T-Line for Dayton Ref 8" (RS225) - diyAudio
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Old 19th January 2005, 06:20 AM   #1
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Default T-Line for Dayton Ref 8" (RS225)

I just started doing the initial designs for a bass TL box for the dayton 8". This will be matched with a CSS WR125 for a mid and an Aurum Cantus G2si for treble. The G2's and the WR125's should be at my doorstep any day now, the Daytons haven't been ordered yet, just have to stop being lazy. I haven't worked out crossover points yet, so I'm not worried too much about that. Likely the mid crossover will be around 250hz, and the entire system will be actively crossed.

My question doesn't really have to do with the Dayton specifically I suppose, but more about mounting. Is it too much of a compromise to mount the midbass at the bottom of the enclosure, near the ground? I would like for the line to have a single bend and exit at the bottom in the rear. I suppose I could put two turns in and mount it at the top, but I just don't know how long the line is going to be. I'm planning on a tapered line so it should keep length to a minimum.

Also on a side note, I can't seem to find and appropriate Sd measurement for the Dayton driver. Where can I find this.

So anyways, I'm probably just looking for design tips in general as I go through this. This is my first T-line box that I've designed so I'm trying to get everything just right. I also can't seem to find a copy of Mathcad that I can use. If someone wants to plug in the Dayton to the MJK sheets and lemme know what it comes up with, I would be eternally greatful.

Thanks very much

-Steve
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Old 19th January 2005, 05:25 PM   #2
GM is offline GM  United States
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>My question doesn't really have to do with the Dayton specifically I suppose, but more about mounting. Is it too much of a compromise to mount the midbass at the bottom of the enclosure, near the ground?
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Depends on high up the XO point/slope is, ergo how close the mid must be for good summation, ergo where is it in relation to the listening position vertically. That, or how much slope the baffle has.
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>Also on a side note, I can't seem to find and appropriate Sd measurement for the Dayton driver. Where can I find this.
====
Look at the measured specs, it lists the effective diameter, which you can calc it from using (d^2*pi)/4.
====
>So anyways, I'm probably just looking for design tips in general as I go through this. This is my first T-line box that I've designed so I'm trying to get everything just right. I also can't seem to find a copy of Mathcad that I can use.
====
??? Do you mean you have an Apple?
====
>If someone wants to plug in the Dayton to the MJK sheets and lemme know what it comes up with, I would be eternally greatful.
====
Traditional, ML-TL, or somewhere in-between?

BTW, folks tend to be more helpful if provided with enough info that they don't have to search for it, so posting any pertinent links, etc. is encouraged.

GM
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Old 19th January 2005, 06:04 PM   #3
cjd is offline cjd  United States
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What kind of bass response do you want? I messed with modeling a TL for a pair of RS225's and it got pretty big pretty fast as I moved the low frequency target down (22Hz is realistic if you have the room IIRC). Also, I believe that the drivers weren't mounted at the end of the line, but partway along it. Which would mean they could be up off the floor some.

I'm not sure where you can get the free version of MathCad any more - I know the link on MJKing's website doesn't work any more.

Also, remember to remove the area of the phase plug from the cone area when calculating based on the diameter.

C
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Old 19th January 2005, 06:35 PM   #4
cjd is offline cjd  United States
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Alright. I had a few minutes and Mathcad already open and the RS225 specs handy...

Single RS225.

Line length 84-88 inches long.

Driver can be placed as far as 24" from the line end without significant ill effects, though it starts to introduce broader ripples at 200Hz up.

Line taper at 5Sd to 1.5Sd (with 1.55Sd being the open end) looks good. Err on the side of a little big. 7:2 looks great still, but a smidge under 5:1.5 starts to raise F3 quickly.

Stuff with 3-4oz per cubic foot (or, .2lb/ft^3)

This gives you an F3 at 30Hz.

Lengthen the line up to 120 inches, still 5:1.5 up to 7:2 taper ratio, same stuffing ratio. This gives you an F6 at 24Hz which, in-room, will often end up being flat.

Need smaller? Drop the taper ratio, shorten the line, and add stuffing. For example, 2.5:.75 taper, .5lb/ft^3, 66" length = F6 at 42Hz. You also need to move the driver closer to the closed end to reduce higher frequency ripple. 2.5:.71 taper stuffed .2lb/ft^3 at 84" gives you an F3 at 40Hz, F6 at 33Hz.

It's all about picking your compromises.

Have fun! And let us know how it turns out.

C
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Old 19th January 2005, 07:04 PM   #5
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I knew you guys would come through. Thanks so much for your effort so far.

On the mathcad note. I have a PC, and a linux box, but I can't find a demo for anything. I'm sure we have it on Campus somewhere here at OSU, I just have to find it.

I'm thinking that 90" or so would be about a max for the line. I figure that gives me a 50" tall box. That means my mid would be mounted about 55" high, which is getting pretty tall.

While I'd love a pair of speakers that would be give me good response down to 20hz in room, I don't need it. I'll give up ultra low response for a smaller cabinet. My living room is sloped ceiling with 8 foot on one side and 20ft on the other. I'm thinking that a nice straight line in one corner with a 15" driver will fill in the bottom octaves nicely. So I'm going to look into something with an f6 in the high 30's.

I'm at school right now and late for Microcontroller system design, but when I get home I'll draw up an initial box design and see what everybody thinks.

Thanks again
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Old 19th January 2005, 07:18 PM   #6
GM is offline GM  United States
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>I'm not sure where you can get the free version of MathCad any more - I know the link on MJKing's website doesn't work any more.
====
Oh really?! It just worked for me.
====
>Also, remember to remove the area of the phase plug from the cone area when calculating based on the diameter.
====
Technically correct, but has no real bearing on a cab's design, assuming you use CSA instead of Sd to define SO/SL. Even then, a little too big is better than too small. Still, I didn't know it had one or would have said the same thing.

GM
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Old 19th January 2005, 08:05 PM   #7
cjd is offline cjd  United States
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dunderhead:

I would go with an 84" line and the 2.5 to .75 Sd taper, driver ~18" from the closed (large) end, stuffed with about a quarter pound per cubic foot. That's actually a very reasonable box size. If you build an angled division in the box from front to back to separate the TL from the mid enclosure (so the mid/tweet gets mounted into a triangular shaped box, looking at it from the side) you can get the tweeter in at ~40" off the floor or so even, I think.

GM: Haven't tried that link in a couple weeks. It wasn't working last I tried it. Guess I should've checked. And Sd/Bl relate in such a way that it can tweak the design some. Not hyper critical in this case, but not unimportant either. Try adding 5-10cm to Sd on a model. It's interesting. In the case of M King's stuff, since it uses Sd to base the rest of the numbers it's not unimportant either I think. Probably not much more than interesting once all is said and done.

FWIW, I did this modeling with M. King's "Offset Driver" worksheet. Fine tune with the "Sections" worksheet.

C
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Old 20th January 2005, 01:15 AM   #8
Greg B is offline Greg B  United States
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I don't really have a suggestion on the TL, but here are the specs from PE:

Dayton RS225s

Specifications: *Power handling: 80 watts RMS/120 watts max *VCdia: 1.5" *Le: 1.0 mH *Znom: 8 ohms *Re: 6.4 ohms *Frequency range: 27-2,000 Hz *Fs: 27 Hz *SPL: 88.1 dB 2.83V/1m *Vas: 2.75 cu. ft. *Qms: 1.60 *Qes: .47 *Qts: .37 *Xmax: 7 mm *Dimensions: A: 8-3/4", B: 7-3/8", C: 4".

PARAMETERS

Re 6.40 [ ]
Fs 26.35 [Hz]
F1 14.13 [Hz]
F2 47.32 [Hz]
Zm 26.01 []
D 162.00 [mm]
Qms 1.55
Qes 0.50
Qts 0.38
Bl 7.60 [N/A]
L1K 0.79 [mH]
L10K 0.26 [mH]
Ms 27.52 [g]
Vas 78.64 [l]
dBSpl 87.48 [dB]
Cms 1.33 [mm/N]
Ma 84.00 [g]
FsMa 13.09 [Hz]

GB
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Old 21st January 2005, 06:38 AM   #9
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So I thought I would bump this back up to the top with a couple more questions. I'm going to finalize some things this weekend, and I want all the help I can get.

My current crossover design seems to go like this.

RS225 up to ~250Hz

WR125 from 250hz to ~6khz

AC G2si from 6kHz up

All slopes will be 24db/ octave initially.

Anybody see anything fundamentally wrong with this?

Each driver will be amped with channel from a few Panasonic Equibit receivers I've got laying around, and those will receive a signal from kx project drivers, and later from BruteFIR.

I'm going to go ahead with an 85" line. I like to the way it fits with the alignment tables, and what has been said in this thread. It is tempting to figure out how to put together a 120" line though.

Thanks much.

-Steve
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Old 21st January 2005, 07:09 AM   #10
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Also, on a separate note, are we using 162mm as effective diameter or 7 3/8"?
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