SpeakerTalk

clubsport911 · Posted: Wed Mar 27, 2013 9:25 am Post subject:

Surely the main costs were time in researching the optimum design ? There is perhaps some increased complexity in component count for the crossovers, but computers solve the former and the real costs of a few more caps and inductors for these kinds of speakers is negligable.

No, I'm not buying the cost or complexity reason for 2013.

I think you have nailed it well. It needs equalisation to make it perform and this does add. Few modern speakers except active studio monitors contain in built correction (and of course, subwoofers).

Interested that a lot of car subs are cavity coupled bandpass designs.

There is another reason ?

SaSi · Senior Contributor 200+ Joined: 24 Aug 2008 Posts: 256

The 4th order bandbass enclosure is a design that trades frequency response for efficiency. It gives much higher output for a limited frequency range. Provided it's coupled with a capable mid/bass to cater for frequencies above 60-80Hz it's a decent tradeoff.

In some older threads it was described how difficult it was to model and then finetune (by testing and modification) the bandpass tuning.

For several years (perhaps decades) KEF was constantly producing at least one such design. There are several different products employing this principle (104/2, 105/3, 107, 107/2, etc).

I am guessing that the difficulty in finetuning the design would have implications on how these systems aged. Surround and spider drift in characteristics over years could alter the tuning and perhaps make these systems age less gracefully than other designs.

Additionally, KEF switched priorities and looks like they now focus on concentric drivers that reduce lobbing between mid range and tweeter.

speakerguru · Posted: Thu Mar 28, 2013 9:58 am Post subject:

SimplySound · Posted: Thu Mar 28, 2013 3:19 pm Post subject:

SaSi · Senior Contributor 200+ Joined: 24 Aug 2008 Posts: 256

It's very interesting to see that the ported design is more sensitive to aging than 4th order bandpass.

I mean, I know that a ported speaker design is hard to tune - at least compared to a sealed box - but I didn't realize it's also sensitive to aging.

One thing that makes me wonder is refoaming (in a broader sense to cover rubber surrounds as well). Perhaps the spider is much stiffer than the surrounds but I'm guessing that changing the original surround to an unknown - generic - version should alter the characteristics of the driver, hence possibly bring the system out of tune.

But going back to the original comment; a ported system is a 3rd order system and a bandpass system is a 4th order system. Isn't it logical to assume that the higher order system is easier to bring out of tune?

speakerguru · Posted: Mon Apr 15, 2013 10:35 pm Post subject:

The alignment of a woofer system is dominated by the moving masses of driver and ports (if present) and the compliance of the box volumes. These are normally very stable with time.

If the system has been designed sensibly the compliance of the driver and passive radiators (if present) which do age will be swamped by the box cavity compliances which do not.