Extended and Efficient midrange: what do we have here?

[zmyrna]

On a slim OB, if single 8" starts rolling off at 400Hz, two 8" will start rolling of at 400Hz too. So what is the point?
If you want to cross lover, you either need a bigger baffle or active EQ.
MTM is hard to implement and expensive too.
If you pick a high eff mid, you can do with just one per channel.
In a closed box, single Supravox or PHL 6" should match fine with your tweeter.

[Telstar]

Originally Posted by zmyrna

On a slim OB, if single 8" starts rolling off at 400Hz, two 8" will start rolling of at 400Hz too.

Yes, but two drivers reinforce the emission in all their range, including <400hz, as they have a bit more baffle space, i suppose. I have more margin to play with mechanical filtering.
From my old sims, rolloff was around 350hz, so you are spot on with 400hz for a narrower baffle (25-30cm). But probably I wont go OB this time.

If you know higher efficiency mids, with a NON-rising FR please list them.
PHL maybe, but if i don't see at least the FR, I wont pick one, since they declare only 5-6khz as upper range, which translates in 3k max 1st order filter. PHL drivers do have one advantage, though: they exist in 16Ohm version.

In a closed box, single Supravox or PHL 6" should match fine with your tweeter.

Probably yes, thanks
I have to study about baffle step and whether one or two drivers are better (to my ears).

I'll wait a few weeks for more suggestions.

[wintermute]

when looking at the baffle step, plan for a 3-4db reduction in overall efficiency, so to reach your target of 95db efficiency you need 98-99db to start with for the drivers covering the baffle step region (ie your midbass drivers!) If you crossover at your baffle step frequency to your bass drivers you can then level match for the bass. To get a baffle step frequency of 200Hz you are going to need a wide baffle!

The other way to look at it is that all drivers must be 98-99db efficient and you do line level baffle step compensation. This though ups the ante for ALL of the drivers efficiency wise

Depending on the placement of the speakers you may need more or less baffle step compensation, but 3-4db is a good ballpark figure to plan on.

Tony.

[Jonasz]

B&W FST?

Should work fine down to about 300hz with a steep crossover.

[Telstar]

Originally Posted by wintermute

when looking at the baffle step, plan for a 3-4db reduction in overall efficiency, so to reach your target of 95db efficiency you need 98-99db to start with for the drivers covering the baffle step region (ie your midbass drivers!)

Thanks, Tony. This helped.
So I definitely need two 93dB midranges or a 98-99 one.
Therefore PHL 6" which are 98-100db gets back on frontline, but I need to find one driver from their production with satisfactory FR in my used range.
There is also the PHY-HP H21 LB 15 (added to the first post), which is 8" and most suited in OB (0.59 Qts), anyway I'm pretty sure is well over 300€ price, and for OB I fond the need for more cone are = two of them => out of budget.

If you crossover at your baffle step frequency to your bass drivers you can then level match for the bass. To get a baffle step frequency of 200Hz you are going to need a wide baffle!

Bass will be active at line-level, because it's absolutely impossible to find a <=12" with low Fs and high efficiency, the TL will be tuned at 25hz and I want an Fs of around 20hz. My favourite bass drivers atm are the scan-speak Discovery either 10" or 12".
If i wanted to go all passive, bass response would terminate at 35hz in the best case unless i use some 15" pro driver and still it wont go as low as the scanspeak (or a peerless).

I dont want to equalize but maybe a little has to be done either at the bottom or the top of the midrange freq window.
I can accept a 250hz XO, but not a 300hz this time.
If basta! simulates normal baffle step, IIRC about 40cm are required for 250hz.

[5th element]

I second the recommendation for the FST. High efficiency, controlled upper breakup and will work down to 250-300 Hz with a steep xover. It's distortion profile also suits being crossed over high, which is incidentally what B&W designed it for. You will need a notch at 3.5kHz for the one peak/fly in the ointment, but all wider bandwidth/high efficiency drivers are going to require some response shaping if crossed high.

Note that first order electrical crossovers do not often give first order acoustic slopes. Lots of Dynaudio loudspeakers use first order acoustic slopes but often have very complex crossovers in order to achieve them.

[454Casull]

10F/4424G00

Not extremely efficient, but smooth and extended.

[Telstar]

Originally Posted by Telstar

IIRC about 40cm are required for 250hz.

I correct myself, that would be 45cm, which is a little much for WAF, so probably I have to compensate.

I'll check the 2 drivers recommendations tomorrow.
Thanks

[Telstar]

Originally Posted by 454Casull

10F/4424G00

Not extremely efficient, but smooth and extended.

It's pretty good up to 4khz, but I cannot use 90db. I had checked all scan-speak catalogue as first thing since I'm mating their tweeter.

[Telstar]

Originally Posted by 5th element

I second the recommendation for the FST. High efficiency, controlled upper breakup and will work down to 250-300 Hz with a steep xover. It's distortion profile also suits being crossed over high, which is incidentally what B&W designed it for. You will need a notch at 3.5kHz for the one peak/fly in the ointment, but all wider bandwidth/high efficiency drivers are going to require some response shaping if crossed high.

These are already two things that I don't want to do. I hate those peaks in the voice range and a notch would be mandatory. Add that LF response is almost insufficient for even a 2nd order xo at 250hz.
Efficiency data I have to extrapolate from the graph attached above, but it should be at least 97db for making this driver viable for me. I checked cost and I can't buy 2 per speaker.

There are very few wideband that do not require equalization, such as Volt (too inefficient but otherwise perfect for the job) and the 7" EMS that I listed in the first post -it may beam but it's the only full range I know off that is naturally smooth. But it's lacking of spl in the low-end of my used range.

Note that first order electrical crossovers do not often give first order acoustic slopes. Lots of Dynaudio loudspeakers use first order acoustic slopes but often have very complex crossovers in order to achieve them.

Thanks for this advice. I will commission the XO realization to somebody much more expert than yours truly, once I finalized the drivers and rough shape of the speakers.