Xmax A12p

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Hello, Mark!
Is it possible increase Xmax for Alpair 12P? Want try it with Linkwitz transform in Closed Box.
Best regards, Dmitry.

Hello D,
What amp are you using (power rating)? How large is your room? What types of music do you play?

Xmax on the Alpair 12P is already large but not to be used all the time. Reminder, it isn't a high power driver.

Thanks
Mark
 
I don't think that you understand the magnitude of the power and excursion that a LT requires. I have a sealed 12" driver that does essentially what an LT does. At 30Hz, the 12" driver runs out of excursion -- +/*12mm at 500 watts to do 30Hz @105dB @2.5m. That's a 12" driver. The A12P is a 6" driver. There is simply no way to get 30Hz out of a sealed A12P at anything above say 70dB.

Bob
 
Hello, Mark.
I'll try to use your driver with Holton amp for experiments. As you know, the more Xmax, the lower the frequency, which can reproduce a speaker with a Linkwitz transform. In this variant, I can get 35 - 38 Hz. I would like to enlarge.

I think you're confused between the driver's frequency in free air (Fo) and the practical (actual) limits of box alignments when applying the same driver.

Take note of Scott, Bob and similar senior forum members who have a large understanding on using full-range drivers. They have much knowledge and experience.

Ask them nicely for their help to get a sealed box alignment that will work.

Thanks
Mark.
 
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...As you know, the more Xmax, the lower the frequency, which can reproduce a speaker with a Linkwitz transform...

Not so. Not by itself anyway, without major caveats. LT requires the drive unit to possess very high power-handling levels (especially if you require more than whisper-level SPLs) since you are pumping considerable current into it. With a relatively small wideband drive unit like the 12P which is not designed for woofer duties, you'll fry the voice coil if you try pushing it particularly hard. LT was primarily intended for bass drivers -big voice-coils, high power-handling & to allow more practically sized sub-woofers. Also good for line-arrays.

...In this variant, I can get 35 - 38 Hz. I would like to enlarge.

Check the power-handling and the SPLs that will be available. Which brings us back to the next points.

-The 12P is not designed to be constantly hammered to, or near, rated Xmax like that; a point Mark regularly makes with all his drive units. It has wide excursion, but it's there to handle occasional LF dynamic swings when reproducing music at a more 'normal' average SPLs. If you run it to the limit of travel, you have nothing left to handle these dynamic peaks. And ultimately, you'll reduce its lifespan. You don't run a car flat out all the time -same deal with drive units. All of them.

-Xmax per se doesn't mean much since there is no industry standardised definition about what it is. There are numerous ways of defining it & the calculations all give different results for the same drive unit. Smashing. Personally I think distortion levels (2nd - 7th) at different drive levels to be rather more useful, with a figure given for maximum excursion beyond which the driver should not be run (especially if travel is not limited by the suspension before the VC smacks into the back-plate).

-Even if you could get around the above, as previously noted FMD (Doppler distortion if you prefer, although it's arguably not the right terms) comes into play. The HF in particular can get rather odd when reproducing a signal on a cone that is moving nearly 1/2in back & forth. This cannot be engineered out; it's not a matter of driver design, it's the laws of physics. It's not an issue for a bass / sub-bass driver, since they are functioning over a very narrow BW, but it can be for a single unsupported widebander.
 
If you want to LT a driver to low frequencies, that would be best -unless of course you only require output at very low levels. It might not be what you want to hear, but wanting it to be otherwise doesn't make it so, alas. It can be done with multiples, but you need the cone area & power-handing capacity.
 
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Ok. Thanks for all the criticism. I'll be back to multiband systems.

Hi D,
Not sure why you've chosen to use the word "criticism". Experienced forum guys were trying to help, but you ignored them.

You didn't give any details on your box design (size, alignment, calculations etc), nothing about the music you want to play, nothing on room size.....but you still got advice that's likely saved wasting your money.

You lack full-range design experience, not a problem, everyone can learn. Sadly, you ignored a primary functions of this forum which is seeking and/or receiving knowledge/advice and sharing ideas.

Mark.
 
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Dear Mark. The word "criticism" in the Russian language has no negative connotations. Sorry for my poor English.
And I just asked whether the production drivers with extended Xmax, nothing more. Box is very easy to calculate, especially when using Fibonacci numbers. Music, room sizes should not matter. If your speaker system can only play a specific genre and to some specific configuration space, it is a bad system. I completely lack the knowledge in designing multi-wave systems, but I do not consider Doppler in driver. My mistake. Wanted to get everything out of nothing. It does not happen, I agree.
Nevertheless, I'll try your item with Linkwitz transform. On occasion...
 
DIM as i see it by own sims with LT circuit. When doing small helper circuits with OPAmps as example buffers, high/low pass and gain, a good electric specs can be maintained from input to output by good quality OPAmps passives and clever circuit. A LT circuit degrade electrical specs at output no matter how expensive OPAmps and passives used, therefor if used try to route that only to a narrow BW in a less revealing frequency area especially not the middle area and up because you get a degraded electrical signal quality after a LT. So using it with a FR is not good because the degraded electrical signal quality is presented to listener by mid to hf frequency, and add that Scottmoose mention same happen acoustic for the driver that mid to hf be degraded. From my view if sealed is a demand add quality EQ to get needed frequency curve by offering SPL.
 
...The word "criticism" in the Russian language has no negative connotations. Sorry for my poor English.

Your English is better than our Russian.

Box is very easy to calculate, especially when using Fibonacci numbers.

True, although Fibonacci numbers don't make much difference. A little. Sometimes. Depending on circumstance.

Music, room sizes should not matter.

They do matter, because that is fundamental context. If a person only has a small room & listens to light chamber music, they do not require an Altec VOTT derived system with horn loaded 16in woofers. A compact monitor will do what they want. If a person lives in a converted barn, has a very large room & happens to like Mahler at concert hall SPLs (approx. 95dB average at the listening position + at least 25dB dynamic range available on top of that), then a small monitor is not going to do the job. They need a large system with high efficiency woofers & probably horn-loaded compression mid-tweets.

You can LT an Alpair 12. Just don't push it too hard.
 
Well said, Scott. In addition, we need to consider speaker position relative to listening position. Smaller systems are required even in large rooms if nearfield speaker positioning is preferred. One can have a very musically satisfying system using 7A / 7.3 Pensils in a nearfield arrangement.
 
Dear Scottmoose, I have no tasks to sounding sheds (if I understand correctly what you mean). And who would ever think to use the small speakers to work in large rooms? To do this, we usually use a large system, right? Such as our bipolar speakers ...

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