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Multi-Way Conventional loudspeakers with crossovers

Open Source "Tower XL"
Open Source "Tower XL"
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Old 27th June 2019, 05:09 PM   #861
Paul Vancluysen is offline Paul Vancluysen  Belgium
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Quote:
Originally Posted by Aatto View Post
some updates on the design.
I added the IHA as suggested, the mid chamber is about 13 liters and the IHA is about 23 with the 18cm cutout on the back wall of the IHA and HF Driver+Horn will fit nicely there as well.
IMO, this looks a very good concept, good size and shape for the midrange part, and some extra volume for the woofer. Some tests can be done using a IHA. If not successful, it isn't lost space.
Maybe adding an extra vertical bracing in the woofer part, behind the driver? That should make the cabinet extra solid.
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Old 27th June 2019, 08:04 PM   #862
Juhazi is offline Juhazi  Finland
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The IHA might make a resonant chamber, but high f?
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Old 27th June 2019, 08:40 PM   #863
Roundtoit is offline Roundtoit  United States
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I am looking forward to test results of this incarnation. There is a refined and simple elegance achieved here which I hope delivers from theory to good test facts. This will be a great build.

1.) I'm out of my element here and trying to learn...I do grasp bass reflex port resonance and helmholtz resonance. Does unequal horizontal and/or vertical offset the the lower front ports have any effect on internal standing waves? How about unequal port diameters and lengths?

2.) Any suggestions about quality enclosure simulation software so I can learn more? Are the items OmniMic V2 and DATS acceptable for testing?...or too easily outgrown? These questions come to mind because I have many pairs of various aged mid-quality speakers and I want to restore/rebuild within reason so as to sell and fund my audio habit.

Thanks
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Old 27th June 2019, 10:55 PM   #864
tmuikku is offline tmuikku  Finland
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IHA might work fine but prototype box is mandatory I think. Post #858 drawing, simple construction, good! but the IHA port is in a place that it is difficult to tune unless removable front panel or some clever adjustable vent one can adjust through the horn hole by hand.

The IHA port might be most effective at the very top, it is all pressure nodes of standing waves there!

But, it might be just as effective (regarding mids leaking through the "main" ports) to just put damping material for the whole top section (above woofer) and not worry too much about the IHA port.

It is interesting to see how it turns out
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Old 3rd July 2019, 07:00 AM   #865
KaffiMann is offline KaffiMann  Norway
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Open Source "Tower XL"
Quote:
Originally Posted by tmuikku View Post
But, it might be just as effective (regarding mids leaking through the "main" ports) to just put damping material for the whole top section (above woofer) and not worry too much about the IHA port.
I think so too, a thick section of melamine foam up top instead of the IHA, will effectively kill most resonances there, add a half as thick layer at the bottom of the enclosure, and it should be a very "dead" box indeed.

I was convinced into ordering some melamine foam off ebay, in account of it's very dense OCF structure it is far superior to any polyurethane foam I've tried.
It will be my "go to" damping material for the foreseeable future, perhaps spiced up with wool felt in some cases.
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Old 3rd July 2019, 07:58 AM   #866
mbrennwa is offline mbrennwa  Switzerland
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Open Source "Tower XL"
I've had very good results with melamine foam in the Monkey Coffin. However, the melamine will not magically absorb the 145 Hz mode of the current Tower XL design. Sheep wool works better to absorb low frequency sound, but is also limited.

The idea of the IHA is that it presents a sink for sound waves at the frequency of the IHA tuning, instead of reflecting it back into the bass chamber. This is different to a hard wall reflector covered by damping material in an attempt to absorb the sound.
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Old 3rd July 2019, 08:32 AM   #867
KaffiMann is offline KaffiMann  Norway
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Different materials do have different uses.
Did not realize you had any modes triggering at 145hz in this, but not surprised, have not tried running any sims.
145hz might be a bit hard to deal with, regardless of which solution you implement. You might have some problems at around 300hz as well, but that's easier.

It would be easy to push the numbers of enclosure dimensions in a different direction to trigger more easy to deal with modes, but it seems that choices have been made and decisions set, and I will not try to convince change from a decision done "by heart".
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Old 3rd July 2019, 09:33 AM   #868
tmuikku is offline tmuikku  Finland
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In post #858 the woofer is roughly midway of the frontpanel height, so the lowest standing wave might be non existent, according to hornresp and my prototype.

Prototype is needed to see what the lowest leaking standing wave mode actually is and then tune the IHA to that. The section at the top will make the enclosure longer and lower the standing waves in frequency, also the woofer is not at the center of the box "height" anymore due to this elongated path.

Last edited by tmuikku; 3rd July 2019 at 09:48 AM.
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Old 3rd July 2019, 01:58 PM   #869
KaffiMann is offline KaffiMann  Norway
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... Did you include the alternate tapering top?
Would you mind sharing the numbers on that hornresp sim? Just a picture of the input window please. Not being lazy, but I just sneak in a couple minutes of diyaudio every now and then, packing and prepping for vacation, so very limited time for audio stuff.

Last edited by KaffiMann; 3rd July 2019 at 02:00 PM.
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Old 3rd July 2019, 04:25 PM   #870
tmuikku is offline tmuikku  Finland
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Quote:
Originally Posted by KaffiMann View Post
... Did you include the alternate tapering top?
Would you mind sharing the numbers on that hornresp sim? Just a picture of the input window please. Not being lazy, but I just sneak in a couple minutes of diyaudio every now and then, packing and prepping for vacation, so very limited time for audio stuff.

Hi, nope didn't include the tapering top, but one could try it in hornresp.
It is just a concept that seems to hold true with my prototype box. Use Hornresp MLTL wizard, tune parameters for your box, adjust L12 con (driver position) and see the lowest resonance come and go. Driver at ~halfway the resonance goes away, seems to be at the half wavelength on the longest dimension (attached, ~106cm height, ~160Hz lowest standing wave).

One could tame the lowest resonance with the IHA, and target some of the other resonances with the driver / port position. Thus, prototype necessary to see what the midrange leakage from the reflex port is, and then try to address them as much as needed, if needed.

ps.
All this is just one experiment of rather inexperienced tinkerer, so my advice might be just in the ballpark, which doesn't tell much for optimal performance. Optimal performance must be done with prototype box
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Last edited by tmuikku; 3rd July 2019 at 04:47 PM.
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