Quick question guys.
I can purchase 25mm (1") thick MDF for roughly the same price as 18mm (~3/4") Ply. I'm not sure what sort of ply it is, all I can say is that it looks like it has no voids on the edges. I can also purchase 3/4" MDF if that is better suited.
What would people recommend? These speakers will never be carted around, so weight isn't a problem.
I can purchase 25mm (1") thick MDF for roughly the same price as 18mm (~3/4") Ply. I'm not sure what sort of ply it is, all I can say is that it looks like it has no voids on the edges. I can also purchase 3/4" MDF if that is better suited.
What would people recommend? These speakers will never be carted around, so weight isn't a problem.
You have to make up your own mind on that one, we ALL have different ideas on what is best, but if the ply isn't guaranteed "Void-free" ie: Marine grade; then I would use MDF and use 18mm BUT I would laminate two layers together for the front baffle.
Inside; the panels can be deadened by using the cutouts as is or cut in half and glued if you are not using a double holey brace.
Check out the scraps bin too, you may be lucky and find some ply to use as a decorative front panel.
If cost is an issue use chipboard and scraps of MDF as resonance damping,
Inside; the panels can be deadened by using the cutouts as is or cut in half and glued if you are not using a double holey brace.
Check out the scraps bin too, you may be lucky and find some ply to use as a decorative front panel.
If cost is an issue use chipboard and scraps of MDF as resonance damping,
Forgot to mention. I came across a second hand amp yesterday that I couldn't pass up. It's just a Sherwood RD-6613 receiver, less than 6 months old, perfect working order (just missing features that the original owner wanted) $50. It's practically brand new. If it had a bi-amp mode, it would of been ideal but it doesn't seem to have one. Maybe it has a dual stereo mode, I haven't checked.
He paid roughly $400 for it, sold it to me cheap as I have done a few favours for him over the past 12 months.
Its specifications state that in stereo mode, it provides 2x100W into a 6 omh load (6 ohm being the minimum it can handle safely). For surround mode, it states that it can send 125W to the fronts, centre, or rear speakers. I'm not sure whether that is nominal power or peak.
As far as I'm concerned, I have a couple of options in regards to what I will do with it.
1. I could turn around and sell it for ~$200 which I will then put towards another gainclone to power the subs.
2. I can try and use it to power my subs despite it being an amp only suitable for driving 6 ohm loads and above. Considering I don't need to drive these subs overly loud, maybe I can wire them in series for a 16ohm load. Maybe I'll see how it handles a 4 ohm load, etc. http://www.diyaudio.com/forums/multi-way/110496-4-ohm-speakers-6-ohm-amp-newbie-question.html
Also, just as I was finishing this post, something else turned up at my door.
At the very least, they look better than I expected for what they cost.
He paid roughly $400 for it, sold it to me cheap as I have done a few favours for him over the past 12 months.
Its specifications state that in stereo mode, it provides 2x100W into a 6 omh load (6 ohm being the minimum it can handle safely). For surround mode, it states that it can send 125W to the fronts, centre, or rear speakers. I'm not sure whether that is nominal power or peak.
As far as I'm concerned, I have a couple of options in regards to what I will do with it.
1. I could turn around and sell it for ~$200 which I will then put towards another gainclone to power the subs.
2. I can try and use it to power my subs despite it being an amp only suitable for driving 6 ohm loads and above. Considering I don't need to drive these subs overly loud, maybe I can wire them in series for a 16ohm load. Maybe I'll see how it handles a 4 ohm load, etc. http://www.diyaudio.com/forums/multi-way/110496-4-ohm-speakers-6-ohm-amp-newbie-question.html
Also, just as I was finishing this post, something else turned up at my door.
At the very least, they look better than I expected for what they cost.
It was a bit silly for me to ask that question considering the differing opinions on the topic, I don't know what response I expected to get, haha. I know planet10 generally stays clear of MDF. I'm sure he has his reasons so I wanted to try a plywood enclosure but as you've mentioned, I have no reason to believe that the plywood I can purchase is guaranteed to be void free, MDF would be the safe bet.
I do like the thought of 25mm panels, but I had better do a bit more searching on here to see if it is really worth it. I may be able to opt for a simpler cross-brace system if the box has thick walls. Otherwise, 18mm MDF is the default choice (with a doubled up baffle).
If you try and drive the woofers flat out you will probably trip the protection circuits ( if it has any ) but it will drive a nominal 4R load, the Jaycar woofers can't handle even 80 watts anyway so it really is a moot point.
The pair may be able to handle the peaks of 80 though, thermal isn't the issue here it's excursion and excursion increases rapidly if you are going to use even a little bass boost down below 30Hz
The pair may be able to handle the peaks of 80 though, thermal isn't the issue here it's excursion and excursion increases rapidly if you are going to use even a little bass boost down below 30Hz
I'll just have to get my hands dirty and see how I go. I can't turn my gainclone much further than halfway whilst remaining comfortable. I doubt I'll be pushing the subs hard either.
The amp states that it is suitable for up to 16 ohm loads. Would you even entertain the idea of running the woofers in series, would there be negative effects? As the amp is not providing the same power into the speakers, I'd assume that volume would be decreased, by how much I have no idea.
The amp states that it is suitable for up to 16 ohm loads. Would you even entertain the idea of running the woofers in series, would there be negative effects? As the amp is not providing the same power into the speakers, I'd assume that volume would be decreased, by how much I have no idea.
So does that mean that the woofers are wired in parallel with in their boxes, but the negative terminal from one box goes to the positive terminal of the other box before making it back to the negative terminal of the amp?
Gunns timber yard in Launceston has 1" MDF for ROUGHLY the same price as 18mm ply, they weren't exactly the same. I've lost the piece of paper I had written the prices on, but for either type of wood, it was between $70 - $80 for a piece that was 2.4m long by 1.2m wide (or it could of been 1.6m, can't remember).
You could try Gunns in Melbourne, but you guys should have far more options than what I have on this little Island State.
Whoops I left out a full stop
I meant that you should wire the 2 woofers inside the box in parallel but driven by the separate amplifier ( Bi-Amping )
I will try that if this receiver allows me to use the surround channels as additional stereo ones. I have a suspicion that it won't have that functionality.
Look at the inputs you have 6, LRC, Sub in, RR & RL You have 5 speaker terminals plus "Sub out" I would be willing to bet that the pre-amp in the receiver can handle it, just send the LF to one pair and the Mid/high frequency to another pair and just run it. Splitting the signal into the bands is the harder part of the equation
Oh, ok. Light bulb just lit up (albeit dimly)
Going back to what was discussed earlier, maybe I can then feed the "sub out" from my sound card and split it with a Y-cable.
When you say bi-amp, you are talking about still having the woofers wired in parallel rather than having a separate channel for each. Is this because I should be thinking about the twin 8" woofers as one unit as there is no XO separating them to speak of?
Going back to what was discussed earlier, maybe I can then feed the "sub out" from my sound card and split it with a Y-cable.
When you say bi-amp, you are talking about still having the woofers wired in parallel rather than having a separate channel for each. Is this because I should be thinking about the twin 8" woofers as one unit as there is no XO separating them to speak of?
Well if using a "Y" cable there is another possibility if you want to build 4 boxes, use 2 "Y" cables to give 4 inputs to the amplifier then the amp is driving a nominal 6R load and you get +6dB twice, there are benefits to this arrangement as the woofer boxes are half the size and easier to place, how-ever this depends on the XO frequency OK if low (80 Hz ) but not so good as XO approaches 150Hz
It's a 5 channel amp. Run it in 5-channel stereo and driver each woofer with its own amplifier.
... or, specs say it has 5.1 channel direct inputs... just bang the outputs of your XO in there.
dave
... or, specs say it has 5.1 channel direct inputs... just bang the outputs of your XO in there.
dave
Good 18mm ply will have it all over 22mm MDF (and your back will thank you), If the vendor can't tell you, have him rip a piece in half because he should know.
dave
As much as I love the little reference D27/P13, I'd go straight to the XT25/PL18 as it's less compromised especially in bass and mid detail. As good as the P13 is, you can't dredge any more bass or open up the mids more due to the polypropylene cone. The XT25/PL18 is a speaker that will do you more long term and good bang for buck (not much more in driver cost).
If you want to learn by playing with the crossover for this speaker, then try Ken Perkin's Nebula crossover first before building Troel's crossover. I feel Ken's would do the job just as well and is less complex and cheaper.
Parts Express Nebula project
With Ken's crossover you can play to your hearts content with L2, R1 (keep > 4R7) and C3 to learn what changes to components effect the sound. Leave all other values the same.
L2 smaller gives more mids and less BSC (larger visa versa)
R1 smaller reduces tweeter padding (larger visa versa).... keep above 4R7
C3 smaller increases the tweeter xo point (larger visa versa)
Listen without the zobel (R2, C2) on the woofer to hear the difference on the filter without impedance correction.
It's an AR series xo and very easy to tweak and play with.... good learning tool.
Wow excellent, I'm quite surprised by this answer . I'll price up the crossover and will order in the new year. I take it the cross over would also work in the Troels box then? It also has a much smoother impedance response than the Troels XO.
By the way for other Australian builders, WES is much cheaper than speaker bits. My P13 + D27 was going to be about 33% cheaper at WES.
Thanks for the help, much appreciated.
Thanks for the guidance. Tonight I took the sub-out from the PC and fed it into the front-right external input on the receiver. I configured the PC as best I could with the default driver software and connected an old speaker I had lying around. It successfully sent only low frequencies through the receiver.
So I think what I'll try and do is split the sub-out into 4 identical feeds and connect it to 4 separate external inputs. This will be the initial design which I will build on. I will build an active XO and most likely a linkwitz transform filter later on.
Thanks for the heads up.
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