LXmini 数字分频系统 DIY

扬帆远航

标题是不是不严谨呀？我以为是DIY数字分频，进来没看到这方面任何DIY。加了系统二字就不是DIY数字分频了？

linxbaijy

一个发烧友和SL讨论LXmini设计思路，虽然这个是贴在LXmini用户论坛里面的，但并无版权和设计细节，故转载如下。

After some emails mainly regarding the Design List:
http://www.linkwitzlab.com/Constant_dir ... _louds.htm

SL asked me to post my musings on the forum (for the benefit of others) rather than keep them in email form. I had a short conversation after adding some links to the Design List.
My response/questions in RED, SL in Bold
(I have added additional comments after SL's answers)

SL made the following comment (which prompted my questions):
SL: "Pluto sounds muffled to me in comparison to the LXmini. It must have been due to the Aura tweeter, but I am not sure what exactly was the cause."

So the following conversation happened (with my amateur speculation):
Hi Siegfried,
Thank you for your response, more idle musings that do not require any kind of reply:

Disregarding the hint of cardioid behaviour I wonder how FU10RB (with LX Mini style tube) and U22REX/P-SL would play on an LX521 style baffle. How that would compare to LX521, for a fully active three way solution, accepting lower output limitations.
SL: *** I would not add the diffusor and just leave out the tweeters. But why? I would expect acoustic benefits from such configuration. ***

I guess SL sees no benefit in experimentation with adding LX Mini style tubular diffusers to the LX521 baffle then.

Regarding LX Mini treble clarity maybe the lack of a crossover in the most important frequency range for directivity.
Perhaps the lower crossover frequency removes harmful distortions in upper mid and low treble caused by large excursions from the bass/mid cone, just as I found adding Pluto Plus to Pluto improved midrange clarity?

SL: *** I seriously doubt that ***

This makes sense, unsurprising response I guess considering SL's continuing development of open baffle, so it sounds like SL considers there is no subtle engineering trade offs here, or at least nothing that would be audible to human ear. Further consideration LX Mini upper treble is subjectively very smooth; if my suggestion here were to hold water then you would expect LX Mini upper treble to be inferior to Pluto but it isn’t. Again as with Pluto I do not miss the expensive tweeters I have used in the past. I had wondered if LX Mini might sound slightly rough (or lacking “air”) in the upper treble to younger ears but I hear no problems at all. As stated before the treble is subjectively superior.

To my ears adding Pluto Plus to Pluto removed a certain hardness from the sound of Pluto. LX Mini does not seem to need this at all.

SL: *** I think this is due to the radiation characteristics of the fullrange driver and its cone breakup behavior. This driver and its open baffle application make the difference in my mind. ***

For most of us I think this part can be taken as a given, the major part of the appeal of the speaker. A bit of OB performance that can work in a small room loudspeaker. I hope more Pluto builders will experience this.

When I added the bass units to LX Mini I found just more bass (and that the combo needs work). I barely miss them with LX Mini which I find strange.

SL: *** Note the intentional difference in stuffing and tuning of the woofer pipe. ***

I’m still using the Pluto 2.1 pipes and stuffing which were originally filled to 200g of stuffing per speaker; however I used 200g total per speaker of MDM-3 and some other lambs wool derived damping to make up the 200g and your LX-Mini stuffing instructions for MDM-3 would put the MDM-3 at just 130g per speaker –as opposed to 200g (per Acousta Stuf) - so perhaps my tubes are a little over damped? - all supposition without measurement.

I raised the coupler a little (and I have an additional mounting ring) so my tubes will still be a shorter than proper spec but the speakers sound really great. I’ve not detected any booming bass, just the opposite. However without measurements given that there will still be a small difference maybe you can take my comments regarding the bass with a pinch of salt. Come the good weather I should take them outside to measure them.

Perhaps some of your work coincides with the work of Earl Geddes. The directivity over 700 Hz being more uniform than Pluto......

Accepting that he does not want to illuminate the back wall at all he says:
“The response from 700 Hz to 7000 Hz is paramount”
“Above 700 Hz the polar response should be constant”
“Above 700 Hz the direct response and the power response must follow one another”
https://www.youtube.com/watch?v=fE2nWVwFT9k

SL: *** I agree, but not necessarily with the 700 Hz corner though it is near the upper limit of the ITD range of hearing. I suspect it is convenient for Earl, because his horn does not go lower. ***


Of course Geddes achieves 700 Hz upwards with an enormous 18” waveguide and he is openly uninterested in the pursuit of reproducing a convincing representation of an auditory scene of a concert hall event.

SL *** I am aiming for wider dispersion and more power into the reverberant field by using also the rear radiation, than Earl. He tends towards giant headphones at a distance. The LXmini is also somewhat like that. ***

linxbaijy

最后SL提到，就如Geddes 设计巨大的号角来达到一个远距离上的耳机的目标，LXmini在一定程度上也是一样的，殊途同归。

linxbaijy

另外一个对SL的LXmini设计感到迷惑，认为SL偏离了他一直主张的全指向和偶极的路线，SL说他的目标是要减少Pluto设计里面和房间的作用- Pluto要离后墙有一定距离才能有优秀的音场和定位，LXmini试图减少这种房间和摆位的依赖。SL依然认为偶极是最容易达到一个自然的声音，因为偶极没有箱子，偶极上出来的声音怎么搞都不会差。但全频的偶极很难办到，所以才有了Pluto，LXmini这样的一些设计。

BillM256

You can find my motivation and explanantions for the design of the LXmini at http://www.linkwitzlab.com/LXmini/Design.htm.

It was an attempt to get a speaker that is less sensitive to placement than the Pluto. An omni has maximum interaction with the room and I wanted to reduce the effect of the wall behind the speaker by not illuminating it. Clearly that is not possible at low frequencies with Pluto, but I did not mind because Pluto performs quite well close to a wall, which I find somewhat surprising.

But Pluto images better when further away from the wall, which is not an acceptable placement for that room. So a cardioid without a resistance box ( I hate box issues), which turns into a dipole when the woofer monopole is out of the picture, seemed like a worthwhile experiment. Both cardioid and dipole have have a theoretical 4.8 dB directivity. If I suppress the rear radiation from the dipole then the directivity increases to 7.8 dB. But I want the rear radiation to add to the reverberant sound field and therefore the diffuser. The dipole by itself becomes directional, but not as much as a monopole of equal diameter.

In the end you have a speaker that is acoustically small (an important criteria) that goes from monopole gradually to cardioid, to dipole with diffuse rear radiation. It becomes more directional at higher frequencies. Horizontal and vertical polar responses are nearly identical! Acoustically it is a coax, but without Doppler distortion.

I have not changed my opinion that full range dipole, cardioid or monopole are the optimum solutions because they generate a neutral reverberant field and make loudspeaker and room perceptually disappear. A dipole is just the easiest to implement and does not have a box. It is difficult to screw up with a dipole. It beats a box anytime. But it is also difficult to build a fullrange dipole.

Study my website a bit more because I am terse and provide little redundancy. I do not expect people to understand upon first reading. I am not writing novels like the audio press for easy reading. See my CAUTION http://www.linkwitzlab.com/index.html#CAUTION:.

Have fun, SL

旺德福

家电论坛里有个叫普兰的，专业搞音频工作，比较推崇电脑分频，用制作母带级别的专业音频接口，实现分频后再分开推各个单元
现在高端音频接口功能非常强大，实现复杂的分频和EQ调整可以说是小儿科，而且调校起来很简单，你可以参考一下
http://www.jd-bbs.com/thread-3491705-1-1.html

水晶

希望楼主翻译一下,以飨读者,(对于音响术语在线翻译基本不知所云).

pcello

linxbaijy 发表于 2014-11-11 19:56
一个发烧友和SL讨论LXmini设计思路，虽然这个是贴在LXmini用户论坛里面的，但并无版权和设计细节，故转载如 ...

看 不懂啊，林博能翻译一下吗？

gxcrt111

我也看成DIY数字系统了，原来DIY音频系统

nuaaz

linxbaijy 发表于 2014-9-28 03:37
1.  LXmini 必须数字分配，EQ曲线非常古怪，模拟分频没法办到。
但数字分配并非限制在minidsp一个方案上 ...

请现在有软件分频的方法了吗？ 如果能用Jriver 分频就好了。LXmini用的是全频单元，不怕烧高音，玩软件分频是最合适不过的了。

无花

顶上去，非常有兴趣

howewh

前辈能发个Plan给我吗?

logicart

楼主，垫高音管子的木块高度多少？谢谢！

HUAKYANT

林博，我也想做lxmini，大家现在还在做吗？群号是多少啊，谢谢

xzj1009

好贴  做个记号

qiqi283

HUAKYANT 发表于 2016-10-11 14:52
林博，我也想做lxmini，大家现在还在做吗？群号是多少啊，谢谢

怀念林博，这里发给你群号，Linkwitz同学会：118130806，大多数里面的大神们都在扯蛋，但所提问题都有人给你解答。

stevenlee2223

qiqi283 发表于 2018-12-31 05:03
怀念林博，这里发给你群号，Linkwitz同学会：118130806，大多数里面的大神们都在扯蛋，但所提问题都有人 ...

怎么搜不到这个群

binphy

这个群有问题，不要加

0754yj

binphy 发表于 2019-1-18 10:55
这个群有问题，不要加

这个QQ群建群至今已经九年左右了，一直都好好的没有问题，只不过这个群屏蔽了群搜索而已。