Built an MLTL and am testing. Haven't done ground plane measurements yet, later this week perhaps. These levels are not for a given power but just the difference between low level and high level. Should I normalize the response reducing peaks to a level of ~105dB (while leaving the nulls alone)?
Comments, questions?
Comments, questions?
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Design details? Looks like it needs a bit more damping, though it's more about how smooth they sound without sounding bland Vs how they measure.
GM
GM
It's an MLTL with added tapped twist to the design. Line length is 76" for the MLTL and then an additional 44" length external to that enclosure for the tap. Vb of the mltl is ~27³ L, single 2.48" ID port 3.75" long external to that enclosure with a 3"ID precision port flare for end correction, driven with a single 6.5" woofer. Fb of the MLTL is ~31Hz.
The impedance and nearfield driver/port measurements I mentioned the other day when discussing dampening materials are from the MLTL. In this tuning I used bjorno's Ikea polyfill suggestion and then added the tap after imp. measurement. Wife was home and couldn't do more. Today is another story and in about 30 minutes or so can get back to measurements and tweaks 😉
Room has many issues, poor construction to start with, then a hallway and a kitchen that act as bass traps. Sliding patio doors right behind the sub about a foot back. Driven from approx mid wall width and mid room height.
This is an experiment, not an actual sub used for something. Simply having fun with theory at this point. There is no dampening in the tap section yet if it can be called a tap. The external enclosure is to place the port and the driver at the same exit point balancing the wavefronts.
The impedance and nearfield driver/port measurements I mentioned the other day when discussing dampening materials are from the MLTL. In this tuning I used bjorno's Ikea polyfill suggestion and then added the tap after imp. measurement. Wife was home and couldn't do more. Today is another story and in about 30 minutes or so can get back to measurements and tweaks 😉
Room has many issues, poor construction to start with, then a hallway and a kitchen that act as bass traps. Sliding patio doors right behind the sub about a foot back. Driven from approx mid wall width and mid room height.
This is an experiment, not an actual sub used for something. Simply having fun with theory at this point. There is no dampening in the tap section yet if it can be called a tap. The external enclosure is to place the port and the driver at the same exit point balancing the wavefronts.
Ran another slow sweep, measuring from mid room (worst case senerio) noting room peaks and nulls. Room peaks at 50&80 with a strong nulls @ 33, 70 and 90. Another @118Hz I'm not sure of cause but believe to be interaction of the external enclosure and second harmonic of the mltl and ~164 which is the mltl enclosure itself (third harmonic).
Here is a comparison with out tap in violet and with in blue. Need more across the room as it has a very smooth distribution with the tap. Without the tap the room is loaded from two distinct points depending on orientation due to it's 45" length and the distance to the port of ~40.5".
In this configuration it was found best to lift it up so that the driver and port were equidistant from the floor ceiling boundary. Port up, driver down firing. Off the top of my head that's ~23" if memory serves me correct.
Multisub placement built in, but damn that's tall, 5'8" x 8.25" diameter! 🙄
In this configuration it was found best to lift it up so that the driver and port were equidistant from the floor ceiling boundary. Port up, driver down firing. Off the top of my head that's ~23" if memory serves me correct.
Multisub placement built in, but damn that's tall, 5'8" x 8.25" diameter! 🙄
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Having built tube subs 30years ago can say this. It is a thin wall ~0.125" (~3.2mm) paper board that is not suitable for upper frequency use due to the low dampening and transparency. With that said, if bandwidth limited, works fine <150ish. Yet at the same time bass transients pass through with a bite if the music demands it, fast, very good depth and punch which is probably due to the material transparency in the upper octaves.
Casting sand vinyl mix between the outer diameter of this and another, next size up being 8.5"ID leaves a 0.125" gap, would make a good constrained layer design cheap enough.
Casting sand vinyl mix between the outer diameter of this and another, next size up being 8.5"ID leaves a 0.125" gap, would make a good constrained layer design cheap enough.
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