My first homemade speaker full range WAW / FAST

Lorepeo

Member
2016-02-23 10:52 am
Hello everyone, I apologize in advance for my bad English (I'm using an online translator :D).
I would build two Fast full range speakers to compensate, with a subwoofer or woofer, the "few low frequencies" of the full range speaker.
The speakers i would buy are aucharm 5 " (aliexpress).
I think should be a good standard (for my pocket). They are 8 ohm speakers.
I'm totally ignorant in that matter of self-construction so I apologize for the stupid things i'll write.
Which characteristics should have the woofer to be compatible with the full range i've choose? (I will not listen to disco music but surely simphonic music and church organ).
Which crossover or filter should I buy to make a cutoff around 70Hz? (can you tell me one concrete example because the ones that I find in internet have all cutoff around 300hz and so they are not okay because I would lose the beauty of the full range (which frequencies starts from 60hz to 20khz).
My amplifier (by now) is a lepy lp2020a then the cutoff of low frequency I think is also useful for him not to devote too much power for the low frequencies.
I've many more question but i will ask them later.
Thanks a lot
 
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Hello welcome to the forum. There are very many options to build a small speaker system. You will find many ideas here. Depending on what you want and of course how much money you have �� you can do nearly anything. For the very cheapest, you can build with foam board or plastic like xrk971 does, and have full range horns or very inexpensive or very cheap.

I barely know what is FAST, but I do know that doing the subwoofer is the hardest part. Do you have active crossover like mini DSP? That, and having several amplifier channels gives you great flexibility in designing your system.
 
For example, at USA prices at least, you can make a pair of Horn out of foam board with a single drivers that will play very loud down to maybe 200 Hertz or just $100 or so. On the other hand, if you expect organ music and wall shaking bass, you will spend more money and most likely have a subwoofer that you cannot lift by yourself. ��
 

krivium

Member
Paid Member
2009-10-13 2:43 am
Which characteristics should have the woofer to be compatible with the full range i've choose? (I will not listen to disco music but surely simphonic music and church organ).

Well not really easy to answer: it lacks some design goal. Do you want your sub to be ported (bass reflex), sealed (closed box), horn loaded (as suggested by Soldermizer)?

Which spl (sound pressure level) do you want to achieve (approximate average level you usually listen)? Which deepest lowest note you want to hear ( you mentionned organ but you want your speaker able to reproduce an organ full range? If yes this means 16hz lowest note... not easy to reach even for some 15" drivers)? Which dimensions you want the final box to be?

Please specify this and it'll be easier to give you an answer.

Which crossover or filter should I buy to make a cutoff around 70Hz? (can you tell me one concrete example because the ones that I find in internet have all cutoff around 300hz and so they are not okay because I would lose the beauty of the full range (which frequencies starts from 60hz to 20khz).

Well it's not so easy. You can't decide a cutoff frequency only by using the driver bandpass. Other parameters play a role too. You'll not nescesseraly 'loose' the beauty of full range cuting them at 300hz, in some case (if not most) it'll probably be the opposite! But it's difficult to answer without design goal given... And don't forget you can't break law of physic (you can't produce high spl with 1 small direct radiators driver, as you can't reproduce without distortion low end contents).

From what you wrote it seems you want a passive cross over. It can be more difficult and costly to implement than use of an active filter as suggested by Soldermizer (minidsp) but both have pro and cons... Either way you'll probably need to use some measurement microphone (to take measurement and validate choices you are going to make) and how to use them.
 
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Lorepeo

Member
2016-02-23 10:52 am
Thanks for your answer.
Yes I would realize a speaker as much as possible small, with a more complete range of frequency possibile. If possible not active subwoofer.
With my mini speaker amplifier (Lepy lp2020a) is possible the creation of a two-way speaker with a full range and a woofer and passive subwoofer? Or is it necessary that the woofer or subwoofer are active?
The minidsp (i did not know it) seems very interesting but it would be the most expensive part of my hifi so I'll keep it as an option for the future.
I don't repute foundamental to go down to 16Hz but I would simply extend a little below the frequency of the full range starting at 60hz.
I had thought of a one-way full-range but the construction of houses in TL or in Horn scares me a bit '(for its size and for all the resonance parameters, isolation I do not have the technical skills to calculate) so I thought I would fall back on a two-way, exploiting the full potential of the full range and only for the lowest frequency the woofer or subwoofer.
Something like that
Strassacker: Speaker Building, Components

Starting from the full range speakers that are those
Aucharm High Performance 5'' Full Range Speaker Paper Cone Aluminum Bullet&Casting Aluminum Basket 8ohm 30W-inAcoustic Components from Electronic Components & Supplies on Aliexpress.com | Alibaba Group
I would like to chose the correct woofer or subwoofer ed project the case for the speaker.
I hope that is possible (for this forum rules) to post the link to other internet website as i've made; if not i'm sorry and i'll remove them as soon as possible.
Thanks
 

krivium

Member
Paid Member
2009-10-13 2:43 am
Yes I would realize a speaker as much as possible small, with a more complete range of frequency possibile. If possible not active subwoofer.

That's ok. But you'll have to compromise on some parameters: small box usually means low spl and not very much low end.

Why do you want your 5" to reproduce 60hz? It don't make sense to me: i doing so you'll have HUGE amount of distortion and poor output level.

Better to do the same as the link you gave: use of a 8" for low end (you could go easily to 40hz and cutoff at 250/300hz), full range for high freq (typical fast set up).

There is a reason why you can't find example of 5" cut at 70hz: It don't make a valid engineering (objective) or audible (subjective) choice of cut off point for the kind of speaker you want to build.
 

krivium

Member
Paid Member
2009-10-13 2:43 am
May i ask why don't you choose an already done/tried design following your requirements using relatively lowcost drivers and including everythings already done?

There is many example here.

You'll learn a lot in doing that and people could help you understand design choices done.
 

krivium

Member
Paid Member
2009-10-13 2:43 am
Lorepeo, here is a graph to give you an insight of why freq of 250/300hz is often choosen to cross over full ranger and sub. Driver is Vifa Tc9fd, a popular 3.5" full ranger.

http://www.diyaudio.com/forums/atta...erformace-testing-platform-hd-tweeter-raw.png

The plot represent freq range and below that distortion level for differents harmonics (2,3,4,5,6). If you look carefully you'll see that once you are below approximately 300hz distortion level start to rise dramatically. This is somewhat typical of small drivers and 5" does exhibits more or less the same behavior. You should notice too that spl level is quite low (around 70db past 1khz... probably with 0.25watt input for these measurements) and as power increase these figures will too and probably for the worst (and maybe in a non linear fashion!).

As you can see on the freq response graph there is no clues about that. But if you listen to the driver you'll hear that.
If you cross your sub at approximately 300hz distortion for the full range will be kept at minimal and your sub driver distortion should be low too. Overall the sound will be better that your full ranger playing 'alone' and 'really' full range.

Thats oversimplified but it's just to explain you one of the reasons this cross over choice of approximately 250/300hz for fast and why it could give better end results (at least when used as direct radiators drivers).
 
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Lorepeo

Member
2016-02-23 10:52 am
My doubt was born by reading also this forum
http://www.diyaudio.com/forums/full-range/196167-markaudio-fullrange-woofer-6-fast-3.html

The speakers I like (aucharm 5 ") have a good xmax 2.5 mm and a minimum frequency response below 60hz so should already be in a position (compared to other full-range) to play good bassi.
Reading in internet (also on this forum) I seem to have realized that the beauty of the full range and the fact that the crossover does not dirty the sound maybe then it would be appropriate to do so to intervene as little as possible and only where it is needed.
It is not true that the beauty of the full-range sound is expressed on the individual voices and the voices in the scale of hertz is precisely in the range of 300 hz?
Cosa c' nella Musica?

But if you suggest me that best cutoff frequency (for "my" kind of full-range) is around 300 hz also in a configuration that is not a normal two way speaker but a full range assisted (as less as possible) i'll do it in that way.
Some full range speaker for example has higher minimum frequency and smaller xmax (fostex fe126en xmax 0.35 mm and min frequency to 83 hz).

Now it determined that the best cutoff frequency is around 300 Hz, there i answer you:
1) Being my amplifier not very powerful (for now, then maybe I will change in the future) can hold a passive subwoofer or a passive woofer (together with the full range)? and which diameter and characteristics (xmax sensitivity etc) should have the woofer (to be happy with the caracteristics of the full range i'm going to choose?
2) if I had made the cutoff for the woofer (ignorantly) I thought since entering the speaker to split the line into two (a clean that goes to the full range and a filtered at 80 Hz that went woofer) instead if the cutoff to 300hz I do think I have to also filter the full range so I need a crossover that makes the cutoff for both the speakers around that number of hertz (one in-line and two output-line to the speakers), correct?
 

krivium

Member
Paid Member
2009-10-13 2:43 am
I seem to have realized that the beauty of the full range and the fact that the crossover does not dirty the sound maybe then it would be appropriate to do so to intervene as little as possible and only where it is needed.
It is not true that the beauty of the full-range sound is expressed on the individual voices and the voices in the scale of hertz is precisely in the range of 300 hz?

Designing loudspeakers is all about trade off and compromise.
Correctly implemented and specifically choosen for the application you target cross over does not nescessary 'dirty' the sound and as pointed in previous post about distortion of small full ranger they can be a beneficial trade off (even if they are not 'as clean' as no filter at all) once you take the whole picture: distortion is not really what i would describe as transparent or desirable in sound reproduction if your looking for realism.

I won't say that having only one speaker to reproduce the whole frequency range of human voice (being mal or female) is not a desirable feature but from my experience this is not an easy task to reach (you need quite good speaker) and you'll have to give up on some other desirable feature to do that.

For me small full ranger used as direct radiator have other interesting advantage than the one you focus on: used nearfield they're quit good to reproduce a stable imaging for example and they have a natural directivity pattern which i find desirable in this situation. They can usually use small box (if you accept to loose bass capability).

They have drawback too: they can't keep up moderatly high listening level especially if you don't release them from bass duties, they can have difficult reproduction of complex musical section (they are not as precise as some multi way beside the fact multiway use cross over), etc,etc,...

The whole point about FAST design is to use small full ranger in their better spec frequency range (including distortion, spl capability,etc,etc...) and keeping the desirable feature they have and for this you'll have to use some dedicated (sub)woofer(s) for low end reproduction.

I'm not saying that 250/300hz is the 'best choice' for cross over choice: i repeat this is all about trade off and compromise: in using this point you'll probably keep distortion low enough for the full range to perform without colouring too much the sound. It will not create problematic 'lobing' as your driver overall diameter will enable you to keep centre to centre distance of FR and woofer close enough to be < 1/4 wavelength of FC.
This points allow the use of the desirable feature of a 8" (or bigger) woofer: low distortion and enough spl for lower frequency to keep with the FR (including BSC).

As a whole the trade off of using a filter can be considered desirable... :)

You could choose an fc of 80hz too but you'll induce distortion in low frequency range from your full ranger and not make an efficient use of your woofer (most 8" are usable up to 250hz minimum)...

All is about choice, taste, trade off, compromise,.... ;)

I don't know the driver you choose (audiocharm5") maybe it's a great one, maybe not.

My advice about this as you don't have a lot of experience is to stick with a known driver from which other members could give you advice to use it. Don't trust datasheet. At best they re right but most probably they'll be optimistic about spec and as (i suppose) you don't have measurement microphone and software to check you'll probably doing 'shot in the dark' about design of your box and (mostly) your passive filter which could be a nightmare.

About your amplifier (power requirement) it'll depend of your listening habits and choice of drivers.

I repeat the advice i gave in previous post: better to stay with a proven (already existing) design than to go from scratch for a first build. Designing speakers is not easy (even with just a subwoofer added to a FR) as you'll have to take many parameters into account: it could end up being a major failure with money spend.

If you absolutely want to design your own take a look and learn from existing design (the one from Planet10 or ScottMoose or Bob Brines diyaudiomembers come to mind for small fullranger and FAST but there is many other example here and there on other forums) then take the plunge... But don't spend money on something you are not sure will work at the end. My two cents.
 
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Lorepeo

Member
2016-02-23 10:52 am
Ok
Now i write in this thread (because it's "my" specific therad about Fast).
Perhaps (in my idea of speaker cabinet) 12" are too much.
My english is terrible, but perhaps i've understood that you want to tell me that if the full range is a 8ohm also the woofer have to be an 8ohm?

My other option is to buy the aucharm 4" that is a 4ohm (that is a little cheaper) and then i should need to buy a 4ohm woofer?

What do you think about those woofer (in combination with the aucharm 5") that are in line with my budget?
http://www.seas.no/index.php?option=com_content&view=article&id=75:h1224-08-l18rnxp&catid=44:utv-prestige-woofers&Itemid=461

http://www.audio-constructor.com/index.php?main_page=product_info&cPath=1_211&products_id=1793
Thanks
 

krivium

Member
Paid Member
2009-10-13 2:43 am
My english is terrible, but perhaps i've understood that you want to tell me that if the full range is a 8ohm also the woofer have to be an 8ohm?

Your english is not really worth than mine... but people seems really tolerant about that here! ;)

About driver Z (impedance) it's not easy to answer you because it'll depend from the kind of filter you'll use but as a quick answer if you use parallel filter (the most common configuration) it is easier to use 8r drivers as it should give total impedance of 4r which amp usually take care of easily. 2r is a much more difficult load for amp.

Before choosing your drivers for your FAST take a look at that thread where you should find some very usefull informations:

http://www.diyaudio.com/forums/mult...designing-crossovers-without-measurement.html

It'll raise some new questions from your side that's sure but AllenB take care of many problems you'll face and explain them clearly.

:)
 
it is easier to use 8r drivers as it should give total impedance of 4r which amp usually take care of easily.

The filter will keep the total impedance of the system 8 ohm if you use an 8R woofer & an 8R midTweeter.

With a FAST differring impedances are not a problem. If you are going to try to get away with a passive XO, you typically want the woofer(s) to be 3-5 dB more sensitive than the mid-tweeter and you choose an XO point that uses the extra sensitivity to do baffle step. If you use 4 ohm bass and 8 ohm mid-tweeter you can get away with a smaller inductor than if you use an 8R bass (helf the size) and the cap for an 8R midTweeter is half the size of the caps needed for 4R. At the sizes needed for a FAST XO these parts are large.

Things are much more flexible if you bi-amp (and with an XO below 200 Hz it almost becomes mandatory.

When going for a passive XO i have had best luck with 1st order series.

dave
 

krivium

Member
Paid Member
2009-10-13 2:43 am
The filter will keep the total impedance of the system 8 ohm if you use an 8R woofer & an 8R midTweeter.

Oups! My bad.

I gave up on passive filter and gone active for maybe 6 years now and didn't look back at how it worked since, active is so easier to setup and finally (for me) cheaper once you invested in the hardware...

Thanks correcting me Planet10.