a DIY rant

[lsiberian]

Some folks think wheat bread is better for you than white. Who am I to argue with psuedo-science and marketing teams? People despise science they embrace psuedo-science.

 

[Swerd]

View attachment 11527
The true end of Upgradeitis

A speaker like this will sound like crap unless you have one of those impossible-to-find flux capacitors.

 

[dnewma04]

I ran across this thread and can shed a little insight, not as the poster in the referenced thread, but as someone who is a fan of the approach he is taking and some of his equipment choices so bear with me. I'm not offended by being grouped with him or of the disdain for his approach, but I think there is at least some misunderstanding being displayed here. It might take a couple of replies to address the issues.

First, the 15" woofer he chose is about as good as it gets in my experience for his application. This is no typical pro audio driver, it was intended for home audio applications and just happens to work very well in PA systems, as well. It uses an old Altec cone profile, that when coupled with the phase plug shape that was chosen provides excellent performance (even off axis) compared to any other 15" driver I've encountered. It's pretty well flat to 1500hz even at 45 degrees off axis. On axis, it's well behaved up until about 4khz. It's very low and consistent inductance keeps performance consistent even when the volume knob moves towards 11. It displays lower power compression than any driver I've ever encountered. Even at rated power (500w), it's power compression is significantly better than most of it's competition at much lower power levels. I believe the JBL 2226 shows almost 3dB of power compression at 500w compared to about 1dB for the AE TD15M. The consistent and low Le makes it one of the easiest drivers to work with, as well. It's impedance is smooth consistent for a much wider range than even most smaller drivers making it easy to drive and easy to work with. In short, it's the best midbass driver I've ever used in any of my designs. It's dynamic ability is unparalleled to a degree that listening to some traditional favorites for midbass leaves me flat now (including dynaudio, seas excel, scanspeak revelators, and even some PHLs).

Second, if there is an issue with his design, I'd suggest that it's that his chosen horn isn't an ideal match for the midbass choice. The directivity match won't be as ideal as the transition from a 10" driver to the chosen waveguide. The superb off axis performance of the TD15M mitigates some of the issues, but they are still there. The coverage window won't be quite as wide vertically with a 15" driver but as long as you aren't using them as near field monitors, even this shouldn't be an issue in a normal room. The SEOS-12 + compression driver (actually, any of the SEOS designs) delivers very smooth and very consistent performance over a wide range. I've seen them used as low as 1200hz with the right compression driver choice and they are almost uncanny in their ability to sound the same anywhere in the room rather than the typical dome tweeters off axis performance being tonally different than it's on axis performance. There is a lot to be said for the constant directivity approach, especially in terms of mitigating room acoustics issues.

To address the original rant and to confirm some of the issues proposed, I do have to mention that I was a long term horn hater and believed that pro audio parts didn't belong in a typical listening room. This was often confirmed by listening to things like Altec A7s in basements and small rooms, or Klipschorns, etc. About 13 years ago, I had the opportunity to hear some Lambda Acoustics Unity Horns. I had very low expectations going in for the horn piece but knew I liked the woofers. Frankly, I was blown away and I heard them in two settings, in a large warehouse and in a intimate living room setting. There was no sense of the speaker being too large for the room, just the opposite. It sounded like I was listening to a small monitor speaker with a soft dome tweeter, but just with what felt like unlimited dynamics and scale. I'd never experienced anything like it, they just disappeared despite being physically overwhelming. The effortlessness has been unmatched to this day and it set me off on a quest to find out what was responsible for the performance. With a bit of elevator thinking and some actual research into small room acoustics, I've pretty well determined that my preconceived notions that big speakers can't work well in small rooms has been proven wrong. This isn't to say that listening to some LaScalas in a 12x10 living room wouldn't be painful, or that horns in general work well in small spaces, but a very good waveguide with constant directivity and smooth response can work superbly in small rooms because of their ability to dminish many of the problems we typically face with early reflections, for instance.

If I had even a small bit of advice for him, the only thing I would have suggested is to bump up to the SEOS-15 or SEOS-18 for a more ideal match.

I think many of you would be stunned by the performance he could achieve with those parts.

 

[dnewma04]

I think I understand the general idea behind controlled directivity, but I don't get:

Very good list of questions:

• Why a compression tweeter in a CD mount would sound better than a more typical tweeter on a flat baffle.

I don't know that it's really the compression tweeter that makes it sound better, it's the waveguide. Waveguides can be effectively used with dome tweeters, as well. What they allow is very wide and constant dispersion. Typically, a dome tweeter will do well on axis and even do pretty decently off axis to some degree, but their off axis performance will always differ from low frequencies to high. They will have very wide dispersion at lower frequencies that diminishes as the frequency goes up. The problem with this is that the reflected material in the room will have a different sonic character than the direct sound. I don't know if there is individual sensitivity to this, but I've often heard this contribute to the head in the vice quality that many speakers have (including many horns).

• Why PA speakers better suited for large auditoriums would sound better that home audio speakers in a home setting.

I'm not sure they are better suited for large auditoriums compared to small rooms, as opposed to better suited to auditoriums than smaller speakers. I think there is an important distinction between the two. While a small 2 way is unsuited for an auditorium, a 15" woofer isn't necessarily unsuited to a small room, unless of course, you are trying to cram some 30 cu ft speakers into a 500 cu ft room. PA speakers can have advantages in terms of power compression, as well, for those listening at a high level. I know I go a bit over the top, but when I design speakers, I tend to make what I refer to as 20 or even 30dB speakers. I want to build a design that is capable of peak output significantly higher than my average level. (I go over the top and typically try for 30dB). This doesn't mean I listen loudly, but I do have a couple of pieces of music with 25-28dB crest factor and if I want to turn the volume level up, I don't want my speakers collapsing.

• Why anyone would try and use a 15" woofer in a 2-way even if the tweeter might go as low 1 or 1.2 kHz.

As I mentioned in my last post, I'm not sure this is an ideal matchup, but because of the specific driver chosen, I bet it fairs very well. If someone wanted to use an Eminence or JBL in that same application, I may caution against it. For whatever reason, the TD-15M does a lot of things very right.

I think the last point to make about pro audio drivers is that they often exhibit measurably better distortion performance than home audio equivalents.

I also believe that a healthy dose of skepticism is important and would encourage anyone who gets a chance to hear for themselves what a high end modern horn system (using quality waveguides) is capable of. It still may not be your thing, but I suspect you may be surprised.

 

[connieflyer]

I would like to add my two cents worth about horn speakers if I may. I have been around audio since the 1950's and have heard and experienced some really neat systems. My first expweience was tearing apart an old floor standing radio (yep state of the art back then, I was 14 at the time. I fixed the tube amp and took the speaker out of the cabinet and it sounded really good. Well ok I had to put my ear almost down inside the cone, but for that time period what can you expect, so after going with several well known brands (later inlife of course) including Wharfdale W 40D's and W60"s then on to jbl's in the mid 60's I aquired a pair of new Electrovoice EV Sentry 5's I have used these ever since. They have 10" woofer and a horn driver and the clarity for vocals still amaze me. They are currently my secondary system back in the computer room repaced by 5.1 PSB's but still spend alot of time listening to the EV's. F0rty years old and srill going strong. Obviously they have been surpassed by new designs but the sound of these still captivate me, they are powered by a H-K avr501. Just my experience with horns so you have to find a good pair and then make a judgement call. Thanks for reading. Don

 

[dnewma04]

Some folks think wheat bread is better for you than white. Who am I to argue with psuedo-science and marketing teams? People despise science they embrace psuedo-science.

The science behind constant directivity horns is solid, established and well understood. The same goes for small room acoustics. A great deal of the SEOS waveguide projects you'll find on the internet are based on this. If you were implying that it's pseudo-science, I'd suggest you take another look.

 

[dnewma04]

Thanks for putting it that way. It made me think about what got me mad enough to start this thread.

Even though the dude is still in the "Garage speaker 101" stage, I wasn't really annoyed at him. I don't know about you , but most of us were at that stage at some time in the past .

What set me off on that rant was that everyone else in that thread so readily agreed with him. No one addressed the critical question of how can you successfully cross over that 15" woofer to that tweeter. Instead, most posts I saw talked about how to cross over that 15" woofer to a subwoofer! Apparently he plans on SIX subwoofers. In a room less than 11' wide, where are all those dog house sized cabinets going to sit?

I think the people in that thread are aware of the performance of the TD15M and may have cautioned against the use for another 15" driver. For the subwoofers, I didn't look closely, but if he is using multiple subwoofers, he may be using a distributed bass system, which is another well established tactic to tackle issues in small room acoustics. Eigenmodes in the room dominate the sound from about 200hz down in a typical listening space. You can attempt to control them passively with room treatments, but those tend to be very large and only moderately effective. With distributed bass, you tackle eigenmodes more actively and consequently, more effectively than passive means. If he was stacking up 6 subs in one spot, then he's simply going for output and presumably low distortion. In any case, there are solid reasons why someone would choose to use multiple subwoofers. Like the Lambda Acoustics Unity Horn system, distributed bass done right was an eye opening experience that won't be going away for me any time, soon. I can't imagine a scenario where I'd be without at least 3 subwoofers despite having 15" drivers that play comfortably down to 35 hz. And in the case of distributed bass, it really has very little to do with output, it's about quality and consistency of the bass response in the room. In my last house, I went from 30dB swings in output in room to 18dB with passive room treatments. Going to a distributed bass system by itself brought me down to 8dB differences. Adding passive room treatments back into the mix had me down to about 4-5dB.

 

[dnewma04]

It almost seems like a case of "mine's bigger than yours". I can't really understand why people ever used PA speakers in the home, unless they have a MASSIVE room and want high SPL. I've had a few people buy stuff from me for that reason, but I can count them on one hand.

The QSC K series is very nice, but from my experience with it almost any decent "home" speaker can beat it in SQ. Don't get me wrong, the K series is fantastic for a PA speaker, but even for PA usage they are limited on output. Using two K12's and two K subs we got them to choke when the SPL demand got high enough. All depends on the music we played, but anything with lower bass was a no go. They got a bit harsh at the top as well, but that was at VERY high SPL.

If you ever get an opportunity to listen to a Yorkville U15, try to do so. It's not quite as refined as some high end horn systems I've heard, but for a commercial PA product it gets very close. It's capable of superb performance but isn't particularly cheap.

 

[lsiberian]

The science behind constant directivity horns is solid, established and well understood. The same goes for small room acoustics. A great deal of the SEOS waveguide projects you'll find on the internet are based on this. If you were implying that it's pseudo-science, I'd suggest you take another look.

I'm not sure you understand the point of the thread. It's not a knock on horns in general, but I've seen no reason to pick horns over traditional speaker design in a home theater. I can understand if a person likes horns, but to me they are more trouble than they are worth. Horns are great for pro-audio of course, but I don't see a place in home audio for them personally. I doubt they offer any real advantage over traditional builds in typical home theater applications other than efficiency.

Waveguides are certainly helpful especially in center channels, but I'm not sure they are really worth the effort either.

Instead of implying we haven't done our homework. Why not link project and studies that support the position so we can have a more constructive discussion?

 

[dnewma04]

Sure thing. Earl Geddes is a good starting point. A forum member named "Zilch" did a lot of work implementing the technology from JBL, Geddes, and others. There are threads all over the internet about "econo-waveguides" or econo-waves with loads of measurements and reviews.

Geddes on Waveguides - diyAudio
http://www.gedlee.com/downloads/directivity.pdf
www.gedlee.com/downloads/Audio Acoustics 6 12 05.ppt‎
http://www.pispeakers.com/Pi_Speakers_Info.pdf

Sorry about the implication, it wasn't mean to be insulting so much as a heads up that things have come a long ways since what many of us first experienced with horns and further, that the chosen components actually do work well together. None of us have time to hear or read up on everything and I'm sure there are loads of subjects I have opinions on that are based on soemthing other than all of the information.

In the past, even the best horns provided some coloration to the sound that many found undesirable, even if the horns were CD. The newest waveguides have seemingly solved most of the coloration issues which really leave physical size as one of the only real limiting factors in their use.

Also, I'm not knocking anyone's personal preferences here. If traditional format speakers satisfy your needs, I don't see any reason to choose anything different, either. There are some inherent advantages (just like anything else) of using waveguides, however, and I don't think it was fair to think that the designer or responders to that thread were not very experienced or savvy as some had implied.

 

[Swerd]

dnewman04, thanks for your effort at making a reasoned contribution to this aging thread.

You might find more to read about this subject (and my strong dislike of most horn/waveguide speakers) here:

http://forums.audioholics.com/forums/loudspeakers/85105-what%92s-deal-speakers-horns.html

 

[dnewma04]

Thanks for the link, Swerd! Let me have a look.

 

[GranteedEV]

running the TD15M up to about 1khz is not ideal since it has a (benign/controlled) breakup frequency about half an octave above that (~1.6khz) That said, it's no different from running the typical 6" paper woofer up to around 2.5khz while it is in breakup in the ~3khz+ region. You know, like crossing a Seas ER18 to a Fountek NeoCD3.

 

[ski2xblack]

Since this still seems to have some life, I would like to hear dnewman's and Not Grant's take.

In addition to the directivity mismatch of the drivers/waveguides of the speaker that inspired this thread, there is another thing that I have noticed which, if it were my design, would have been avoided or at least received serious attention. Specifically, in my experience auditioning, owning, and Tool-Timing horn/waveguide speakers, they seem to benefit when frequency divisions between drivers are located well outside the frequencies where our ears are most sensitive. Am I off my rocker here? I think I would want a big ol' waveguide for everything from 400-500 hz up to 6000 hz or higher, leaving the critical mid-range unadulterated by phase shifts and other passive network nasties. That would mean either a three-way, or a two way with a much larger horn/waveguide.

I also wonder if Dennis Murphy ever received the drivers/SEOS from the diysoundgroup folks. Would love to hear his feedback on the real world results for this stuff.

 

[Swerd]

Since this still seems to have some life, I would like to hear dnewman's and Not Grant's take.

This was originally my rant. That qualifies me to comment .

In addition to the directivity mismatch of the drivers/waveguides of the speaker that inspired this thread, there is another thing that I have noticed which, if it were my design, would have been avoided or at least received serious attention. Specifically, in my experience auditioning, owning, and Tool-Timing horn/waveguide speakers, they seem to benefit when frequency divisions between drivers are located well outside the frequencies where our ears are most sensitive. Am I off my rocker here? I think I would want a big ol' waveguide for everything from 400-500 hz up to 6000 hz or higher, leaving the critical mid-range unadulterated by phase shifts and other passive network nasties. That would mean either a three-way, or a two way with a much larger horn/waveguide.

You've hit on the $64,000 question in speaker design. How can a crossover do it's job without creating an negative impact on the speaker's sound?

I have seen designs that do achieve flat frequency response in the crossover region and largely deliver on the promise of an inaudible crossover. It involves careful choice of drivers, using only the frequencies where they have wide off-axis dispersion and little or no distortion or break-up noise. This usually requires small woofers to maintain wide off-axis dispersion, and crossover frequencies to the mid or tweeters well below where break-up noise begins (for woofers) or well above where low frequency distortion can be heard (for tweeters). When designing the crossover itself, care and attention must be paid to keep the roll-off curves on both sides of the crossover as smooth and symmetric as possible, and to avoid rapid shifts in response phase angle in the crossover range.

Easier said than done. The basic idea is to stay within the comfortable range for a driver and avoid getting greedy.

You are not off your rocker, but I don't know of a midrange with waveguide that can handle 500 to 6000 Hz. If you go from 650 to 3000 Hz, you'd have the midrange of a Philharmonic 3-way .

I also wonder if Dennis Murphy ever received the drivers/SEOS from the diysoundgroup folks. Would love to hear his feedback on the real world results for this stuff.

Until I hear otherwise, I think his silence on the subject tells us all we need to know.

For grins, Dennis recently showed photos of this speaker he worked on (read about them starting on post #4063 of this thread Philharmonic Audio - Dennis Murphy). It was a custom crossover job for someone who built what became named the "PhilharMonster". It is not something he will offer.

I show it only because it was meant to be a high sensitivity design, and it uses horn/waveguide mounted compression-type tweeters. Note that these tweeters were crossed over much higher than in a typical constant directivity 2-way design.

 

[GranteedEV]

<quote>

if it were my design, would have been avoided or at least received serious attention. Specifically, in my experience auditioning, owning, and Tool-Timing horn/waveguide speakers, they seem to benefit when frequency divisions between drivers are located well outside the frequencies where our ears are most sensitive. Am I off my rocker here?

</quote>

Not if it's a Synergy horn

You probably know about my current project, and I'll say more when I learn more

I show it only because it was meant to be a high sensitivity design, and it uses horn/waveguide mounted compression-type tweeters. Note that these tweeters were crossed over much higher than in a typical constant directivity 2-way design.

The TPL-150 is a pleated diaphragm air motion transformer, not a compression tweeter.

 

[ski2xblack]

The Volti speakers discussed previously exemplify the freq band divisions I refer to, as do Khorns, 'Scalas, and passive two-way Jubilees for that matter. All of the SEOS based two ways have the crossover smack in the middle of the mid-range.

Grant-not-grant, I will be paying attention to your build!

 

[revive]

Great conversation and so interesting to see how far we've come - many home theaters now employ Constant Directivity Waveguides and Compression Drivers paired with exceptionally performant 10,12 and 15" mid woofers - usually to then be coupled to an insane subwoofer array.

 

[Verdinut]

Great conversation and so interesting to see how far we've come - many home theaters now employ Constant Directivity Waveguides and Compression Drivers paired with exceptionally performant 10,12 and 15" mid woofers - usually to then be coupled to an insane subwoofer array.

That's a 2013 thread. It has to be abandoned.

 

[highfigh]

Great conversation and so interesting to see how far we've come - many home theaters now employ Constant Directivity Waveguides and Compression Drivers paired with exceptionally performant 10,12 and 15" mid woofers - usually to then be coupled to an insane subwoofer array.

I know this is an ancient thread, but where did you get your information?