[billmcc]

I've had a pair 1801tls for close to a year and really like the SQ. An issue I've seen recently is that the woofers have "bottomed out" several times with the volume fairly high. One time was with the 1801tls running full range and then today with surround music with the crossover set to 80 Hz. I can understand the woofers bottoming out in full range at loud volumes but with the crossover on the Emotiva XMC-1 set to 80 Hz it seems odd. Is "bottoming out" the correct term? The woofers make like a chuffing noise that is a little alarming. The volume level isn't insanely high with the level of the XMC-1 at the most at about -10 dB.

I checked all the settings with the XMC-1 and the channel levels are at 0.0 for the left and +0.5 for the right. I'm using Wyred 4 Sound SX-500 mono block amps so I doubt very much that the amps are clipping. Is it normal for the woofers to bottom out on occasion? When it happens and it is brief is there a possibility of damaging the speakers? Thanks in advance for any thoughts on this .

Bill

[jsalk]

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

[billmcc]

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

Jim,

Thank you for your time and very detailed explanation as to why the woofers are bottoming out. It makes perfect sense, especially the suggestion to step up to the Veracity STs or HT2-TLs  .

Bill

[fsimms]

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.

Bob

PS Room correcting absorption panels, rugs and resonators that work at the dip frequencies might help, but I know very little about that.

[billmcc]

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.

Bob

PS Room correcting absorption panels, rugs and resonators that work at the dip frequencies might help, but I know very little about that.

Bob,

Thank you for your thoughts and suggestions . I have Dirac full but know so little about how to manually manipulate the target curve. The Dirac settings could be part of the issue but I also bottomed out the woofers when using Reference Stereo without Dirac. I think Jim is totally correct in that I have the volume level way too high. I'm expecting way too much out of the 1801tls. For the sake of my speakers and my hearing I'll be backing down on the volume a bit. At least I'll try my best .

Bill

[billmcc]

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

[DMurphy]

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. 

[Paul K.]

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 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.

[billmcc]

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

Dennis and Paul thank you for input on my earlier questions. I switched out the 1801TLs for the SongTowers (dome tweeter) and listened to my reference disc (Patricia Barber's Verse SACD) and I prefer the overall SQ of the 1801TLs. The STs might handle the lower bass better but the vocals and midrange of the 1801TLs are better IMO. So I'll watch the volume level till I decide on a pair of Veracity STs or HT2-TLs.

Bill

[avahifi]

Remember that a 3 dB bass boost requires double amplifier power.  Another 3 dB boost requires doubling amp power again and so on.  You can very quickly run out of amplifier and/or speaker capability with an equalizer.

Frank Van Alstine

[toddc2]

... 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.

[fsimms]

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.

Yes, you just double click on the target curve at the frequency that you want to cut and that puts a spot on the line that you can drag down.  FWIW, if you want to reduce the frequency range that is corrected, then you have to delete the spots on the curve near the frequency extremes so you can drag the curtains(edges of the graph) inward. You can't drag the curtains past one of those spots.

Bob

[DaveC113]

Best to work on room acoustics to get rid of the bass nulls before trying to correct, it's not going to work well to use EQ to boost nulls, it takes too much power... I'd see how the speakers perform without the EQ trying to fill the nulls, I bet it'll be much better.

[JLM]

Yes, I run EQ and have always read/been told that it is best used to reduce peaks, not boost dips.  Boost dips as your own risk.  The 10 dB gain mentioned translates into 10 times the power (dB to power is a logarithmic relationship).