New Fostex fullrangers are in at Madisound

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#141
Aha another clue. Thanks GM.

I looked up T/S max flat alignment and found several articles that I will need to read. It looks to me like the TS max flat alignment is just beyond critically dampened. The others look like under-dampened systems and get progressively worse as dampening goes down.
 
#142
TheGimp said:
As a general guideline, at what volume is it necessary to switch from 12mm to 15mm plywood?
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My immediate response would be "probably around 4-5 liters" - some of our very early larger ( ~13 L) builds for FE127E were with 12&18mm, and even with extensive bracing, they were a bit ringy. The smaller enclosures ("millies" & "micros") have much smaller panels, with corresponding higher resonance frequencies that are not so easily excited.

We elected to standardize on 15mm for economy of scale, with 18mm for baffles on the "primes" to allow for deeper rebates required for flush mounting of drivers such as Mark Audio/Alpairs, as well as deeper chamfers. Many of the smaller designs don't require a full sheet, so the unit cost for materials isn't all that high.

I've got 12.5mm I can use for all but the front, and can pick up 17mm for it. Locally there are no options between 12.5 and 17.5mm
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Which design are you considering? IINM all of Dave's recent drawings have been dimensioned for 15&18 or even all 18 - certainly the case for the Fonkens Jon and Odougbo recently built.
 
#143
I'm trying to design the speakers myself using the general form of the Fonken as a guideline. I'm shooting for right at 9L internal volume as that seems to be the optimum.

I used the Onken calculator to get me started, then used HornRep to further model volume and duct tuning with the parameters from the Fostex data sheet for the FF-WK series.

I fed the output of HornRep into Akabak to tweak further.

From there I am using a spreadsheet to calculate internal volume from the desired volume plus brace displacement, speaker displacement, etc, and calculate dimensions using the that volume with the golden Ratio as multipliers.

Then, the spreadsheet adds wall thickness, port thickness, etc, as an adders to get final dimensions.

I finally located a local source for Baltic Birch at lunch time today. They carry 1/2" (12mm) and 3/4" (17mm) plus some lesser thicknesses (1/4"?) I didn't look at closely. Available sheets are 30" X 48" and 30" X 24".
 
#144
TheGimp said:
I'm trying to design the speakers myself using the general form of the Fonken as a guideline. I'm shooting for right at 9L internal volume as that seems to be the optimum.

I used the Onken calculator to get me started, then used HornRep to further model volume and duct tuning with the parameters from the Fostex data sheet for the FF-WK series.

I fed the output of HornRep into Akabak to tweak further.

From there I am using a spreadsheet to calculate internal volume from the desired volume plus brace displacement, speaker displacement, etc, and calculate dimensions using the that volume with the golden Ratio as multipliers.

Then, the spreadsheet adds wall thickness, port thickness, etc, as an adders to get final dimensions.

I finally located a local source for Baltic Birch at lunch time today. They carry 1/2" (12mm) and 3/4" (17mm) plus some lesser thicknesses (1/4"?) I didn't look at closely. Available sheets are 30" X 48" and 30" X 24".
Click to expand...


FWIW, I'd stick with the 17mm for all - I'm pretty sure a single 30x48 Sheet would be enough for the dFonken125 (had to look that up), either the rectangular or trapezoid shaped
 
#146
It might have been, but I wrote 17 when I copied the data from the sticker. I didn't take my caliper with me.

The birch finish plywood I measured at Lowes and Home Depot varied considerably (over 0.4mm), but wasn't baltic birch.
 
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#149
giantstairs - I quite like my TAP3116 (Yuan-Jing kit version) on everything I've fed it into so far - Fostex FF85,105 & 165WK, FE126EN as well as at least half a dozen models of Mark Audio. The most recent CHS70 is one to keep an eye open for, I much prefer it to the CHR70.3, and might suggest it a very competent candidate for someone on a budget tighter than the A7.3 would permit.

Of the Fostex drivers listed above, the only one I've not heard in one of the FH models is the 105 - those were in the Woden Vampyr, and maybe one of the BabyLabs ( it gets hard to remember after a while) . If you have the floorspace, the 165WK in FHXL is very impressive
 
#150
giantstairs said:
I'm not really clear about damping factor so was wondering if there were any opinions on how the FF165wk would work well with a lm3875 gain clone or tpa3116d2 amp or really needs a tube amp or current source to shine?
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Drivers with < a ~0.403 Qts such as this driver has [if the published specs aren't too far off] ideally needs enough series resistance [amp + wiring + any added filter] to increase Qts to a ~0.403 Qts' for a max flat impedance vented alignment [Vb = Vas, Fb = Fs], so above this Qts' value one ideally needs to use some form of TL and below it, a tuning > Fs, though if max bass efficiency is desired with a tube amp, then tuning to Fs is a good plan.

GM
 
#151
Thanks Dave and Chris. I will be replacing my damaged FF165k in a BIB with the newer model and was hoping it would work better with a chip amp, tpa3116, or even a Pass amp camp amp. I found the older FF165k to sound harsh and bass shy (even in this large cab) with these amps. With the F2 it really filled out and became a bit of a bass monster (relatively speaking).

Chris, I've had a different experience with my unmodded Tpa3116 (yuan-ging blue/black) finding it almost unlistenable with my FF165k, Fe108ez, and just ok with my CHR-70s. 😕

I am hoping the FF165wk fares better as I can't justify buying another amp (can you ever?), or bringing my F2 stovetop oven home with my 2 small boys. I have found the APPJ PA0901A on Amazon.es for 200€ but again... :no:
 
#152
GM said:
Drivers with < a ~0.403 Qts such as this driver has [if the published specs aren't too far off] ideally needs enough series resistance [amp + wiring + any added filter] to increase Qts to a ~0.403 Qts' for a max flat impedance vented alignment [Vb = Vas, Fb = Fs], so above this Qts' value one ideally needs to use some form of TL and below it, a tuning > Fs, though if max bass efficiency is desired with a tube amp, then tuning to Fs is a good plan.

GM
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Thanks GM! I will need to study your post!

I was hoping to throw these right back in to my BIBs calculated for the older model. According to the newer specs the cabs will be a bit small. I was hoping with the lower Vas it would require a smaller cab but the Qts has gone up quite a bit. And it looks like some series resistance will raise it higher still. My cabs are built to a line length of 168 (40hz tuning) with a Sm of 94 sq. in.

I saw a pencil type enclosure you drew up for the FF165wk and that looks to be a good option, but having 2 corners available and the cabs already built, I will try the BIBs first. The ceilings are a bit high for optimal loading so another option would be find some legs and flip them over to try to get some extra gain, although this will place the drivers too low for my taste.
 
#153
You're welcome!

Yeah, until Vas gets quite large, Qts dominates. Regardless, if it was designed using my calculator, then there's plenty of flexibility built in for corner loading since I allowed for floor loading them, so will be surprised if it doesn't do well enough. Please let us know for sure though!

GM
 
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