Usher 8945A with Vifa XT25

[lewisd]

Need some opinions

I've been planning on building a monitor for about half a year or so and have gone through many designs. I'm stuck on this one tho.
Essentially i want to know if the Vifa XT 25 (dual concentric) will go well with the Usher 8945A or 8945P(phase plug) for a 2 way bookshelf crossover at 2500 hz, probably using 2nd order, due to the low end distortion of the vifa.

Will the usher give clear strong midrange?

Does the airy characteristics of the vifa go well with the Usher? Zaph provides some very nice specs on both of the drivers if you need visuals.

Any suggestions would be helpful
Other suggestions are welcome (minus going to scan-speak for the woofer) lol too much money

What type of league would this speaker be in from the driver point of view.

thanks again
don

[ttan98]

I am looking at this design myself, refer to these sites for ideas:

1.http://www.partsexpress.com/projects...r701/index.cfm

2. http://murphyblaster.com/content.php?f=usher2way.html

3.http://www.markk.claub.net/usher_index.htm

you see you don't even have to design the x-over!!

[lewisd]

thanks for your response

can any body give me the characteristic sound of the Usher woofer. Warm, detailed etc. When compared to the peerless HDS 6.5" how does it compare??Midrange and bass.

thanks

[ssmith]

Originally posted by lewisd

Essentially i want to know if the Vifa XT 25 (dual concentric) will go well with the Usher 8945A or 8945P(phase plug) for a 2 way bookshelf crossover at 2500 hz

have you thought of the usher 9930 or 9950 tweeters?
I'm curious about these and the 8945's too.

[ttan98]

BTW I haven't build one yet, in the process of building.

I heard from those you have said that its has powerful bass, but the mid range is a little lacking.

It sure makes a good MTM speaker without A SUB WOOFER.

[Rounder]

As for your question for whether the airy vifa will suit the usher, keep in mind that usher is very similar to scanspeake, and vifa and scanspeak have been successfully matched together before in retail commercial speakers. The question is do you like the sound they produce?

Keep in mind that the breakup at 6.5khz really needs to be properly removed because if it shows up then sibilance will be heard.

And lastly make sure u do something with the elevated FR above 1khz, because it will give u a forward/bright sounding vocal. Oh and u realize the impedances dont match right? Could cause problems... Just throwing it out there.

[lewisd]

I've been designing several box sizes (data achieved from Zaph, Mark k and manufacturers spcs) using the usher and i am curious as to what the optimum box size that people have been using that resulted in good performance as the end result. I've designed pretty much everything from a bookshelf to a floor stander, but again software can only give me so much feedback, it comes back to what it will sound like in real performance.

Any feedback is welcome and appreciated

Donny

[Jay_WJ]

I've built a 2-way with the Usher 8945P. The cleanest midrange I've ever heard. Just what I expected from Mark K and Zaph's tests.

I've used a sealed design in my case. So I can't really help you much here. But all the existing three vented designs (Dennis Murphy's, A Feyz P's, and PE kit) with 8945P or 8945A use the PE .75 cu ft box. The A and P versions' T/S parameters are very similar.

That's why I suggested box dimensions with .75 cu ft in my 8945P design page:

http://www.geocities.com/woove99/Spk...Usher_2way.htm

BTW, I've modeled a xover for the 8945P and the XT25 for someone else. But the higher frequency response between the A and P versions are different. So, you may not be able to use it. If you still want it, though, I can send it to you. Let me know.

[lewisd]

Ah thanks jay

I have looked at your design before and found it very impressive design wise, can't tell the real performance but i bet it's very good. If you wouldn't mind sending that xover it could be helpful, i can work backwards and see what you did.

I am curious to see if you have a conjugate notch like zaph's and otherwise just see what you have done with the xover.
Was this another design you considered over using the HDS? if so y?

Cheers
donny

[Jay_WJ]

Originally posted by lewisd
I am curious to see if you have a conjugate notch like zaph's and otherwise just see what you have done with the xover.
Was this another design you considered over using the HDS? if so y?

Hi Donny,

I initially used a conjugate notch. But recently I learned that an LR4 design can be done without it. A shunt resistor in parallel with the XT25 can prevent a resonance-induced peak. BTW, an LR2 slope is not appropriate for the 8945P or 8945A due to their nasty response above 2.5 kHz (combination of breakup and rolloff). In fact, very few 7" drivers can be used in an LR2 design. The Seas CA18RNX is the only driver I can think of now.

I modeled the XT25 version because someone at PE forum asked me to do so. A downside of using the XT25 with the 8945P is that the problem of 8945P's 1.2 kHz dip cannot be addressed with a 2 k or 2.5 kHz crossover point.

Luckily I found the 8945A's frd file I traced before using Zaph's IB measurement, which is also very close to the PE measurement. So, I was able to model a xover for you by modifying the 8945P xover. For diffraction modeling, I used the same baffle and driver positions that I suggested in my Usher 2-way design page for a vented cabinet. The baffle is 8.5" wide. But this xover can be used with an up to 10" wide baffle without modification. A little wider baffle will only increase the lower midrange SPL a little bit. Below is my modeling result:





According to the XT25's distortion measurement, this tweeter can be used in an LR4 design with a xover frequency as low as 2 kHz. Take a look at Zaph's XT25 harmonic distortion sweep (http://www.zaphaudio.com/tweetermishmash/compare.html) and then the XT25's rolloff in the above crossover simulation. The XT25's distortions start to rise at about 1.5 kHz but its rolloff through the xover already reaches more than 10 db down at that point. So the 2 kHz xover point here is a good choice that avoids the XT25's high distortion range as well as the 7" woofer's frequency range that is prone to beaming.

The system frequency response turned out to be surprisingly good as a preliminary xover's. If you're going to use this driver combination, I'm pretty sure that this crossover will only need minor fine tuning to provide a satisfying result to you. Fine tuning options I can suggest are the tweeter level and the notch filter depth in the woofer network. The split padding resistors (R9 and R10) are on purpose. They were split to give better phase tracking as well as response shaping of the tweeter. To adjust the tweeter level, you need to vary R10, not R9. Changing R9 will only affect treble above 4 kHz. The series notch filter in parallel with the woofer is used to suppress a response hump around 700-800 Hz. Along with the primary 2.0 mH inductor, this notch filter works as a means of baffle step compensation. By adjusting the R1 value, you can conveniently control the midrange's brightness/warmness.

The designed listening axis is in the middle of tweeter and woofer axes.

Let me know if you have any questions.