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Old 30th March 2015, 02:49 AM   #1
AlexQS is offline AlexQS  United States
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Default Efficient 3-way

I'm trying to achieve high efficiency and good bass for low power amp.

Will the below speaker choices work? My goals include good bass, more volume without turning the knob as far, clean/clear soundstage, and good imaging and instrument seperation. It will run on my pair of LM3875 Peter Daniels kit I built a few years ago. I can't remember exactly, but with the P/S I chose I think it's close to 40 watts per channel and needs an 8 ohm speaker.

Tweeter: Fostex FT17H
8 Ohm, 98.5dB
Crossover to play at 7500Hz and higher
http://www.madisound.com/loudspeaker...ions/ft17h.pdf

Mid: Audax PR170M0 6.5" Midrange 100dB
cross to play from 250Hz to 7500Hz
Will be in sealed 0.2 cu. ft. (F3 190)
https://www.madisoundspeakerstore.co...idrange-100db/

Bass: Goldwood GW-1558
8 ohm, 95.6 dB
Crossed to play 250Hz and lower
Will be in a huge 34.6 cu ft (less displacement of .2 cu ft sealed mid box) net 34.4 cu ft vented box (f3 22Hz)
Goldwood GW-1558 15" Pro Woofer
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Old 30th March 2015, 04:35 AM   #2
_henry_ is offline _henry_  Australia
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you need to have tweeter that can play lower than that.

if its going to be passive vented bass, max sensitivity will be around 94db max (in general for a suitable woofer in a suitable box), unless you loaded it in a horn enclosure.

when you design speakers, the physical distance between midrange and tweeter will dictate your transfer function, so it will be below 4khz if you want to get the right summation between them and seamless sound.

simulate your selected bass driver to make sure you can get your target sensitivity.

the midrange can be 2db lower than the tweeter and/or woofer, and whichever has lowest sensitivity will be your final sensitivity (woofer (in your cab alignment), mid and tweeter)
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Old 30th March 2015, 05:52 AM   #3
AlexQS is offline AlexQS  United States
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Thanks for reply. I thought the tweeter might be too high. So you're saying it just doesn't come low enough in frequency to match the mid I chose, and if I find a tweeter that will play 4k or lower then it will sum with the mid I chose? Or are you saying something else about 4k that doesn't have to do with the mid I chose?

When you say: simulate your selected bass driver to make sure you can get your target sensitivity.

Is the graph here what you mean by simulate?
http://www.goldwoodsound.com/Woofers...1558graphs.pdf

If so, what do you think, and if not, how do I simulate?

Thanks,
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Old 30th March 2015, 06:34 AM   #4
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The bass transducer: the manufacturer says that it is designed for all uses except hi-fi - it isn't mentioned !
And it is too big! You could replace Sd to excursion, so maybe a 10"
and could gain some dB/SPL by using a 4 Ω speaker ( so maybe... a car speaker ).
The Audax mid works well also with 1st order crossover, about 33uF and 0.5 mH. It's low excursion makes it unsuitable for a 250 Hz crossover point until 4th order is considered...
I used it with an Audax titanium dome 94 dB/W/m; also silk dome making 96 dB is available, though they both don't have ferrofluid.
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Old 30th March 2015, 06:37 AM   #5
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------------As others have noted-----------
The Fostex requires a Xover over 5Khz.
The Audax PR170M0 cone craps-out around 3Khz from resonance and beaming.
The Goldwood GW-1558 has Qts=0.63, and is best suited for dipole operation. It and was probably designed for open back guitar amps.

---------------
Since you are willing to accept a 34.4 cu ft vented box, take a look at the 9cuft Maximus_18 kit coming soon from diysoundgroup.com. 97db @2.83V sensitivity

Maximus-18 DIY Sound Group

Maximus-18 DIY Sound Group
Price Break Down:
1- 18" woofer ~$220 for Peavey LoRide18
1- 12" Eminence Deltalite woofer: $134.99
1- Denovo FL-450: $142
1- SEOS-15 waveguide: $35
1- Set of crossover parts: $TBA
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Old 30th March 2015, 06:44 AM   #6
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Some guys around here do these things with the Audax mid/tw combo
XS-96 | Gold Note
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Old 30th March 2015, 07:50 AM   #7
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Quote:
Originally Posted by picowallspeaker View Post
Some guys around here do these things with the Audax mid/tw combo
A crossover at 4.5Khz with the PR170M0 to a dome tweeter as in the XS-96 will have noticable lobing... both large changes in SPL sitting vs. standing, and also changes in perceived volume around the Xover frequency as the percentage of direct listener SPL vs. indirect room SPL changes. Lobes push more sound energy down(floor_bounce) and up(ceiling_bounce) and those reflections change the sound stage.

Also, the polar response of the Audax PR170M0 must be closely matched to the polar response of the tweeter around the Xover frequency to maintain a smooth directivity function, for both uniform SPL and consistent room reflections(sound stage).

The promise of powerful dynamics with excellent low level details from a high efficiency speaker creates challenges. The "good" sometimes overshadows the "nasty" in some modest cost/size high efficiency designs.
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Old 30th March 2015, 11:57 AM   #8
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I'd go for the biggest compression driver you can get, and a 15" driver below it.

Fewer drivers on the same budget means each driver is of better quality. For instance, I really like my Beyma 15P1200Nd + EV DH1a 2-ways. I use them for PA duties, but they're also perfectly at home in a HiFi situation.

You could use 3 cu.ft for the bass drivers and achieve respectably low bass, though an f3 of 22Hz might be pushing it. I can say, though, that the high-end pro 15"s are worth the extra.

Chris
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Old 30th March 2015, 12:38 PM   #9
AndrewT is offline AndrewT  Scotland
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I would not attempt a vented box for a driver with a Q=0.63.
That is either sealed box, or open baffle, or even infinite baffle. Maybe a little bit of LT to adjust the box Q and the F-3dB
But with a 3.9mm Xmax you will need a low bass speaker making it a 4way if you want/need low bass reproduction.
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Old 30th March 2015, 04:07 PM   #10
pguerin is offline pguerin  France
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Hi,

Considering the combo PR170 M0 / Audax tweeter you can have a look at the Pro 33 Kit from Audax, cf shematics. The discontinuited PR 130 has been replaced with success with Fostex FT17H, see crossover shematics.

But it's an almost 25 years old design Click the image to open in full size.
Attached Images
File Type: jpg pro33.jpg (295.0 KB, 52 views)
File Type: jpg FliltresF17H.jpg (98.2 KB, 53 views)

Last edited by pguerin; 30th March 2015 at 04:24 PM.
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