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Multi-Way Conventional loudspeakers with crossovers

Precision Devices 18" for bottom of 3 way?
Precision Devices 18" for bottom of 3 way?
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Old 1st February 2019, 04:53 PM   #1
mortron is offline mortron  Canada
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Default Precision Devices 18" for bottom of 3 way?

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?
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Old 4th February 2019, 12:16 AM   #2
kipman725 is offline kipman725  United Kingdom
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Its apparently discontinued. I have used PD woofers in the past, they are well built. They are a UK company though, I would have thought other brands would be cheaper in North America?
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Old 4th February 2019, 04:24 AM   #3
WaVeInFoRm is offline WaVeInFoRm
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there is a simuler trowls design.
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Old 4th February 2019, 12:35 PM   #4
mortron is offline mortron  Canada
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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.
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Old 4th February 2019, 12:57 PM   #5
EarlK is offline EarlK  Canada
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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"

Last edited by EarlK; 4th February 2019 at 01:01 PM.
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Old 4th February 2019, 02:07 PM   #6
chris661 is offline chris661  United Kingdom
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Looks like a good driver. I haven't used them, but I know people that swear by them.


Chris
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Old 4th February 2019, 02:13 PM   #7
kipman725 is offline kipman725  United Kingdom
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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.
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Old 4th February 2019, 10:07 PM   #8
mortron is offline mortron  Canada
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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?
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Old 4th February 2019, 10:26 PM   #9
EarlK is offline EarlK  Canada
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Quote:
Originally Posted by mortron View Post
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?
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 ).

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Old 5th February 2019, 02:48 PM   #10
etalon90 is offline etalon90  Canada
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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?

Last edited by etalon90; 5th February 2019 at 02:51 PM.
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