Waveguide adapters bad idea? - diyAudio
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Old 7th July 2013, 11:12 PM   #1
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Default Waveguide adapters bad idea?

I'm interested in trying out my first horn driver, the B&C DE250 but I am limited in waveguide choices. Is it bad for sound quality to use an adapter to use threaded waveguides with this driver?
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Old 8th July 2013, 02:09 AM   #2
AllenB is offline AllenB  Australia
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Since you are interested in 'trying it out', an adapter will get you started. The throat profile seems to be critical but if your adapter and horn are reasonable you may still get good sound. You'd be re-doing the crossover when you change it, however. I've been down that road and I modified the adapter to suit the desired profile.

Last edited by AllenB; 8th July 2013 at 02:13 AM.
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Old 10th July 2013, 04:24 AM   #3
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Default There is Nothing Wrong with the Idea of an Adapter!

Use answers to the following questions as a guide when designing one:

Question #1
Assuming a satisfactory adapter can be designed, will the marriage of the driver and horn be a good one?

Is the horn large enough to properly load the driver to its lowest frequency of operation?
Usually this frequency limit is about octave below the high pass crossover frequency.
Is the application long or short throw?
Will HF beaming be sufficiently mitigated by the horn/driver combination?

Question #2
Is the required transition in one or two dimensions?

Are we just transitioning driver exit and horn entry slopes while maintaining a circular cross-section?
Or, are we also transitioning into a rectangular or bow-tie cross-section.
Here the wave front is being transformed from a surface approximating spherical cap to that of a of a torridal segment.
Mitigating HOMs under these conditions will be near to impossible.

Question #3
Is a smooth transition from the driver to the outside air possible?

Any discontinuities in this transition, whether introduced in the adapter or not, will cause HOMs to be triggered across the air column enclosed by the horn.
Other resonances formed along the horn axis will be triggered by reflectance of the horn mouth.


Regards,

WHG

Last edited by whgeiger; 10th July 2013 at 04:29 AM.
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Old 10th July 2013, 12:38 PM   #4
bwaslo is offline bwaslo  United States
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Spinmeister, what is limiting you in waveguide choices? Parts Express and Denovo both have a number of bolt-on waveguides for pretty cheap. Denovo in particular has some that aren't much more than the shipping cost.
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Old 10th July 2013, 07:53 PM   #5
gedlee is offline gedlee  United States
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It is always best to have the horn go right down to the diaphragm, but this is not practical when one wants to allow for interchangeable horns. So basically all compression drivers already have "adapters". That said adding another one is not necessarily a disaster, but it can be. It is how it is done that matters, not whether or not one is used. And each case is different. So if you want an answer you would need to note a particular situation.

Clearly avoiding an adapter avoids the question altogether.
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Old 10th July 2013, 09:11 PM   #6
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Quote:
Originally Posted by bwaslo View Post
Spinmeister, what is limiting you in waveguide choices? Parts Express and Denovo both have a number of bolt-on waveguides for pretty cheap. Denovo in particular has some that aren't much more than the shipping cost.
The SEOS 12 looks good and works without that adapter. Since its included, I can mess with it with other drivers.
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Old 10th July 2013, 09:15 PM   #7
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Quote:
Originally Posted by gedlee View Post
Clearly avoiding an adapter avoids the question altogether.
The only two drivers I'm interested in are the BMS 4552 and DE250. They are both bolt on.

Any input on them? I was looking to avoid titanium. The BMS appears to reach higher in frequency. I can definitely hear higher than most and missing much after 15K will bother me.
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Old 11th July 2013, 09:24 PM   #8
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Quote:
Originally Posted by SpinMonster View Post
The only two drivers I'm interested in are the BMS 4552 and DE250. They are both bolt on.

Any input on them? I was looking to avoid titanium. The BMS appears to reach higher in frequency. I can definitely hear higher than most and missing much after 15K will bother me.
Avoiding titanium, do you have an allergy ?

You can listen to the BMS 4552 and 4550 compared both to other drivers and an original recording here:
High Frequency Compression Driver Evaluation

Both BMS drivers sound good, the less expensive 4550 has more clean output below 1000 Hz.

Both have a HF "zing" around 18 kHz, which I can't comment on since I can't hear it.

I can remember hearing 16,750 Hz from CRTs long ago...

Edit- turns out the CRT flyback transformer was only 15.734 kHz, in retrospect maybe 16 kHz was my "all time high"...

Art

Last edited by weltersys; 11th July 2013 at 09:28 PM.
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Old 11th July 2013, 09:39 PM   #9
gedlee is offline gedlee  United States
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Quote:
Originally Posted by SpinMonster View Post
The only two drivers I'm interested in are the BMS 4552 and DE250. They are both bolt on.

Any input on them? I was looking to avoid titanium. The BMS appears to reach higher in frequency. I can definitely hear higher than most and missing much after 15K will bother me.
I think that the DE250 is a classic design and the best 1" driver for the money (but then they are all pretty much the same.)

Missing "after 15k" is all in head because it is not in your ears.
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Old 11th July 2013, 10:07 PM   #10
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Originally Posted by gedlee View Post
Missing "after 15k" is all in head because it is not in your ears.
Earl,

Like Ronnie Reagan said, "There you go again".

My girlfriend ( less than a year younger than my 1956 model carcass) hears 20 kHz with no problem at all. Of course, she does not care about HF response of speakers, while I miss no longer being able to tell cymbal brands without needing to look at the name tag on them due to my upper hearing fading away by the year.

Interestingly, her mother requires hearing aids to be able to hear conversations.

Art
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