Advice on bookshelf speaker build

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BobtheBuildUps

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Joined 2015
#1
I build a set of 3 way floor-standers a couple of years ago and have not been satisfied with the sound. I built them knowing absolutely nothing about audio; used store bought crossovers without even matching them to the speakers i had (resonance frequency etc) and didn't even buy speakers with the same impedance(8,8,6). After getting into audiophile quality headphones i can see how bad they really are and how much of a waste it is to have decent drivers sitting in them. I am thinking of building a pair of bookshelves as a start and then expand from there.
These are the drivers i will be scavenging out of them.??
Woofer: HiVi D5G
Tweeter: ?vifa d25ag-35-06?

I joined this forum as i could not find all the information i wanted about crossover design and enclosure design.

1) How can i match the sensitivity of a 6 ohm tweeter and a 8 ohm woofer? (woofer being 83db and tweeter being 90db) Would i be better of to buy a 8 ohm tweeter and just attenuate using a calc like the erse one?
2) The woofers sensitivity drops rapidly above 2500hz and the tweeters resonance frequency is 850Hz. If i were to cross them at 2000Hz which is roughly 1 octave above the resonance of the tweeter, would i have to use a 4th order crossover?(according to some threads i have been reading, crossing only 1 octave above fs requires 4th order as 3rd and 2nd will produce distortion?)
3) Can i use a 4th order high pass and a 2nd or 3rd order low pass together?
4) How can i find the perfect volume for a ported enclosure?

Sorry if i used any terms incorrectly i am just a Noob 🙂
 
#2
1) if you design the crossover properly it doesn't matter if the woofer and tweeters impedances are different. The crossover is designed based on the impedance at the crossover frequency (or if you have actual measurements can be optimised further).

2) I'd aim for a 4th order acoustic slope, this will probably be achieved with a 3rd order electrical filter.

3) yes. the imporatant thing is to get the accoustic slope the same. The electrical order (apart from phase issues) does not matter too much, the important bit is to get the acoustic slope for both drivers to be as close to the chosen crossover order as you can.

4) use a simulation program. Unibox (excel based) winisd (exe) boxsim (also an exe and a lot more than just box simulation) are a few.

Also have a read of Allen's sticky thread http://www.diyaudio.com/forums/mult...designing-crossovers-without-measurement.html

Tony.
 
#3
A little homework reveals that the Kevlar HiVi D5G is quite an odd driver. More of a high inductance bass unit in fact.

The tweeter is a fairly regular metal type.

If the bass was better, you could do something like this Michael Chua Robin design:
"ROBIN" (HiVi M5a + VIFA D25AG) Monitors by AmpsLab

I think you must ditch the HiVi in favour of something better behaved. If I was you, I'd look at fixing your 3 way if the bass is something easy.
http://www.troelsgravesen.dk/3WClassic.htm

3 ways aren't that hard with suitably chosen drivers. They all follow the Duelund target slopes.
 

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#4
Hi,

If S7's graph is for the D5G a standard two way is a world of
pain, the midrange is pretty unworkable with a simple x/o.
Fixing the 3 way may be the best idea.

All 3 ways do not follow the Duelund criteria, pointless aside.

rgds, sreten.
 
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#5
Thanks for the reply's.
In response to wintermute, i do know that you can use different impedance drivers together but i was just wondering how to match the "loudness" using a conventional crossover. Also, how would i go about designing a 3rd order electrical filter, using a calculator or program?
In response to system 7 and sreten, what kind of effects does high inductance have? The bass driver from the 3 ways is the hivi D8Gs. Does this woofer suffer from the same problems as its smaller brother? New Zealand has no decent diy audio shops so i have to ship everything in. I am not keen on having to pay double the product price in shipping (parts express). The only places i could actually get anything from would have to be aliexpress or eBay as their shipping prices are pretty low. I don't really want to spend over 500 dollars as i am saving up for a car🙂
Thanks for all the help,

Jeremy
 
#7
Hi Jeremy, Do a search on Lpad's for matching levels. If the drop required is not too much then just some series resistance in the tweeter circuit can also work. The best way to design the filter is with simulation, preferably with actual measurements of the drivers, but you can also use data traced off manufacturers curves.

I'm not sure the d8G is much better to be honest. Not something I would recommend for a first foray into crossover design!!

Tony.
 
#8
wintermute said:
Also have a read of Allen's sticky thread http://www.diyaudio.com/forums/mult...designing-crossovers-without-measurement.html
Click to expand...
wintermute said:
The best way to design the filter is with simulation, preferably with actual measurements of the drivers, but you can also use data traced off manufacturers curves.
Click to expand...

The perceived quantity of sound, the SPL might be directly heard ...
Or, after many years with the same preamp/ amp combo, you'll find how the volume knob reveals the sensitivity of the drivers connected.😎
 
#11
BobtheBuildUps said:
Thanks for all the advice!!
Are the drivers i have bad or just difficult?
On aliexpress i could get a pair of fountek fw168s for a decent price and free shipping. Would these drivers be better for my first project? Are they any good?

Thanks, Jeremy
Click to expand...

Your 8" woofer, the Hivi D8G looks OK to me. It's not QUITE suitable for a two way however, requiring a 2kHz crossover.

So we are back to fixing the three way. Midranges should be efficient and smooth for simple filters. A metal coned Fountek FW168 looks like a similar world of hurt to the HiVi D5G to me. 🙄

The Peerless 830860 Polycone looks like something that will work with little effort. Troels Gravesen uses it in a two way quite comfortably while noticing its suitability for a three way:
Peerless HDS PPB 830860

See if you can find that one. It's not expensive.
 
#12
I couldn't find peerless HDS woofers with a decent shipping price. Ended up being around 90 USD worth of shipping... i hate living in New Zealand 🙁. I have however, found a couple of alternatives with cheap shipping. Are any of these suitable for a first timer?
HiVi M6N or M5N
HiVi S5N
HiVi F5
Peerless SDS 830656
Tang Band W5-704D
Dayton Audio RS150-4

Could i use the M5N instead of the M5A in the "Robin" design you (S7) linked before or would it require crossover modifications?
Are the M5A and M5N the same just with different frames?

Thanks, Jeremy
 
#13
According to Zaph tests (Zaph|Audio) the Peerless SDS 830656, Tang Band W5-704D and Dayton Audio RS150-4 are better in cost/performance terms than the HiVi M5A. I used the Peerless and I think this is a nice driver, but if the price is similar I would choose the TB, just leaving out the Dayton as for this driver you need to lower the crossover point to roughly 2KHz (metal cone with nasty breakup) imposing thus a robust and more expensive tweeter.

Ralf
 
#14
For a suggestion about the Peerless paired to a Vifa BC25TG15 see my thread: http://www.diyaudio.com/forums/multi-way/140231-peerless-830656-suggestions.html. If you want to build that design you can tune to your taste the tweeter level by choosing different resistors. For example a couple of dB more with a 2R7 instead of the 1R8 I used. Resistors are cheap so buy some more values and try. There is also a design by ASE with the same drivers (http://www.speaker-online.de/bauen/BVSAK3R.pdf), the woofer is marked as 830657 but this is an error (it is the 830656).

Ralf
 
#15
Just looking at the datasheets, the peerless, tang band and dayton look the friendliest on your list.

The only thing I don't like about the tang band is the dip starting at 300Hz and ending 5db down at 400 Hz, probablty the bigger problem though is that it doesn't fully recover until around 1500Hz. Other than that I'd say it looks like the best of the three from an ease of crossover point of view.

I'm not sure about the Hivi datasheets they all seem to exhibit the same sort of response, and I wonder if it has something to do with the way they do their measurements, perhaps in 4pi space rather than on an IEC baffle (and then nearfield spliced in at lower frequencies) They just don't look natural.... The datasheet doesn't specify that I can see.

The peerless does have quite a breakup peak at 5Khz that may need dealing with with a notch filter but apart from that looks very good.

Just my 2c worth 🙂

Tony.
 
#17
system7 said:
Your 8" woofer, the Hivi D8G looks OK to me. It's not QUITE suitable for a two way however, requiring a 2kHz crossover.
Click to expand...
Problem? I think the D25 will handle 3rd order 2KHz quite nicely. The crossover point isn't the reason i wouldn't use the D8G in a 2-way, more because the frequency response of the D8G is rough as hell above 300Hz.

Of course, a 2KHz crossover on a tweeter with Fs=850Hz is not the easiest crossover for a newbie to design properly but a 3-way is even more of a learning curve.
 
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