GoodSoundClub - Romy the Cat's Audio Site

In the Forum: Horn-Loaded Speakers
In the Thread: Macondo’s Midbass Project – the grown up time.

Post Subject: Midbass horns, latest story.Posted by Romy the Cat on: 6/2/2013

A few months back a audio guy visited me and after a listening session I asked him if he can report any problems with sound. He reported that he hears a slightly more prolonging decay at upper bass then what he suspect to be. I knew about this effect but I felt that it was in very minor scale. As the larger picture I have observe this effect many times, for instance here.

http://www.goodsoundclub.com/Forums/ShowPost.aspx?PostID=16461

… where effect was part of a larger picture.

It did not bother me so much as with my type of music I feel that slight longer decay at upperbass helps to get an illusion of larger concerts halls, never bad, isn’t it? The effect was very minor and in my view negligible.

As time goes by I observed that the effect was growing and growing and last 2-3 month it become some kind of almost a conspicuous boomines at upper bass… I tested many times all calibration and filtration and I am very confident that the amps, filters and driver are operating where they shall be. It is not too unpleasant but notably. I was not in a rash to fix it, not to mention that I have no idea what to fix. I was not in a rash as nowadays I turn my large playback only to blast my Bruckner at full power and the rest I tend to play on Pilot playback – it is summer and it is hot.

Two week or so a local audio guy visited me, listened my playback and insisted that the problem that he hears I did not have it before. This was quantifiable evidence that something is objectively wrong. I knew it but I was not willing to knowledge it as there is no explanation for it.

I spend whole nigh trying to figure out, listening, experimenting. I discover that if I go for third order filter on Midbass then I get appropriate sound but I do not understand why after two year of operation the midbass horns started to sound more extended to higher knee. The softening of the suspension and even paper would not be responsible for it as not primary resonance slid away but HF extension. I did short my 18mF coil with 100uF electrolytic and I get the OK sound but still I need some explanation.

The leading idea is ugly and I hope it is not true. The idea is the drivers in midbass hors get demagnetized and this lead to HF extension. Usually as the LF drivers demagnetized then we lose definition in lower knee. It does not feel that it happens. However, perhaps as the driver is locked in back chamber then it is not so obvious that it lost the magnetic force. I do not know and I never heard the fully charged and then discharged Alnico driver in properly operating horns. The whole presumption is ugly as I do not see myself removing the driver from horns and send them out to recharge each 2 years. Perhaps I needed to put the magnet charging wire in the back chamber and recharge them right there in attic? Well, if I go for this then I need to be sure that it WAS the problem.

Rgs,
Romy the Cagt

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