830875 enclosure calculations

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race27

Member
Joined 2020
#1
hello all, before i start making sawdust id like to run my design by everyone to see if this should work or tweek my calculations. 830875 peerless in a .83 cu ft enclosure, slot port is 6"w x .75"h x 5.1"long tuned to around 46. i would like to tune it lower but just dont think it will work. what is your opinion, am i on the right track, thanks.
 
#3
When I ran the 830875 driver with a 23 liter box tuned to 46 Hz, I get a response that dips down in the 90 Hz region by -1 dB, then rises back to 0 dB at 50 Hz...

However this kind of tuning can be sensitive to getting the port tuning frequency right... vary it by +/- 5% and see what the effects are.

If you have the measuring equipment to verify your box tuning, this would be nice.
 
#9
Let me fix that for you:

For an interesting implementation of the Peerless 830875 idea, go to a website devoted to sadly-deceased Louis Coraggio by his brother Rob Elder

Veeper TM Monitor Speaker.

We have probably said enough already about the Peerless 830875. I sure don't want to go into it more myself. But a decent driver if properly implemented.
 
#11
race27 said:
hello all, before i start making sawdust id like to run my design by everyone to see if this should work or tweek my calculations. 830875 peerless in a .83 cu ft enclosure, slot port is 6"w x .75"h x 5.1"long tuned to around 46. i would like to tune it lower but just dont think it will work. what is your opinion, am i on the right track, thanks.
Click to expand...

Greets!

Depends on the max power available. A quick sim in Hornresp 'say's that your vent at the 75 W rated power overloads the system with a ~50 m/s vent mach and getting it down to ~20 m/s makes for a relatively huge vent, so recommend shrinking the cab down to ~15.13 L/~923"^3 net with a 3" dia. pipe x 14" L to get it down to ~20 m/s/~45.8 Hz tuning.

You can tune it a bit lower, but you're trading efficiency for BW, so max power capability drops like a stone below Fs, though if hard in a corner it could work out for your app.

GM
 
#12
with some help ive settled on .81 cu ft with a slot .75h x 8w x3.4L and it will be mated to a xt25tg30 or possibly a sb29. starting out with 12db xo at around 2400 will see how it sounds and if i dont like it the slot will be filled in and a round port added as per your suggestions. id like to be able to take it apart but my past experience with using titebond2 once the glue joint dries the wood comes apart before the glue joint gives up assuming a tight fit. waiting on drivers to arrive and i will post my findings and some pics after paint later hopefully not too much later as north fla. has been getting a lot of rain lately. thanks for everyones input and will reply soon.
 
#14
I had the 830874 in a closed box; very good driver for the money for sure. Some like it better than the 830875; others the other way around. I ended up with a Zobel and a notch for the peak at above 4 KHz then a first order LP at about 3300Hz. If you cross lower than that with second order; the notch may not be necessary but the Zobel still may be required. These are very similar performing and sounding drivers and worth the extra effort and expense of a sophisticated X/O. I have now moved up to Satori and won't go back to anything less (except in the case of a budget system for someone else). Both of these Peerless are worth getting a decent tweeter; don't go "TOO CHEAP" on a tweeter choice here.
 
#17
drivers (830875) were chosen based on so many good reviews. the tweeters are already on hand and well broken in. most everyone has different opinions on what sounds best and no 2 people are alike so with that i prefer the sb29 overall over the xt25 but for pure sound prefer the xt25. i can live with the off axis of the xt25 and the xo will be just a starting point. when listening to new tweeters i prefer to listen at very low power with no xo to see where they like to operate and how they behave. i wish oldspeakerguy could have been my name but he was just way ahead of me. over the years ive grown less and less tolerant of 2500-4k. it just works on my ears so xo points may very well shift to reduce that and in my opinion crossing the tweeter higher usually helps in more ways than one. just finished the enclosures and its pouring rain again so no painting till later.
 
#19
if a smaller driver might work better what do u think of the sb13pfc25. ive not worked with it yet but will in the near future. the only smaller driver i have on hand that i really like is the morel mw113,had it layin around for years and works really well but just doesnt go very low in a 2 way.
 
#20
Well, by going smaller still, you're shifting the tonal balance higher, raising the low corner/tuning [Fb] to maintain it as best we can. This in turn affects tuning [Fb].

With both drivers the pistonic limit is dictated by its 1+" VC size, which limits the upper end: ~13543/pi/1+ = ~4300 Hz, so more math later this means the lower corner is raised to ~270 Hz, hence tuning shifts up to ~67.5 Hz.

In theory, the SB needs a stronger motor [lower Qt], so it can be tuned proportionately higher than the 6"at high SQ, so if tuned to ~67.5 Hz, then damping it flat may be required depending on actual specs and how it sounds to you.

Regardless, since you have one, might as well try it, though in theory the 6" is preferred. That said, since this is old age related, the 250 Hz low end will probably need to be shifted up to as much as 500 Hz over time like some of my older friends [and even some younger] have proven.

GM
 
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