Romy the Cat wrote:

Anyhow, I would like to add some addition to my “to do” list for 2008. 8) Try my new experimental AHFS in context of my RAAL “Water Drop”

OK, I would like to share with readers of my site a notion is that I am would like to look into. First think first let defend I call tweeter from now and below. A tweeter is something that use above I would say 10-12kHz. So, it you tweeter is crossed at 2.100Hz or 1.800Hz then do not read further - it would have littlie relativity to you.

I have notice is that in most oaf of the cases the high frequency solutions for our acoustic systems have inherent problems. The patterns with which our tweeters react to musical events have different impact my listening consciousness. It does depend in a way from the type and topology of tweeters used but still something fundamentally wrong with tweeters generally. I have no problems to resolve all tweeters problems (time alignment, all aspects of integration and etc …etc etc …) but still the tweeters jump out from what I feel is right presentation of sound. It is not my tweeter. I have good tweeter and it is very smartly used. The problem I report is applicable for all tweeters I have heard, including my tweeter.

So what it is. The problem that I see is a certain dynamic non-linearity of tweeters. A properly calibrated and integrated tweeter in some cases runs too hot during soft passages and some time too hot during the loud passages. When I am taking about too hot I do not really mean “bright” but rather a very minor deviation of what I would call proper balance. The proper balance could be evaluated not but by “sound too hot” or “not enough air” but rather by assessing the relationship between HF Spaces and MF space. Well, if the playback properly performs full-range and properly calibrated then it is possible to assess the relationship between HF Spaces and LF space but it is more complicated for most people as there are many “issue in this subject”.

Anyhow, I was trying to catch the pattern according to which tweeters do dry too fast of over spit the MF and I was not able to. That leaded me to invent a concept of “Active High Frequency Solution” – AHFS. This is purely conceptual invention and I have no specifics. The AHFS is a concept what a tweeter has own brain and can move own output in consistence with what MF channel does. I am talking an intelligent automated compressor/extender/volume control/harmonic fertilizer that execute some king of God know what kind parabolic or hyperbolic algorithm and changes the volume and harmonic content of tweeter in dependency of what HF and what MF do. Hypothetically I can see a mechanism, fed from HF and MF chanals, which in real time (1/10 of the tweeter rate) changes gain and loading of the output tube that drive tweeter. It is not so hard to implement – what hard is to know how to process and interpret the needs to this active non-linear correction.

I share this idea with some folks wondering what they feel about it. No one proposed any intelligent explanation or was able to collaborate the subject. No one except the RAAL’s Alexander Radisavljevic. Alex proposed a very interesting idea what it might come from. He suggested that the microphone compressors that pro flasks use mostly have limited compression bandwidth and they stop compression at 12-14kHz. The tweeters and particularly his ribbons are dynamically –linear at HF and therefore they just over-dynamic above 12-14kHz. I feel that it might be very plausible direction to think as I did detect that the tweeters that have own compression at higher frequencies (fabric tweeter) practically immuned from the problem. I was intentionally listening today of some recordings that use no compression of any kind and I realized that the problem is not there even with my tweeter. So, would it be that my tweeters have a need to recognize the type of the compression that was used during the recording, detect the excessive dynamic of the HF ingredient and then to implement in a real time a contra-measure to the problem?

Well, sometime I would like to attack this notion and try to execute some form of Active High Frequency Solution. If you, the readers, have any ideas, thoughts or initiatives on the subject that feel free to share.

Romy,

In all your search for better sound quality, did it ever occur to you that the greatest time-domain distortion might occur at the other end of the signal chain?

The problems you perceive at the upper end of the spectrum are as likely problems with the microphones used in the recording as with your playback setup.

Many people do not understand the scale of the issue. Small resonance (time-domain) problems in microphones become big problems on playback.

If you are making critical decisions about your playback system according to your impressions when listening to a recording - you had better be sure of the equipment used.

To me, it sounds like you are describing the sound of the condenser microphone (especially the measurement variety).

Don't under-estimate the lack of listening that goes into the design of the average microphone.

Most of the designers have never heard a horn system and are no more critical of the direct-radiator speakers than they are of their own microphones.

Andy