[IanS]

Has anyone done a transmission line version of the 1801?  The Thor is based on the same woofer, so it would seem you could use a similar cabinet design, maybe a bit smaller for the 1801?  

Maybe this wouldn't be significantly better than the 1801f, so its not worth trying, but I know a lot of people are huge fans of TL enclosures, and its clearly been done with this woofer, so I thought I would mention it.  

If this has already been discussed, just forward me to the thread, but I couldn't find it with search.

-Ian

[David Ellis]

I don't recall anyone executing a T-Line or MLTQWP using the 1801 drivers.  If you wish to attempt this - no problem.  I decided against this because that size cabinet is expensive to build and ship.  Using a real woofer is much smarter use of that cabinet volume.  However, for a DIY guy attempting to build a big cabinet there is good theory supporting loudspeaker pipes.  

I suggest you read this:

http://home.hetnet.nl/~geenius/Optimo.html

And this:

http://www.t-linespeakers.org/projects/martin/MLTQWT/

This was good, but I didn't think it warranted the extra effort:



Hopefully this helps.

[IanS]

The Thor is the kit I was thinking of which offered the W18 in a TL enclosure.  http://www.madisound.com/thor.html  

I hadn't considered it until the 1801f design came out, and I agree it would only be reasonable as a DIY option.  I thought it might offer slightly better bass for those considering the 1801f in a similar cabinet.  

Thanks for the links.  

-Ian

[David Ellis]

I knew exactly what speaker you were considering.  

One note of caution.  The character of bass will change with the various cabinet configurations.  A few folks have remarked that the Thor did not meet their needs due to lean bass.  I must admit that rooms tangible impact.  Listeners also have subjective impact in this matter.  

The truth I wish to convey is that the bass character will change dramatically with cabinet configuration.  While Joe D' is one of the premier loudspeaker designers in the world, the Thor bass might not meet your needs.  In this regard, I suggest you read the remarks from Tony Gee on cabinet configurations and.... experiment.

Since nobody has implemented the 1801 in a pipe, you might consider a ported enclosure.  They work quite well.  Most truly high end speakers use a ported enclosure.  If nothing else, your experimentation with a ported enclosure will provide a very good base-line reference for the pipe configuration you construct.

[IanS]

Thanks for commenting.  I probably will not mess with success quite honestly, I just wanted to get your opinion on the TL, since I hadn't seen it before.  

Everyone seems to agree that the 1801b is better than the sum of its parts, which are already very nice

-Ian

[Al Garay]

Is there a good reason why most high-end speakers are ported as opposed to sealed?

Al

[ooheadsoo]

Higher Q gives punchier bass, better impact?

[suits_me]

I don't know if they're good reasons, but speakers are ported to gain the extra efficiency and a few extra hertz to the -3db point, at the cost of poorer measured transient behavior at the low end, a more difficult impedance curve, a faster roll off from that -3db point, as well as possible port noise. I'm sure there's more to it than just that.

Apart from lacking the benefits of ported designs, acoustic suspension designs have to deal with the increase in air pressure in the cabinet when the woofer moves in. Some say this can negatively affect sound quality.

I've heard TLs I really like, but they are usually expensive to manufacture and difficult to design.

[David Ellis]

I don't know if they're good reasons, but speakers are ported to gain the extra efficiency and a few extra hertz to the -3db point, at the cost of poorer measured transient behavior at the low end, a more difficult impedance curve, a faster roll off from that -3db point, as well as possible port noise. I'm sure there's more to it than just that.

These are very good reasons, and a very good basic understanding of the ported enclosure.  Yep, sure, you betcha!

Apart from lacking the benefits of ported designs, acoustic suspension designs have to deal with the increase in air pressure in the cabinet when the woofer moves in. Some say this can negatively affect sound quality.

This, however, is er... a backwards.  I too misunderstood this for several years.  The ported enclosures actually have more "spring" on the driver than a sealed enclosure.  This seems very counterintuitive.  Further, the associated terms for ported enclosure such as "underdamped" can create confusion.  I'll try to explain.

Consider that any loudspeaker driver (in a cabinet) has spring and dampening just like a car suspension.  In the case of a speaker the dampening comes from almost completely from the driver.  The spring comes from the driver AND cabinet.  Sure, there is pressure against the driver in a sealed enclosure.  However, this pretture comes on slowly as the frequency drops.  With a ported enclosure, there much more significant pressure above the tuning frequency.  This creates an oversprung situation.  Relatively speaking (no pun intended) the system is underdamped.  The ported cabinet is more spring than damping force above the tuning frequency.  With a ported cabinet there is actually more spring than in a sealed cabinet above the tuning frequency.  The Q of the "idea" ported cabinet is 1.  The "ideal" Q of a sealed cabinet is .707.  The sealed cabinet has LESS spring with the same damping.  This makes for a better damped system.  It is further possible to lower the spring of the sealed system by making a larger cabinet and a "low Q" system.  Such a cabinet would have even less spring with the same damping.  It might have a Q of .55-.65 .  Many say this is "ideal".  

Typically all sealed cabinets will have a lower Q than ported cabinets.  However, it is possible to give a sealed cabinet more spring by making the cabinet VERY small.   This could bump the Q of the sealed cabinet above 1.

One of the very real adantages of the ported cabinet is the woofer travel.  The woofer travel of a ported cabinet is more firmly limited above the tuning frequency.  This is a very real consideration when max spl is considered.  Ported cabinets are much easier on the driver X-max for most practical applications.  Even the 1801 has a tuning frequency of about 34hz.  Clearly 99.99% of music is above this 34hz.  The ported cabinet enables more spl with the same driver X-max.

There are further considerations in this realm, but my remarks will hopefully suffice.