In response to your comment, I may be on a different branch of the right track rather than on the wrong track. As Jim points out, equalization can compensate for the bass rolloff of low QTS drivers in open baffle designs (and in sealed enclosures too), giving you the gift of extended bass response without the group delay and other disadvantages of a ported box. Good idea if you're using multiple high quality woofers, like those in the Orion, that can handle the extra power needed to drive them at low frequencies.

I was looking at some drivers in WinISD, using a 1,000 sq ft "sealed" box to mimic an open baffle. The Eminence Delta 15LF, with a .58 QTS has an F3 of about 51hz - not too bad. The Silver Iris, with its .98 QTS is an even better candidate. Its bass rolloff begins at a much lower frequency than the Delta LF, which would provide more midbass punch, and its F3 is about 35hz. So now I'm beginning to understand why hurdy gurdyman is so enthusiastic about the Silver Iris driver.

It is my premise (true or not, it's mine) that despite what WinIsd might say a high Qts driver is providing the impression of extended base response by flapping in the breeze. It is not providing an accurate representation of the input signal.

As I noted in my original post (assuming that sound quality was important) if you want to go the OB route you have to be prepared to EQ and it's almost mandatory to bi-amp to get the needed degree of driver control.

OTOH, if your primary concerns are (personally) satisfying reproduction at minumum investment and not fidelity (which is a matter of personal preference) then I would agree that a high Qts driver is the way to go. But I would also contend that concerns as to how Driver A compares with prized classic Driver B should not be among your criteria for driver selection.

Retsel

Before this, I used vintage high Q EV drivers in OB. Sounded great down to the 80 Hz baffle cut-off.

Nobody would ever call call any of these drivers slow or distorted. The sound was very good, and the cost downright cheap!

Dave

My enthusiasm is higher than ever. I visited Darrel Hawthorne and listened to his set-up. He has bigger room designed for music listening. The sound was incredible! I have never heard a better sounding home system. Everything was so natural. I'm seriously looking at ways to make a better listening enviroment at home, now. I'm also going to make a wingless baffle. The Silver Iris doesn't need the wings. The high Q drivers sound their cleanest with narrow wingless baffles.

Dave

I have not heard the Silver Iris but I have now changed the woofers in my Lowther OB system to the Eminence Alpha A15 which has a Qts of about 1.2, I updated my site to reflect this yesterday. I think these Eminence drivers are very close (if not the same) to the Silver Iris 15 inch driver. The bass is as you describe, deeper and warmer compared to the lower Qts Dayton drivers I was using before and could easily support a smaller baffle. With my big baffle the bass goes very low for an OB system.

The one difference in the Silver Iris and my system is the location of the crossover point. I am rolling the Eminence drivers out at 200 Hz using a 12 dB/octave filter. Obviously the Silver Iris uses the woofer to a much higher frequency which may or may not be a concern. I will have to play with my active crossover to see how things work crossing over higher. Would you happen to know at what frequency the Silver Iris corsses to the coaxial horn tweeter? But based on my experience with the Eminence Alpha driver, I bet the Silver Iris sounds very good in a "smaller" OB at a great price point.

Martin

The SI driver has a frame like the Alpha, but everything else is different. The cone is covered in concentric rings from one edge to the other. The Qts is around 0.9. The XO point is around 2500Hz, give or take a few.

The origional speaker that Darrel Hawthorne done his experimenting with was an Alpha. The results were so good that he worked with Eminence to develop a coaxial driver with all the strong points of the Alpha but even better suited for OB coaxial use. The engineers at Eminence came up with the present Siver Iris, which seems to be a great OB speaker. Those that have the origional XO really need to get the new one to really hear what these drivers can do. The origional XO had some serious problems. It was not an Eminence design, BTW, but from an independant company.

I'm keeping my SI for a long time.

Dave