A midrange to keep dipole-radiation to as high a frequency as possible

[otto88]

A good mid driver option:

Mitteltöner, midrange, Konusmitteltöner, Konus-Mitteltöner, Isophon mts 120 ALU, Mike Koch Audio

under: Download Katalog-Datenblatt Isophon, on page 3:
the Isophon PSM120

The narrow 120 mm frame would be good for extending the upper limit for a "baffle-less" open baffle.
Also sensitivity good: claimed 92 dB, and power handling high

I'm waiting to hear from koch audio what its Sd and Xmax is; but would guess its excursion limited low end in an open baffle, to have plenty of headroom, would be about 400 Hz

[6.283]

Hi Otto88,

I have not measured such small drivers myself, yet. But I could imagine that the rear ratiation suffers from the relative large magnet structure. That results in early roll off at the back and limits the usable FR for dipole operation.

Oliver

[StigErik]

The front/rear response difference can be solved by using two midranges in push-pull arrangement.

[454Casull]

Originally Posted by StigErik

The front/rear response difference can be solved by using two midranges in push-pull arrangement.

How does that help with maximizing dipole range? Using two drivers even slightly increases the distance between the front and back origins, no?

[studiotech]

BG Neo10. Best choice out the IMHO. Perfectly symmetrical radiation front and rear. Low distortion as long as you stay above 300-400Hz.

BG, Neo10 - n10 by: BG Radia - Meniscus Audio Group, Inc.| Speaker

see my measurements here:

HTGuide Forum - more Neo10 measurements

and zaphs here:

Zaph|Audio

Greg

[twest820]

Agree on the Neo10. The Neo8-S is worth a look as well and I seem to recall it being somewhat cheaper than the Isophon AL 120.

Originally Posted by 6.283

I could imagine that the rear ratiation suffers from the relative large magnet structure.

Below the dipole peak the back wave can be powered from the front of the driver with pretty good directivity. There's some room for maneuver there---with typical tweeter crosses near 2kHz one can probably get away with a 15cm OD without much rear wave asymmetry---but generally what one ends up looking for in a dipole mid is maximum Sd with minimum OD and good xmax.

[otto88]

The Neo10 is certainly excellent on the criteria of dipole-radiation.
Though sensitivity: I was a little disappointed to see the slope of the FR. Even if crossed at 500 Hz, its sensitivity is only 86 dB. I guess with power handling of 75 – 100 watts that’s ok.

Nice low distortion too - Glad I posted!

Fyi I’d also been considering an M-T-M with Markaudio Alpair 10's Generation 2. A 4” full ranger which i’d just use c 500 - 1800 Hz. Madisound is supposed to release them in about a month, with 4 at a “crazy price”

Greg,
I saw from your thread at htguide that you’ll be using the Neo10 with Lambda 15s. That’s my plan too (I have a pair of 15TDMs).
What Hz do you think you’ll cross at?

[twest820]

Originally Posted by otto88

I was a little disappointed to see the slope of the FR.

How so? The datasheet gives the nude dipole response without EQ so it'd be weird if it were flat.

[otto88]

Thanks, I didn’t see that they were measured that way.

It'd be handy if there were Sd and Xmax specs for the Neo drivers, in particular the Neo10.
We could put them into Linkwitz' spl_max1 spreadsheet, and get a sense of at what dB and Hz they begin to excurse near their limits, and get into higher distortion.

[CLS]

It may not be properly calculated. I think it's not 'piston' motion.