Open baffle pondering... yet another project.

[cjd]

Yes, I have too many projects in mind, and NO time to do any of them. My work schedule is starting to look like Jon's! So I figured, why not stack my speaker projects up too! Maybe I'll start calling them YAP-X where X is the current number of the (yet another) project... or maybe the speed at which my mouth runs sometimes.

Anyhow, I was meandering through some of the stock over at PE and got to thinking about the B&C 18TBX100 18" and 15TBX100 15" woofers with open baffle use in mind. Am I missing/forgetting anything here? What little information I can find on them suggest they should be quite good on distortion. Price isn't all that bad.

Also gazing at some 8" mids, like the B&C 8PE21 though that's a big magnet assembly - a Neo option really would be ideal there. Pondering BG Neo8 to a tweeter of some sort or another... Pondering a tablesaw-built dual-sided waveguide for that. Tweeter crossing in 5kish maybe. Could be a ribbon.

But hauling out my ultra-cheap open baffles and being yet again mesmerised despite their glaring deficiencies has me really itching for dipole...

C

[Tim]

Actually, B&C makes 2 Neodymium 8" models but they use the same basket

http://www.usspeaker.com/B&C-8NDL51-1.htm

Their 6.5" and 10" models seem more streamlined than the current crop of 8" models.

Wierd I was thinking about something similar but with 2 15's rather than a 15 and 18. This is what I was thinking about for the midrange on the front

http://www.usspeaker.com/B&C-8CX21-1.htm

or this

http://www.bcspeakers.com/index.php?sez=1&categoria=3&id_descrizione=32&prodotto=203

or this

http://www.bmspro.info/photos/bmspro_info/8CN252.pdf

[JonMarsh]

The 18TBX100 looks like many "pro" woofers which use a molded cone edge for the suspension- it does't look like a cloth accordian edge.

With demodulating rings, distortion might be pretty good- and it's got a bit more Xmax than the 18.00 ND W1's I bought, but the SPL curve has me scratching my head a bit (the way it nosedives below 100 Hz - tested in small box?)

Just hard to know without measuring one, but at $320 it's not an impulse purchase (of course the Ciare's weren't either, though it must look like it watching how quick I scarfed them up- hope to have measurements in the proto baffle next Friday, but have to leave on business travel Sunday, so who knows?)

The FR plot on the 8PE21 looks pretty good, it's certainly plenty sensitive enough, and Z curve doesn't look too funky- it will start to beam above 1200 Hz, but it ought to work very well up to 1500, maybe even higher. Certainly you could take it up to 1700 or 1800 to a DDS ENG-1 waveguide and decent driver with the right crossover approach. The way it rolls in the bottom end, you might need to use a 400 Hz crossover with it, though. Note that the 1 mm Xmax makes the Accuton C90/T6 look like a long throw sub in comparison... :W definitely plan on a highish LF crossover if you go open baffle.

[AJINFLA]

You are going to need lots of eq. Look at swept volume primarily (yes driver distortion matters, but a higher distortion driver barely moving may produce less distortion than a lower distortion driver nearing xmax, etc). These x2 would be better than the x1 18" IMHO. The neo 8" B&C's should take you down to 150hz no problemo, these look decent up to 150. Price is right.
http://www.bltsound.com/index.php?crn=143&rn=384&action=show_detail

http://www.bltsound.com/eminence/kappalite-3015lf.pdf

cheers,

AJ

[cjd]

Grr. Browser crashes after you've typed a response suck.

Jon, that's the kind of information that's perfect. I'll look more carefully. I barely remember yesterday morning, don't remember Monday aside from the vague notion I stayed home 'cause my headache was so bad... Not at all set on them, just bored and digging through the PE catalog as I need a longer XLR cable to reach from my pre-amp to the amp on one side of my room. Will probably grab some real short runs since the DAC I may try next has balanced out, so I can go to the pre... and maybe some other cables since I'm short on decent IC's laying around randomly. And maybe some speaker parts while I'm at it... I still like those Ciare drivers but figured I would at least look around, see if there was anything else out there to consider...

Also, I still think I'd like to work with the Neo8 and I think a Fountek NeoCD2 on the top end. Not sure one or 2 Neo8's per side yet. 2 makes mounting harder as it would probably have to be MTM, which means the next driver down has to go next to it. I have some other experiments I'd like to try with those anyhow, but they may end up in a waveguide of sorts. But crossing a Neo8 to an 8" driver should give me lots of wiggle room. I've even considered the RS225 and the Peerless. Would have to double up on these - I'm hoping to reach above 92dB sensitivity, 94 would be nice. Open baffle up to ~5kHz or maybe 8kHz. If I bring that sensitivity requirement down I could use the Neo3 up there and keep it all open baffle.

AJ: who said anything about one? I got a chance to play with a pair of 18" one-off beta pro-sound type drivers (sensitivity was maybe 90dB? But Fs was supposed to be decently low) and that was quite a fun experience. I didn't have the time to really experiment with them. I have pretty serious bass requirements, so I know quite well I'll need to shore up swept volume.

I have some vague ideas rolling around in the back of my head that I'd like to try, and all of them probably stupid and something folks here could say "oh, you don't want to do that, here's why" and leave me deflated... then again, I might save some money. So here's another thought I'd had.

What would happen if I were to mount two woofers facing each-other with some decent distance between them (1 diameter?), wired out of phase. And running open baffle. I imagine it would do crazy stuff to radiation pattern, but how badly? And would there be other problems I'm not thinking of yet?

Oh yeah. I think I may have been looking at the B&C 8PS21 at the same time as the P8E21... 5mm vs 1mm xmax and I don't remember response now, may have even decided on the 8PS21 and... who knows. My brain is about useless right now.

JBL 2241G/H sure is nice.

C

[knifeinthesink]

Chris,

Out of curiousity, what do your ultra cheap open baffles consist of?

[cjd]

One of the famous 4" Panasonic "NSB" buyout drivers PE had for a while a couple years ago, and a 3/8" coil 3/4" Audax tweeter...



I think I started the whole dipole craze (as far as it exists or existed) with the NSB's. These opened some eyes despite their response problems (nice dip at 3k, but hey - it was all parts I had lying around) at the 2004 Chicago DIY.

C

[Brian Bunge]

That might be cool with one of the rear mounted ND20's. IIRC, they need about a 1/2" baffle to flush them up to the front. Use a 3/4" baffle and slightly round over the outside of the tweeter hole to provide a nice smooth transition. Not sure if it would actually provide any horn loading, but could look cool on a baffle that was painted.

[JonMarsh]

Grr. Browser crashes after you've typed a response suck.

Jon, that's the kind of information that's perfect. I'll look more carefully. I barely remember yesterday morning, don't remember Monday aside from the vague notion I stayed home 'cause my headache was so bad... Not at all set on them, just bored and digging through the PE catalog as I need a longer XLR cable to reach from my pre-amp to the amp on one side of my room. Will probably grab some real short runs since the DAC I may try next has balanced out, so I can go to the pre... and maybe some other cables since I'm short on decent IC's laying around randomly. And maybe some speaker parts while I'm at it... I still like those Ciare drivers but figured I would at least look around, see if there was anything else out there to consider...

Also, I still think I'd like to work with the Neo8 and I think a Fountek NeoCD2 on the top end. Not sure one or 2 Neo8's per side yet. 2 makes mounting harder as it would probably have to be MTM, which means the next driver down has to go next to it. I have some other experiments I'd like to try with those anyhow, but they may end up in a waveguide of sorts. But crossing a Neo8 to an 8" driver should give me lots of wiggle room. I've even considered the RS225 and the Peerless. Would have to double up on these - I'm hoping to reach above 92dB sensitivity, 94 would be nice. Open baffle up to ~5kHz or maybe 8kHz. If I bring that sensitivity requirement down I could use the Neo3 up there and keep it all open baffle.

AJ: who said anything about one? I got a chance to play with a pair of 18" one-off beta pro-sound type drivers (sensitivity was maybe 90dB? But Fs was supposed to be decently low) and that was quite a fun experience. I didn't have the time to really experiment with them. I have pretty serious bass requirements, so I know quite well I'll need to shore up swept volume.

I have some vague ideas rolling around in the back of my head that I'd like to try, and all of them probably stupid and something folks here could say "oh, you don't want to do that, here's why" and leave me deflated... then again, I might save some money. So here's another thought I'd had.

What would happen if I were to mount two woofers facing each-other with some decent distance between them (1 diameter?), wired out of phase. And running open baffle. I imagine it would do crazy stuff to radiation pattern, but how badly? And would there be other problems I'm not thinking of yet?

Oh yeah. I think I may have been looking at the B&C 8PS21 at the same time as the P8E21... 5mm vs 1mm xmax and I don't remember response now, may have even decided on the 8PS21 and... who knows. My brain is about useless right now.

JBL 2241G/H sure is nice.

C

Lots of interesting ideas. It's a real shame it takes so much time to implement and test an idea, compared to thinking it up? :W

Migraines? you mention headaches... I used to be prey to those occasionally, but not in years. ThomasW lives with weekly migraines, it seems at times.

[Rudolf]

What would happen if I were to mount two woofers facing each-other with some decent distance between them (1 diameter?), wired out of phase. And running open baffle. I imagine it would do crazy stuff to radiation pattern, but how badly? And would there be other problems I'm not thinking of yet?

Like this?:

http://www.linkwitzlab.com/models.htm#B1

[cjd]

A headache weekly sounds about right for me, but stress will bring those to never-ending. TOday I almost have relief since I got a HUGE burden off my shoulders (also a HUGE win both for my team and for the whole project). But my headache settled in last Thursday probably around 1 or 2pm. Mild, just a little behind the forehead, right side, and jaw tightness. It can settle into my eyes pretty easily, and back of the head at where the neck joins.

I may pull my IB manifold out and do some measurements... hey, why not use whatcha got?! Silly me to not think of that before. I think I'll add a couple Neo8's to my PE order to mess with also. Table saw (plus jig!) should be up to doing the waveguide work I have in mind with these.

Rudolf, I'm pretty sure that Linkwitz is modeling those in phase. If I'm reading his diagrams and stuff correctly. Which I think I am. And that's distinctly different than what I had in mind. But "no different than side by side" is still a good outcome as it opens up some flexibility in basic design, particularly how big (or small) I might be able to make this beast. Yes, if it works right I have some wild and crazy thoughts rolling around. Might end up being a 5-way. Ouch! :lol:

[AJINFLA]

If wire them out of phase you end up with a quadrupole, as discussed here

https://www.htguide.com/forum/showthread.php?t=24687

Radiation pattern can be seen here https://web.archive.org/web/20060902.../rad2/mdq.html

Force cancellation with dreadful efficiency. Perhaps why the Emerald Physics is now a dipole .

cheers,

AJ

[Rudolf]

Rudolf, I'm pretty sure that Linkwitz is modeling those in phase. If I'm reading his diagrams and stuff correctly. Which I think I am. And that's distinctly different than what I had in mind.

"wired out of phase" can be quite different from "driven out of phase". So I just linked an example to find out what you had in mind.
The combination you have in mind then should be a linear quadrupole. Prof. Russell has some more on that on his university site. But I fear that would give you even more headache. :roll:

[cjd]

Yeah, linear quadrupole. Hmm. And more Hmm. Headache? Yeah, but not from this. This stuff is too fun for headache.

C