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Romy the Cat wrote:

I will slowly upload, as time permits to write them, different posts on the subject of Ultimate MF Compression Driver.

The subject of bandwidth for Ultimate MF Compression Driver is complicated subject. If to look at the major questions for this subject then they will be the very simple: how low it shall go and how high shall it go. It does not sound complicated the answer is not so simple.

Let start from “how high shall it go”. There are a few schools of MF implementation by compression drives:

a)  MF driver gores to 6K, then another upper MF driver and then tweeter.
b)  MF driver goes to 10K-12K and then tweeter.
c)  MF driver goes to 6K and then tweeter.
d)  MF driver goes to 15K and then tweeter.
e)  MF driver goes all the way up and no additional tweeter used.

Let analyze the implementations.

The implementation A. There are very few companies that support this implementation. This setting requires superb driver’s time alignment, axes aliment and driver’s TTH characteristic match. This configuration is the best suites for multiamping. The major problem with this configuration is to dealing with lobbying of HF drivers but with vertical configuration it is doable. Ironically the only company that supports this configuration (Goto) does not believe in alignment, vertical configuration and their reputation in TTH filed is very questionable.  Anyhow, it is a legitimate configuration but I do not feel that this is Ultimate configuration for MF driver as it is two or more divers that cover MF. The biggest problem with it is the fact the very few people use this configuration and therefore there are very few or I would say none of the drivers made for this configuration, and whatever is made id not tested properly. No one will do a dedicated compression driver for one octave, like from 6kHz to 12kHz. What companies do is to designate very much the same driver to be upper or lower MF by using diaphragms with different Fs.  Some very few manufactures (like Goto) do make different drivers for upper and lower MF but since Goto users are mostly Morons and Goto themselves are very controversial I would not trust to what they do.

The implementation B. This configuration that I use and I find it more comfortable for Ultimate MF Compression Driver. From one side the driver does not go to high and do not deal with problem in implementation C. From another side the 12K is itself is self-sufficient listening range and an addition tweeter does not add sound but there the artifact of sound. It is very important as driving tweet up and down you do not change the amount of sound that tweet output as it happen in the configuration A but you rather change ONLY the amount to HF. If tweeter is closed very low, like 5-6K then you can’t adjust your HF and you MF separately.

The implementation C. This is the configuration that I do not like. The MF and Tweeter are locked and need to be balance according to MF and there is no way to dial in the HF. Some people go away by using very harsh tweeters in this configuration or the tweeter that have a small thump at 12-13K region. This give some help bit still I find it very flexible. Your room and your listening distance might have very different acoustic requirement at 6K and 12K and using a single driver that cover the whole upper MF and HF range is a bit problematic in my view.

The implementation D is not bad if our driver can handle it. The very minor problem that I see in compression drivers is hat in order the driver to be able comfortably and clearly to shoot all the way to 15K the drivers need to have small and very stiff diaphragms. Thos small- diaphragms most of the time demonstrate harmonic deficiency across MF and I more incline to use MF compression driver with fuller body.

The implementation E. In my estimation it never happened but it always right thing to do to switch your playback this configuration and to hear what your MF driver dose atop.

So, my own preference is to have MF with bass channels to run with playback and to have auditable a full range, fully balanced sound. Then add a tweeter but very surgically and very purposefully.   Mostly the configurations B feel friendlier to me. Still, I have to admit that if a person knows what he is doing and have right objectives then the very identical sonic results might be obtained by using any of the mentions configurations.

Now about the bass region – how low an Ultimate MF Compression Driver shell do? Some people would like to have a driver that goes down to 200Hz and some people use a driver from 1000-1500Hz and up. If the driver has bottom of 900Hz as many of them are then they mostly too cold sounding drivers. I think the ultimate range of MF compression driver still starts from 500Hz.It would be nicer to have a driver to go lower but an Ultimate MF Compression Driver would be use in Ultimate configuration that in my mind imply a dedicated lower MF channel the remove the LF stress from MF diaphragm. So, if the Ultimate MF Compression Driver is used from 1000-1500Hz then why shall it be able to play 500Hz? The answer is: he harmonic reserve – the driver that will be suited for 500Hz will have larger cone and softer sustention and consequentially it will play 3khz with more harmonic richness.

So my vote is for 500Hz- 12000/13000Hz driver. That is all that is bandwidth related…

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