Dang Bill. That's awesome. For the record you did try to talk me out of it. But I feel like I must build it now. It will be interesting to see how the actual measurements compare to your sim. Looks like a tuning freq. around 25Hz? I was also thinking about making the top gasketed and removeable to adjust damping. I have heard that fiber damping is difficult to simulate its affects. It would make for a fun experiment, except for the size and weight and amount of material and questions from my wife, but other than that I think I will proceed with creating CNC toolpaths. I predict that the tuning will be closer to 20Hz maybe even lower, but that's OK with me. Excursion control. I like the way you figured that driver offset. All things must be considered. Thanks for the encouragement and your attempts at discouragement. You are better at the former than the latter.
What crossover frequency do you think you will be using? If you cross at about 60Hz or so, you will be able to actively choke off some of the nasty peaks and dips in the 100 to 300Hz area that are causing most of the problem in the unstuffed line. These peaks and dips are the most difficult to control with stuffing because of the longer wavelengths.
A 70 or 80Hz xover will also help somewhat to choke off the nasty peaks at 110Hz, 180Hz, 250Hz, 310Hz, etc., in the unstuffed model. The SPA250 uses a 24dB/octave low pass filter that can be adjusted from 40 to 180Hz. So, just to show the differences, I used David Ralph's Winfilters program to generate several LR 24dB/octave low pass filters at 60, 70, 80, 100, and 180Hz. Then I fed the FRD's into OmniMic to make some comparisons. At 110Hz, the 60Hz xover is -21dB; the 70Hz xover is -17dB; the 80Hz xover is -13dB; the 100Hz xover is -7dB, and the 180Hz xover is only -2dB.
Yeah, his designs are pretty legit. We used his weird array speaker for live sound and it worked surprisingly well. Not sure I would use it in my living because they are really ugly.
The TL subs also work really well, but IMHO ported subs are the way to go.
Very nice John. I must admit that I do not know much about the tapped horn. I do see some similarities to a transmission line, lots of overtones, so limited bandwidth, not a big deal for a sub
Comments
In case anyone is interested in how the model was set up, here is what the enclosure model looks like in the LA TL program:
And the impedance charts:
Dang Bill. That's awesome. For the record you did try to talk me out of it. But I feel like I must build it now. It will be interesting to see how the actual measurements compare to your sim. Looks like a tuning freq. around 25Hz? I was also thinking about making the top gasketed and removeable to adjust damping. I have heard that fiber damping is difficult to simulate its affects. It would make for a fun experiment, except for the size and weight and amount of material and questions from my wife, but other than that I think I will proceed with creating CNC toolpaths. I predict that the tuning will be closer to 20Hz maybe even lower, but that's OK with me. Excursion control. I like the way you figured that driver offset. All things must be considered. Thanks for the encouragement and your attempts at discouragement. You are better at the former than the latter.
Eggie - suggestion:
Leave the top-side of the TL open and place a 1/2" thick glass table-top on it with a gasket to seal it.
Now you have a visual aide/conversation piece that can be covered with a nice walnut top hidden under the couch to assuage the WAF.
What crossover frequency do you think you will be using? If you cross at about 60Hz or so, you will be able to actively choke off some of the nasty peaks and dips in the 100 to 300Hz area that are causing most of the problem in the unstuffed line. These peaks and dips are the most difficult to control with stuffing because of the longer wavelengths.
Originally I was thinking 80, then last night I thought 70 would be about the max for second order slope. We shall see.
A 70 or 80Hz xover will also help somewhat to choke off the nasty peaks at 110Hz, 180Hz, 250Hz, 310Hz, etc., in the unstuffed model. The SPA250 uses a 24dB/octave low pass filter that can be adjusted from 40 to 180Hz. So, just to show the differences, I used David Ralph's Winfilters program to generate several LR 24dB/octave low pass filters at 60, 70, 80, 100, and 180Hz. Then I fed the FRD's into OmniMic to make some comparisons. At 110Hz, the 60Hz xover is -21dB; the 70Hz xover is -17dB; the 80Hz xover is -13dB; the 100Hz xover is -7dB, and the 180Hz xover is only -2dB.
Here is a link to dlr's site in case you want to use the winfilter program: https://www.speakerdesign.net/
This, I even had a fold for this. I thought I gave Craig the plans too.
I am skeptical of the claims by Fitzmaurice's folded horn.
I never built one of his designs, but as far as I know, there were many happy peeps who did.
Yeah, his designs are pretty legit. We used his weird array speaker for live sound and it worked surprisingly well. Not sure I would use it in my living because they are really ugly.
The TL subs also work really well, but IMHO ported subs are the way to go.
Lab 12 horn fold attached.
Very nice John. I must admit that I do not know much about the tapped horn. I do see some similarities to a transmission line, lots of overtones, so limited bandwidth, not a big deal for a sub
Sucker is big though
Half wavelength?
550 centimeter length
Centipeders