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Multi-Way Conventional loudspeakers with crossovers

Seas W22XL in Transmission Line
Seas W22XL in Transmission Line
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Old 30th July 2018, 11:21 AM   #1
LJT is offline LJT  Norway
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Default Seas W22XL in Transmission Line

Has anyone tried or simulated the Seas W22EX in a transmission line?
From running the numbers thru the alignment tables in my old copy of Loudspeaker Design Cookbook I believe the element to be suited, however I believe there are more accurate modelling tools available.

I am contemplating a makeover of my old Seas Trym speakers from reflex to TL so I guess baffle width is fixed. http://seas.no/images/stories/diykit...t/trym_cab.pdf
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Old 30th July 2018, 01:41 PM   #2
pkitt is offline pkitt  United States
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Assuming Seas' published T/S values for this driver are reasonably representative, I think it would work pretty well in TL, either tapered or mass-loaded (ML-TL). A 10:1 tapered TL would need a line length of 70-80 inches in order for its 1/4-wavelength resonant frequency to optimally tune the system for this driver; but it might be necessary to use a shorter line with a larger taper ratio to achieve optimum results. Any tapered line that would work well could be converted to an ML-TL of the same length and volume with equal or slightly better performance in specific areas.
Paul

Quote:
Originally Posted by LJT View Post
Has anyone tried or simulated the Seas W22EX in a transmission line?
From running the numbers thru the alignment tables in my old copy of Loudspeaker Design Cookbook I believe the element to be suited, however I believe there are more accurate modelling tools available.

I am contemplating a makeover of my old Seas Trym speakers from reflex to TL so I guess baffle width is fixed. http://seas.no/images/stories/diykit...t/trym_cab.pdf
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Old 30th July 2018, 02:24 PM   #3
pkitt is offline pkitt  United States
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Default Modeling results

I modeled a couple of 10:1 tapered TLs that differed only in the volume in the lines. Each line was tuned to ~25 Hz. I've attached the two resulting predicted bass responses.
Paul
Attached Files
File Type: doc Tapered TLs for Seas W22EX.doc (40.0 KB, 75 views)
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Old 30th July 2018, 02:56 PM   #4
LJT is offline LJT  Norway
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Thanks, so with the smaler line I'm looking at an internal volume of approximately 60 liters.
What software tool is it that you are using for the modelling?
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Old 30th July 2018, 03:25 PM   #5
ernperkins is offline ernperkins  United States
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I tried a MLTL using Martin King's Mathcad worksheets. I made these assumptions:

- Use the original width, depth and material dimensions. This gives an internal width and depth of 9” and 11.5” respectively.

- The spacing of the drivers remains the same including the distance of the tweeter from the top. This also fixes the distance of the woofer from the top, one of the MLTL variables.

- The tweeter height will be 35” from floor; this fixes the internal height to about 38” (37.9”).

With those assumptions the gross volume would be 64 L and I subtracted 0.5L for the speaker and bracing. I ended up with 0.5 lb/ft3 stuffing density in the top 24". The port, 3” diameter and 8” long, is placed 5” above the internal bottom.

Here’s what I got with a 18 W input signal (anechoic response, no room or boundary effects) for SPL, excursion and port velocity. Note that the excursion is RMS, not peak or peak to peak.
Attached Images
File Type: jpg W22EX SPL.JPG (35.9 KB, 318 views)
File Type: jpg W22EX Excursion.JPG (43.1 KB, 319 views)
File Type: jpg W22EX Port Velocity.JPG (34.2 KB, 315 views)
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Old 30th July 2018, 04:36 PM   #6
pkitt is offline pkitt  United States
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I used Martin King's software "ML-TL Corner", and I can model tapered TLs or ML-TLs with it quickly. If tapered and folded, though, Martin's "Sections" software is necessary to correctly model the line around the fold.
Paul

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Originally Posted by LJT View Post
Thanks, so with the smaler line I'm looking at an internal volume of approximately 60 liters.
What software tool is it that you are using for the modelling?
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Old 30th July 2018, 10:35 PM   #7
LJT is offline LJT  Norway
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Quote:
Originally Posted by pkitt View Post
I used Martin King's software "ML-TL Corner
I tried download from quarter-wave.com only it is blocked by username and password. Any idea how I can go about contacting Mr. King for purchasing a license?

Are there any sonic differences to the conventional TL and the ported MLTL solutions as proposed by ernperkins?
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Old 31st July 2018, 02:10 PM   #8
pkitt is offline pkitt  United States
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Very near the top of the home page for Quarter-Wave there's a link to Martin's Yahoo group primarily devoted to TLs. If you become a member of that group you can get access to Martin's software.

For truly equivalent tapered and mass-loaded TLs, there will be no sonic differences. Each has their pros and cons; with the same line volumes, the ML-TL will have a bit lower f3, whereas the tapered TL will have a much lower air velocity in its terminus than in the port of the ML-TL. Also, the overall response of the ML-TL will be usually be smoother above 300 Hz so than that of the tapered TL.

The ML-TL that ernperkins modeled is the simplest form of an ML-TL. The internal height of the cabinet is the line's length and while its 1/4-wavelength resonant frequency contributes some to the overall system tuning, most of the tuning comes from the port acting on the line's volume. There's nothing at all wrong with that design and I've built several similar designs, but I prefer a longer line where its 1/4-wave resonance plays a bigger part in the tuning.
Paul

Quote:
Originally Posted by LJT View Post
I tried download from quarter-wave.com only it is blocked by username and password. Any idea how I can go about contacting Mr. King for purchasing a license?

Are there any sonic differences to the conventional TL and the ported MLTL solutions as proposed by ernperkins?
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Old 1st August 2018, 11:41 PM   #9
LJT is offline LJT  Norway
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So, I went shopping wood for the new cabinets today.
Since this is also a case study before my next set of DIY speakers, I decided to go with the conventional line.
For my next project MLTL is an option due to cabinet shape.

It should be noted that I have decided to deviate somewhat from the original Trym layout. I believe the Trym is an early design and I will eventually attempt an XO redesign. This change of layout has the effect of putting the bass element in a slightly different location compared to pkitt's modelling. I don't think this is as critical for a conventional TL as it is for an MLTL?

Before I start cutting I hope someone verify my understanding of pkitt's modelling.
Attached images show two alternative boxes. I believe box #1 should be very close that proposed by pkitt. Alternative #2 has a slightly longer line, but if necessary, I can shorten it further by lifting the start of the line by making a false bottom.
So my questions before I make final decition towards alternative 1 or 2 are:
- How critical is the line lengths
- How important is the radius fillets, and what do you propose to make them from?
- Do the start of the line have to be level, or is it OK if it is slanted (I.e - do I have to make the cavity for the XO in alternative#2 or is it OK to simply attach the XO to the cabinet at the start of the line?
- Any other comment you may have
Attached Images
File Type: png Alternative-1.PNG (303.1 KB, 224 views)
File Type: png Alternative-2.PNG (675.6 KB, 223 views)
File Type: png Pipe taper.PNG (544.0 KB, 77 views)
File Type: png Thor slaying Trym.PNG (195.5 KB, 56 views)
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Old 1st August 2018, 11:50 PM   #10
phivates is offline phivates  United States
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Line #2 will make more bass. Some have added elevating spacers to adjust the low end response if too heavy.

Last edited by phivates; 1st August 2018 at 11:53 PM.
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