Can anyone tell me if this layout works well? I see 3+ Bertha drawings on the internet each with slight variation in the geometry. I am wondering if there is one that is actually perfectly correct / true to the original? I attached the one that I think looks honest and usable for verification.
Thanks,
Thanks,
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If built solidly, that design will work well with the correct drivers.
The dimensions you show fit the EAW BH882iP, Richard Long's 1970s "Berthas" may be slightly different.
Slight variations in the geometry won't make any difference you would hear in any indoor deployment, driver choice will make more response variation.
Huge cabinet, considering response drops about 24dB per octave below 38Hz, with the extension should get down to ~30Hz.
The standoff baffle material depth is OK for drivers with Xmax ~8mm, should be increased if you were going to use high excursion drivers.
Thanks weltersys. Good to hear confirmation on that. I can measure these against a real set of Richard's Berthas other than the fact that I can't destroy the artifacts to obtain the deeper horn fold measurements.. I can confirm some stuff though. Like volume of the rear chamber, S4, S5, probably the size of the throat chamber / S1.
Does anyone know what drivers it used? I heard the originals used JBL drivers and the RLA ones were Eminence. The RLA ones were apparently cheaper models than then JBLs but worked better. I'm sans part numbers on the transducers.. Maybe we get a HornResp file going? I was thinking of making an enlarged back cover to fit modern speaker motors or you can use a flat cover and use the classics.. I'll share the final DXF files if anyone wants it. 18mm Baltic with dados for easy horn fold alignment. Bet these would have ripped with PD1850..
I can't believe they use this much plywood 😳
Does anyone know what drivers it used? I heard the originals used JBL drivers and the RLA ones were Eminence. The RLA ones were apparently cheaper models than then JBLs but worked better. I'm sans part numbers on the transducers.. Maybe we get a HornResp file going? I was thinking of making an enlarged back cover to fit modern speaker motors or you can use a flat cover and use the classics.. I'll share the final DXF files if anyone wants it. 18mm Baltic with dados for easy horn fold alignment. Bet these would have ripped with PD1850..
I can't believe they use this much plywood 😳
Hmm, that far back they were most likely Cerwin Vega, 'Loud is Beautiful if its Clean! 😉
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Alright well let’s start from square one. I’ll do some math and get some length and cross sectional area data put together for horn resp
I wish I had space for these... and then skills to build a pair. Cannot fit more than a quad of B36 clones with 15" woofers and that is already really tight already🙂 Looking forward to seeing pictures from the build!
About a month ago you were interested in a "sub made to hug a wall".
If you can use a room's corner walls as the horn extension only a fraction of the plywood is needed for ~30Hz response.
The room corner trihedral mouth would be considerably larger than the 9951 mouth extension.
The Klipschorn or Tom Danley's "Bdeap" (Boundary Dependent External Air Path) are examples of the concept.
https://www.freepatentsonline.com/20040238268.pdf
The proximity to the corner boundary changes the response, the horn loads to a lower frequency when around 10" from the wall:
https://forums.prosoundweb.com/index.php?topic=75746.0
Lots of options in FLH.
Art
I built a club in 1985 with Richard. It had 4 of 10 foot wide Berthas. I visited Richard in his shop in NYC where he was finishing the mouths and Berthas. The mouths has 3 side sections to the expansion , rather than the 2 on the standard 8 foot.
The Bertha Eminence woofer part number 18016 67-8525. (8525 was a date code).
i tried Celestions and JBL in the Berthas, but it tore them apart quickly. I tried buying replacement Eminences from Kenny who took over Richard’s business after he passed in 1986, but he stiffed me after I made payment for 4 of them. I also used some EAW 882 with mouths in another club, but never has to replace the drivers and I quit servicing the club not long after it was installed.
The Bertha Eminence woofer part number 18016 67-8525. (8525 was a date code).
i tried Celestions and JBL in the Berthas, but it tore them apart quickly. I tried buying replacement Eminences from Kenny who took over Richard’s business after he passed in 1986, but he stiffed me after I made payment for 4 of them. I also used some EAW 882 with mouths in another club, but never has to replace the drivers and I quit servicing the club not long after it was installed.
Can current drivers be used in the berthas? Or design needs to be tweaked for it.
Just curious , what is the compression ratio on the berthas , as far as I know compression rations higher than 3.8:1 needs very strong motor and cones drivers , weak drivers will shred in to pieces under a high compression horn
Just curious , what is the compression ratio on the berthas , as far as I know compression rations higher than 3.8:1 needs very strong motor and cones drivers , weak drivers will shred in to pieces under a high compression horn
EAW used RCF L18P200N . The Eminince didn’t look as robust a motor or frame as JBL, Celestion etc, , but it worked.
We used 2 of the 10 foot Berthas on top of each other to save space on the dance floor. The standard 8 foot Bertha had a 28 foot mouth, the 2 x 10 foot had a 70 foot mouth. and there were 2 sets of them on the dance floor. Went pretty low and loud.
the L18P200N is no longer made,
Fs was 28Hz
Xmax 9mm and BL 23
|
CIARE 18.00SW-8
| Resonant Frequency (fs) | 36Hz |
| Impedance (Re) | 7 ohms |
| Electrical Factor(Qes) | .55 |
| Mechanical Q (Qms) | 6.7 |
| Total Q (Qts) | .5 |
| Compliance Equiv. Vol. (Vas) | 93 Liters/3.28cu. ft. |
| Voice Coil Overhang (Xmax) | 14.0mm |
| BL Factor | 32.5 T-M |
| Diaphragm Mass (Mms) | 377 Grams |
| Surface Area of Cone (Sd)m2 | 0.1134m2 |
| Reference Efficiency | .73% |
| Coil Inductance (Le) | 3.0mH |
CIARE NDH18-4S
| Resonant Frequency (fs) | 31 Hz |
| Impedance (Re) | 6.1 ohms |
| Coil Inductance (Le) | 1.9mH |
| Electrical Factor (Qes) | .33 |
| Mechanical Q (Qms) | 9.8 |
| Total Q (Qts) | .32 |
| Compliance Equiv. Vol. (Vas) | 239 Liters/8.44 cu. ft. |
| Voice Coil Overhang (Xmax) | 11.5mm |
| BL Factor | 27.7 T-M |
| Diaphragm Mass (Mms) | 212 Grams |
| Surface Area of Cone (Sd)m2 | 0.1164m2 |
| Reference Efficiency | 2.1% |
BEYMA 18QLEX1600FE
| Resonant Frequency (fs) | 30 Hz |
| Impedance (Re) | 5.3 ohms |
| Coil Inductance (Le) | 3.9 mH |
| Mechanical Q (Qms) | 6.5 |
| Electrical Factor (Qes) | .24 |
| Total Q (Qts) | .23 |
| Comp. Equivalent Vol. (Vas) | 6.89 ft3 / 195 Liters |
| Voice Coil Overhang (Xmax) | 13.0 mm |
| Moving Mass (Mms) | 323 Grams |
| Surface Area of Cone (Sd)m2 | 0.1255m2 |
| BL Factor | 36.4 N/A |
| Reference Efficiency | 2.1% |
| Displacement Volume (Vd) | 1631 cm3 |
RCF LF18X451
| Resonant Frequency (fs) | 30 Hz |
| Impedance (Re) | 5.4 ohms |
| Coil Inductance (Le) | 2.9mH |
| Electromagnetic Q (Qes) | .29 |
| Mechanical Q (Qms) | 6.7 |
| Total Q (Qts) | .28 |
| Compliance Equivalent Vol. (Vas) | 220 Liters/7.77cu. ft. |
| Voice Coil Overhang (Xmax) | 13.5mm |
| BL Factor (BL) | 30.5T-M |
| Effective Moving Mass (Mms) | 260 grams |
| Surface Area of Cone(Sd) | .122 m2 |
| Reference Efficiency | 1.9% |
B&C 18DS115
| Resonant Frequency (fs) | 30 Hz |
| Impedance (Re) | 5 ohms |
| Electrical Factor(Qes) | .21 |
| Mechanical Q (Qms) | 4.3 |
| Total Q (Qts) | .2 |
| Compliance Equiv. Vol. (Vas) | 168 Liters/5.93cu. ft. |
| Voice Coil Overhang (Xmax) | 16.5mm |
| Reference Efficiency | 1.9% |
| Diaphragm Mass (Mms) | 330 grams |
| BL Factor | 39 T-M |
| Surface Area of Cone (Sd)m2 | 0.1210m2 |
| Coil Inductance (Le) | 3.85mH |
| EBP | 142 |
If FLH is desired, maybe the SuperBassHorn could be a better option It can reach 30Hz, no internal space wasted and bigger mouth.
Link for custom model in parametric CAD
https://freeloudspeakerplan.rf.gd/pages/sbh.htm
Original PDF plan also attached for replication, but customize it for a specific drive is smarter.
Ps.: The only change i would do regarding usage intention would be removing the offside driver by adding panels and throat chamber that will increase bandwidth extension in the upper range.
Link for custom model in parametric CAD
https://freeloudspeakerplan.rf.gd/pages/sbh.htm
Original PDF plan also attached for replication, but customize it for a specific drive is smarter.
Ps.: The only change i would do regarding usage intention would be removing the offside driver by adding panels and throat chamber that will increase bandwidth extension in the upper range.
Attachments
Lord,
the superbass horn uses the RCF LF18N401 correct ?
looks like RCF no longer make it
but now they make this one that looks like the new version of the 18N401
https://www.usspeaker.com/rcf - LF18X401-1.htm
the superbass horn uses the RCF LF18N401 correct ?
looks like RCF no longer make it
but now they make this one that looks like the new version of the 18N401
https://www.usspeaker.com/rcf - LF18X401-1.htm
ohh i found the N version here
https://www.planetdj.com/rcf-lf18n401
BL factor (BL): 27.80 T x m
DC resistance (Re): 5.10 ohm
Effective moving mass (Mms): 201 gr
Effettive piston area (Sd): 0.12 m2
Electrical factor (Qes): 0.27 Qes
Equivalent Cas air loaded (Vas): 257 liters
Half-space efficency (Eff): 3.01%
Max. linear excursion (Xmax): 9 mm
Mechanical factor: 6.50 Qms
Resonance frequency (Fs): 32 Hz
Total factor: .26 Qts
Voice coil inductance @ 1kHz (Le1k): 2.50 mH
VS the X version
BL factor (BL): 26.50 T x m
DC resistance (Re): 5.40 ohm
Effective moving mass (Mms): 215 gr
Effettive piston area (Sd): 0.12 m2
Electrical factor (Qes): 0.31 Qes
Equivalent Cas air loaded (Vas): 274 liters
Half-space efficency (Eff): 2.30%
Max. linear excursion (Xmax): 12 mm
Mechanical factor: 7.40 Qms
Resonance frequency (Fs): 30 Hz
Total factor: 0.30 Qts
Voice coil inductance @ 1kHz (Le1k): 0.83 mH
https://www.planetdj.com/rcf-lf18n401
BL factor (BL): 27.80 T x m
DC resistance (Re): 5.10 ohm
Effective moving mass (Mms): 201 gr
Effettive piston area (Sd): 0.12 m2
Electrical factor (Qes): 0.27 Qes
Equivalent Cas air loaded (Vas): 257 liters
Half-space efficency (Eff): 3.01%
Max. linear excursion (Xmax): 9 mm
Mechanical factor: 6.50 Qms
Resonance frequency (Fs): 32 Hz
Total factor: .26 Qts
Voice coil inductance @ 1kHz (Le1k): 2.50 mH
VS the X version
BL factor (BL): 26.50 T x m
DC resistance (Re): 5.40 ohm
Effective moving mass (Mms): 215 gr
Effettive piston area (Sd): 0.12 m2
Electrical factor (Qes): 0.31 Qes
Equivalent Cas air loaded (Vas): 274 liters
Half-space efficency (Eff): 2.30%
Max. linear excursion (Xmax): 12 mm
Mechanical factor: 7.40 Qms
Resonance frequency (Fs): 30 Hz
Total factor: 0.30 Qts
Voice coil inductance @ 1kHz (Le1k): 0.83 mH
They don't make enough stuff with flat magnets anymore... the rear chamber seems like it usually has to be bigger.. Hey the superbass horn looks like a lot of fun! Might have to optimize one for Faital 18XL2000 🙂
Here is where I am with the BH882.. It's a good starting point for entering it into horn resp.. ☕
S1 = 35cm X 20.5cm = 717^3cm doubled for 2x transducers and it's 1435^3cm
L1-2 = 53.5cm
S2 = 47cm X 20.5cm = 963.5^3cm, doubled for each half of the unit ( it's a W.. ) and S2=1927^3cm
L2-3 = 90.5cm
S3 = 20.15cm x 103cm = 2075.5^3cm, doubled for each half of the unit ( it's a W.. ) and S3= 4151.9^cm
L3-4 = 87.71cm
S4 = 50.75cm X 103cm = 5227.25cm, doubled for each half of the unit ( it's a W.. ) and S4= 10,545.5^3cm
😵💫
Hey look at that, pretty simple how each cross sectional area just about doubles other than S1..
be back soon..
Here is where I am with the BH882.. It's a good starting point for entering it into horn resp.. ☕
S1 = 35cm X 20.5cm = 717^3cm doubled for 2x transducers and it's 1435^3cm
L1-2 = 53.5cm
S2 = 47cm X 20.5cm = 963.5^3cm, doubled for each half of the unit ( it's a W.. ) and S2=1927^3cm
L2-3 = 90.5cm
S3 = 20.15cm x 103cm = 2075.5^3cm, doubled for each half of the unit ( it's a W.. ) and S3= 4151.9^cm
L3-4 = 87.71cm
S4 = 50.75cm X 103cm = 5227.25cm, doubled for each half of the unit ( it's a W.. ) and S4= 10,545.5^3cm
😵💫
Hey look at that, pretty simple how each cross sectional area just about doubles other than S1..
be back soon..
