Sensitivity of Drivers.

[RMutt]

Some more help needed please. In a three way speaker design, is it normal practice to use drivers that all have the same sensitivity? I am looking to extend the bass response of my speakers. I am considering adding a bass driver with a higher sensitivity, as the bass seems a little quiet in my speakers at the moment. Treble and mid are 91, I have found a bass of 93. Would this overwhelm the upper frequencies? Is this feasible? On a related note, are sealed box design speakers always compromised in the bass response or are there any good examples of speakers that give a an extended low bass?

[Ali Tait]

It could be added, though you'd need to pad down the sensitivity to match the other drivers. There is a lot more to it than this though IMHO, you need info on the frequency response of the driver in question, as well as it's other characteristics.

I'd say it would be much easier to add a dedicated adjustable sub or two to your existing speakers, as these can be easily tuned to match them.

[RMutt]

Yeah, I know I am trying to simplify what is a complex set of parameters. I have tried a sub, albeit not an expensive one, and was not happy with the result. I can get the drivers for less than a hundred pounds, decent subs would be much more. I suppose what I need to know is if it is a complete non starter. When you say pad, would that adjust volume or frequency? Do you think a good quality volume control could work?

[Macca]

A resistor in series with the driver is the usual way of reducing sensitivity. Difficult to get right if you are working blind. I'm guessing the exisitng speakers are DIY jobs?

[walpurgis]

Some more help needed please. In a three way speaker design, is it normal practice to use drivers that all have the same sensitivity? I am looking to extend the bass response of my speakers. I am considering adding a bass driver with a higher sensitivity, as the bass seems a little quiet in my speakers at the moment. Treble and mid are 91, I have found a bass of 93. Would this overwhelm the upper frequencies? Is this feasible? On a related note, are sealed box design speakers always compromised in the bass response or are there any good examples of speakers that give a an extended low bass?

There have been sealed box speakers with extended bass response. A famous one was the Acoustic Research AR3a, which would produce accurate bass notes down to below 30Hz. Less well known and also American the original Advent Speaker, quite similar in concept. Of course there's the first Bose 901 which was compact, but kicked out monstrous bass down to about 25Hz, but that was 'cheating', they used massive electronic equalisation to achieve it. The old 'isobaric' type Linn speakers have a potent bass performance too.

[Ali Tait]

Yeah, I know I am trying to simplify what is a complex set of parameters. I have tried a sub, albeit not an expensive one, and was not happy with the result. I can get the drivers for less than a hundred pounds, decent subs would be much more. I suppose what I need to know is if it is a complete non starter. When you say pad, would that adjust volume or frequency? Do you think a good quality volume control could work?

Check this out-

http://www.madisoundspeakerstore.com/l-pads-attenuators/fostex-r82b-200w-l-pad/

[RMutt]

Thanks for that Geoff. Yes Martin, it's my Goodmans K2 project, you've seen it before but may have forgotten it. How do you work out the value of the resistor?

[Ali Tait]

This would basically adjust volume to match the other drivers. You would still need to design a crossover, taking into account the frequency response of the new driver to see where in frequency to marry it to your existing drivers.

[RMutt]

Thanks Ali. I presume that could be used to the bass?

[RMutt]

Update. I made a mistake with the tweeter and mid. Both are 92db. Would a 93db bass be close enough? I don't suppose anyone knows what the sensitivity of the original Goodmans K2 bass is do they? Thanks.

[Macca]

Update. I made a mistake with the tweeter and mid. Both are 92db. Would a 93db bass be close enough? I don't suppose anyone knows what the sensitivity of the original Goodmans K2 bass is do they? Thanks.

I recall your Goodmans now. :) When I have built speakers in the past I have not worried overly about differing driver sensitivities. There are so many other parameters having an effect that it is difficult to quantify anything before you actually get the drivers in the box and start playing music. I would just stick them in there as is and see what it sounds like. It is the only way to be sure.

[walpurgis]

Sensitivity variations become more perceptible as frequency rises because of the way our hearing works, but as long as drivers are within an average of 2 to 3 db of each other in sensitivity you would really struggle to hear any difference between them.

[Ali Tait]

Thanks Ali. I presume that could be used to the bass?

Yes I'd have thought so.

[Ali Tait]

Update. I made a mistake with the tweeter and mid. Both are 92db. Would a 93db bass be close enough? I don't suppose anyone knows what the sensitivity of the original Goodmans K2 bass is do they? Thanks.

Yes I'm sure it would, though published specs are often different from the reality. If they are correct, they should be well matched.