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Old 17th January 2009, 04:51 PM   #1
nl is offline nl  United States
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Default DIY Synergy horn ideas

I'm thinking about a Danley Synergy-type horn for home use with the following characteristics:

2-way design using classic 1.4" driver like RCA MI-9584, crossed around 400hz. Highs provided by separate tweeter. Possibly using a coaxial driver like B&C DCX-50.

Lower mids provided by a pair of 8", 10" or 12" drivers.

About 100 watts max expected power. (No need for 2000W handling ability. At 110db, 100 watts is 130db as it is!)

Square cross section with about 30 degree angle and about four foot length (similar to SH-25).

Double-layer MDF construction.

Cutoff around 80hz-100hz.

Aiming for "half size" mouth to sit on floor (half space), about 28"x 28".

My main questions are regarding the addition of the two cone drivers. At 400hz, the longer wavelengths make things rather simpler than the 1200hz crossover of the Danley three-way models.

Regarding the "holes" going from the cone driver to the horn, what is a good size? I have heard that a good rule of thumb is that a) the size of the hole should correspond to the throat of a comparable front horn, eg. 3" diameter throat for 6" diaphragm, and b) the total size of the holes (for two drivers) should be equivalent to the cross-sectional area of the horn at the point they enter the horn. However, it seems that the Danley designs use smaller holes than this.

At 400hz, the quarter-wave length is about 7", so the holes should be less than 7" from the throat. This may eliminate the 12" driver from consideration, as its 6" radius would put it quite close to the limit, not to mention some sort of back chamber for this driver. Thus, I'm tending toward the 8" drivers, perhaps out of the B&C catalog, which might allow 5" distance. However, I would like very high efficiency, of 110db perhaps.

Lastly, a hole in the wall of a horn tends to act as a notch filter. Should I be concerned with the holes' effect on the output of the mid-high driver?

Thanks for your help.
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Old 18th January 2009, 09:39 AM   #2
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G'day nl

You've made a few strange choices here.

Having a separate tweeter somewhat defeats the purpose of building a Unity/Synergy horn. These things are all about flat power response and single source behavior throughout much of their range, both of which you will be throwing away with the separate tweeter.

That old RCA driver will not give you the sensitivity you are after at the top end of it's frequency range. You'll be hard pressed getting 110dB/W/M at high frequencies with any CD horn. Sensitivity aside, there are many much better compression drivers available today from the likes of B&C, BMS and 18 Sound. The BMS 1" will let you cross at slightly below 1KHz to some 8" drivers or perhaps 4x 6" drivers. You should be able to achieve a bit over 100dB/W/M with this driver.

Cheers

William Cowan
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Old 18th January 2009, 10:11 AM   #3
kstrain is offline kstrain  Scotland
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Quote:
Originally posted by cowanaudio
G'day nl
Sensitivity aside, there are many much better compression drivers available today from the likes of B&C, BMS and 18 Sound.

Cheers

William Cowan
G'day William,

Pardon me asking here, but do you recommend a particular 18 Sound CD? I ask as the ones I measured (and listened to) were pretty dreadful, with many sharp resonance features not even hinted at in the spec sheet. That was in direct head to head comparison of the ND1060 and the DE250, which might have been thought to be roughly similar. The DE250 was a delight in comparison on a heavily damped XT1086 horn. I'm going to have a BMS 1" to compare the same way, within the next week or so.

Ken

Typo: ND1060
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Old 19th January 2009, 12:07 AM   #4
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G'day Ken

I've used the XD120 for quite some time in a system at home and liked the sound and the way it measured. A friend used one of the higher power 1" 18 Sound drivers in a system he built and it sounded great. Not sure what model that driver was, but they're not all bad, but I have also heard the ND 1060 has a few problems.

I currently use the B&C DE25-16 as well as a BMS 4550 in another system (On the XT 1086 horn). I am very impressed with both these drivers. The 4550 will soon end up in a Unity horn.

Cheers

William Cowan
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Old 19th January 2009, 02:56 PM   #5
nl is offline nl  United States
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HF rolloff, and EQ compensation due to CD loading, is a consideration. I hadn't thought about it much. I would imagine that the narrow dispersion (only 30deg) might help somewhat in that regard. However, I am interested mostly in the method of integrating the cone drivers into the horn, notably the size of the holes ("throats"?), and the relation of the holes to the cross-sectional area of the horn at the entry point.

I would consider a 1" compression driver, which brings up the question: given lower power handling needs, would it be possible to make a decent two-way system with, for example, two 8" drivers and a 1" compression driver crossed around 1000hz, usable to 100hz or lower?
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Old 19th January 2009, 03:07 PM   #6
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The size (diameter, length, number) of the midrange holes will effect the response of the mids and distortion performance at low frequencies (and thus limit how loud they can go at low frequencies). The holes will also effect the response of the tweeter. Things I've found in the past are that typical midrange drivers have flat response with larger holes, but this destroys the output from the high frequency driver (response curve is very ragged). My advice would be to simulate the response to arrive at a good design.

I also agree with William that using a separate tweeter does not make much sense.
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Old 20th January 2009, 05:53 PM   #7
kstrain is offline kstrain  Scotland
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Quote:
Originally posted by cowanaudio
G'day Ken

I currently use the B&C DE25-16 as well as a BMS 4550 in another system (On the XT 1086 horn). I am very impressed with both these drivers. The 4550 will soon end up in a Unity horn.

Cheers

William Cowan
G'day William,

and many thanks for that. I've tested a BMS 4548 PLUS today and will soon add what little I have to say about this very nice driver to a post on my thread comparing the DE250 with the ND1060.

Ken
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Old 3rd September 2009, 12:35 AM   #8
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Quote:
Originally Posted by cowanaudio View Post

I currently use the B&C DE25-16 as well as a BMS 4550 in another system (On the XT 1086 horn). I am very impressed with both these drivers. The 4550 will soon end up in a Unity horn.
Just curious if the 4550 ever ended up in the unity horns. I have been impressed with the 4550 and would love to incorporate it into my unitys but I probably don't have the skill to implement it with a passive crossover without discussion and/or piggybacking on another's skill. Since the unity community seems to be very helpful, I am hopeful these drivers will be implemented by some benefactor.

Thanks,
rick
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Old 3rd September 2009, 03:42 AM   #9
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Quote:
Originally Posted by nl View Post
I'm thinking about a Danley Synergy-type horn for home use with the following characteristics:

2-way design using classic 1.4" driver like RCA MI-9584, crossed around 400hz. Highs provided by separate tweeter. Possibly using a coaxial driver like B&C DCX-50.

Lower mids provided by a pair of 8", 10" or 12" drivers.

About 100 watts max expected power. (No need for 2000W handling ability. At 110db, 100 watts is 130db as it is!)

Square cross section with about 30 degree angle and about four foot length (similar to SH-25).

Double-layer MDF construction.

Cutoff around 80hz-100hz.

Aiming for "half size" mouth to sit on floor (half space), about 28"x 28".

My main questions are regarding the addition of the two cone drivers. At 400hz, the longer wavelengths make things rather simpler than the 1200hz crossover of the Danley three-way models.

Regarding the "holes" going from the cone driver to the horn, what is a good size? I have heard that a good rule of thumb is that a) the size of the hole should correspond to the throat of a comparable front horn, eg. 3" diameter throat for 6" diaphragm, and b) the total size of the holes (for two drivers) should be equivalent to the cross-sectional area of the horn at the point they enter the horn. However, it seems that the Danley designs use smaller holes than this.

At 400hz, the quarter-wave length is about 7", so the holes should be less than 7" from the throat. This may eliminate the 12" driver from consideration, as its 6" radius would put it quite close to the limit, not to mention some sort of back chamber for this driver. Thus, I'm tending toward the 8" drivers, perhaps out of the B&C catalog, which might allow 5" distance. However, I would like very high efficiency, of 110db perhaps.

Lastly, a hole in the wall of a horn tends to act as a notch filter. Should I be concerned with the holes' effect on the output of the mid-high driver?

Thanks for your help.
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