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Old 5th November 2012, 09:22 PM   #11
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hi all
well ive been busy
but we have a problem ,speakers of this size should make bass !!!!

but its missing no bass
not sure what is happening or where to start , i have only listened to one speaker so far as the other one is yet to arrive
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Old 5th November 2012, 11:45 PM   #12
GM is offline GM  United States
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Well, most times it’s due to one or two things or a combination of both when HF horn coaxes are involved.

First, and the most common is that any air leak, even a tiny one, pretty much negates any cab loading, especially a MLTL, tuning it up very high.

The other is that the HF horn is much more sensitive than the woofer, so must be attenuated considerably to tonally balance it in room to the woofer.

Anyway, ignoring any room gain, there should be solid bass to the high 30s once dialed in.

GM
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Old 6th November 2012, 12:07 AM   #13
IG81 is offline IG81  Canada
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Great job, they look good! Glad to see other people are making cabs larger than the kids!

The 212 comes with a crossover from GPA right? I don't know if it's correct for you baffle width.

IG
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Old 6th November 2012, 12:49 AM   #14
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Your port is looking small and short.
I want this USA piece to work, by the way. Otherwise, offshore. Some more.

Last edited by phivates; 6th November 2012 at 12:52 AM.
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Old 6th November 2012, 02:27 AM   #15
GM is offline GM  United States
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Hmm, my monitor is all but dead and can't even see the port, but if it's 3" instead of 6" diameter, then even if airtight, the tuning will be around an octave below Fs, which would equate to no bass also unless corner loaded.

GM
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Old 6th November 2012, 05:31 AM   #16
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Hi guys
sorry about the late reply my internet has been down

the port is 100mm x 19mm so should be close , i was also wondering how the crossover would work seeing as the baffle is very wide compared to what gpa would have set it up for so maybe i need to adjust the lpad/resistor to suit

playing them on the ground before i mounted them reminded me very much of my lowther dx2 in that they are very detailed but bass shy and may perhaps need to go in a ported cab designed with a deliberate 2 to 3 db hump in the lower bass to balance out the presentation

a quik calk works the internal volume out at 206 litres after driver and braces and i would have a few air leakes as suggested by gm

aside from the bass i was a little shocked at the size once built but i,m getting used to them
Sheafer
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Old 6th November 2012, 08:34 AM   #17
Zen Mod is offline Zen Mod  Serbia
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I think GM's R for port is semi-diameter , so it needs to be D=6"=152,4mm

most probably that's the reason for missing bass

let GM confirm (again)
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Old 6th November 2012, 08:45 AM   #18
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Thanks zen mod
i would be wrapped if its that simple
aside from the lack of bass they sound promising

cheers
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Old 6th November 2012, 09:11 AM   #19
GM is offline GM  United States
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Greets!

Bummer, I’m that way a lot with ‘customer no service’ AT&T, but my only other option AFAIK is $#!% Comcast at a much higher cost, so screwed once again by big business.

The XO point is high enough that baffle size should have virtually no impact on baffle step loss since the WLs involved are shorter than the driver’s diameter.

100 mm = ~3.937" diameter, so is about the size one would try if the speaker was positioned hard up against a rigid/massive corner like in basement, which is a bit lower than I would normally recommend tuning this driver, so still very bass shy even if no leaks.

6" = 152.4 mm and if you wanted to add a bass 'hump', then a 9 - 10" [228.6 – 254 mm] diameter is required, increasing tuning up around the GPA reflex tuning, ~defeating the point of using a MLTL loading beyond getting the driver up to ~ear height, though its much larger Vb would give it more bass ‘thump’ than the reflex.

For those folks wanting the vintage Altec mid-bass prominent ‘West Coast Sound’, this is the way to go.

GM
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Old 6th November 2012, 09:19 AM   #20
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Thanks GM
i just finished sealing up any leakes that were present and will cut the port larger tommorow to see the effects

what would be the equivilent slotted port size and is it just a matter of H x W of the slotted port to equal a round port

many thanks again for your help

Sheafer
forgot to ask ,regarding stuffing is the top half of the cab loosley stuffed a good start or would you suggest something else

Last edited by slr 5000; 6th November 2012 at 09:22 AM.
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