Check out these speakers with a very interesting design

[gus6464]

They are Neat Acoustic speakers which is a british brand. Their Momentum line is not their top of the line but their design is very interesting. They have drivers inside the cabinets which are not visible.

Momentum 4i floorstander http://www.neat.co.uk/p_pages/momentumtwo.php

Momentum 3i bookshelf http://www.neat.co.uk/p_pages/momentumone.php

I emailed their US distributor to see if they have any dealers where I live to see if I can listen to them.

 

[Sheep]

A ported Isobaric system. usually these are sealed.. I wonder how they sound.

No specs on the website it seems..

SheepStar

 

[3db]

I'm very curious to hear how that sounds. I wonder too how much cabinet resonance is inherent in a design like this.

 

[TheDog]

I've seen isobaric speakers like this in car-audio applications, not in home audio though. I'd also be interested in hearing how they sound. Let us know if you get the chance to listen to them.

 

[TLS Guy]

same design

I did exactly the same thing 20 years ago.

These speakers are the same, except the bass mids are in individual sealed chambers. The speakers can be run passive or biamped. They are really only any good biamped. They are now doing sterling service in our Grand Forks ND condo. Bass mids are the extended range dual magnet version of the 17 W-75. the tweeter is Scanspeak and the concealed isobaric drivers are 10 inch Morels.

http://mdcarter.smugmug.com/gallery/2465549#129314808

These speakers are good performers. The bass mids have acoustic roll off. There is an active low pass crossover to the isobarik drivers.

With speakers there is seldom anything new under the sun.

 

[3db]

I did exactly the same thing 20 years ago.

These speakers are the same, except the bass mids are in individual sealed chambers. The speakers can be run passive or biamped. They are really only any good biamped. They are now doing sterling service in our Grand Forks ND condo. Bass mids are the extended range dual magnet version of the 17 W-75. the tweeter is Scanspeak and the concealed isobaric drivers are 10 inch Morels.

http://mdcarter.smugmug.com/gallery/2465549#129314808

These speakers are good performers. The bass mids have acoustic roll off. There is an active low pass crossover to the isobarik drivers.

With speakers there is seldom anything new under the sun.

I would think that a design like that would incite cabinet resonance more so than the more conventional designs. What advantages would this design have over a sealed or convential ported system?

 

[TLS Guy]

I would think that a design like that would incite cabinet resonance more so than the more conventional designs. What advantages would this design have over a sealed or convential ported system?

Cabinet resonance is not a big issue in my speaker, as there are four separate cavities in the speaker, which gets you off to a good start.

At the time there was a lot of buzz about this form of loading, and a lot of interest in Isobarik loading. There were a lot of articles in speaker builder at the time. Linn acoustics have a patent on Isobarik loading, so you have to pay them a fee to do it commercially. Ivor Tiefenbrun the inventor was widely extolling the advantages back then.

Now the advantage of the coupled cavity is to get a low F3 in a pretty small space. Both these enclosures are what is called a second order coupled cavity bass system. Even though this alignment is ported it rolls off at 12 db at both ends of the band pass. Now the isobarik addition halves the volume.

Now the F3 of my speakers is 27 Hz second order roll off on the bottom end and 90 Hz on the top end. Think of coupled cavity bass systems as band pass devices. Now the bass mids have acoustic roll off at 90 Hz second order, so you have an acoustic second order roll off.

The low pass crossover just cuts of the bass drovers above acoustic roll off to prevent HF getting radiated from the port.

OK, no free lunch is there? The idea was to prevent the huge time problems of low frequency crossovers, the problem is coupled cavity designs have significant phase and time delay problems of their own. THD is also higher than for conventional loading. In my view the second order coupled cavity designs are the only ones close to acceptable for Hi Fi use. The second and fourth order alignments, a la Bose, I find unacceptable.

Now the next problem is the isobarilk loading takes a lot of amp power. You are getting the same performance as one driver but powering two. The enclosure volume is halved because VAS is halved. Bottom line to make my design perform properly you need a pretty beefy high current amp to drive the bass system at higher listening levels.

So it was an interesting experiment, and I did use the speakers for monitoring in some live recording sessions, but I haven't been tempted to do this design again.

 

[3db]

In my view the second order coupled cavity designs are the only ones close to acceptable for Hi Fi use. The second and fourth order alignments, a la Bose, I find unacceptable..

alignments and coupled are two different things here?

Now the next problem is the isobarilk loading takes a lot of amp power. You are getting the same performance as one driver but powering two. The enclosure volume is halved because VAS is halved. Bottom line to make my design perform properly you need a pretty beefy high current amp to drive the bass system at higher listening levels.

So it was an interesting experiment, and I did use the speakers for monitoring in some live recording sessions, but I haven't been tempted to do this design again.

I don't see the high current amp as a problem as there are many low sensitivity 4 ohm speakers that are conventional in design that require a beefy amp.

Thanks for the response.

 

[TLS Guy]

alignments and coupled are two different things here?



I don't see the high current amp as a problem as there are many low sensitivity 4 ohm speakers that are conventional in design that require a beefy amp.

Thanks for the response.

What I wanted to say was that among coupled cavity designs the second order alignment is the only one I would consider, not third and fourth order coupled cavity alignments.

I agree that now we have cheap plate amps the drive of the isobarik bass system is not the problem it was. However I would be suspicious you could get superlative results from this approach without biamping. For one thing sensitivity and efficiency are low. You only have port output no output radiated from even one cone. If you use a passive crossover on the lower units, you still have to use a very low crossover point, and that is very unsatisfactory. Also you you can't trim the bass unit output, which is very important in this type of system when changing acoustic environments.

I just felt after doing it, that it was interesting as the bass output and reach take you by surprise in a speaker that size. Our now retired dermatologist, who is a great audio buff, just loved those speakers. So there is a speaker for everyone one. I just felt the exercise was a lot of bother for the results.
When all said and done there is good bass reach, but the bass articulation is not spectacular. As you probably know I do like my speakers to reproduce the King of Instruments realistically. The bass articulation of TLS speakers is just unmatched. That is what I have returned to again and again and is by far and away my preferred form of bass loading. The bass pipes speak more clearly and firmly, with natural articulation from a good TLS that other alignments just can not match. Unfortunately very few have heard good TLS systems. There are designs out there that claim to be, but I dispute that. They are variants of reflex loading in my view. There is the odd bad design out there. Since John Wright of TDL left us there have been no good commercial designs, and its been left to the DIYs like myself to develop the breed.

I should mention the THOR kit. It is a kit, and is not available complete, But I have three very happy customers from those.

May be its time for an Audioholics TLS? I'm thinking about it.

 

[jcPanny]

New AV123 subs

FYI,
A couple of the AV123 subs under development will use a similar driver coupled to a passive radiator design including an entry level "X-plosive" and a high end "BMF-1" sub.

 

[TLS Guy]

FYI,
A couple of the AV123 subs under development will use a similar driver coupled to a passive radiator design including an entry level "X-plosive" and a high end "BMF-1" sub.

That's interesting. I would love to have been able to make mine a passive radiator design. The passive radiator speaker presents a lot of difficulties for the DIY builder. A manufacturer can produce a passive radiator with the exact spec. he needs for the woofer and box. This gives the well funded manufacturer a huge advantage when a passive radiator would be the best solution.

With amp power now cheap and readily available isobarik subs make powerful modestly sized subs a reality. I have tried to model low F3 isobarik subs, but you get into insurmountable port problems. A passive radiator would get over that.