So today I removed some more stuffing inside. It seems the stuffing has quite a large effect and needs some carefull tuning.
I also did a quick distortion measurement at I guess around 2Vrms. If I find some more time I will do some more detailled measurements. But it looks already promising:
I also did a quick distortion measurement at I guess around 2Vrms. If I find some more time I will do some more detailled measurements. But it looks already promising:
I've been thinking of building this clone and wondered if anyone has an opinion on bracing? I believe that I read on build threads that a few people felt that the long panels might benefit from some additional bracing. Any thoughts?
BTW, I was wondering if anyone had measurements that are more clear than the copy of the blueprint that has been posted? I am having trouble reading some of the measurements and wondered if there was a set of exact measurements floating around.
JP
BTW, I was wondering if anyone had measurements that are more clear than the copy of the blueprint that has been posted? I am having trouble reading some of the measurements and wondered if there was a set of exact measurements floating around.
JP
I didn't try any high power into It. Its now just connected to my 70W receiver. Even with this it makes more than enough noise, on low frequencies even enough airflow 
I'm not able to do an absolute spl measurement right now as I have no real reference.
This box is already quite braced and very heavy. I might add some bracing later in the area where the drivers tap in the horn and near the mouth.
I'm not able to do an absolute spl measurement right now as I have no real reference.
This box is already quite braced and very heavy. I might add some bracing later in the area where the drivers tap in the horn and near the mouth.
Thanks for the very informative writeup. Excellent work.
I do have a stuffing question -
When I completed my recent tapped horn, I lined only the throat end of the horn path and achieved a relatively smooth frequency response that was quite similar to what Hornresp predicted, though down a few dB (which may be my microphone or measurement technique).
Your initial measurements showed a significant dip, then you provided updated measurements taken after you removed some stuffing. The change in the frequency response is significant. In post 28 of this thread, the entire path length of the horn is lined with what appears to be polyester batting. Where did you remove the stuffing from to cause the changes in frequency response?
Thanks.
I do have a stuffing question -
When I completed my recent tapped horn, I lined only the throat end of the horn path and achieved a relatively smooth frequency response that was quite similar to what Hornresp predicted, though down a few dB (which may be my microphone or measurement technique).
Your initial measurements showed a significant dip, then you provided updated measurements taken after you removed some stuffing. The change in the frequency response is significant. In post 28 of this thread, the entire path length of the horn is lined with what appears to be polyester batting. Where did you remove the stuffing from to cause the changes in frequency response?
Thanks.
geitmans said:I didn't try any high power into It. Its now just connected to my 70W receiver. Even with this it makes more than enough noise, on low frequencies even enough airflow
I'm not able to do an absolute spl measurement right now as I have no real reference.
I'd love to know what this thing does with some decent power.
When you do a sweep with your 70w receiver cranked, whats your SPL meter read?
Thanks for the photo, that helps. I only stuffed the throat of the sub that I built, fortunately I was pleased with the results. I had to be - I sealed it up tight and left myself no way to change it.
If it were me, I'd probably leave the throat area and remove the fill from the mouth side. I'm sure that others may have different feedback for you though.
Thanks again for documenting and sharing your project.
If it were me, I'd probably leave the throat area and remove the fill from the mouth side. I'm sure that others may have different feedback for you though.
Thanks again for documenting and sharing your project.
Today I did some more listening. This thing is surely impressive, it can shake concrete foundations. I also a managed a more detailled distortion maisurement. It was done with a WM-61 modified according to Linkwitz I don't know how accurate the microphone is but it should be ok.
I will try to experiment some more with the stuffing to remove the big null around 140Hz
I will try to experiment some more with the stuffing to remove the big null around 140Hz
Hi geitmans,
thanks for your reply. But what I do not understand is how you changed the bating (shown in post 47) in order to get the response shown in post 51? Or was the dip @60Hz caused by room effects (as mentioned in post 36) which was cured by modifying the TH's position in the room?
Happy easter.
Erik
thanks for your reply. But what I do not understand is how you changed the bating (shown in post 47) in order to get the response shown in post 51? Or was the dip @60Hz caused by room effects (as mentioned in post 36) which was cured by modifying the TH's position in the room?
Happy easter.
Erik
I don't think stuffing had much (if anything) to do with the big null at 60 hz. At least in my own testing, stuffing (and overstuffing) brought the big peaks down a bit but didn't do much (if anything) to fill in my big null (mine is at 80 hz, but still directly below the first big problem peak). OTOH, moving the mic around seemed to have a much more profound effect. Putting the mic in the mouth gives a smooth response that matches the hornresp predictions quite well, but putting the mic far away and off axis would make the dip up to 20 db deeper. If the mic or horn is moved even a few inches between measurements it gets hard to compare susequent measurements accurately to each other.
OTOH, maybe I'm completely wrong (which is not unusual) but I've NEVER seen stuffing fill in a big null like that unless you overstuff so severely it brings everything down to the level of the null.
OTOH, maybe I'm completely wrong (which is not unusual) but I've NEVER seen stuffing fill in a big null like that unless you overstuff so severely it brings everything down to the level of the null.
Happy Easter everyone
All my measurements were done with the speaker and mic in an identical position. The speaker is positioned with the mouth upwards in the middel of the room (like in the picture in post #28). The mic is positioned in the middle of the mouth. I first thought the dip might be caused by a room effect, but now I saw it was caused by the horn itself. I don't think room effects can cause such a large effect as this is somewhat a nearfield measurement.
Since post #47 I removed some more stuffing in the mouth area. The dip in the 60 Hz region is still there but is a lot less severe.
Also notice post #51 has a 100 dB range to see the harmonics, the other graphs have a 50 dB range.
The stuffing clearly influnces the tuning of the horn. This is also proven by the impedance plots which clearly show a shift of the impedance minima and peaks.
All my measurements were done with the speaker and mic in an identical position. The speaker is positioned with the mouth upwards in the middel of the room (like in the picture in post #28). The mic is positioned in the middle of the mouth. I first thought the dip might be caused by a room effect, but now I saw it was caused by the horn itself. I don't think room effects can cause such a large effect as this is somewhat a nearfield measurement.
Since post #47 I removed some more stuffing in the mouth area. The dip in the 60 Hz region is still there but is a lot less severe.
Also notice post #51 has a 100 dB range to see the harmonics, the other graphs have a 50 dB range.
The stuffing clearly influnces the tuning of the horn. This is also proven by the impedance plots which clearly show a shift of the impedance minima and peaks.
any updates available on the stuffing situation? I for one really appreciate all the time you've put into this, thanks for documenting your efforts.- Status
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