I am looking at a long term project (either 2 or 3 way depending) involving high efficiency drivers for home use and am looking at this woofer from Precision Devices for a possible 3 way:
PD.18BR40
It appears to have some good specs going for it. Smooth up top and can cross over easily to an (likely 10" ala JBL4345) efficient midrange driver, then horn up top. Figuring a large bass reflex in the neighbourhood of 180L or more tuned to low 30's... Played a bit in Unibox, not too proficient yet, so dunno if I'm overlooking anything.
Precision Devices is new to me. I've seen some mention of them online but am unsure of their quality/reputation. It certainly looks like a nice driver but wonder how it would compare to a say JBL 2240 or 2242?
PD.18BR40
It appears to have some good specs going for it. Smooth up top and can cross over easily to an (likely 10" ala JBL4345) efficient midrange driver, then horn up top. Figuring a large bass reflex in the neighbourhood of 180L or more tuned to low 30's... Played a bit in Unibox, not too proficient yet, so dunno if I'm overlooking anything.
Precision Devices is new to me. I've seen some mention of them online but am unsure of their quality/reputation. It certainly looks like a nice driver but wonder how it would compare to a say JBL 2240 or 2242?
They are available to me locally on sale. It came up on my radar because of price. I had originally had long term plans of employing a JBL pro woofer and this seems to spec well and be fairly priced.
I've run sims in Unibox and have been trying to get a few things to play nice. Excursion and port noise with my tuning still needs to be finessed.
Just not sure if this driver will disappoint or impress.
I've run sims in Unibox and have been trying to get a few things to play nice. Excursion and port noise with my tuning still needs to be finessed.
Just not sure if this driver will disappoint or impress.
That PD 18" specs out more like a high tuned JBL 2241H.
When looking for standins for a 2245h compare the EBP numbers ( EBP = Fs/Qes ).
2245H EBP = 75(hz) , 2241H EBP = 81(hz) , 2242H EBP= 120(hz) , PD 18BR40 EBP =90(hz)
The EBP will give one a reasonable ( quick ) idea as to whether or not the device is a woofer or more of a midbass driver.
- Take the EBP , divide by 2 and one will get an idea of the lower end available ( from within the pass band ) produced by the woofer ( F3 should still be a bit lower ).
PS; EBP stands for "Energy Bandwidth Product"
When looking for standins for a 2245h compare the EBP numbers ( EBP = Fs/Qes ).
2245H EBP = 75(hz) , 2241H EBP = 81(hz) , 2242H EBP= 120(hz) , PD 18BR40 EBP =90(hz)
The EBP will give one a reasonable ( quick ) idea as to whether or not the device is a woofer or more of a midbass driver.
- Take the EBP , divide by 2 and one will get an idea of the lower end available ( from within the pass band ) produced by the woofer ( F3 should still be a bit lower ).
PS; EBP stands for "Energy Bandwidth Product"
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I have seen the PD woofers used in bass scoops (back loaded horn) at events like the Notting Hill carnival where they appear to sponsor a float. It seems to be designed to play at high volume but not super low. It could perform quite well in a sealed box with a large amplifier and lots of EQ as the xmax of 10.5 mm is quite good.
Thanks for the replies. This is much more informational than my usual "which of these 2 woofers is best?". I really should be asking why a woofer isn't well suited, it may teach me something useful.
So Energy Bandwidth Product is a new one for me, and am going to have to do some Googling to see just what it's all about. When I model the woofer in Unibox I get a tune of 30hz and f3 is ~32.5hz. With 400w input I can satisfy the demands of not exceeding Xmax and keep port noise down. At 700w it's another story. No matter what I do, I can't keep the tune and get the Xmax or Port noise to play nice with that tuning. I presume higher tuning would help. Would using the EBP/2 formula (45hz) be a reliable way to deduce optimal tuning freq, and whether a woofer will actually be able to be tuned to Fs?
So Energy Bandwidth Product is a new one for me, and am going to have to do some Googling to see just what it's all about. When I model the woofer in Unibox I get a tune of 30hz and f3 is ~32.5hz. With 400w input I can satisfy the demands of not exceeding Xmax and keep port noise down. At 700w it's another story. No matter what I do, I can't keep the tune and get the Xmax or Port noise to play nice with that tuning. I presume higher tuning would help. Would using the EBP/2 formula (45hz) be a reliable way to deduce optimal tuning freq, and whether a woofer will actually be able to be tuned to Fs?
No, this formula is best used ( IMHO ) just as short-hand to get a rough idea of the low-end capabilities ( when comparing/shopping multiple woofers for a project).
One still wants to tuneup the woofers of their choice to see what the response curve looks like.
- The formula above just helps narrow the herd that much quicker.
If one uses this ratio then one ( should be able to see why Troels chose ) the BMS 18N862 woofer pdf for his large box 4-way ( apart from going the route of tuning it up, etc. etc. ).
- It has an EBP of @ 70hz and a strong motor shifting approx. 267grams of cone weight ( MMS ) which is going to offer authoritative pounding bass reproduction ( IME ).
I own the PD 154 (different parameter from the 18br40) but it perform great
Quality is also top notch and both unit measure within 1db of each other.
PD does use smoothing on their graph and the PD154 breakup at 2khz is much worse than factory graph suggest.
In operation below 300hz, it doesn't matter, it would do great, if you aim for a 800hz crossover, I would be more concerned as 3rd harmonic will peak up at ~660hz (2000/3)
What is your intended crossover slope?
Quality is also top notch and both unit measure within 1db of each other.
PD does use smoothing on their graph and the PD154 breakup at 2khz is much worse than factory graph suggest.
In operation below 300hz, it doesn't matter, it would do great, if you aim for a 800hz crossover, I would be more concerned as 3rd harmonic will peak up at ~660hz (2000/3)
What is your intended crossover slope?
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Good specs for what use? Don't forget that an 18" won't be able to produce much off axis mids, so is IMO limited to bass use. Making a 2 way out of it will be an expensive lesson because it will result in a horrible sounding speaker with a huge off axis mids dip.
Many small subwoofer/bass drivers in separate boxes also sound better then 1 big one due to placement options.
Many small subwoofer/bass drivers in separate boxes also sound better then 1 big one due to placement options.
Heresy I'll tell ya, Heresey!!
Just for fun... You can build a surprisingly competent 18" two way suitable for domestic use using an 18" and dome tweeter. Know eyes are rolling... but it has been done. As a demo - think piece, I designed such a crazy thing for a DIY get together in the S.F. CA area sometime around 2000 or so. I named the thing "The Jokes".
As always, it comes down to good basic engineering. I will admit, the result was far from practical for most users. The major part of this unique contraption was driver choice.
The 18" was a medium Xmax paper cone pro PA driver built for Wright Brothers Sound by Eminence. Happened to have 4 left over from a big pro sound project. It was intended as a high output mid woofer for vocals. Light cone, 2.5" 4 layer voice coil. 80 oz vented magnet. Low QTS. Very low FS (18 - 20 Hz) Cone profiled for max possible dispersion. So it was quite reasonable off axis up to about 750 Hz or so.
Enter a special dome tweeter... the venerable Scan-Speak D3806/820000. This wonderful creation has been in continuous production for over 4 decades!! Not very many drivers can qualify there! 1.5" treated silk dome with a HUGE (SD) motor with a LOT of copper. Can play nicely down to 1,200 Hz assuming a correct 2nd order Butterworth (electrical) 3rd order acoustic crossover.
The D3806 ran flat out. On a larger baffle with a bit of recess it is about 91 dbw. The 18 was in a heavy stuffed 5 cu. ft. sealed box that provided a QTC of about .65. Add a healthy baffle step correction circuit and a 2nd order Butterworth low pass (electrical) at the right frequency and you have a flat output from around 38 Hz up to just over 18Khz. Vocals were wonderful. Imaged quite well. Power response was quite nice. Big and ugly, but did sing. What I remember most about this design was how effortless it was. Kind of like a BIG OB. Know it really surprised a lot of people. OK, I'm done!
Just for fun... You can build a surprisingly competent 18" two way suitable for domestic use using an 18" and dome tweeter. Know eyes are rolling... but it has been done. As a demo - think piece, I designed such a crazy thing for a DIY get together in the S.F. CA area sometime around 2000 or so. I named the thing "The Jokes".
As always, it comes down to good basic engineering. I will admit, the result was far from practical for most users. The major part of this unique contraption was driver choice.
The 18" was a medium Xmax paper cone pro PA driver built for Wright Brothers Sound by Eminence. Happened to have 4 left over from a big pro sound project. It was intended as a high output mid woofer for vocals. Light cone, 2.5" 4 layer voice coil. 80 oz vented magnet. Low QTS. Very low FS (18 - 20 Hz) Cone profiled for max possible dispersion. So it was quite reasonable off axis up to about 750 Hz or so.
Enter a special dome tweeter... the venerable Scan-Speak D3806/820000. This wonderful creation has been in continuous production for over 4 decades!! Not very many drivers can qualify there! 1.5" treated silk dome with a HUGE (SD) motor with a LOT of copper. Can play nicely down to 1,200 Hz assuming a correct 2nd order Butterworth (electrical) 3rd order acoustic crossover.
The D3806 ran flat out. On a larger baffle with a bit of recess it is about 91 dbw. The 18 was in a heavy stuffed 5 cu. ft. sealed box that provided a QTC of about .65. Add a healthy baffle step correction circuit and a 2nd order Butterworth low pass (electrical) at the right frequency and you have a flat output from around 38 Hz up to just over 18Khz. Vocals were wonderful. Imaged quite well. Power response was quite nice. Big and ugly, but did sing. What I remember most about this design was how effortless it was. Kind of like a BIG OB. Know it really surprised a lot of people. OK, I'm done!
Thanks for the reply John! Those sound awesome. I wish I could hear all the mad creations out there. Especially many of yours.
I am really having trouble trying to decide on how to go with my project. I want to use large drivers in a 3 way, and am not sure how to decide which drivers to use. It's tough.
I am really having trouble trying to decide on how to go with my project. I want to use large drivers in a 3 way, and am not sure how to decide which drivers to use. It's tough.
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