Low distortion tweeter for MTM

[Zvu]

Hi guys,

Inspired by few projects on this forum i started to think about something that would be the ultimate loudspeaker project for me. Project like that should have flat frequency response, good CSD, lowest distortion possible and possibility to be listened in smaller or larger rooms (by european standards small is anything from 12-16sqm, and everything from 20sqm to about 40sqm is on the larger side). I started searching for midranges and few solutions immediately popped out but i decided on Tang Band W4-1337SDF. You'll notice that it has F on the end which means that it uses ferrite magnet instead of Nd. I decided on Fe version because it measures somewhat better regarding distortion profile from its Nd sibling. Measurements attached.



Since it has break-up at 13.5KHz, it is quite usable up to 4.5KHz where HD3 peak can be seen, but even at 95dB HD3 is only slightly above 0.5%. Intention is to make xover point between 3.5-4KHz with the tweeter. Down low it can be used to about 250Hz but i intend to cross it somewhere between 300-400Hz. For woofers i'm still deciding between 2xRS180 or 2xRS225 per speaker - i'm leaning to RS225 but i still have to find some decent distortion measurements for RS180 to be able to write it off.

Image not available

So, one midrange looks good, two are better. Higher sensitivity, lower distortion - high end midrange for reasonable amount of money... Only drawback being vertical directivity when used in D'Appolito, as i intend to use them. But, as i mentioned earlier, i would like to be able to listen to them from smaller distances (about 2-2.5m) and that's where i think i have a problem.

I have to put the mid centers as close to tweeter as possible to get better vertical dispersion. I've been watching Nd tweeters but they either have high distortion at >90dB, or ragged frequency response or they are adequate but insanely expensive.

I ordered at ebay sixpack of TB W4-1337SDF from guy from Indiana (4 for me, 2 for my friend), and i can get RS180 and RS225 in europe (RS180 costs 54$ and RS225 costs 75$ a piece - much more expensive than in US but still way cheaper than Seas or Scan Speak equivalent).

I need a tip for tweeter that has: good distortion profile to at least 95dB, flat frequency response, good CSD plot, with small radius and not too expensive.

Piece of cake, huh ?

Much obliged.

[JonMarsh]

You know the old saying.... pick any two of three, and it's doable. All three, likely another matter... particularly the low cost.

[Face]

SB Acoustic has a few smallish face plate tweeters that may fit the bill.

[JonMarsh]

Don't forget CTC considerations in choosing your crossover frequency. You'll have more latitude in that though, if you use a phase quadrature 2rd order crossover, but still, it shouldn't be forgotten.

Scanspeak has some nice small form factor tweeters, but inexpensive they aren't. I agree with Face that SB might be someone to check out.

[Zvu]

I'm very grateful for your suggestions and advices.

I have looked at SB26STCN-C000-4 and it rises distortion over 90dB. SB29RDCN is a good one and at a decent price but it is a ring radiator. I have at this moment two way using SB17NRXC35-8/SB29RDC-C0004 and it sounds spectacular but tweeter off axis behavior dictates rising response on axis. Since power response of this speaker should be rock solid all the way to mid/high xover point, i would like to use dome because of off-axis behavior that suits this loudspeaker better than ring radiator.

As for xover, i intend to try BW3 and LR4 as suggested by D'Appolito for MTM and then i'll see what works the best for me. I'll make a test cabinet to measure and try different xovers and driver spacings but i'm inclined to believe that closer they are, the better vertical dispersion it is. I will measure it and see if i'm right or wrong.

Regarding tweeters, i'm not hunting for anything dirt cheap (though i might buy and measure ND20FB-4 just for the heck of it) but i will try not to give 250-300$ for a pair of tweeters. Tang Band has lots of good lookin' Nd tweeters but i can't seem to find reliable measurements for them.

At the moment, i'm reading tweeter tests done by Evil Twin. Maybe i find something new. In the meantime, i'm quite impressed by performance of Seas 19TAF/D and Seas 27TDC.

If i don't find small tweeter that suits me i can always buy Seas TDC and route the part of its front plate. Mids are going to be mounted on aluminium plate with tweeter, and that will be mounted into the routed opening on the front of the loudspeaker cabinet - something like THIS. But milling through tweeter front plate is no elegant solution so i'll keep looking for a while.

cheers

[JonMarsh]

Going with a larger format tweeter will open up your choices and options substantially- hugely, in fact. Too bad you can't consider $300 a pair, because there are number of Transducer Labs N26 variants in that price range which have stellar distortion performance not just for that price, but for any price.

[Zvu]

For 220$ i get small format Scan Speak D2004-602000. Looks pretty good:

http://www.audiocomponents.nl/download/scan-speak/D2004-602000%20-%20Hobby%20HiFi%202011-1.pdf

HD2 falls under 1% after 2KHz, and HD3 is nonexistent.

[5th element]

The metal domed SB standard line is pretty darned good.

http://www.audiogurman.com/1.htm#sb26adc

[Zvu]

I hear you 5. I've been watching them for quite a while. I like not seeing metal dome resonance and distortion performance is stellar but i would like to find something like that with smaller face plate.

Main concern of mine is vertical lobbing and i want to put the nulls as far off-axis as i can. If i use normal tweeter, CTC is bigger and i'm kinda set on xover point - not lower than 3KHz. Objective is to make something similar to Snell Illusion but that can work in smaller or larger rooms.

[Face]

A 3k crossover seems almost wasteful nowadays...unless dealing with ribbons.

[Zvu]

Agreed, but searching for tweeter that has flat frequency responce, low distortion, good csd (to at least -40dB), small faceplate and moderate price is hard enough without adding low Fs and low distortion at say 2-2.5KHz to the list.

It would be kinda pushing it

[Zvu]

TangBand 28-847SD looks quite good but off axis is obviously it's weak point. I would like to see detailed distortion plot though - at least HD2 and HD3. Vifa NE25VTC-04 is much better performer in that regard but worst at everything else.

[Face]

SB26STCN-C000-4

http://www.audioexcite.com/?page_id=4084

Only $33. https://www.madisoundspeakerstore.co...weeter-4-ohms/

[5th element]

I would look at tymphany's website and see if anything there looks suitable.

3kHz isn't very low and most neo domes can do that without a problem.

They've got quite a selection of what looks like cheap and very small format tweeters. Couldn't tell you about the performance but it seems like they are bringing back the D26NC which would be perfect.

[bvbellomo]

If you can cross a little higher, I recommend the ND16FA. Very nice tweeter, if a little below your price class. Dayton has several other small neos that might be worth using, but I haven't used them.

[Zvu]

SB26STCN-C000-4

http://www.audioexcite.com/?page_id=4084

Only $33. https://www.madisoundspeakerstore.co...weeter-4-ohms/

Thanks for the link Face. I've seen Göran's measurements, they look good but measurements on this forum and Italian site (dibirama altervista) shows higher distortion than the ones Göran made.

http://www.dibirama.altervista.org/home-page/tweeter/326-sb-acoustics-sb26stcn-c000-4-tweeter-1-4-ohm-240-wmax.html

Other than that and off axis response they look good. So does Tang Band 28-847SD, which would be my primary choice because of good general performance.

[Zvu]

I would look at tymphany's website and see if anything there looks suitable.

3kHz isn't very low and most neo domes can do that without a problem.

They've got quite a selection of what looks like cheap and very small format tweeters. Couldn't tell you about the performance but it seems like they are bringing back the D26NC which would be perfect.

I checked Tymphany Peerless site for D26NC55 lookalike tweeters and none of them shows flat frequency response as the original Vifa did. If you have some info that they will revive D26NC55, that's another matter and would be a good news.

[Zvu]

If you can cross a little higher, I recommend the ND16FA. Very nice tweeter, if a little below your price class. Dayton has several other small neos that might be worth using, but I haven't used them.

Thanks for your suggestion. Zaph used ND20FB and i intend to buy and measure it and see if it suits me.

[jpvanson]

Agreed, but searching for tweeter that has flat frequency responce, low distortion, good csd (to at least -40dB), small faceplate and moderate price is hard enough without adding low Fs and low distortion at say 2-2.5KHz to the list.

It would be kinda pushing it

To add another option that's a bit off the beaten path, there's Stereo Integrity's M25 tweeter. It's intended as a higher end at a budget car audio tweeter, but, unusually, it has an XBL^2 motor that I think may give it some potential to fit your criteria.

As a fan of that particular approach to motor design (and being impressed by the quality of one of their early model 24" subs I have), I picked up a pair a few months back to play with as kind of a first post audio hiatus DIY project. Unfortunately, I haven't the gear and especially the knowledge yet to make the measurements needed to do a proper job of that just yet nor have I seen anyone make any proper measurements of this model yet either. So, that project has been shelved for a bit. Still, the XBL^2 motor has the potential to offer very good distortion performance, possibly better than others anywhere near this price point, as frequency decreases (provided the factory is assembling to spec). The Klippel shown is from a prototype that wasn't properly sealed in back hence the funky impedance curve near resonance. The production units are supposed to have fixed that, so it'd be interesting to see where that's at now, as well. (At this point, I'd send my pair out to someone who knows how to do it right just to see how they measure up.)

Just another to consider.

[Zvu]

Thanks for the tip.

I also found this - but nowhere to buy them:

http://www.acousticdev.com/cms/index.php?option=com_content&view=article&id=56:ceradome-tweeter&catid=38:uncategorized&Itemid=60

Looks a lot like TB: http://www.parts-express.com/pedocs/...ions-45762.pdf

[jpvanson]

Thanks for the tip.

I also found this - but nowhere to buy them:

http://www.acousticdev.com/cms/index.php?option=com_content&view=article&id=56:ceradome-tweeter&catid=38:uncategorized&Itemid=60

Looks a lot like TB: http://www.parts-express.com/pedocs/...ions-45762.pdf

Measurements I may lack, but my ears tend to perk up when I hear XBL^2, so I've a little knowledge here. From what I've gleaned, ADI's tweeter is an OEM design that requires a minimum order of 1000 units and not at a budget per unit price. So, it never came available to DIYers directly, so far as I've seen, and probably never will. However, a revision does seem to be used in Starke Sound's offerings. (The marketing jargon in the technical section of that site is cringingly bad, but, rest assured, LMF is basically an improvement by Wiggins on XBL^2 using a deeper notch in the split gap.) I suspect the smaller offerings use a variant of the ceramic dome while their flagship model uses beryllium. I've got to admit, while I find the speakers on the ugly side and hate the ridiculous technojargon, I would like to hear them. Not exactly available for DIY, but they are out there. (I see that they're offering a tweeter upgrade to owners of their lower tier products to the beryllium drivers. So, I suppose there might be a tiny, tiny chance to sweet talk them into selling a pair of traded in used tweeters, but the price is out of the budget you desire seeing how the upgrade is $450 to $1250 depending on condition of the returned drivers. [Ouch!])

As for the TangBands, they probably do use the same frame and phase plug. From what I've seen, using generic frames and soft parts tends more to be the rule than the exception as for most smaller driver design outfits, those targeting budget brackets or others just doing small runs or prototyping, it doesn't make sense to invest twenty thousand plus in tooling just to be cosmetically different from boutique brands when a generic offering suits the particular need. With XBL^2 drivers, the difference is in the magnetic gap of the motor and won't really show on the outside other than with a thicker top plate (hidden with a tweeter, typically). How they compare distortion wise is a matter for measurements. XBL^2 has potential to be really good there, but it's also particular about the alignment of the voice coil and how it interacts with the split gap. If the build house is good, then I'd wager the TangBand would have tough competition. If not, well, probably not.

In any case, these aren't the only XBL^2 tweeters out there. I know of one other: Kravchenko's KAXBLTWT. (Just rolls off the tongue, don't it?) Kravchenko makes pretty good drivers from what I've heard and, I believe, he's the driver source for the oddly named, but apparently rather nice Funk Audio speakers. (When I've lurked here over the years, I've sometimes wondered what kind of designs this group could come up with if they used a custom source like this to have drivers built specifically for a design rather than rely on what general purpose designs the bigger outfits decide to offer.) Unfortunately, those tweeters, though apparently they measure very well, fail to meet your needs of size, mountability (pretty much useless for use on a regular baffle), availability and, of course, cost by far.

There are others that may turn up from time to time on the used market, the CSS LDS25X, for example, but they don't come up for sale all that often. The distortion plots on page four here may at least give you an idea of what tweeters of this motor design are capable of, though. I bought the M25s to find out if they could do something similar if I can get past this equipment and competency hurdle of mine.

[5th element]

I checked Tymphany Peerless site for D26NC55 lookalike tweeters and none of them shows flat frequency response as the original Vifa did. If you have some info that they will revive D26NC55, that's another matter and would be a good news.

The D26NC55-06 is there on the website...Just without a picture.

[Zvu]

I assumed that they just didn't take it of their website but left it for reference because i can't find anywhere to buy them.

I guess it will be available through usual sources in a couple of months.

Thanks

[Zvu]

Has anyone had the chance to listen or measure LPG 26NA tweeter ?

http://www.madisound.com/store/manuals/26na.pdf

They are about 50$ a piece and looks like decent performer.