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Some questions before I start sonosub.


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#1 of 25 OFFLINE   Harry Lincoln

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Posted March 31 2001 - 02:03 PM

I will be starting my sonosubs next week. I am planning to make two subs, each using the Shiva driver mounted in a downfiring position and 16" sonotube.
I saw a post on another thread from Patrick Sun that suggested a couple of possible designs for this driver(using LspCAD). The one I am currently planning on using is:

6ft^3 internal box volume
2 x 4" ports 23" long
Tune = 17Hz

1) I will be using these subs mainly for movies. My room is approx 19x13x9. I usually listen at about 5-10db below reference, so I do not need insane SPL output (althogh I'd stil like a lot), but I want them to go LOW and stay flat. Am I on the right track with this design? (I dont have a PC so I cant run my own sims) What are the predicted perfomance figures for this design?

2) If I use the dual port configuration, how should I space the ports, evenly spaced between the side walls and each port or should the ports be as close to the centre of the enclosure as possible. I think I read somewhere that the port diameter should be at least equal to the distance between the port and the sidewall.

3) Has anyone measured the internal vloume displacement of the Shiva driver?

4) I've been doing some research on the net and have noticed that there are two sets of specs going around for the shiva driver. eg. the Adire site lists the Qts as 0.39, vas 150lt x-max 15.1mm, I found this specsheet reproduced on some DIY sites sites but some of the values were different (Qts0.38, vas 144l and xmax 15.9mm). At first I thought these would apply to the mk1 and mk2 Shivas but the xmax values are 15.1 and 15.9, the Adire site claims the Xmax was increased by 1mm for the mk2 driver. Whats the go here? I live in oz so I might not be able to get the mk2 over here, If the specs are different for the two how will that affect the cabinet volume and port calculations?

5) I will be installing an SVS style base plate ont he subs, how much space should I leave between the driver and baseplate?

6) I am currently using two Yamaha YST SW300 subs. Would it be possible to use the intenal amps from the Yamahas to power the sonosubs until I buy a deicated amp? The manual rates the amps as: 185w/5ohms. How should the Shiva VCs be wired?

7) What specs should I look for in an amp to power this combo? Amp suggestions welcome.

Thanks in advance for all replies.

p.s. I was initially planning to go the SVS route but because of the way the Aussie$ is looking and the freight costs to oz, TomV at SVS suggested I started looking at DIY. I was blown away by the price of this project. Total materials cost for the TWO subs is only $600aus.+amplification. To put that into perspective my YST-SW300 Yamahas cost me $1800 for the pair($2400retail).


Harry




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#2 of 25 OFFLINE   Dylan SJ

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Posted March 31 2001 - 02:28 PM

Harry: This is a bit OT, but have you got/ordered the Shiva's yet? I may have 2 MKI's for sale. I also have some 24" Sonotube. I'm on the Mornington Peninsula.

I'll do my best with some answers.

Quote:
2) If I use the dual port configuration, how should I space the ports, evenly spaced between the side walls and each port or should the ports be as close to the centre of the enclosure as possible. I think I read somewhere that the port diameter should be at least equal to the distance between the port and the sidewall.

I assume you will be putting the ports in the top? I think you just need to keep them a little away from the side wall, at least a port diameter seems good. You don't need to evenly space them, except for asthetics.

Quote:
3) Has anyone measured the internal vloume displacement of the Shiva driver?

The Shiva white paper says 3 liters.

Quote:
5) I will be installing an SVS style base plate ont he subs, how much space should I leave between the driver and baseplate?

I think 3 to 4 inches is enough.




#3 of 25 OFFLINE   Harry Lincoln

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Posted March 31 2001 - 03:16 PM

Dylan, no I haven't got my Shivas yet, I was planning on getting them in a few weeks - how much do you want for yours? I dont have a map handy and dont really know haw far away the Mornington Peninsula is from Bendigo, which side of Melbourne is it on?


Harry.

#4 of 25 OFFLINE   Harry Lincoln

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Posted March 31 2001 - 03:47 PM

Also Dylan, if you wouldn't mind, could you measure your Shiva for me, I need the measurements so I can cut the bottom end cap for the driver to sit flush with the cap, outer diameter, inner diameter and the thickness of the mounting face.
One question I forgot to ask in my initial post is what should i use as stuffing and how much?

Harry.

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#5 of 25 OFFLINE   Seungsoo Hwang

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Posted March 31 2001 - 04:36 PM

generally, you dont stuff vented subs, rather line the walls with something like polyester batting or fibreglass.

#6 of 25 OFFLINE   Harry Lincoln

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Posted March 31 2001 - 08:40 PM

Seungsoo, yeah I know, thats what I meant, poor choice of words.


Harry.

#7 of 25 OFFLINE   Dylan SJ

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Posted April 01 2001 - 04:14 PM

Harry: Mornington Peninsula is on the estern side of Melbourne, a fair distance from Bendigo. I still haven't decided on selling though. They are currently in an EBS sonotube and they may stay there or go into a small sealed box or I may sell? I believe you can buy new Shiva MKII's locally for $245+GST+Shipping.

I can't measure the driver any time soon but the Shiva White Paper gives the physical dimensions you need.

#8 of 25 OFFLINE   Julian Data

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Posted April 01 2001 - 04:37 PM

Harry,


Let me try to answer your questions:

1). With the provided power of 185W@4Ohms, this design is pretty good! Posted Image You seem to be on track here.


2) From the ends of the tube/endcap have at least .750" away and between a minimum of an inch or so. Will these ports be flared? If so, remember to compensate for the diameter of the flare, which I think is over 6-7" per port.

3) As per the white paper: 183 in3.

4) Use the DUMAX figures.

5) What plate amp(s) do you plan to use? I suppose that the amp will be on one of the endcaps or tube? I would rather have the amp externally, meaning not even installed with the enclosure.

6). If the Yamaha amps are stable at 4Ohms, I don't see a problem. BUT, more likely that the amp on the Yamaha sub has a "boost" for low Frequencies.

7) 250-300W should be fine. Remember that you are using two independent enclosures. I'd wired each VC/driver in parallel for 4Ohms and connected to each channel/amp.

If you plan to do one amp, wire them in series but this will change FR of the subs.


jD


#9 of 25 OFFLINE   Harry Lincoln

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Posted April 01 2001 - 07:32 PM

Dylan, If you decide to sell let me know - I spoke to a courier today and the freight f rom Mornington was quite cheap. Acoustic Concepts quoted $245 but I'm not sure if that included GST.
I'm posting on a Dreamcast console, I dont have a PC, the Dreamcast cannot display the Shiva White Papers or any .pdf files which is a pain in the arse.

Julian,
I could be wrong but I checked a site with a heap of Dumax figures(not sure if it was the Dumax site) and found no mention of the Shiva. How do I know which are the Dumax figures?
I don't plan on using a plate amp, I'll go with a stereo amp eventually so I can sell my Yamahas. The Yamaha does have an e.q. control to boost or cut the low feq, but I leave it in the neutral position. The amps are actualy rated at 5ohms not 4ohms but this shouldn't cause too many dramas.


Could someone who has a Shiva please measure the inner diam, outer diam and the thickness of the mounting face(the outer ring where the screws go), so I can cut my endcaps to flush-mount the driver. (or even get the measurements from the shiva white paper- I cant display the page on my DC console)This would be greatly appreciated.

Harry.

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#10 of 25 OFFLINE   Dylan SJ

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Posted April 01 2001 - 08:23 PM

Harry: Acoustic Concepts price is $245 PLUS GST. I know the owner personally and don't want be seen to be peddling on his behalf in the Forum. Having said that, his stock is all MkII Shiva's.

I've posted a screenshot of the white paper physical specs here . Hope you can see it.

Dylan

#11 of 25 OFFLINE   Harry Lincoln

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Posted April 01 2001 - 09:21 PM

Thanks for the screenshot Dylan, I got all the info I need. I've seen the changes made for the mk2 driver on the Adire site, do you know what the real-world performance differences are?


Harry.




#12 of 25 OFFLINE   Dylan SJ

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Posted April 01 2001 - 10:07 PM

Harry: The Adire specs are supposed to be pretty close to real world and most people use them comfortably.

Seeing you can't run the sims, I'll do them in LspCAD and post a screenshot for you. I'll base them on 6ft^3 @ 17Hz using 2 4" ports.

#13 of 25 OFFLINE   Dylan SJ

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Posted April 01 2001 - 11:29 PM

Harry: I ran your numbers, the screen shot is here . Basically, a 6ft^3 or 170l net volume with 2x 748mm long 100mm diameter ports.

#14 of 25 OFFLINE   Harry Lincoln

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Posted April 02 2001 - 07:50 PM

Dylan, the sceenshot file seems to load ok but there is no image on the page, thanks all the same. I'm a bit curious at the port length you mentioned in your above post (2 x 748mm). Was this reccommeneded by the LspCAD program? The initial design that I am working from recommended 2 x 548mm ports, also done with LspCAD, is that 7 supposed to be a 5?


Harry.

#15 of 25 OFFLINE   Dylan SJ

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Posted April 03 2001 - 12:31 AM

Harry: I changed the screenshot format, so please give it another try.

The 2x748mm port length was from LspCAD. The parameters I used were: 1xShiva MKII, VC in parallel, bassreflex box of 169.9l tuned at 17Hz, no fill and 2x10cm diameter ports.

I may have forgotten something, but I don't think so.

#16 of 25 OFFLINE   Patrick Sun

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Posted April 03 2001 - 12:37 AM

Using the same specs, I also get 2 ports 775mm long (using 101.6mm for the port width). 775mm is too long for port width (for port lengths, try to stay within 5 times the port width or you will have pipe resonance characteristics show up in your porting). I've built a sub with three ports (101.6mm wide) that were 914.4mm long and that was just simply too long for ports, I wound up cutting off the bottom endcap and starting over with a single 152.4mm wide port.

If you could fit a single flared port (nominal 101.6mm wide, and 400mm long) I would go with that option, rather than dual ports for this application.


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#17 of 25 OFFLINE   Harry Lincoln

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Posted April 03 2001 - 02:35 AM

Dylan, the screenshot works fine now, thanks again. Looking at the cone excursion graph, should I consider using a subsonic filter to protect the driver? I read somewhere that the Haunting DVD contains information as low as 4hz!
Thanks for the tip on the port Patrick. I spoke to my freind, the cabinet maker, today, he is making the endcaps for me, he suggested cutting a flare into the MDF top panel, 20mm radius cut - so the diameter at the top end of the flare would be 140mm, the bottom of the flare would be flush with the inside of the 4" PVC pipe, he suggested it because he thought it would look 'cool', (along with using 32mm polished chrome pipe around the outside of the dowells that connect the bottom endcap to the baseplate, and a circular press-on rubber mounted speaker grill (well not an actual grill, just a ring covered with speaker grill cloth), to stop anything falling down the port.)
What size flare should I get for the other end, or are all 4" flares the same? When measuring the port length, I assume you include the flares? Dylan, do you know if you friend at Acoustic Concepts sells flares?, or maybe I'll try a car audio store.
Any suggestions on what I should use to line the inside walls of the cabinet?

Harry.


#18 of 25 OFFLINE   Dylan SJ

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Posted April 03 2001 - 01:06 PM

Harry: Glad the screen shot worked (changed it from progressive to standard jpeg).

I would recommend a subsonic filter. I don't use one currently and occasionally bottom out. I will be using one with my Red Oktobers.

Acoustic doesn't have flares and doesn't know of any in Australia. You may find one at a car audio place or you could import one for the US, but given the $A....

Use polyester batting to line the walls. You should be able to find some at a local fabric store.

#19 of 25 OFFLINE   Harry Lincoln

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Posted April 03 2001 - 09:06 PM

I tried every car audio store in town today - no luck. Maybe I'll have a go at grafting a firbreglass flare onto the end of the PVC, or maybe make on out of wood. How big should the flare be?- I was thinking a 20mm radius (same as the flare on the top endcap) which would give a width of 140mm at the very bottom of the port. Would this work o.k. or should I go fo a bigger one?
Is there a formula for working out the volume of a flared port, or should I just seal both ends and dunk it in a bucket of water?
I have heard people mention that they sprayed the outside of the port tube in a rubber based coating to reduce resonance. Can anyone comment on whether they think this is worth doing?
If I went with a non-flared port, would I have to alter my port length? How much better does a flared port perform over a non-flared port.
Dylan, have you looked around for a subsonic filter yet? I was wondering what is available locally.

Harry.

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#20 of 25 OFFLINE   Dylan SJ

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Posted April 03 2001 - 09:48 PM

Harry: I went past Acoustic Concepts today and he showed me a 4" flared port his neighbour is willing to sell for $A35. It is the same as Adire's product. From your original post you were doing 2 subs though, so you need 2 ports.

I haven't looked for a subsonic filter yet as I haven't decided on the amp, which may have a filter built in. I'll let you know when I do.

BTW Do you have email facilites? If so, email me so we can exchange local information directly rather than clutter the forum.





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