The Tower Discussion Thread!

[davef]

Can anyone tell me if the bamboo used is a solid core or a laminate of veneer slices? Thanks.

Hi ToneDef,

The bamboo we use is solid, we do not use any veneer. We use what is called 3/4" edge grain solid-stock, sometimes also called vertical grain.

[parimento1]

Thought I would share a fun photo with everyone.

Here is a batch of our customized RAAL 70-20XR Amorphous Core ribbons getting ready for testing for later this evening and tomorrow morning. Every ribbon is tested for rub and buzz, listened to by me during a specially designed sweep, and tension tested. Although quite rare with our shipments, if any ribbon is even slightly off, it is set aside for diaphragm replacement and then tested again.

All of this occurs before the ribbon is even installed into the speaker, at which time it is then thoroughly tested again with a variety of measurements.

Forgetting the price, but I wonder what a RAAL ribbon line array would sound like? Strange thinking about it... but I could go out and purchase a really REALLY nice car for the amount this batch of ribbons cost

I get more enjoyment from music though

Enjoy!

What is the difference between these ribbon tweeters and the ones like the the X-Art tweeter by Adam Audio or the ones used by Legacy audio. Just curious.

[davef]

What is the difference between these ribbon tweeters and the ones like the the X-Art tweeter by Adam Audio or the ones used by Legacy audio. Just curious.

The differences are significant. A "true" ribbon tweeter, like these RAAL's, have only a single moving part -- which is the actual ribbon, also called the diaphragm. The ribbon in the RAAL's is set between insanely powerful magnets. Current from the source flows directly through the diaphragm itself, which causes it to move back and forth and generate sound. Because of this, the moving mass is as low as physically possible (aside from a plasma tweeter) which translates to the lowest levels of inertia, stored energy and fastest start and stop times (transient response).

The latest iterations of these AMT ribbons (Air Motion Transformers) are quite different in design. These use folded pleats (think of them like an accordion) that squeeze the air in between the pleats thus creating sound waves. A voice coil is imbedded into the diaphragm material so that current can travel through the material and force the cleats to expand and contract. This type of tweeter, in my experience, has more limited horizontal dispersion compared to our true ribbon and also has significantly higher mass and less high frequency extension. One benefit of these types of ribbons is that they have a lot of radiating area (due to the folds) and in general, can handle more power and be crossed lower than a typical true ribbon or planar magnetic tweeter, the exception to this is the RAAL 70-20 which can handle an insane amount of power and be crossed as low as 1800Hz.

My first experience with AMT tweeters was with the ESS AMT1 way way back in the mid 80's. I was a tech at a rather famous/infamous audio chain and we sold the AMT1's. They were way ahead of their time but back then, unfortunately, people wanted loud and dynamic while the AMT1's were clean and detailed, even at loud volumes they did not sound loud. Cerwin Vega was big in those days... However, the AMT1 gave me one of my first tastes at what true HiFi was about so I have fond memories

Back on topic, I generally prefer a well implemented AMT design to planar magnetic designs -- neither of which can really compare to the RAAL 70-20, both in listening and measuring.

[davef]

Ps: I counted ~46 RAALs in that pic....quickly doing the math..yup nice car indeed...lol..

My RAAL STC is expected to arrive on the 23rd along with the 200se...can't wait.

52 ribbons to be exact... and would you believe that after today, this batch is now 80% sold already? Crazy...

Dave could you elaborate on the pros & cons or subtle differences found between the RAAL 70-20xr vs. 70-10 version having tested both? I'd just like to hear/read your opinion on this matter?

I have spent a lot of time evaluating these two ribbons (as well as other RAAL’s) and I am happy to discuss and lay down some facts.

The 70-20 is Aleksandar’s pride and joy. It is a technically more advanced tweeter with some features and performance that RAAL does not want in the public domain, which is the reason it is only available for purchase by qualified OEM’s. You will never see it available for sale at Madisound, for example. It has twice the radiating area of the 70-10 which allows this tweeter to effortlessly reproduce the upper mids and lower highs with lower distortion and superior dynamics, which is one of the reasons why listeners almost immediately notice smoother, effortless vocals. The tweeter is also capable of being crossed over at 1800Hz, which allows directivity matching to larger midrange woofers – while also allowing more of the upper mids to be reproduced by the ribbon (which is a good thing). Even with the lower crossover, the 70-20 is capable of handling 25% more power than the 70-10, regardless of where the 70-10 is crossed.

The 70-20 also has a considerably "flatter" high frequency response compared to the 70-10, which has a rather pronounced tipped-up response, this is the reason it includes acoustic foam. Some would call the use of this foam a feature of the tweeter, but it isn’t, it is used to compensate. Any engineer or even any consumer can add acoustic foam to any tweeter to tailor the highs to their liking – I did just that on several M&K models I worked on many, many years ago. Foam causes other issues and my preference is the less tinkering required, the better the overall performance and longevity.

Additionally, a unique feature of the 70-20 that is seldom discussed is that the transformer is wound with a specific inductance that electrically matches the inherent acoustic low frequency roll off of the ribbon itself, the result being that when combining the acoustic and electric slopes, the tweeter has a smooth 3rd order built-in high pass. This is extremely worthwhile as it allows the crossover to use a single series capacitor to create a true 4th order L/R HP filer, which typically takes 3-4 components in the crossover. This eliminates crossover parts which further enhances signal purity and the “less is more” paradigm.

The only advantages the 70-10 has over the 70-20 are that it is quite a bit less expensive and the smaller width of the 10mm diaphragm (as compared to the 20mm width) provides for wider horizontal dispersion. I am not sure there is any audible advantage to this though, in fact, it can be detrimental in smaller rooms as it will cause more high frequency reflections off side walls and high frequency directivity should match midrange directivity as close as possible. You don’t want an exceptionally wide response from the tweeter and a more narrow response from the midrange driver. This is one of those characteristics that will be debated forever, some designers prefer extremely wide, others prefer higher directivity.

In evaluating these tweeters, the deciding factor for me was the polar response of the 70-20 when mated with a 5 ¼” midrange driver. We were able to cross at the ideal frequency and combined with the directivity of the 20mm ribbon, the result is a nearly perfect polar response, free of any upper midrange / lower high “blooming”.

Please don’t misunderstand me, the 70-10 is a fantastic tweeter and if the 70-20 did not exist, we would probably be using it. However, there is a reason that it has become the high-end tweeter of choice for companies like Salk, Selah, Vapor and others… It is really very special and even 2 years later, the most “technically correct” tweeter I have ever come across.

[parimento1]

In evaluating these tweeters, the deciding factor for me was the polar response of the 70-20 when mated with a 5 ¼” midrange driver. We were able to cross at the ideal frequency and combined with the directivity of the 20mm ribbon, the result is a nearly perfect polar response, free of any upper midrange / lower high “blooming”.

I have the RAAL towers and am amazed at the integration of the ribbon tweeter with the cone midrange and woofers. How did you work this magic, so that the ribbon tweeter so neatly integrates with the other kinds of drivers? Many speakers I have heard with ribbon tweeters tend to call attention to themselves and "stick out" sonically from all the other standard drivers.

[Kisakuku]

I have spent a lot of time evaluating these two ribbons (as well as other RAAL’s) and I am happy to discuss and lay down some facts.

David, thanks a lot for such an informative write-up. Would you be able to offer an opinion on theoretical advantages and disadvantages of sealed vs open-backed enclosures for midrange drivers and how they would apply to your particular design of RAAL towers (tweeter covering a lot of upper midrange, bamboo cabinets, etc.)?

[SteveR]

I finally finished my per-order...took a while to work it all out but I think it will be a Stellar setup.

Fronts: Matte Black Towers and Horizon all RAAL
Front Wide: Matte Black Sierra-1 (basic tweeter)
Side and Rear Surrounds: 200SEs
(2) FS-12s one front and one rear

Pre/Pro: Integra DHC-80.3
Amp: Integra DTA-70.1
Blu-Ray: Oppo 103
Projector: JVC-RS4810
Screen: TBD

The rest of the house has a Control4 home audio/video system with several wire runs (2-RG6, 4-Cat6, 2-low voltage bundle) to each possible TV location as well as wireless and wired internet. I had the place wired like crazy for possible upgrades in the future as well as open conduits to several key rooms and the head end in the HT room. It is painful now ($$$) but will be worth it as this is our home for many years to come. We are both retired and plan on staying in this house for a very long time so making it easily future up-datable was a key issue for me.

There are 9 audio zones in the house; each independently controlled.
There are 6 audio zones in the house; each independently controlled.
Each major room has a RG6 and RG45 plug as well as telephone. Some rooms have on-wall volume controls while others use a universal remote. There is a central keypad for the house system and a dedicated remote for the Media Room.


Now to get it all shipped and installed once we move in!

The house is 6-7 weeks from completion and we can hardly wait! Living in a RV for 6 months with two dogs in a cramped RV park is a bit stressful. Not to mention the lousy speakers and sound system in the RV.

Thanks to all the kind folks that have provided advice and support through this difficult but exciting experience of starting all over with my HT/audio system. Everything is a compromise of some type and all we can hope for is that all the compromises blend into a system that does what we want with the quality we can afford with the sound and video experience we envisioned.

I will follow up once it is all installed...in a couple of months.

[jm78]

I can't seem to find high gloss cherry or high gloss expresso pics.

Also, would the cmt-340se or sierra 1 sound that off as a center with the sierra towers with nrt tweeters? Hmm, get the sierra-1 with nrt tweeter, so at least tweeters are the same as towers. Or cmt-340se with greater output, maybe has more chance matching the towers.

Man, I would love the horizon center but I think it would either blow my budget or break my tv stand, lol.

[jm78]

Ughh, read a lot of this thread. So much RAAL love, poor NRT, and poor me not enough money for RAAL.

[Sam1000]

I finally finished my per-order...took a while to work it all out but I think it will be a Stellar setup.

Fronts: Matte Black Towers and Horizon all RAAL
Front Wide: Matte Black Sierra-1 (basic tweeter)
Side and Rear Surrounds: 200SEs
(2) FS-12s one front and one rear

Pre/Pro: Integra DHC-80.3
Amp: Integra DTA-70.1
Blu-Ray: Oppo 103
Projector: JVC-RS4810
Screen: TBD

I have a similar setup. (RAAL towers across the front and 200Se for surrounds + Rythmik + Integra 80.2). You are going to love it :-)