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Old 8th August 2017, 11:26 PM   #21
GM is offline GM  United States
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Quote:
Originally Posted by lbstyling View Post
Thanks GM,

Your model requires a 59L box, which is possible, but I'm looking for a cabinet that is roughly 110cm x 20cm x 30cm maximum external dimensions, giving me about 40L to play with.

The question is,
1) How accurate is Hornsrep?
2) If a satisfactory response is simulated, are there any other real world factors to be considered? I have heard:
3) Is Hornsrep only simulating the horn response or the horn and the drivers rear radiation, or is it the front as well? The response drops down as the frequency increases above 400hz in my simulations, this is obviously a problem if it includes sound output from the front.

I have heard several rules for making a horn, but I don't know how true they are?

1) That the horn length must be 1/3 of the Fs of the driver
2) The areas of each end of the horn must add up to the length of the horn (approximately)
3) The driver must tap at 1/3 of the way down the horn for a flatter response.

Basically, is this actually going to work? And is it a good idea?
You're welcome!

1] Plenty close enough when used correctly.

2] Yes, like can one build it in the desired space, etc..

3] It shows both horn and driver, though only up to a certain point where either the horn rolls it off or where the driver's no longer a point source. It's academic though for a tapped alignment as the phase response limits the XO point to at/just above the tap point or ~250 Hz at most according to HR. For a higher XO point you'll need a regular TQWT.

1] Never been exposed to this rule-of-thumb and makes no sense to me as presented, but a horn has to be a 1/2 WL long to properly load, though doesn't have to be to Fs unless that's the design goal.

2] This makes no sense to me either as presented, but the throat area [St] is a function of the horn's desired HF response and the mouth area [Sm] plus any local boundary loading sets how low it will load.

3] Well, it needs to be at an acoustically odd harmonic, so typically 1/5th, 1/3rd, 2/5ths, though due to the flare factor [T or M depending on the source] and frequency ['x' Hz pipe fundamental] these points are physically a little bit lower in reality, but for most folks just dividing by the fractions is plenty close enough.

Yes and mostly no as I'm not sure if you understand how hard this will be to accurately fold up and will probably have some dead space that will need filling to keep from resonating; whereas mine will be much easier with just plain boards and if it can't be made to fit the space, then use the wizard to make it smaller, but do keep the driver at the 13.94 cm point at each end.

Regardless, you didn't respond to whether or not you want a TTQWT or regular TQWT, but judging by your Sketch, you want a regular one, so your sim is no good as is or even if you change the driver type from [TH] to [OD], though if you change mine you'll have a good one to start with.

GM
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Old 8th August 2017, 11:41 PM   #22
lbstyling is offline lbstyling  United Kingdom
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Originally Posted by planet10 View Post
Not going bigger will compromise the sound, and i doubt you can fit a proper TL into that box.

dave
I am willing to accept efficiency loss from a TL cabinet format at the bottom end (below 80hz) as a sub will be used, and EQ will also be available. I would like the speaker to sound reasonable without the sub turned on though.

I don't seam to get significantly more bottom end even when increasing the size of s1 to s4 by a factor of 2 or more, mostly efficiency.
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Old 9th August 2017, 12:48 AM   #23
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Originally Posted by lbstyling View Post
I am willing to accept efficiency loss from a TL cabinet format at the bottom
Then what is the point of doing a TL?

dave
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Old 9th August 2017, 05:08 AM   #24
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whereas mine will be much easier with just plain boards and if it can't be made to fit the space, then use the wizard to make it smaller, but do keep the driver at the 13.94 cm point at each end.
FWIW, I shrunk a TQWT [no tap] version of mine to ~37.5 L and with a stuffing adjustment it appears to meet your needs.

GM
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File Type: txt TD10M40hzTQWT.txt (973 Bytes, 7 views)
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Old 9th August 2017, 05:10 AM   #25
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Originally Posted by planet10 View Post
Then what is the point of doing a TL?

dave
Yeah, a MLTL would be plenty sufficient.

GM
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Old 9th August 2017, 06:25 PM   #26
lbstyling is offline lbstyling  United Kingdom
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Originally Posted by planet10 View Post
Then what is the point of doing a TL?

dave
The reason for doing a TL is subjectively, I find them to sound good, and I can't help but think that standard ported enclosures must colour the sound as they keep most of the back-wave from the driver in. I have no measurements to support that this is audible, but I just can't see how large proportions of the sound doesn't bounce around inside the enclosure and simply emerge back into the room by passing back through the speaker diaphragm at a later interval.

Damping of course will help convert some of this into heat, but it just doesn't seem right to me. The more efficient the cabinet design makes the speaker, the less energy will be kicking around in the cabinet I suppose. On top of this, the larger the cabinet in proportion to the driver, the more area to absorb the backwave.

Last edited by lbstyling; 9th August 2017 at 06:35 PM.
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Old 9th August 2017, 07:06 PM   #27
lbstyling is offline lbstyling  United Kingdom
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Quote:
3] It shows both horn and driver, though only up to a certain point where either the horn rolls it off or where the driver's no longer a point source. It's academic though for a tapped alignment as the phase response limits the XO point to at/just above the tap point or ~250 Hz at most according to HR. For a higher XO point you'll need a regular TQWT.
I was not aware of the max frequency limitations of a TH. Simulations all show the output dropping at higher frequencies, hence my question. This explains it. thanks!
Quote:
2] This makes no sense to me either as presented, but the throat area [St] is a function of the horn's desired HF response and the mouth area [Sm] plus any local boundary loading sets how low it will load.
I definitely read somewhere that the compression ratio (ratio of s1 to s4 should ideally be kept to circa 3:1. I was assuming this was to do with air velocity in the same way as port noise becomes a problem with a undersized port, or with pressure on the driver diaphragm itself from the back-wave.
Quote:
I'm not sure if you understand how hard this will be to accurately fold up and will probably have some dead space that will need filling to keep from resonating; whereas mine will be much easier with just plain boards and if it can't be made to fit the space, then use the wizard to make it smaller, but do keep the driver at the 13.94 cm point at each end.
I was going on the premise that if the horn angle was constant, (link s1 to s4) that a single fold would be needed, and as the angle doesn't change, this would be easy (1 piece of wood down the middle) I can accept a moderate increase in the depth of the cabinet if necessary.
Quote:
Regardless, you didn't respond to whether or not you want a TTQWT or regular TQWT, but judging by your Sketch, you want a regular one, so your sim is no good as is or even if you change the driver type from [TH] to [OD], though if you change mine you'll have a good one to start with.
Considering your earlier point about using a TH only up to about 250hz, I will need to use this driver up to circa 500-700hz crossover (JMLC 350hz horn above) So I would need a TL or MLTL then. I am unsure of the advantages/disadvantages of a MLTL though to be honest.

One of the reasons I chose the TD10M is because I wish to have the option to change over the tweeter for various alternatives, so wanted a driver that could play higher if needed.

I appreciate the major drawback to the design is the distance between the tweeter and the bass driver, but this is partly why the design has the TD10M at the top of the cabinet, so I could swap out the horn for alternatives at a later date and see if I felt decreasing the C to C distance to the tweeter was worth the trade off of loosing that up front presentation of a horn.

While I am talking about it, I assume there is no alternative layout I have missed that would reduce the c to c distance without significant drawbacks? (cant look ugly though). I thought about angling the driver back, so the magnet is much closer to the tweeter, but this just seams to cause complications with reflective surfaces in front of the driver.

I could move the driver so the magnet is very close to the tweeter magnet, and put a mini horn mouth on the front of the driver as well, but I have no idea how to simulate this, and it would probably have awful off axis behaviour unless the cabinet was very wide.
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Old 10th August 2017, 09:19 PM   #28
lbstyling is offline lbstyling  United Kingdom
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can I model a MLTL in hornresp?
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Old 10th August 2017, 11:40 PM   #29
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Good enough, but the vent has to be inputted at the bottom, though the sim calculates it as both the driver and vent is the same distance from the listening position [LP], which adds a notch in the response.

To view the response with it shifted up at an odd harmonic where some of us like to put them to deal with the notch, then you have to put in the angular offset using the OUTPUT/HORN/COMBINED in the TOOLS menu.

Attached for reference:

GM
Attached Files
File Type: txt 25GDN-5_MLTL.txt (965 Bytes, 2 views)
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Old 12th April 2018, 08:47 PM   #30
lbstyling is offline lbstyling  United Kingdom
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Hi all,

So this design has developed into a 3 way with a JBL 2206 as the bass driver, and the TD10M moved to mid range duty.

I plan to keep the form factor (shown on the previous page) but make the tube in the middle sealed.

The 2206 will be placed side facing in the bottom cabinet, and will likely be just ported as per JBL's recommendations as it only needs about 50L

I would like to run the mid driver down to about 200hz or so. I hope this is low enough to not become an issue with beaming/directivity.

The idea is to keep the distortion low for the mid by offloading the higher excursion needs of bass to the 2206h.

I don't know where the crossover frequency will be, but as it will be digital active, this shouldn't be too much of a problem.

Aesthetically, I don't want the edge around the mid driver to be too thick as per Planet10 suggests in post 18. I will if I need too though. Can anyone provide any evidence to support Planet10s suggestion that having the box too close to the size of the driver is detrimental to the sound? And how close can I go?
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