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3pi vs. 4pi [message #66818] Thu, 31 March 2011 21:40 Go to next message
mike_2008 is currently offline  mike_2008
Messages: 7
Registered: March 2011
Esquire
Wayne: I am sure that you probably answered this question previously, but I was unsuccessful in locating a previous thread.

First, I know very little about speaker building, but I do understand that the more you spend on drivers the better the sound quality.

If the Standard 4Pi with the upgraded driver is a 9 (on a 1 to 10 scale), how would you rate the following:

- Standard 4Pi Eminence Omega 15
- Standard 3Pi Eminence 12LF

I am just trying to get a sense of the cost vs. benefit. Obviously, the Eminence 12LF driver is the least expensive driver. I do understand that you recommend using multiple subs. If you used multiple subs, could you get away with the Eminence 12LF driver and still get great Home Theater results.

I appreciate your response.
Thanks
Options in a nutshell [message #66826 is a reply to message #66818] Thu, 31 March 2011 23:40 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17869
Registered: January 2001
Illuminati (33rd Degree)

It's all about the midrange, when you're talking differences between the JBL 2226 and the Eminence Omega 15. The Omega 15 sounds very good, powerful yet still natural sounding. But it isn't as good as the JBL woofer. The 2226 uses a flux control ring, which reduces distortion. It makes the midrange sound clearer and it reduces listening fatigue.
The same kinds of things could be said of the Definimax and the Delta woofers. The Delta 12LF is a nice woofer, gets very loud and still maintains composure. But it isn't as good as the Definimax, which uses a flux control ring.

I'm not going to do the "rate on a scale of 1 to 10" thing, because I don't think that will give you a clear picture. Instead, I want to give you a (very) brief explanation of what you gain with each improvement. You can also read the whitepaper below to get a little more explanation of the technologies used in these loudspeaker systems and how I recommend they be used.
Like I said above, the JBL and Definimax woofers have flux stabilization rings, so their distortion is lower and midrange is clearer. The good/better/best improvements in the mains are about midrange quality and sometimes power handling. Powerful woofers like these are loafing at hifi and even home theater levels, which really helps quality because they aren't strained. So midwoofer upgrades aren't about the low bass. That can really only be improved with multisubs.

Even if you have stereo main speakers that are capable of clean, extended bass response, without multiple subs, the in-room response will be lumpy. The reason is standing waves inside the room cause peaks and dips throughout the room. Bass will be stronger at some positions than others, and it's different for every frequency.

Room modes are strongest in rooms with rigid walls (like concrete, rock, stucco or brick). Well damped rooms aren't as bad (like those with framed drywall construction and a lot of furniture) but you'll still improve response with multisubs. Put a speaker that is perfect outdoors in a room with rigid walls and you'll see peaks and valleys up to 20dB below 100Hz. Most framed drywall homes aren't this bad, but you should still expect 10dB fluctuation in the modal region.

Multisubs obviously don't help the midrange above 200Hz or so. That's where the improved midwoofers in the mains help you. But they can be used to help the lower midrange between 100Hz and 200Hz, if needed. When you put matched-directivity two-way speakers on stands to get them up to ear level, the vertical height creates a floor reflection that introduces a self-interference notch around ~150Hz. So if you put your two-ways on stands, I recommend placing a sub on the ground beside and slightly behind each one. Low-pass the sub around 90Hz to 120Hz so there is still some output in the lower midrange, blending with the mains. These flanking subs will smooth the floor bounce notch as well as other room modes.

The constant directivity cornerhorns don't need flanking subs, because the midhorn and woofer are blended between 100Hz and 300Hz. They don't suffer a floor bounce notch as a result. They are also tightly packed into the corner so there is no front wall or side wall reflection. Flanking subs for the two-ways are placed slightly beside and behind the mains to help smooth the wall reflection, which acts sort of like floor bounce. But the constant directivity cornerhorns don't need this, because they are so close to the boundaries they do not introduce any self-interference.

You can also install subs more distant from the mains, with low-pass frequency set lower (50Hz to 80Hz, depending on distance from mains) to prevent localization. The more distant subs are usually better at smoothing the lowest frequency room modes. If you have a troublesome lower bass peak - which is usually a result of a big above and below in frequency - then putting subs on the other side of the room is the best solution. Two to four subs placed in different locations will average the sound field and make the bass smooth throughout the room.

Re: Options in a nutshell [message #66834 is a reply to message #66826] Fri, 01 April 2011 14:49 Go to previous messageGo to next message
jgoodd8050 is currently offline  jgoodd8050
Messages: 25
Registered: February 2010
Chancellor
Wayne,

What you said about 100hz blending with subs is very helpful to me. How far away from the mains do you usually place the flanking subs?

Thanks Jeremy
Re: Options in a nutshell [message #66836 is a reply to message #66834] Fri, 01 April 2011 15:30 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17869
Registered: January 2001
Illuminati (33rd Degree)

Flanking subs should be just a couple feet away. They're basically at the foot of the mains, and when blended up through the lower midrange, they'll smooth the floor bounce notch. They're sort of making a three-way speaker out of your matched-directivity two-ways, except that not being attached, you have a little more placement flexibility. You can take advantage of this to smooth a couple other self-interference notches too, like the one from the wall right behind the mains. Just move the subs a little bit behind the mains and they will help smooth that reflection notch too.

I generally put flanking subs a little bit below and behind the mains, and perhaps just to the outside (or the inside). Keep them close enough to integrate well, and not betray their position. You're going to run these up into the midrange, even if just barely, so you don't want them to be too far away. But you want them to be offset enough to provide smoothing of the self-interference notches. So put them in between the mains and any nearby reflective surfaces. Something like this:

http://lonestaraudiofest.com/2010/Photos/Dsc_0011.jpg
three π mains with flanking subs

Re: 3pi vs. 4pi [message #66854 is a reply to message #66818] Sat, 02 April 2011 20:07 Go to previous messageGo to next message
mike_2008 is currently offline  mike_2008
Messages: 7
Registered: March 2011
Esquire
Wayne: I just want to thank you for taking the time to respond to my question with a very detailed answer.
Re: 3pi vs. 4pi [message #66871 is a reply to message #66854] Sun, 03 April 2011 09:47 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 17869
Registered: January 2001
Illuminati (33rd Degree)

No trouble, my pleasure. That's what the forum is for!

Re: 3pi vs. 4pi [message #66882 is a reply to message #66871] Sun, 03 April 2011 15:18 Go to previous message
Matts is currently offline  Matts
Messages: 359
Registered: May 2009
Grand Master
I started out with "all-Eminence" Pi 4's and later upgraded to JBL/B&C Pi 4's- and to answer your first question, I'd say both of them are very equivalent in price/benefit ratio. You don't need to rate them anything out of 10- they're both easily worth what they cost. Spend whatever you can afford and enjoy 'em.
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