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Old 8th January 2006, 05:55 PM   #31
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Quote:
Originally posted by Vikash
40.5 and 45mm ports to hand. Both are 121.5mm long.
123mm is what the calc says... so your port is close enuff.

dave
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Old 9th January 2006, 12:46 AM   #32
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Quote:
Originally posted by Landroval
However with HobbyHifi's measured T/S I'm getting a +5dB peak at 70Hz with 55Hz tuning.
Umm, guys, any comments on this?
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Old 9th January 2006, 01:42 AM   #33
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Quote:
Originally posted by Landroval


Umm, guys, any comments on this?
Well, I am in the process of building a bipole MLTL, for which I had used the CSS T/S parameters to model in MJK's mathcad sheets. The FR graph from that one looks like:
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Old 9th January 2006, 01:47 AM   #34
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And I found that if I just lengthened the port from 2.5" to 3.5" and reduced its diameter from 2" to 1.5" when using the T/S parameters from Hobby Hifi, I could get this with the same box:
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Old 9th January 2006, 02:03 AM   #35
maxro is offline maxro  Canada
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So, I suppose, if your box is large enough, the higher Vas won't be too much of an issue. You'll just have to tune the port lower to match the lower Fs to get rid of the hump.

That is supposing the Hobby Hifi specs are correct.

My box, by the way, is a folded, mass-loaded Voight of sorts. Kind of unusual in that the drivers are near the large end (top) and the port (firing at the floor) is halfway along the line, at the fold.

L=69.5"
Zdriver=4"
Zport=35"
So=56.16sq"
Sl=2.5sq"
density 3.5lb/cuft
Rport=1"
Lport=2.5"

I'll report back when I finally get these things done. Hopefully this week some time.

Max
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Old 9th January 2006, 11:05 AM   #36
Vikash is offline Vikash  United Kingdom
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Quote:
Originally posted by Landroval


Umm, guys, any comments on this?
This may be of interest. Also read Dan Wiggins' post further down in that thread.

I may just make a mock carboard cabinet tuned to 54Hz and see what the measured FR is.
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Old 9th January 2006, 01:11 PM   #37
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Quote:
Originally posted by Vikash

This may be of interest. Also read Dan Wiggins' post further down in that thread.

I may just make a mock carboard cabinet tuned to 54Hz and see what the measured FR is.

...further down in that thread I had posted the HobbyHifi and Klang+Ton TSPs

Both are very well respected DIY mags here in Germany, but...
I have the FR125Ss playing in a 12L sealed cabinet, I can't measure them, but I doubt that the f3 is somewhere between 50 and 55 Hz (see the simulation below), from what I'm hearing the f3 is more like in the 70 - 80 Hz area.

I will start experimenting with ports for the 12L enclosure in the next days.
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Old 9th January 2006, 02:04 PM   #38
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Default Enclosures and Notch

Hi,

I made some measurements on Saturday with a customers reflex cab. So far: 14 liters or 0.5 cu.ft reflex was great (with a 2" port, 4" long).

Notch 1: 0.39mh / 44uF (2x 22) / 12 ohms --> this is for the 1500Hz region

Notch 2: 0.1mh / 4.7uF --> this is for the 7000Hz peak

Now the curve looks good within +/- 2 or 3dB

Regards
Thorsten

P.S. We used the measured parameters of German DIY magazines "HobbyHifi" and "Klang+Ton" (intersection of both results)
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Old 9th January 2006, 02:10 PM   #39
Vikash is offline Vikash  United Kingdom
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Thanks for the filter info. This is the kinda stuff I was initially looking for. Do you have the FR graph at all? It would make it easier to see which T/S params are closer.
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Old 9th January 2006, 02:53 PM   #40
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Default Tsp

To get the plot out of my measurement prog will take a while. Here are the TSP of "Hobby Hifi" (Klang + Ton was very close):

FR125S
Fs: 44,8 Hz
Qms: 3,6
Qes: 0,66
Qts: 0,56
Vas: 8,7 L
Cms: 2,4 mm/N
Rms: 0,41 kg/s
Sd: 50 qcm
Xmax: 6mm
Re: 7,1 Ohms
Le: 0,39 mH
BL: 4 N/A
Mms: 5,3 grams

WR125S
Fs: 59,8 Hz
Qms: 5,7
Qes: 0,96
Qts: 0,62
Cms: 1,6 mm/N
Rms: 0,29 kg/s
Vas: 5,8L
Sd: 50 qcm
Xmax: 6mm
Re: 7,2 Ohms
Le: 0,71 mH
BL: 4,1 N/A
Mms: 4,4grams

WR125ST
Fs: 67,8 Hz
Qms: 5,7
Qes: 0,89
Qts: 0,77
Vas: 4,4 L
Cms: 1,3 mm/N
Rms: 0,31 kg/s
Sd: 50 qcm
Xmax: 6mm
Re: 16,2 Ohms
Le: 1,22 mH
BL: 5,7 N/A
Mms: 4,2 grams

I can't scan the whole article due to copyright laws, sorry!

Regards
Thorsten
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