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Old 23rd May 2011, 08:27 PM   #1
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Default Using the Marchand frequency generator

I have used the free Marchand frequency generator a while back but I need the directions again.

I recall that varying the frequency would get a lot of air out the port. I moved the same FE167e speaker to a smaller box and do not feel that air pressure at the port opening now. The Port is the Fostex recommended 2 in x 2 in. in a box with internal dimensions 7 5/8 in w., 4 3/8 in d., 22 1/2 in tall.

Is there a different calculator for port dimensions based on T/S params *not* WinISD? I want to port a different speaker from a Roland piano salvage. The Rolands were on deal as full range remainders on Ebay a few years ago.
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Old 24th May 2011, 12:23 PM   #2
IG81 is offline IG81  Canada
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Hi Lon,

IMHO the Roland has too high a Qts to work in a vented alignement; it might fare better in an open or infinite baffle, or aperiodic (maybe still too high for this last one).

As for port dimensions, I like to use Hornresp to simulate vented enclosures; it's quite a versatile little program.

IG
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Old 24th May 2011, 03:22 PM   #3
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Yes open baffle has been recommended for this speaker before. Recently I screwed it to a board 2 x 2 feet. The sound, simply put, was awful. No OB wings or other attachments but I didn't think it was successful.

I have not used Hornresp and am pretty feeble and incompetent doing calculations.

The Roland (actually a speaker put into Roland electric pianos) is happy in a sealed box, and stock with no cone treatments. At least it doesn't sound bad if not perfect.

I may use the 7.5 cutout from the OB cut down to try a Karlson at some point for a different driver but that is some time off.
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Old 24th May 2011, 03:48 PM   #4
IG81 is offline IG81  Canada
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As a MI driver, it likely has some deliberate coloration of the sound. This might be pleasant or not used for music, subjectively. I found these specs you posted for you drivers:

Fs = 78.76 hz
Vas = 24.5 L/0.8652 cu ft
Re = 7.309
Le = .2462 mh
Qms = 5.772
Qes = 1.977
Qts = 1.473
Sd = 21.4 sq cm/3.317 sq in
BL = 0.4477 N/A (calc'd)
Spl 89.65 1w/1m
Pe = 30W

With such an Fs and 2'x2' baffle, and perhaps even on much larger baffles, they won't ever produce much bass, or even midbass, thus probably resulting in the awful sound you describe. Luckily they don't have too huge a Vas, so maybe aperiodic boxes could be the ticket here? (in addition to you finding them happy in a sealed box).

IIRC the Karlson you build is K8? If putting the Roland in there, stuff the backchamber nicely with polyfill or equivalent and maybe even damp the vent. I'd venture a guess that they would do better in K12-size kouplers though.

IG
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Old 24th May 2011, 05:07 PM   #5
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Yes I still follow the Karlson discussions and was going to try one of the larger ones. The K8 was not satisfactory. And the question I had for the Karlson group (don't remember if I asked this in mail to someone or posted) is this: some of the old Karlson ads show the cabinet lying on its back. What was the philosophy of doing that? I can add this to the Karlson discussion as well.
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Old 24th May 2011, 06:21 PM   #6
IG81 is offline IG81  Canada
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Quote:
Originally Posted by loninappleton View Post
Yes I still follow the Karlson discussions and was going to try one of the larger ones. The K8 was not satisfactory. And the question I had for the Karlson group (don't remember if I asked this in mail to someone or posted) is this: some of the old Karlson ads show the cabinet lying on its back. What was the philosophy of doing that? I can add this to the Karlson discussion as well.
Yeah, the add with the lady putting her drink on the tabletop placed over the lying down koupler.

This is the 1st (1954) K12, dubbed "Karlsonette", two of which I have built. They advised lying the koupler on it's back, narrow end of the slot towards the wall, so as to have the driver firing up, towards the wall and accordingly give some diffusive effect. I did not try it with my koupler and doubt I would much care for it. I find strange that they placed a, somewhat spaced, tabletop over it though.

Drivers with high motor strenght, low Qts and low moving mass are advised for Karlson and have been reported to work well in kouplers of their nominal sizes. In my case, with the Karlsonette (K12), I've had luck with mid-Qts drivers (0.45-0.55) of smaller size than nominal koupler size, namely 8" and 10". Hard to tell how a driver such as the Roland with very high Qts will do.

IG
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Old 24th May 2011, 07:58 PM   #7
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Ok, thanks for answering. I think "poorly" is the best the Roland will do in these given all the advice so far. It's just my attempt to squeeze some usage out of what I have and keep building. :-)
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Old 24th May 2011, 08:39 PM   #8
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You might try a little bigger baffle....Say 3' wide x 5' high
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Old 25th May 2011, 01:22 AM   #9
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Erf, I am out of wood. I'll leave the big panels to others.

So with the Marchand prog the only thing I remember is when you can't hear the frequency, that's it-- you at the lowest the Speak will go.

I will have to get serious about Hornresp.

Also, about the time I wanted to get a fresh speaker of either Mark Audio or Fostex 126en, they are all out at Madisound.
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