Arvo, Orion, Phoenix.... ???

[intelonetwo]

Hi All,
I am about to embark on this IB design using the following drivers:
Vifa XT25 tweeter
HiVi M8a mid-range
Dayton 15" IB woofer or Stryke AV15
Question? Does, anyone know how the Dayton 15" IB or Stryke woofer sounds?




MI-II-CENTS
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The TailWind Generation I

[ThomasW]

ThomasT

Do you really mean IB= infinite baffle?, or are you going to build a dipole?

Given it's construction materials the Dayton IB woofer will have a sonic signature similar to Tempest/Shiva/ DVC-12/15/etc.

I haven't heard the new Stryke drivers, but older the HE-15 alu cone sounds quite good




theAudioWorx
Klone-Audio

[sfdoddsy]

Thomas doing a dipole along the lines of mine and the Arvo Part.

My question with the Dayton would be about air noises, given some of SLs findings about the Shiva on his site.

Steve




Steve's DIY Dipoles

[intelonetwo]

Thanks Thomas and Steve.

I like the PE subwoofer mostly because I dont have the money for four 12" woofers, and my theory is that having two 15" subwoofers from Parts Express would equal or exceed the amount of bass in a room. Is this correct?

ThomasW:::
I would like to in the future two 12" woofers per side wired out of phase using a physical dipole woofer arrangement which would provide more benefits I believe than the straight mounting arrangement of one 15" woofer.

My question is, would using the 15" give enough output and integrate correctly with the HiVi M8a to be used as a full range speaker in a Music based system?

Thomas




MI-II-CENTS
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The TailWind Generation I

[JonMarsh]

Integration of the system depends on a lot of factors. If you're using all active crossovers, or at least active crossovers for the low bass to midwoofer/midrange driver, then it's easy to make up efficiency and level differences which arise from both the interaction with the specific dipole baffle you're using (for the midwoofer, and for the low woofer), as well as the specific driver characteristics.

If you want to go passive, such as the "Arvo Part" project, then it's a lot tougher, and reuqires some bona fide engineering in terms of understanding the driver and baffle response and levels, and selecting the best driver set and configuration to reach your goals. Note, for example, that in the "Arvo" the 8's are wired in series, the 10" Titanic 2's in series- were the Titanic's 8 ohm drivers, (instead of the 4 ohm parts they are) they'd be wired in parallel. The M8a's are in series because this is necessary to help match up the level's, and to support the passive EQ and resulting network impedance. It will still look close to an 8 ohm load at many frequencies- if they were wired in parallel, it would look close to a 2-3 ohm load, and be too sensitive to match up with the woofers. Perhaps this sounds like an undue amount of juggling and matching of parameters between the drivers, but ponder that a simple in room response of the woofer and midwoofer combined - without crossovers or EQ produces this response (long window measurement time- includes the affects of early reflections, etc, with NO smoothing) The important part is what's going on below 1.5 kHz. To get this response in a two way dipole section PRIOR to the application of EQ or a crossover makes the crossover work MUCH easier. What it represents is seeking acoustical solutions to acoustical problems- something I'm rather in favor of, as opposed to tons of outboard electronics. (hey, someone's gotta be the conservative curmudgeon on the forum!






Now,

It seems from your description you're talking about using a single M8a midwoofer on each side. This will keep about the same sensitivity (re to input voltage) but will cut the power handling. Since the 8's pasband before rolll off is down to 200 Hz or so, excursion is something of a factor, since the actual electrical roll off will only be about 6-12 dB/octave- still plenty of excursion at 50-100 Hz.

Now, to compare two 12's to a single 15 can be done on a couple of different levels. One is simple swept volume- i.e., Sd times Xmax.

The DPL 12 has a cone swept area of about 506 cm2, and the Xmax is 14 mm. It's very well designed to minimize air noise for low frequencies in a dipole system- very important if you want to reproduce bass below 100 Hz cleanly.

The Dayton IB 15" driver has a Q well suited to dipole applications, probably more so than for an IB sub, as it's about 0.65 Qts at resonance of 20 Hz fs. I prefer something closer to 0.5 to 0.573 for system Q. This "Q" correlates well with what is subjectively called "fast bass". Yeah, there's no such thing as fast bass, but there is critically damped transient reponse- this is determined by the Q. The Sd is a little over 800 cm2, so it's not quite twice that of a DPL12. However, it's pretty close. It would require a larger baffle- that won't necessarily hurt anything, may help, since you'd probably want to consider a folded baffle anyway to extend the start of the dipole cancellation. The frame design is NOT optimized for a dipole application, and I'd have some concerns about it- since your concern here is cost, it would be a shame to buy these and then figure out they didn't really quite cut it.

Once you've decided what baffle configuration you want to use, you need to measure the repsonse on the baffle- at some frequency the response will be close to an IB or sealed box response, but it will drop off as you go lower, at about 6 dB/octave. If you crossover at 200 Hz approximately, then you want some baffle compensation. Becuase of the voice coil inductance, there's already some roll off above 70 Hz. This may help out substantially, but since is this a nominal 8 ohm driver, and it's nominal sensitivty at 200 Hz relative to 2.83 VRMS is at least a couple of dB lower than the 10" driver, (it's 4 ohm, but two are used in series- which doubles the impedance and keeps the same net output level due to the additional radiation resistance) you may have a bit of difficultly trying to engineer a passive crossover. Active, you shouldn't have any level matching problems.


Even the Dayton Titanic series has a frame design much closer to the needs of dipole woofers- that's part of why I ended up selecting the Titanic MkII "10" for my not quite full range dipole system. It has a number of other attractive features, such as weaving the voice coil leads into the spider, to prevent slap on the cone with high excursion. Since it's really an 11" driver, the Sd is 340 cm2, not quite half of a typical 15. But then I plan to cross these over at about 75 Hz to a low bass system.

So, yes, I think the Dayton IB driver has the output capability, but I'm concerned about other characteristics that make it not as desirable. In the long run, it may be better to save up a little more and go with a driver configuration that you'll be happier with for the long haul. There's no reason a well executed DIY speaker or amp won't be in regular usage 10 years or more after it's construction, so I recommend planning and researching carefully.

To borrow from the old saying, research and plan 4 times, measure twice, cut once.


Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[intelonetwo]

Thanks Jon,
I plan on using the dbxDriverack PA Eq, like jdobbs. This I understand will provide all the necessary crossover functions in the simplest manner possible, considering my limited construction space and expertise (with building crossovers).

I have been looking at the Adire DPL12 quite closely, however 4 drivers is a cost prohibitive $600. Do you have an angle on some at a lower price? LOL.

My goal here is to design and buiild a pair of Full-Range towers that do not have to make excuses for their performance in light of any other speakers. In other words, I want to build a butt-kicking speaker.

How much amplification do think will be necessary to driver 4 of the DPL12 woofers to full excursion?




MI-II-CENTS
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The TailWind Generation I

[sfdoddsy]

To finish off my dipoles, and for aesthetic reasons, I am considering a bit of a redesign, to something like this:




And from the side:



The DPL12s would be replaced by a single Stryke AV15, and the speaker would be a four way with 2 x Focal 10L6411, 1 x Seas W22 and the Seas Millenium, crossovers at 80, 320, 1440.

The top panel and bass would be able to be aligned separately from each other. In fact, the top panel would be removeable to sit as a separate tower. The front baffle would be in two pieces so that the mid and tweeter section could be flipped to have the tweeter on top or not depending upon where the acoustic center needed to be.

Finish would be gloss black for the sub section, and aluminium side rails and rubber (mmm) clad baffle for the main panel.

Any thoughts on my current madness?

Steve




Steve's DIY Dipoles

[Tim]

Steve, I like the flexibility of your new dipole concept. I have some DPL12's and I'm still trying to decide how I want to use them.
I was originally thinking about an Arvo Part MkI with the Adire drivers rather than the Daytons. However, after reading about Jon's ideas for the MkII Arvo I started thinking about a short line array of planar magnetic drivers. My idea was to use a Magnepan MMG mounted on top of a subwoofer using the DPL12s. A used pair of MMGs would be less expensive than a line array of BG8s, wouldn't require additional tweeters, and would have better resale value if it didn't work out. If midbass drivers were required for adequate output in the transition region the project would become excessively wide. I'm wondering if anyone has ever seen the inside of an MMG and can comment on whether if would be feasible to remount the component drivers on a new baffle with a short line of 6 MCM carbon fiber woofers or 4 M8a's?

[sfdoddsy]

I haven't seen inside a pair of MMGs, but the Maggie I would choose to mate with a sub would be the MG10QR, like this one:

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=3001451255&category=14993

I used to have a pair and they sound good, and were designed to be used with a sub.

Steve




Steve's DIY Dipoles

[sfdoddsy]

I've ordered the aluminium side panels to finish of the test baffles, so they should look something like this:



Steve




Steve's DIY Dipoles

[intelonetwo]

The speakers look great Steve, cant wait to see the finished product. Are you still using the Stryke 15 for the bottom two woofers?

Is the bottom unit an H-Frame design? Are you using 4 per side or 2 per side in this arrangement?




MI-II-CENTS
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The TailWind Generation I

[sfdoddsy]

It's the same driver complement as the current baffles, ie Adire DPL12s, but painted black and with the side panels.

Steve




Steve's DIY Dipoles

[intelonetwo]

So you scraping the Stryke AV15 idea and going with the DPL12? Is there any particular advantage to using the DPL12 over the Stryke AV15, other than the DPL12 allow you to run the woofers in a physically push-pull arrangement?




MI-II-CENTS
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The TailWind Generation I

[sfdoddsy]

Not scrapping the idea, I'll just finish off the current ones first, since the carcass is done. According to the dipole bass noise chart at Linkwitz, a single AV15 should give 3dB greater volume than a pair of DPL12s at 25Hz.

I may pick up a couple next time I'm in the States, assuming they ever ship.



Steve




Steve's DIY Dipoles

[sfdoddsy]

This is the final test baffle:






Steve's DIY Dipoles

[JonMarsh]

Pretty cool looking, Steve!

Too bad you're a little far away to just drop by for a listen! Though ThomasW and I have always thought it would be cool someday to visit the land of Oz.

-Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Jack Gilvey]

Nice, Steve...funny how your "test" projects look much better than my "finished" ones. Looking forward to more impressions.

[sfdoddsy]

Trust me, they don't look quite as flash up close. And screwing four precut bits of wood together isn't quite furniture grade, but they are coming along.



Steve




Steve's DIY Dipoles

[Hank]

Steve, lookin' good! I look forward to reading about your final design and listening results.

[sfdoddsy]

I now have a proper website with more info than you'd ever want on my speakers plus some other stuff.

And since Jon has named his speakers, I thought mine needed a name as well.

So I shall now refer to them as... Bob.


Cheers

Steve




Steve's DIY Dipoles

[Dennis H]

HAR! "Bob's Butt." Hilarious. Well done, Steve. :LOL:

[JonMarsh]

Cool Site, Steve! 8) 8) 8) 8) 8)


Yup, that's a "Five Cool" rating!

It's impressive to see so much DIY productivity PLUS putting the site together. I'll just have to hang my head for now, but then that gives me the opportunity to stage a comeback.


Seriously, nice work. I like the dramatic shots, too! :W


Best regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[Hank]

Steve: excellent site and I like your humor. You could be a Texan!
What About Bob? Bob is cool and must sound quite good.

I've gone through the Yellow Pages, but cannot find a "rubber emporium", but I'm intrigued and will continue my search for cabinet rubber

[PMazz]

cannot find a "rubber emporium"

C'mon Hank, just go to a pharmacy. Act like an adult, for gosh sake.

Pete

[sfdoddsy]

I have an International Directory of Rubber Emporiums, I'll try to find the nearest one for you.






Steve's DIY Dipoles

[sfdoddsy]

Ah, here we go Hank. An Austin Rubber Emporium:

Austin Rubber Emporium

And just to get this on topic, here's a shot of my new center speaker. The drivers aren't right, but will be. It already sounds very good.



Cheers
Steve
:twisted:




Steve's DIY Dipoles

[PMazz]

Shouldn't that be more like "Leather Emporium"!

Pete

[sfdoddsy]

I'm sure they cater to all tastes in coverings.






Steve's DIY Dipoles

[Hank]

I wonder if Steve's rubber fetish can be linked to the fact that toilet flushes rotate backward *down under*. Hmmm...

Anyway, keep going Steve.

[sfdoddsy]

Well, in between blowing up a woofer I whipped up a test baffle for a four way. By the time i add separate subs it may be more trouble than it is worth.

What think you all?






Steve's DIY Dipoles

[Hank]

Frankly, Steve, I think they look very nice. If you do dipole subs, you will definitely be taking up some floor space with your system. If you don't have the WAF problem, then go for it!

[SamL]

Hi Steve,

Are you using active or passive crossover for your 2 way center channel?
Bec of space and location, I am thinking of using dipole for my center and wonder if Vifa M21W0-39-08 can do the job?
Do I still need to add BSC onto the crossover if going dipole?

Thanks,
Sam

[sfdoddsy]

Well, I have a Behringer DCX2496 digital crossover on order for the center and surrounds.

But to tell you the terrible truth, I'm not using any crossover at all at the moment. ops:

I have the preout split two ways with one running directly to the tweeter and the other for the woofer into a Behringer 602 mixer. This has an EQ band at 80Hz which I use to boost the bass, and two more bands at 2500 and 5000 which I have all the way down.

I wouldn't risk the Seas tweeter like this, but I'm just using a Focal TC90 and Seas L21. It sounds darn good and bass goes surprisingly deep. Makes one wonder how much of the dipole charm is the nature of the beast and how much the drivers chosen.

Apparently, due to the rear wave, baffle step is not needed. And I don't see why you couldn't use the Vifa driver if your tweeter allows a low enough crossover.

You could probably also use a passive crossover if you can find a way to actively boost the bass for dipole effect. I wouldn't necessarily recommend the Behringer mixer, but it kind of works.



Steve




Steve's DIY Dipoles

[Dennis H]

Sam, SL designed something similar to what you are describing. "The design is a 2-way loudspeaker with a passive crossover between a Vifa P21WO-20-08 woofer and a Vifa D26TG-35-06 soft dome tweeter."

http://linkwitzlab.com/proto.htm#PMT1

[SamL]

Excellent! :P

The SL's PMT1 and PMTM1 is what I am looking for - thanks.
I still keen on Vifa M21WO-39-08 as it got 6mm xmax compare to 4mm of P21.
I qot 2 questions. Is the back spine really necessary? Can I hang the speaker on the wall - what if with additional 1 - 2" at the back?


Thanks,
Sam

[sfdoddsy]

If you mean hanging on the wall with the back up against the wall, I think that would be a bad idea. Dipoles need space behind them.

Steve




Steve's DIY Dipoles

[SamL]

You are right. The radiation will change from 4pi to 2pi.
Um... back to drawing board.

Thanks,
Sam

[sfdoddsy]

Well, after some pondering about space and practicality, I decided it might just be easier to steal SLs aesthetic designs as well as his acoustic ones.



The final finish would be black all over.

Steve




Steve's DIY Dipoles

[JonMarsh]

Looks pretty interesting Steve- so these are your newest prototypes, a "hybrid" combination of Phoenix and Orion? Could/should work pretty well- do you have a pair working in this fashion yet, or is this just a "proof of concept"? (territory I'm well familiar with...)

I'm hoping to finish up my klones in the next couple of months (veneering will take the longest time, I expect), then it's back to the Arvo. Planning on making a tweeter change, but other than that, the initial measurements were quite promising. All passive crossover, then probably a single stage NFB equalizer for the bass below 70 Hz. Balanced and unbalanced inputs and outputs (the NFB gain block is inherently a balanced differential circuit).

Let us know how you like the sound of your hybrids...

~Jon

Regards,

Jon




Earth First!
_______________________________
We'll screw up the other planets later....

[sfdoddsy]

Yep, they are up and running and sounding rather tasty. I recently changed some of my EQ settings to those closer to SLs since I have the more powerful Driverack 260 now.

This is the room response at the seating position, 1/24 octave:



The only additional tweak I'm thinking of is flattening the rise at 5kHz which I've been told is endemic to the Millenium, although it doesn't appear on the official measurements.

Steve




Steve's DIY Dipoles

[Hank]

Steve, those are going to look very nice. I've not heard such dipoles and really want to experience the *different* sound they make. How much woofage boost will you need for you listening room?

[sfdoddsy]

The total amount of boost isn't easy to work out.

I boost at 6dB an octave from 300 down to 20Hz which is 24dB.

Against this, there is a -6dB low shelf cut centered on 150Hz to balance the bass boost of floor radiation to the open radiation of the mids. Then the overall bass level is cut by about another 6dB.

So I guess the maximum boost is around 12 dB at 20Hz.

This measures flat and sounds it, although I sometimes think there is a tiny bit too much bass on a few records.

Cheers

Steve




Steve's DIY Dipoles

[Dennis H]

The only additional tweak I'm thinking of is flattening the rise at 5kHz which I've been told is endemic to the Millenium, although it doesn't appear on the official measurements.

Could be. Or I wonder if it might just be baffle effects? Did you see Dennis Murphy's tests of a 3/4" roundover on one of his small cabinets? It smoothed out some HF ripples. I know SL isn't big on offsetting drivers and rounding edges but it does seem to improve HF response both on and off axis. Maybe you could find some attractive thick felt or foam at your local rubber emporium. :LOL:

http://murphyblaster.com/content.php?f=cabinets.html

[sfdoddsy]

Now all in black



8x)




Steve's DIY Dipoles

[sfdoddsy]

And that's it. I've decided I've finished. No more test baffles unless I decide to have some side panels made professionally, although there may still be a bit of audio tweaking.

Thanks everyone for all their help and advice.

Photos of the final speakers and the new centers and surrounds are here:

http://www.doddsy.net/steve6_014.htm

Cheers

Steve




Steve's DIY Dipoles