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Old 2nd September 2007, 08:30 PM   #1
Dr_EM is offline Dr_EM  United Kingdom
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Default Good for transmission line?

I have been looking at woofers for a 3 way system and am quite keen on the SPH-275C from Monacor. I am mainly attracted to it because it seems to have very optimal parameters for a TL design (and after building a TL sub I have decided I like the sound they give ).

http://www.monacor.com/en/produktsei...pr=EN&typ=full

In a 3 way I would be intending to cross it low at around 200-250Hz, so it will mainly be active in subwoofer region (hence why it's posted here).

Really I am wondering just how well it would work (frequency response) but don't have the design software. Also the size it would need to be. My sub with 2x6" is quite large compared to the drivers so one (or a pair as it would be) with 10" will presumably be larger. VAS is higher and resonance is lower so presumably a larger area and longer line result. Anyone thoughts?
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Old 2nd September 2007, 09:04 PM   #2
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Vas is a factor to determine line length.

You need to get busy with Martin J Kings worksheets.
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Old 2nd September 2007, 09:20 PM   #3
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Quote:
Originally posted by richie00boy
Vas is a factor to determine line length.
It is more like Fs is the prime factor in line length, and Vas the total box volume which given you have fixed the length means Vas is related to cross-section.

dave
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Old 2nd September 2007, 09:38 PM   #4
Dr_EM is offline Dr_EM  United Kingdom
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Yes, I hear MJK is where it's at with transmission lines. Are they literally "worksheets" though? What I've read on his site, being honest, is mostly above me. It goes into great depth. Does he have a program to model in? Such as you put in driver parameters and various line models and it shows frequency response, excursion etc? Something interactive like that. Scottmoose came up with a frequency response graph for the Morel woofers in a TL and I think it was using MJKs "worksheets".

Vas is 100L and this looks relatively low for a 10" driver (I think). Would it end up as a wardrobe ?
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Old 2nd September 2007, 11:00 PM   #5
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I missed the "not" out!

As far as I know you just bung parameters etc into the spreadsheet.
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Old 2nd September 2007, 11:52 PM   #6
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Quote:
Originally posted by richie00boy
As far as I know you just bung parameters etc into the spreadsheet. [/B]
Not really a spreadsheet, but yes, you bung in the speaker's T/S and then you play with various line configurations.

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Old 2nd September 2007, 11:52 PM   #7
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Default Re: Good for transmission line?

Quote:
Originally posted by Dr.EM
...and am quite keen on the SPH-275C from Monacor.
Anyone thoughts?

Hi,
The Qts of this driver is on the low side for TL. Should be looking at one with a higher Qts - .40 and up will give better results.
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Old 3rd September 2007, 12:18 AM   #8
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A good choice in a 10 inch would be the Peerless S263SWR3908.
http://www.tymphany.com/datasheet/pdf/pl/830668.pdf

It has a low Fs (33), good response up tp 1K and a Qts of .51. Also pretty cheap - $70.00 here.
Make an excellent TL sub.
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Old 3rd September 2007, 12:37 AM   #9
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Well I havent heard that you cant use low Qts drivers for a TL - Generally speaking high Qts drivers (.4+) will only work in sealed enclosures, now considering a TL works more like a vented box then it would make sense that low Qts drivers are better suited (0.3-0.4). I have had a lot of success using just such drivers.
I have always designed TLs (actually quarter wave) using the basic 1/4 wavelength of Fs (assuming tuning ratio of 1) & a taper of 1.25 to 1, using the drivers Sd to calc cross sectional area.
I would suggest keeping the folds very simple & minimal, the best sub I built (which I currently use) has a single 'fold' - this alos meant it was very easy to tune with damping.
The Monacor driver you have chosen looks fine + I have always liked carbon fibre for bass duties.
Andrew.
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Old 3rd September 2007, 01:52 AM   #10
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Quote:
Originally posted by Ap
Well I havent heard that you cant use low Qts drivers for a TL - Generally speaking high Qts drivers (.4+) will only work in sealed enclosures

Oops! Got it backwards, sorry. Brain is not in gear.

Dr.EM, please disregard my previous posts.
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