Originally Posted by btinindy
Hi John, I am interested in your thoughts. I currently have a TD15M with a SEOS 12 (soon to be a SEOS 15 then soon to be a SEOS 18). I am interested in adding these 18's to the mix. I would go passive on the CD and use the minidsp to go active between the td15M and the 18. Where would you recommend crossing these? What sized sealed enclosure would you recommend for the 18? The td15m is in a sealed enclosure of about 3 ft^3.
I use this system for movies and music. I would love to be able to run these in two channel mode full range for music.
I have two JTR Captivators for subs so I would be interested in your thoughts on how low the 18's you are selling would optimally be run.
Thanks for your thoughts.
If used in a stereo pair you could go anywhere from 200hz up to 500hz while still keeping about 90 degrees from them. I would typically measure response and see where the baffle rolloff is affecting the TD15M's and then cross right in that area. Most likely somewhere around 250hz.
I'm not sure which Captivators you have. It really doesn't matter too much in this case though.
You have a couple options for the enclosure. For maximum output, a vented enclosure 6-8cf tuned from 28-32hz will give you a massive amount of output and lots of efficiency. You will be able to input close to 1500W while staying within Xmax limits and reach almost 125dB range at 30hz from a single woofer. If you do have this much room available and can go vented, I would suggest taking them as low as possible. The woofers in the Captivator will move more air due to the higher excursion, but I don't believe they have anything done in terms of reducing flux modulation, linearizing inductance, etc. The PB18H+ (TD18H+) is extremely low distortion due to the Lambda motor design and also about 7dB more efficient than the woofer in the Captivator. You could play with the crossover point easily if you are using the minidsp, but I would be willing to bet the PB18H+ will sound significantly better all the way down to 30hz. I guarantee you will hear details in fast bass guitar notes that never seemed to exist before. It will also give you more overall output than the Captivator is capable of all the way down to that point. You could also go smaller, maybe 4 cf tuned to 38hz as another option if that is too big.
Sealed is an option, although you give up output and efficiency and EQ is required to extend the response. The larger you go with the enclosure, the more efficient the low end becomes.
The following shows 18" in 8cf vented tuned to 28hz in green, sealed 3cf in red, sealed 4cf in orange, and sealed 6cf in yellow.
My overall suggestion though is to go vented, as large as you can up to 6-8 cubic foot, then take them down as low as possible.