[David Ellis]

I chatted with Thilo at TC Sounds a few days ago.  It was educational and provided optimism.

The tentative woofer @ 1 year ago with a cloth surround didn't function as hoped.  The surround had to be very hard/dense to function properly.  The result was a VERY low VAS and commensurately low sensitivity.  So, Thilo knew this wouldn't work and had no "perfect" solution for me.

Currently, Thilo expressed an interest in conveying/purveying another motor project.  I don't know what it is, and it seemed experimental in nature.  Thilo only conveyed that the results should be superior to an underhung motor.  I find this encouraging.  Hopefull I'll have something in a few weeks.  My only concern at this point is having a very compliant & soft surround.  This is necessary for high VAS and high sensitivity.

Dave

[JoshK]

I would probably lean towards a rubber surround.  I think the fear of it rotting away isn't justified since you can replace them easily enough and many don't have their drivers that long anyway.  I think rubber surround is spse to be superior to cloth in a few ways.

[David Ellis]

The initial hope was the cloth would have very good longevity and be very light and pliable. This didn't matriculate.

Foam is actually a very good material for a surround, and there are some very long lived foam surrounds constructed nowdays.  A while ago I spoke with a gentlemen that manufactures surrounds in the USA.  He conveyed that one of their foam surrounds has a 10 year guarantee under ANY conditions.  I was very surprised about this.  Certainly a common/cheap surround used for an automotive woofer placed in humid/salty air would have a life expectency of @ 2 years maximum.  Offering a 10 year guarantee under these conditions seems absurd for an "average" foam surround.  But, new chemistry has made a very positive impact. 

Also, it seems like foam surrounds are making somewhat of a comeback.  Many automotive subwoofers use foam surrounds, and I don't think this is a mistake from a durability perspective.  I have seen several 20 year old speakers with perfect foam surrounds.  Certainly there is a fair percentage of rotten surrounds on old speakers too.  The difficult part in all of this is that consumers can't discern the difference.  Getting a good foam surround is certainly a major boon.

However, for me, if the VAS of the prototype rubber surround is high enough, and the surround manages to control/damp any cone wobble, a rubber surround will be used.  This is primarily because rubber WILL live forever, and folks spending big $$ on speakers want something that will last for 20-30 years.

Dave

[JoshK]

   I said rubber, but meant foam.     Rubber can be good too, but I was meaning foam. 

[Guilhermejs]

Any new subwoofer recomendations for 1801b?

[David Ellis]

Unfortunately, the SCC300 is gone .

My choice would be the TC1000, but this is only due to their excellent reputation and the high VAS of the TC1000.  It looks good on paper, but I have never heard this particular driver.

http://www.tcsounds.com/tc1000.htm

Larger VAS/Cabinet subs will be more sensitive (or have deeper bass).

Alternately, I recommend you simply call TC sounds, describe your application and desires.  They will recommend an appropriate driver.

Dave

[Guilhermejs]

Dave,

      What do you think about using the Meniscus 8'' as a 3a way on a floorstander version of the 1801b? I thought about using it on a transmission line cabinet.

Regards,

Guilherme

[David Ellis]

I have mentioned previously that the 8" Meniscus is produces wonderful bass in a ported cabinet.  My sentiment remains very true in this regard.  And, the best part is the Meniscus 838 is not very expensive.  I don't recall the exact Qts number for my drivers, but believe it was @ .40. 

I believe that a TL or TQWP may sound marginally better than a ported cabinet, but the TL or TQWP cabinets are considerably larger.  The size and mass of these cabinets is the primary reason folks don't implement them.

Dave

[Guilhermejs]

Dave,
         

Do you think that a sealed 1801b would be better in this case? What enclosure size do you recomend?

Guilherme

           

[David Ellis]

Do you think that a sealed 1801b would be better in this case? What enclosure size do you recommend?

It should be theoretically better, but the impact may not be audible.  The sealed 1801b cabinet should be about 16 liters. 

However, if you already have a larger 21 liter cabinet constructed, this will be fine too.  Simply stuff the port with a sock.  Prefer a good Champion sock, but I am certain that other brands will perform admirably too.

Dave

[goldlizsts]

Do you think that a sealed 1801b would be better in this case? What enclosure size do you recommend?

It should be theoretically better, but the impact may not be audible.  The sealed 1801b cabinet should be about 16 liters. 

However, if you already have a larger 21 liter cabinet constructed, this will be fine too.  Simply stuff the port with a sock.  Prefer a good Champion sock, but I am certain that other brands will perform admirably too.

Dave

A silly comment.  When I was at a famous designer's home, we experimented both ways.  The "tightness" of a sealed cabinet was very obvious.  So I ran with a sealed cabinet tho I was told I could go with a port, and could later stuff it with a sox if I changed my mind.  Never looked back.  I often test a speaker's bass with the Reference Recording's Fanfare for the Common Man track.  If a speaker's bass performance is good, it would become very obvious when the drums come on, right at the head of the track.  From my experience, a sealed cabinet still gives a far superior bass (in terms of tightness, at least in my case).  Of course, one'd lose that 5-10 Hz below.  I often thought hat most speakers are ported because of the intention to get that extra few Hz below.  This is my personal user's experience, not meaning to challenge anyone's opinion.  My hi-fi knowledge is limited.

[David Ellis]

A silly comment. 

I disagree.  I think this comment is very good.  Also, I must convey that your Reference Recordings sample track is a good choice.  I have this recording, albeit on a Chesky label.  The drum is very clear and easily discernable.

If I could design a perfect speaker, it would have a larger sealed woofer of good sensitivity.  The theoretical dampening advantage of a .7qts (or lower) bass system is obvious and audible.  However, for the 1801 the sealed version failed as as a stand alone monitor.  Neither Dennis or I preferred this version - despite the theoretical advantages.

I believe this outcome is rooted in 2 possible variables.  First, the sealed 1801 (and all sealed speakers), require more excursion in the bass region above the tuning frequency.   The 1801 tuning frequency is 34hz.  Folks often tout the problems with ported woofers when they unload, but this happens below (not above) the tuning frequency.  Second, the 1801 lost 10-15hz of bass extension.  Somewhere in these two possible variables, the 16 litre sealed 1801 lost in a/b comparison with the ported 1801 as a stand alone monitor.

However, Guilherme's proposition was for something in a 3-way application. With a filter circuit on the woofer, the impact of the ported versus sealed cabinet dissipates.

and

My hi-fi knowledge is limited

IMO, if you are listening to that music and making these discernments you have profoundly good hifi knowledge aa.  Few folks have a mental memory firmly grounded the sound of live unamplified music.  IMO, this is far more important than being able to recall all of the Stereopile Class "A" components, opamp slew-rates,  vacuum tube compatibility, or schematic diagnosis.

Dave

[Guilhermejs]

I have finished a DIY subwoofer with two NHT10 woofers, parallel on a sealed enclosure.

I'll test it on my system using a active crossover, crossed at 80hz initially. After completing the adjustments of the subwoofer with the system, I'll test the 1801b sealed on the 22L enclosure, and then adding wood pieces until it reaches 16L. This test will take a few days and I'll be on a trip next week, so I will post my coments in a few weeks!

Thanks

Guilherme

[David Ellis]

My hunch is that you won't hear any impact when adding lumber to fill your current cabinet.  However I do suggest experimentally adding some fiberglass insulation (sound absorption) to the midrange cabinet.

I look forward to your comments.

Dave

[Guilhermejs]

Dave,

         I'm designing my floorstander with 1801b sealed + Meniscus 8" in transmission line, and I thought about inclining the baffle so the tweeter magnet will be in the sabe distance of the midbass baffle.

I have seen this in many speakers, is there any reason why you didn't use this method in your speaker? Plus, what do you think bevel the baffle?

I mean something like this:




Thanks,

Guilherme

[David Ellis]

This is a good question.

Tilting the speaker backwards may make the crossover easier to design.  This isn't always true, but seems that it is often true.  Minimally, there is absolutely nothing wrong with a backwards leaning speaker.

I think the bevel looks nice.  Certainly Avalon has marketed this appearance very effectively.  However, the 1801 was designed with a flat baffle and a slightly rounded edge on solid lumber.  The primary reason for the rounded edge or beveled edge is appearance.    While there are theoretical advantages to larger roundovers, their audibility is very questionable.  Aesthetics are the primary motivator IMO.

Off axis 90 degrees I heard surprisingly positive effectiveness from a completely round cabinet created by Wayne Wendel ( a local gent).  I don't recall having heard this in other speakers.  When moving off axis the sound quality of most speakers will decline notably.  However, there are a few potentially mitigating concerns.

1.  We didn't have the same drivers and optimized crossover in a rectangular cabinet for comparison.

2.  Perhaps the extreme off axis signal from a loudspeaker doesn't matter or SHOULD be distorted?   After all, folks go to great effort to absorb/disperse the in-room off axis reflected signal from a loudspeaker.

Dave

[Guilhermejs]

Dave,

       So the 1801b crossover needs to be changed to use a inclined baffle?

Thanks for the reply

Guilherme

[David Ellis]

Code: [Select]

So the 1801b crossover needs to be changed to use a inclined baffle?
 
Yes.

Dave