How lucky I am! The Melquiades bass channel at full throttle gives me just enough gain to power my Midbass horn to the reference level of my MF channels.  That is truly a very lucky thing. The biggest dilemma I am thinking now is type of the filter to use in the Milq’s bass channel input. I can go RCRC filter and I can go LC filters. Both will work fine. Currently I implemented RCRC filter (thanks, Dima for help with mathematics) and I am contemplating if it make sense for me to go LC.  I would need a 10H indictor and I have found that Sowter has a very cook, u-metal enclosed, miniature choke #9810:

http://www.sowter.co.uk/acatalog/SOWTER_TRANSFORMERS_EQ_INDUCTORS_6.html

This is exactly what I need but doe it worth it? Briefly let me to lay down the cans and pros…

LC is better because along with cap it will write a perfect second order curve that will be consisted to the very stop band. This will allow having a stable Bessel Q and absolutely no phase or amplitude anomalies. In RCRC filter the first filtering section talks to the second one and the curve reportedly if screwee….

RCRC is better for MY application because a bandpass signal goes only across 2 resistor. The HF that are not the part of bandpass are going via caps to the ground and get shorted. So, the sound worsening that happen in caps does not go to load. Also, the bandpass signal does not go over 3 miles of wire in he indictor.

Honesty I have no idea what to pick as I have do recognize a rational on both sides. Did anybody compare those two type of filters sonically?

Listening my new midbass horn, just left channel for now, I would like to share my observation so far about sonic result of the project.  Generally the sonic result of the project have exceed my expectations, however not always in the directions what I expected. Some aspects of my midbass horn sound make me to look at some things from a slightly different angle, below I will explain it. Take under consideration that my midbass project is not completed. Some  things  in the midbass sound will be  changed, unquestionably improved – I still  am learning the character of sound in my new room and from my effectively new playback system.

Now about the midbass Sound. It is very difficult to talk about midbass sound without referencing it to the sound of the rest of the system. The sound of the entire system is not where I would like it to be for now but even in the context of current playback state I might confidently say that midbass is very fine.

All my fears about midbass that I accumulated over the years of listening of different midbass solutions did not realized in my horn. I have no idea what I did specifically right or if anything that I did in my projects is directly responsible for it the result I got in my view has no resemblance to midbass I hear so far.  A midbass horn always sounds impressive as midbass horn is. Good or bad but it always demonstrate it presence. The best midbass horns do it with superb softness of bass notes and with a very fine harmonic infliction of very fine honk. In this case “fine honk” I use very admirably as if it tactfully done then I very much appreciate it. If you read the beginning of this thread then you would see that the super softness was my one of the primary objective.  Well, this midbass horn taught me something else – something that I did not knew and did not experience before.

As today my midbass horn has no even signs of honk or softness. The tone from it so clean that it reminds me the cleanness that I had with my woofer towers in the old listening room. Also horn absolutely does not show itself off – with a proper fine calibration – thank God I have ears - it truly stays behind and plays only what is being called. There is not “in face” pushing with it dynamic or with it chromatic. There is absolutely no forwardness or aggressiveness. There is no midbass noise or tonal disorientation. It is so clean, so elegant and so inconspicuous   that it took for me for a while to get use to it sound at properly balance the midbass output to the rest system. The horn does not produce soft bass as I was striving but rather the “Critically Proper Bass”. It kind if tunes itself to the way how a given phrase need to be played it can play orgasmaticly soft and sometime it throw such a hard phrase as it is driver from 1000W SS amplifier with 180 out transistors. Stunningly the horn develops this hardness from nowhere, with no preamble. It is like most of the figure scatters before jump  they let themselves a few feet of preparation and then there are some that shot themselves  in air juts so suddenly and so without any “prelude”. This horn does the same. It might play overly soft and lash and out of the blue it developers a rough wave of super hard dynamic that shoot itself out of horn like from a canon.

All of it can’t be called “impressive” but in reality it is not. All those beautiful things the horn does somehow that it is become very organic part of general sound. I truly hate those moments when sound reproduction efforts do the job so well that it deliver to a listener a micro-pleasure in audio realm.  In new room I do fight in my calibration to get rid of this effect and the horn complies brilliantly. The back location of the horn is not a problem at all, contrary to my fear. It is a subject of sane calibration and appropriate use and from where I stay today it is not a subject at all.

Still, I did not mention the most important thing about my new midbass horn. This most important and the most astonishing   new characteristic of Sound I did not pursue and I got it purely accidently. I did not talk about it in this thread and it took for me two weeks to understand the effect. I never experience this effect in audio in this way before and it took for me while to think about it. I do not have time to write about it now as it might be a very deep-sited concept, larger in meaning then my projects, that in a way might alter a whole perspective how midbass horns design need to be approached. This coming week I’ll put some thoughts and observations together I will write about it, perhaps in a new thread.

Romy the Cat wrote:

Still, I did not mention the most important thing about my new midbass horn. This most important and the most astonishing   new characteristic of Sound I did not pursue and I got it purely accidently. I did not talk about it in this thread and it took for me two weeks to understand the effect. I never experience this effect in audio in this way before and it took for me while to think about it. I do not have time to write about it now as it might be a very deep-sited concept, larger in meaning then my projects, that in a way might alter a whole perspective how midbass horns design need to be approached. This coming week I’ll put some thoughts and observations together I will write about it, perhaps in a new thread.

http://en.wikipedia.org/wiki/Dynamics_(mechanics)

Here, in very different dynamics pattern is where my new horn demonstrates absolutely astonishing skills.

Pretty much all bass that I ever hear in sound reproduction (and I did heard what a lot) was based upon “point of no return” idea. If we look at the dynamics of bass at high speed film then a bass harmonics will open up, the

Tone will roll to it; targeted pitch and then we have a combination of electrical, mechanical and acoustic decays. There is however an interesting moment. When voice coil got the pulse voltage of the midbass note then the enter bass is constructed. The voice coil pushes the diaphragm and from here there is nothing that might stop the bass note to show itself off and consequential participation of the electrical and mechanical after effects. We so accustomed to it that we do not even feel that anything is wrong with it. Here is what my new midbass horn enters the battle and show off that the back, the “dark side of the bass note” is also a very powerful expressive tool. Somehow my midbass horn is able to control the bass note not only in the leading slope but also at the decay.

This is VERY different feeling and it took for me while a while to understand and to get accustom to it. A few days ago I have visitor, a local audio guy, who came to me listing room with no invitation, trying to listen my new setup. I played a piece that he very much knew and on orchestral midbass crashes he felt that there was not crash of appropriate mass. The was in the middle of my thinking about the value of the midbass crash – I exactly understand how he felt but as now I believe that he was wrong in his expectation. My playback instead of uncontrolled generic crash offers an opportunity to have controlled music-specific crash – this is so new and so unexpected that a person need to get use to it and I never heard in regular audio. In regular audio we accustom that any loud midbass tone get converted to sort of speed bump. You run a high speed, hit the bump and have your “point of no return”, what you fly in air and you have a generic expectations that the landing is coming. Interesting that sending you to air is very much depending from the leading profile of the speed bump. Your return however hardly read the back side of the speed bump (unless you drive VERY slowly) and it would be mostly the subject of your car mass, electricity of your suspicion, force of gravity for your given planet and so on… Sounds familiar? Here is where my midbass horn behaves differently it reads the back side of the midbass speed bump with a fanatical precision.

My midbass horn has very little this common midbass denominator and it makes the notes much more distinct. It also reduces this midbass crash noise very effectively. I was asking myself what I did in my midbass horn so right that lead to this accidental magnificent performing quality. The analogues answer is that I did nothing right or wrong. The result that I have is a normal for a car the drive very slow, does not use own moving mass. Welcome to the world of NATURALY flat impedance.

As I said above my horn as it got burned in does develop more distinct impedance change during it resonance but this impedance change is amazingly low. Going over even resonance frequency I have around ONE OHM change – this is absolutely unseen by me before. What is superbly important is that this superb impedance flatness is accomplished NATURALY, with no zobel resonator and while the driver produce the proper frequency range. The only similar effect I ever observe in audio when amp with current feedback and negative output impedance was driving large inactive woofer. The configuration was able to accomplish a stunning bass decay but it had “no bass”, to get bass the setting required EQ. In my current setting the EQ is done by horn, also naturally. I came to thin in this association abs ONLY my new midbass horn and the negative output impedance setting were the cases when I was not able by ears to guess the horn lower frequency range. I usually very good with it but here the horn sounds much lower than measured.

So, what I have in the end. I have a driver that for whatever reason demonstrate a stingily flat impedance in the given horn and driven what whatever it driven (not ultra low impedance SS amp). I have a horn that practically does not experience any throat reactance as it has no reflection. I have a drive that does not use own mass or excursion to create pressure. Is it some kind of perfect setting? Perhaps but I will be lying if I say that it was intentional. All of it came as accident, sort of come the territory…

In context of my new experiences I would like to propose a few additions to my “Macondo Axioms”. They are not THE Macondo Axioms but rather the midbass ideas that I learned during the last two weeks.

1)    Proper midbass sound happens only if a horn shots in open air. Any reflections back to mouth create impedance bumps and  harmonic generality.

2)    Midbass horn have be driven  by lowest impedance. If you use SET amplification then use as lowest loading your amp gain/power permits.

3)    I have no idea what in the Vitavox 15” driver loaded in my horn made the impedance so flat but if some kind of rule of linearization of impedance by horn does exist then  this rule must be followed. The effect of  a midbass horn to impose it's super authority over the “back side” of the bass note is too powerful to discard it.

4)    A midbass horn MUST NOT be a lowest channel in an ambitious playback system. A complementary NON-HORN ULF channel is required.

That is basically all. This dark side of the bass improvement is the biggest accomplishment that I see in my entire project.  I know that it would do upperbass but I have no idea that it will extend my views about super controlled midbass decay reproduction. We are so accustomed in sound reproduction that in midbass the resonance thump kicks in soon of later or that those electrical artificial resonators would remove life from bass notes that we do not even think that it might be different. My new midbass horn demonstrated and taught me that it is possible to do playback’s midbass decay without any “event”, nether mass-event of the approximating impedance dive or the depersonalizing event of electrical resonators.

jessie.dazzle wrote:

… I do not fully understand the relationship between output impedance and diaphragm control; also I don't know what you mean by "negative impedance". Your mid-bass drivers have 15 Ohm coils; from what you write, I assume you are driving them from 15 or 16 Ohm taps. Correct?