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Old 25th May 2010, 07:52 PM   #1
Havoc08 is offline Havoc08  Denmark
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Default Iphone speaker - help needed :)

Hi all,
As my little sister just had her house turned upside down by thieves who stole everything including the homemade iPod speaker I made her, I would like to make/give her a new one .

the old one ended up quite nice and was based on a pair of rainbow slx 230 speakers and an amp32.

I would like to jump into doing a stereo 2 way from scratch and have many ideas, but avg. theoretical knowledge at best.

The basic plan is as follows:
A stereo 2-way Ipod/Iphone active speaker

Tweeter: Vifa XT25SC90/04 Zaph|Audio

Woofer: Dayton RS125S-8 Zaph|Audio

LR 12dB filter around 2-3khz


Amp: Tripath 41hz amp32 or amp4.

Dock: Homemade or stripped dock integrated into speaker.


SO... what do you think so far? The speakers are primarily choosen based on zaphs measurements (relying on the rs125s being similar to its brother rs150s).

Having never done a filter before I'm comming up short here (but hoping to get some help from you guys ).

I presume I need in the filter at least:
The LR 12 dB low pass for woofer
LR 12 dB high pass for tweeter
Impedance matching
Gain/SPL matching (L-pad?)
Damping of impedance at x-over frequency
Zobel?

Any help is highly appreciated
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Old 25th May 2010, 08:10 PM   #2
Havoc08 is offline Havoc08  Denmark
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Unless anyone argues against the RS125S driver, the box would be 2 chambers of 10,6L (excluding port and driver displacement) and a 10,6cm long 4,7cm dia. port tuning it at 58,7hz according to winisd.

BTW should you also subtract the port volume from the total volume as you do with the driver?

Zobel: R = 7,88ohm C = 11,61uF

High pass @ 2500hz: C1 = 10,3 uF L1 = 0,4mH
Low pass @ 2500hz: C2 = 5 uF L2 = 0,8mH

But this is all based on published specs (kind of a no-no, but have no way to measure the unites).

So far I am curious if the zobel resistance affects the filter values as these are based on the Re values as used here mh-audio.nl - Home
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Old 25th May 2010, 09:57 PM   #3
Havoc08 is offline Havoc08  Denmark
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Old active iPod speaker
Click the image to open in full size.

Click the image to open in full size.

She had a red and black iPod at the time.
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Old 25th May 2010, 10:15 PM   #4
Havoc08 is offline Havoc08  Denmark
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Just noticed that the RS125S has a fairly high Fs so that probably won't work. I found the RS150S in another shop so it is either that or a peerless HDS woofer 830860 - Peerless HDS-134PPB PPB diaphragm, 26 mm coil, AL - Europe Audio or 830991 - Peerless 5.25'' HDS-134 driver with glass-fibre cone - Europe Audio
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Old 26th May 2010, 06:26 AM   #5
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I'd model them both in winISD, see what does best in a fairly small box.
The Tang Band 5" subwoofer might be of interest. Cross it over to a 4" mid and tweeters. W6-1139SH - TB speakers 5.5 inch - Europe Audio
It's effciency is pretty low, but it does extremely well in small boxes.
Down firing sub, with stereo mids and tweeters?

It's another option.

Chris
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Old 26th May 2010, 07:30 AM   #6
Havoc08 is offline Havoc08  Denmark
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Hi Chris,
I considered a 3-way, but regarding price and complexity I settled for a 2-way. Inherent to the ipod speaker design stereo imaging is minimal and she doesn't listen to bass heavy music, so the primary concern is SQ and reasonable size.

Appreciate your input though... you shouldn't by any chance have an oppinion on filter design for any of the drivers I mentioned earlier?

The RS125S is modeled with a F3 around 40-50hz which is way below the drivers Fs of 86 hz. I believe I read somewhere that above Fs the driver is controlled by the amp and below Fs the driver is controlled by the suspension and at Fs there is very little control.

Last edited by Havoc08; 26th May 2010 at 07:32 AM.
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Old 26th May 2010, 07:47 AM   #7
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[QUOTE=Havoc08;2198775
I considered a 3-way, but regarding price and complexity I settled for a 2-way. Inherent to the ipod speaker design stereo imaging is minimal and she doesn't listen to bass heavy music, so the primary concern is SQ and reasonable size.
[/QUOTE]

I'm surprised that that line of thot didn't take you to a full-range. The Mark Audio CHR-70 or Mark Audio/CSS EL70 would fill the bill nicely. 8 octaves + in a small box (9 in a bigger one). no XO, CHR can go sealed which makes it really simple. They both sound really good.

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Old 26th May 2010, 08:42 AM   #8
Havoc08 is offline Havoc08  Denmark
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Hi planet10,
I considered a fullrange as I have made some B3N zaph fullranges, but they are limited in sub 100hz bass and SPL.

The reason I didn't go with the mark audios was zaphs comment on the optimal size for a fullrange "You'll never find me running larger full range drivers because I think they generally have too many problems that degrade the sound. But the 3" wide range is another story - they are large enough to blend well with a subwoofer, but small enough to have high frequency extension and off axis response that doesn't stink. 2" drivers are too small, with poor low end extension, distortion and power handling problems. With those you end up with the typical "Blose" sound - no midbass, and a sub that's easily locatable due to a crossover that is too high. 4" or larger drivers can integrate well with a sub, but lack high frequency resolution, have terrible off axis response and have breakup nodes too low in frequency. That leaves us with 3" drivers, the magic size. ".
Also that I would like to learn to make a x-over myself and understand why the decisions are made in different filter types
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Old 26th May 2010, 03:50 PM   #9
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Hi,

The idea I had in mind for the 2.1 system was similar to that of the B&W Zeppelin.
How about a pair of 3" drivers, with a subwoofer?
The reason I'm pushing the subwoofer - if you have one end of the frequency range, but not the other (provided, of course, you have the midrange), it sounds awful. That's why the old speakers, while limited at both ends of the frequency range, still sound good. However, I find it difficult to listen to a 3" driver alone. There simply isn't enough bass (this seems to be emphasised by the presence of the treble), so the whole experience isn't as good.

If you have the option, go for an active cross-over. This makes component price much lower.
I'd pick 4th order for the full-range drivers, and 2nd order for the sub, around 150Hz.
The reason - the steep crossover on the full-rangers mean they won't hit excursion limits (2nd order on full-rangers isn't enough. I know this from experience.) 2nd order on the sub so it can re-enforce the lower midrange a little (can be lacking in small-driver systems).

Anyway, these are just my opinions.
Chris
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Old 26th May 2010, 04:11 PM   #10
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Quote:
Originally Posted by Havoc08 View Post
zaphs comment...
Also that I would like to learn to make a x-over myself and understand why the decisions are made in different filter types
Wanting to learn XOs is a good reason, what Zaph says is not.

I'm with Chris. If you really want an XO, they are best really low, but trying to craft one for a tweeter/midbass -- the worst place to put an XO -- is going to teach you a lot more. I just gave up on them.

dave
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