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Ronnie,

I’m sorry I was not able to detect the clipping you were taking about listening your file. However, if you can hear ANYTHING distorted at 1kHz (when ONLY your upper bass horn is playing) then you might consider the following: it has NOTHING to do with horn at this frequency.

1) The driver might be defective (do both change have the distortions? Do distortion take place when the driver is not loaded into the horns)
2) The driver’s outer suspension touches the mounting plat of the horn during the driver operation. (Put a few mm gasket between the driver and the horn and see if the distortions went away? Alternatively you might wet the back pane, then attach the driver, play it and then see if the outer suspension got moisturized)
3) There is some dirt in the front chamber that “rings” at 1kHz. (Disconcert driver and clean it up, use vacuum cleaner)

What crossover frequencies you use ay your channel?

Ronnie, I’m very confident that your “1kHz problem” is a pure mechanical accident and it has nothing to do with the initial design. I am sure that soon on later you will find what the problem was.  However, there is something that makes me concern about your horn much more then the “1kHz syndrome”. 

You see in the horns everything is connected….

I am concerned that in the horn you made sound might have compressed and suffocated …. and it would come directly form the horn design. I am not convinced (I never head the thing) in what I proposed and you should be the judge but let me to explain my rational to propose what I’m proposing

When I advocated use of Fane8M driver I meant that the driver does good job loaded into my 4” horn. Now, Fane8M is 150Hz-400Hz driver and at its bottom knee the 150Hz is kind of “pushing”. When we place a driver into a horn then the horn provide low frequency equalization. At open air the Fane8M roles at 300Hz-500hz (I do not remember correctly the numbers – I did it 6-7 years ago), in sealed box it goes down to 90H-120Hz. Surely, we do not want a MF driver to stress to the bottom of it’s capacity, and particularly those low-excursion drivers. So, if you listen the Fane8M in a sealed box then it would sounds fine at 700Hz but it will sound compassed at 100Hz….

Then we load the Fane8M into a horn. A horn equalizes low frequency up, the type horn that you and I use does + 6dB at it bottom. The key in here is to understand at WHICH FREQUENCY those + 6dB will occur. The lowest threshold of the equalization determined by… the diameter of the throat  - the smaller throat the stronger equalization at lower frequency. Now, let pretend that we have the identical deriver that sits in 4” throat ands in 6” throat (let disregard the back chambers). The 4” will make a 300hz-in-air driver to have +6dB at 120Hz but the very same driver that mounted into 6” throat will do +6dB at 180Hz. (All numbers are for the sake of illustrations). So, in order to make the same drivers into the different horns to sound 120Hz at 0dB the different horns/drivers should be driven with the different level of hardness. Interesting that in case of 4” horn the 120Hz at 0dB will be coming NOT FROM THE DRIVER EXCURSION (it not mass-centric but velocity centric system) but from the “artificial” horn’s equalization (in this case the word “artificial” is positive). However, in the case of the 6” driver the 120Hz at 0dB will be produced by EXCURSION OF THE DRIVER + “some residue of the horn EQ. Nevertheless, let do not forget that our driver might not sound as good when it stressed to operate too low. I would not even mention that fact the in this “EXCURSION” situation the driver is still sitting in a horn but in fact it acts as a direct radiator (there many other problems in this setting like Doppler distortions, “modulative boom” and so on)

This is why I generally advocate smaller throats… for a given driver. The Fane8M is fine with 4” throat, 115-120Hz but I feel that it very maximum that is possible to get out of this driver. I get in my smallish room 100Hz by back-chambering the driver and by picking some room gain (although the horns are in middle of the rooms). You have open back (which it fine). Your have the horns sitting in the middle of the rooms (where they should be) but it looks like your room is relatively large room. So, you might loose 10-15Hz in back chamber and I would say 10-15Hz  in the room. Then you might be loosing 30-40Hz because the 6” throat. Yes the driver still might make the 115Hz but it made but driving the driver harder and by use of the DRIVER EXCURSION INSTEAD OF THE HORN EQUALIZATION. This is the key to understand why the larger mouth makes horn idea not as worthy as it could be. In fact… if you drive the horn harder then you might have excessive lower MF that you would need to kill by filter…

So, I do not know if in your configuration with 5.5” throat the Fane8M was an optimism driver. I never used it this way but looking what the driver does in open air and sealed box I have my suspicions and it might act as the “oxygen deficient driver”. In fact, even in my 4” horn I might recognize the first signs of the ““oxygen deficiency” but I still was not able to fine better driver tonally with 1003dB sensitivity. If I were you I would try some other 8”-10” drivers that might go slightly lower then Fane8M, I would say for 10-20Hz lover. Do not forget that you with your horn will be using this driver at it’s very bottom with a great influence of the “direct radiation operation style”. The alterative version, if you LF section can handle a higher crossover point would be to high-pass your horn at 140-150Hz (where it still might act as 100% horns) and to listened if it sound better.

Ronnie, this all are juts my speculations and you feel free to regard them if you do not see any auditable avoidances of what I said.

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