Augmenting the bass range of my speakers (inc. bi-amping)

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#83
Hi PM,

Progress has halted since I posted that last pic as I've been really unwell the last few days :xeye:

I feel just about ok enough to screw the side on again and add extra screws, but the MDF dust might flare up the coughing, so it might have to wait till tomorrow.


Could be thinking about the x-over for it, but I'm not even up to that right now. :dead:
 
#87
pinkmouse said:
Get well soon! 🙂
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Cheers man, I'm quite a lot better now 🙂

I decided I needed to seal the gaps in the loose panel as there was too much leakage and vibration. In the end I thought a coating of all purpose Sealant was the way to go as I could always tear this panel away from such a rubbery compound, unlike glue. I smeared some on with a finger, then screwed the panel on, then played some test tones and checked for leaks. I then sealed these from the outside.

The result - the port now breathes more violently and the drivers seem to be using less excursion. So the speaker is working more like it was designed to. The only output much under 40hz is extreme port wind, so I'd make the port larger if I did this again.

Think I'll give it another blast in the system now, and be thinking about making the x-over...
 
#88
I think the neighbours have maybe had enough of that listening test now 😉

It's very fun to play this with my main speakers.

I wonder why the excursion is so high though, any thoughts? I can make the cones travel far enough to induce bad noises with a 70w amp. This isn't what WINISD predicted, why?

This speaker is clealy not nearly capable of the max SPL it was supposed to be capable of.
 
#91
pinkmouse said:
Hmm, the port is obviously wrong somehow. What happens if you block it completely?
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Blocking completely is easier said than done, but covering it with my hand cone excursion is reduced at 25hz but increased at 31hz and especially 40hz. This would suggest it's tuned correctly I think.


richie00boy said:
What frequency were you expecting the vent to be tuned to? Let me know the box outer dimensions, panel thickness, vent length, height and width, and I'll do a double check for you.
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It's supposed to be tuned to 40hz. Externally it's 600 x 188 x 460 mm. The port is 250 mm long, 145mm wide and 30mm high.

Actually, I think the port may be slightly detuned. I might not have taken account of the thickness of the front panel :xeye:
 
#92
Yes, I accidentally made the port a little longer than it should be. It would appear to actually be tuned to about 39hz, see pic. Doesn't make much difference tho, and I think it sort of sounds as it models - a little shy.

I'm still no closer to understanding about the excursion though.
 

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#95
Hi all. This project seems to have run out of steam right now, as the isobaric ported prototype was only 'ok' and not impressive enough to justify carrying on with and building two of.

With the other speaker being cut to the right shape for a ported box (boring) I wondered if I could squeeze a transmission line in there. I've heard one set of TLs and I loved the smooth high quality bass they made. Like nothing else.

I've drawn to scale a possible maze arrangement, and although it's long enough I think (just about 1/4 wavelength of Fs) it's rather a small diameter line. Worth building to try??
 

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