that volume. A smaller box could be used, but of course the output/sensitivity below 40 Hz would suffer.

The 10's parameters would seem to require a rather large box if you go ported; think 160 liters net. That's the size of the AS-15 subwoofer. Not surprsing, literally; it's a Hoffman's iron law thing, for the given cone mass and efficiency, it's inescapable. But a similar tuning at 22 Hz is possible, which should result in very nice in room response without a sub. Maximum anechoic output from each cabinet at 1 meter ~106 dB down to 21 Hz- WITHOUT room gain. This requires a 4" port minimum (21 cm long), though 6" would be better. This size sounds more like a bigger Dunlavy, doesn't it?

The 10's could work pretty well in a sealed box with a Q of 0.5 to 0.566 (Bessel). This would be for a well out away from the walls, so that there's a good bit of difference in the room gain at 60 Hz versus 30 hz. But maximum power output is much less below 50 Hz, falling to 100 dB at 30 Hz, and about 92 dB @ 20 Hz per cabinet.


If you're interested, let me know, and I'll post the plots from Unibox.

~Jon

[Steve Goff]

Thanks so much, Jon. I guesss I'll have to think about all this. I'm curious, though: would the RS-225-8 work better in your estimation because it has a better-behaved high end? I noticed that from PE's graphs the RS270 has a pronounced impedance glitch and breakup at about 1.3K.

[JonMarsh]

My best estimate right now (since I haven't got the 10's in yet- due in a few days) is that the 8" would be a bit easier to work with; the 10 is very smooth to 1 kHz, but as you note, you'd want to have the 1.3 kHz area well down in level.

If one were to do a "Sophia" clone, instead of Watt Puppy, then just one of the ten's per cabinet, and much smaller cabinet, could work. But for efficiency and having a litttle sensitivity available to lose in the crossover insertion loss, dual 8's, though bigger, might be the best way to go.

One other point about the crossover- in practice, just a cap for the midwoofer high pass tends to not be practical because of the LF impedance. What you'll need is an LCR zobel to equalize the impedance of the midwoofer in the upper module, then the cap can be chosen for the desired effect. This is inevitable, especially if you're shooting for the asymmetric 18 dB HP/ 6 dB LP, because the midwoofer enclosure should be fairly small to tune the box rolloff to something close to a Q of 0.707 2nd order HP. So, inherently, the LF resonance will be interacting with the zero from the feed cap, unless you kill the impedance variation. Still, it doesn't need to be a very expensive coil, becuase you have an R budge all the way up to the nominal Z of the driver. Caps in the zobel can be bipolar electrolytic, or for stability, I'd recommend the Dayton metallized film; fairly inexpensive. HP cap I'd consider using at least Solen or Madisound GE's, if still available.

`Jon

[Brian Bunge]

Jon,

Please do post those Unibox plots!

[JonMarsh]

Here are the main ones





M8ta enclosure with M8a





M8ta Enclosure with RS-225-8




Dual RS225-8 for 120 liter box




Dual RS270 for 160 liter box

[JonMarsh]

More Dayton "collectibles" - RS-180

For those of you who like pictures of the Dayton "collectibles" Reference series of drivers, please refer to these photo's of the RS-180, 7" mid woofer.


Yeah, I know. How do you tell it from the RS225 8" drivers, without a ruler?

Why, because the Xmax is only 6 mm instead of 7mm! Trick question, I know. They're pretty cute, but they don't have a lot of room behind the basket for the rear wave. Hmmmmmm. Might need a little extra relief behind the baffle.










~Jon

[Brian Bunge]

Jon,

I've been meaning to ask this question for quite some time but keep forgetting to do so. How do you derive the values of Qa, Ql, and Qp that you use in your simulations and what do the various values mean to the resultant response curve? I never fool with them and just leave them to whatever the default settings are.

Thanks!

[Hank]

Brian, looks like you're getting into the gory details, or should I say A.R. areas. I can't answer, but all three denote the system Q at Fb. Qa is Q due to absorption (absorption by what - the cabinet and dampening materials?); Ql is Q due to leakage losses; and Qp is Q due to port losses (do you wanna measure your port's viscosity?).
I know it's no help, but it makes me feel good to throw around some terms after a hard day of responsibility and a L O N G meeting.:Z
Stay tuned for the correct answers from the Poohbahs. :amen:

[JonMarsh]

Well, I'd have to say Hank is doing just fine with Poobah-hood, also!

No need to add anything, really. I sometimes do a quick check with Q degraded, just to see if the performance suffers much; but since I normally use heavy lining and some stuffing behind the driver, Qa is typically on the lower side, anyway. With a sufficiently large port, and good cabinet construction, the others don't have much impact in the real world- or so I've found, comparing predicted and measured response.

Well, it looks like I'm not going to Singapore in November (praise be for small blessings), not becuase the folks in Singapore don't want me there, but because our upper management in Europe has kicked off a new cost cutting program, called, what else, "Smart Savings". Of course, as I see it implemented so far, it's looking a bit more like penny wise, pound foolish, as it's going to delay developoment activities for new products, as well as hiring for existing critical reqs (all open reqs are now on hold, and have to go back to major division heads/board memebers in Europe to be reviewed and approved again. Given how much they kicked and screamed before, this seems kind of pointless to moi, just delays things. So now they're trying to talk one of our guys who was retiring end of Decmeber into stayin on a few more months, because otherwise they won't have bodies. And the two reqs in Engineering in Singapore for my group are now on hold, as well as my travel back there. I guess customer support and time to market aren't really very important. Oh yeah, there were those problems with the customer satisfaction survey this year, which are supposedly going to be a high priority for our US Pres this new fiscal year.

"Smart Savings"? Doesn't look like it.... Not from down on the ground level. BTW, now replacement PCs or any other IT purhcase have be approved all the way back to the European headquarters. If it weren't so sad some levels, I'd be :rofl:

And some of the folks from headquartesr wonder why I use my own laptop at work, and my company one sits on a desk for when I need email from at home.

/Rant.

[Hank]

Jon, Bro, I with ya. Big corporate intelligence is indeed in many ways, an oxymoron. Hang in there and make every effort to enjoy the holidays, family and friends. Remember, after we leave the corporate world, we'll be forgotten almost instantly.

[JonMarsh]

Yup. That's why I'm looking forward to some time at ThomasW's 2nd week next month, and I have the 3rd week of December scheduled off, too.


On topic, the 10" Dayton's just shipped, went off backorder, though the web site never showed they were out of stock. I ordered two more, so I have enough to test for one panel of the Saint-Saens.


~Jon

[JonMarsh]

RS225 Measurements

Well, after having to mess around with some cable problems, and fighting the %&@%@# binding posts on the new Palladiums (that CE stuff, designed to prevent idiots from shorting things out, makes it impossible to use many spade connectors, such as WBT), I got some basic meausrements done on my new RS225s, inlcuding in the M8ta enclosures.


First, let's look at the free air impedance.



This plots a little bigger than I would normally do, just so you can see the glitch at ~1.6 kHz fairly clearly.





Here, in the enclosure, is the impedance curve; note the difference in scale, so the 1.6 kHz glitch amplitude, though reduced, is still evident.

The LF tuning for the port enclosure combo is quite as expected, with an impedance null at 22-23 Hz, the center of the port tuning.

Now, next step is to look at the VERY near field response, hunting for snarks as it is, in the cone behavior. Mark K and I have both seeen irregularities in very nearfield measurements which are somewhat smoothed out (masked) in one meter measurements, but which in our opinion show problematic behavior. Don't ignore the clues, I say...

This is a near field (1") MLS measurement...



See that sharp dip at 1.5 kHz? That coincides pretty well with the impedance glitch. It also is very, very similar to Mark K's measured results. We'd hoped that the published PE curves were the results of an improved cone, but that doesn't seem to be the case.

Here's a more conventional 1 meter measurement; since it's not on an IEC baffle, it shows the characteristic drop between 800 Hz and 200 Hz. This is why you need baffle step compensation.



Note how the 1 meter resonse is smoothed by contributions from the total cone output- but this doesn't tell the story, with regards to that first cone mode and dip at 1.5 kHz. The dip at 200 Hz is due to adjacent room boundary for where the speaker is located, and using a relatively lont time gate.


Based on these results, I thought some detailed swept sine measurements nearfield would be a good idea, as that will have better resolutionn than MLS.

Here's the swept gated sine nearfield to the driver, from 10 Hz to 2 kHz:




This shows the dip quite clearly at 1.5 kHz, as well as the relative cone motion null at ~22 Hz, from the port tuning.



Just for fun, I also measured on the floor near the port exit from the cabinet.




Various bits and pieces in my living room were shaking and rattling during these tests from the gated sine measurement, between about 18 Hz and 35 Hz; for a single small LF driver, there was a lot of clean low frequency content- certainly the deepest I've heard from an 8" woofer! The response above 100 Hz is a combination of port output and reflected sound in the room from the driver; it's hard to do this test and get a clean output of just the port, and the HF port and room respose does a lot of comb filtering.


Conclusions

LF box tuning is right on the money.

Mark K's original meaurements were correct and still valid for production RS225.

Highest crossover frequency which I think I would use with the driver is 1 kHz, with my 8th order equivalent Cauer-elliptical. In my mind, that leaves the Hales Transcendence tweeter (pretty flat down to 550 Hz) or the Millenium Excel (which most, but not all, published plots show roughly flat to 1 kHz and a very slow roll off below that until 500 Hz) as the possible candidates to mate with it.

Since the current cabinets are cut out for the larger tweeters, and either woofer fits, and I'm setup for external crossovers, may as well try making this work, and see what happens, eh?


~Jon

[Steve Goff]

Too bad about the cone mode at 1.5K, Jon. Maybe the RS180S will be better for a two-way, with the RS225s working better in a three way.