choose the best loading for professional woofer

[zedda]

Hi !!

This is my first thread ever!!!

I want to expose a problem that I can not solve

I have this woofer

In BR Box this woofer have a bad response and is not ideal for low frequencies.
Furthermore, the BR loading (64 liters 45hz) created a phase inversion that is able to reach clipping any amp I try... in free air woofer does not create problems

certainly the volume of my box is not enough, but increasing the volume excursion reached critical levels, and the peaks of impedance approaching.

I will try to load it in transmission line or tapped horn.

in truth, I've already tried this woofer in a transmission line,long time ago, in a 40hz transmission line, and it work very good.
with 100 watt whole house vibrated
but this transmission line is old, have a big rear Room coupling, and I would to design a more lighter and more efficient box, but more tuned down.

Now I found a simulator (bullock and white's) for transmission line box,
I attached a photo of the simulation.
the line lenght is 2.36 meters, with 30°celsius of air temperature.
therefore the box is tuned to 37 hertz.

Unfortunately, I do not know use hornresp, and I would like to know how to simulate a simple box with a single folding (see the attached picture)

The latest photos are alternatives of the box that I want to build

What do you recommend?

thanks to all!!!!

 

[pacificblue]

The most promising approach will surely be to start fom the manufacturer's recommendation: 100 l tuned to 47 Hz.

Add a steep high-pass filter at or slightly below that frequency, as is proven practice in PA to avoid excursion and clipping issues.

 

[zedda]

thank you very much!!!!

I know the manufacter recommendation, but I can't understand how they can recommend a tuning so useless...
this woofers are for 2-way systems, and I don't understand how it is possible for them to put a box of 100 liters on a stand with a 1.4 inch big horn...
evidently the engineers at B&C are highly trained

I want to try to use them as a subwoofer.
with a 0.22 qts I can't get a good bass reflex...

for this I would like to try again the transmission line or the tapped horn

see you tomorrow!! I go to sleep

 

[sreten]

Hi,

Its not a sub, and can't be made into a sub. It does
what it does, goes really loud with no real deep bass,
in a compact vented box like all other PA drivers do.

Your understanding is useless, not the driver.

rgds, sreten.

 

[bear]

Geez, sreten, ur ******* HARSH!

Give the fellow a break, he says it's his first post. You slap babies too?

_-_-

 

[zedda]

Geez, sreten, ur ******* HARSH!

Give the fellow a break, he says it's his first post. You slap babies too?

_-_-

it's ok bear no worries.
sreten told me what he thinks.

I want to try to simulate this woofer in a tapped horn,
if the simulated response is decent then it means that both box (TH and TL) are good for my woofer

but I don't know how to use hornresp...
simulation of the transmission line is too good for me...

Woofer is very braked at low frequencies, maybe it is better the transmission line because it is less compressed

can someone explain to me how to simulate it?

thanks again to all

 

[zedda]

if I have a woofer with fs if 38hertz
I have to tune it to 38hertz x 0.707 ????
it is a rule?

 

[pacificblue]

if I have a woofer with fs if 38hertz
I have to tune it to 38hertz x 0.707 ????
it is a rule?

Says the same person who thinks

evidently the engineers at B&C are highly trained

Loudspeaker enclosure calculating with Thiele Small parameter

And yes, this driver will work in a TH. If you have enough space, you can reach 30 Hz @ -3dB. Just read the HornResp user's manual or the http://www.diyaudio.com/forums/subwoofers/119854-hornresp.html thread

 

[AndrewT]

post1, pic4
How close do the speaker driver and the port need to be to meet the specification of a tapped horn?

 

[zedda]

Says the same person who thinks



Loudspeaker enclosure calculating with Thiele Small parameter

And yes, this driver will work in a TH. If you have enough space, you can reach 30 Hz @ -3dB. Just read the HornResp user's manual or the http://www.diyaudio.com/forums/subwoofers/119854-hornresp.html thread

thanks for the reply

I'm certainly not well expressed
I wanted to know if it is a rule for TH to tuning at 0.707 x FS
I would prefer a tuning at 37 hertz not 26 hertz

I use them outdoors and the lightness and portability are required

 

[zedda]

post1, pic4
How close do the speaker driver and the port need to be to meet the specification of a tapped horn?

Hi AndrewT

the photo 4 represents a Transmission Line box
I think the tapped horn must have the basket of the driver inside at the duct exit

 

[AndrewT]

Hi AndrewT

the photo 4 represents a Transmission Line box
I think the tapped horn must have the basket of the driver inside at the duct exit

i.e. at S3
And L34 can be 0.1mm.
But how far away from S3 can the driver be to still behave as a TH?

The question still stands:

post1, pic4
How close do the speaker driver and the port need to be to meet the specification of a tapped horn?

 

[pacificblue]

I wanted to know if it is a rule for TH to tuning at 0.707 x FS

No, it is not a rule. Any box tuning is a compromise, and you decide which compromise to take. That formula leads to a good compromise between low f-3, high sensitivity, high max SPL and flat response.

If you don't need such a low f-3, but prefer a smaller box and/or higher SPL instead, tune it higher to your needs.

37 Hz outdoors is quite ambitious already even without considering box size and weight. With a single driver it could be advantageous to tune it even higher.

 

[pacificblue]

post1, pic4
How close do the speaker driver and the port need to be to meet the specification of a tapped horn?

Designer's decision. There is no specification for that particular distance. It is usually determined by the driver dimensions and how you can make the horn contour fit into the box.

 

[AndrewT]

Could you show the input screens for a Transmission line where the driver is VERY close to the port and for a TH where L34 is almost zero?

 

[zedda]

No, it is not a rule. Any box tuning is a compromise, and you decide which compromise to take. That formula leads to a good compromise between low f-3, high sensitivity, high max SPL and flat response.

If you don't need such a low f-3, but prefer a smaller box and/or higher SPL instead, tune it higher to your needs.

37 Hz outdoors is quite ambitious already even without considering box size and weight. With a single driver it could be advantageous to tune it even higher.

thank you!

ok! the box tuning is my choice

I have two driver 15ndl76, and
I think placing them horizontally in series

is more sensitive TH or TL at the same tuning frequencies??
the TH should be more compressed and more controlled, but sensitive??

for AndrewT
I think that the transmission line simulator(bullock and white's) does not allow you to manage the proximity to the woofer from port
while I don't know how to use hornresp.

 

[zedda]

Hi
I'm trying to simulate the tapped horn but I can't

however, investigating some type of TH and Tlines, I discovered these things:

I think the tuning frequencies (and low) the air velocity become important, and for a good sensitivity is important to not slow down too much the velocity with curves or with compression ratios too high
a divergent duct reduce air velocity and let down the tuning frequencies

I want to raise as much as possible the sensitivity at low frequencies
the lower compression of Tline could increase too much the excursion under the tuning frequency

I noticed that if I tuning the line to 35hz I have a loss of efficiency at 50Hertz
as can be solve?

 

[freddi]

I drafted a reply a couple of days ago but could not remember the title of the thread

ask some of the guys who know how to do TH and tapped - tqwt and they likely will come up with something better than my simple example.

7.4 cubic foot inverted tapped horn/transflex-type test pipe from 1 sheet of plywood - YouTube

simple tapered 1/4 wave tapped tube made from one sheet of plywood
Ang=2.0 x Pi
Eg=31.62
Rg=0.10
Fta=0.00
S1=1096.00
S2=890.00
Par=21.00
F12=0.00
S2=890.00
S3=419.00
Par=200.00
F23=0.00
S3=419.00
S4=419.00
Par=0.01
F34=0.00
S4=0.00
S5=0.00
L45=0.00
F45=0.00
Sd=855.00
Bl=17.77
Cms=1.73E-04
Rms=5.90
Mmd=87.02
Le=1.50
Re=3.10
TH=1
Vrc=0.00
Lrc=0.00
Ap1=0.00
Lpt=0.00
Vtc=0.00
Atc=0.00
Pmax=200
Xmax=14.0
Path=0.0
Fr1=0.00
Fr2=0.00
Fr3=0.00
Fr4=0.00
Tal1=100
Tal2=100
Tal3=100
Tal4=100
Comment=15NDL76-4 in my tapped pipe

 

[zedda]

wow!!! thank you very much freddi

the impedance is very perfect, the first peak is bigger but at 18 hertz, therefore doesn't create problems...
the second peak is lower... appears to be a very easy load
also the excursion is more controlled...

if I don't ask too much, how are the external dimensions of the cabinet?
the value of spl is a little low but not bad...

 

[freddi]

those figures aren't real bad for half space - its 15.5" deep by 17.75" wide by 48" tall. Ask some of the guys real good with hornresp in the subwoofer forum to model some tapped horns and tapped TQWT-s for that B&C - if you already own then might put it to use - it looks like a high fidelity unit as a direct radiator.

here's an old thread at Speakerplans where I got the idea for the pipe and the aperture - look at the simulations - they should help you get an idea on how to use hornresp for this case.


http://forum.speakerplans.com/plan-d20-hz-macro-sub-tapped-horn-by-moi_topic24838.html