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Multi-Way Conventional loudspeakers with crossovers

Which 15 or 18 ınch woofer- best for open baffle
Which 15 or 18 ınch woofer- best for open baffle
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Old 10th November 2017, 12:19 PM   #61
Kjeldsen is offline Kjeldsen  Denmark
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Very often the major problem with cheap drivers in OB, is that they make to much mechanical noise, when they move a lot. If you go for 8 woofers, you will already pay an amount, where you can get decent 15" and half decent 18" woofers.

Right now I have 8 pcs 10" OEM VIfa woofers. They do a good job, but make mechanical noise when pushed to the limits. My new project is with very good 15" woofers (Gladen RS15 FA). And they have no noise, no matter how much the cone moves.
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Old 10th November 2017, 12:36 PM   #62
ErikdeBest is offline ErikdeBest  Switzerland
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Which 15 or 18 ınch woofer- best for open baffle
Hi! I have 6 WS25E per side and they are doing well for moderate SPL levels. Also no problems with trapped air or other noise. But for a future project i am going for the W200, an 8" with somewhat higher xmax.
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Old 10th November 2017, 02:38 PM   #63
zmyrna is offline zmyrna  United Kingdom
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IMO the best price/performance for OB bass:
one per side decent quality midQ 15-18" high-passed 60hz
+ ripol nearfield sub with similar 15-18"s (or IB, or sealed corner sub)
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Old 10th November 2017, 02:59 PM   #64
CharlieLaub is offline CharlieLaub  United States
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FYI: I just got a flyer from Parts Express. Their PA465 18" "subwoofer" is on sale for $155. This would be a pretty good driver for use in an open baffle (or my favorite, the H-frame). It doesn't have any fancy construction or motor, but should fit the bill nicely.
Dayton Audio PA465S-8 18" Pro Subwoofer 4" VC 8 Ohm

Product Specifications:

Nominal Diameter: 18"
Power Handling (RMS): 1,000 Watts
Impedance: 8 ohms
Sensitivity: 93.9 dB 2.83V/1m
Voice Coil Diameter: 4"

Thiele-Small Parameters:

Resonant Frequency (Fs): 32.3 Hz
DC Resistance (Re): 5.4 ohms
Voice Coil Inductance (Le): 4.98 mH
Mechanical Q (Qms): 6.92
Electromagnetic Q (Qes): 0.62
Total Q (Qts):0.57
Compliance Equivalent Volume (Vas): 6.81 ft.³
Mechanical Compliance of Suspension (Cms): 0.09 mm/N
BL Product (BL): 21.9 Tm
Diaphragm Mass Inc. Airload (Mms): 271g
Maximum Linear Excursion (Xmax): 10 mm
Surface Area of Cone (Sd): 1,225 cm²
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Old 10th November 2017, 03:10 PM   #65
Jim Griffin is offline Jim Griffin  United States
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sismik11 raised this question in Post #60

"These speakers have very small magnets. Normally I consider this a problem, but many seem to apply that this is not the case when dealing with open baffle speaker design. Can anyone explain why this is so?"

A smaller magnet structure is an advantage for a woofer operated as a dipole. You will typically find that woofers with more powerful neodymium magnets have a significantly smaller (and lighter) magnet structure. Also reduced basket webbing improves air flow from the rear of the driver. Hence, the emitted sound from the forward and rear directions of the woofer is more symmetrical thus better emulates a true dipole.
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Old 10th November 2017, 03:31 PM   #66
picowallspeaker is offline picowallspeaker  Italy
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Quote:
Originally Posted by sismik11 View Post
Hi.

One more question. These speakers have very small magnets. Normally I consider this a problem, but many seem to apply that this is not the case when dealing with open baffle speaker design. Can anyone explain why this is so?
Mr Griffin had explained in the previous post from yours.
It's the difference of monopole and dipole. And velocity vs pressure.
Talking about SPL and how it is related to cone movement.
So the pressure is related to velocity and resistance of air, or better, impedance Z. p=Z * v
As you have a "low coupling" from membrane to fluid (air ) in OB since the wavelenghts involved are much bigger than the phisical elements.

The solution is to send more voltage to the speaker and this results in higher excursion. But for a double lenght in excursion the price rises a lot, I see.
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Old 10th November 2017, 05:20 PM   #67
zmyrna is offline zmyrna  United Kingdom
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Eminence have some cast frame 18"s for similar price
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Old 10th November 2017, 09:15 PM   #68
Scott L is offline Scott L  United States
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Which 15 or 18 &#305;nch woofer- best for open baffle
Quote:
Originally Posted by Jim Griffin View Post
I'm the Cookeville dude that Scott means. Scott has an open invitation to visit.

My implementation is more of a balanced approach--not the absolute deepest bass but a very good balance of bass/mid/treble. While in some ways relatively modest system the results are very musical.

It is an open baffle midrange with PHL Audio 1240s in an MTM and Aurum Cantus G2 tweeters. Eminence 3015LF Neo Kappitalite woofers in H-frame mounts handle the lows. The 3-way crossovers are via a DEQX PDC2.6 HD at 175 Hz and 2500Hz. I'm using 96 dB/octave slopes.

http://www.diyaudio.com/forums/attac...ctures-001.jpg

Open baffle or dipole bass works on sound velocity vs. sound pressure (monopole) effects. The tradeoff you have to appreciate is superior attack and decay of dipolar bass at the expense of chest thumping--often muddy sounding--bass heard from monopole speakers.
Four of us went to visit Jim at his house during the following month of July (I believe, since it's been over 4 years ago), and were treated with the greatest of hospitably from Jim and his wife.
After finishing a fabulous lunch, we auditioned 5 or 6 different systems. I liked the line source arrays he had downstairs, and the triple (almost) full range ribbons he had upstairs, the best.
In return, I have invited Jim to come listen to my system, which utilizes the much maligned mono-pole bass system, but at this point he refuses to communicate with me, entirely. Strange, to say the least.
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Old 11th November 2017, 02:19 AM   #69
Jim Griffin is offline Jim Griffin  United States
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Scott L,

I'm not ignoring you but I have been busy today so I did not have a chance to reply.
Of course I would love to hear your system. We can work out a plan for a listening session.

You will have to visit me again to hear my later (2015 version) version of an open backed system. I'm working on a Constant Beamwidth Transducer line array/system which should be finished this winter. The CBT system will have a monopole bass setup that you will like but it will not rival your infinite baffle bass setup.

Jim

Last edited by Jim Griffin; 11th November 2017 at 02:27 AM.
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Old 11th November 2017, 10:07 AM   #70
Scott L is offline Scott L  United States
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Which 15 or 18 &#305;nch woofer- best for open baffle
Quote:
Originally Posted by sismik11 View Post
Hi.
Questions for an old but still very relevant thread.

I too am playing around with OB speakers and have come across the Visaton ws 25 e WS 25 E - 8 Ohm .

This is a very cheap 10” driver with high Qts: 1,43 and fairly low fs: 34 Hz but low sensitivity: 88 dB. With a price tag of under 35 EUR it would be interesting to try 4 or maybe 8 per side to compensate for the low sensitivity.

What are your thoughts or even better experiences with this driver? The only thing I can find about these drivers are from Visatons own ORGUE speakers.

One more question. These speakers have very small magnets. Normally I consider this a problem, but many seem to apply that this is not the case when dealing with open baffle speaker design. Can anyone explain why this is so?
The 88 db sens. rating on this driver, is actually a bit mis-leading. It refers to the average mid-band sensitivity which should not be substituted for a sensitivity rating for bass, which appears to be 80 db +/- 1 db, from 30Hz up to 280Hz. Sensitivity and relative system efficiency are often confused for one another. They are related, but certainly NOT the same thing. Ultimately, system efficiency depends upon the type/and/size of the enclosure. For an open-baffle (di-pole) bass attempt, some aspect of the design must be substituted for the lack of the enclosure. The exact conditions for the response sweep are not given, such that we can only assume it was done on an IEC baffle, and reveals the effect of the high Qts, as witnessed by the rise in response near it's low end, relative to what is typically shown for normal-Q-range drivers. This, along with a few other revealing specification indicators, does confirm you suspicion that this driver is a prime candidate for a di-pole bass configuration. Yes, probably best realized using multiple drivers, on a baffle at least as large as an IEC (65x53 inches). Also, if a woofer has to chuff and puff to produce bass, it's not being used in an ideal situation. Having stated that, I have no idea if the driver's construction techniques would be prone to producing mechanical noise, but again, if your woofers are flopping around in extreme fashion, then you have the wrong design.
About a year ago, I was invited to listen to the Linkwitz LX-521 speaker system. As far as it's bass production, all was fine as long as it was not asked to do something it simply could not do, and that was to play back Bella Fleck's flight of the Cosmic Hippo. I don't think they are made for that type of music, but more for small scale acoustics.
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