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Three Pi and Three Pi Sub Plans [message #91007] Wed, 02 October 2019 14:22 Go to next message
timothyeyster is currently offline  timothyeyster
Messages: 4
Registered: October 2019
Esquire
Hi, Wayne.

Firstly, thanks for sharing all of this fantastic information and for providing your products to the DIY community!

Secondly, I purchased a pair of your H290C waveguides yesterday to go with a pair of DE250s I have (thanks for shipping those so quickly, by the way), and would love a copy of your plans for the Three Pi and the Three Pi Subwoofer to look over. Could you also please point me toward the appropriate crossover schematics/layouts?

Lastly, when I decide which woofer I'd like to use in my builds, is that something I could purchase from you a-la-carte, or do you only sell those packaged within the kits?

Thanks again,

Tim

Re: Three Pi and Three Pi Sub Plans [message #91013 is a reply to message #91007] Thu, 03 October 2019 09:03 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17598
Registered: January 2001
Illuminati (33rd Degree)

We don't sell partial kits or raw drivers. But we do well the crossovers individually (assembled or unstuffed) for those that want to source their own drivers.

I'll send plans directly to your email address. The plans include the crossover schematic.
Re: Three Pi and Three Pi Sub Plans [message #91068 is a reply to message #91013] Sat, 12 October 2019 16:49 Go to previous messageGo to next message
timothyeyster is currently offline  timothyeyster
Messages: 4
Registered: October 2019
Esquire
Wayne,

Thanks for sending those over!

The 3Pi design is really elegant, and, I'm convinced, would perform incredibly well. Unfortunately, after much consideration, I just don't think it will shoehorn into my space due to the cabinet size.

I started modeling alternative boxes in WinISD, and think I found a good compromise: Using the B&C 12PLB100 woofer you've identified, I tried B&C's recommended box size of 1.41 cuft tuned to 52HZ, and came up with a ruler-flat response to 60HZ that then slopes quickly to -3db at 50HZ. This seems like acceptable low frequency cutoff to me, especially if used with flanking woofers.

However, after reading your thinking behind the larger box with the EBS alignment, and how it's meant to play lower and integrate better with flanking woofers, I'm wondering if I'd lose more than just a little low end extension using this smaller box. I'm also wondering if I were to change the box alignment, if a substantial redesign of the crossover will also be required.

Having already gotten so much great information from you and this site, I feel bad asking for more. But, if you would be willing to share your thoughts on this, or point me toward further reading, I'd sure appreciate it.

Thanks again,

Tim
Re: Three Pi and Three Pi Sub Plans [message #91083 is a reply to message #91068] Mon, 14 October 2019 10:37 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17598
Registered: January 2001
Illuminati (33rd Degree)

What you propose sounds like it would work pretty well. You would lose a couple synergies that are designed into the three π and four π models though. And you would need to test your design with acoustic measurements, paying special attention to the lower midrange. I think you'd be alright there though, because your cabinet is small enough that it would have relatively high-frequency standing waves inside, and those would be attenuated the fiberglass stuffing material. The standing waves are potentially problematic in larger cabinets.

The synergies I'm talking about are matching the baffle step with the flanking sub rolloff, which both conjugates baffle step and mitigates higher-frequency room modes and self-interference notches from nearest boundaries. This is what you get from the existing three π and four π designs when used with flanking subs.

A smaller baffle will have baffle step higher in frequency, and you wouldn't want to run flanking subs high enough to fill in that gap. So there will be a little bit of a droop between the flanking sub upper frequency and the baffle step frequency.

But you might still give it a go. I wouldn't try to compensate for baffle step with an electronic filter, I'd just live with the droop and see if it was objectionable. My guess is it would sound just fine.
Re: Three Pi and Three Pi Sub Plans [message #91085 is a reply to message #91083] Mon, 14 October 2019 14:33 Go to previous messageGo to next message
timothyeyster is currently offline  timothyeyster
Messages: 4
Registered: October 2019
Esquire
Thanks for the great response; that's exactly what I was trying to understand. Again, the design seems very elegant, and I wish I could accommodate the cabinets in my room.

I have been thinking about building a baffle wall, however, as I already have an AT projector screen, but am unhappy with the in-wall speakers installed behind it currently. If I understand correctly, these proposed shrunken Three Pis set into that baffle would not suffer from baffle step loss, so should perform quite evenly down to their roll off frequency excepting interference from room modes. Is that correct?

Then, at that point, would you still recommend the flanking subs, or would it make more sense to just run several distributed subs crossed at a lower frequency?

Again, thanks for all of the great info!


Re: Three Pi and Three Pi Sub Plans [message #91086 is a reply to message #91085] Mon, 14 October 2019 17:13 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17598
Registered: January 2001
Illuminati (33rd Degree)

If you can mount the speakers in the wall, that's perfect because it removes self-interference from the wall as well as removing any baffle step. It really is the best option. You can setup the subs as distributed multisubs rather than flanking subs.

However, you will lose the left/right self-correcting imaging if you don't toe them in so that their forward axes cross in front of the listeners. Is it possible to do that to the left and right speakers? Can you provide a wedge-shaped baffle that connects to the wall and still offers toe-in?

If you cannot, it isn't terrible for movies, especially if you have a center dialog channel. But it is really nice because the left and right speakers are balanced over a wider range of positions. When the axes cross, people sitting nearer the left speaker will still hear the right channel very well, and vice versa.

As I said, it isn't terrible to forego the axes-crossing for home theater if you have a center channel. But it is better to have both a center channel and left/right axes crossing. And if you don't have a center channel, like when you are listening to stereo, or if you are attempting to create a phantom center, you'll really benefit from the toe-in that crosses the axes in front of the listeners.
Re: Three Pi and Three Pi Sub Plans [message #91221 is a reply to message #91086] Sun, 24 November 2019 16:36 Go to previous messageGo to next message
timothyeyster is currently offline  timothyeyster
Messages: 4
Registered: October 2019
Esquire
Wayne,

After much consideration, I ended up building a pair of Three Pis per your plans. They are a bit dominating in my current room, but will eventually go behind an AT projector screen (hopefully with enough space to cross their forward axes properly). In terms of the sound, I'm very happy with the dynamics, detail, and imaging- really nice sounding speakers. I noticed right away that the high-end balance is very depressed compared to most other speakers I've had. Running an Audyssey auto setup brought them much more in line with my preference, but shelved the high end nearly 10db. Does that seem normal with these, or might I have made a mistake building the crossovers? I'm using the DE250, and the B&C 12PLB100 woofer.

Also, though the bass is quite good, I'm eager to add the Three Pi flanking subs to complete the picture. I ordered a pair of kits from your site last week, and look forward to building the boxes shortly. Could you please clarify for me how best to accomplish the port on these? Is there something included in the kit, or do I use PVC pipe?

Thanks again for all of the great information!

Tim
Re: Three Pi and Three Pi Sub Plans [message #91222 is a reply to message #91221] Sun, 24 November 2019 16:47 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 17598
Registered: January 2001
Illuminati (33rd Degree)

Glad you got the mains done! I'm sorry you're having trouble with the tweeter circuit though. Do check your connections - The treble SPL should be equal to the bass SPL. Without R1/R2 attenuation/compensation, the tweeter would be 10dB higher than the midwoofer, so something is amiss. Could be that you've effectively shorted R1 in some way.

The sub kits have port material included, so wait until they arrive and cut the port hole to match the duct material. The hole diameter shown in the plans is accurate, but having the duct in your hand might help you get it exactly right.
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