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Old 2nd September 2008, 08:01 AM   #1
the joz is offline the joz  Australia
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Default Help with Sub Drivers for my 2 Channel Full Range

Hi I posted here tather than the Sub section I hope it's OK??

Guys looking for some help with driver selection for my mains.
I'm building a pair of floorstanders that will be all active.
These speakers are going into quite a large room aswell and will be out from the wall approx 1 meter and away from side walls minmum of about 1.5 meters.

Basically the setup will be as follows
SW-M-T-M-W-SW

My dilemma is choosing the bass/sub driver.
The mids and highs are taken care of by Scanspeak Revelators so far and I'm happy with what I've got there.
What I'm after is some sealed boxes to keep the sizes down hopefully.
I know, but as it is they'll be plenty big without over doing it huge bass boxes.

As it is the SS Rev bass drivers roll of pretty quickly below 70hz in their sealed box so I would like to get a driver's that would easily crossover with them at about 80hz and reach down deep as flat and clean as possible.
I would also prefer 8ohm drivers to run in parallel rather than 4ohm units

So far whats on offer are a couple of the following..

P.Audio TM12...unfortunately 4ohm.

Specs on the woofers as below:
Nominal Dia: 320mm
Effective Piston Dia: 245mm
Rated Impedance: 4 ohms
Power Handling: 400 watts rms
Sensitivity: 92dB 2.83V/1 metre
Voice Coil Dia: 77mm
Magnet: 171.6 Oz Ferrite

Fs: 48.5Hz
Re: 3.5Ohms
Qms: 8.750
Qes: 0.550
Qts: 0.520
BL: 19.30
Mms: 192.19Gr
Vas: 17.51 litres
Sd: 0.0471 M/sq
Le: 1.00 mH
Eff: 0.35%
Hag: 9.5mm
Hvc: 36.00mm
Xmax: 13.33mm each direction.

One os my concerns with the PAudio is that It needs a tonn of power to get that cone moving because as the vas suggests it seems verey non compliant.


or
the Peerless 12"Peerless 830847 subwoofer


Description: 308 mm XLS home subwoofer with 8 + 8 Ohm voice coil. For small enclosures of around 58 litres.

Nominal impedance Zn (Ohm) 4 Reference voltage sensitivity (dB) 92.0
Minimum impedance/at freq Zmin (Ohm/Hz) 3.0/115 Voice coil diameter d (mm) 51
Maximum impedance Zo (Ohm) 72 Voice coil length h (mm) 33
DC resistance Re (Ohm) 2.5 Voice coil layers n 2
Voice coil inductance Le (mH) 1.8 Flux density in gap B (T) #
Resonance frequency fs (Hz) 21.8 Total useful flux (mWb) 2.3
Mechanical Q factor Qms 10.24 Height of the gap hg (mm) 8
Electrical Q factor Qes 0.37 Diameter of magnet dm (mm) 147
Total Q factor Qts 0.36 Height of magnet hm (mm) 35
F (Ratio fs/Qts) F (Hz) 60 Long term power (IEC) (W) 175
Mechanical resistance Rms (Kg/s) 1.48 Max linear SPL (rms) (dB/W) #
Mechanical loss Rm (Ns/m) # Xmax peak (mm) 12.5
Moving mass Mms (g) 110.9 Nominal power (W) 350
Suspension compliance Cms (mm/N) 0.48 Frequency range (Hz) #
Effective cone diameter D (cm) 24.4 Net weight (kg) #
Effective piston area Sd (cm²) 466 Recommended Box Volume (Vb) (Litres) #
Equivalent volume Vas (ltrs) 144.2 Recommended Port Diameter (mm) #
Force factor BI (Tm) 10.2 Recommended Port Length (mm) #


Another Peerless....Peerless 830500 subwoofer


Description: 308 mm XLS 8 Ohm subwoofer for demanding compact subwoofers. Heavy rigid alloy frame.

Nominal impedance Zn (Ohm) 8 Reference voltage sensitivity (dB) 90.6
Minimum impedance/at freq Zmin (Ohm/Hz) 4.7/106 Voice coil diameter d (mm) 51
Maximum impedance Zo (Ohm) 64.2 Voice coil length h (mm) 33
DC resistance Re (Ohm) 3.5 Voice coil layers n 4
Voice coil inductance Le (mH) 4.2 Flux density in gap B (T) 1.04
Resonance frequency fs (Hz) 18.1 Total useful flux (mWb) 2.5
Mechanical Q factor Qms 3.70 Height of the gap hg (mm) 8
Electrical Q factor Qes 0.21 Diameter of magnet dm (mm) 147
Total Q factor Qts 0.20 Height of magnet hm (mm) 35
F (Ratio fs/Qts) F (Hz) 90 Long term power (IEC) (W) 165
Mechanical resistance Rms (Kg/s) 5.12 Max linear SPL (rms) (dB/W) #
Mechanical loss Rm (Ns/m) # Xmax peak (mm) 12.5
Moving mass Mms (g) 166.3 Nominal power (W) 300
Suspension compliance Cms (mm/N) 0.46 Frequency range (Hz) #
Effective cone diameter D (cm) 24.4 Net weight (kg) #
Effective piston area Sd (cm²) 466 Recommended Box Volume (Vb) (Litres) #
Equivalent volume Vas (ltrs) 139.2 Recommended Port Diameter (mm) #
Force factor BI (Tm) 17.6 Recommended Port Length (mm) #
(*) Not applicable to this speaker. (#) Applicable but not available



Please excuse to formatting,cut and paste jobby not quite neat.

Anyhow I will gladly look at any suggestions or recommendations to solve my decision making.

Not looking for the cheapest item around just something that'd give some decsnt SPls while staying clean.

Now I've probably left out some important info so please excuse me..



Oh! and a favorite of a freind of mine the..

NHT 1259
NHT 1259 Specifications
Fs 16.5Hz
Nominal Impedance 4 ohm
Mmd 128.0 Grams
Cms 696.48 m/n
Vas 238.4 Liters
Rscc 3.52 W
Leap Krm 3.277 mW
Leap Kxm 10.063 mH
Leap Erm 0.772
Leap Exm 0.743
vcL 1.06mH @1K
Bl 9.574 Tm
Qms 2.680
Qes 0.533
Qts 0.445
Voice Coil Height 34 mm
Air Gap Height 8 mm
Xmax 13.0 mm Peak
SD 0.0491 m 3
Surround Rubber
Cone Material Polypropylene
Magnet 59 oz.
Voice Coil 50 mm
Music Power 300 Watts
Sensitivity 90 dB 2.83V/1m


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Old 2nd September 2008, 08:24 AM   #2
BHTX is offline BHTX  United States
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Jeez.. why all the drivers?
Why integrate subwoofers into the mains?
Might as well go SW-W-M-T-M-W-SW instead of SW-M-T-M-W-SW then, no?
Just curious.. what amps and active crossovers are you using for all of that?
By the way, the NHT/MAD 1259 requires a sealed enclosure that's probably much larger than what you're looking for.
Anyway, if 12's is what you're wanting, how about the Dayton DVC? Or is that not pretty enough? Not expensive enough? Would give you just as much, if not more, for less money. If you think that's not your cup of tea, what about the Reference series?

edit:
Oh, you're in Australia. Dunno what's available. Sorry.
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Old 2nd September 2008, 09:42 AM   #3
the joz is offline the joz  Australia
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Haha!

Your right,
I did mean SW-W-M-T-M-W-SW...oops!

My amps are a local product which give me about 180 watts rms 8ohms/channel and the active crossover is atm 2 x Rane AC23's running as 4 way.

All I can say is I'll look at the Dayton as I'm not familiar with them at all.


Anyhow f I can't find the right drivers locally I can always import depending on the cost.


I'm just concerned about any decision with drivers,as you can appreciate not all bass/SW drivers sound the same.
I'm really wanting an articulate hi-fi reproduction rather than a big boom.

But any input welcome ..
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Old 2nd September 2008, 10:52 AM   #4
BHTX is offline BHTX  United States
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Default Re: Help with Sub Drivers for my 2 Channel Full Range

Quote:
Originally posted by the joz
As it is the SS Rev bass drivers roll of pretty quickly below 70hz in their sealed box so I would like to get a driver's that would easily crossover with them at about 80hz and reach down deep as flat and clean as possible.
Quote:
Originally posted by the joz
I'm just concerned about any decision with drivers,as you can appreciate not all bass/SW drivers sound the same.
I'm really wanting an articulate hi-fi reproduction rather than a big boom.
You'd probably be surprised then at just how little these small characteristics of individual loudspeaker drivers often contribute to the end result, especially in large multi-way systems like yours. Even more so, relying on price as an indicator of performance is bad way to go IMO.

Anyway, sure, not all woofers sound the same. However, given two completely different 12" subwoofer drivers with similar parameters and performance, each placed in their own suitable enclosures, and lowpassed at 80 Hz or less.. I'm positive you wouldn't be able to hear the difference between the two. As long as it's a suitable driver for the intended application in the right enclosure, the room and placement will have a much greater effect at lower frequencies than the driver itself ever will. And at the very lowest octaves, it's really all about air movement anyway. Rather than looking for "high-end" names and high prices, focus on finding the right balance between size, sensitivity, freq extension, and output.. then, find a good bass driver that suits the app, without unnecessary BS and added cost. Even something as drastic as a cheaper stamped steel frame isn't really going to make a bit of difference on a subwoofer driver.

..Just my $0.02.
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Old 3rd September 2008, 10:50 PM   #5
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Quote:
What I'm after is some sealed boxes to keep the sizes down hopefully.
It's usually the other way around (unless you're applying active EQ?). But if size is a priority, you could still go sealed, but use two woofers front-to-front or back-to-back in half the volume. In this case, 4 Ohms each works out OK.
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Old 4th September 2008, 01:02 AM   #6
the joz is offline the joz  Australia
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Thanks again for your thoughts and input guys.
I pretty much know that what I'm buliding aren't going to be small.
But without rushing into it I'm trying to keep box size down if possible.
It seems maybe high excusion and high power will be needed ortherwise it may come down to ported enclosures.

Arrgh! life wasn't meant to be easy...

Anyhow the search continues..
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Old 4th September 2008, 03:10 AM   #7
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If your heart is set on building the subwoofers into the same cabinet as your tweeter (a bad idea if you believe in doppler/intermodulation/whatever they call it now distortion, and non-geometric subwoofer placement) you don't have to put them both on the front, apart from the bonus visual impact.
The recoil of the two subs pushing the box the same way will cause the rest of your drivers to move also (unless its back is bolted to a concrete wall?), the amplitude of this can be significant compared to hf drivers, and people complain about the effects of this.
If you have one on the opposite side of the other, you have no recoil pushing the box, and if one of them has its rear pointed outwards you can 'minimise even-order distortion' caused by the drivers differing behaviour when cone is traveling outwards and when inwards. I'm doing this on my current project, results to come.
At subwoofer frequencies they're pretty much omnidirectional anyway so it'll perform about the same, just won't look symmetrical, unless you mount them on the left and right sides of the cabinet.
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Old 4th September 2008, 04:03 AM   #8
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Hi joz,

With today's best speaker technology I think the only reason to build a 4 way is because of a religious believe in acoustic 1st order crossovers. If you accept LR4 or B3 or B5 slopes after reading JohnK's Music and Design Xover articles, a 3 way WMTMW with say 15" Lambda TD15S, ScanSpeak 6.5" Revalator, and Seas T25001 Millenium can get 20-20K with excellent phase coherence. Use the speaker budget$ on 5 instead of 7 speakers.


http://www.rockporttechnologies.com/

Rockport Technologies Hyperion
13" Audiotechnology
6" Audiotechnology
1.1" Dynaudio Estar
74.66 " high
19" wide
29.25" deep
585 lbs
Attached Images
File Type: jpg hyperion.jpg (36.7 KB, 315 views)
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Old 4th September 2008, 04:12 AM   #9
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Flagship 4-way SW-W-M-T-M-W-SW often seem over the top. Perhaps the designer wanted to use 1st order on the main WMTW which allows the owner to uses tubes or SS amps, and then use a separate sub amp with steep Xover to pump up the 16Hz pipe organ. When I look at this Rockport Arrakis I wonder if putting the two subwoofers on opposing sides at the bottom of the cabinet would give push-pull counter mass vibration removal plus better floor gain.

Some 4-ways use 0.75" tweeter, 4" mid, 8" woofer and 15" subwoofer.


Rockport Arrakis
15" Audiotechnology
8" Audiotechnology
5.25" Audiotechnology
1" Ring Radiator
81" high
24" wide
36.5" deep
900 lbs
Attached Images
File Type: jpg arrakis.jpg (35.3 KB, 303 views)
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Old 5th September 2008, 03:22 AM   #10
the joz is offline the joz  Australia
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Hi linesource,stunning speakers the Rockports,but putting the two sub drivers on opposing sides would mean using a huge cabinet I think.Though I do like the Hyperions.

But the drivers I'm using are from another project that a freind tired off (Ekta Grands)and I bought of him.
I have had them running in my room for a while but with the rear ports they I felt that I couldn't place them properly.
Don't get me wrong they performed very well indeed with with amazing bass.
The two 7" Revelator bass drivers did an amazing job.
But somehow the overall balance was not to my taste, the highs mids and upper bass I like but the lower registers I prefer from my other subs running below 70-80hz.
Hence time to rebuild them.

Here's a pic of one of the Ekta Grands
Attached Images
File Type: jpg ekta grands007.jpg (63.8 KB, 288 views)
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