Waveguide benefits/drawbacks - ongoing studies

[Saurav]

Anyone try this with a ribbon tweeter? It should help with those too, right? How would one go about mounting something like a Fountek tweeter to the MCM waveguide?

[cjd]

You wouldn't use the MCM waveguide I suspect. Though you may be able to if you felt heavily behind it. Could be interesting - not just a waveguide, but it would isolate output to the center part of the ribbon.

Otherwise, you could experiment with recangular horns using somethign like chip-board or other stiff but fairly flexible cardboard (any craft store would have this in the section where they do picture framing).

In fact, rectangular horns should be a whole lot simpler to experiment with!

C

[ThomasW]

Planar tweeters need something like this....

Image not available

[AJINFLA]

Out of the 41 projects 19!!! are using either some sort of waveguide or coaxial speaker. As three projects are subs it means that more than half of the speaker kits use WG or coax. Finnish are really in leading role on this field it seems

I've always liked the Fins :B. Looking forward to your updates Ergo.

Cheers,

AJ

[Saurav]

I started thinking the same thing after I posted the question - something that narrows into a rectangular/slot-like aperture. PE has some rectangular horns, don't they? Time to go look...

And isolating output to the center of the ribbon... where have I read that before? Wasn't that in the VMPS paper?

[AJINFLA]

These I saw these awhile back: http://www.ossaudio.com/.
The BG neo3 might be robust enough to be practical, although it is a planar.
I'll stick with domes.

Cheers,

AJ

Image not available

[cotdt]

i'm really thinking of ripping out my Dayton RS270 to use as a waveguide... and replace the cone with hemp material like the kind they use for Hemp Acoustics... results to follow...

[cjd]

I have an RS270 that was kicked sitting around at home...

hmmmm.

Though I want to run it thorugh acoustic tests first, 'cause I think it survived far better than it should have.

Saurav: you could do flat sided horns easily, but it should be well within your mathematical grasp to do flares too. No purchasing necessary.

C

[Saurav]

You forgot to account for laziness.

[RonS]

Thanks Ergo!

[Paul W]

Waveguide questions ??? (longish)

38,000 miles on airplanes this month gave me a lot of time to think of different possibilities for my next project…and a couple of those possibilities involve waveguides for domes. I do have a few questions though…

Question 1: For me, this is the most important. How do these waveguide thingies sound? Reduced distortion is a good thing, but what about the spatial characteristics? Anechoic room, recording venue, what do they sound like to you?

From reading, Constant Directivity works better with broad included bandwidth…implying a larger midrange driver with restricted directivity. One possible configuration would be a 3-way with 15” metal woofer like the (rumored) RS380HF, W22 mid, and one of the new Seas metal domes. A stuffed U-baffle would be 18-19” wide so plenty of room for large diameter waveguides.

Question 2: Is there any reason a shallow waveguide would not work with a mid like the W22?

An easier way to get to a large mid would be to use a 15” pro driver like the JBL 2226. Since (the few) 15” pro drivers I’ve looked at seem to fall apart below 1k, and 1k might be asking too much of a 1” Hi-Fi tweeter, maybe a 1” pro compression driver like the JBL 2426. So the “all-pro” configuration could be a 2.5 way with two 15”. Problem is, I have zero experience with pro drivers.

Question 3: Is there a repository for independent FR and distortion measurement results for pro drivers?

Question 4: What drivers does Earl GedLee uses in his Summa? Any other driver recommendations?

Question 5: Given appropriate listening area coverage, and careful attention to directivity handoffs from tweeter down through mid and woofer, what else should be considered when selecting waveguide included angle?

Question 6: I don’t have access to a big lathe (and am woodworking challenged to begin with) so how does one go about making large waveguides with a router? Other ideas?

The answer to Question #1 is most important…no point in building something I won’t like. Please fire away if you have an opinion on any of the above!
;x(

[AJINFLA]

Hi Paul,

1) I don't think waveguides "sound" like anything. To me, that would be an indication that something is wrong. Now, I realize that people tend to associate a "sound" with horns, but this is why a waveguide is called a waveguide rather than a horn. The difference between a tweeter with a waveguide and the tweeter without should be very subtle. Its more a question of how does the overall system sound, since you are really shaping the power response. Which leads to the second part of the question. A dipole (which you obviously know) is already directional (figure eight) all the way up to where the driver itself becomes directional (near xo), in which case you still have controlled directivity. What the tweeter WG then does is continue this directivity control up into its operating range until it becomes directional itself.
You seem to be mentioning a lot of larger pro drivers, without specifically stating the goals of you new system. I'm guessing fairly high output is one.
A stuffed U would mean different radiation patter between woofer/mid or non OB mid. Neither sounds like a good choice to me.

2) Why? The dipole radiation pattern of OB is controlled directivity. So is a cardioid. A WG would have to be huge to load the driver acoustically.

3) Don't know of any other than the manufacturers themselves. JBL, Beyma, BMS and Selenium all have FR & distortion specs.

4) B&C. Its on their website: http://www.bcspeakers.com/sez/popup_news.php?id_news=61

5) Diameter, depth, profile.

6) Good question .

cheers,

AJ

[JonMarsh]

You've touched again, AJ, on one of the most important and overlooked issues- having similar directivity throughout the frequency range. One reason I'm not in favor of so called "cardiod" woofer setups (like JohnK prefers), and I'm re-thinking even a moderate U baffle.

[Paul W]

Hi AJ,
I should have stated it more clearly but when I said "spatial characteristics" I was asking about room interaction, not any sound generated by the waveguides. I think at least two things would sound significantly different than a flat baffle:
1) Fewer/weaker reflections from nearby objects/walls.
2) For equal on-axis response, lower power injected into the room at frequencies where the waveguide actually narrows directivity.
Any comment on those two, and/or other, characteristics?

Yes, relatively high output is an objective...but only to support high dynamic range with low distortion in a large room.

Jon,
My current thinking on a stuffed U is to absorb as much of the upper midrange backwave as practical to avoid a "hard switch" from a dipole (near) figure 8 to a monopole waveguide at crossover. The radiation pattern at lower frequencies would transition through cardioid to dipole bass...no abrupt change in radiation pattern at any frequency. (Far easier said than done.)

What are your thoughts?
Paul

[oneoldude]

There must be something in the air. :W

I too was doing some thinking re: H and U frames because I have a bunch of drivers sitting on the floor that need to be put to work. Then I visit here and the same subject is in the air. Interesting. 8O

If we take the position that uniform directivity is a sine qua non of the ideal loudspeaker, then we should not be mixing H and U frame designs. Their radiation patterns are too different. But that does not mean that U-frame designs must be disregarded.

A complete U-frame system could be worked out with separate U-frame enclosures (open ended damped tubes like years ago?) for the W and M and a cleverly designed T housing with an additional rear firing T (inverted signal, eq'ed and delayed) to create a cardioid pattern for the bottom end of the T's passband. That could result in a close approximation of a cardioid pattern from bottom to top (Indeed, the T could be dipoled the same way and do away with the need for a WG in an all flat baffle or H-frame system.).

It would not be an easy project. Salmi (Gradient) uses the cabinet compliance in back of the M along with acoustic resistors in vents (cloth strips) to shape and delay the M's rear wave so as to get his desired cardioid pattern. He uses a co-axial driver that behaves like a WG to control the T and also puts it on axis with the M. But in conversations with him, he told me he has yet been able to accomplish a decent passive cardioid with the W. That is why he uses a dipole there.

So it looks to me that the easiest way to go is either the H-frame or flat dipole. There is some romance in the flat dipole because I really dislike the 1/4 wave resonances generated by the H-frame design. But there is also romance in the H-frame because it allows a smaller baffle to be used. Then again we could bring the dipole down to 40-60 Hz and use a closed box below that. Gee that S.L. is a smart guy! :amen:

Decisions, decisions. Compromises, compromises. Will it never end? :boohoo:

[AJINFLA]

Hi Paul,

there is definitely reduced energy directed at the sides of the room. Mine really doesn't bring that out however, as my left side wall is 5 ft from the speakers and its a floor to ceiling window with horz. blinds and drapes. The right side wall is 15 ft away. It might really stand out in a narrow room.
I never built a non WG version (the thought wouldn't cross my mind ) to do an apples to apples type comparison (which would be tough to do with the low xo). I'll just say that there is, to my ears, a nice balance from top to bottom. Nothing really jumps out at you. It has a sort of constant character from lowish to high volumes. It simply gets louder.
I know that's not the kind of audiophile gushing about this and that, but that's about the best I can do.
I think there is some misconception (look way back at some of my old posts, its been raised before) about the "abrupt" transition from mid to tweeter. This is based on the assumption that there is strong/full rear output from the midbass up to xo and then suddenly none as you transition to the monopole tweeter.
What seems forgotten, is that the rear radiation is being low passed by the basket/magnet assembly well below the xo. I know I swore I wasn't going to horrify my neighbors with test signals or bother with any more measurements (again) on my mutants (I'm done with that design), but I lied. You just made me run downstairs to do a quick'n nasty on the laptop to show the trend. Please don't mind the uncalibrated scale ops: . The mic at woofer level, around 20 deg to the left (so its not directly behind the basket) 2 ft behind the speaker. Its about 4 ft out, facing a heavily treated wall.

Image not available

combined with the front radiation, it's really not abrupt at all. That's the whole idea. Smooth power output into the room with a downward taper up in frequency.

Cheers,

AJ


p.s. On a side note, just started my new job today. The last year or so hasn't been the best for speaker building financially (or neighborly). I hope to have this place of no speaker testing/building rented in a couple months. Then hope to then move to a house. With a garage! Where ungodly amounts speaker building/testing noises can commence. :g> :-y

[JonMarsh]

There must be something in the air. :W

I too was doing some thinking re: H and U frames because I have a bunch of drivers sitting on the floor that need to be put to work. Then I visit here and the same subject is in the air. Interesting. 8O

If we take the position that uniform directivity is a sine qua non of the ideal loudspeaker, then we should not be mixing H and U frame designs. Their radiation patterns are too different. But that does not mean that U-frame designs must be disregarded.

A complete U-frame system could be worked out with separate U-frame enclosures (open ended damped tubes like years ago?) for the W and M and a cleverly designed T housing with an additional rear firing T (inverted signal, eq'ed and delayed) to create a cardioid pattern for the bottom end of the T's passband. That could result in a close approximation of a cardioid pattern from bottom to top (Indeed, the T could be dipoled the same way and do away with the need for a WG in an all flat baffle or H-frame system.).

It would not be an easy project. Salmi (Gradient) uses the cabinet compliance in back of the M along with acoustic resistors in vents (cloth strips) to shape and delay the M's rear wave so as to get his desired cardioid pattern. He uses a co-axial driver that behaves like a WG to control the T and also puts it on axis with the M. But in conversations with him, he told me he has yet been able to accomplish a decent passive cardioid with the W. That is why he uses a dipole there.

So it looks to me that the easiest way to go is either the H-frame or flat dipole. There is some romance in the flat dipole because I really dislike the 1/4 wave resonances generated by the H-frame design. But there is also romance in the H-frame because it allows a smaller baffle to be used. Then again we could bring the dipole down to 40-60 Hz and use a closed box below that. Gee that S.L. is a smart guy! :amen:

Decisions, decisions. Compromises, compromises. Will it never end? :boohoo:

Yeah, compromises- unless you just say, what the h@ll, d@mn the torpedos and full speed ahead! So, I have two new larger baffle designs I'm working on that address this and other concerns, and no U baffle (well, unless in one case you count about 3-4" tapered backwards- it's more of an esthetic thing than an acoustic thing.) The other thing is after much thought and some playing around, I've come to the conclusion (for me) that I don't want a cardiod radiator- I don't think it will give the same sonic advantages as a true flat dipole. So, I'm going somewhat purist... got religion, I guess you'd say.... you know, the Dark side is back....

[Paul W]

AJ,
First, congratulations on the new job! That is always an exciting time, particularly when it enables more speakerbuilding.

I spent many hours on the backside of OB W22's, so I am aware the masking by the spider and magnet assembly. Mine were crossed at 800Hz to mid-domes. An apples/oranges comparison (only about 3 1/2 feet from the front wall) but I didn't have the same success you are having. It wasn't an issue of response, rather I didn't like the way the image wandered depending on which note/frequency was playing. That problem went away by damping the higher frequency rearwave of the W22's. Further from the wall and the rearwave may not have been a problem at all.

With my listening area turned 90 degrees, and further from the walls, my current speakers (the W26/ribbons) are completely different. The ribbons sound best as true dipoles. With damping they sound "lifeless"...accurate yes, but not as enjoyable as dipole.

With so many variables, maybe a few quick & dirty prototypes before I get serious. Some 7" and 12" waveguides from Steelsound ($5 and $7!) are in transit and, out of the clear blue, a friend at work offered to sell or loan a couple of JBL 15" pro drivers...dunno what they are yet.

Dude!
I have always wanted to say that, but a little old myself. You gave me an idea. I might also try back-to-back drivers in-phase...rearwaves vented to the sides/top/bottom. 4-leaf pattern with nulls to both walls? Someone has already done it, but it might be interesting to try while I'm making a mess in the garage.

Jon,
You're absolutely right. MDF is cheap...d@mn the torpedos!
Paul

[alexnick]

http://www.exdreamnet.de/download/WgPractice.zip

http://www.exdreamnet.de/download/WgRevisited.zip

http://baseportal.de/cgi-bin/baseportal.pl?htx=/Data/exdreamaudio/download&cmd=list&range=0,20&cmd=all&Id=3

And other interesting stuff too, here:

http://baseportal.de/cgi-bin/baseportal.pl?htx=/Data/exdreamaudio/download

[Angaria]

Is diffraction on the baffle edge less of a concern after using a wave guide?

I've been working on a design where a neo3 tweeter is basically suspended in space on the face of a half-sphere.

If I put a wave guide on it does that obviate the hemisphere baffle?

rough sketch attached

[Branwell]

Hi Paul,

Re: Wave guide sound….

I’ve been playing with BMS 4540ND compression tweeters in DDS I-90 waveguides crossed to 10” PHL mids crossed to 15” bass drivers. The crossover I use is the DEQX.

For reference, with the same crossover, I’ve had systems with Seas W22, W18ex SS18W/8545, PHL1340, 1120, Seas Millennium, SS9900, Morel 110, G2, 45” Newform and a bunch of other stuff in sealed, ported, and dipole configs.

Realism: To me, regardless of music played, the pro sound setup mentioned sounds more real.

Enjoyment factor: Prosound setup hands down.

Sound stage: Not sure the pro sound drivers have an advantage, but they are not at a disadvantage.

Sense of ease: The prosound drivers mentioned make standard drivers mentioned sound like toys. The prosound drivers are in a different league when it comes to headroom, dynamics and lack of congestion on complex recordings.

Range of recordings: I’ve noticed a funny trend among audiophiles. Seems the better the speaker, the fewer recordings it can play without sounding nasty. Apparently the truly great speakers have such good resolution that any recording flaw shows up. This was pretty much my experience with standard drivers. Interesting thing with the pro sound drivers mentioned, the flaws show up, but not in a nasty way. i.e. the sound never gets hard and brittle. I can still enjoy 95% of my music collection.

Well that sounds all up. What’s the down.

Very efficient drivers require very quiet electronics. Any hums or buzzes will easily be heard.

The dispersion pattern is narrower. Might be more even to a point, but the wave guide tweeter definitely rolls off on the top end more than a 1” dome off axes.

The FR of the raw drivers is not as smooth as the standard drivers mentioned. A genius with passives, of which I am not, might be able to deal with it, but I needed to resort to digital active to solve that issue.

Box size. Big drivers need big boxes. Not a problem if you have the room, but….

Overall, while I still listen to my setups that use standard drivers, I find myself less and less satisfied with them. They just don’t sound as real.

Branwell

[jquin]

As far fabrication of the waveguide is concerned I guess one could make successive cuts using a jasper jig at different depths. A rounded end router bit would smooth out the steps a bit into waves. I'm not sure what kind of steppiness would be tolerable without effecting sound quality.
Aesthetics of the job would be a somewhat subjective matter.

John Q

[Paul W]

Hi Branwell,
Pretty old question, so surprised to see you answer h:

I'm just beginning to get serious on a path very similar to yours. BMS4552ND, same DDS waveguide, 18Sound 10NDA520 mid, BMS 18N850 woofer in a damped U-baffle.

I second most of what you say, especially the realism and sense of ease. The ability to play an instrument very loud and -simultaneously- reproduce a voice 20-30db down with great delicacy is really striking...and something rarely heard with Hi-Fi drivers. However, my 80-90's CDs still sound bad, and most of my SACDs and DVD-A still sound great. Listened to a couple of AIX DVD-A disks last night...wow!

The speakers are located several feet from the nearest wall, so not much benefit from the narrowed dispersion/reduced wall reflections. However, the room is extremely large so the increased dynamic range really helps. Hi-Fi tweeters without waveguides get "swallowed up" by the room.

Agree on the crossover. Even with a swamping resistor in parallel with 16 ohm 4552s, impedance is still quite choppy. I'm certain passive can be done (using one now) but I would be tweaking for a year. Since my projects get replaced about once a year, the mini-project for today is a switch to full active.

A couple of questions for you: What XO slope and frequency are you using on the DDS? A very rough check showed it losing pattern control higher than advertised. Also, have you tried any of Earl Geedes "fish filter foam" in the WG?
Paul

[h-bar]

Not sure if this is of interest or use to anyone reading this thread, but here are some measurements I obtained from an MTM with waveguide-loaded tweeter. The top graph shows, both woofers, tweeter, and their sum, all at 1 meter on-axis. The bottom graph was obtained at tweeter height, and 0, 15, 30, and 45 degrees off axis. There are 5 dB separating each horizontal grid line. Ignore the low end rolloff because the plots do not include any nearfield woofer measurements. The overall downward tilt of the response was done on purpose.



The speaker, and a close-up of the modified MCM waveguide, are at the following links. The crossover is passive.






The drivers have been around quite awhile. It's a ScanSpeak d2900-9300 textile tweeter, and two Vifa 5.5" P13WH-00-08 woofers. The excessive woofer separation is a result of the fact that I modified a cabinet I had originally built for another purpose rather than starting from scratch.

I posted this on DIYAudio but triggered no interest. Since this seems to be a kinder and gentler forum, I thought I'd risk giving it one more shot.

[JonMarsh]

Hi Paul,


p.s. On a side note, just started my new job today. The last year or so hasn't been the best for speaker building financially (or neighborly). I hope to have this place of no speaker testing/building rented in a couple months. Then hope to then move to a house. With a garage! Where ungodly amounts speaker building/testing noises can commence. :g> :-y

Congratualations on the new job, and hope your real estate changes are completed smoothly!

[Branwell]

Hi Paul,

I haven’t settled on the top crossover yet so have two programmed in the DEQX. One at 1400hz and one at 1600hz. Both are 96db. The bottom is 180hz at 48db.

On the foam front. No. I haven’t tried it….Might though….

I am thinking my next project might be to try one the BMS coax compression drivers in a large wave guide.

On the 18” BMS woffer. How is that working out? How high does it play well?

Branwell

[Paul W]

Branwell,
The local aquarium store has a wide array of different filters, several precut in circles about the right size for WGs. So I bought a bag of different types...let you know how they work out.

The BMS 18 is a very substantial driver with excellent build quality. As shown in the BMS spec sheets, the impedance curve is quite flat. Breakup is at 1.1k and strong enough that it needs a Seas-like trap. There is another resonance at 9k which may be dust cap breakup but, with xo, so far down it doesn't need a trap. So, I think the driver should be okay to 300Hz but haven't tried it over 200Hz. The only "problem" with it is the cone is relatively heavy so it takes at least 100 pounds of mass to prevent baffle shake...it really makes you think about how powerful the motor is!
Paul

[AJINFLA]

Is diffraction on the baffle edge less of a concern after using a wave guide?

I've been working on a design where a neo3 tweeter is basically suspended in space on the face of a half-sphere.

If I put a wave guide on it does that obviate the hemisphere baffle?

rough sketch attached

Depends on who you ask. Earl Geddes certainly thinks it should be a concern.
It won't hurt to have a bit of round over of the baffle edges on your monopole, so why not.

I posted this on DIYAudio but triggered no interest. Since this seems to be a kinder and gentler forum, I thought I'd risk giving it one more shot.

Don't be so sure of that . Hey, good job. MTM's aren't my bag, but heck, you had the enclosure with cutouts already, why not give it a shot.

Congratualations on the new job, and hope your real estate changes are completed smoothly!

Thanks Jon. Not as new as it was 9 months ago . My real estate woes continue until I can find a decent tenant for my loft :banghead:
No more students LOL. The new listening space is quite a bit deeper, but only 1/2 as high. Most importantly, much further away from the neighbors, although I'm afraid the SPL capability of the new system might negate that :lol: .

Branwell,
The local aquarium store has a wide array of different filters, several precut in circles about the right size for WGs. So I bought a bag of different types...let you know how they work out.

The BMS 18 is a very substantial driver with excellent build quality. As shown in the BMS spec sheets, the impedance curve is quite flat. Breakup is at 1.1k and strong enough that it needs a Seas-like trap. There is another resonance at 9k which may be dust cap breakup but, with xo, so far down it doesn't need a trap. So, I think the driver should be okay to 300Hz but haven't tried it over 200Hz. The only "problem" with it is the cone is relatively heavy so it takes at least 100 pounds of mass to prevent baffle shake...it really makes you think about how powerful the motor is!
Paul

Paul, I had asked a while back on a couple forums about what type of foam Geddes uses for his RSP. Are you sure the pet store stuff is similar enough?
I also recalled looking at the BMS 850 when they released it. Very nice choice on your part IMHO. However, the dip @ 300hz would suggest to me pure sub, usable to 150 or maybe 200hz in a pinch (with some upper end eq for XO purposes).http://www.bmspro.info/photos/bmspro_info/18n850.pdf

cheers,

AJ

[dwk]

Paul, I had asked a while back on a couple forums about what type of foam Geddes uses for his RSP. Are you sure the pet store stuff is similar enough?

Geddes uses 30ppi polyurethane foam, genearlly used for filtering. The pet store stuff is actually quite similar, but quite expensive for the small quantities you get. McMaster has larger quantities (SKU 2195K55 for example), but it's in thin sheets so a fair chunk of work is needed to build up deeper plugs. I am intending to build Geddes style plugs for my U15's, but it may be a while.


FWIW, I'm still in the early stages of mapping out my experiences with the U15's. Since they aren't DIY I don't post much on them, but my experience so far pretty much mirrors what Branwell relates. Since the horn/waveguide carries everything from 300 on up, directivity is controlled as much as the physical size of the horn allows, and this really does seem to mitigate room reflections - I may easily be imaging things, but I sure seem to hear incredible clarity from my setup. The sense of ease is also eye-opening. I'm running ~1W through cabinets designed to take 800W, and there's just no way you'll see any kind of compression or strain. My only 'complaint' is that matching subs has been challenging - having a 15+dB difference in efficiency is a problem.

[EdL]

From AJ: "I had asked a while back on a couple forums about what type of foam Geddes uses for his RSP. Are you sure the pet store stuff is similar enough?"

My recollection of Earl's comments over @ AAsylum are that he used 30 ppi (pores per inch) open cell foam. Further checking this for sources of the material turn up one in Livonia, MI. Roush Industries includes some acoustic concerns. Their website includes products that Earl may have picked from...it may be a stretch, they're in the same town.

http://www.roushind.com/html/nvh_nvcpacoustic.htm

After just checking the site, I no longer find the 30 ppi material listed. It had been

I've played with this material to see if a plug can be turned on a lathe. It can.

[Dennis H]

How thick is Geddes's foam plug? Put another way, what percent of the horn depth does it cover?

[Dennis H]

Okay, I've been Googling around and I found this page discussing fish filters and listing some sources for bulk foam. He says the foam is reticulated stuff like they used for speaker grills in the '70s so not all 30 ppi open-cell stuff would be the same. Reticulated foam has the cell walls dissolved away leaving a stringy sort of structure. Foambymail has 30 ppi up to 2" thick at a pretty good price. His page number for McMaster is old. Didn't try any of the others.

http://webpages.charter.net/bobalston/BuklFilterMedia.htm

http://www.foambymail.com/Hi-FlowFoam.html Scroll down to speaker foam.

[dwk]

How thick is Geddes's foam plug? Put another way, what percent of the horn depth does it cover?

It fills the entire horn, and actually sticks out front a bit as he rounded it into a spherical section. Thus it's probably 14-16" deep. Since the foam is so open, it has to be pretty deep to offer any absorption. I'm really not sure how well the idea would work with the small tweeter-only waveguides that are more commonly discussed around here.

I 'm not sure the foambymail stuff is the same, but it seems to be in the same direction. Not all that much cheaper than McMaster per unit volume, but the smaller pieces and thicker sheet means less waste. Might be worth the risk to try a 2" 36x48 sheet..

[AJINFLA]

Hmm,

good catch Dennis (sorry, couldn't resist with all this fish talk :lol: ). $70+ for the 2" is a bit steep for the measly pieces that I need. Maybe I will try the pet store stuff.
Now how to turn it down to the needed profile...

Image not available

cheers,

AJ

[Dennis H]

Now how to turn it down to the needed profile...

If you're building it in layers, say 2" thick, just set your jigsaw at an angle and cut out circles.

[Paul W]

The round filters I bought are actually three different types. One is an open cell foam, another is a polyester filament type, the third is also polyester but "variable density" (more open on one side that the other). Ten filters for about $25. A quick check yesterday didn't produce any noticeable difference, but this was only one filter thickness (less than an inch).

Another possibility for cutting foam might be a "hot wire"...might also fuse the layers together.

AJ,
That 300Hz dip in the factory graph almost caused me not to buy the 850...haven't seen anything that bad in the examples I have. They seem happy at 200 but I haven't had any reason to try them higher.

What model are the coaxials? What is the outside diameter without the mounting tabs? It looks like a good candidate for a CC I'm building for a friend.
Paul

[AJINFLA]

What model are the coaxials? What is the outside diameter without the mounting tabs? It looks like a good candidate for a CC I'm building for a friend.

JBL 350244-001 & 350245-001. 5.5" dia. You betcha.
http://www.jblproservice.com/pdf/Con...rol%2030WH.pdf Bracket & screws mandatory. Glassfiber rings advised.
FR http://www.jblpro.com/pages/install/..._30/Ctrl30.pdf
Note the peak 123db/1m capacity. Flank it with 2 capable woofers and you have a serious LCR for seamless front integration.
My kind of MTM monkey box .

cheers,

AJ

[ergo]

I had some posting in Jon's Isiris thread about my results with waveguides and Seas T29CF001
here
and here

Now I made some follow up tests.

I first planned to try the Vifa XT25 in WG but that is not very easy to do. The construction of XT25 is such that the front plate extends backwards to meet the surround of the ring radiator and if the front plate is removed it is very hard to do the same effect with WG. To leave the front plate in place would mean modifying the WG physically which I do not want to do just yet.

So I tried two thing instead.

First I inserted felt rings between the T29CF001 and WG to make the dome sit deeper in the WG throat.

Image not available

I hoped it will help the situation with the 8kHz and 16kHz dip. The result was basicly that the WG lost it's "magic" meaning the lower end gain was not there anymore. The response looked like a regular tweeter with extra dips in it

The second attempt was with a Seas 27TBFC/GTV in waveguide.

Image not available

This worked much better.

Here is a comparison of T29CF001 and 27TBFC on axis and 15 degrees off axis (levels intentionally offset)

Image not available

On the on axis response the dips are still there but a bit less severe.

The off axis is even better with 27TBFC/GTV.

The off axis for T29CF001 in WG

Image not available

And the off axis response of 27TBFC/GTV in WG

Image not available

For the last a graph of the 27TBFC/GTV in WG plus a first order electrical filter

Image not available

This gives quite perfectly the 4th order LR HP response for 1kHz crossover.

If this tweeter could handle it - I do not know yet.

Ergo

[ergo]

Few more interesting graphs.

These are polar responses for Seas W18NX and 27TBFC/GTV in WG compiled from off axis measurements. Measurements were done with off axis degrees 0,5,10,15,20,25,30,35,40,45,50,60,70,80,90

@ 500Hz

Image not available

@ 1kHz

Image not available

@2kHz

Image not available

I think this shows quite well that the WG indeed does make the polar patterns match better for the mid unit and the tweeter giving a smoother power response in the end.

Ergo

[ergo]

Aaah - one request. Would it be possible for the moderators to combine two thread on the subject of waveguides, this one and the "New Wave Guide Study". They both have good info in them but I quess it would make a better reference is the info would be combined or at least the threads cross link to eachother in the beginning ?

Ergo

[AJINFLA]

Ergo,

I added a link to my original post in this thread.
Some pics from CES2007. There are WG's on each page. The OSS models look to have sub-optimal terminus baffles. That Almarro mid looks suspiciously like the TB titanium. Lastly, looks like Clayton Shaw @ Emerald Physics dumped the quadrupole in favor of dipoles (retained the WG of course )

http://www.positive-feedback.com/Issue29/ces071.htm

cheers,

AJ

[ThomasW]

Aaah - one request. Would it be possible for the moderators to combine two thread on the subject of waveguides, this one and the "New Wave Guide Study". They both have good info in them but I quess it would make a better reference is the info would be combined or at least the threads cross link to eachother in the beginning ?

Ergo

Merging the threads would create a mess. The forum's software merges thread posts according to the date each was posted. Since the two threads have posts occuring on the same dates, the software would 'shuffle' the two thread into one, destroying the continuity of the individual threads.

Crosslinks have been posted in the first post of each thread,

[JonMarsh]

Ergo,

I added a link to my original post in this thread.
Some pics from CES2007. There are WG's on each page. The OSS models look to have sub-optimal terminus baffles. That Alamarro mid looks suspiciously like the TB titanium. Lastly, looks like Clayton Shaw @ Emerald Physics dumped the quadrupole in favor of dipoles (retained the WG of course )

http://www.positive-feedback.com/Issue29/ces071.htm

cheers,

AJ

The Emeralds Physics LS-1 is an interesting way to package the dipole subs and main drivers together in two sets of panels with a floor foot print more like a conventional tower...

I agree about the Almarro mid-

The Almarro A318B integrated amplifier sure uses some knarly looking output tubes- look like old triode transmitter tubes!!

Wide baffles in their big speakers will make some aspects of design easier, but I'm not sure I'd like what they'll do to the net room power reponse. Would be interesting to do a comparison of enclosure profiles and how that affects things... of course, I have my own opinions already.

[cjd]

The Emeralds Physics LS-1 is an interesting way to package the dipole subs and main drivers together in two sets of panels with a floor foot print more like a conventional tower...

Interesting? It's practically brilliant. Why the heck didn't I think of something like that?

C

[JoshK]

Those big three tit tubes are 6C33C triodes. I am currently designing some PP monoblocks based on them. Tube audio is my other hobby.