Home » Sponsored » Pi Speakers » 4PI Plans Request
Re: 4PI Plans Request [message #91242 is a reply to message #91241] Mon, 09 December 2019 09:42 Go to previous messageGo to next message
mathiasb is currently offline  mathiasb
Messages: 6
Registered: December 2019
Location: WA
Esquire
Barryso wrote on Mon, 09 December 2019 09:13
I've not heard the HTM-10's. There are a number of threads on other forums that go into detail about the DIYSG speakers and their designers seem well spoken and diligent. There are many folks that have built them that like them.

Thing is, you already have the 2226h woofers. These aren't the entry level woofers for the 4 pi's but the full blown upgrade woofer. They are also the single most expensive part in the 4 pi build - about $1000 for a brand new pair. It's a great woofer even when you have to buy them retail but you already have them ... IMHO it'd kinda be a shame to ignore them.

My $0.02.

Thank you for your reply! I currently have the HTM-10's myself, but have only had them for less than a year, and paired with a subwoofer all this time. I haven't given them the chance to see "what they can do".

My plan for the JBL's was to build MBM modules, or to perhaps build the 4Pi speakers and replace the HTM10's in the living room. I have to do some more research - if it is possible to build the 4Pi with an active crossover (MiniDSP) instead of an active one, I might try that first.
Re: 4PI Plans Request [message #91243 is a reply to message #91242] Mon, 09 December 2019 10:47 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17639
Registered: January 2001
Illuminati (33rd Degree)

You've got mail!

I agree with Barry about the JBL 2226H. It is an excellent midwoofer. The flux stabilization ring in the motor structure reduces distortion down to the levels normally only seen in horns. When combined with a horn tweeter, you have a system that is very smooth and distortion free.

Also compare the H290C waveguide to the SEOS12. The H290C is measurably smoother. I considered using the SEOS12 at one time, but I wasn't happy with its performance. It has peaks that must be smoothed with notch filters in the crossover. So I designed the H290C waveguide specifically to allow an upgrade path beyond that.
Don't get me wrong - SEOS enthusiasts are very much like Pi Speakers enthusiasts. And their waveguides and loudspeaker designs are very good. In fact, when they started out, many of them were regulars here and on (Zilch) Evan Flavell's "Econowave" threads. Pi Speakers is sort of like the grandfather design for Econowave and SEOS speakers. The loudspeaker models here were inspirations for their designs.

That's why I considered using the SEOS waveguide when they first started out. I had a wood horn/wavguide that provided constant directivity, but it was very expensive. My other option was a radial horn that had nearly constant-directivity. This was much more popular because of its cost. So I was looking for an upgrade path for the radial horn using a horn/waveguide of approximately the same physical dimensions.

At that time, about ten years ago, the guys that are now DIYSG were talking about making a waveguide too. Back then, I thought we might work together. And like I said, many of them were regulars on this forum and on the Econowave thread. We were all very much kindred spirits.

But we diverged mostly on the points of acoustic loading. We agreed on pretty much all other aspects. I personally do not like waveguides that deoptimize acoustic (horn) loading because they become excessively resonant and require notch filters in the crossover to avoid peaks in response.

So I chose to have an injection mold made for the H290C horn/waveguide, which was very much like the expensive wood horn/waveguide I offered at the time. The H290C does everything I want it to do, at a reasonable cost. It provides constant directivity and is very smooth, not needing notch filters in the crossover.

And speaking about the crossover, I suggest that you stick with the passive crossover as shown in the plans. You could employ an active crossover, but it must have the exact same transfer function as the passive crossover or you would be degrading performance rather than improving it.

I use a digital active crossover to design the passive crossover. It uses an impedance chart in the form of a ZMA file to incorporate the actual electro-mechanico-acoustic load of the drivers in the system. See the link below for more information about the process.
Systems with active crossovers have their benefits, but first-things-first: To get amplitude and phase response right, we need either to include the driver's electro-mechanico-acoustic interaction directly with the passive components, or if isolated using an active filter, we need to be able to employ a ZMA file or some other way of including the load impedance.

It's an Nth degree thing. You can definitely make a great loudspeaker without this kind of precision. It's like making a hotrod car with a carburetor and distributor with ignition points. You can make some awesome stuff with that technology. But if you have a computer sensing oxygen and detonation, you can get even better performance.

While some might see the passive crossover to be more akin to the carburetor, it's not the case. The passive crossover has been dialed-in with the computer. So in this case, the passive crossover is the one that is the Nth degree solution.

An active crossover that didn't exactly emulate the transfer function described above would be more like the computer controlled carburetors of the 1980s. It wouldn't be exactly right. Sort of like how the computers in the 1980s cars couldn't detect detonation and their narrow-band oxygen sensors don't have the ability to provide an accurate signal. They couldn't rapidly change the air/fuel mixture or set the ignition timing. So even though those 1980s cars had computers, they didn't offer much in the way of performance. Same could be said of an active crossover that wasn't dialed in, but instead used generic filter functions.

The only way to get an active crossover to give a true benefit would be to employ a digital filter like I use for designing, one that has an impedance plot of the drivers in the system. It would then give the exact same transfer function as the passive unit.

And one last thing. Not something you asked about but worth mentioning anyway. I highly recommend flanking subs be used. They work very well with my mains or with DIYSG speakers. They are a subset of the multisub concept, which is another thing I advise. But if you want to start small, use two flanking subs and then later add another sub or two, placed further away. I call the distant subs "distributed" multisubs, to distinguish them from flanking subs. But both "flanking subs" and "distributed subs" are parts of a total multisub setup.
Re: 4PI Plans Request [message #91244 is a reply to message #91243] Mon, 09 December 2019 11:40 Go to previous messageGo to next message
mathiasb is currently offline  mathiasb
Messages: 6
Registered: December 2019
Location: WA
Esquire
Wayne Parham wrote on Mon, 09 December 2019 10:47

You've got mail!

I agree with Barry about the JBL 2226H. It is an excellent midwoofer. The flux stabilization ring in the motor structure reduces distortion down to the levels normally only seen in horns. When combined with a horn tweeter, you have a system that is very smooth and distortion free.

[...]


Thank you! Offtopic: Perhaps I'll change my two Ultimax 18's (build thread) from LFE signal to flanking subs, making them extensions of the (current) HTM-10's, versus being on the LFE channel alone. It would however require setting the front speakers to "large", and I have no way of highpassing them in the AVR that way.
So, I'd need a second stereo amp to do that.

Current:
(AVR: FL/FR small - 2 subs)
AVR amp FL/FR pre-out > HTM-10 FL/FR
AVR amp LFE x2 > MiniDSP 2x4HD > Crest 7.5 > 2x sealed Ultimax 18

Proposed:
(AVR: FL/FR large - no subs)
AVR amp FL/FR pre-out > MiniDSP 2x4HD
MiniDSP 2x4HD > HTM-10 FL/FR
MiniDSP 2x4HD > Crest 7.5 > 2x sealed Ultimax 18

Then landing Audyssey XT32 on top of all that Smile, it'd be a challenge but has potential.
Re: 4PI Plans Request [message #91245 is a reply to message #91244] Mon, 09 December 2019 12:25 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17639
Registered: January 2001
Illuminati (33rd Degree)

I think that's a good way to go. Run the flanking subs with a 100Hz/2nd-order low-passed copy of the signal sent to the main speaker each sub is flanking. Run the mains set to "large" so you blend with the flanking subs. The mains should be able to handle the LF content unless they just really can't handle the low notes or you are pushing them close to their limits. If you're pushing them hard, then high-pass them at their Helmholtz frequency.

This Helmholtz recommendation is, of course, relevant for vented systems. Above the Helmholtz frequency the vent reduces excursion, but below Helmholtz the woofer is unloaded. If sealed, it's not such a stark a change in excursion but then again, there is no reduction of excursion from the vent. So for sealed woofers, high-pass where excursion becomes a problem either because of IMD or xmax or both. The goal is to run the mains as low as possible for modal smoothing.

The improvements from flanking subs and multisubs are measurable and audible. The effect is anywhere from subtle to striking, but it's always noticeable. Flanking subs make the upper midbass and lower midrange smoother. Male voices, piano, guitar and cello sound clearer. Distributed multisubs make the deep bass smoother. You will notice bass notes that seemed light or even missing before. Sounds like a better foundation.
Re: 4PI Plans Request [message #91247 is a reply to message #91245] Mon, 09 December 2019 14:59 Go to previous messageGo to next message
mathiasb is currently offline  mathiasb
Messages: 6
Registered: December 2019
Location: WA
Esquire
Wayne Parham wrote on Mon, 09 December 2019 12:25
I think that's a good way to go. Run the flanking subs with a 100Hz/2nd-order low-passed copy of the signal sent to the main speaker each sub is flanking. Run the mains set to "large" so you blend with the flanking subs. The mains should be able to handle the LF content unless they just really can't handle the low notes or you are pushing them close to their limits. If you're pushing them hard, then high-pass them at their Helmholtz frequency.

This Helmholtz recommendation is, of course, relevant for vented systems. Above the Helmholtz frequency the vent reduces excursion, but below Helmholtz the woofer is unloaded. If sealed, it's not such a stark a change in excursion but then again, there is no reduction of excursion from the vent. So for sealed woofers, high-pass where excursion becomes a problem either because of IMD or xmax or both. The goal is to run the mains as low as possible for modal smoothing.

The improvements from flanking subs and multisubs are measurable and audible. The effect is anywhere from subtle to striking, but it's always noticeable. Flanking subs make the upper midbass and lower midrange smoother. Male voices, piano, guitar and cello sound clearer. Distributed multisubs make the deep bass smoother. You will notice bass notes that seemed light or even missing before. Sounds like a better foundation.

Totally agree (not that facts need agreeing) about multiple subs, I run two now, independently.

I'd have to get a second amp to do this, so I can DSP the front speakers - however, quick question on the low pass for the subs - how come 100Hz, and not, say, 80, or 120? Is that based on Pi4 (would make sense), or just a starting point in general?
Re: 4PI Plans Request [message #91248 is a reply to message #91247] Mon, 09 December 2019 16:45 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17639
Registered: January 2001
Illuminati (33rd Degree)

The flanking sub low-pass recommendation of 100Hz second-order is empirical, so you can consider it a starting point and not a hard-fixed number. However, I have found that the slope is always better being gradual than it is being sharper. Fourth-order slopes are too steep. I have also found that low-pass below 80Hz is too low for flanking subs. The range of 100Hz to 120Hz and sometimes as high as 150Hz seems to work best. Much higher than that and the subs become localizeable and draw attention to themselves.

The low-pass and amplitude of flanking subs is set by simultaneous optimization of three things:

1. Amplitude level-setting the subs to the mains, so we gain bass extension at the appropriate SPL. This usually amounts to about 10dB more gain on the subs, because they are usually about 10dB less efficient than the mains.

2. Low-pass that conjugates baffle-step. Cabinets the size of my three Pi and four Pi mains tend to have baffle step in the 100Hz to 200Hz region. Instead of employing compensation in the crossover, we use the flanking subs to provide additional SPL as BSC.

3. Low-pass that mitigates higher-frequency room modes and SBIR from nearest boundaries. The worst anomaly usually comes from the wall directly behind the speakers, but the nearest side wall is sometimes objectionable too, as can be floor bounce. The modal region extends above 100Hz, but distant multisubs cannot be run this high without being localizeable. And the boundary interference notch from the wall behind the speakers seems to almost always be between 80Hz and 120Hz, probably because proximity to the wall behind the speakers is most convenient and/or popular in this range of a few feet. So this makes it useful to have a truncated array in the 80Hz-120Hz region, to counter the interference notches there. The flanking sub and the midwoofer in the mains form a simple two-element array.
Re: 4PI Plans Request [message #91257 is a reply to message #81341] Fri, 13 December 2019 20:37 Go to previous messageGo to next message
Sion is currently offline  Sion
Messages: 1
Registered: December 2019
Esquire
Wayne,

After some amount of web surfing, I could be able to reach at here while reading many good reviews on the pi speakers.
I'm starting to think about setting up Hi-Fi audio system again in my house. More than 20 years ago, I used to build vacuum & solid-state amplifiers including one pair of speakers. So, I'm thinking of DIYing both amplifiers and speakers again even though I'm not confident on wood DIYing...

I have couple of questions.
1. Kit means that all the components are provided except for the boxes. So, I need to build the box with some good wood engineering skill.
2. A good quality wood can be purchased at stores like home depot?
3. Can I get advice from you while building the speaker boxes? or do you have very detailed instructions?
4. I can see some upgrade options for the components for the 4 pi kit. Do you have any sweet spot for the selections?

Finally, I would be very grateful if you could send me a set of the 4 pi plans (this means drawing and instruction?).

Merry Christmas and Happy New Year!

Thanks in advance,
Sion
Re: 4PI Plans Request [message #91260 is a reply to message #91257] Sat, 14 December 2019 09:53 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17639
Registered: January 2001
Illuminati (33rd Degree)

You've got mail!

Kits include the speaker drivers, the connector panel, hook up wires, "π" logo decal and a printed copy of the plans. For larger speakers that incorporate a compression tweeter and crossover network, kits also include the crossover, Zobel woofer damper, and all cable assemblies are completed and ready to install. Every kit containing a compression driver also includes the horn flare and the bolts to mount the driver to the horn.

I recommend using only MDF or Baltic Birch. You will probably want to purchase wood at a quality lumber yard, because the large chain retail hardware stores do not usually stock MDF or Baltic Birch. They only sell cheap plywood products and chipboard. Both of those are suitable for many construction projects, but not for loudspeaker cabinets.

Please peruse the Pi Speakers FAQ. I think you will find the answers to all of your questions there, as well as answers to many things you haven't thought to ask yet. The FAQ has information about upgrade options, the differences between models and upgrade choices, build and setup advice and other useful things. And as you start your build, please feel free to document it here and ask questions or make comments along the way.
Re: 4PI Plans Request [message #91266 is a reply to message #81341] Sun, 15 December 2019 21:12 Go to previous messageGo to next message
Valentino Beach is currently offline  Valentino Beach
Messages: 1
Registered: December 2019
Esquire
Hello Wayne,

Have been following your 4PI design with great interest for over a year now.
Finally I have purchased a pair of 2226H JBL drivers for this project.
Can you please send me a set of plans to build these speakers.

Thank you,

Gil
Re: 4PI Plans Request [message #91268 is a reply to message #91248] Sun, 15 December 2019 22:12 Go to previous messageGo to previous message
mathiasb is currently offline  mathiasb
Messages: 6
Registered: December 2019
Location: WA
Esquire
Wayne Parham wrote on Mon, 09 December 2019 16:45

The flanking sub low-pass recommendation of 100Hz second-order is empirical, so you can consider it a starting point and not a hard-fixed number. However, I have found that the slope is always better being gradual than it is being sharper. Fourth-order slopes are too steep. I have also found that low-pass below 80Hz is too low for flanking subs. The range of 100Hz to 120Hz and sometimes as high as 150Hz seems to work best. Much higher than that and the subs become localizeable and draw attention to themselves.

The low-pass and amplitude of flanking subs is set by simultaneous optimization of three things:

1. Amplitude level-setting the subs to the mains, so we gain bass extension at the appropriate SPL. This usually amounts to about 10dB more gain on the subs, because they are usually about 10dB less efficient than the mains.

2. Low-pass that conjugates baffle-step. Cabinets the size of my three Pi and four Pi mains tend to have baffle step in the 100Hz to 200Hz region. Instead of employing compensation in the crossover, we use the flanking subs to provide additional SPL as BSC.

3. Low-pass that mitigates higher-frequency room modes and SBIR from nearest boundaries. The worst anomaly usually comes from the wall directly behind the speakers, but the nearest side wall is sometimes objectionable too, as can be floor bounce. The modal region extends above 100Hz, but distant multisubs cannot be run this high without being localizeable. And the boundary interference notch from the wall behind the speakers seems to almost always be between 80Hz and 120Hz, probably because proximity to the wall behind the speakers is most convenient and/or popular in this range of a few feet. So this makes it useful to have a truncated array in the 80Hz-120Hz region, to counter the interference notches there. The flanking sub and the midwoofer in the mains form a simple two-element array.

I'm having difficulty finding a good high pass for the mains. Considering they'll be getting a full range signal I want to protect them. The tuning is around 50Hz. With a sub LPF of BU2 100Hz, is BU4/BU3 HPF at 50-60Hz a good start for the mains? After that - there's the playing around with the delays to get the sub and speaker to integrate, before even looking at EQ.
Previous Topic: Flanking subs
Next Topic: For Sale: 4 Pi speakers (upgraded drivers) + pair of 3pi flanking subs
Goto Forum:
  


Current Time: Sat Jan 18 09:29:01 CST 2020

Sponsoring Organizations

DIY Audio Projects
DIY Audio Projects
OddWatt Audio
OddWatt Audio
Pi Speakers
Pi Speakers
Prosound Shootout
Prosound Shootout
Smith & Larson Audio
Smith & Larson Audio
Tubes For Amps
TubesForAmps.com

Lone Star Audiofest