Thanx!
My cheap compact home stereo is limited in low end, ~110 dB in listening position for 15-30 Hz. But the overall impression of the record is quite favorable.
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Compression drivers?
- Thread starter DanielT
- Start date
My cheap compact home stereo is limited in low end, ~110 dB in listening position for 15-30 Hz. But the overall impression of the record is quite favorable.
dasdoing
Major Contributor
Thanx!
My cheap compact home stereo is limited in low end, ~110 dB in listening position for 15-30 Hz. But the overall impression of the record is quite favorable.
that loud fluttering is what I was talking about in my original post. hearing that with a compression driver is almost scary.
dasdoing
Major Contributor
and Katz said the correct level is 7dB above standard Dolby calibration
What is this, 85 dB?
dasdoing
Major Contributor
I am quite interested in the SB CD and horn here…https://josephcrowe.com/products/di...y-15-2-way-monitor-using-sb-audience-products
I do wonder, given this uses a Bianco CD, should I await the inevitable release of a Nero line of CD’s before I buy.
Performance looks great here, and not all that expensive.
I do wonder, given this uses a Bianco CD, should I await the inevitable release of a Nero line of CD’s before I buy.
Performance looks great here, and not all that expensive.
OP
DanielT
Master Contributor
- Thread Starter
- #168
Excited I must say BUT I am wondering about a few things. First, how come measured FR looks so different compared to SB's data?
Especially above around 12 kHz or so and above there. Why this huge rise?
Speaker no. 1786 --- Large DIY 15" 2-way Monitor using SB Audience Products:
SB's own data on the Audience 65CDN-T 1.4" compression driver:
Then, and this actually relates more to room acoustics than compression drivers. If you push speakers into the corners of the listening room, support from the walls boosts the sensitivity but reflections of the sound, will it be optimal?
Edit
But ok if it measures according to the link, in the corners, then FR is ok. 4dB diff to fix (on axes anyway) then notch filter above 10 kHz. FR that is, but reflections in the room?
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I believe he states within the description that he modified the CD (perhaps opened back and placed foam to reduce a resonance, as he has done before).
[Usually] these are diaphragm resonances, [usually] they are more noticeable for large, 3-4", phragms. Coating may help, JBL -SL (aquaplased) phragms seem to be the best\most famous example.
in H280 horn:
BTW your avatar is definetly good.
The difference north of 12 kHz could be a crossover effect or an acoustic effect.
Presumably the crossover is subtracting energy south of 12 kHz in order to equalize the response of the horn/compression driver combination and get a good level-match with the woofer, and perhaps what we are seeing north of 12 kHz is the result of non-subtraction in that region. It is also possible that the region north of 12 kHz is being deliberately boosted by the crossover network, which would show up in the impedance curve as an impedance dip.
It is also possible that the horn in the upper graph has significant pattern-narrowing north of 12 kHz, such that the acoustic energy up there is being "squeezed" into a narrow angle, with the effect of increasing the on-axis SPL in that region at the expense of the off-axis SPL in that region.
OP
DanielT
Master Contributor
- Thread Starter
- #172
Aha! It looks nice if you like a sloping FR. Many people do that, but a 10 dB difference between 1.5 kHz and 6 kHz is a lot. EQ may probably be needed.
And if you like that dispersion on the horn:
Dispersion 60° x 40°
"BTW your avatar is definetly good."
My avatar is the best thing I've posted, expressed here on ASR, anything but it fades to be honest. That it would happen in our lifetime. This mad power, land hungry dictator, brr. Best not to say more.
"....subtracting energy south of 12 kHz in order to equalize the response of the horn/compression driver...."
Aha, that seems reasonable, there is a big difference in the slope between "Speaker no. 1786 --- Large DIY 15" 2-way Monitor using SB Audience Products"
and SB's measurement with their H280 horn.
Here are the data on the SB Audience H280, 1.4 inch
Dispersion so 60° x 40° okay but what is:
Directivity factor (Q) 18
Directivity factor (Dl 13
? Do you know that?
SB Audience H280, 1.4 inch entry, 279 x 279 mm
en.toutlehautparleur.com
Simply "equalization is needed." Always for constant (more or less) directivity horns\waveguides.
The higher the DI, or "Directivity Index", the narrower the radiation pattern is.Dispersion so 60° x 40° okay but what is:
Directivity factor (Q) 18
Directivity factor (Dl 13
? Do you know that?
SB Audience H280, 1.4 inch entry, 279 x 279 mm
View attachment 227771
The higher the Q, the more "pointy" the radiation pattern is. So the two numbers tend to approximately track one another.
The polar pattern graphs you provided show that the pattern changes significantly from low frequencies to high frequencies, so the numbers given by the manufacturer for DI and Q are averages.
Imo the actual graphs convey far more useful information than the Q and DI numbers do.
OP
DanielT
Master Contributor
- Thread Starter
- #175
Aha, got it.
I think several people are interested in this: If you Duke were to put together a full-range two-way speaker (or down to...hm..you choose 20,30,40 Hz yourself) with compression drivers. Which compression drivers, including bass ditto, would you choose?
Parameter budget, hm, same there av choose yourself. It's just a thought experiment. ...or....
Edit:
What do I know. You are a manufacturer. Maybe you have some ready-made models/speakers, or DIY kits?
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That's a big question.
I'd prioritize matching up the radiation patterns of woofer and horn in the crossover region, at least in the horizontal plane. Also, I'd look for a horn with fairly constant directivity, which does not rely on diffraction slots to widen the pattern at high frequencies, and which does not have sharp edges around the mouth. The 18Sound horns are among the best off-the-shelf horns in these respects.
Then I'd look at compression drivers which work well on the chosen horn, paying attention to getting a good match between the exit angle of the compression driver and the entry angle of the horn.
Here's an example of what something like this might look like:
For an imo very well thought-out DIY approach, google "econowave".
The raw response vs crossover is shown on Joseph's site
The basic traits of this driver can be seen in some other measurement's made on a Faital LT142 here
https://www.diyaudio.com/community/threads/a-3-way-design-study.376620/post-6993828
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If I: large format driver (4" or 3" or coax), digital xo 800 and lower, any suitable
midbass andsubs in accordance with available room and possibilities; for example mine https://www.audiosciencereview.com/...-low-q-subs-quasi-plain-wave-radiation.24396/
tuga
Major Contributor
I think several people are interested in this: If you Duke were to put together a full-range two-way speaker (or down to...hm..you choose 20,30,40 Hz yourself) with compression drivers. Which compression drivers, including bass ditto, would you choose?
You can’t get constant directivity full range with a 2-way speaker, unless you are looking at omni dispersion.
For constant narrow using compression drivers on horns you are looking at 4-way minimum.
I like the response of the RCF ND650 in the factory datasheet better, and I guess would consider the poly surround a plus. Among others the Lavoce HD1403 horn looks nice, 80deg horizontal, the B&C ME90 is nice as well.
