New Wave Guide Study

[JoshK]

Thanks but I already have 8 on hand. I bought extras so if I broke any or I could set up multiple domes to experiment with, etc.

[Dennis H]

Btw, anyone have any suggestions for which compression driver to use? I am clueless about these. The B&C ones look to have much flatter FR, but I have no idea if the horns they are measured on are compairable to the ones the BMS are measured on.

I'm not sure but, just looking at the curves, the B&C looks like it's measured without a horn. The BMS curves specify a 90x75 CD horn which would have a non-flat on axis response. Same with the sensitivity specs, the B&C looks like it's without a horn and and BMS is with a typical horn. So, if all that's true, the curves don't help much to make a decision. I wish we could see some distortion curves for the B&C although I suppose even those are affected by the horn.

Pinging Mark Seaton, which 1" compression drivers do you like?

[noah katz]

In case he doesn't chime in, I believe Mark favors the BMS 4552ND.

[JoshK]

I've been leaning towards the BMS for no particular reason other than positive chat and it isn't much more, about the same ballpark.

[JoshK]

Well I received my DDS Eng 1-90's. I got the bolt on type. It look like it may be able to be used with dome tweeters...but not sure. I only have the H1212 on hand and its metal grid is in the way. Its a bit shallower than I expected. I think my SteelSound 7" WG's (not 90º...probably ~70º...same as Dayton WG's I think) are deeper or as deep.

The DDS is a bit expensive IMO for a WG, but then it is nicer made then the SS or MCM wg. Its not a cheap plastic...its a thicker plastic composite mold of some type. Seems like it'll be less prone to resonance.

[EdL]

Hi Josh,
I posted a method for removal of the H1212 hexagrid on the "Seas H1212" thread. They can be removed, saved and reinstalled.

[Branwell]

Hi JoshK,

You might try the BMS.
I’ve got the DDS 90 wave guide hooked up to a BMS 4540ND driver and really like it.
Would also love to try the 4542ND.

The 4540 in the DDS wave guide measured about identical to this graph.



Something to keep in mind if you’re planning a digital crossover with a compression tweeter.

Initially I had the combo crossed directly with a DEQX. Sounded good, but not quite right.

The problem gain mismatch. I had it crossed over to a PHL 1340 bass mid driver and the DEQX was having to pull about 17 db or more from the tweeter. I think this was pushing things as far as the digital DEQX was concerned.

I put an L Pad in the circuit taking about 10db or so from the tweeter. After this, things shaped up nicely.

On crossover points.
As you can see from the above graph, the driver starts taking a dive right around 1500hz.
I found crossing it over at 1500hz did not present a problem for the driver. It never sounded like it was stressing or loosing dynamics at any volume level I listen at even at that low crossover point. This is in stark contrast to 1” domes which to me really go to poop when one gets anywhere near their natural roll off.

Branwell

[Dennis H]

I found crossing it over at 1500hz did not present a problem for the driver.

That's good news. It implies BMS is easily meeting their specs -- freq range 1.2K-30K, recommended crossover 1.9K. There's hope that the 4552ND might actually be able to use a 1K crossover based on the specs -- 500-20K, rec XO 1K. The lower crossover would be useful given how much the waveguide increases C-C distance.

[JoshK]

Thanks Branwell for the tip. Yeah that is a good idea to bring the gain mismatch down with passive elements. I picked up a pair of JBL 2123H's so not altogether different than your combo. Below the JBL's I had planned to use some Lambda TD15x's but the dude who sold them to me innappropriately packed them and they were damaged.

I'd really like to repair the Lambda's but John J of AE hasn't responded, nor has the dude from Millersound. I don't know who else to ask about repairing the cones.

[Branwell]

Hi JoshK,

I recently dismantled the BMS / WaveGuide, 10” Phl Mid section to rebuild them into better cabinets.

In the mean time, I rehooked up MTM top sections with Seas W18ex drivers and Millennium tweeters.

The first thing I noticed was…where did all the power go?. The second was where did all the dynamics go?. The third was where did all the detail go? And lastly, where did the life go? My foots not tapping.

Changed out the top units for MT tops with SS8545s and North D28 tweeters. Same thing.

Changed them out for MTM tops with PHL 1340 Bass mids and Morel 110 tweeters. Better, but much the same.

Here’s the thing that gets me. In theory, all of the above systems should have outperformed the BMS / WaveGuide, 10” Phl Mid section in detail, but in practice, they don’t.

Wondering why, I came to a conclusion...probably wrong, but I like it.

The BMS / WaveGuide, 10” Phl Mid section is so totally effortless and easy going in my room that it gets played louder, and being louder, one hears further into the subtleties of the music…Will have to take some SPL measurements, but I am fairly sure that’s it.

Would be interested to hear how your setup ends up sounding.

Branwell

[Mark Seaton]

In case he doesn't chime in, I believe Mark favors the BMS 4552ND.

Actually, of their 1" exit drivers, the 4550 is my preference if weight isn't a factor with portability. Having recently killed a few dome tweeters with large home theater dynamics and a big amp, I keep coming back to the peace of mind in the headroom and power handling of real compression drivers. The ring radiators are the other options that interest me, but I'd rather put the effort into making a good compression driver work. While there are other good compression drivers on the market, for the cost and performance, the BMS drivers really perform. The ring design gets around the breakup of a large metal diaphram, and they tend to be more efficient on the bottom end of their operating range than comparably priced or sized drivers. I haven't looked to confirm in a long time, but I also believe the coil has a bit more mobility than more conventional drivers.

The one I'm very interested in but haven't seen much info or reports on yet is the 1.4" exit, coaxial/2-way compression driver. This driver on the 1.4" 18Sound horn might be a very worthwhile pairing.

[Mark Seaton]

Hi JoshK,

I recently dismantled the BMS / WaveGuide, 10” Phl Mid section to rebuild them into better cabinets.

In the mean time, I rehooked up MTM top sections with Seas W18ex drivers and Millennium tweeters.

The first thing I noticed was…where did all the power go?. The second was where did all the dynamics go?. The third was where did all the detail go? And lastly, where did the life go? My foots not tapping.

Changed out the top units for MT tops with SS8545s and North D28 tweeters. Same thing.

Changed them out for MTM tops with PHL 1340 Bass mids and Morel 110 tweeters. Better, but much the same.

Here’s the thing that gets me. In theory, all of the above systems should have outperformed the BMS / WaveGuide, 10” Phl Mid section in detail, but in practice, they don’t.

Hi Branwell,

I do believe that you are correct that the fact that the BMS waveguide and 10" PHL are operating well within their linear range is a significant factor, but I doubt this is the only notable difference. If you are using the DEQX then a good deal of the acoustic phase differences are minimized, but that still leaves the directivity of the waveguide and the larger 10" driver. Even if the on axis is matched to rediculous similarity, the off axis, total power radiated into the room, and the interaction with the room's acoustics will be quite different. There's also a question of how the DEQX is taking its measurements and how it determines the correction applied, as the horn has a different acoustic behavior than the dome tweeters and the room will creep into both measurements, and of course contribute less with the waveguide.

[Dennis H]

Actually, of their 1" exit drivers, the 4550 is my preference if weight isn't a factor with portability.

Hi Mark,

Why do you prefer the non-neo version? BMS claims the 4550 can cross a bit lower but I notice it shows an upward spike in the 3rd harmonic below 1kHz that the 4552 doesn't show. If I couldn't see any numbers, and just looked at the curves, I'd be inclined to cross the 4552 lower.

[Mark Seaton]

Good catch Dennis,

The neo motor does have greater motor strength which is probably part of the difference. I have not compared the two side-by-side as the projects I've used the 4550 in were ones where the cost was already pushing it a bit and the weight wasn't an issue. It probably comes down to cost, weigth and value of a slight performance gain. If the added cost of the 4552ND was not a concern in a project, I might choose it over the 4550, but in the end you'd need to take some more measurements of the two to make any real determination. I would point out that the waveguide and the crossover design will probably be hugely more impactful on the resulting sound quality than the difference between the two drivers.

[AJINFLA]

Even though I'm not currently pursuing the static WG avenue , I found this very interesting http://audioheritage.org/vbulletin/s...ad.php?t=12126
He is doing a great deal correctly IMHO. Food for the mind.

Cheers,

AJ

[TacoD]

Great link!

[JoshK]

Great link!

indeed!

;x(

[Patrick Bateman]

Hi JoshK,

I recently dismantled the BMS / WaveGuide, 10” Phl Mid section to rebuild them into better cabinets.

In the mean time, I rehooked up MTM top sections with Seas W18ex drivers and Millennium tweeters.

The first thing I noticed was…where did all the power go?. The second was where did all the dynamics go?. The third was where did all the detail go? And lastly, where did the life go? My foots not tapping.

Changed out the top units for MT tops with SS8545s and North D28 tweeters. Same thing.

Changed them out for MTM tops with PHL 1340 Bass mids and Morel 110 tweeters. Better, but much the same.

Here’s the thing that gets me. In theory, all of the above systems should have outperformed the BMS / WaveGuide, 10” Phl Mid section in detail, but in practice, they don’t.

I agree with you. Once you get used to the lack of dynamic compression, it's hard to go back isn't it?

Wondering why, I came to a conclusion...probably wrong, but I like it.

The BMS / WaveGuide, 10” Phl Mid section is so totally effortless and easy going in my room that it gets played louder, and being louder, one hears further into the subtleties of the music…Will have to take some SPL measurements, but I am fairly sure that’s it.

Can you tell me a little bit about how the "room sound" is different? Personally, I've found that the use of constant directivity waveguides sounds much closer to the real event. Ironically, the "room sound" is so different, it actually sounds strange at first. But once I grew accustomed to it, traditional speakers sound "tinny" and weird. When I listen to a conventional dome, the treble sounds completely unnatural to me now.

Would you agree that waveguides sound more like "the real thing?"

Would be interested to hear how your setup ends up sounding.

Branwell

[Patrick Bateman]

Hi JoshK,

You might try the BMS.
I’ve got the DDS 90 wave guide hooked up to a BMS 4540ND driver and really like it.
Would also love to try the 4542ND.

The 4540 in the DDS wave guide measured about identical to this graph.

I've posted extensive measurements of my speakers. They use the same compression driver. I agree, they measure well. I've also posted a crossover. I'm using a 99x66 degree oblate spheroidal waveguide.

Something to keep in mind if you’re planning a digital crossover with a compression tweeter.

Initially I had the combo crossed directly with a DEQX. Sounded good, but not quite right.

The problem gain missmatch. I had it crossed over to a PHL 1340 bass mid driver and the DEQX was having to pull about 17 db or more from the tweeter. I think this was pushing things as far as the digital DEQX was concerned.

I put an L Pad in the circuit taking about 10db or so from the tweeter. After this, things shaped up nicely.

On crossover points.
As you can see from the above graph, the driver starts taking a dive right around 1500hz.
I found crossing it over at 1500hz did not present a problem for the driver. It never sounded like it was stressing or loosing dynamics at any volume level I listen at even at that low crossover point. This is in stark contrast to 1” domes which to me really go to poop when one gets anywhere near their natural roll off.

Branwell

Traditional passive crossovers cannot give you a flat response with a compression driver. This is because the compression driver response is not flat! What's worked for me is to use a 2nd or 3rd order crossover, but adjust the "corners" dramatically. So the first corner could be as high as 6khz, but the 2nd corner could be as low as 1khz.

In my current crossover, I'm using two caps and an inductor, which gives me three corners. Like a 3rd order crossover, but not a textbook one.

:: PB ::

[Paul Ebert]

Apologies if this is a thread hijack, but I'm really curious which DIY available coaxials (or coincidents) AJ would recommend.

Also, where can I get information on some of these waveguides (like the DDS)? Are there links to pictures, prices and technical information?

Thanks.

[AJINFLA]

Paul,

I recommend.....you tell me lots more about your systems specific needs
Frequency range, target SPL, box/boxless, shielded/non, musical tastes (eg. ruthless accuracy [rigid cone] vs creamy smoothness [soft cone], etc, etc, etc... and of course, the dreaded b word. Budget.
Keep in mind also that it may be tough to recommend something that I haven't heard, unless its the TAD CST (then the b word would be BIG$), so there are some units that would still be plenty good, my recommendation or not.

cheers,

AJ

[Paul Ebert]

Paul,

I recommend.....you tell me lots more about your systems specific needs

Sure! I would be interested in a coax (or coincident) that goes fairly deep (100 hz would be great) in a dipole. It would need to have enough xmax and power handling to do OK with that in a baffle that wasn't too wide (say < 18"). My target efficiency is >90 dB/watt. I want good dynamics, excellent detail (hard cone?), low distortion. I'd like it to be a small coax so beaming is reduced (8" would be good). I currently own a pair of Hawthorne Silver Iris's which are OK (and inexpensive), but they beam a lot.

Shielding is a non-issue. I'd actually prefer non-shielded since it would probably have better air flow in the back. This is for a music system (not, HT). My musical tastes are broad, but mainly classical music.

Budget is fairly flexible, though I don't think I could pay more than, say $500 or $600 for a coax (woofer and tweeter) pair. Of course, quite a bit cheaper would be better!

Thanks.

[AJINFLA]

I have not heard a Silver Iris, but I see a lot of red lights in that approach.
Cheap, yes. Weak motor allows OB without eq etc. Effective but very non optimal. That is simply not the way to equalize reponse..and dipoles need eq.
XO is also way too high for such a large woofer. I would expect less than stellar mids from upper band nastiness.
If you are willing to eq, then a smaller but much higher quality driver is the way to go. 100hz OB requires a good amount of swept volume for even modest SPL. Forget an 8". Too much excursion required, a no no for a coincident driver.
A larger woofer cone and a robust tweeter that can cross low to avoid large cone upper band limitations is the recommendation.
My suggestion would be something like this http://www.assistanceaudio.com/15_Assaudcoaxial.html
Crossed 1-1.3k range.
I've heard Ciare and BMS, but not this unit, so no *recommendation* .
Good luck.

cheers,

AJ

[Paul Ebert]

I have not heard a Silver Iris, but I see a lot of red lights in that approach.
Cheap, yes. Weak motor allows OB without eq etc. Effective but very non optimal. That is simply not the way to equalize reponse..and dipoles need eq.
XO is also way too high for such a large woofer. I would expect less than stellar mids from upper band nastiness.

Yep, that just about sums them up, though the mids are better than I would have thought. I bought them last year because I wanted something efficient (they have great dynamics) and with some good bass. From that perspective, I've been fairly pleased. Eventually though, I'd like something better. And, yes, the replacement will include eq - I already have enough of Bob Ellis's Active Filter 4 boards to build a 4-way active crossover.

The Ciare / BMS coax does look nice.

Thanks.

[Paul Ebert]

I have a question for you controlled directivity gurus. I can appreciate that matching the directivity of the tweeter to the midrange could be a very good thing, but is this an intrinsically better approach than going the other way? As in, a dome mid to match a dome tweeter. Or, does that simply push the problem down to between the woofer and the mid?

[Patrick Bateman]

I have a question for you controlled directivity gurus. I can appreciate that matching the directivity of the tweeter to the midrange could be a very good thing, but is this an intrinsically better approach than going the other way? As in, a dome mid to match a dome tweeter. Or, does that simply push the problem down to between the woofer and the mid?

A dome mid and a dome tweeter do not have the same directivity. So it's not a solution to the directivity problem. A waveguide is.

:: PB ::

[Paul Ebert]

Oh. Maybe, then, my question was a stupid one . In that case, I may as well make evident my ignorance: how does the directivity of a dome mid and dome tweeter differ?

Thanks.

[EdL]

Directivity of frequencies is more appropriate than directivity of drivers. A tweeter carries a greater share of those higher frequencies that tend to be directive, or beam. A waveguide will have a greater influence in dispersing the frequencies carried by a tweeter. A waveguide can have some influence with a mid-dome, just not as much.

I've had to walk the same path as you. There is no ignorance in asking a good question.

[sliceofhogan]

Phio Audio waveguide

The Phio Audio is also interesting. The developer uses a XT200 as driver and crosses at 800hz. Too expensive (EURO 299) for a test, alas...
Link to Phio Audio

[augerpro]

Paul E you read my mind! I'm still not totally understanding the goal of controlling this directivity, Edl's answer notwithstanding ops:

Even power response throughout the FR being important to SQ (according to Dr. Toole's research anyway), I assume this is the main goal of the waveguide. But I always thought it was even power response WITH wider dispersion than conventional designs that was important. Not just even power response in and of itself.

So instead of a conventional speaker where beaming is happening by the W and T at the top of their FR, we are trying to beam (or at least tighten directivity) throughtout the FR of the speaker until about the the lower half of the W's passband? Sure power response will be more even through most of the speaker's FR, but dispersion would be less through that same area.

I would think REDUCING the beaming of the T and W in the higher frequencies of their passband would be the way to accomplish Dr. Toole's observations. Not increasing beaming of T at lower frequencies, as would be the case here.

I guess it comes down which is more important: the even power response with wider dispersion, or even power reponse with narrower dispersion. Or maybe just higher dispersion period versus even power response.

As far as dynamics, lower XO, lower distortion, and time alignment, just on those merits I like waveguides. But power response seems very important and that was the subject I'm most trying to understand. Hope that all made sense :E

[augerpro]

Also what are some popular 6" or so wg's available in the US?

[JonMarsh]

Augero,

A dome tweeter has VERY wide dispersion in the lower frequency ranges- in fact, this is responsible for a phenomena called tweeter "flare" in the lower ranges of the crossover, where it's dispersion is much wider than that of the midwoofer in the crossover region in many designs.

Very wide dispersion also increases room interaction, as there are more side reflections from adjacent walls, ceilings.

In my own current project, I'm using a waveguide to lower the workload on the tweeter in the lower part of it's working range, and to control the directivity so that it more closely matches the dipole directivity- where in the lower midrange front to rear cancellation helps match up the directivity with the upper range portion of the middrange driver, and of course the bass range has more limited directivity (and less room interaction) with a figure eight dipole (not U baffle). Reducing the room interaction for off axis sounds means that the direct sound of the recording predominates more. And the room less. IMO, that's a major contribution to fidelity of reproduction, especially for recordings with a true acoustic on the recording (i.e., not multi-mic studio wonders. But even the latter will be clearer sounding).

~Jon

[chasw98]

Here is a question for Jon or anyone with knowledge. Back in the day a company called Community Light & Sound came out with "constant directivity" horns. They were available for compression drivers and even up to 15 " drivers. These were for pro use in sound systems. As time went on, companies like EV and JBL picked up on it and brought out their own version of constant directivity horns. Are these comparable to a waveguide and, if they are, why are all waveguides I have seen very smooth from throat to the outer edges whereas constant directivity horns were always somewhat had a wiggle in their mold to achieve constant FR in all in the vertical and horizontal plane according to their specs? If they are not the same, what is the difference between a waveguide and a constant directivity unit? Thanks!

Chuck

[EdL]

Augero and Paul,

I believe in trying to wrap words around the issue I made a mistake.

"A waveguide will have a greater influence in dispersing the frequencies"

Should have read: "will have a greater influence in controlling the dispersion of lower frequencies".

Thanks to Jon for helping me realize my mistake.

[ThomasW]

Chuck,

I don't know if that's covered in Earl Geddes' book. I was going to buy it, but got lost just reading the table of contents....... 8O

Perhaps someone with the book could comment.

[Dennis H]

Chuck,

Yeah, the current waveguides are a variation on the constant directivity theme. The main difference is one of emphasis. The old ones were trying to get a lot of horn gain so they used a lot of compression in the throat leading to high distortion. Modern compression drivers have much more SPL capability so the emphasis is more on controlling directivity and keeping distortion low than maxing SPL.

About the wiggle in the mold, do you mean increasing the flare rate out near the mouth? That's an effort to reduce reflections/diffraction from the mouth, similar to how a big roundover works. It's a problem with the commercial Geddes-style waveguides I've seen. Geddes stuffs the horn with very low density foam like the stuff JBL used to use for grills. Peavey has an interesting variation where they use higher density foam at the outer edge. An advantage of foam/felt treatments is it keeps the total size of the horn smaller compared to a large roundover or flare.

Quadratic-Throat-Waveguide.pdf

Image not available

[Mark Seaton]

Chuck,

Yeah, the current waveguides are a variation on the constant directivity theme. The main difference is one of emphasis. The old ones were trying to get a lot of horn gain so they used a lot of compression in the throat leading to high distortion. Modern compression drivers have much more SPL capability so the emphasis is more on controlling directivity and keeping distortion low than maxing SPL.

About the wiggle in the mold, do you mean increasing the flare rate out near the mouth? That's an effort to reduce reflections/diffraction from the mouth, similar to how a big roundover works.

As Dennis points out, modern pro speaker designs (there are still many designs in use that are 20+ years old) have their emphasis on directivity control. In some cases you are trying to keep it wide enough at high frequencies, and in other cases you are trying to keep it narrow as possible to keep the interaction with the room and reflections to a minimum.

In the case of the flaring of the end or increased angle at the last 1/3rd of the horn mouth, this is done for two reasons. Reflections from diffraction off the sharp edge transition is one reason, but the other is that with an appropriate driver, a straight walled horn will hold its physical pattern fairly well down to some low frequency. Then at very low frequencies it will of course have no pattern control. Aside from diffraction off the edge of the horn, the flaring of the end of a straight walled horn is an effort to smooth the transition from the horn controlling directivity to not having any.

With a straight walled horn and sharp termination, just below the range over which the pattern approximates the horn wall angle, the directivity will colapse and narrow down and then quickly expand towards point source behavior. By flaring the large end of the horn, this transition can be made more gradual such that the transition is more of a gradual loss of directivity or widening of pattern.

Of course we also aren't accounting for all the peculiarities that happen if you try and deviate too far from a round/squarish pattern and the potential for pattern flip and loss of pattern in one axis before the other.

[Dennis H]

For those who missed it, forum member Mefistofelez posted a link to a nice summary of modern horn/waveguide design written by Jack Bouska.

http://audioheritage.org/vbulletin/showthread.php?t=12967

There's also a DIY section where Jack makes his own waveguides out of solid oak.

http://audioheritage.org/vbulletin/showthread.php?t=12126

[Paul W]

This post is also quite helpful... Tom Danley post

[chasw98]

All very interesting! Thank you all for bringing me back to the current century, but I will have to say that the foam/felt looks suspiciously familiar. Why, it was used on my UREI 813's some 20 years ago as Mark said. I have also used constant D (sounds like a rap name?) horns in churches and auditoriums where you wanted strict control over the patterns to set up intelligble audio. And we used to call some of the larger constant d horns "the lips of God" instead of Jaggers lips. We used several that were 3 to 4 feet wide and 2 to 3 feet tall. Thanks for the answers.

Chuck

[Paul Ebert]

OK, so I think I understand the basis for desiring controlled dispersion.

My next question is: is it better to go dipole in the midrange (with a cone) or to use a waveguide with a midrange such as the RS52? Any clear pros or cons to either approach? Assuming dipole bass, of course.

[JonMarsh]

OK, so I think I understand the basis for desiring controlled dispersion.

My next question is: is it better to go dipole in the midrange (with a cone) or to use a waveguide with a midrange such as the RS52? Any clear pros or cons to either approach? Assuming dipole bass, of course.

That probably dends on what you call midrange and what you call bass...

For me, anything above about 200-250 is midrange, up to about 2-2.5 kHz. YMMV. We did a speaker for ThomasW that was dipole up to 300, then controlled directivity midrange above that. There are probably too many different factors to consider, but in general, I didn't like it as much as I did the Arvo midrange being dipole from 200 Hz to 1200 Hz, as well as lower.

OTOH, I've never heard a midrange dome waveguide setup; keep in mind you could probably only get that to work down to 600-800 Hz, and that would be a BIG waveguide- double or more the size of the tweeter waveguides we're playing around with for 2kHz and above. Then, you'll still need a tweeter waveguide, and a lower midrange (though you might be able to stretch the Aurasound NS12 up that high- it's going to be beaming somewhat by 600. My own measurements show the distortion on the NS12 to be falling steadily all the way up to 1 kHz. I don't know of another 12" driver you might pull off a crossover to a waveguide loaded dome mid. So, maybe you could pull off a three way in that fashion. Would be interesting to see what the tradeoffs are; it would be a pretty tall vertical source at 600 Hz, getting close to a line array, which would mean SPL response would be variable for the system overall depending on distance (line array around 600 Hz, close to point source else where).

Now, how about a stack of 4 NS12's on each side, a waveguide loaded BG RD50, then a stack of ribbon tweeters above 4 kHz?

Oh yeah, better be careful with that idea, that's Evil Twin's Saint-Saens...

[AJINFLA]

The problem with using a WG for a mid (like the RS52) is that you could only use it up to around 7k (or so) at which point you must cross to a tweeter that will be completely decorrelated, seperated by several wavelengths if mounted (for example) above the guide, due to the large guide needed to effectively horn load the bottom end - as Jon points out. Mounting a small tweeter inside the guide (reverse unity style) to reduce CTC would create too many other issues.


cheers,

AJ

[Paul Ebert]

Well, it seems I can rule out the WG mid. Probably a good thing: I don't have to add a whopping lathe to my wish list

Thanks!

[dwk]

The problem with using a WG for a mid (like the RS52) is that you could only use it up to around 7k (or so) at which point you must cross to a tweeter that will be completely decorrelated, seperated by several wavelengths if mounted (for example) above the guide, due to the large guide needed to effectively horn load the bottom end - as Jon points out.

Actually, if you could get 7k out of the mid the 'external' tweeter might be ok - there's so much comb filtering etc going on at that point that subjectively it may work. In my RS52-based Unity prototype though I only managed to get about 4k out of the RS52. Even so a top-mounted waveguide tweeter sounded pretty good, although it certainly wasn't perfect.

This does require a pretty big waveguide, though - I tried an RS52 in a sawed-off PE 12" waveguide, and didn't get much below about 1k with it, so you have to figure 14 to 16" by the time you get some edge transition, at which point you're starting to worry about C-T-C to the midbass.

Mounting a small tweeter inside the guide (reverse unity style) to reduce CTC would create too many other issues.

With the mini neo's that are now available, I think this might be viable but would take some clever construction. Once again it depends on how high you can push the xover, but a small 'pod' formed out of bondo part way down the flare could work.

Of course, given that I threw in the towel on all this and just shelled out $$$ for the real Yorkville Unities, I guess I'm obligated to point out that there are some real practical challenges involved.