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Multi-Way Conventional loudspeakers with crossovers

tqwtl predictions
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Old 2nd August 2017, 11:06 PM   #11
pkitt is offline pkitt  United States
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If the Qts of the TD10M was around 0.40, then using a line with a 1/4-wavelength resonant frequency of 40 Hz would likely result in an overall response shape that is flat from the knee in the curve on up. However, the published Qts of this driver is 0.24, and a 1/4-wavelength resonant frequency much higher than 40 Hz would be needed for an overall flat response shape.

Once you've determined the optimum 1/4-wave resonant frequency for a specific driver, the bass response (f3, for instance) will be dependent primarily on the volume in the line.

The speed of sound is minutely affected by stuffing, a misconception from long ago. Stuffing densities commonly used in TL designs range from 0.25 to 1.0 lb/ft3 (for polyester fiber). Virtually all stuffing materials perform the same job the same way, differing only in stuffing density necessary to achieve a desired result.
Paul
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Old 3rd August 2017, 08:36 PM   #12
lbstyling is offline lbstyling  United Kingdom
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I was under the impression fiberglass was a better material for stuffing. Something about it reducing harmonics to lower frequencies than polyester.

Is the only way to determine the ideal horn length for this driver by simulation trial and error then?
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Old 3rd August 2017, 08:49 PM   #13
planet10 is online now planet10  Canada
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Originally Posted by lbstyling View Post
I don't know the effect of adding fiberglass or other fill on the speed of sound.
Little to none.

HornResp now lets you add damping, this will help get rid of the ripple.

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Old 3rd August 2017, 10:13 PM   #14
pkitt is offline pkitt  United States
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Fiberglass is "better" only in that it takes a lower stuffing density to achieve the same effects as polyester fiber. For instance, a stuffing density of ~0.7 lbs/ft3 of fiberglass gives the same results as a stuffing density of 1.0 lb/ft3 of polyester fiber.
Paul

Quote:
Originally Posted by lbstyling View Post
I was under the impression fiberglass was a better material for stuffing. Something about it reducing harmonics to lower frequencies than polyester.

Is the only way to determine the ideal horn length for this driver by simulation trial and error then?
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Old 8th August 2017, 07:12 PM   #15
lbstyling is offline lbstyling  United Kingdom
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Quote:
Originally Posted by pkitt View Post
Fiberglass is "better" only in that it takes a lower stuffing density to achieve the same effects as polyester fiber. For instance, a stuffing density of ~0.7 lbs/ft3 of fiberglass gives the same results as a stuffing density of 1.0 lb/ft3 of polyester fiber.
Paul
That clears that up then, thanks

Here is a Sketchup drawing of a possible cabinet for the speaker.

khyFH5l.jpg

dYuTEgh.jpg

Its a JMLC 350 horn, about 600mm wide. The compression driver is currently a JBL 2452, but may change for a D2 at a later point.

What do you think?

The TD10M cabinet is 1000mm tall in this drawing

When putting a fold in the horn, how do you measure the length? Do you calculate it as the shortest route, or as the average distance from one end to the other?
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Old 8th August 2017, 08:00 PM   #16
planet10 is online now planet10  Canada
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Originally Posted by lbstyling View Post
Here is a Sketchup drawing of a possible cabinet for the speaker.
The TQWTL looks to be too small. And having a cabinet edge inside that close to the driver is a receipe for early reflection and unwanted cupped sound particularily in voices.

dave
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Old 8th August 2017, 10:13 PM   #17
lbstyling is offline lbstyling  United Kingdom
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Originally Posted by planet10 View Post
having a cabinet edge inside that close to the driver is a receipe for early reflection and unwanted cupped sound particularily in voices.

dave
Hi Planet,

When you say the cabinet edge is too close to the driver, do you mean inside the cabinet? as in the sonotube is too close to the diameter of the driver?

externally, the speaker has a 3/4 inch round over all around the driver.

Quote:
The TQWTL looks to be too small.
On hornsrep, my best simulation gives S1=259, and S4 = 90. I took this to mean 259cm2?
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Old 8th August 2017, 10:16 PM   #18
planet10 is online now planet10  Canada
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Originally Posted by lbstyling View Post
When you say the cabinet edge is too close to the driver, do you mean inside the cabinet? as in the sonotube is too close to the diameter of the driver?\
Yes the inside/ With a driver this size i'd want at least 50mm each side.

dave
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Old 8th August 2017, 10:38 PM   #19
lbstyling is offline lbstyling  United Kingdom
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47MjyKW.jpg

Thats an extra 25mm each side. There is a compromise aesthetically here for me for going much bigger. I'm hoping that using a 3/4 inch round over bit on the inside of the baffle, and filling in the inside of cabinet where the baffle meets the sono tube in order to smooth the airflow further may help.

I know exactly what you mean about 'cupping'. This was the sound I could hear when listening to the KEF R500s on demo last week (for fun, as I had been reading about just how well that KEF co axle driver measures)

I assumed this was due to the tweeter being mounted in the mid driver.

Is it still noticeable when only playing up to 500-700 hz?
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Old 8th August 2017, 10:52 PM   #20
planet10 is online now planet10  Canada
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Quote:
Originally Posted by lbstyling View Post
There is a compromise aesthetically here for me for going much bigger.
Not going bigger will ompromise the sound, and i doubt you can fit a proper TL into that box.
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Is it still noticeable when only playing up to 500-700 hz?
Yes. Voice fundementals ar ein that range or below (male bass fundemental on the order of 80 Hz)

dave
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