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Old 11th July 2013, 09:17 PM   #11
golfnut is offline golfnut  New Zealand
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Hi All

Having built a set of 7.2 pensils I'm keen to explore as FAST option to fill in the bottom. I've also completed a set of ESLs that bottom out just below 40Hz, and I am amazed how much better the bass is compared to my olf KEFs that bottomed out at 50 Hz. So I've been looking for a 8-10" driver that will have f3 in a closed box (for good group delay) below 40 Hz. So far I have only found one, the Scanspeak 23W4557, which looks very good but is horrifically expensive.

Q1: does anyone know of other smallish woofers with f3 below 40 Hz? I've searched online T&S databases and the Scanspeak driver is a standout.

Q2: Has anyone tried adding mass to a woofer cone, e.g. by adding a metal ring or epoxy near the dustcap. This would lower the fs and enable operation to lower frequencies in closed box. The cost is higher Q of the driver - bigger cabinet volume, and a loss in sensitivity. By my reckoning, adding about 30% extra mass to one of the Dayton 8" drivers would have the desired effect.
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Old 11th July 2013, 09:57 PM   #12
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Quote:
Originally Posted by golfnut View Post
Hi All

Q2: Has anyone tried adding mass to a woofer cone, e.g. by adding a metal ring or epoxy near the dustcap. This would lower the fs and enable operation to lower frequencies in closed box. The cost is higher Q of the driver - bigger cabinet volume, and a loss in sensitivity. By my reckoning, adding about 30% extra mass to one of the Dayton 8" drivers would have the desired effect.
Hi G, Guys,
I'd strongly urge not adding 30% additional mass to a small woof (or any small driver). I'm certain no driver designer will factor-in additional loads of this magnitude into the driver's suspensions. There's a real risk of taking the unit's power-train out of operational alignment, coil rub leading to circuit failure is a possibility. I'm certain most all makers will their void warranties against such modifications.

For further discussion on modifications of this magnitude, please use a forum section like the lounge:

The Lounge - diyAudio

Thanks
Mark.
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Old 11th July 2013, 11:09 PM   #13
Einric is offline Einric  United States
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Default AP6.2 Gold x Dual DA175 Passive FAST

Here is just a simulation but it looks kinda promising, Parts would cost about $200 +S&H.
4 DA175's should provide plenty of bottom end.
The A6.2MA will be in the Madisound 1.7l chamber and the DA175's would be in 1.8-2cuft shared tuned to 31-33hz.
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Old 12th July 2013, 01:50 AM   #14
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I am seriously looking at the Dayton RSS315HF-4 in a 50l sealed box. Using a Linkwitz transform or a DSP equivalent, you can get 103dB@30Hz and 97dB@20Hz. This at 250w/ch and not exceeding either Xmax or RMS power limits. The beauty of sealed is that you can run prodigious power through the speaker without worrying about the cabinet unloading.

Bob
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Old 27th November 2013, 02:17 PM   #15
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Hey guys, sorry to go off topic but what's that software your using for sims Einric?

A friend just gave me 500 bucks and asked me to build her! a set of towers. I'm set on the A7.3 and possibly the SLS 830669. Thinking slim cab with the SLS mounted on the sides.

I am limited to about 150 per driver and local availability for drivers in Melbourne, Aus.

Has/could anybody sim the SLS with the A7.3?

Cheers for any advice.
Dean

Last edited by thunk303; 27th November 2013 at 02:25 PM. Reason: clarity
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Old 27th November 2013, 03:35 PM   #16
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Looks like X.Over 3 Pro, possibly with box plot from BassBox 6 spliced in. Both programmes, especially the former, have a dodgy reputation, but they can (can) be quite effective providing you know what you're doing.
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Old 28th November 2013, 10:21 AM   #17
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Still looking at a FAST system with the A7.3, but finding an appropriate woofer is a bit of a pain... with my various requirements of low f3, ~60L sealed box size etc. the two best fits I've found so far are the Scan Speak 26W/8534G00 and 26W/8861T00. the latter being near 4x the price of the former...

Looking forward to getting this built, but it's turning into a long term project including amps and DPS
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Old 28th November 2013, 04:02 PM   #18
chrisb is offline chrisb  Canada
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take a look at some of Peerless 5.5 - 6.5" such as 830875, etc?


with several different "FAST" projects over the past few years, we've had much more seamless integration with multiples of smaller woofers (such as 4@830870 in dual side mounted push/push configuration in the faceted enclosure below )

Click the image to open in full size.
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Old 28th November 2013, 07:20 PM   #19
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What's pictured, is that four per enclosure? With multiple smaller woofers would I need a vented enclosure to get a lower frequency response. Or would I be able to stay sealed and utilise active DSP/PEQ to cut & boost my way there... within reason.

Am looking at peak SPL of 80~85dB, so most of the drivers mentioned will hit well over 90dB with 4~8 Watts.
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Old 28th November 2013, 07:35 PM   #20
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Quote:
Originally Posted by BuildMeSomething View Post
What's pictured, is that four per enclosure?
4 Peerless 830870 4" bass drivers. We had to get Scott to design an ML-V to get the bass enclosure tall enuff to support the co-laterally mounted mid-tweeter to be at a reasonable height. PLLXO 1st order at 240 Hz.

The ML-TL for these bass drivers is used with a pair as a woofT for the uFonkenSET (same XO).

Click the image to open in full size.

These woofers like lots of volume but do dig low in the quarter-wave boxes. When working on our stand-mount MTM i 1st looked at these, but they needed 30 litre BR to match the extention of the 2 Silver Flutes W14 (in 10 litre) we finally settled on.

dave
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