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Re: Hardwood floor [message #51336 is a reply to message #51333] Thu, 09 August 2007 19:28 Go to previous messageGo to next message
j.luis is currently offline  j.luis
Messages: 22
Registered: May 2009
Chancellor
Hy ..Tim . What woofer do you have in the 7 Pi bass bin ..Thanks

Re: Hardwood floor [message #51337 is a reply to message #51336] Thu, 09 August 2007 19:46 Go to previous messageGo to next message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron
Absolutely standard build to Wayne's specifications - the woofer is the JBL 2226H.

tim

Re: Pi Sevens up and running! [message #51340 is a reply to message #51320] Fri, 10 August 2007 00:29 Go to previous messageGo to next message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron
I ran a frequency test in my living room tonight with my Radio Shack meter and the test tones from realtraps.com - the results are as follows:

* Audible response below 20Hz if I turn up the wick a bit.
* Real response seems to start at about 25Hz - small peak at 26Hz.
* Up another 10dB by 35Hz.
* Up to "average" levels by 46Hz - 15dB above the 35Hz figure.
* Small peaks at 67Hz, 100Hz, 160Hz and 290Hz.
* Response drops at 85-95Hz, 110-150Hz, 230-270Hz.
* Narrow suckouts (down 8-10dB) at 110Hz and 270Hz.

This is with three bags of R-19 - two under the piano and another hiding under a coffee table.

I'm a bit surprised there's not more bass in the 25-45Hz range - is this the result of inadequate corners, perhaps?

I can also hear a certain amount of vibration - not sure of every cause, but I could identify a shelf and a table and some CDs as a start. Also the floor vibrates, and I wonder if I should isolate the speakers from the floor?


Re: Easy to add Post-assembly Bracing [message #51341 is a reply to message #51335] Fri, 10 August 2007 08:27 Go to previous messageGo to next message
Skip Pack is currently offline  Skip Pack
Messages: 51
Registered: May 2009
Location: Hollister, California
Baron
I imagine it would be a good thing if you could use some
closed cell foam or something like that put the brace/rod
under a reasonable amount of compression. Perhaps you
could take a square of mdf, drill a hole in the center,
and glue it to the inside of the back panel centered on the
woofer cutout. you could then put a thin amount of the foam
in the hole then tighten the woofer mounting screws against
rod/dowel going from the hole to the back of the driver.
You could judge the force adjusting the thickness of the
foam to make it snug without putting too much stress on
the woofer frame or the mounting screws.

As I said I haven't done this, but I do put four of the dowels
around the woofer cutout to localize the panel reaction to
the woofer acceleration.

Skip

Re: Pi Sevens up and running! [message #51342 is a reply to message #51340] Fri, 10 August 2007 09:32 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18670
Registered: January 2001
Illuminati (33rd Degree)

The 2226 is an excellent woofer, one of my favorites for the seven π. But it's not tuned for subwoofer use, and doesn't reach the 20Hz-30Hz range. As you've noticed, there's usable output from 30Hz up but bass starts to rolloff about 40Hz. The system is tuned to have a slightly overdamped alignment for corner loading. Corner loading brings up the bottom end and the overdamped alignment prevents a midbass peak.


Re: Super-tweeter [message #51346 is a reply to message #51334] Mon, 13 August 2007 10:16 Go to previous messageGo to next message
dB is currently offline  dB
Messages: 234
Registered: May 2009
Master
I am going to post a good site on ribbons very educative, watch for the main thread. In the mean time you can ask if Wayne plans in using them in the future and what he thinks if he has anything in view.
Also watch for beautiful Fostex's not far way in price ($50's/$100's), FT17H/FT96H that is if you can handle.

Regards


Re: Pi Sevens - almost finished! [message #51349 is a reply to message #51315] Tue, 14 August 2007 01:13 Go to previous messageGo to next message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron

I've turned them around against a different wall and finished the veneering (although they still need finishing). This seems to work better as they have more room to breathe. The treble seems improved, which is a surprise, and the overall balance is better too. As you can see from the picture, they are sitting on my hardwood floor, which is less than ideal.

They don't have any feet or isolation of any kind - any ideas as to what I should do there?

The crossover is still loose, and needs a box, and I plan to remove the shelves and build something more effective for CD storage so the speakers are truly in the corner.

I'm constantly amazed at how much more I'm hearing from all my records. It's hard to stop listening - which is the point, I guess


Hey Tim. [message #51352 is a reply to message #51349] Thu, 16 August 2007 11:11 Go to previous messageGo to next message
j.luis is currently offline  j.luis
Messages: 22
Registered: May 2009
Chancellor
Hy..Tim .How compare your new speakers against the older ones ..thanks

Re: Hey Tim. [message #51353 is a reply to message #51352] Thu, 16 August 2007 15:47 Go to previous message
Tim Barnes is currently offline  Tim Barnes
Messages: 46
Registered: May 2009
Baron
Some information in my previous post (referenced below).

The increased efficiency is the first and most obvious difference. The second is the increased sense of ease and detail in the mid-range. I am hearing a lot of new information. The difference between CDs and LPs is even greater than before - with LPs clearly preferable.

The corner positioning and perhaps the use of horns seems to lead to a couple of changes - more air movement and sense of being involved in the sound which is a good thing. The precise imaging I was used to is not really present any more. I feel there's a bit of a hole in the soundstage towards the center. But there's a benefit too - the sweet spot is much bigger. I can sit in many places in the room and still enjoy a balanced sound.

There seems to be a shortage of low bass with the Pi Sevens, but very good and clear and unfussy mid-bass. The Thiels use a passive bass radiator which gave quite a lot of bass - especially if the speakers are anywhere near a corner.

The Thiel cabinets are much more rigid than the Pi Seven bass cab - double or triple thickness baffle, lots of internal bracing, smaller panels. I never felt any vibration of the Thiel cabinet, but I can detect vibration on the front of the Pi. I plan to take the drivers out and beef up the internal bracing.

The treble is clearly less than with the Thiels, but it's clean and sweet. I might investigate a super-tweeter, but we'll see. The integration between the treble and mid-range seems to be perfectly seamless from anything more than a couple of feet away.

One reason the Pis work well for me is that my amp is a Music Reference RM9 tube amp that is not really at its best into very low impedances. The Thiels go below 2 ohms at certain frequencies, which in addition to their low efficiency makes them tough to drive. A transistorized amp was better at the bass, but worse at the mid-range. With the Pis I can get a good overall performance with my tube amp.

Let me know if you have any more specific questions - I'm still learning about the speakers and I'm sure my views will continue to evolve.

My net conclusion is that they were well worth the trouble to build, and a very satisfactory improvement on the Thiels. I wish they were smaller.

Regards,
tim


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