Passive Crossover No.2252 for Fostex T900A

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In this video we look at implementing a passive high pass filter for the stock Fostex T900A. Since featuring the tweeter in a recent blog, I was asked to develop a proper high pass filter for the super tweeter.
Original blog post: josephcrowe.com/blogs/news/pa...
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Joseph Crowe Custom Audio Products is a small business located in Canada. Owned by Troy J. Crowe, he offers custom audio products such as wood horns, crossovers, design and testing, or complete speaker builds. He provides services to either individuals, small businesses, or start-ups. All of his designs are available for personal use in the form of 3D CAD files or Drawings. Please contact for commercial licensing.
Troy J. Crowe has a background in Mechanical Engineering Technology with extensive experience in both the Audio Industry and the Automotive Industry. He does all his own design work and CNC machining. His focus is on audiophile two-channel music systems for the most accurate sound reproduction.

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30 окт 2023

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Комментарии : 15

@firstdaddy 8 месяцев назад

I too have experienced how different levels of stored energy at various frequencies can contribute to undesirable results. You seem to have corrected this issue which should correlate well with your subjective listening experience. Good work!

@impuls60 8 месяцев назад

But how will the phase rotation of the 4th order work with the midrange driver? Looking forward to see some measurements of this filter in a lp/hp crossover situation.

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

I'm going to go out on a limb here...but I have not experienced this as an issue in crossover design. From my experience, if the slopes match at the crossover then all is well. I'm referring to the measured response of each driver with the intended passive filter. To me, what matters is that the summed acoustical and electrical transfer functions combine to form the target slope. So that means you can combine whatever order you need to achieve the desired slope. Horns have a very steep drop below the cutoff frequency of the horn, which requires the low frequency to have a much higher order electrical filter to match the strong acoustical filter of the horn's response below cutoff. If I am wrong I would like to know what metric shows me this. I always get a flat response through the crossover region if the slopes are symmetrical.

@tomekwhite 8 месяцев назад

Excuse me Joseph, but how come there is “dramatic improvement” in CSD? To my eye stored energy just evened out across the spectrum (there is more “ringing” than originally) and it rings exactly as long as before…?

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

That's correct, the improvement is just a you say, an evening out across the spectrum. Looking at it closer I don't think it's fair to call it a resonance, as the time scale is only 0.92ms deep. It's just the natural pistonic decay of the diaphragm. Most manufacturers have the time scale at around 6ms. So we ae straining at micro details in the data. The burst decay shows full decay by 6 periods across the spectrum, so not something that's even close to audible anyways.

@tomekwhite 8 месяцев назад

@@JosephCrowesDIYSpeakerBuilding I’m actually willing to agree with your assessment regarding audibility of this decay, however in this case you also have to agree, that mentioned “improvement”/“evening out” is purely theoretical - if the decay/“resonance”wasn’t audible in the first place then mentioned improvement is only “on paper” (still isn’t audible anyway).

@photorealismstr 8 месяцев назад

Have you tried digital crossover like minidsp;

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

I've tried the Hypex FA123 which is very low distortion and noise. But I've not tried some of the latest MiniDSP products. The third channel on the FA123 is lower power than the other two channels and only meant for HF drivers. So it sounds fantastic.

@JRadian 8 месяцев назад

That's WAY too much work and money thrown at fixing $1200/pair super tweeters! You still end up throwing away lots of sensitivity in the end. Fostex seems to publish just as fake measurements as Beyma does for TPL AMT tweeters.

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

ouch...you're not wrong.

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

The horn lens I developed has also addressed all of the issues with the tweeter where it will likely be just a very simple filter. But yes, why should one have to "fix" such an expensive tweeter. josephcrowe.com/blogs/news/fostex-t900a-with-horn-lens-no-2258

@davidkclayton 8 месяцев назад

Worthless, sorry, no instruments play Above 8000. Nor would you want to hear anything that plays that high.

@JosephCrowesDIYSpeakerBuilding 8 месяцев назад

I routinely do crossovers and the response above 8kHz is very critical to the overall sound quality. Why would think instruments don’t play that high? Do you not know there are harmonic resonances that easily extend in to that region that give the instrument its distinct tone and character?

@firstdaddy 8 месяцев назад

Not sure where you get the idea there are no instruments that play beyond 8KHz. The clarinet, flute, piccolo, violin, and pipe organ all can play to 8KHz or higher.

@davidkclayton 8 месяцев назад

@@firstdaddy you're probably right you could probably get an instrument to go beyond a reasonable scale but is that something you want to listen to? Here's a fun experiment for you. Get yourself a tone generator play an 8 kilohertz tone, I think you'll find that uncomfortably High pitched.