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Multi-Way Conventional loudspeakers with crossovers

SYN 9:  a change in direction
SYN 9:  a change in direction
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Old 14th September 2021, 02:09 PM   #121
mark100 is offline mark100  United States
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Join Date: Dec 2010
SYN 9:  a change in direction
For the 4mdn34's, i recessed 3 7/8" diameter, 6mm deep.
Both to allow for excursion, and to reduce the thickness of the ports. (Horn is 12mm BB)
The ports are 15/16" diameter, with centers at 3 1/2" from throat.
They lie tangent to the horn's top and bottom flares as seen from front view posted earlier.
4 in mid mount.jpg

One quick indoor measurement showed no change to their response when enclosed.
Which surprised me, as I thought something would change....but no....

A similar surprise occurred testing different 12"s.....kappalite 3012LF, faital 12pr320, and rcf mb12n351.....I could not tell their response traces apart.
The horn seems to dominate things somehow....


Making sawdust is a truth serum, huh?

So is listening...still have no clue why adding the small mids brings so much extra SQ to the party.
Can't see a bit of difference in mag, phase, decay, THD, etc..... between taking the CD straight to 12"s, versus adding the small mids as a bridge.

About to get serious with modulation testing like Art Welter has done.....would love to find some objective answers.
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Old 14th September 2021, 04:55 PM   #122
hornsteff is offline hornsteff  Denmark
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Join Date: Aug 2010
Location: Loejt Kirkeby, Aabenraa
Thanks again for sharing your experience.

Yes, there must be some explanation! Looking forward to Arts modulation test.

Hmm strange, that the response of the midranges is not affected! Maybe the volume behind the cones needs to be much smaller to create a higher HP-roll-off-frequency?
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Old 14th September 2021, 06:46 PM   #123
mark100 is offline mark100  United States
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Join Date: Dec 2010
SYN 9:  a change in direction
Owe a couple of corrections:

In #117 i said displacement increases 16x (for same SPL) per octave decrease.
Meant to say 4x.
(16x error came from thinking in two-octave terms, trying to use each section in 5-way for as close to two-octaves as reasonable.)

And i keep getting the name of the B&C 4" mids wrong.... it's 4NDF34.

Ok, back to current discussion...
Steffen, did you mean (1) volume between the cone and the port?
Or (2) the volume of the rear chamber behind the cone?

Because if (1), that should create a higher frequency low-pass filter.
Since the driver is already strong all the way to 1kHz as is, I haven't bothered with reducing space there. So it was the same for both unenclosed and enclosed.

If (2),
I just ran Hornresp for a sealed 4ndf34....
Shows it only makes some difference below 200Hz, and then very little. So sim ties to experience nicely, i think. Box size doesn't matter here, yea!
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Old 14th September 2021, 07:55 PM   #124
hornsteff is offline hornsteff  Denmark
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Hi Mark

At (2) my thought was/is to create a natural roll-off, to hand over to the woofers. I am still hoping to stay in the IIR-domain and maybe use Chriss approach? I dunno yet?

I am still trying to wrap my head around, what happens with filters and PEQs in regard to phase in SYNs! What does the bandpass created by the volume under the cone and the port do to phase, I guess it is just behaving like a filter!? What happens to the phase at the notch-frequency? Bla bla bla...... My current knowledge about filters is mainly in respect to Duelund Syncron Filters, and how a loudspeaker with those filters is created. With a Duelund-crossover you create target-curves for each driver that you have to match acoustically, i.e. by combining the acoustical filtering with electrical filtering to generate the desired frequency-response for each driver. If you do it right, the the woofer, midrange and treble combine coherently, because they share the same phase-curve/rotation. Maybe SYNs are more forgiving in that respect, because the drivers are placed axially and not stacked vertically!?

AAAAARGH I cant really explain what it is I am trying to figure out! I think I simply need to build something and try things my self, to find out what happens! Asking and
to formulate questions is not that easy, understanding the answer can be equally challenging! I have ordered some books that hopefully can help with my lack of knowledge.

I go to sleep now!

Steffen

Last edited by hornsteff; 14th September 2021 at 08:01 PM.
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Old 15th September 2021, 06:09 AM   #125
hornsteff is offline hornsteff  Denmark
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Join Date: Aug 2010
Location: Loejt Kirkeby, Aabenraa
Hi Mark

I got a data-sheet for the B&C 4NDF34-16 from B&C and today also from TLHP.

That data was not shown on neither B&Cs or TLHPs homepage.

TLHP says: "The 4NDF34-16 is still in the standard range, we have no information from B&C Speakers, as of today, which precisely indicates that this model is discontinued."

I thought it would be nice to have that information out.

Steffen
Attached Files
File Type: pdf 4NDF34-16_datasheet[832].pdf (454.5 KB, 12 views)
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Old 15th September 2021, 01:50 PM   #126
mark100 is offline mark100  United States
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Join Date: Dec 2010
SYN 9:  a change in direction
Quote:
Originally Posted by hornsteff View Post
Hi Mark

At (2) my thought was/is to create a natural roll-off, to hand over to the woofers. I am still hoping to stay in the IIR-domain and maybe use Chriss approach? I dunno yet?

I am still trying to wrap my head around, what happens with filters and PEQs in regard to phase in SYNs! What does the bandpass created by the volume under the cone and the port do to phase, I guess it is just behaving like a filter!? What happens to the phase at the notch-frequency? Bla bla bla...... My current knowledge about filters is mainly in respect to Duelund Syncron Filters, and how a loudspeaker with those filters is created. With a Duelund-crossover you create target-curves for each driver that you have to match acoustically, i.e. by combining the acoustical filtering with electrical filtering to generate the desired frequency-response for each driver. If you do it right, the the woofer, midrange and treble combine coherently, because they share the same phase-curve/rotation. Maybe SYNs are more forgiving in that respect, because the drivers are placed axially and not stacked vertically!?

AAAAARGH I cant really explain what it is I am trying to figure out! I think I simply need to build something and try things my self, to find out what happens! Asking and
to formulate questions is not that easy, understanding the answer can be equally challenging! I have ordered some books that hopefully can help with my lack of knowledge.

I go to sleep now!

Steffen
Yeah, the whole phase rotation / summation thingy can get confusing.
The good news imo, is once we start trying things out for ourselves and making measurements, it gets clearer quicker.


Single drivers in open air tend to have natural 2nd order roll-offs on both ends of their bandwidth. With these freq response roll-offs comes 2nd order phase rotation.
(Phase is relatively flat within the drivers in-band reponse where magnitude is relatively flat.)

The mids in a MEH have a steeper HF rolloff than 2nd order due to the acoustic lowpass formed by the reduced air volume between the cone and port.
I get about 30dB down, an octave away from the high corner at around 1kHz, with the 4ndf34's.
Which means a boat load of phase rotation above 1kHz...clearly unusable territory.
So it's important to crossover well below that high corner if trying to use low order IIR crossovers.....simply to have room to tie it to the CD in its flatter mag and phase region.
With steep linear phase xovers, the mids can be used all the way up to the high corner if desired.

With regard to what happens to phase at notch frequency, the notch that is made from reflections bounced back from the throat....well, anytime their is rapid mag change, there is rapid phase change.
That's why it's important to xover below notch freq.
How far below again depends on how wide a plateau of relatively flat mag and phase below notch frequency there is to work with.



My take on xovers ....(is first off, folks make them waaaaaaay too difficult, but i'll stay away from there haha)

Ok, my retake on xovers is that they all need to start with a complementary acoustic order in mind. A complementary acoustic order that is achieved after adding electrical filters.
(some folks advocate using non-complementary acoustic orders to steer lobing, but i think that is a lot of overcomplicated horse wallop thinking ..i digress again )

Anyway, like your Dueland example where you start with a target acoustic curve, i always start with a target acoustic curve..... a target acoustic xover.

Whether you massage response towards the target curve using IIR PEQs in-band and out-of-band, with or without "named filters/xovers", or use linear phase xovers, or use any combination of any of those, .....is totally immaterial towards the goal of matching the target curves.

The real decision that matters imho, is choosing appropriate target curves to begin with, that can be realistically reached with the electrical filter toolset available.

Differences in techniques are more about semantics than anything else....all approaches do the same thing if done correctly.


Everyone wants flat mag and as little phase rotation as possible.
Which means keeping order low if using IIR.
Or use linear phase xovers if summation benefits from higher order.
That simple really

Hope all that rambling helped
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Old 15th September 2021, 02:33 PM   #127
hornsteff is offline hornsteff  Denmark
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Join Date: Aug 2010
Location: Loejt Kirkeby, Aabenraa
Thanks Mark. I appreciate your patience and willingness to share your experience, I know those questions can get real complicated in a hurry! The rambling helps. :-)

As you say, build, measure and learn. :-)
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Old 16th September 2021, 03:10 AM   #128
grec is offline grec  United States
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Join Date: Mar 2006
Location: Destin
Thank you Mark.
I'm really interested in your adventure.
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Old 16th September 2021, 07:47 AM   #129
pelanj is offline pelanj  Czech Republic
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Join Date: Jul 2008
SYN 9:  a change in direction
This thread (and the previous one) are really inspirational. I feet the urge to finally finish my AMT based horn
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Old 16th September 2021, 03:23 PM   #130
mark100 is offline mark100  United States
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Join Date: Dec 2010
SYN 9:  a change in direction
Thx for the kind words guys....
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