What are the pros and cons of this speaker design?

[crenca]

Elac and Andrew Jones new $2.5k speaker (not released yet) looks interesting.  What is everyone's opinion about Jones' bass driver design - basically, a passive cone being driven by a ported active speaker directly behind it which is enclosed by the cabinet:

 

https://parttimeaudiophile.com/2017/05/07/axpona-2017-elac-conjures-big-sound/#jp-carousel-58073

 

 

[semente]

A resonator?

A crutch, an artifice...

[monteverdi]

The passive cone will not transmit efficiently the higher frequencies produced by the woofer (including ports) behind and will therefore act as a filter. But the compliance of the (small) air volume and surround will slow down that front driver and will cause some time delay

[crenca]

1 minute ago, monteverdi said:

The passive cone will not transmit efficiently the higher frequencies produced by the woofer (including ports) behind and will therefore act as a filter. But the compliance of the (small) air volume and surround will slow down that front driver and will cause some time delay

 

 

hhmmm.  I wonder if that air volume you speak of would not be more like what occurs with headphones and the ear canal in that there is not enough air to have the wave propagation effect so it acts more like a coupler (i.e. piston) and thus the time delay is trivialized??

[monteverdi]

30 minutes ago, crenca said:

 

 

hhmmm.  I wonder if that air volume you speak of would not be more like what occurs with headphones and the ear canal in that there is not enough air to have the wave propagation effect so it acts more like a coupler (i.e. piston) and thus the time delay is trivialized??

Similar but much higher volume than an ear canal. So how direct that coupling is will depend on volume and leakage. Isobaric designs with 2 stacked active woofer are existing for quite some time. So it is somewhat a hybrid idea between that and passive radiators.

[semente]

7 minutes ago, monteverdi said:

Similar but much higher volume than an ear canal. So how direct that coupling is will depend on volume and leakage. Isobaric designs with 2 stacked active woofer are existing for quite some time. So it is somewhat a hybrid idea between that and passive radiators.

 

I have no experience with passive radiators; is there any reason why it would produce better transient response than a port, the suspension perhaps? 

[monteverdi]

The main advantage of passive radiators is that they have less high frequency leakage than open ports and also no wind noise like too narrow ports have. They can be tuned by varying the membrane weight like varying the length of open ports. Transient response is really depending on the main driver and box volume optimization both with ports or passive radiators. In the last few years I see much more commercial loudspeakers with passive radiators as it is easier to design smaller box volume as no port volume has to be added to the box (which can be quite large with large port diameter and if tuned low also long length).

[Don Hills]

It's a series tuned 6th order bandpass. Not a new idea, but interesting in its use of a passive radiator instead of a port. 

[semente]

9 hours ago, monteverdi said:

The main advantage of passive radiators is that they have less high frequency leakage than open ports and also no wind noise like too narrow ports have. They can be tuned by varying the membrane weight like varying the length of open ports. Transient response is really depending on the main driver and box volume optimization both with ports or passive radiators. In the last few years I see much more commercial loudspeakers with passive radiators as it is easier to design smaller box volume as no port volume has to be added to the box (which can be quite large with large port diameter and if tuned low also long length).

 

By the sound of it I don't think that transient response will be up to sealed-box level.

And it's still a crutch, an artifice to extract more low frequency amplitude and extension from ever smaller boxes...

It's probably also cheaper overall than getting a proper "active" driver to do the job and reducing the size of the cabinet brings the cost down too.

 

R

[Rt66indierock]

9 hours ago, semente said:

 

By the sound of it I don't think that transient response will be up to sealed-box level.

And it's still a crutch, an artifice to extract more low frequency amplitude and extension from ever smaller boxes...

It's probably also cheaper overall than getting a proper "active" driver to do the job and reducing the size of the cabinet brings the cost down too.

 

R

 

I got a half hour one on one with Andrew Jones at RMAF 2016. Part of the discussion was about sealed boxes and how to get closer with to them with other designs. I will be interested in listening to these speakers.

[NOMBEDES]

First:   Andrew Jones.  I think he is one of the best designers around.  I would go with him 92% of the time.  Good sound, good price.

 

Second: Don't a lot of expensive subwoofers have passive radiators?   

[crenca]

4 minutes ago, NOMBEDES said:

First:   Andrew Jones.  I think he is one of the best designers around.  I would go with him 92% of the time.  Good sound, good price.

 

Second: Don't a lot of expensive subwoofers have passive radiators?   

 

Well, look at that design again - this is not the everyday passive radiator common in subs and full range speakers.

 

It is rather a completely enclosed and ported LF cone that is then acoustically coupled (via a small air space - much like a headphone driver is to your ear canal) to a larger "passive" radiator...

[NOMBEDES]

13 minutes ago, crenca said:

 

Well, look at that design again - this is not the everyday passive radiator common in subs and full range speakers.

 

It is rather a completely enclosed and ported LF cone that is then acoustically coupled (via a small air space - much like a headphone driver is to your ear canal) to a larger "passive" radiator...

 

@crenca Got it.  Still, interesting.  Proof is in the sound I guess.

[esldude]

It is not a new idea.  It is a bandpass variation.  In a classic bandpass you have a sealed woofer, and the cone drives a ported box.  So the ports and box size act as filters that aren't electronic to control both high and low frequency response.  Solves just the problem he is saying it solves which is to simplify the electronic crossover and not have any higher frequency noises coming from ports.  Within reason passive radiators can be substituted for ports and function about the same yet not have air flow to cause noise at higher frequencies.

 

More interesting was something Sonus Faber has done at times.  Use an inexpensive woofer as a passive radiator by leaving it disconnected from the wiring.  Yet put a resistor across the leads of the magnet so it could tune the Q of the woofer system.  That was neat, useful and simple.