Project #2: Raptor MTM's (yet another RS180/TDFC MTM to choose from)

[Raptor550]

Hiya Folks!
Well a friend really liked my last speakers so he wants to buy em from me. He needed something semi-portable to use them to DJ house blues party's. Thats OK, I wanted to do a new project anyways! (internal voice: "FEED MY ADDICTION!") :B So I have my sights set on another Dayton/Seas combo, what can I say, I'm in Ohio so I am biased.

Anyways take a look at this crossover and tell me what you think (for those of you crazy gurus that can actually look at a schematic and actually know what its going to do)



This is an untested design, so we will see what happens. Its an incarnation of the "Raptor" MT's, the latest from Jay_WJ over on the DIYaudio forum. By now I should be his favorite guinea pig. This will be my build page.

[Dennis H]

Errrrr, well, since you asked, I predict this one will be 'too revealing' just like the last one. Three components aren't really enough to properly handle a 'difficult' driver like the RS180 when you include BSC, breakup suppression, etc.

[AJINFLA]

Good ole Cartoon...

[PoorboyMike]

Jay seems like a smart guy but he sure is arrogant for somebody who has never actually "built" a pair of speakers.

If it was my money, I would start with a proven design and go from there.

Eventually, I plan on getting a full measurement set up and attempting my own designs. When I do get to that point, I'll start out with a much more forgiving driver than an RS180. :T

[PoorboyMike]

Good ole Cartoon...

LOL! When I 1st looked at that I didn't really get it. After I posted I looked again and it hit me. Duhhh! :B

[fjhuerta]

I'm using a similar crossover on my 27TBFC tweeter,and I needed a conjugate in order to lower high frequency response (with in-baffle measurements). It was simply too much. The way I see it, that circuit is a direct copy of Zaph's bargain MTM, and I don't think it'll work well with different drivers (the RS180 instead of the Daytons Zaph is using), or a different baffle configuration.

[Raptor550]

it would be a shame to build a speaker that was 'too revealing'

I never got the arrogant vibe from Jay, he seems pretty helpful to me. Sometimes the internet is not so good about communicating stuff like voice inflection. If he IS arrogant I didn't notice's-that All I will say on that subject. But you do bring up a good point the RS180 is a fickle mistress not to be taken lightly. *read after BOM*

AJINFLA - i'm kinda slow so I'm not sure if I get your joke, that one thing I DO get is that crazy dog avatar! I laugh out loud half the time I come across any of your comments because of that bewildered pooch!

On to business:

Who got da' BOM!
* 027-440 Yes Dayton DMPC-30 30uF 250V Polypropylene .. $7.88 $15.76
* 027-534 Yes Solen 2.0uF 400V Polypropylene Capacito .. $1.96 $3.92
* 004-4.3 Yes Dayton DNR-4.3 4.3 Ohm 10W Non-Inductiv .. $1.38 $2.76
* 004-4.7 Yes Dayton DNR-4.7 4.7 Ohm 10W Non-Inductiv .. $1.38 $2.76
* 255-204 Yes Jantzen 0.13mH 18 AWG Air Core Inductor .. $2.88 $5.76
* 260-520 Yes Sonic Barrier 1/2" Acoustic Foam w/PSA .. $8.73 $17.46
* 260-530 Yes Sonic Barrier 3/4" 3-Layer Damping Mate .. $17.74 $17.74
* 295-364 Yes Dayton RS180S-8 7" Reference Series Shi .. $30.74 $122.96
* 027-206 Yes Dayton PMPC-0.47 0.47uF 250V Precision .. $1.31 $2.62
* 027-244 Yes Dayton PMPC-10 10uF 250V Precision Audi .. $6.04 $12.08
* 255-112 Yes Jantzen 3.3mH 15 AWG P-Core Inductor .. $10.24 $20.48

Subtotal: $224.30 w/o sonic barrier = $189.10
Madisound:
27TDC (H1149) Textile dome $64.10
1.0mH 15 AWG Steel Laminate $17.30

Sub-Total: $81.40

GRAND TOTAL: $305.70
w/o sonic barrier = $270.50

I keep flipping between this desighn and the Natalie Portmans, primarily because I am tight on cash (but having a sexy speaker name does hold some sway). Evil twins BOM's came out to $305 with the RS tweeter. Which makes me wonder if I could get down to $260 with a Seas NapP. I am going to the PS tent sale so I will save money the more parts I can get from PE. I have heard that you need to have test equipment to make sure your individual RS tweeter can go so low which I do not have. I know Thomas is pretty strict about the stickys, but couldn't I do a reverses like what Jon_W did to the Modula TM's?

On the subject of saving money, anybody look at those Janzen P cores? They are pretty cheap and claim to have "significantly lower hysteresis"

[Raptor550]

wow! the difference a decimal place makes! HAHA! the x overs will cost allot less because the inductor values are smaller. OY-vey I feel like a dummin'.

[Dennis H]

27TDC (H1149) Textile dome $64.10

I think the the 27TDFC (H1189) is a closer drop-in replacement for the 27TBFCG.

[dlneubec]

Raptor,

To put it succinctly, Jay had a very short and explosive history on this forum. What you may not get is that as far as anyone knows, he has not built any speaker, measured any speakers, and has only done crossover simulations, etc.

You are considering building and comparing his design to the work of folks here who have many, many years of accumulated knowlege and experience measuring, designing and building successful speakers. Designs have been created using that experience and have had lots of folks build and/or hear and positively reveiw the results.

There is a big difference between being able to run a simulation software and knowing how to design and implement a successful speaker. My suggestion is to give Jay a year or two and at least a couple of successful builds (ones that others have heard and independently judged successful at DIY meets) before you consider spending your hard earned money on building his designs.

Best Regards,

[cjd]

I would add, no insight into the process followed was given. Back when I was just getting started I did lots of sim data based modeling. I even built a whole bunch. And I found all SORTS of things I wasn't doing that I *HAD* to do for it to work properly. Sim data is only as good as your understanding of what's going on.

So, I can look at this network and have some idea of how it might contour response, but that will tell me nothing about how it will actually work. Or sound. Phase, I can't do in my head.

Also, while the TDFC and the TBFC tweeters are pretty much interchangeable, the TDC is not quite such IIRC.

C

[Raptor550]

Thanks Dan for your candidness, I respect that. Polititics aside I think i am leaning towards the Nat p's because they might not be as expensive as I thought they where. I'm putting together a natp BOM as we speak to compare.

TDFC and the TBFC tweeters are pretty much interchangeable,

I think me putting the tdc was a mistake on my part., What I was wondering about was what would one have to do to put a tbfc or tdfc in the place of the RS tweeter.

Right now I am looking to see if I can save some money by replacing ferrite's with jantzen P inductors

cjd, if you ever stop by Dayton I would love to pick your brain.

[Hdale85]

Well all I know is don't use solid core inductors. And isn't there a nat p variation that uses the seas tweet?

[JonMarsh]

On the subject of saving money, anybody look at those Janzen P cores? They are pretty cheap and claim to have "significantly lower hysteresis"

Lower hysteresis than what? air core coils have no hysteresis. But they need more turns of wire, and that means larger gauge wire to keep DCR in check. The P-Core inductors are powdered iron bobbins; actually they have higher hysteresis than a decent ferrite, but don't saturate as abruptly. I've seen these in Legacy Audio designs, and I've heard them saturate when driving the speaker (Legacy Whispers in this case, at the factory) near their limits. Loudspeaker cored inductors are generally not properly characterized or specified.

If you have to go that way to save money, try the C-Core. they're likely to have less distortion. Inductors with cores have inductance varation as a function of current, even if the core permeaibity is quite low. (which means larger core, and more wire turns).

~Jon

[cjd]

RS28 to Seas is a new network.

So, for giggles, I tossed the RS150 at this topology (with RS28A) using the data files I have handy for Ryan's project. I was able to get good integration with some tweaking - however, the breakup peaks were no more than -15dB. This doesn't really tell us anything new, however - the basic topology is sound. The key is whether it is properly implemented. Can't say that just looking at the network. Could go sim it all up, but that's more time than I feel like spending. If I remember maybe I'll throw the data files from the WWMTM project at this topology.

C

[JonMarsh]

My own experience is that a good level for the break up peaks is -45 to -50 dB. Or lower. That experience was developed from the original M8a project with HiVi 8" woofer, and applied to the Modula MTM, the Modula MT, and the NatalieP.

One of the things not quite right about the Thor design by Joseph D'Apollito, as that he uses a notch filter only to get the W18 reduced in level enough to follow an LR4 roll off; at the driver resonance, it's only down about -15 dB. The problem is that the driver is behaving in a non-pistonic manner, there is still energy storage going on, and the so called correction is only valid for the on axis measurement- other things can happen in other directions. Anyway, it doesn't sound good.

Easiest way to evaluate that is to listen to the midwoofer by itself with the tweeter disconnected; anything that sounds at all grungy or not like a low pass filter is driver crap getting through that will cause listening fatigue. Just looking at the summed response can be VERY misleading, as I'm sure CJD knows from experience.... :W

[Raptor550]

Forgive me for my newby questions, you guys are really helpful, I haven't been ably to find C-cores.
Looks like my choice is 18/ 20 gauge air-core or 15 gauge p-core. The 20 gauge still holds till 200 RMS which is quite a bit higher than the rs180 so 20 gauge should be OK? what would be the advantage of a larger gauge?
what does hysteresis sound like?

With the tweeter disconnected, would I use test tones to hear the grunge right? Or would it be more obvious then that?
----------------
I did a BOM for the natP's with strictly Parts express and it came out to $313
but since everything will be %20 off Saturday I should be able to have them for around $250 thats really steep for me but I would rather do things right "the first time" then keep inching my way up with iterations, its cheaper in the long run I guess.

looks like .2mh is out of stock!

[joecarrow]

I can't speak about the sonic effects of different inductors from first hand experience, but all the theory I know says that if it's not an air core, you're best off with as much headroom as possible. That's not good for the budget, though, so I guess I'd say that as long as the DC resistance is in line with what the design calls for, then go for it.

You want to hear the grunge? :twisted: Just hook up the woofer with any music and no crossover! I made that mistake after my first shipment of components showed up. I thought, "Gee, I wonder what this woofer everyone is so excited about sounds like!". I nearly sent it back, and I couldn't believe I was hearing the same woofer after I built the Modula MT crossover. Of course I know better, but I guess it's the kid in me wanting to touch the stove to see if it's really hot.

Good luck on your build- money was tight for me too when I did it, but I was glad I did. I also had to wait the better part of a year before I felt financially comfortable doing it, so I guess I'll just say that sometimes that's a good option too.

[cjd]

I always listen to drivers raw, no crossover. You learn a lot about them that way.

The absolute most important consideration with series inductors in a woofer network is matching impedances. (if you're looking at a series network, consider this true for ALL inductors).

Madisound often has equivalent components at better prices when it comes to stuff like inductors. Plus I like sharing my business.

C

[4thSeason]

Raptor I can't see the schematic but you may want to see if it looks like my crossover. You indeed are not the guinia pig for this I built one with the assistance of Jay and right now I have a thread going about this design. As of late I have been very busy but if you were considering it it would give you insight. And I concur that I have personally spoken to Jay on several occasions and he is very nice and indeed helpfull although I understand he had issues with people here that is not my buisness, that being said everyone else here is also in my opinion very knowledgable and helpful. Sorry I haven't updated my thread lately I have been so busy trying to hammer down a large realestate deal(25 units and a Pizza shop)

Bri