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Bill - Every speaker driver has a given amount of XMAX. This is a measurements of the excursion capabilities of the driver. It can only go so far in or out before it bottoms out.The deeper a driver plays, the more air it needs to move in order to reproduce the deepest bass. Thus, the more cone excursion is required.Normally, the Seas Excel W18 will play down to about 45Hz in a standard ported cabinet. In the case of the 1801TL, the transmission line extends the bass response down to about 34Hz. With speakers, there is never such a thing as free lunch. For everything you gain, you have to give up something. In this case, because the bass response is extended, more of the total excursion (XMAX) is used up playing this deeper bass. So the speaker can’t handle as much power as it could if it didn’t play quite as deep.When you hear a driver bottom out, that should tell you that you are driving it a bit hard. If you damage the driver in the process, it simply will not play any more.As to why this would happen when the crossover is set to 80Hz, it is hard to say (more variables involved). But one thing I have noticed with speakers of this type is that the distortion levels are so low, you often don’t realize just how loud you are playing them. You are not getting the usual distortion cues that would make you realize it is time to turn it down. So you may simply be playing things louder than you think you are and using up all the available XMAX in the process.A speaker like the Veracity ST or HT2-TL is the solution. Since two woofers share the load, you have twice the XMAX at your disposal.- Jim
I also have an XMC-1 room correcting preamp. I think I know what your problem is. The XMC-1 can give up to a 10 db boost at frequencies where the speakers dip due to room cancelations at low frequencies. The XMC-1 will boost the response dip. If you have the full Dirac upgrade, then I would suggest that you put a small dip, in the target curve, at the measured response dips. This would cause only partial filling the lowest dips. Vandersteen recommends that you don’t try to correct the whole amount of large dips with a big boost. Just try to get a good compromise with a smaller boost at the dip points.BobPS Room correcting absorption panels, rugs and resonators that work at the dip frequencies might help, but I know very little about that.
Should SongTowers with two 5" woofers handle higher volumes than the 1801tls with a single 6" woofer? I still have my SongTowers and will have to see if they handle the louder volumes better.Bill
I think they might. If you look at Paul Kittinger's simulations for a lot of speakers, the maximum stress on the woofer isn't confined to the lowest frequencies. Sometimes the woofer exceeds X-max at high volumes in the 80 Hz range. Two woofers in parallel have a big advantage over a single woofer, particularly when it is tuned for low bass reach.
I wanted to look up the excursion characteristics and graph from the modeling I did for the 1801TL in my old emails, but even though I likely have that email, when my computer went South several months ago and everything was transferred from it to my new computer, all embedded modeling graphs in emails didn't make the transfer, only the texts. If Jim (or you) saved or printed out my emails, maybe it's available?Paul
... I have Dirac full but know so little about how to manually manipulate the target curve...
After taking the measurements and before optimizing the filter, Dirac shows the default target curve. You have the option of tweaking the curve before generating the filter. I "think" you just drag the target down at your response dip, although I admit I've always just used the default so I'm not positive.
