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MultiWay Conventional loudspeakers with crossovers 

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22nd November 2010, 02:46 PM  #101 
diyAudio Member
Join Date: Mar 2008

The new thread about trying to simulate a bassreflex boss using LTspiceIV is here :
Marshall Leach ventedbox loudspeaker Spice model (AES 1991) 
29th November 2010, 04:58 AM  #102 
diyAudio Member
Join Date: Sep 2005

I've been amusing myself with manual calculations to try to find a suitable bass driver for a bass reflex system, with a f3 of 30 Hz. I've found a few that gives satisfying Vb and vent tuning values, but when I come to calculations of the vent diameter and length, my luck is out. I've been trying with dual 10" and 12" drivers.
I get results in the 56" for the diameter, and at least around 30" for length. Can it be due to that I use double the Vd value, as I do for Vas when calculating Vb value for the box? I've used the following formulas, given in Basta! + Dickason's formulas for a SBB4 in LDC. (For vents, I've tried those in LDC and some others, result the same): 1. Öhman Vb = Vas/1.1 x (Qts/0,40)^3/1+0,4xViso fp = fs x (0,42/Qts) 2. Keele Vb = Vas x 15 x Qts^2,87 / 1 + 0,4 x Viso fp = fs x 0,42 x Qts^0.9 3. Margolis/Small Vb = Vas x 20 x Qts^3,3 / 1 + 0,4 x Viso fp = fs x 0,42 x Qts^0,96 I've used a Viso value of 20% (Viso = amount of lining material in comparison with total volume) Suggestions for f3 calculations for the formulas above? Suggestions for vent calculations? Suggestions for two 10" or 12" that might give a f3 around 30 Hz in a box with a Vb of at the most around 100 liter? 
29th November 2010, 10:13 AM  #103 
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Join Date: Mar 2008

Best choice would be Monacor SPH200KE, two drivers inside a 85 litre box.
Second choice would be Monacor SP212, one driver inside a 85 litre box. Big cone doesn't mean deep bass. 
29th November 2010, 11:02 AM  #104  
diyAudio Member

Quote:
Suggestions would the SEAS L22RNX/P (bass reflex), W26FX01 (sealed), or Peerless XXLS subwoofers (sealed) see links below. THE ART OF SOUND PERFECTION BY SEAS  H125208 L22RNX/P THE ART OF SOUND PERFECTION BY SEAS  E002608S W26FX001
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29th November 2010, 08:51 PM  #105 
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Join Date: Mar 2008

Comparing some bassreflex arrangements.
Monacor SPH210 is ruled out because of 50 Hz 3dB point. Monacor SPH225C is ruled out because of 51 Hz 3dB point. Seas W26FX001 E0026 is ruled out because of Box volume 60.7 litre. Monacor SPH200KE gives a 29 Hz 3dB point in a 25.8 litre box. Amazing for such a small box. Problem may be the port lenght, 182mm long with 50mm diameter. Seas L22RNXP H1252 gives a 31 Hz 3dB in a 36.5 litre box. Port is compact : 119mm long with 50mm diameter. Monacor SPH212 gives a 28 Hz 3dB in a 48.6 litre box. Port is very compact : 98mm long with 50mm diameter. Last edited by steph_tsf; 29th November 2010 at 09:14 PM. 
29th November 2010, 09:32 PM  #106 
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Join Date: Nov 2003
Location: Brighton UK

Hi,
Thought I'd do a quick check of one of the above, the SPH200KE. I don't get the same numbers. 26L sealed is around Qbox = 0.67, I get around 40Hz for 3dB, 30Hz needs a bigger box. Qts = 0.38, Fs = 28Hz, Vas = 54L, not checked the driver parameters. rgds, sreten. 
30th November 2010, 12:28 AM  #107 
diyAudio Member
Join Date: Mar 2008

Ooops ! I agree there is a problem in my post #103 & #105. I'll redo the calculations checking with WinISD beta. In the meantime please ignore post #103 & #105. Please apology.

30th November 2010, 06:14 AM  #108  
diyAudio Member

Quote:
You should maybe look at F3 and F10 numbers to determine which woofer system works best in your room. We get some Wavecor woofers in India. I dont know if you get them where you are but they perform well in small boxes with passive radators. Yo can check out their 10" and 12" woofers here. http://www.wavecor.com/
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...still looking for the holy grail. Last edited by navin; 30th November 2010 at 06:27 AM. 

30th November 2010, 05:56 PM  #109  
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Join Date: Sep 2005

No, not necessarily, but it does help moving air when going deeper.
Quote:
Quote:
We do have Wavecor in my area, and I've checked them up earlier, but I will do it again, and I'm not used to radiator solutions at all, never looked at that solution at all. If someone could just outline the major difference between reflex and radiator, I would be much obliged. Small box is not that important, if by small you mean something less than around 100 liter in total for the woofer section. Smaller would be nice (WAF), but I think I can handle up to 100 lit. 

1st December 2010, 05:00 AM  #110  
diyAudio Member

Quote:
There is no "RIGHT" solution. The roomspeaker interaction is what determines the response of a loudpspeaker. Becuase bass has longer wavelenghts it's interaction with the room is more prominent. Dont aim for flat response (+/3 db as advertised by many manufactuers in their catalogs). The room can add +/ 10db with ease so all those flat response curves are really not worth the paper they are written on. Which is why I discussed F10 numbers earlier. I have lived on 3 continents (4 countries) and a variety of dwellings from a studio apartment in NYC (with flimsy sheet rock walls) to a large (wooden) house in the boonies with vaulted ceilings to a brick and concrete apartment and once even had a square room (exactly 16ft square). Each dwelling offered it's own challenges. As DIYers I believe it is our abilities to adjust for these "challenges" (as well as adjusting the sound to our ears) that makes DIY such a pleasurable and fulfilling pastime/hobby. Passive radiators have their uses. If port lengths are too long a PR is often a viable option. Another option is that one can avail of Milo Nestorovic's concept of using cones of 2 different sizes (say a 10" woofer mated to a 12" PR). Adjusting the mass of the PR is also easier than adjusting a port length so in that way a PR is easier to tune to a room that a bass reflex speaker. However a PR has a fixed (static mass) while th mass of air inside a bass reflex port is not nesscarily so and this can pose it's own problems (transient response is not as good as a (SBB4 or even QB3) ported box). Wavecor's website has sample boxes and their transient response curves for your reference. see link below for more. Audio Innovation  by Dan Marx www.danmarx.org Before starting out I would advise you to try out a few of your friends' speaker systems in your room and at least determine which systems sound best. From the late 70s to today I must have "gone through" over a dozen speaker systems (from Philips, KEF, Volt/Rogers, JBL, JBL/UREI, Gold Sound, Vifa, Focal, Dynaudio, Morel/Focal, Peerless/Dynaudio, Focal/Morel/JBL, ScanSpeak, Audio Concepts, etc...) and each worked within it's own limiations and enviroment. I have also lived with friends' speakers from Klipsch, Polk, Fried, Vanderstee, Theil, Snell, AR, Infinity, etc.. and each time realised that DIY is a much better option even if you dont save any money by going DIY. Good photographers have a clear idea of the picture they are going to take before even raising the camera to their eye. Similarly you need to determine what you want your system to sound like before shortlisting the drivers. Hope this helps.
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...still looking for the holy grail. Last edited by navin; 1st December 2010 at 05:13 AM. 

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