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]

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.

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]

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.

 

[twest820]

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.

Greg, myself, and Zaph have all published such data. Shouldn't be hard to figure out what numbers to plug into Linkwitz' spreadsheets to get equivalent results. Might be easier to work from the measurements directly though.

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

It's not, but what controls the excursion limited region is the volume displacement corresponding to the acceptable distortion level. The specific ratio of Sd to xmax doesn't matter, so it also doesn't matter if the ratio's constant.

 

[otto88]

Good point.
So to be safe youd need to use a woofwer "under it" that could be crossed higher than intended and/ or use steeper XO slopes

 

[el`Ol]

I don't know midrange drivers that are really open in the back. You probably get better radiation patterns with flat car stuff back to back like this:
http://www.ciare.com/pdf/catalogo/US0720N04.PDF

 

[otto88]

Posts “crossing”:

When I said “Good point” - I was replying to CLS


“Greg, myself, and Zaph have all published such data.”
tw:
I have looked at Greg’s and Zaph’s links twice (don’t know where your data is), but can’t see data on the Neo10’s limits: can you be more specific?

 

[twest820]

Both Greg and Zaph state the SPLs they're testing at, though in Zaph's case it's over in his measurement page---90dB on infinite baffle. My data's less accurate on SPL, but it's here, for the time being. So you've got three sets of THD data at six or different SPLs to work from.

 

[studiotech]

Otto88, are you going active? Lower end sensitivity won't be as much of a problem then anyway with the Neo10.

Greg

 

[el`Ol]

The new Neo8 has higher SPL than the old one and can be crossed lower, forget dynamic drivers.
http://www.audaxspeaker.de/

 

[otto88]

Greg

Yes it will be active.
When I look carefully at the graph and the fine print on BG’s datasheet, its 86 dB at *0.5 m.
IIRC at 1 m that’s 83 dB.
However 83 dB + 75 watts, at a listening of say 3 m (10 feet) is only about 98 dB.

For the occasional “blast” on favourite albums/ when I have the house to myself, its distortion will be much higher.

I’m looking for a mid/ midwoofer that can cross at no more than 500 Hz, which if it has average power handling (c 80 watts), reaches its Xmax at closer to 110 db. That way when it hits say 108 dB, its distortion shouldn’t be so bad.

So what’s needed is sensitivity of a minimum of say 92 dB.

Any comments on an M-T-M with dynamic drivers?
eg Markaudio 4 inch Alpair 10's Gen. 2: a pair would be 93 Db
The current Gen 1: http://www.markaudio.com/alpair/10/fullrange gets lots of praise

Or a good 6.5”?