Home » Sponsored » Pi Speakers » 4Pi - alternate compression driver mounting?
Re: 4Pi - alternate compression driver mounting? [message #94819 is a reply to message #94807] Sun, 14 November 2021 00:23 Go to previous messageGo to next message
areohbe is currently offline  areohbe
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Registered: May 2021
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I'm a complete amateur and a sucker for aesthetics. I have a pair of Wayne's crossovers and waveguides in hand.

I hope to have some prototype MDF cabinets complete by end of year. Will share results once I get there.
Re: 4Pi - alternate compression driver mounting? [message #94849 is a reply to message #94819] Mon, 29 November 2021 12:03 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
Chancellor
Squeezed in a couple hours of work over the Thanksgiving holiday.

JBLs arrive later this week. Then, I'll complete the cutouts for the driver and port.

DE250 is backordered until 12/15. Confused But, still hoping to have some measurements by end of year.

/forum/index.php?t=getfile&id=2915&private=0

/forum/index.php?t=getfile&id=2916&private=0
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Re: 4Pi - alternate compression driver mounting? [message #95025 is a reply to message #94478] Sun, 02 January 2022 20:31 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
Chancellor
All glued up!

Will be diving in to REW for the first time this week. Hoping the frequency response gods are looking fondly on me and everything measures as desired.

The DE250 is still backordered. Hoping it arrives mid Jan when I get back from an upcoming trip.

Had a lot of inspiration/design tweaks while building out this prototype cabinet. And, of course, made a few mistakes that I'll be able to avoid in the final build.

I thought I was excited before, but it's starting to feel real and I can't wait to get these hooked up and in their final resting place.

/forum/index.php?t=getfile&id=2943&private=0
Re: 4Pi - alternate compression driver mounting? [message #95026 is a reply to message #95025] Mon, 03 January 2022 09:40 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
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Registered: January 2001
Illuminati (33rd Degree)

Lookin' good!

Fingers crossed on the measurements!
Re: 4Pi - alternate compression driver mounting? [message #95072 is a reply to message #94478] Tue, 11 January 2022 21:17 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
Chancellor
The DE250's got pushed back again. Parts Express is now estimating March. Sad

I picked up some PSD2002's in a panic. They were already out of stock at PE. I'd imagine they'll be backordered everywhere soon as well.

The 2002s are schedule to arrive tomorrow. Very Happy
Re: 4Pi - alternate compression driver mounting? [message #95082 is a reply to message #94478] Fri, 14 January 2022 18:25 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
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$75 class D amp, no dampening yet, and already pure bliss. Very Happy Very Happy Very Happy

/forum/index.php?t=getfile&id=2989&private=0
Re: 4Pi - alternate compression driver mounting? [message #95086 is a reply to message #94478] Sat, 15 January 2022 20:36 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
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Short video if anyone is interested. Nothing fancy, recorded on an iPhone. YouTube link.

I'm by no means an audiophile, but sounds pretty damn good to my ears.
Re: 4Pi - alternate compression driver mounting? [message #95088 is a reply to message #95086] Sun, 16 January 2022 10:56 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18364
Registered: January 2001
Illuminati (33rd Degree)

Looks like a really cool build!
Re: 4Pi - alternate compression driver mounting? [message #95141 is a reply to message #94478] Thu, 27 January 2022 22:21 Go to previous messageGo to next message
areohbe is currently offline  areohbe
Messages: 20
Registered: May 2021
Chancellor
Wayne - I'm sorry but I have a few quite a few questions about proper measurement technique...

I've dug through the forums and found answers to some but not all of my questions. So here we go...

How "wide open" of an area do you need be in to reap the benefits of testing outside? I'd imagine this depends if your testing with speaker laid on its back or upright?

The performance measurement page indicates the mic should be placed 10 feet from the front baffle. Does this differ depending on the measurement device or any other variables? I am using a UMIK-1.

How important is the quality/type of amp used?

The measurement page says a drive voltage of 8.2vrms was used. Do I need to measure my amp's vrms? Or is this not relevant if I am sending a signal from REW out of my laptop into the amp? (I feel really dumb for asking... does it matter what level the "bass" and "treble" gains are set at?)

Related to vrms, do I need to worry about this "Calibrate Level" setting in REW?
/forum/index.php?t=getfile&id=2993&private=0

Thanks in advance, Wayne. Really appreciate the care and energy you put in here.

Here's a pic from some preliminary tests the other night. I'm a bit bashful to share my results until I know I am doing everything correctly. Sad

/forum/index.php?t=getfile&id=2994&private=0

Re: 4Pi - alternate compression driver mounting? [message #95144 is a reply to message #95141] Fri, 28 January 2022 12:13 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18364
Registered: January 2001
Illuminati (33rd Degree)

The quality of your environment will be reflected in the quality of your measurements. Oh, such a pun in that sentence. Laughing

For measurement charts that will be published, I would recommend no less than 30 feet of unobstructed reflection-free area. On the other end of the scale, if you just want to look at the frequency range near crossover - like during development or to see the position of the vertical nulls - then just a few feet is enough. You can use a gated pseudo-anechoic measurement for that.

Your backyard has a lot of items that will reflect sound, so it is really only suitable for the latter. But that's pretty good because the main thing you want to see is the position of the vertical nulls. Being outdoors, you won't have room modes, so you'll be able to see a general trend that is accurate down through the bass range. But it will be only the general trend that's accurate - you'll see plenty of peaks and dips that wouldn't be there is an anechoic environment. So expect that.

As for the amp, it's generally not an issue unless it is pushed into clipping. I doubt you'll do that, but just to be safe, don't push the amp hard. I don't think you're testing max-SPL, so keep the signal under 10v. And on that subject, the drive signal level isn't all that important. It just needs to be enough to overcome the noise floor. I tend to use multiples that easily calculate back to a 2.83v/1M value. This allows me to measure voltage sensitivity along with everything else I'm trying to see.

Which is what that "calibrate level" task is doing for you. If you measure the voltage at the speakers and enter that into your measurement system - and if the system knows the microphone distance too - then it can provide a chart that shows what SPL values would be measured at 2.83v with the microphone at one meter. This has become a standard, so it's useful for comparison with other systems.

Lastly, you're going to want to lay your speaker on its back, facing upwards. Measure it like shown in the video in the post below. Scroll down to the link that says "Vertical Nulls." It will show you how to position your microphone and what to look for.
Sadly, this won't be enough to verify the response in the 100-400Hz range, which is where I would expect to find problems from internal standing waves. The objects around the speaker will create reflections that will modify response in this region. What you might want to do is to clear out as many of the things in your back yard as you can, making it as reflection-free as possible. Then set the speaker in the middle of the yard as far from the house and the fences as possible. The further away you can get from reflectors, the lower in frequency your measurements will be accurate. Hopefully that will be enough to see smooth response in the 100-400Hz region, to verify that the port and driver arrangement is not causing any midrange anomalies.
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