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Old 2nd February 2004, 12:59 PM   #1
Nuuk is offline Nuuk  United Kingdom
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Default Cost-effective bass extension from 65Hz

As you may have seen, I now have my Goodmans 201's in their new open baffles so I am turning my attention to the bottom end.

The plan was to get four 12 inch drivers and use them in a W baffle with an amp each and some EQ. Thinking about it again though, this seems an expensive way (for me anyway) to get bass from around 65Hz down to 40Hz (the realistic limit for this configuration according to SL).

An alternative is to go with a single driver on each channel a la NAO This means half the number of drivers and amps, leaving funds for a possible sub to get down even lower.

I think that my chosen driver, the Alpine SWE1250 would work in either system.

Or, how much quality would I loose by building an ELF system (perhaps one per side) to go up high enough to 'meet' the 201's at around 65Hz?

Does anybody have any comments on this issue to help me make a decision?
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Old 2nd February 2004, 01:29 PM   #2
Guss is offline Guss  Canada
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You don't need to reach fully 65hz because the rolloff of your speakers together with your sub will complete the spectrum...at a certain point...

The elf seems to emphasis the lowest end which you barely would hear and most of the records still miss that part exept maybe for techno and/or rap... Even if the thing is tweakable (he used the amp I think to get that response so far ) you should consider a something tuned say at 30hz where you can enjoy the 40-50 region...There is a lot of diy sub projects on the net actually, try seatching for what you want exactly, maybe there is one for you out there.
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Old 2nd February 2004, 02:18 PM   #3
Mats J is offline Mats J  United States
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I can't seem to find anything on the Alpine SWE1250. the closest I found was swe1241. Could you provide a link or something?
Thanks,
Mats
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Old 2nd February 2004, 02:26 PM   #4
Wizard of Kelts
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Nuuk:

Is there any good reason a ported, sealed, or Transmission Line enclosure cannot meet your needs?



Mats:

Here is the link to Alpine USA. I clicked "Products" and the thing took so long to load, (I use dialup), that I said the heck to with it.

If Nuuk or anyone has the Thiele-Small specs for the Alpine SWE 1250, please post.
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Old 2nd February 2004, 03:07 PM   #5
Nuuk is offline Nuuk  United Kingdom
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I wanted to avoid a boxed sub if possible and use dipole as people rave about the better quality of the dipole, and it should be less of a problem in my room which is 4 by 3 metres (12 feet by 14) And of course, the main system is dipole.

It seems that Alpine driver is the SWE1241 (not sure how I got 1250 ) and here are the specs as it does take a while to get them off the site.

Alpine SWE 1241

Thiel Small Parameters

Coil Height (Hvc) : 33.4mm
Cone Area (Sd) : 490.87 sq. cm
D.C.Coil Resistance (Re) : 3.6 ohm
Electrical Q (Qes) : 0.70
Equivalent Suspension Stiffness (Vas) : 61 liters(2.3cu.ft.)
Free Air Resonance (Fs) : 31Hz
Frequency Response : 26Hz - 1kHz
Gap Height (Hag) : 10mm
Impedance (Nominal) : 4 ohm
Inductance (Le) : 2.78mH at 1kHz (0.86mH at 20kHz)
Linear Excursion (X linear) : 11.7mm
Maximum Excursion (X peak) : 23.4mm
Mechanical Excursion (Peak-to-Peak) : 40mm
Mechanical Q (Qms) : 9.68
Sensitivity : 89 dB/W/M
Total Loudspeaker Q (Qts) : 0.66

Features:
Woofer

Bumped Backplate
Custom High-Strength Steel Basket
Designed and Engineered in the USA
Dual Progressive Nomex® Spiders with Integrated Tinsel Leads with Edge Control
High Excursion 3/4" Santoprene Surround
High Strength Brass Voice Coil Bobbin
Kevlar Reinforced Pulp Cone
Oversized Parabolic Dustcap

Specs:
General-Subwoofers

Diaphragm Material : Kevlar Reinforced Pulp
Magnetic Weight : 64oz.
Mounting Depth (top mount) : 159mm (6.4”)
Mounting Diameter (top mount) : 274mm (11”)
Recommended Box Types : Sealed/Bandpass
Recommended Sealed Box Volume : 0.8 – 1.7 cu. ft.
Spider Material : Dual Oversized Nomex
Voice Coil Diameter : 38mm
Power Handling

Power Handling Capacity (Peak) : 600W
Power Handling Capacity (RMS) : 200W
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Old 2nd February 2004, 03:08 PM   #6
Nuuk is offline Nuuk  United Kingdom
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Quote:
You don't need to reach fully 65hz because the rolloff of your speakers together with your sub will complete the spectrum...at a certain point...
That's right Guss. I think that Rod Elliot suggests going to about 0.75 of the -3db point of the main drivers.
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Old 2nd February 2004, 03:53 PM   #7
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Nuuk:

Well, as you pointed out, really deep bass is hard to get from a dipole.

At any rate, all that is required is to take a board, a stand that allows the board to tilt back for the board to keep it's balance, and see how it sounds.

With an Fs of 31 and a Qts of .7, your speaker in a true Infinite Baffle, (where the box affects the speaker not at all) would be -3 dB at 31 Hz, which is very good.

You don't have any closet doors handy to mount these in, do you? That would save a lot of trouble.

Otherwise, what I would do is to take a closed box of 2.3 cu Ft or larger. The sealed system in the closed 2.3 cu Ft box will remain at the midpoint all the way down to 42 Hz, with a respectable Qtc of 1.0. If you want, you can make an aperiodic vent and lower the Qtc even further.

Try the experimental slanted board first-easy enough to do, I would think.

Kuei did his in acrylic, but the principle remains-one slanted board to a single base board.
http://www.diyaudio.com/forums/attac...?postid=234863
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Old 2nd February 2004, 05:20 PM   #8
Nuuk is offline Nuuk  United Kingdom
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Quote:
Kuei did his in acrylic, but the principle remains-one slanted board to a single base board.
That's Kuei's full-range unit, not his bass woofer!

I'm leaning toward the U baffles but in my case they would be firing through the main baffles and I wonder what effects this may have on performance?

Click the image to open in full size.
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Old 2nd February 2004, 07:01 PM   #9
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Does anyone have one of these?
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Old 2nd February 2004, 08:12 PM   #10
Nuuk is offline Nuuk  United Kingdom
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Quote:
Does anyone have one of these?
Aaarrgh, not another option

Well it looks good on paper but.......

And of course, for those of us outside the US, it would be a case of finding suitable drivers. I think for now, I would rather keep things a bit simpler but it would be good to find out more from somebody who has actually heard one.
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