Oh, I didnt know getting an account is hard. I know some guys who have ordered a lot of stuff from them. They were the ones who said I should use them and would order on my behalf.
The 18mm ply that is commonly available here is only 7 layers thick. From reading some of your other posts, BB is more like 13 layers for the same thickness. I also recall you saying that you would probably consider the number of layers more important than the actual wood the ply is made from. Apologies if I have misquoted you.
Would you say that a 7 layer ply would still be a better material than similarly thick MDF? If the ply turns out to be void free, I'll purchase it for the external panels and the holey brace. If it isn't void free, I'll purchase 18mm MDF and probably resort to hardwood cross-bracing (having a t brace no further apart than 40mm) as I can't imagine it being a good idea to still use ply if it has loose material in it.
Open to correction.
Blokes from Europe and America have access to products we can only drool over, BB over there means Baltic Birch, over here it means Brace Board, the nearest equivalent I can think of is marine grade Hoop Pine, Gunns ply is hardwood from memory and 3 times the mass of Baltic Birch
I can only agree with you there. To be clear, I meant Baltic Birch, didn't realise that the acronym had a different meaning in Aus.
I just found a distributor in my area that sells marine grade hoop pine ply, I might go and see what it's worth. I have a feeling that the price will scare the living daylights out of me.
I just found a distributor in my area that sells marine grade hoop pine ply, I might go and see what it's worth. I have a feeling that the price will scare the living daylights out of me.
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I feel that I have lost focus on what I was setting out to do, build a cheap pair of subs.
I'll be using 18mm MDF. I'm a novice at speaker building, best that I stick to cheap materials especially if suitable ply is considerably more expensive and hard to come by in Australia.
I'm even thinking I'll use MDF for the holey brace as I will have enough left over from the sheet (I need to buy two 2.4m x 1.2m sheets to make all the necessary panels). Surely it would do an adequate job of bracing?
I'll be using 18mm MDF. I'm a novice at speaker building, best that I stick to cheap materials especially if suitable ply is considerably more expensive and hard to come by in Australia.
I'm even thinking I'll use MDF for the holey brace as I will have enough left over from the sheet (I need to buy two 2.4m x 1.2m sheets to make all the necessary panels). Surely it would do an adequate job of bracing?
Yes mate, isn't it easy to loose sight of your original goal and start to chase perfection??
Use chipboard to keep the cost down, scrounge scraps of MDF and glue them to the chipboard, this will help damp down the resonance, sealed boxes filled with fiberglass and Bonded polyester mat and use software to boost the low bass, use a simple "H" brace from side to side a scrap of hardwood to put between the 2 woofers to make that part of the box stronger and stiffer and use one of the cut-outs to stiffen the back panel.
Manufacturers use all of these methods to keep cost down and if this is a learning process build why not keep to a lower budget, beg and scrounge and borrow until you have learned enough to know what best suits you music listening and your room.
I approve ( not that you need it )
It should work in Troel's box with some tweaking but I suspect it's more suited to the smaller sealed design of the Nebula due to the use of the 2.2mH inductor at L2 which gives large BSC for the lower bass in a sealed design. I also suspect it may be a bit more laid back across the mids (hunch only).
Here's one you can try (even cheaper) using the Nebula crossover schematic reference numbers and values of some of the caps and inductor will be able to be used in Troel's xo if you don't like it. It's similar to the crossover I used in a XT25/18W8531 speaker that worked well.
L1=0.1mH (0R05 - 0R08)
R1=3R9
C1=20uF (parallel 2 - 10uF)
L2=1.5mH (0R3 - 0R6)
R2=8R2
C2=8.2uF
C3 not used
Place 15R damping resistor across tweeter +ve to -ve (parallel)
Tweeter wired -ve polarity
The pic shows the plots for FR and Z.
Another similar design is from Tony Gee.
Humble Homemade Hifi
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Shame as I still have the P-13s/D-27 to do it with, maybe this is where i should be using the M-22 woofer and make it a 2.5 in a sealed box for the bedroom.
Cheers for the help. Are those component values to be used with the Nebula schematic?
I found the Humble Homemade Hifi design as well but its crossover looked fairly complex as well. Also he seemed to place importance of the 7 degree angle which looked like it would be fairly confusing / annoying.
On the Treols cabinet design, what's going on at the bottom with all the red stuff?
I'll probably order my 4 drivers and XO from WES in the new year. Looked like the Nebula design was going to be ~$60 for both speakers, unless I went for the crazy expensive inductors.
I've got the BOM to make the amp as well, haven't priced it up yet but it is all Farnell / Element14 stuff so shouldn't be a problem.
Cheers
That red stuff on the bottom of the cabinet schematic is the crossover components in their own separate compartment. Is this what you meant?
Yes, thanks. I had no idea and wasn't sure if it was some kind of baffling / support. Cheers.
Don't get me wrong as the P13 is still a great driver. The PL series just happens to bring out a bit more mid detail and a 6.5" driver is going to have better bass which is better for a more balanced speaker with a fuller sound such as Troel's floorstander.
The P13 does have good music making ability with it's smooth presentation and in fact I liked it much better than the highly regarded SEAS W15LY001 in a similar design. The SEAS is very detailed and neutral (one of the best I've heard in this regard) but for some reason I did not enjoy the music through it even after heaps of different crossovers trialled.... just wasn't engaging. Maybe extra detail can have it's problems. In the end I sold the SEAS and kept the P13.... all down to personal taste and how you like music presented.
BTW, I have tried the D27/P13 with the 0.5 M22WR lower section of my mains and works surprisingly well. Mine now uses a Scan Speak S2905-970000 tweeter
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Yep... use the Nebula schematic designations but tweeter -ve polarity.
If the tweeter sounds harsh then use L1=0.08mH (remove 5-6 turns from a 0.1mH depending on bobbin size.... we can tell you exactly) and C2=5.6uF as this increases the crossover point and takes more load off the tweeter near it's Fs. L1 needs a low DCR (0R05 - 0R08) as this helps protect the tweeter. 1.5mm - 2mm wire would do the job.... no smaller.
Which amp are you building?
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OK cheers. I'm not quite sure what tweeter polarity is but I'll figure it out between now and then.
Looking to build a LM4780 based PA03 Pavel Dudek's deLuxe Gainclone. Might modify the schemativ slightly since my mates don't think I'll need all the features and because we are DIYing the PCB it might not work with tech we have available. Any thoughts on it
Where did you introduce the M-22? I was thinking of using it quite high about 300/350 given its smooth FR and a baffle width of 280mm
-ve tweeter polarity means the +ve speaker wire is connected to the -ve terminal on the tweeter. This gives us correct phase and summing with the mid woofer and if we don't, you get a suckout (null) across the crossover frequency (see graph).
I haven't built that amp but have built the AudioSector LM4780 which is a nice amp. I ran mine using 25VDC rails (18VAC tranny) which is more tolerant to lower impedance loads and runs cooler. You do lose some power however but there was still plenty for my needs. It did need a pre or buffer section before the input for a full bodied sound. Without this it can sound a bit thin.
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