95 dB - by mixed driver D'Appolito

[rick57]

I have some good spare 6.5 inch midbass drivers: PHL 1280 (6.1 ohms, 91 dB) , Focal 6W4311 (6.6, 91 dB) and the Usher 8945A 7" (5.8, 88 dB).

I want a system with about 95 db efficiency. I have tweeters about that (Esg), and will do an active sub.

I could sell the 6.5 inches and buy something 95 db, but there’s not many options:
- maybe second hand (no longer made) Focal (6WM?) that’s 95 db, but I’ve heard it and it has a pretty unpleasant “shouty” quality;
- the 10” Ciare PM250 - the sub would have to cross at 200 Hz, and it will beam above 1 kHz -not suitable in this room; ditto JBL 10" 2123.
- Eminence Beta 8 (94 dB) – as detailed & clean as any of the above??

So tonight I thought – a D'Appolito using eg the PHL 1280s and the Ushers. I am not mad on D'Appolitos because of the vertical lobbing, but could live with that.

The downside of paralleling is the amp will have to be able to handle about 3 ohms.

The advantage I see of mixing drivers is that the peaks & troughs in the FR in each driver type will be reduced (to half?).

What do you think?

Thanks

[SY]

Get the drivers spaced tightly, use a 4th order crossover, and keep the crossover frequency as low as your tweeters will allow and you won't have much lobing problem, just the characteristic narrowed vertical dispersion.

This will not fix driver problems, you'll need to attack them more directly.

[rick57]

SY,

Thanks for the very fast and helpful tips!
So there’s no downside on mixing mid drivers . . good!

Tweeter options are at 1.5 k (if I get some of the modest $ Seas tweeters whose Fs is 500-600); or with ESgs at either 2.2 or 2.7 k.

Would those different Hz make much difference? (Is there a particular link on this?)

All the 1.5 k tweeters will be no more than 90 dB, while the ESgs are 95- 96 dB . .

Cheers

[SY]

Ah, I misunderstood, I thought you were using two of the same driver. Never mind. You do not want to do an MTM. What you CAN do is stack the two, use the lower driver to do the baffle compensation while the other runs flat out. But mixing drivers in the sensitive part of the midrange will most likely make a sonic mess.

[gary f]

I would not mix drivers. Crossover design will be very difficult if you put drivers in parallel.

F

[rick57]

(I should have said that the three drivers mentioned are each in pairs, eg 2 * PHL etc, but you probably realized that).

Thinking further, mixing drivers would seem to be a plus if eg the Usher has a rise around 900 Hz (which they do), and the Focal had a mirror image dip at that point (no idea). So it looks to me like FRs are needed to make a decision.

> Crossover design will be very difficult
If I stick with mixing drivers, I might nudge this project further down the experience list . .

SY what sort of sonic mess were you envisioning?

Thanks

[SY]

Well, if you have an MTM that's really M₁TM₂, you'll have a polar pattern that changes with frequency in a nonsymmetrical way. You will not sum properly at the centerline.

[rick57]

Ah, sounded a bit tooo convenient to be good . .
Thanks again SY

[Ap]

As someone alluded, make a 2.5way.
That way you can use different drivers, although they will probably reuire different bass loadings (separate cabinets).
Even an MTM with 90db drivers is going to only be 90db due to baffle step losses. At the ned of the day it might be easier to sell a pair & buy another matching pair to whatever you keep.

[Cal Weldon]

If you can avoid using two different drivers to cover the same frequency you will be happier. A 2.5 way should be the same drivers. If they are not you really just have a three way with serious overlap. Not sure how you'd ever get that to sound good.