Ok, so looking closely at Bjornos modelling, clearly I should have used some stuffing to eliminate the spikes at around the port resonance. This was an oversight on my part, but lessons learnt! This was a trial for me, and I'm really happy with the results. My floorstanders have useable response down to approx 45Hz, so this design was intended mainly to fill from there down. My "as built" port length was 1.3meters.
Thanks
Thanks
Put 4 coats of primer on, leaving the top coat for next summer, should give the enclosure time to climatize, possibility for seems to open up, so don't see point in finishing it yet anyway.
All sounding well, really happy with it. When I open it up next year, I'll consider putting acoustic lining on the panel behind the drivers, as I suspect this is contributing to a slightly muddy upper bass - reflections coming through the driver. It's barely noticeable, I'm just being quite picky
Any advice on what type of lining might be suitable? I've seen some eggbox self adhesive foam which might be ok - Eggbox Profile Foam Laminate Panel
Thanks
All sounding well, really happy with it. When I open it up next year, I'll consider putting acoustic lining on the panel behind the drivers, as I suspect this is contributing to a slightly muddy upper bass - reflections coming through the driver. It's barely noticeable, I'm just being quite picky
Any advice on what type of lining might be suitable? I've seen some eggbox self adhesive foam which might be ok - Eggbox Profile Foam Laminate Panel
Thanks
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Measurements with UMIK. Pink Line is natural response with only the AV Amps 60Hz - 24dB/octave LPF. Blue Line is the same but with mild PEQ applied.
Each of the two lines are averages derived from 5 positions (across 3 seats on a sofa), with the mic in the exact same spot for each of the 5 x before and after PEQ measurements.
Martin
Each of the two lines are averages derived from 5 positions (across 3 seats on a sofa), with the mic in the exact same spot for each of the 5 x before and after PEQ measurements.
Martin
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Thanks. I'm really happy with it. Here's some more measurements. This time, I took 27 measurements from 9 points across the whole of my corner four seat sofa. These are averages of 9 measurements. I've included the raw measurements too.
Pink Line - 250Hz 24dB/oct LPF.
Blue Line - Above + PEQ
Green Line - Above + 16Hz BW 30dB/oct HPF + 100Hz BW 12dB/oct LPF
I also played a song with 30Hz content, and recorded 116.5dB on the REW meter with UMIK. Really should have done a sweep as well, but headache and neighbours inhibited me. I'll post that another weekend.
Thanks for everyone's help on this forum. Cheers, Martin
Pink Line - 250Hz 24dB/oct LPF.
Blue Line - Above + PEQ
Green Line - Above + 16Hz BW 30dB/oct HPF + 100Hz BW 12dB/oct LPF
I also played a song with 30Hz content, and recorded 116.5dB on the REW meter with UMIK. Really should have done a sweep as well, but headache and neighbours inhibited me. I'll post that another weekend.
Thanks for everyone's help on this forum. Cheers, Martin
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Thanks Jag768, and many thanks for the inspiration along the way.
The reality is I would not have built this without the contributions from diyaudio. This was a learning experience for myself, and I can only hope the record of my design (including its faults), will help others in the future.
Cheers, Martin
The reality is I would not have built this without the contributions from diyaudio. This was a learning experience for myself, and I can only hope the record of my design (including its faults), will help others in the future.
Cheers, Martin
Jag768. I forgot to mention - I bought the Minidsp 2x4 HD version. The graphs above show a subsonic filter applied, with what appears to be no peaking. I know this isn't the best method to test, should really be done with electrical measurements directly at the input and output of the minidsp, but I'm guessing any peaking would show up in the green response curve?
Cheers
Cheers
Totally agree. Ill try to remember linking to this thread if ever this issue comes up again
Thanks. Really happy with the measurements, although I'm not sure how the response manages to stay relatively flat down to 10Hz. Doesnt make any difference once the subsonic filter is applied anyway.
I have one of the minidsp slots configured without the subsonic filter, but a compressor instead, so achieve response down to 10Hz, and no group delay associated with the subsonic filter, but with limited output
Totally agree. Ill try to remember linking to this thread if ever this issue comes up again
Thanks for confirming. Hoping the info comes in handy for others.
Even a nearfield room measurement will show lots of ambient noise below 30Hz, so it is not reliable. Outdoor ground plane would be better. It also depneds on the mic capsule, amp and software used.
I'm planning to line opposing panels only on the inside of this box, to reduce artefacts, muddiness in the upper bass and eliminate reflections. I've found some sticky back egg box foam. Attached is an example of the sound absorption coefficient. Any thoughts on whether this will improve in the way I'm hoping? I'd be happy with any improvement, so currently thinking about lining the wall behind the top driver, top panel and one side panel.
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This is the 35mm egg box acoustic foam -
Eggbox Profile Foam Laminate Panel
Or there's a 10mm flat foam with a 2mm bitumen backing -
Acoustic Foam Laminate Panel
Any thoughts / suggestions would be greatly appreciated.
Eggbox Profile Foam Laminate Panel
Or there's a 10mm flat foam with a 2mm bitumen backing -
Acoustic Foam Laminate Panel
Any thoughts / suggestions would be greatly appreciated.
Attachments
This site recommends 30mm egg crate foam for "large bass cabs" in their own words -
Cabinet-damping
Cabinet-damping
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