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Re: 4pi build with stands finally realized [message #94551 is a reply to message #94536] Sun, 03 October 2021 12:18 Go to previous messageGo to next message
Roger S. is currently offline  Roger S.
Messages: 15
Registered: September 2021
Location: Norway
Chancellor
Measurements are done indoors and in the 4pi box. I am using a diy turntable for off axis measurements. Some pillows on the floor helps, but with gated measurements or with frequency dependent windowing in REW it seems quite reliable in the midrange and up. I know outdoor measurements are preferred, but a lot of hassle.


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Re: 4pi build with stands finally realized [message #94552 is a reply to message #94551] Sun, 03 October 2021 13:05 Go to previous messageGo to next message
Roger S. is currently offline  Roger S.
Messages: 15
Registered: September 2021
Location: Norway
Chancellor
Made some measurements of the woofer before and after crossover. I got less noise when I laid the speakers on the floor. Called the guy who sold the woofers, and he insisted they were originals. He put his pride in this and said he had newer sold drivers with aftermarket recone kits. Made three measurements, with and without crossover on 0,25m, 0,5m and 0,75m distance. Averaged the three measurements for each case. It is smoothed 1/12 and has not got the resolution you get outdoors, but the general shape and location of the dips/peaks are consistent. Standing measurements show more or less the same. It is more useful to show the effect of the xo.

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Took measurements with my turntable going from -45 to +45 degrees, and with 5ms gating to remove most reflections from midrange and up. Horizontal power response looks good to me, and I think this correlates with what one is hearing if listening at distance in a reflective room as mine. There is a problem with flutter echo in my room and I hat to pull down the area from 1,3k to 3k with eq to get it balanced to my taste. This has been the case with almost every speaker I have had in this room.

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Re: 4pi build with stands finally realized [message #94554 is a reply to message #94552] Sun, 03 October 2021 13:47 Go to previous messageGo to next message
Roger S. is currently offline  Roger S.
Messages: 15
Registered: September 2021
Location: Norway
Chancellor
I have now spent some time listening, and the treble impresses me the most compared to my former setup with a Fane 60x50 tractrix horn. The horn has no honk as promised, and treble is airy and smooth. Good low level detail. After finetuning the eq notch around 1,3-3k I have no listening fatigue at all. With 500watt on the woofer, and 125watt for the horn, I had had no problem playing stupid loud either. Speakers are toed in in front of my listening position. I guess I listen closer to the 10 degree axis now, and imaging is really good. Integration with subwoofer was easy. Added +3db low shelf on the woofer to straighten the response a bit deeper, then added 80 Hz 4th order LR to the 4pi and 73 Hz 36db LR to the subwoofer. I tend to run the subs 4-6 db hot, so the effective xo for the sub will go up a bit. Timealigned the two, and transition is really good.
The last test I did was testing the port tuning. I disconnented one wire from the amp, attached an amperemeter and used the tone generator in REW to find the frequency with the impedance dip/highest current draw. I was surprised it was down at 35 Hz as the internal dimensions are exactly as described. Port dimensions and length are the same. I guess the damping material I added on top and sides behind the port is to blame. It is close enough to the port to extend the effective length. Will probably try to remove some of it later to rise the tuning. I am going to use subwofers anyway, and the effect at 80Hz is minimal anyway.
It has been a lot of work, but I am now a happy owner of 4pi's, and it is time to relax and listen to music. Hope this build will inspire others too;)
Re: 4pi build with stands finally realized [message #94555 is a reply to message #94554] Sun, 03 October 2021 14:14 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18155
Registered: January 2001
Illuminati (33rd Degree)

Your measurements look good, congratulations! I feel better about that 2226H cone now, because the measurements appear in line with what I expect from the OEM.

As for box tuning at 35Hz, that's not bad at all. The expected Helmholtz frequency is 37Hz - and that's what I've measured on several occasions - but even if you have some slight differences in your box or damping material that shifts it down to 35Hz, that's not too bad.

The truth is the 2226 will perform very well in cabinets from 2ft3 to 5ft3 with Helmholtz frequencies between 35Hz and 40Hz. I've found that the thing that matters more than the box tuning - provided it's in that range - is the positions of the driver and port in the cabinet and its size and shape because of internal standing waves. We don't want a pressure node to line up with the port or driver in the lower midrange 'cause that will give noticeable midrange aberrations.

I can see from your response curve that you loudspeaker system is free of any such aberrations and it is working as designed. https://audioroundtable.com/images/thumbs-up.gif
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