single versus dual drivers for dipole speakers

[Poultrygeist]

A tube used as a phase plug. The tube pins are held in by magnetic attraction.

 

[john11]

Hi. Thanks for the reply.

I'm thinking about using two visaton b200 per channel as high and low midrange drivers, dividing the midrange into 100hz-1khz and 1khz to 6khz and sending set one to each driver.

Do you think this is a good idea.

One driver by itself has difficulty reproducing the entire audio spectrum, divide the spectrum into two or three so that the bandwidth of sounds sent to each driver is decreased i find lowers distortion and increases sensitivity.

But what do you think about four way.

Does going one step further help to improve audio quality

I did this last week and noticed more detail coming from the speakers

I used my usual rel sub and b&c tweeters, then an audax mid between 100hz and 6khz, sounded good, then going up to four way with another audax mid inserted brought even out more detail.

Do you think this is a good idea with the visaton b200, not sure as this is a better driver than my audax units and may be able to go from 100hz to 6khz without need for further assistance.

Many thanks. John.

 

[Poultrygeist]

I've tried tri-amped 3 ways using an electronic crossover and found it to be a connection nightmare. The juice wasn't worth the squeezing. One full range speaker with bass support is the common practice. It's what you see 90% of the time and it's the route that experts like MJK and Nelson Pass choose to take.

 

[Poultrygeist]

I have a friend on another forum that used this folding wing design but increased the baffle width enough to fit a 15" Eminence Alpha woofer below each B200. He still loves it after 7 years. There's no perfect speaker design just compromises. You lose some things to gain others. As simple as possible is always the best approach.

http://www.6moons.com/audioreviews/roadtour5/roadtour5.html

http://www.wildburroaudio.com/index.php

 

[john11]

Okay, got the drivers through today and have set them up but they sound awful.

The audax drivers i was criticising earlier sound like heaven in comparison.

I read the visatons benefit from some burn in time and improve.

I hope they do improve but it needs to be a massive improvement just to bring them up to the audax's

What do you think, if the burn gives a slight improvement only i am in trouble just spent over £400 for nothing.

 

[Poultrygeist]

Can you post a picture of them mounted in the baffle?

 

[TLS Guy]

Okay, got the drivers through today and have set them up but they sound awful.

The audax drivers i was criticising earlier sound like heaven in comparison.

I read the visatons benefit from some burn in time and improve.

I hope they do improve but it needs to be a massive improvement just to bring them up to the audax's

What do you think, if the burn gives a slight improvement only i am in trouble just spent over £400 for nothing.

Burn in is a myth. You have what you've got. I warned you earlier about this simplistic plan.

If it was that easy to build a speaker by putting drivers on a flat board we would all do it.

The fact is that building a speaker is a complex mix of science and art.

However, you have to build with some principles and concepts in mind. The first is that the cone of a moving coil loudspeaker is a terribly inefficient coupling to an acoustic space in the lower frequencies. When you put it in open baffle you have the added problem of additions and cancellations from the front and rear radiation. To deal with the latter complex electronic equalization is required. This has to be active and NOT passive.

As far as bass, even closed box designs require equalization to get deep bass. Moving coil transducers ideally do require acoustic transformers to aid them to output decent bass. This can be reflex (ported), TL, or horn.

The next issue is full range drivers. There are practically none, and none suitable for open baffle. You may have posted a picture of Nelson Pass with a Lowther driver on a flat baffle. However that is just daft.

The Lowthers are very efficient high sensitivity drivers. This makes them low Q drivers. So the cut off very high without the proper loading. They are designed to be loaded by very efficient horns to give acceptable bass response. I'm very familiar with these drivers. I grew up in the Medway Towns in Kent, not too far from Bromley. The late Donald Chave who took the company over form Paul Voigt, was one of my close group of mentors those many years ago.

The next problem is that single full range drivers have to cope with the problem of cone break up. They all do. This results all too often are an irregular frequency response and beaming. Even the famed Lowthers are not immune form this, but way better than most.

The only full range driver I have know to sound good is this one and its close relatives. However this is the one I like the best, the Jordan Watts module.

The major secret is in the design and manufacture of the cone. It break up in a highly controlled fashion with radiation area decreasing linearly with frequency.

However you could not load this speaker on an open baffle. It would destruct pronto. Properly loaded they have a remarkably good bass response.

Unfortunately for you the result you have got, is exactly what I predicted.

So you will have to chalk this one up to experience and move on. Those of us that build speakers have all built some dogs. Remember you almost always learn more from what goes wrong, then goes right. However you must first learn why your project failed before moving on to the next.

One last point, don't blame the driver, blame your application primarily. I don't know that driver, but may be with the right design and application it could be part of a good speaker system.

 

[Poultrygeist]

There is no burn in with speakers but many FR drivers do require mechanical break-in of the suspension. A Fostex FE126En never sounds very good out of the box but comes into it's own after a couple hundred hours.

To quote Siegfred Linkwitz, co-inventor of the Linkwitz-Riley filter: "It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker".

 

[Poultrygeist]

Visaton B200 over H-frame OB woofers.

 

[Poultrygeist]

Visaton B200 on flat baffles with Eminence Alpha woofer augmenting the bass.

 

[Poultrygeist]

Rather than designing your own OB's it makes more sense to copy a proven design. Here's another that uses the B200 and Alphas.

http://taooftubes.blogspot.com/2011/01/visaton-b200eminence-alpha-15a-speaker.html

 

[TLS Guy]

There is no burn in with speakers but many FR drivers do require mechanical break-in of the suspension. A Fostex FE126En never sounds very good out of the box but comes into it's own after a couple hundred hours.

To quote Siegfred Linkwitz, co-inventor of the Linkwitz-Riley filter: "It is difficult to screw up an open baffle speaker design to where it sounds worse than your typical box speaker".

Well, Linkwitz designs use complex electronic crossover and EQ. If you go to his site there is a mile of information about open backed speakers. They are very complex and there is no simple solution for them. Linkwitz also states that active EQ and crossover are mandatory in this approach.

In my view it is still a dumb idea. You can design properly loaded speakers to be non resonant. They have far improved power handling, bass response and dynamic range. In today's environment with very high dynamic range sources able to bring massive musical forces to light in the home, an open backed speaker will just never cut it. It is basically a very stupid concept and actually can be pretty much guaranteed to get the worst out of any driver.

 

[john11]

Hi. Thanks for the replies and giving me so much to think about.

Unfortunately i have blown all of my budget on the visatons so will have to experiment around with them hoping i can salvage something.

Thanks to everyone who participated

@ TLS Guy: Massive respect

@Poultrygeist: The Daddy

@The Warrior: Kudos Points

@Swerd:Big Up To The Max

 

[Poultrygeist]

Hang on to the B200's as they're one of the most popular and respected OB drivers around. This forum is obviously not a great resource for opinions or information on open baffles. Check out the massive OB forums at diyAudio and Audio Circle. Martin King's quarterwave site and his OB projects are another good resource.

If you've blown your budget you should at least try the B200's in the folding wing OB's ( Wild Burro Audio Labs ) for the cost of a $20 sheet of MDF. Very simple build with no crossovers and there's no simulation software needed for that design. For bass support a box sub is easy to integrate.

When I first ventured into open baffles and heard their intoxicating "live" sound I knew I could no longer justify owning the Zu's which I sold along with a pair of expensive Aerials. They'll spoil you on everything else as the coloration of conventional speakers becomes so obvious.

I can't comment on the break-in requirements of the B200 but with the Fostex and Lowther a common practice is to play FM static with each driver facing the other a few inches apart while covered with a heavy wool blanket.

 

[Swerd]

This thread involved people with apparently passionate likes about some rather uncommon speaker types (open baffle, also known as dipole speakers). When others (myself, TLS Guy and TheWarrior) with somewhat different tastes spoke up, there was no ugliness. I'm pleased .

There's always room for personal preference and reasonable disagreements, as long as the discussion remains civil. As it did here. Poultrygeist gets a pat on the head for his role in this. Please stick around here at AH. You won't be tarred & feathered for your preferences.

I'm sorry the original poster, john11, had to spend so much money on drivers that now disappoint him. And I hope this doesn't dampen his enthusiasm towards DIY speaker building.

 

[Poultrygeist]

If the OP lived on this side of the pond I'd be interested in buying those B200's as they hold much promise.

They're not easily sourced in the US and last time I checked were available through a dealer in Canada.

 

[Poultrygeist]

If I had those B200's I might try them in place of the Tang Band W8-1808's in this build. These tri-amped 3 ways use an active crossover and the tweets are planar B&G's. Not Lowthers but dang close.

 

[Poultrygeist]

For anyone who thinks that Lowthers are limited to horns should check these OB's from Lowther America. It's all about bass augmentation and usually with pro woofers. Tubes driving the Lowthers and SS for the woofers.

Nelson Pass designed a special OB electronic crossover which is now sold by Lowther America.

http://www.lowther-america.com/Cabinets/Open_Baffle_Speakers/

 

[TheWarrior]

This thread involved people with apparently passionate likes about some rather uncommon speaker types (open baffle, also known as dipole speakers). When others (myself, TLS Guy and TheWarrior) with somewhat different tastes spoke up, there was no ugliness. I'm pleased .

There's always room for personal preference and reasonable disagreements, as long as the discussion remains civil. As it did here. Poultrygeist gets a pat on the head for his role in this. Please stick around here at AH. You won't be tarred & feathered for your preferences.

I'm sorry the original poster, john11, had to spend so much money on drivers that now disappoint him. And I hope this doesn't dampen his enthusiasm towards DIY speaker building.

Lol... I love the interwebz!

Um, why is this project scrapped? You have some respectable drivers, try the other OB idea from Poultrygeist or put them in a box! Do you need help building one or something?

 

[TLS Guy]

If the OP lived on this side of the pond I'd be interested in buying those B200's as they hold much promise.

They're not easily sourced in the US and last time I checked were available through a dealer in Canada.

I can't see how those drivers show any promise. It is amazing what marketing hype can do coupled with delusion.

This is a very crude driver, that has a lot on common with the crude drivers in pre WW II radiograms.

It is a paper cones with a crude rolled paper surround.

As you would expect there is early cone break up at 600 Hz with the consequent poor response compounded by undamped edge reflections from the crude surround.

However this is the real piece de resistance.

As I understand it the mantra of the open baffle lobby, is to rid us of resonance.

Now that driver is a very high Q driver. The Total Q of that driver is 0.75! This you would expect, as the driver has a light cone and a free air resonance of 40 Hz. So the suspension has to be very floppy. So this driver by definition is a resonant driver! In any design the driver Qts sets the lowest parameter possible for system total Q. In an open backed box system Q will be driver Q.

Now for non resonant reproduction total system Q needs to be around 0.5. These sort of Qs are possible with enclosure design and with good bass output. My enclosures have a Q of 0.5 and reproduction is non resonant.

This driver on the other hand is incapable of non resonant reproduction in ANY application.

I can state categorically that any system designed round this driver is not capable of realistic reproduction, only highly colored reproduction. Some may like this. I don't.