DIY Waveguide loudspeaker kit

[Patrick Bateman]

No pricing yet on anything that uses the 15" waveguide because I don't yet have the sourcing for that ironed out. Not too long though.

What would be the interest level in a full Summa size speaker?

You could sell a TON of kits if you did an Abbey with a low-cost woofer. Here's why:

The "real" Summa is a no-compromise design that mates a 15" waveguide & a 15" woofer. The achilles heel of the Summa is the woofer. There are only a handful of 15" woofers which can play into the midrange. The B&C 15TBX100 fits the bill, but it is E-X-P-E-N-S-I-V-E.

The Nathan 10 is a low cost alternative to the Summa; the kit costs less than 1/4 of what the Summa retails for. The Nathan ten has two drawbacks. It offers controlled directivity down to 1400hz, and the smaller woofer can't play as low as the Summa. Of course these are nitpicks; it's IS dramatically less expensive after all. You can save a few bucks by going with Eminence drivers, but why bother? The B&C woofers are superior, and the cost difference is less than 15%.

As I see it, the Abbey has the potential to be the most popular in the line. Here's why:
The Summa offers controlled directivity down to 920hz, while the the Abbey goes down to 1150hz. That's a *very* small difference, less than a quarte of an octave. To me, the most interesting aspect of the Abbey is the choice of woofer. The B&C 12TBX100 is an exceptionally expensive 12" woofer. Retailing for $295 here in the states, there are only a handful of woofers in it's class.

Your own studies have proven that the choice of drivers has little impact in the sound, despite popular belief. For instance, the substitution of TAD for B&C didn't improve the sound. Knowing that, you could easily substitute a dramatically less expensive woofer for the B&C.

For instance, the P-Audio SN12MB retails for half the cost.

I have a hunch that an Abbey which uses a low cost woofer would cost half the price of the Summa, while offering 80% of the performance.

Two other options are the Eminence Kappa 12 and the Deltalite II 12". Each retails for $130, vs $295 for the B&C.

Of course, there's no free lunch. The use of a less expensive woofer has drawbacks. However, I believe they would be all but inaudible in this application. The motor in the B&C 12TBX100 is a real work of art. B&C used a 100mm voice coil so that it could handle shocking amounts of power - two thousand watts! But that single design aspect carries drawbacks. A huge voice coil increases inductance, which then limits how high the woofer can play. B&C puts shorting rings in the motor to counter this.

Compared to the B&C, the Eminence and P-Audio woofers look liliputian. The P-Audio can only handle 600watts, due to it's dramatically smaller voice coil. But there's an upside! The P-Audio offers dramatically lower inductance, less than 1/4 of the B&C. This is easy to explain, there's simply less copper in the voice coil. Lower inductance allows the P-Audio to play a full octave higher than the B&C. Based on published specs, the P-Audio appears superior to the offerings from Eminence. The Kappa 12 has higher inductance, and the Deltalite 12 has similar performance to the P-Audio, but with a dramatic rise in the midrange.

Another upside to the use of a 12" woofer is a simplified crossover, which would further reduce the cost.

If the Abbey kit offers 80% of the Summa's performance for under $1998 a pair, that would be remarkable. And it seems like it's do-able IF the woofer was replaced.

 

[MartinQ]

Thanks for your take on the situation Patrick. Its really great to have an outsiders opinion who is 'in the presence of' a Summa.

The Nathan ten has two drawbacks. It offers controlled directivity down to 1400hz ... The Summa offers controlled directivity down to 920hz, while the the Abbey goes down to 1150hz. That's a *very* small difference, less than a quarter of an octave.

So directivity to 1400Hz is a drawback, but 1150Hz isn't? Is that 250Hz difference (from 10" to 12") more significant than the 230Hz difference (from 12" to 15") ?

You can save a few bucks by going with Eminence drivers, but why bother? The B&C woofers are superior, and the cost difference is less than 15%.

Going from B&C drivers costing $300 per box ($163.03 + $131.96 CDN) to an Eminence set costing $175 per box ($119.99 + $54.99) is significant. I understand it is only one cost out of many, but when you are building 3-channels, all those little bits add up.

If what Earl is saying applies to this specific scenario (about different drivers having almost no sonic impact), then I'd be happy to save over $100 per box at this level. On top of that, my local supplier has a 7 year warranty on the Eminence, but only 1 year on the B&C.

Compared to the B&C, the Eminence and P-Audio woofers look liliputian. The P-Audio can only handle 600watts, due to it's dramatically smaller voice coil.

For an indoor home audio scenario I can't see needing (or wanting) more than 100-300 watt per channel for the mains (subwoofer excluded). I am interested in quality and efficiency, not high power handling.

For a different venue (dj, outdoors, club, bar) I could certainly understand higher power drivers and amps being involved.

 

[gedlee]

All quite interesting.

But here are some points:

1) I never said that the drivers make NO difference only that competent drivers are all equivalent - that the differences aren't noteworthy. P-audio are not competent drivers. I have a closet full of them and not one of them met its "published specs", so much for the really cheap option.

2) You are missing the single biggest reason that I use the 12TBX100, it has a shorting ring. This I consider critical in a "competent" design because quite honestly I can't see why anyone would make a speaker without it. I'll have to look over the Eminence drivers to see if any of the woofers have shorting rings.

3) What I get the drivers for and what you are quoting are not the same thing and it factors into the equation.

4) I have already quoted the Abbeys at $1100 ($2200 / pair) is it really critical to get that last $101 out? I could do it, but I might question the value of that. The Eminence woofers might be a good idea since the ESP12 actually used an Eminence woofer. That change alone would not reduce the price $100 however.

But thanks for the options review. Very interesting.

 

[Variac]

I have to admit that despite what Earl says about it not mattering much , I find the B+C horn driver very appealing. It has a non-titanium diaphram and made by a company with a very good reputation.

I don't think that Patrick is saying that 600 watts will be used, but just emphasizing the quality of the driver. Also a speaker that can handle lots of power has less power compression, which IS relevant,

The Summa has a great reputation. The kits will sell better if they are "Summa clones", not some unknown.

I think that Patrick makes a good point about how the 12" version may require a less special woofer, to get into the midrange, than a 15", so may well be the best value speaker.

However , if the 15" goes low enough to make it possible to enjoy music without a subwoofer, then there is a large savings- even if the sub is a Costco! - less space taken also- better SAF.

So my opinion is that if you have any option, make it an alternative woofer,


EDIT: I was writing this as Earle Posted In answer to his question:
is it really critical to get that last $101 out?

My answer is NONONONONONONO!!!!!!

We want quality- that is the appeal of the Summas
I always want to love Eminence, but my experience with them hasn't been all positive, soundwise..

 

[Patrick Bateman]

Shorting rings lower distortion and inductance right? But a smaller voice coil also lowers inductance. Bastiani and Emerald Physics went this route; each uses a very inexpensive woofer paired to a high quality compression driver.

Admittedly, the cheaper woofer would have higher distortion.

When it comes to the compression driver, there is little excuse to use a $50 CD. First of all, we want very low inductance so that our response is extended. The Eminence is 1.6mh while the B&C is just 0.11mh.
In addition to lower inductance, the B&C uses a diaphragm with superior damping, while the Eminence uses titanium. If people don't like the sound of 1" titanium dome tweeters, they're going to hate the sound of an Eminence CD with a 3" diaphragm!

To make a long story short - it seems that the use of an inexpensive compression driver is a big compromise, but the use of a inexpensive woofer is less so.

Also, 99% of DIYers are complete cheapskates

 

[MartinQ]

To make a long story short - it seems that the use of an inexpensive compression driver is a big compromise, but the use of a inexpensive woofer is less so.

This makes good sense. Again, I'm looking for the best compromise for a given situation, not the cheapest.

Also, 99% of DIYers are complete cheapskates

Totally agree .... not that this is entirely a BAD thing.

 

[Patrick Bateman]

I don't think that Patrick is saying that 600 watts will be used, but just emphasizing the quality of the driver. Also a speaker that can handle lots of power has less power compression, which IS relevant

My main gripe with high power woofers is inductance. Hi-end prosound woofers use a 4" voice coil which drives up inductance dramatically. That limits your high frequency response. The addition of shorting rings offsets this, but increases cost. Even worse, the addition of shorting rings requires a larger motor, which FURTHER increases cost. Take a look at the motor on the 12tbx100 and the 15tbx100 - they're HUGE. And expensive.

Originally posted by Variac EDIT: I was writing this as Earle Posted In answer to his question:
is it really critical to get that last $101 out?

My answer is NONONONONONONO!!!!!!

We want quality- that is the appeal of the Summas
I always want to love Eminence, but my experience with them hasn't been all positive, soundwise..

JBL made a speaker inspired by the Summa, but it's really REALLY cheap. Because the cabinets are crummy, the Summa KILLS it in the imaging department. I've taken my MP215s apart, and the drivers look like little toys. They are seriously the cheapest drivers you've ever seen in your life. But there's an upside to cheap drivers, and that's low inductance. If you look at the power handling of the JBL, it's just 250 watts, which is tragically low in the prosound arena. Yet I think JBL was *forced* to go that route - if they used a motor that was even a little larger, it would have been impossible to mate the 15in woofer to the 15in waveguide without resorting to shorting rings.

Check out the response graphs on the MP215 - you'll see that the cheap 15" they're using is just starting to run out of steam at 1khz. To my ears, the midrange response of the MP215s is pretty damn special, and I believe it has to do with the waveguide they're using, which was certainly inspired by Geddes. In other words, it's the waveguide not the drivers that's magic.

I'd really love to see tons of people with Summas, and it seems like a $999 speaker with 80% of the Summa's performance would be just the ticket.

 

[augerpro]

Shorting rings lower distortion and inductance right? But a smaller voice coil also lowers inductance.

Shorting rings can keep inductance low throughout the cone's stroke though. These drivers may similar or better inductances on paper, where inductance is measured with a small signal, but I ask you: how will they behave when the woofer is actually moving? I think that is where the money is well spent for the B&C driver.

 

[Patrick Bateman]

for some reason the URL for the mp215 isn't showing up properly, here it is a 2nd time

http://www.jblpro.com/mpro/PDF/MP215.pdf

 

[Patrick Bateman]

Shorting rings can keep inductance low throughout the cone's stroke though. These drivers may similar or better inductances on paper, where inductance is measured with a small signal, but I ask you: how will they behave when the woofer is actually moving? I think that is where the money is well spent for the B&C driver.

I'm really cheap, like a lot of DIYers. I didn't buy the Summa because I wanted "the ultimate" speaker, I bought the Summa because I realized that there was absolutely no way that my personal attempts at making a speaker would come close to what Dr Geddes is capable of.

So, absolutely, there are people out there who want "the best."

But there are also cheapskates like me who would be interested in a bit of cost cutting.

As far as the woofers moving, I can barely detect if the woofers are moving in the Summa. If they use 1mm of stroke I'd be surprised. They're sensitivity is so high I can't imagine I'm using more than a watt or three.

 

[Variac]

I do agree with Patrick's analysis, If a compromise must be made that results in a significant cost savings , then the woofer seems the place to do it.

The inductivity issue is very interesting. It is kind of a truism that big woofers with smaller voice coils tend to handle the midrange better.. Maybe I know why now..

The baffles will still be MDF. What else could they be?

I thought that possibly the entire front baffle could be molded with the waveguide. It would have to backed with rigid foam to be stiff though..

 

[gedlee]

Comments:

1) Where the shorting ring is placed determines if it reduces the inductance or not. If its below the VC around the pole, and not too close to the VC then it won't affect the inductance.

2) I prefer the higher inductance on the woofers because I use this in the crossover to help to create a steeper slope. To me its not a bad thing.

3) A copper cap on the center pole is the cheap method of shorting ring, but it robs BL and lowers inductance. Its worth doing on a CD where inductance matters a lot, but the wrong way to do a woofer.

4) The TBX drivers have shorting rings not Copper caps (see http://www.bcspeakers.com/download/comparison/Design.pdf). I need to check on the Eminence drivers.

5) Inductance modulation is a big issue when one takes the woofer as high as I do and I take this into consideration. Inductance modulation is the only loudspeaker distortion mechanism that is broadband and not displacement dependent - it happens with no displacement at all. If there is a nonlinearity in the loudspeaker that would be audible this is the one. Displacement distortion will always have a LF signal component and the upward spread of masking will thus tend to mask its effects. But a current distortion can happens with no masking signals at all.

6) I also would be concerned with a smaller voice coil because of thermal compression - it will be greater. So the larger VC with a shorting ring looks attractive to me. The lowest cost woofer with these features is clearly what I want, B&C or otherwise. I only get dealer pricing on B&C and Eminence, so other drivers thus tend to be out of the picture. I would entertain any woofer that meets these minimum requirements if the price is lower than what I get from B&C and Eminence.

 

[gedlee]

I thought that possibly the entire front baffle could be molded with the waveguide. It would have to backed with rigid foam to be stiff though..

I'm looking into doing this now. The material for casting is expensive - a lot more than MDF, so its a dollars thing. But I tried some things today that look attractive. Casting the baffle instead of MDF is not likely to get the cost down.

What would you guys think of a waveguide or waveguide and bafle that looked like cast bronze? Would that be almost as good as wood? Wouldn't that improve the WAF! "Look dear its a bronze sculpture!"

 

[Patrick Bateman]

I have already quoted the Abbeys at $1100 ($2200 / pair) is it really critical to get that last $101 out? I could do it, but I might question the value of that. The Eminence woofers might be a good idea since the ESP12 actually used an Eminence woofer. That change alone would not reduce the price $100 however.

But thanks for the options review. Very interesting.

I could probably sell ice to an eskimo; both my mother and father were entrepreneurs, so I picked it up at an early age.

Does the last $101 count? Absolutely - because getting them in under $1000 has a strong psychological component.

If you run the numbers, it will look like a bell curve, with a handful of people ponying up for the Summas, a handful opting for the Nathans, but the "sweet spot" is certainly the Abbey.

Again, these are just my opinions, but it seems that The Abbey offers the best compromise between cost and performance. Because of that, eking out a few bucks would certainly result in additional sales. If changing the woofer doesn't do it, I'd start thinking about using smaller inductors in the crossover. True, it increases the resistance, but the cost benefits are substantial, and the effects are less audible than if you used cheap caps.

A $999 Abbey has a nice ring to it.

 

[Patrick Bateman]

Comments:

2) I prefer the higher inductance on the woofers because I use this in the crossover to help to create a steeper slope. To me its not a bad thing.

3) A copper cap on the center pole is the cheap method of shorting ring, but it robs BL and lowers inductance. Its worth doing on a CD where inductance matters a lot, but the wrong way to do a woofer.

4) The TBX drivers have shorting rings not Copper caps (see http://www.bcspeakers.com/download/comparison/Design.pdf). I need to check on the Eminence drivers.

5) Inductance modulation is a big issue when one takes the woofer as high as I do and I take this into consideration. Inductance modulation is the only loudspeaker distortion mechanism that is broadband and not displacement dependent - it happens with no displacement at all. If there is a nonlinearity in the loudspeaker that would be audible this is the one. Displacement distortion will always have a LF signal component and the upward spread of masking will thus tend to mask its effects. But a current distortion can happens with no masking signals at all.

Given two woofers with a conventional motor, one with an LE of 2.0 at 1khz and one with an LE of 0.25 at 1khz, wouldn't it be safe to say that the one with lower inductance will also have lower inductance modulation?

In other words, isn't the amount of inductance modulation relative to the amount of inductance?

Keep in mind, I agree that a woofer with a shorting ring is the best option, if cost is not an issue.

BUT - if you must use a woofer without one to save money, wouldn't you go with the woofer that has the lowest inductance?

This appears to be the route that's been chosen by a lot of commercially successful high efficiency speaker manufacturers. Whenever I go to CES, I'm always astounded by how cheap the woofers are which are used by most of the high efficiency companies.

The $5400 Bastanis Prometheus uses a woofer which looks suspiciously like the $99 Eminence Alpha. (http://www.6moons.com/audioreviews/bastanis/prometheus.html)
Pi Speakers uses Eminence Alpha and Delta (http://www.pispeakers.com/Products.html)
Emerald Physics uses Eminence Alpha. (http://www.polkaudio.com/forums/showthread.php?t=65150)
The venerable Adire HE10.1 kit used Eminence Alpha, with a modded compression driver. (http://www.audioxpress.com/reviews/media/203dell2119-1.pdf)


In fact, I can't name a single high efficiency loudspeaker which uses a shorting ring in the motor - those woofers are just too expensive to be commercially viable.

 

[gedlee]

Given two woofers with a conventional motor, one with an LE of 2.0 at 1khz and one with an LE of 0.25 at 1khz, wouldn't it be safe to say that the one with lower inductance will also have lower inductance modulation?
In other words, isn't the amount of inductance modulation relative to the amount of inductance?

I don't think that this is true. There are a lot of factors involved and I am not sure that the total inductance is the dominate one or even a principle one.

Keep in mind, I agree that a woofer with a shorting ring is the best option, if cost is not an issue.

BUT - if you must use a woofer without one to save money, wouldn't you go with the woofer that has the lowest inductance?

Again, I am not sure thet this what I would do. The concept of squeezing out another $100 is not yet one that I have bought into and how I did that to best advantage would take some study.

This appears to be the route that's been chosen by a lot of commercially successful high efficiency speaker manufacturers. Whenever I go to CES, I'm always astounded by how cheap the woofers are which are used by most of the high efficiency companies.

The $5400 Bastanis Prometheus uses a woofer which looks suspiciously like the $99 Eminence Alpha. (http://www.6moons.com/audioreviews/bastanis/prometheus.html)
Pi Speakers uses Eminence Alpha and Delta (http://www.pispeakers.com/Products.html)
Emerald Physics uses Eminence Alpha. (http://www.polkaudio.com/forums/showthread.php?t=65150)
The venerable Adire HE10.1 kit used Eminence Alpha, with a modded compression driver. (http://www.audioxpress.com/reviews/media/203dell2119-1.pdf)

In fact, I can't name a single high efficiency loudspeaker which uses a shorting ring in the motor - those woofers are just too expensive to be commercially viable.

Can you name another high efficiency system that sounds like the Summa? Maybe there is a reason. Maybe I do things differently.

 

[FrankWW]

John, Remember the woofer has to keep up with the waveguide/CD and this has to happen in a variety of situations the manufacturer can't control.

In this case the manufacturer is aiming at highest performance. That's point of his design.

The limitation in any 2way with competent waveguide/CD is the woofer.

I might want a smaller version of a Summa, but if I do, then I must bear in mind the part that is "handicapped " is the woofer. It's probably more "handicapped" than in the larger version.

So, is cheap, no shorting rings, the way to go if I want optimum performance, given I like like to play big music really loud?

 

[Michael Ando]

Personally I disagree with trimming off every last possible dollar. I think it is a insult to the design not to build it as well as practical. If the cost reduction really makes no difference its ok or maybe a very little difference for a lot of money. Thats not the situation here where the difference in cost between drivers isnt much in the context of high quality speaker systems.
I do diy for personsal satisfaction and to get things that I cant buy. I am not saying price isnt a consideration but if I go to the trouble to buid a pair of loudspeakers I want to feel I didnt compromise the design. Dr Geddes has said he believes he has designed speakers that perform at a very, very high standard...they shouldnt be comprmised for the sake of a few dollars. Mike A

 

[tinitus]

Lets be honest now
Earl is doing this in the hope of jumpstarting his Summa production, not to make a few bucks on cheap kits, and I think its ok that we "help" him with that getting the oppertunity to buy first rate quality kits, right
I think Earl has a name to protect, which is why he shouldnt compromise his design
I probably cant even afford to buy a waveguide because of expencive shipping, custom and taxes
but I can tell you that, if the product wouldnt be first rate quality I wouldnt even consider it

 

[audiokinesis]

Patrick, I agree with Earl on staying with woofers that have shorting rings instead of compromising to meet a psychologically attractive price point. In my experience, shorting rings make an audible improvement (I can give anecdotes if you'd like).

If I were in Earl's shoes, I wouldn't make what I thought was a significant compromise in sound quality to meet a target price. Maybe that's why neither one of us have gotten rich selling speakers yet! But, I presume it matters to Earl that his name only be attached to products which he has no reservations about.

edit: In my opinion Earl's market is the educated customer; that's why he has found success here rather than in traditional high-end audio (which is less educated): You guys are very deeply interested in the technology of acoustically and psychoacoustically advanced loudspeakers.

Duke