Mod Note: This thread was split from Portable sound system gallery... in the class d forum.
In the meanwhile I tested a few other small (3" or 8cm...) fullrange drivers (instead of the 2" Visaton FR7).
Perhaps I should clear a bit on my methods and equipment. I made another couple of PVC enclosures, this material is not ideal for getting the best results. But the tests are based upon comparison between drivers, and the enclosures I used are about the same (only tweaked the stuffing a bit...). All were tested on AMP32 and AMP9 from http://www.41hz.com on SMPS supply. All drivers were optimized by PLXXO notch filters and run through 1:2/1:4 (switcheable) audio transformers to boost up the voltage a bit from my MP3, MD and CD portable players (and compensate for the loss by the filters). The signal run through both the transformer and filter
has a bit more gain and has much better bass and highs. The transformer is mainly responsible for the bass enhancement, the filter does both (and takes away that mid-high range edge that most fullrange drivers suffer from)... I made two filters, both are adjustable with a potmeter to simply go from "SHOOOOUUUT" to "BOOM~boom~PSS~pss~PSS...:) but one even has switches for two different cap values and three different resistor values added :cool: All in 'mini' aluminum diamond plate chassis (as usual ;)
Good efficiency, but a lot of distortion and pretty 'canny' sound. Even with notchfilters I couldn't manage to get real good sound from it...
But for applications where soundquality is less important a pretty nice driver for what it costs... I do think the foam edge isn't going to last very long (with central heating at home those can pulverize within about six years....)
Quite a revelation compared to the FR8 in soundquality, but the efficiency is pretty low. A heavier magnet, larger voice coil and rubber edge justify the higher price. In fact I think they're better value for money. The one thing that does bother me is that it definately needs a tweeter, the highs are (especially when compared to my next candidate) just not there enough. This makes the sound a bit dull, and on top of that the higher midrange area sounds rather coarse. Overall the FRS8 sounds nicer than the FR8, the whole frequency band under 8K is very clean, flat and shows low enough distortion to listen to for long sessions (but with a tweeter...).
Next up (and the latest I tested) Monacor SPH-30X:
The extra you pay for this driver is payed back in equal amounts of soundquality. The bass is phenomenal (for such a small driver...), it's light (because it has a neodymium magnet) and magnetically shielded, made from very durable materials, shows very litlle distortion, handles quite a lot of power and the efficiency is GREAT! Not even speaking of the very fine high frequency resolution and the good staging that goes with that. Absolutely the winner! :cheers: A lot seems to do with the good construction of the driver, like the rubber edge is really thin and flexible which saves energy I think. The voice coil windings can be seen through openings behind the spider, this driver is very well ventilated. Also the basket is from one piece of steel all around the magnet, large and reliable connections are riveted to it 180 degrees apart with nice looking litz wires going to the voice coil. It all has a slight 'Morel' feeling to it, they also use steel baskets the same way. And last, but not unimportant to me, it looks very good IMHO (no glued wires visible around the dustcap...) An a+ in my book!
Special thanks go out for Planet10 for his great site:
He has put theory on PLLXO filters on this site in a very understandable way. Very nice documentation for DIYers, good work man!
For the record, all this has nothing to do with HIFI! Allthough it comes verdraaid* close!
*Dutch word for which I have no translation that will pass the censoring, though it doesn't mean anything offending in my language...but I think anyone can understand from the context :D
Hmm, maybe the right word is "wickedly"...(the word 'twisted' popped up, which would be the literal translation, but not fit the context....:) )
Oh yes, if you want to know more theory I used to make the notchfilter:
The coils I wound myself (15 minutes per coil with a fixed electrical drill from a large spool of enameled ofc copperwire I have, cores are made from a stack of six plates of steel from an E-I core transformer).
On the Monacor I use a 3K resistor from the source and paralleled a series network of a 154nF capacitor followed by a 97mH coil and a 10K potmeter to ground, don't know if I've done everything right here, but I tweaked it a lot and got to a nice setup for each different driver IMO.
The FRS8 sounded nicer with a 5K resistor from the source, 330nF cap, 110mH coil and also a 10K pot.
For FR8 I'm not sure...:D
By the way, I tested FR7, FR8, FRS8 in both 4 ohm and 8 ohm versions. Nothing really dramatically different here, except for the obvious...
Monacor SPH-30X I only have in 8 ohm version (least distortion, still enough power...)
Look how cute, but there's a beast hiding in there...:clown:
Thanks for the info v-bro! I appreciate it.
The only 3" speaker I'm familiar with is the Tang-Band W3-871s - have you heard those in a similar config?
Hi, no I haven't, very interesting drivers they make, but none of them really seemed to match the profile. They either have phase plugs (which menas dust and water can enter the magnet gap), or they didn't have the nicely light neodyme magnet, or just paper cone...
The price/quality seems very good, for inside use they would perhaps be my choice...
Interestingly enough, these FR8 and SPH30X exhibit the same single sine wave pulse looking response around 3kHz and have a peak in the response around 10kHz. The FRS8 on the other hand has a much smoother response and no peaking at 10kHz. The FR8 and SPH30X are also more sensitive than the FRS8. Judging just from the frequency response the FRS8 should have been the winner. You mentioned that you thought the FRS8 "definitely needs a tweeter" indictaing that, like many, you prefer a rising treble response OR have less hearing sensitivity to higher frequencies. I know I can't hear over 17kHz...
an alternative with good sound is
the FRS8M Visaton, Omnes audio 3.01.
free download plan for two driver:
Bwrx: The FRS-8 should indeed show a nicely flat response, but my experience is they sound quite matte... I confirmed this more or less with a portable spectrum analizer borrowed from a collegue. Or maybe my ears are going down, maybe I should have them tested first :D
The other drivers (FR8 and SPH30X) indeed show some harshness without the filter. The FR-8 is incurable in this IME, I tried many filter configurations.
The SPH-30X on the other hand keeps a high dose of finesse and detail richness in the high frequency range. Though without the filter it sounds overbright and a bit coarse in the higher mids...
The FRS-8M is one of the newer drivers in this size from Visaton isn't it?
Very nice design, 360 degree radiation rules! :cool:
Next thing I was thinking about is to create a subsonic filter to protect the small drivers a bit from the bass peaks...So I'm thinking notch@10Khz and highpass@80hz...
Any ideas would be very welcome...:worship:
Oh by the way, this is what I use on the SPH-30X:
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