Tri-wire 2.5 way speakers?

[Sonusthree]

Hi everyone,

I've tried everything except a subwoofer to get more bass from my speakers without satisfactory results so far. Here's my next idea and I really need some advice before I break something or maybe just waste some money!!

The speakers in question are Tannoy 611 dual concentric. They are a 2.5 way design with 8" mid/bass and a supplementary 8".

Both 8" drivers are working together below 250Hz.
The enclosure is sealed.

Could I add an extra set of binding posts to the bass driver and power with an appropriate amp?

I would hope to use this method to increase the power going to the bass driver and equalise the sound to my taste. I would also gain the desirable option of going active for this section and bypassing the inductor!

I can see (I think?) that each amplifier would have an easier load under these conditions but I'm confused slightly that:

1, One cone moving 'further' (louder) than the other would effectively 'suck' the other cone that is also working at the same frequencies.
2, Phase issues could be a problem?
3, Unequal excursion would mean that the extra bass would not reach so low. My theory being that the lowest frequencies come from both 8"drivers working together as one larger driver perhaps equivalent to one 10"??

Does anybody have any advice for me? I'd rather not try this blindly!!

Any help would be VERY much appreciated,
Martin.

[Random Task]

both woofers also work in the same enclosure ?

[Sonusthree]

Hi RT,
Yes, everything is in one sealed enclosure.

[Random Task]

If it so,
I think, with an extra amplifier and active crossover network, it will work. But without measure equipment it´ll be difficult to reach the cut-off frequency of the sub-woofer in the system..
On one hand,without the passive network (coil),the woofer will not reach the lowest frequency as before,because the enclosure is calculated with the RDC of the coil.
On the other Hand,probably all of the active crossovers have a bass-gaining to use as you desire...

[Sonusthree]

Thanks for the reply.
I will keep the passive network at first and then build my own DIY active filter later (for the bass driver only). I can tweak this forever until it is right.

My main question is about the use of two cones operated at different levels within a sealed enclosure.
Both driver's frequency range will overlap.

What would happen?
Any disadvantages?

[Sonusthree]

I guess that I'll just have to try it and see what happens.

Wish me luck!!!

[5th element]

I guess it could have some impact, but the effect would be rather small. Remember if one driver wasn't connected at all, it would only be influenced in the same way a passive radiator is. Meaning it would only be excited at the tuning frequency, not across the board.

A 2.5 way loudspeaker, by its nature, compensates fully for bafflestep, providing both mid/bass drivers are identical. Increasing the level of the lower driver will most likely upset this balance and could add a thickness to the sound thats unwanted.

IMO you are not experiencing lack of bass or 'thinness' of sound due to lack of bafflestep compensation, more the speakers are not reaching low enough for your liking.

Four 8" drivers is a reasonable amount of air shifting and certainly should be capable of reaching appreciable SPLs, you do not mention that the speakers dont go loud enough, simply that there is not enough bass.

There is also one possibility, the amplifier you are using doesnt like the load so much and the bass sounds thin because of it. Adding in the second amp, even played at exactly the same level could sort things out.

One last thing is room placement, is it possible you are sitting in a room mode notch? If at an important frequency it could rob the sound of impact.

Finally, could it be a psychoacoustic effect rather then a true lack of bass. IOW are the speakers a little bright and foward sounding, giving the impression there is a lack of bass.

Edit - One way to test out a number of these various issues could simply be done using parametric EQ. You could plug the computer into the hifi and apply subtle amounts of eq shaping. Be it boosting the bass or applying a tilt that slowly reduces the level by 3-4 dB from say 500-20000hz. This could be a tonal balance issue or a true lack of bass.

[Random Task]

Oh..my fault..
my last answer is in expection of independent enclosures of the woofers..
By using the same Enclosure, it´s exactly what 5th element say..sorry

[Random Task]

Tannoy Speakers are well known for their higher SPL(effency)..not for bass..maybe an extra Sub with deep cutoff frequency can manage it?

[herm]

Sonusthree,

Just one guys opinion here:

Your solution will boost all bass below 250 hertz.

This will work if your problem exists with all frequencies below 250.

My guess is that your problem would be better solved with a good
EQ and some kind of measurement device.

You might find you are OK except for some large room/placement
nulls, which will NOT be fixed by raising everything below 250.

Can you beg/borrow someones SPL meter? A good measurement
saves a LOT of blind attempts at fixing....

herm