The dome midrange thread

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#362
Last time I checked, the 1558SH was $100, so they obviously went up in price. It will still outperform the MD60N in the low end and has lower THD across the board. The problem is again consistency. The MD60N isn't the best dome mid for the price and its size. It does have a smooth pass band above 1.5k but the problems around 1k spoil it. The D7608 is better in this area and will play lower, but needs careful attention regarding the back chamber design. I still prefer to put up with the D7608 quirks to get the effortless midrange its capable of. The solution to the lack of lower mid capability is to use 2 of them with a staggered HP ie. like a 2.5 way setup does.
 
#364
profiguy said:
TW030WA11/12 don't use ferrofluid.

Most mid domes with ferrofluid have the higher viscosity type. Visaton uses a synthetic FF which is more stable long term. Most of the Seas anf Morel also use a synthetic FF.

I sometimes add FF to compression drivers with small VCs that see hard use. I haven't had any issues with it long term, just that it cut down with warranty claims. It barely affects FR when used correctly with the right amount.
Click to expand...
I have 8 Visaton domes all older, the titanium 50 and 25 mm, between 40 and 15 year old
, they all had ferrofluid in them, when checked with Dat3 , they all had (much) higher resonance frequency as they should have, I took out the ferrofluid and now they are back to normal, the very early 50 mm domes have a much higher resonance frequency as the newer ones, I will test them to see if they still are usable....
 
#370
fluid said:
For sure the prices are high but the Bliesma drivers offer some interesting material choices.

I decided on the paper version of the M74 as an inbetween silk and metal.

Unfortunately I still only have pictures and no real data
Click to expand...

Hi Fluid, do you have yet anything more to report? measurements? Listening?

I am torn between deciding m74p or m74s, or D7608...
Under this post i will try to explain why..
 
#372
Hi all, so can you help me on this one thing:
-Is Bliesma m74s good for my use case? or m74p?

I would need middome that goes low as 500-600hz, also the problem is that i need high crossover point of 3-3.5 khz minium. (my ears are sensitive to this region)

So, if we look at the waterfall of those domes:
Screenshot 2024-01-26 at 14.25.18.jpeg


Silk has ridge on 6k, paper less but some still in the region.
I don't think there really is a way to deal with these effectively with my high crossover that has to be LR2? (or LR3)..
Right?

Now if we look at D7608:
Screenshot 2024-01-26 at 14.06.15.png


I think this would fit my use case much better. Maybe i have not looked all the values that take into account here, so any "opposition"?
I really wanted to use Bliesma since i have bad habit of always going for "premium", but maybe it is time to accept that best driver is the best driver for your use case, right?
 
#373
As a retired systems engineer, absolutely, it's all about the use case. However, I understand the pull of the premium. But wouldn't that be the M74B (if you can find a pair)? I think you are going to need to filter out the breakup on any of the options and then apply the L2. It seems to me that the best, in that regard, would be D7608, M74B, M74A and then, considerably more challenging, the M74P and S. The difficulty with the M74P and S is that the breakup is low in frequency, high in volume and either wide for the P or multiple for the S. Contrast that to the D7608 where the breakup is high (but at around 13K still not high enough to ignore?), quite narrow and already down 10 dB or more before the L2.
There are other considerations, though - cost, of course, CTC spacing, even protection against poky little fingers (a big deal for me).
 
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#374
matsurus said:
Hi all, so can you help me on this one thing:
-Is Bliesma m74s good for my use case? or m74p?

I would need middome that goes low as 500-600hz, also the problem is that i need high crossover point of 3-3.5 khz minium. (my ears are sensitive to this region)

So, if we look at the waterfall of those domes:
View attachment 1264885

Silk has ridge on 6k, paper less but some still in the region.
I don't think there really is a way to deal with these effectively with my high crossover that has to be LR2? (or LR3)..
Right?

Now if we look at D7608:
View attachment 1264886

I think this would fit my use case much better. Maybe i have not looked all the values that take into account here, so any "opposition"?
I really wanted to use Bliesma since i have bad habit of always going for "premium", but maybe it is time to accept that best driver is the best driver for your use case, right?
Click to expand...
The D7608 is a pretty large flange so getting center to center spacing at 3.5k perfect is impossible.......you'll have to accept the tradeoff. Best way to mitigate those tradeoffs would be a ribbon tweeter who's narrow vertical dispersion will reduce combing and the amplitude of the primary lobe......better sit your a$$ down to listen though......and make sure the listening axis per the design is centered between the 7608 center and whatever Ribbon you might choose center. Give yourself at least 2m of distance to sum as well.
 
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#375
I was thinking of going for 1.2-1.4 wavelenght rule:

t35c. 110mm
d7608. 152mm

3500hz wavelenght x 1.4 = 13,748 cm
c x c minimal distance = 13,1+ cm


Tmuikku:
Kimmosto original posting of the 1.2-1.4 wl c-c was around beginning of 2021, not sure what the first post was, its on thw htguide, ASR or here, probably mentioned in all. See this for example https://www.audiosciencereview.com/forum/index.php?threads/some-help-with-lobing.22661/post-753404

If one plays with VituixCAD its quite natural to come up with such c-c spacing with conventional multiway speaker. I'd imagine its application dependent if it works or not.

I see it a blessing for designer, freedom. Better to make the new found space available in bigger c-c in good use, its a design freedom and its silly not to take advantage of, especially if it sounds better 😉

Kimmosto:
"
VituixCAD thread on diyaudio contains three examples with real life data and simplified theoretical study about c-c = 1.2 x wave length concept. It's actually quite common in practice. Traditionally XO frequencies 2.5-5 kHz were common, and sound of those speakers was typically smoother and more tolerable than (modern) low XO point. So I'm not trying to invent anything new or provoke. Just giving an answer why some sound features were better in the past; no blood from ears while listening 80s' Gary Moore or Iron Maiden.
Common (modern) opinion/statement is that c-c should be as short as possible. With "normal luck" it hits c-c = 1/2 wave length at XO which causes the worst possible power dip and balance break with conventional unidirectional box speaker. Also risk of power bump above XO point increases with conventional tweeters without wave guide. c-c = 1/4 wave length at XO is just an utopia - worthless to mention for other than XO between mid and woofer, or woofer and small full-range as a tweeter."
 
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#376
Paul Ebert said:
As a retired systems engineer, absolutely, it's all about the use case. However, I understand the pull of the premium. But wouldn't that be the M74B (if you can find a pair)? I think you are going to need to filter out the breakup on any of the options and then apply the L2. It seems to me that the best, in that regard, would be D7608, M74B, M74A and then, considerably more challenging, the M74P and S. The difficulty with the M74P and S is that the breakup is low in frequency, high in volume and either wide for the P or multiple for the S. Contrast that to the D7608 where the breakup is high (but at around 13K still not high enough to ignore?), quite narrow and already down 10 dB or more before the L2.
There are other considerations, though - cost, of course, CTC spacing, even protection against poky little fingers (a big deal for me).
Click to expand...
Hi Paul, i actually don't have good track record with beryllium since my ears are very sensitive to sibilance. I have heard only one speaker with beryllium drivers (and i have heard very expensive ones) that passed my hard limit, and that was only in the very damped and acoustically controlled studio environment with crossover upgraded yamaha ns 1000.
It seems that m74 is out then because of the hard ridges..

Btw: Shouldn't 13k be down about 22db with 3500hz lr2? (i hope i have not understood this uncorrectly)
3500 x2= 7000, 7000 x 2= 14000, ridge in 13k so about 22db down, right?
 
#378
matsurus said:
It seems that m74 is out then because of the hard ridges..
Click to expand...
My view would be different, I chose the paper when I could have picked any other instead. Waterfall plots are the most difficult to interpret and easiest to see gremlins in that may not be a problem in the end system.

All the Bliesma drivers have a flat to rising response. The D7608 a falling one. The frequency responses are nothing alike so without normalization or EQ the waterfall could look quite different.

Look at the impedance responses. The M74S shows signs of breakup in the frequency response but the bump in the impedance is mild. The resonance of the P is strong but consisent with angle so it can be notched quite successfully in the same way Purifi shows in their app note. I think that 3 to 3.5K crossover is quite acheivable with the M74P and certainly with the M74S.

The D7608 has a massive hole at 60 degrees off axis at 3.5K, so in the overall response crossing there will result in eneven directivity. It also has an impedance bump at 2K which can be seen in the waterfall.

LR2 crossovers are hard on the natural rolloff charater of drivers. Other crossover types can give a similar response in the crossover region but cut off the upper end response more sharply. Like an elliptical filter. Like an LR2 but with a deep notch an octave or so higher. That will really suppress the upper end breakup of any of the drivers.

I am sure a decent speaker can be made with any of them. Exactly what will depend on the box, the tweeter etc.
It is almost impossible to acheive a CTC distance that is not a compromise of some form with a 3" dome. Unless you intend to listen close up in the nearfield, a CTC of a wavelength or more is ususally the better compromise and much easier to acheive.
 
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#380
The 920000 version certainly does look advantageous with respect to CTC or, perhaps, put it in a waveguide and boost the low end if that's desirable.

fluid makes good points about the off axis responses and the benefits of an elliptical filter (or the Purifi approach). I used an elliptical filter crossing the RS52AN to the Seas DXT and I felt it helped ameliorate some of the audible impact of the RS52AN breakup. Regarding the off axis responses, below are the normalized off axis graphs, which really help to visualize this.

M74P:
m74p-6_offaxis_normalized_10-50db.png

D7608:
d7608-920010_offaxis_normalized_10-50db.png

However, it seems to me that the M74A might be even better in this regard.

M74A:
m74a-6_offaxis_normalized_10-50db.png
 
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