[bryanb]

Hi Folks,

Decided to jump in 'cause of the hi-Q of the discussions / topics / and apparently the 1801's.

So, some questions.

I noticed a thread on a sealed 1801b, which seems like a good option for crossing over to a sub. Any thoughts on feasability, xover points, xover recommendations? I wonder if using a smaller enclosure to roll off at about 80 hz would be better than a xover?

I'll probably build a full range eventually, but right now I'm about to start building a sub to get my feet wet.

It has a 3.2cu ft truncated pyramid enclosure that (for the sake of experimentation) is convertable between sealed and ported. Got a Dayton titanic MKII (affordable) which has a fs and qts that put it right between ideal for sealed and ported. Tuning it low with the ported mode (21hz) using dual 27"L x 3" ID ports opening down, driver firing forward. So eventually, I'd like something to replace my trusty old B&W DM12's for something to play with this sub. 1801b's? DM-12's will probably go to the rear.

Re the 1801's- That magnesium cone Seas driver has some resonant modes at about 4500 hz, I believe. Has that caused any audible problem? Guessing the xover is below that.

Right now using a yamaha px-3 tt, yamaha cx-2 pre, yamaha t-2 tuner, adcom gfa-545 and hafler dh-500 amps. Eventually want a lexicon for surround / dolby digital / dts movies. Maybe this 1801b is way over classed for my system.... But the price for parts looks good.

Any comments welcome. Thanks, Bryan

:edit: Actually, I wonder if I can ask Dave Ellis for the information package / plans? thx.

I just checked the T/S parameters of the W18 in WinISD, and it looks like an 11 liter sealed enclosure will give an F3 of ~65 hz with a Qtc of .71. Its also clear this driver is meant for a vented enclosure...

[David Ellis]

Brian,

I am very sorry that I missed your post for so long.  I'll attempt to address your concerns fully.

I noticed a thread on a sealed 1801b, which seems like a good option for crossing over to a sub. Any thoughts on feasability, xover points, xover recommendations? I wonder if using a smaller enclosure to roll off at about 80 hz would be better than a xover?

Using a progressively small enclosure (i.e. less than 16 liters) for a sealed 1801 will create an underdamped, high Q bass system.   The result will be a boomy bass due the excess spring force of the cabinet.  An electronic crossover is much better.  Not only will the roll off be nice and even, but the high pass will thermally unload the W18 woofer.  

I'll probably build a full range eventually, but right now I'm about to start building a sub to get my feet wet.

This is an excellent idea.  Subwoofers are very easy, and those with better drivers are VERY expensive commercially.  I think the SCC300 is a great driver, but it leans towards musical and away from droning boom boom.  Many HT guys prefer the latter and this is fine.  The products from Adire Audio are also very respectable.

It has a 3.2cu ft truncated pyramid enclosure that (for the sake of experimentation) is convertable between sealed and ported. Got a Dayton titanic MKII (affordable) which has a fs and qts that put it right between ideal for sealed and ported. Tuning it low with the ported mode (21hz) using dual 27"L x 3" ID ports opening down, driver firing forward. So eventually, I'd like something to replace my trusty old B&W DM12's for something to play with this sub. 1801b's? DM-12's will probably go to the rear.

Since I have not run the parameters on this driver I cannot vouch for the specifics of your application.  However, 3 cubic feet for a 12" woofer is often correct.

Re the 1801's- That magnesium cone Seas driver has some resonant modes at about 4500 hz, I believe. Has that caused any audible problem? Guessing the xover is below that.

Yep, you are darn near right about the cone resonance.  It's actually centered around 4200hz.  The bummer with any driver is that , "ya can't have yer' cake and eat it too".  ALL truly stiff cones will exhibit a cone resonance.  This is simply because the cone won't flex and absorb the acoustic pressure against the cone.  If the cone flexed the acoustic pressure would be absorbed and gradually retrasmitted.  This is the case with... oh... 99% of drivers.  The other 1% require a nice steep crossover to avoid their cone resonance.  The 1801 is obviously in this group.

Right now using a yamaha px-3 tt, yamaha cx-2 pre, yamaha t-2 tuner, adcom gfa-545 and hafler dh-500 amps. Eventually want a lexicon for surround / dolby digital / dts movies. Maybe this 1801b is way over classed for my system.... But the price for parts looks good.

Well.. probably 50% of my customers have systems similar to yours.  About 10% have very good source electronics.  Probably the only group of people that I grossly discourage are those who dearly love their 70s and 80s rock-n-roll.  These recordings are... uh... very bad.  Some nice soft paper cones are much better with this music - at least to my ears.

Also, the price for parts of commercial loudspeakers would astound you.  7 years ago I was completely ignorant about this.  Now I know better.  The "hook" in the loudspeaker industry is the crossover.  A good crossover can make very average drivers sound very decent.  A bad crossover can decimate even the most expensive drivers.

I just checked the T/S parameters of the W18 in WinISD, and it looks like an 11 liter sealed enclosure will give an F3 of ~65 hz with a Qtc of .71. Its also clear this driver is meant for a vented enclosure...

This isn't quite correct.  First, adding some dcr will bump the Qes and subsequently the Qts slightly.  Second, the Factory parameters are a little off.  Most of the drivers I have measured in the past 1-2 years hover around Qts .39-.42.  

A few folks experimented with sealed cabinets (including me), and found that 16 liters is about right.  If you want to be anal, build the cabinet slightly large (i.e. 17 liters) then add inert material to the inside of the cabinet for tuning.

[bryanb]

Dave,

Thanks for the reply. I know you've been busy; all good things in good time.

Using a progressively small enclosure (i.e. less than 16 liters) for a sealed 1801 will create an underdamped, high Q bass system. The result will be a boomy bass due the excess spring force of the cabinet. An electronic crossover is much better. Not only will the roll off be nice and even, but the high pass will thermally unload the W18 woofer... A few folks experimented with sealed cabinets (including me), and found that 16 liters is about right. If you want to be anal, build the cabinet slightly large (i.e. 17 liters) then add inert material to the inside of the cabinet for tuning.

So, would an 80Hz crossover point using a 16 liter sealed enclosure be in the neighborhood (knowing this may depend on the SW as well)? Would there be a sonic (in addition to the thermal) disadvantage to letting a hypothetical sealed 1801x roll off naturally and use an electronic low pass on the SW only? Where were you headed with your sealed cabinet explorations? How big is the 1801b's vented cabinet? Wonder if you could send me your cabinet plans?

Quote:
I just checked the T/S parameters of the W18 in WinISD, and it looks like an 11 liter sealed enclosure will give an F3 of ~65 hz with a Qtc of .71. Its also clear this driver is meant for a vented enclosure...


This isn't quite correct. First, adding some dcr will bump the Qes and subsequently the Qts slightly. Second, the Factory parameters are a little off. Most of the drivers I have measured in the past 1-2 years hover around Qts .39-.42.

Not familiar with dcr. Could you elaborate? Is this driver as much at a disadvantage with sealed enclosures as it appears? Would you consider using the 1801b's with a SW a step down for audiophile use, or is this a worthwhile and potentially sonically rewarding, good bang for the buck endeavor?

This just got to be lots more questions, I know. TIA for your patience and handy knowledge.

Bryan

[David Ellis]

So, would an 80Hz crossover point using a 16 liter sealed enclosure be in the neighborhood (knowing this may depend on the SW as well)?

Yep. An 80hz high & low pass would be fine.

Would there be a sonic (in addition to the thermal) disadvantage to letting a hypothetical sealed 1801x roll off naturally and use an electronic low pass on the SW only?

Yes.  Only an electronic high pass for the monitors will electrically stop the signal from getting to the monitor voice coil on the W18.  An electonic high pass will be better.  There are some doppler (IMD) issues too.  These also favor the use of an electronic crossover.

Where were you headed with your sealed cabinet explorations?

I wanted to see if a sealed 1801 would sound subjectively better than a ported 1801. It didn't.  The loss of 10-12hz of bass from the sealed 1801 was undesirable for me, Dennis and Gary Ganser.  I think these are the only 3 guys who heard the a/b comparison. While there are definately advantages to a sealed bass driver, the sealed 1801 just doesn't get low enought to make the bass satisfying IMO.

How big is the 1801b's vented cabinet?

22 liters

Wonder if you could send me your cabinet plans?

Sure, no problem.  Drop me an email and I'll attach the cabinet plans on the return trip.

Not familiar with dcr. Could you elaborate?

DCR is DC Resistance.  Adding a big inductor before the woofer adds resistance to the circuit.  The inductor resistance effectively couples with the resistance already extant in the woofer voice coil.  The increased resistance negatively impacts the electrical damping of the motor.  The result is a higher Qes and corresponding Qts for the motor.  The result is less sensitivity, deeper bass, and a larger requred cabinet.

Is this driver as much at a disadvantage with sealed enclosures as it appears?

There is no clear winner with regard to enclosure choices in some cases.  In this case, I would never choose a stand alone 1801 in a sealed configuration.

Would you consider using the 1801b's with a SW a step down for audiophile use, or is this a worthwhile and potentially sonically rewarding, good bang for the buck endeavor?

I have heard subwoofers sound very nice when the single subwoofer is dead center.  I have also heard subwoofers sound very nice with dual subwoofers in the front corners.  I have never heard a setup using a subwoofer offset in the front/back that sounded right - even with a killer sub driver/amp/cabinet.  The bass stage is always eschewed.  I built a very nice subwoofer.  It was nice with movies, but nothing else.  I didn't use it for music.  Subsequently, I disassembled the unit and don't use it anymore.  The subwoofer didn't make the music sound better.

My origional intent with the 1801 was killer mids + highs and acceptable bass to 40hz.  I am very satisfied with the results and don't feel the need to use a subwoofer - even with movies I don't miss much.  I do like subwoofers, but don't have the physical space in my living room to implement them properly.  Therefore, I choose to have no subwoofer rather than eschewed bass.  I realize my opinion in this matter goes against the common marketing concerning subwoofers.  Such is...

Please let me know if my remarks are incomplete or require clarification.

[bryanb]

Yup, this all sounds pretty clear. If I recall the math, the vented 22 liter enclosure is 18 db/octave, so leaving the 1801b's alone to roll off at 40hz and getting the sub to handle 40hz and below sound would require a similar rolloff at 40hz with the SW... For one additional (potentially) sloppy lower octave.

Sealed 16 liter 1801, electronically enhanced lower rolloff at 80hz, added to a matched upper end subwoofer rolloff, response matching, potential IMD at a more audible frequency, but better power handling in the mid woofer and the two low octaves... Maybe...

Did you try and match your 16 liter 1801's with a good sub? I can understand the dissatisfaction with the bass if not.

Its starting to sound like the 1801's are going to be hard to improve upon... Guess that's why the potential 3 way monitor I see in the other thread seems to be a slow moving idea

Perhaps another lesson in keep it simple. Guess I'm gonna reread the SCC300 thread.

Regards,
Bryan

[David Ellis]

If I recall the math, the vented 22 liter enclosure is 18 db/octave,

Actually the ported 22 liter cabinet will roll off at 50hz 24db/octave.  

The sealed 16 liter cabinet will roll off at 52hz 12db/octave.  

This doesn't really seem like much difference on paper, but it was very audible with music - especially stuff with good electric bass guitar.

Did you try and match your 16 liter 1801's with a good sub? I can understand the dissatisfaction with the bass if not.

I did NOT use the sealed 16 liter 1801s with a subwoofer.  However, I think you are missing the focus of my point.  I'll try to be more concise.

1. Any subwoofer will add MORE bass to any monitor.  This is true with both sealed and ported setups.  

2.  Any single off center will eschew the bass soundstage.  This is wrong/inaccurate.

There are ways to mitate the effects of #1. One of them is using a plate amp with a 24db low pass.  Another way is using a subwoofer driver that matches the characteristics (mostly cone flex) of the monitor.  Yet another is lowering the crossover frequency of the subwoofer.

Since I am really anal about things being CORRECT, I don't use a subwoofer.  I'd rather lose the program material from 20hz to 35hz (i.e. no subwoofer) than have the program material up to about 120hz (i.e. with subwoofer) smeared.  I apprecaite quality more than quantity.  This is certainly true with bass.

If you want MORE bass, build that subwoofer!  

Guess that's why the potential 3 way monitor I see in the other thread seems to be a slow moving idea  

While improved bass certainly happens when introducing a real woofer into a speaker, I think the primary advantage is in the midrange.  Dennis and I were both surprised with this.  Also, ideas happen quite fast!  Matriculating these ideas happens quite slow with 2 charming little boys in the house.  My 3 1/2 year old can almost write his name!

[bryanb]

LOL, MORE and Correct would be my ultimate goal. I'm going to try it with a single SW, positioned ideally (WAF be damned) and see what happens. The vented / sealed convertible is intended to see if HT can work and audiophile can work with the same enclosure. I think I'll get  the mounting dimensions on the SCC300, just in case.

I know what you mean about little ones. A 2 1/2 year old, very cute little girl can get daddy to do all sorts of (previously) unexpected things...

Thanks for the plans.