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Re: 3 Pi plans [message #88944 is a reply to message #88941]

Fri, 05 October 2018 14:57

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

drake wrote on Fri, 05 October 2018 12:20

I do hope that I can be able to design such a thing from scratch because it would save on costs.

These are kits, so you don't have to design and test. You just have to build the cabinet, or have a professional cabinetmaker do it for you. Some of the builders have made some really beautiful cabinets.

three π loudspeaker performance data

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Re: 3 Pi plans [message #89861 is a reply to message #86772]

Thu, 28 February 2019 05:52

Mabob
Messages: 23
Registered: December 2017
Location: Finland

Chancellor

Hello

I´m back with a few pictures of the finished speakers. I've been enjoying them for a few months now and this is how the setup in my Man cave/garage look right now.

The coating is a tinted acrylic lacquer which was a pain to apply evenly. Next cabinets will definitely be veneered.

My listening impressions so far is that the high end is very good. There's no harshness whatsoever even if you really crank it up! I can also hear vocals like never before Smile

Loads of stuff I didn't even know that was there!

Bass extension is not enough for my liking/room, therefore I built a BFM Table Tuba to take care of the lowest notes. I still feel that on certain music/recordings there is a bit too little attack/energy on drums or even guitar? Hard to put a finger on it... Anyone else experienced something like this? Using a Onkyo home theater amp, but haven't used Audyssey for calibration.

Overall very impressed and happy with the speakers!

Mathias

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Re: 3 Pi plans [message #89862 is a reply to message #89861]

Thu, 28 February 2019 08:59

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

Those look stunning!

To improve the upper midbass and lower midrange, you have two options that come to mind right away:

1. Upgrade the midwoofer to the Definimax 4012HO. It's a drop-in swap, with only a single capacitor change on the crossover. Swap the 10uF capacitor in position C4 to a 20uF cap.

2. To mitigate room effects, incorporate flanking subs. They will improve the frequency response between 75Hz and 150Hz in most rooms. Without flanking subs, there is response ripple and almost always at least one huge notch in this range. It can make vocals sound throaty and guitars can sound weak or shrill, depending on the room. Sometimes the effects are subtle, sometimes they're huge. But flanking subs will always improve this range, reducing the intensity of the anomalies significantly, by at least 2x.

When adding flanking subs, you can put the hornsub at the opposite corner of the room and crossover very low using a summed LFE channnel. Let your hornsub handle the deepest bass - High-pass at 30Hz (24dB/octave) to prevent over-excursion and low-pass at 60Hz-80Hz (24dB/octave) to prevent localization. Placing the hornsub relatively far from the mains helps smooth low-frequency room modes.

Flanking subs are placed just beside, behind and below each of the mains. They are sent a low-passed copy of the signal sent to the mains they are flanking. Flanking subs are low-passed at 100Hz (12dB/octave) which allows plenty of upper midbass to reach the subs. In fact, they're even generating some lower midrange, up to around 150Hz, because of the gentle crossover slope.

Flanking subs are really like a woofer of a three-way setup, blended with the midwoofer in the mains. But since they are a couple of feet beside, behind and below the mains, they smooth higher-frequency room modes and self-interference from the nearest boundaries. The worst offender is generally the self-interference notch caused by the reflection from the wall behind the speakers.

By using both the hornsub and the flanking subs, you will have a multisub setup that will really make the bass smooth. The three subs in their different positions will all contribute to smooth the lower-frequency room modes, from 30Hz up to 100Hz. And as I said above, the flanking subs will smooth the region between 75Hz and 150Hz or so.

It's an upgrade path with incremental updates that you can do as time and finances permit.

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Re: 3 Pi plans [message #89868 is a reply to message #89862]

Fri, 01 March 2019 07:13

Mabob
Messages: 23
Registered: December 2017
Location: Finland

Chancellor

Thank you for the in depth answer Wayne!

This answers pretty much all the things I've been wondering about the use of flanking subs.

I was looking at the Definimax woofer, and even if it would be an update I won't go down that road at this moment. These are quite pricey and availability is not very good here.

The obvious choice for flanking subs would of course be the 3pi subwoofer, but being on a tight budget I'm looking for a budget alternative to this.

What I'm wondering is that if the flanking subs don't have to go very low lets say nothing below 40hz, could I get away with something less beefy than the LAB12? I really like the BFM Table Tuba and was wondering if the T18 loaded with a 10" would be up for the job? The horns are quite easy to drive, they don't need much power.

I can see one more way for an update and that is the 6Pi cornerhorn, since I have the corners for them. Would this be a good way to go for dealing with the issues in the bass?

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Re: 3 Pi plans [message #89870 is a reply to message #89868]

Fri, 01 March 2019 10:11

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

Flanking subs are really just "helper woofers" except that they are generally tuned to provide deep extension. That way you get both benefits - Blending in the 75Hz to 150Hz range gives SBIR smoothing and extension below that gives more deep bass nodes. That allows one or two distant subs to complete the total multisub package.

But for SBIR smoothing, you only need to blend in the upper midbass range. You could get a pair of Alpha 10 drivers and put them in 3-5ft³ cabinets tuned to 40Hz. Set 'em up a couple feet beside, behind and below the mains and send each the requisite signal (100Hz 2nd-order low-passed copy of the main speaker being flanked). Or you could get another pair of Delta 12LF drivers and do something similar.

The main thing is that the acoustic center be a couple feet away from the mains in all three dimensions. That makes bass horns unsuitable for flanking subs because they're too long. The acoustic center can't be made close enough to the mains. Could be done with delay, but I would rather see hornsubs be used as distant multisubs.

As for constant directivity cornerhorns, if you have the right room, that's really the best way to go. They don't even need flanking subs because they don't suffer from self-interference from the nearest boundaries. They are acoustically close to the nearest boundaries, so they're more like vertical ground planes than reflectors. See the links below for more information:

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Re: 3 Pi plans [message #89912 is a reply to message #89870]

Mon, 11 March 2019 17:15

Mabob
Messages: 23
Registered: December 2017
Location: Finland

Chancellor

Thanks for all the information on flanking subs and the corner horns. After much consideration and I think that I will upgrade my 3pi.s to 6pi cornerhorns. I think that way I'll make the most of my limited space.

The back wall is about 3m wide and if I build flanking subs I'll get the speakers too close to my listening position. It'll also be a good challenge to build the mid horns, I really like the look of them!

One thing that bothered me about building flanking subs was finding the right amplification with proper filters. My HT amp has no pre outs, only sub out, which is a mono signal I think. And the plate amp I have has a much steeper lowpass filter than the one you recommend.

So at the moment 6pi feels like the way to go. Additional multisubs might be used if I feel it's necessary. If I understand it right, there is nothing wrong with horn subs as long as not being used as flanking subs?

Built some speaker stands to get them down to the right level. This was a big update that didn't cost much Rolling Eyes

should have done this ages ago!

Well, I'm eager to start a new build, so can I have the 6pi plans please!

/forum/index.php?t=getfile&id=2344&private=0

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Re: 3 Pi plans [message #89915 is a reply to message #89912]

Tue, 12 March 2019 14:43

Wayne Parham
Messages: 18786
Registered: January 2001

Illuminati (33rd Degree)

That sure is a nice looking pair of three π speakers! I like the stands they're on too. They'd be perfect for use with flanking subs.

The way to implement flanking subs is to use the left and right preamp outputs as input signals for the left and right flanking subs. You use a 100Hz second-order low-pass filter for the crossover.

But if you have the right corners, constant-directivity cornerhorns are even better. They don't need flanking subs because they're acoustically close to the walls. The wavefront illustration in the link above shows this nicely. So check your inbox - I've sent the plans for six π cornerhorns.

You can always save your three π cabinets. Put them in storage in case you need to setup a sound system in a room that doesn't have corners suitable for constant-directivity cornerhorns.

In the meantime, run your hornsubs in the opposite corners from your constant-directivity cornerhorns. The hornsubs can be run from the LFE channel, which sums all channels and has a steep low-pass filter to prevent localization. This is a Welti multisub setup and it does a great job of smoothing the low frequency room modes.

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Re: 3 Pi plans [message #89917 is a reply to message #89915]

Wed, 13 March 2019 13:12

Mabob
Messages: 23
Registered: December 2017
Location: Finland

Chancellor

Thanks for the Six Pi plans and nice words about my build!

I really like the way they look on the stands and I'm sure I would be satisfied with this setup after adding flanking subs. What stops me going down that road at the moment is that I would have to upgrade to a pre and poweramp combo plus adding filters.

That being said I just picked up an old Crown XLS402 poweramp Very Happy

Still missing a signal source and filters, so saving that one for the moment.

As you said

"if you have the right corners, constant-directivity cornerhorns are even better. They don't need flanking subs because they're acoustically close to the walls."

Just went over the size measurements for the Six Pis and noticed that they will intrude less in my room compared to Three Pi/Flanking subs.

Will be checking out joshua43214 detailed build log of the midhorn!

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