Recomandation for a cheap midwoofer - diyAudio
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Old 28th November 2013, 02:49 PM   #1
sesebe is offline sesebe  Romania
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Default Recomandation for a cheap midwoofer

I'm trying to fix / improve a 3-way speaker.

I need suggestions for finding a cheap midwoofer who can work between 100 (200) Hz and 7-9kHz. No need to be the best speaker, should be above 86dB sensitivity on sealed box and to be cheap and easy to find.

Box consists of one tweeter, two midbass of 6,5" and a (sub) woofer of 10" placed on side. It is a floorstander.

Tweeter has already changed with SAL DTF 12 and for the bass I only have the measurements made on his vented box.
The impedance of woofer is 8Ω.
The measurements show that will be difficult to use it over 150-200Hz.

Finally I want to get actually a 2-way speaker till 100Hz (maybe cutted at 100Hz) and to extend the range of bass with the vented subwoofer.

I know that the information provided are insufficient to make recommendations but I hope to get some ideas even.

I have no experience with speakers and so I rely on you guys
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Old 28th November 2013, 03:03 PM   #2
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Look for Monacor SPH series .
Maybe they're too good SPH 135 or 165
Check the impedance. Some models are available in 4 or 8 Ω -not the SPH ( only the SPH 30 ) series, which feature some double coil models ( it could be useful if your midranges are 8 Ω and parallel connected = 4Ω and you want to substitute them with a single unit without reworking all the crossover network )
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Old 28th November 2013, 05:11 PM   #3
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Mission cp168 is cheap ~20€. But it wont get to 8k... Not much will, besides a fullrange 6.5"

They were still available at lautsprecher.de last time i looked.
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Last edited by mondogenerator; 28th November 2013 at 05:13 PM.
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Old 29th November 2013, 10:35 AM   #4
tvrgeek is offline tvrgeek  United States
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ses,
What you are asking we really can't answer. You have set constraints that NO driver for any money can satisfy. Why are you looking for a two mid-base system? Why are you picking 7 to 9K crossover? If cost is an issue, use one mid-bass and bring the crossover down to a reasonable point like 2 to 3K.

Full range speakers are not full range and anything resembling sound at 7 to 9 K is mostly cone breakup. Vile expensive things designed to do more than a single driver can do. A mid-bass that can do 7K would be something like the Fountek FE85 3 inch. FR88 better but it costs more than decent cheap 6 inchers like the Silver Flute that will do just fine from 80 to 2K ( with modification) where most any half-decent tweeter can take over. The 3 inch is fine for a desktop, but it won't move the air for a full size monitor unless it was used above 500 or so.
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Old 29th November 2013, 12:41 PM   #5
sesebe is offline sesebe  Romania
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Thank you for feedback.


My question was more theoretical because I had come to the same conclusion like you tvrgeek., but I was not sure.

Luckily I managed to get some reasonable results using the original speakers, lowering significantly the cutoff frequency of the tweeter filter to around 5KHz, and using some notch filtering (paralel with the speakers) for uper side of mid's.
The main problem now are the impedance of speakers that become to low between 800Hz and 5KHz. The mean value of impedance is ~8.2Ω but in this range the lower peak it is around 3Ω.
The measured distorsions are resonable low with a narrow peak at ~5KHz were are double compared to the rest of the band.
For the moment I will stay like this and listen to see if it is need to be changed or not.

To increase the impedance for mid range I tried with notch in series with the mid speaker but the results was not so nice to my ears. Maybe you have some idea how to increase the impedance for this mid band.

Thank you.
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Old 29th November 2013, 02:00 PM   #6
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Most of the impedance issue you have is likely to be the two mids, in parallel. Switching to a single mid would help. But it could also be the multiple notches. Try a single mid, and see what Z does in response.

Of course, you will need to halve/double the L/C to keep the filter slopes and notches. Notch R will need fixing too.
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Last edited by mondogenerator; 29th November 2013 at 02:03 PM.
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Old 29th November 2013, 02:09 PM   #7
sesebe is offline sesebe  Romania
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The mid's are connected in series.

I supose that the impedance problems come from notch filtering because I had no problems until them.

The box it is already made and I can not change it. So I need to live with 2 mid's of 6.5" (are on the same sealed box).

Last edited by sesebe; 29th November 2013 at 02:18 PM.
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Old 29th November 2013, 02:41 PM   #8
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Ah...well if they're in series then it is the notch. Is your notch a parallel tank, running in series with the mid? If so i would try a series LCR, shunting the mids. But you tried that. I'm not sure how well that would work anyway, with series connected mids....

That only leaves TVRs suggestion: lower the crossover to the tweeter at a much lower point, say 2-3k. The mids will sound less directional anyway, and its probably the best idea.
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Old 9th December 2013, 07:26 AM   #9
sesebe is offline sesebe  Romania
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Hello to everyone,

Here are some photos of the final filters that I want to use for my speakers.
Please feel free to comment.
Attached Images
File Type: jpg P1170719.jpg (470.2 KB, 443 views)
File Type: jpg P1170720.jpg (351.5 KB, 423 views)
File Type: jpg P1170721.jpg (411.8 KB, 409 views)
File Type: jpg P1170722.jpg (493.4 KB, 403 views)
File Type: jpg P1170723.jpg (538.4 KB, 386 views)
File Type: jpg P1170724.jpg (439.1 KB, 49 views)
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Old 16th December 2013, 06:07 AM   #10
sesebe is offline sesebe  Romania
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update,

The tweeter was broken, mechanically blocked I work to redesign the filter.....
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