# 1st order xo for tweeters



## Jason Schultz (Jul 31, 2007)

does anyone have an opinion on disadvantages /advantages of crossing a mid to a tweeter using ist order xo. providing the drivers have adequate overlap and the tw is crossed high enough to prevent over excursion, and mid is low enough to prevent beaming. thanks


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## mgboy (Jan 17, 2007)

All I have to say is good luck finding drivers to work, then getting to them to work nicely with a true first order crossover.


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## jeremy7 (Feb 7, 2008)

I'm not sure what type of quality you're trying to achieve or whether your planning this for a two way or a three way. I have seen/heard good quality two way designs with a first order low pass on the woofer, but I'm not aware of any successful designs with a first order high pass on the tweeter. I personally would not use anything lower than a second order on a tweeter. My biggest reason for this is that I don't believe tweeters enjoy too much excursion, and if I'm not mistaken excursion quadruples every octave. In other words your tweeter increases excursion with decreasing frequency at a rate very close to 12db/octave, so a first order high pass will actually allow the tweeter to increase excursion below the crossover even though the volume is dropping 6bd/octave. This I believe can contribute to distortion.


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## Jason Schultz (Jul 31, 2007)

Thanks jeremy. It makes sense when you put it that way. It seems I will be using a 2nd
order xo now. This is for a three way system which i am slowly designing with the input of all you shacksters. Mid Drivers, two of them are the http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-818 Tang band drivers. crossing over to Dayton Tweeter :http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=275-070 at around 4k in a MTM arrangment. the woofer is an old 12 inch poly coated paper cone xo to mids at 300HZ. My aim is to keep the xo completely out of the mid range since i am a learner at building xo's.


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## looneybomber (Sep 20, 2006)

Jason Schultz said:


> Tang band drivers. crossing over to Dayton Tweeter at around 4k in a MTM arrangment.


Little things I forget are center to center spacing (from center of the mid to center of the mid) in MTM's if it's one full wave length or 1/2 wave length. Either way, 4khz is too high.

With those drivers, your CTC spacing is 8.5" if the driver frames are touching. If the XO is dictated by a full wave length, that puts your XO point at ~1600hz. ~3200hz for half wave length.


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## Jason Schultz (Jul 31, 2007)

I thought that with MTM's the fact that both mids have their acoustic centre half way between them that spacing is not a problem (obviously not too far apart ) ,but the only real problem would be the mid to tweeter spacing in a WMT design. I've switched my tweeter to a slighly smaller Vifa unit any way. Looney can you remember where you came across this info. It sounds like the rule for Mid to Tweeter spacing to me.


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## 1Michael (Nov 2, 2006)

The width of the baffle, center to center spacing and baffle step compensation are all Critical when designing the crossover.


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## looneybomber (Sep 20, 2006)

Jason Schultz said:


> Looney can you remember where you came across this info. It sounds like the rule for Mid to Tweeter spacing to me.


I'll look into this to see where I read this. For some reason, such simple information is always hard to find.


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## Jason Schultz (Jul 31, 2007)

That would be great if you found it but don't look to hard because I found out through Bill Fitzmaurice that it is more of an issue with centre channels because it leads to a much narrower dipersion pattern. With virtically arrayed drivers however it might be an advantage because there will be less reflections from the floor and ceiling due to a narrower virtical axis response. 
The tweeter i have is round with 104mm diam . I'm going to grind off sections top and bottom to make it narrower horizontally then mount it in a recessed area in a D'Apollito config. the C TO C spacing will still be about 8 inches apart.


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## Bill Fitzmaurice (Jun 14, 2008)

Jason Schultz said:


> I'm going to grind off sections top and bottom to make it narrower horizontally then mount it in a recessed area in a D'Apollito config. the C TO C spacing will still be about 8 inches apart.


Joe's 'Thor' has 12" CTC with a 2.5kHz crossover, and it's pretty hard to argue about MTM design with the guy who invented it. As for BSC, compensating for it in the crossover, it can't accomodate room placement, which interacts with the baffle step. Compensation via DSP correction fixes both the ** and room issues.


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## looneybomber (Sep 20, 2006)

Jason Schultz said:


> That would be great if you found it but don't look to hard because I found out through Bill Fitzmaurice that it is more of an issue with centre channels because it leads to a much narrower dipersion pattern. With virtically arrayed drivers however it might be an advantage because there will be less reflections from the floor and ceiling due to a narrower virtical axis response.
> The tweeter i have is round with 104mm diam . I'm going to grind off sections top and bottom to make it narrower horizontally then mount it in a recessed area in a D'Apollito config. the C TO C spacing will still be about 8 inches apart.


Well here is a quick conversation I had with a member on HTG.
http://www.htguide.com/forum/showthread.php4?t=31102


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## Jason Schultz (Jul 31, 2007)

thanks for that link looney. I'd love to have that lambda TD 12 to play with1!! I still think i will build a MTM and use a BSC later.I think this would be a smoother way to adjust For baffle step loss. It seems to me that trying to acheive it throgh the xo would result in more of a stepping down in DB at each driver rather than a smooth descent (make sense ?)


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## Aaron Gilbert (Nov 12, 2008)

I have successfully used the Morel MDT-12 tweeter with a simple first order crossover at roughly 3.5 kHz. There's only one component in the entire network - ok, so it's two capacitors in parallel. The MDT-12 is a small faceplate tweeter at just over two inches across. This design sounds just as good in the mid-high end as any of my significantly more complex designs, some may say better. I highly recommend this tweeter.

Here's the response of that unit:


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## Jason Schultz (Jul 31, 2007)

Aaron ,well done. the response is remarkably flat. 
how do your tweeters handle power when you crank things up though.

I have already purchased tweeters Vifa D 27 TD's. they are tried and true without build quality issues. They have a fairly large face plate though which i can grind down to 72 mm at top and bottom edge. I will now use LR2 network at 3000 hz. This will be my first real xo atempt but i will at least have some measurement equipment to " see what i am doing.


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## Aaron Gilbert (Nov 12, 2008)

Jason Schultz said:


> Aaron ,well done. the response is remarkably flat.
> how do your tweeters handle power when you crank things up though.
> ...


They handle power remarkably well, better than I would expect given the crossover slope and frequency. That said, they have only been used as stereo speakers outdoors for the most part. Although higher than a level I'd probably use in a small room, that still isn't anything like home theater levels. And, they're rated at 80 watts RMS, which is higher than most of the other tweeters I have used.


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## jeremy7 (Feb 7, 2008)

three months ago I wrote in this thread that I couldn't think of any successful speakers off the top of my head that used a 1st order xo on the tweeter. I was just reading in stereophile magazine about the new thiel cs3.7 loudspeaker, and it uses an acoustical 1st order xo on all the drivers. In addition the article states that most of thiels loudspeakers use 1st order xo's. However, thiel also has his tweeters designed and built according to his specs. Another thing worth noting from the cs3.7 article is that the tweeter is coincidentally mounted on a 4.5" corrugated flat (not conical) mid range that is supposedly "linear up to around 20khz", possibly allowing a higher cross point. I could not find in the article where the xo points were.


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## jeremy7 (Feb 7, 2008)

Oh yeah, those thiel cs3.7 loudspeakers are just under $13,000 a pair


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## F1 fan (Jul 6, 2006)

jeremy7 said:


> three months ago I wrote in this thread that I couldn't think of any successful speakers off the top of my head that used a 1st order xo on the tweeter.


Besides THEIL another very sucessful speaker brand that uses 1st order networks exclusively is Vandersteen.Others include some Dynaudio models,Sonus Faber and I believe Dunlavy also used them but I think they are now defunct.


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## delphiplasma (Oct 22, 2008)

Good results can be had from a 1st order XO. However, it took me a of a long time to find a dome tweeter that could provide the smooth results as with a second order XO. I do cross them over at a low frequency 1.5 kHz. The tweeter has a larger than normal diaphragm area and a low resonance. But at least you overcome some of those phase distortions.


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## norcad (Aug 17, 2006)

Both Bowers & Wilkins, and Impulse speakers are using 1.order XO.
I have tried Seas 27TFFC with 1. order at 3khz, with a Seas MCA15 mid. And it sounded much better than I had expected. Measured 300-20000hz +/-2dB at one meter, believe it or not :yes:

A friend also uses the Vifa DX25TG with 1.order at 3,5khz, and it sounds great.


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## jeremy7 (Feb 7, 2008)

Both Bowers & Wilkins, and Impulse speakers are using 1.order XO.
I have tried Seas 27TFFC with 1. order at 3khz, with a Seas MCA15 mid. And it sounded much better than I had expected. Measured 300-20000hz +/-2dB at one meter, believe it or not

A friend also uses the Vifa DX25TG with 1.order at 3,5khz, and it sounds great.







norcad
I was seriously considering that vifa tweeter for a project. Do you by chance know what the other speaker was that he used with the dx25tg? I was thinking of using the vifa p13wh with it. Ive heard very good things about both. The dx25tg i read on LDSG websight to cross it over at a higher frequency like your friend did, and im intending to do that. however the p13 is a 5 inch speaker and im concerned about beaming as my crossover approaches 3k and beyond.
thanks 
jeremy


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## norcad (Aug 17, 2006)

jeremy7 said:


> norcad
> I was seriously considering that vifa tweeter for a project. Do you by chance know what the other speaker was that he used with the dx25tg? I was thinking of using the vifa p13wh with it. Ive heard very good things about both. The dx25tg i read on LDSG websight to cross it over at a higher frequency like your friend did, and im intending to do that. however the p13 is a 5 inch speaker and im concerned about beaming as my crossover approaches 3k and beyond.
> thanks
> jeremy


Actually he has tried an 6,5" old Seas, and 6,5" old Vifa, I think it was C17WG(something), its not in production any more.
BTW beaming"problems" isnt that important, when you use an 1.order network the transition between mid and tweet is smoother. I have a hard time to write what I mean in English, sorry.


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## DrWho (Sep 27, 2006)

jeremy7 said:


> I'm not sure what type of quality you're trying to achieve or whether your planning this for a two way or a three way. I have seen/heard good quality two way designs with a first order low pass on the woofer, but I'm not aware of any successful designs with a first order high pass on the tweeter. I personally would not use anything lower than a second order on a tweeter. My biggest reason for this is that I don't believe tweeters enjoy too much excursion, and if I'm not mistaken excursion quadruples every octave. In other words your tweeter increases excursion with decreasing frequency at a rate very close to 12db/octave, so a first order high pass will actually allow the tweeter to increase excursion below the crossover even though the volume is dropping 6bd/octave. This I believe can contribute to distortion.


For what it's worth, a quadrupling of excursion per octave is only 6dB per octave...

The biggest problem with a first order xover is that the xover frequency changes with impedance...and the impedance of a tweeter is going to look like a roller coaster with a large spike around the Fs and then a rising impedance above the spike. At the Fs the tweeter is underdamped so you will have the most excursion...and then the higher impedance causes the xover frequency to "be lower".

Anyways, a first order xover ends up being mostly constant excursion and should keep the tweeter movement under control. However, all that extra excursion results in gobs of intermodulation distortion.


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## norcad (Aug 17, 2006)

DrWho said:


> For what it's worth, a quadrupling of excursion per octave is only 6dB per octave...
> 
> The biggest problem with a first order xover is that the xover frequency changes with impedance...and the impedance of a tweeter is going to look like a roller coaster with a large spike around the Fs and then a rising impedance above the spike. At the Fs the tweeter is underdamped so you will have the most excursion...and then the higher impedance causes the xover frequency to "be lower".
> 
> Anyways, a first order xover ends up being mostly constant excursion and should keep the tweeter movement under control. However, all that extra excursion results in gobs of intermodulation distortion.


I will say the biggest problem is the distortion. But it is a much smaller problem than I thought before I tried myself. The impedance isn't a problem if you are using measure equipment, and see what you are doing. And of course it is better to use a tweeter with low Fs, like the 27TFFC's 550hz.
The real benefit of the 1.order network is transient respons and flat impedance and phase, something small tube amps will like.
The only problem with my Seas combo was a little to much output in the 2-5khz region. The solution was to move the so point on the tweeter a little higher.
But if you want to play load and thinking of party speakers, 1.order is not a great idea.


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## delphiplasma (Oct 22, 2008)

As Norcad mentions the real benefits from a 1st order XO is improved transient response, and phase distortions. The tweeter, however, needs to be very carefully selected to reap those benefits. Low resonance in a tweeter design is a big plus when working with a 1st order XO.


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