11 replies to this topic

[Scrambled_legs]

cant be that bad, just ken uses them so does the guy that runs auto audio.

why have some people said they are not very good. ?

[dave64]

Everyone's taste is different,

[Scrambled_legs]

correct. but are the morel cdm 88 shit [ on paper ] ?

[mr sideways]

they are very good, and are what i will choose when i go 3 way.

But they are a soft dome so act like a large tweeter, so they wont go really low like a normal 4" cone,but they are excellent at the mid and highs.
If you have decent 6.5" mid bass's then that wont matter.

[mulletboy2]

mr sideways, on 22 Feb 2012 - 16:45, said:

so they wont go really low like a normal 4" cone,but they are excellent at the mid and highs.
If you have decent 6.5" mid bass's then that wont matter.

That's not true. Crossover point is very important.. it should be kept out of the midrange ideally.. and that's where you have to put it when using a soft dome mid like this.. so yes, your midbass can play high enough, but your ear is still very sensitive to the frequencies where you have to place the crossover.

Also they have directionality/dispersion characteristics that can be problematic.. again, a characteristic of the speaker design. Doesn't make them bad.. just different, and IM(O/E) harder to get to sound good.

[Scrambled_legs]

i think im going to have to try a few different pairs, and thats not going to make me very happy

mullet, i know just what you are saying about x/over points , rings very true.

[WeirdNeville]

They at least have closed backs, which makes fitting them a touch easier. Most, well, many 3 and 4" mids need enclousures of some description, and that means holes in dash, fiberglass.... more mess...

[Just Ken]

They are an outstanding mid-range mate....

Soft dome with wide disbersal rather than concave cone which requires far more effort when fitting as they are more prone to become directional / audable. Very shallow & easy to mount & they are vented to breath from behind but can be used in sealed pods if required......

ken.

[mulletboy2]

Just Ken, on 23 Feb 2012 - 00:38, said:

Soft dome with wide disbersal

That's a common myth mate. Dome mids may look like they should have wide dispersion patterns compared to concave cones, but it actually works just the opposite. Dome speakers have narrow dispersion patterns and cone speakers wider. That's why domes can work so well in a dash, aimed at the windscreen - you're not getting a direct wave, then an indirect wave moments later - you just get the indirect.

So, in the interest of science:

Quote

The soft domes spawned an entirely erroneous, widespread belief that they had significantly better sound dispersion than cones. As previously mentioned in Section 20.8.4, their hemispherical shape suggested to many people that the sound radiated as in Figure 20.12(a), but in fact, as they move in one plane only, their action is pistonic, as shown in Figure 20.12(. However, once they enter break-up, the centre of the dome uncouples from the high frequencies, contrary to the behaviour of a cone loudspeaker, because the dome is driven from its edges. The rather undesirable result of this is that the dome becomes a ring radiator, which lends to response beaming at high frequencies, because an annular radiator behaves like separate displaced radiators with a space between them, the centre of the ring being the null point.

NB: 20.12(a) shows exactly how you picture a speaker radiating sound. 20.12( shows a pic of a dome, with the sound radiating from all points around the edge, with waves from each point along the edge interfering with eachother, and also a significantly narrower overall dispersion characteristic. See: Recording Studio Design by Philip Newell, p532.

Also:

Quote

Cones have always been a popular choice for mid-range drivers, and they have the rather fortunate tendency to break up in such a way that the higher frequencies are often decoupled from the outer edges of the cone, and thus tend to radiate from the smaller diameter central section. They can thus maintain their wide directivity as the frequency rises.

Why are domes so popular in studios then?

Quote

Generally, the restriction of the use of cone drivers in high-level studio monitor mid-range use is because of the limit to the amount of heat that can be dissipated by the relatively small coils that tend to be used. Theoretically, however, there would
seem to be no reason why small cones cannot be driven by larger than normal diameter voice coils

So, as I keep saying, each type of driver has its pros and cons.. to believe any one to superior across the board is to miss the point.

Edited by mulletboy2, 23 Feb 2012 - 08:20.

[gordon@genesis]

The Domes I have used tend to have a nice warmth to them, which is likely a side effect of not having the cone break up issues that some cone drivers exhibit. The softness of the dome means that when the centre decouples the top frequencies roll off gently whereas cone drivers often have resonances that are usually heard as harshness.

If cone drivers are designed to eliminate the cone resonances, they can give a similar warmth. The Scan Speak drivers with the slit cones are in this category and have a similar sound character with a much wider frequency response.

That said there now are some excellent cone drivers when suitable materials and motor engineering are used together. The little Focal 3" with the grey cone is a very good mid and there are plenty of other examples. I picked this one as I've heard it sound superb in a system. There are lots of others such as the HAT that I've heard good things about but not personally listened to.

The big advantage with dome mids is ease of mounting due to the shallow construction. The CDM88 isn't sealed at the back, but can run quite happily just on a baffle so A pillar mounting becomes easy. They don't play midbass so you will need to get the midbass driver angled so the image doesn't drop on lower vocal notes.

While they don't need an enclosure, power handling is better when mounted in a small sealed enclosure, around 1/4 litre. Look to cross over around 600-700 at the lower end and play no higher than 4k at the top end as they become quite beamy at higher frequencies. Having said that they are easier to mount on axis so it isn't such an issue...

A chambered dome tweeter will be a good match to a CDM88 and will allow you to cross lower minimising the beaming issue.

Edited by gordon@genesis, 23 Feb 2012 - 09:10.

[Scrambled_legs]

if they play well on axis, i may well consider a pair with the d2004.

only thing that troubles me is my midbass playing off axis in the doors...

[davidcox1983]

Horses for courses, sometimes they work sometimes they don't and very car dependant. The dynaudio esotec and brax matrix are also soft dome mids and completely different again even though in principle they are the same, so very hard to generalise how and when best to use them.

But...they can be phenomenal