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Multi-Way Conventional loudspeakers with crossovers

A Bookshelf Multi-Way Point-Source Horn
A Bookshelf Multi-Way Point-Source Horn
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Old 10th January 2016, 10:59 AM   #21
bushmeister is offline bushmeister
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So at 0cm 36mmx36mm
at 5cm 60mmx50mm
at 10cm 90mmx70mm
at 15cm 155mm x 110mm
at 20cm 240mmx190mm
at 25cm 360mmx280mm

Hope this helps!
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Old 10th January 2016, 11:35 AM   #22
xrk971 is offline xrk971  United States
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A Bookshelf Multi-Way Point-Source Horn
This is perfect. Thanks.
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Old 10th January 2016, 11:40 AM   #23
bushmeister is offline bushmeister
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Xrk,

I haven't pulled the trigger on the woofers yet - awaiting your modelling to ensure they will be suitable.

There is an offer on 8 of the SB12NRX25-4 - 4ohm version. Will this make any difference? - as will save me a few pounds!

If not, and the 4 ohm version models well I will order 8. The nice thing with having 4 per horn is because they will be mounted in the corners the shortest port length will be achieved - if I used two larger woofers, the ports would likely be longer if I tried to get them into the corners.
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Old 10th January 2016, 11:45 AM   #24
bushmeister is offline bushmeister
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Link to 4 ohm version - more sensitive, slightly lower Fs, slightly higher Qes.

SB Acoustics :: 4? SB12NRX25-4
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Old 10th January 2016, 11:49 AM   #25
xrk971 is offline xrk971  United States
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A Bookshelf Multi-Way Point-Source Horn
That looks promising. Let me see if I can get a model out sometime today. Those are some big magnets - SBA seems like a nice deal. I have to see what these sell for in the US. They are nice compact woofers.

These go for $50 at Madisound - so not cheap but may be well worth it. I like the specs a lot.
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Old 10th January 2016, 12:43 PM   #26
bushmeister is offline bushmeister
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I can get them for $35 each - one of the rare occasions where we can get speaker parts in the UK cheaper than in the US!
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Old 10th January 2016, 12:52 PM   #27
mayhem13 is offline mayhem13  United States
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You could actually call this a 'bookshelf' design of you oriented the horn vertically and the listening position was near/mid field. There's a similiar DIY design using the Eminence H2EA horn used vertically but I can't find the damn link!��
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Old 10th January 2016, 02:57 PM   #28
xrk971 is offline xrk971  United States
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Default xBUSH v1.0

Bushmeister,
You are in luck...

I put the WG dimensions into Akabak, put the TS parameters for the SB12NRX25-4 in, adjusted where the bass injection port goes (currently at 10cm back from exit plane at mouth - adjustment closer to front possible with a few dB loss). I used the 2 liter per woofer rear chamber suggested by Byrtt along with Byrtt's estimate of 50cc volume for cone and 34mm dia injection ports that are 30mm long.

For this simulation, we are assuming that the SB65WBAC25-4 couples into the WG perfectly with no throat cancellation effects, and a minimal front chamber effect (volume formed by driver and throat is assumed neglible).

Electrical Filter settings are set as:

SB65WBAC25 is Butterworth -12dB/oct high pass at 350Hz with a 1.12ms delay. Also -3dB padding is applied to get SPL to be closer to woofer.

Qnty 4 SB12NRX25-4's in series/parallel and have -24dB/oct Butterworth low pass filter at 350Hz. A -12dB/oct Butterworth high pass at 80Hz is used to prevent over excursion and for handover to sub woofer.

These electrical filter settings combined with the acoustic filters produce an overall acoustic XO at 500Hz and are Harsch like. This cannot be done until you have actually built it because electrical filters will need to be adjusted to get acoustic target to match the BW4 for the woofer and Bessel 2 for the mid/tweet.

Ok, enough talk, here are the initial results - no EQ applied.

SPL at 2.83v and 1 meter - so first thing we notice is that the system will probably work and the drivers will cover their own territory, the horn is quite efficient and these little 4 inch woofers really can't keep up, 500Hz XO seems to be a sweet spot, note that HF performance of SB65WB above 3kHz is probably not going to be as flat or as high - expect -12dB falloff and several dips due to throat cancellation. Overall a very promising start and I would say the main problem is not enough SPL at 80Hz for the XO to sub. If you are OK with 98dB max at 80Hz then get these drivers. The overall system sensitivity of 91dB that I estimated based on the woofer seems to be good - you can just -ve EQ everything to flat at 91dB and save distortion on SB65WB:

Click the image to open in full size.

Cone displacement at xmax with 21v (-3dB on on SB65WB) - the SB65WB is hardly moving so the HD should be low:

Click the image to open in full size.

Max SPL capability at 21v (-3dB on SB65WB) - with proper woofers that have more guts, this system could be quite loud:

Click the image to open in full size.

Electrical input power at 21v (-3dB on SB65WB) this is excellent and shows all thermal values are not exceeded with some room for EQ'ing the SB65WB:

Click the image to open in full size.

I will run the 8ohm case just to check but I imagine it won't be much different, perhaps not as good.

Let me know if you have another larger woofer maybe qnty 2 x 6.5in? 4x 5.25in? Will an 8in woofer fit?

Interestingly, if you were to use bass reflex re-injection right along periphery of horn mouth, you can get quite a bit more reach and integrate well with the sub. Here is what it would look like with 4 Liter rear chambers ea and a 1.75in dia x 8.5in long duct x qnty 4 ducts total, the max voltage can go up to 22v and HPF can be backed off to 70Hz:

Click the image to open in full size.

The predicted impulse response doesn't look too bad actually:

Click the image to open in full size.
Attached Images
File Type: png Xbush-01-Freq-2.83v-500Hz.png (32.2 KB, 1479 views)
File Type: png Xbush-01-Elect-Power-Max-SPL-21v-500Hz.png (23.6 KB, 1479 views)
File Type: png Xbush-01-Max-SPL-21v-500Hz.png (35.3 KB, 1480 views)
File Type: png Xbush-01-Disp-21v-500Hz.png (22.4 KB, 1477 views)
File Type: png Xbush-01-Max-SPL-21v-500Hz-BR-Reinject.png (14.9 KB, 1470 views)
File Type: png Xbush-01-Max-SPL-21v-500Hz-BR-Reinject-IR.png (13.1 KB, 1443 views)

Last edited by xrk971; 10th January 2016 at 03:20 PM.
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Old 10th January 2016, 03:45 PM   #29
bushmeister is offline bushmeister
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Wow! Fantastic work Xrk!

Having done all this - I feel a little guilty looking at other woofers - as it will make more work for you - but, I didn't expect the SB65 to have so much more output than the woofers!

I will just have a re-look at the horn dimensions and woofer options. Give me 10mins!
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Old 10th January 2016, 03:54 PM   #30
bushmeister is offline bushmeister
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OK two of these, per horn (I will have to remove ribs as you suggested) provides almost 3 times the VD cm3:

SB Acoustics :: 8'' SB23NRXS45-8

Fs - 27, Qes 0.41, P-P 13mm.....

Sorry to generate more work for you. I was hoping to avoid removing the ribs - hence the reason for choosing the 4" drivers to fit in between.

Last edited by bushmeister; 10th January 2016 at 03:59 PM.
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