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Old 02-15-2022, 12:43 AM   #1
momaka
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Talking Philips F9217L-50R speakers – build quality impressions and DIY surround repair

More Lo-Fi speakers and another DIY surround repair. The patient this time: a pair of Philips F9217L-50R speakers from a budget Philips rack/component system from the ’80’s. The system belongs to my brother in-law… or actually his parents. However, they didn’t want it when they moved houses and he liked it anyways, so he ended up keeping it. It’s a pretty cool-looking vintage system with a wood/veneer cabinet and shelves for records and cassettes. Unfortunately, I didn’t get a chance to take a picture of it or get the model #’s (but maybe next time I visit, if anyone is curious?)

My brother in-law said the speakers worked but were making rattling noises. So he ended up connecting the system to their living room TV’s sound bar (plus, my sister didn’t like how much space the speakers would have taken anyways.) Thus, the speakers were put in storage, as my brother in-law thought it would be shame to throw them away… but really couldn’t give them away in their current condition either. And he knew he probably wouldn’t ever get to use them too. So he asked me if I wanted them.

I don’t really need any more speakers, but I really dislike broken stuff – especially when it’s something fairly easy to fix. Based on his description of the problem, I pretty much knew I’d be dealing with speakers with rotten foam surrounds. The question was whether they would be worthy of a proper surround replacement job, or if I should just McGyver them like the Boston Acoustics HD8 speaker. So I decided to look at their build quality first and then decide on that.

And here it goes, first let’s see the speakers on the outside.
Philips F9217L-50R speakers (1).jpg

Philips F9217L-50R speakers (2).jpg

The boxes were in excellent condition and the speakers themselves look very presentable.

Next, a shot of the label, which shows they were Made in Belgium!
Philips F9217L-50R speakers (3).jpg

Even the power rating seems sensible at 40 Watts (RMS?) and 70 Watts P Max (which I can only assume is a PMPO rating.) The woofers are 8”, so that’s probably not terribly over-rated as I’ve heard (pun intended) some component system speakers can be.

OK, let’s get the front cover off!
Philips F9217L-50R speakers (4).jpg

Philips F9217L-50R speakers - woofer driver (1).jpg

Surprise, surprise! – Rotten foam surround on the woofer. But hey, apart from that, everything else looks and works great. The soft dome tweeter actually appears to be of decent quality, so these might even sound OK in the midrange and treble frequencies. Beware, though! There is a “Frequency Curve” diagram on the front – often a hint that one would be dealing with cheap(er)/budget/Lo-Fi speakers.

Philips F9217L-50R speakers (5).jpg

OK, let’s take out the woofer and have a closer look.
… Ah, but wait, I need to heat up the soldering iron first, because… soldered connections.
Philips F9217L-50R speakers - woofer wiring connections [rszd].jpg

I guess ain’t nobody got time for crimp terminals here. But that’s OK, I don’t mind soldered wires. Also, take note of the blue Philips axial capacitor. This isn’t actually a filter for the woofer, but rather for the soft dome tweeter. My assumption here is this was easier to get the crossover for the tweeter wired.

Alright, now the woofer is out.
Philips F9217L-50R speakers - woofer driver (2).jpg

Philips F9217L-50R speakers - woofer driver (5).jpg

Philips F9217L-50R speakers - woofer driver (3).jpg

Philips F9217L-50R speakers - woofer driver (4).jpg

I cleaned the rotten foam right away, because it’s really annoying when it falls on the ground and gets smudged – rather hard to clean up afterwards. And yeah, that’s a pretty tiny-looking magnet once again. I forgot to put a ruler next to it to show the size, but it was about the same diameter as the magnet on the Boston HD8… except, note that this magnet is “shorter” as well. On top of that, the rear plate on the magnet isn’t “bumped” either, so speaker will have very shallow cone travel distance (low X-max.) And finally, the voice coil diameter is only 0.75” (19 mm) rather than 1” (25 mm) like on the HD8. Given all of this, I suppose even 40 Watts RMS might be too much for these speakers to handle. On the plus side though, the cone is made of thin and light, but fairly rigid paper. And the magnet gap seemed very tight, because I could easily jam the voice coil just by barely touching the speaker cone anywhere. My guess was, these would be pretty high efficiency speakers and probably sound reasonably OK. However, they also didn’t seem too worthy of a proper repair, given what they are or the fact that probably no one would use them. And to be honest, I don’t think replacement surrounds would have arrived in time to get the repair done. So, time to revisit my DIY paper surround methods again.
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Old 02-15-2022, 12:52 AM   #2
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Talking Philips F9217L-50R speakers – DIY surround repair

Part 2: DIY surround for the woofer drivers

I only had a piece of small cardboard and a round extension cord cable to work with. Therefore, I had to make multiple surround pieces instead of one big piece. Here’s how the first “batch” came out:
Philips F9217L-50R speakers - woofer paper surround (1).jpg

It’s essentially paper towel painted with white interior latex paint and strips of (scrap) A4 paper added on top for support / rigidness… then the whole thing painted again. All in all, I’m not too happy with how the first batch came out, as it was a little on the stiff side. And more importantly, the paper towel I used here turned out to be not-so-great for this, as the layers started separating when I was trying to glue it later. So note to self: don’t use this type of paper towel. Also put fewer strips of A4 paper.
Anyways, I figured I would still try out this surround… and if it was really bad, then I’d re-do it.

Cutting it up to size a little more:
Philips F9217L-50R speakers - woofer paper surround (2).jpg

Rough test fit check… acceptable.
Philips F9217L-50R speakers - woofer paper surround (3).jpg

All glued up (with regular white silicone / caulking )... and I decided to glue it on the underside this time, like the original surrounds.
Philips F9217L-50R speakers - woofer paper surround (4).jpg

Next, I did the 2nd woofer driver with the 2nd “batch” of surround pieces. This one came out considerably better, since I used “better” paper towel type (more stretchy and layers didn’t separate) along with (fewer) strips of thin newspaper. As a result, the surround came out a little softer, just as I wanted.
Philips F9217L-50R speakers - woofer paper surround (5).jpg

Assembled back together and ready for a test!
Philips F9217L-50R speakers - woofer paper surround repair.jpg

Wait now, are they? Turns out no.
These Philips speakers come with a funky-shaped proprietary connector that has a flat blade and a thin pin above it. It’s made so that they can easily hook and unhook from the Philips rack system. Well, that’s all fine, but I didn’t want to drag the speakers again to my sister’s place to test them on their system. Given that the speaker wire attached to each speaker was quite long, I cut off the connector from each speaker with about 1’ (30 cm) of cable length left with the connector. After this, I added a terminal block on the wires. The result was this:
Philips F9217L-50R speakers - proprietary connectors mod.jpg

As for “why”: the idea was that if for any reason my brother in-law wanted to hook any speakers (including these ones) to the rack system, then he could – just use the terminal block on the other side to insert the speaker wire for whatever speakers he wants. When I was at their place again, I simply plugged this connector on the back of his system and showed him how to use it.
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Old 02-15-2022, 12:57 AM   #3
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Talking Philips F9217L-50R speakers – "finished"

Part 3: testing, some modifications , & more testing

Now back to the Philips speakers… I stripped the ends of the wires and gave them nice tinning with leaded solder. Then I tested them on a spare amplifier from my uncle. Needless to say, these are very mediocre speakers. They sounded exactly like I thought they would – pretty much similar to how the Boston HD8 performed. In short, the mid-range and treble was quite respectable… if not even good at times, despite this being a 2-way system with a cheap cap crossover. In particular, the soft dome tweeter sounded really sharp in the treble range, but wasn’t overwhelming. And the mid-range was overall well-balanced. But again, bass was the problematic part (well, maybe not if one doesn’t listen to music with much bass – in that case, I could say these speakers are possibly even delightful.) The upper range of bass from 80 Hz and above was OK and quite “thump-y”. Around 70 Hz, the response was starting to slip. At ~60-65 Hz, it took a major nosedive. And below that, it was pretty much non-existent… except at around 40 Hz, which showed an ever-so-slight up-tick in a quiet “hum”.

Of course, I expected this 100%. After all, the Philips F-9217L are sealed cabinet speakers with weak woofer drivers. I don’t mind sealed cabinets, as they tend to give a nice linear drop-off on the bass response. However, that usually comes at the cost of much lower efficiency/output… and the woofers in these speakers are already quite weak to work against any wave-generated pressure of a sealed cabinet, especially at low frequencies. So it’s no surprise the low-end bass suffered.

I thought about adding a port on them… but was kind of hesitant to spend any more effort at this point, mainly because I didn’t have a clear vision of what kind of material/object to make the port out of. Sure, a piece of rolled paper (or several of them) would work just fine… but I didn’t want to make these speakers look any worse with more of my “handiwork”. The paper surrounds are already bad enough… though, at least the grilles do a good job of hiding them.

But then that same week, my uncle invited me over to chat / have a beer, and show me some of his audio gear, since he too is a big fan of classic stereo systems. So I obliged. As we were talking about speakers and whatnot, I noticed something interesting on his workbench:
speaker port.jpg

In particular, the shaving/sanding on the back of one of these ports got me curious. I asked him what speaker they came out of. He said they were installed in a woofer box that was originally sealed, but someone tried to port it. My uncle didn’t like how it sounded, so he removed the ports and sealed the woofer box again. He thanked me for pointing them out, as he said he forgot to throw them out the previous day. Immediately, my hoarder’s heart jumped a beat! “Why throw them away?”, I asked. My uncle said he knew a place that sells them and they were cheap – like about $2 each. He didn’t want them cluttering his bench, so wanted to get rid of them.

If anyone didn’t figure out where this went … I saved these ports from getting binned. The next day, I didn’t waste a moment and got straight to business – took out the hole saw and was ready to drill a hole for the port. But where?! The front of the speaker didn’t seem like it had enough space – not without cutting some plastic away from the rounded part on the port, anyways. The back seemed like a much more appropriate place. A long time ago, I remembered reading some (fan-written) speaker enclosure building guides… and IIRC, one of them mentioned that while a port will generally work anywhere, manufactured speakers often seemed to place the ports in “certain” spots more than others, like the corners, for example. But another possible “good” spot was at 1/3 and 2/3 of the cabinet’s length. Now I don’t know how much (if any) of that was true, but I quickly grabbed a speaker from a relatively modern (mid 2000’s) Panasonic SC-PM9 “mini” CD/cassette stereo system that I knew had ported speakers and the ports were on the back. Moreover, I knew this system sounded pretty good overall, despite its small size. It just couldn’t get too loud… but at normal listening levels, it had a nice bass and just sounded decent enough. After a quick measurement (and calculation) of where the ports were on the speakers of this Panasonic system, I found out that -yes, the ports were indeed at 1/3 length from the top and 2/3 length from the bottom of the speaker cabinets. Coincidence with what the articles I read mentioned? – Possibly. But I decided to “copy” this design and make the port in the same location on the Philips speakers.

So, I drilled a hole on one of the speakers to try out that little port tube I got from my uncle. I didn’t even bother doing a box/port length speaker calculation, as I was just too eager to try it already.
Philips F9217L-50R speakers - adding port hole.jpg

As you can see, there is also a sheet of foam baffle in there. It’s only on the rear side of the speaker cabinet, though. It wasn’t glued either, so I took it out and cut a hole in it as well – easy-peasy! Then I installed the port. This is how it ended up looking:
Philips F9217L-50R speakers - finished port.jpg

After this, I gave the speaker a quick test again.
Immediately I noticed a significant improvement in the bass response!
In particular, output in the 40-45 Hz range jumped up A LOT… but not only that! The 60 Hz range also got a nice boost, and the 50 Hz range was no longer MIA (still a little weak, IMO, but much better than before.) Heck, even down to 35 Hz, I could hear a light rumble that wasn’t there before. Could these port tubes really have been the perfect length and size for the tuning?!

Just to make sure I wasn’t imagining things… I marked where the speaker was on the floor with masking tape. Then I switched it for the other speaker, which I hadn’t drilled a hole into yet. Using the same volume settings on the amp, same bass frequency sweep file, same set of test songs, and sitting at the same positions in the room… no I wasn’t imagining things! No matter how many times I switched the speakers around, the ported speaker actually had much improved bass output now.

Of course, don’t take this to mean that I was demolishing the building with low-end bass. These Philips speakers are still pretty mediocre in terms of overall sound… but at least on more typical modern-day music with an extended bass range, they may not embarrass themselves as much anymore.

Needless to say, I added the port tube on the other speaker as well the same way… except, I forgot to put back foam baffle on this one. Curious enough, I decided to see if that would bring any (expected) changes. From my own previous speaker cabinet tests before, I’ve come to notice that baffle tends to lower/dampen the bass output on ported cabinets. So I wanted to see if I would get the same results here. And the answer is: yes, the speaker without the foam baffle further increased the bass output.

Again, to make sure I wasn’t hearing things in my head that weren’t there (or perhaps due to differences in the DIY paper surrounds of the woofer drivers), I opened both speakers and transferred the foam baffle from one speaker to the other. Then another run of tests, again observing speaker and listener positions in the room, along with other settings. But the results were conclusive: no foam baffle = even more bass output. So I removed the foam baffle from both speakers and called it job done.

Comparing these speakers in terms of sound to the ones from the Panasonic SC-PM9 system… yeah, the SC-PM9 speakers still sound a lot more bass-y, despite being a fraction of the size of the F-9217L’s. However, the Philips speakers weren’t that much far behind. And here is where it gets interesting: the speakers from the SC-PM9 system had a pretty nice and linear bass output down to about 50 Hz, but kind of “lost it” below that. In contrast, the Philips F-9217L would go down lower, probably due to the bigger speaker cone (and now ported boxes.) However, the bass response was a little more “all-over the place” than the Panasonic speakers. Therefore, if a song had a lot of mixed low and mid/high bass notes, the low ones would sound relatively quieter than the mid/high end ones… save for that up-tick in the 40-45 Hz range. But perhaps the room acoustics could have played a small role here too. Also, while I do love bass, I know it’s not the absolute key to everything in audio. When I played a radio station and the hosts started talking, the mid-range and treble sounded more “up-front” and “clear” on the Philips speakers, to the point where I could even hear the hosts’ mics self-gaining when they stopped talking – something that wasn’t as pronounced on the SC-PM9 speakers. Also, on the SC-PM9 speakers, the voices had a little bit of a low-end rumble to them, as did the more “punchy” kick drums. But then the SC-PM9 speakers couldn’t go as low… and yet I would say they still had more linear bass overall. It’s very weird to describe, so maybe I shouldn’t go further. All in all, I can’t say one speaker system was a winner and the other was a looser. More of, they can both be decent, depending on what type of audio content they are used for.

Anyways, that’s probably enough of my “audiophoolery” descriptions here. The bottom line is: these Philips speakers now sound decent enough for everyday use. Before this, they were unusable. If you don’t want to spend any money on fixing cheap speakers or if surrounds are not available, DIY paper surrounds certainly do work and can save them from being useless.
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Old 03-05-2022, 05:38 PM   #4
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Default Re: Philips F9217L-50R speakers – build quality impressions and DIY surround repair

Believe it or not someone sells those speakers for 110€ :

https://www.badcaps.net/forum/attach...1&d=1646523403

He even claims that the sound is perfect.

Your solution looks professional grade repair compared to this
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Old 03-05-2022, 08:14 PM   #5
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Default Re: Philips F9217L-50R speakers – build quality impressions and DIY surround repair

@momaka:

It's interesting how certain "unassuming" cabinet/driver combos can be improved. Even a (not so?) random port addition did wonders.

A QnD test for the port is to play some "party music of choice" and cover the port.
You can tell if it's close- driver excursion increases while bass output goes down.

Of course, when those were new, such types of music didn't exist.
Don't be too hard on them- they're Philips...

Try an L-pad on the tweeters. Calculators/value tables are easy to find. Drop it down 2-3 dB.
Don't use a single resistor in series, it shifts the XO point & slope.
The XO cap looks like 3.3u? Maybe drop it to 2.2u and raise the XO point.

PMax is possibly short term (excursion limited?) power.
I don't think "PMPO" existed when they were made, and these look too "nice" for that kind of silliness.

Interesting that your paper surround mod worked so well.
With my luck, I'd likely tear them apart while "testing," LOL...
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Last edited by kaboom; 03-05-2022 at 08:18 PM..
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Old 03-15-2022, 07:52 PM   #6
momaka
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Default Re: Philips F9217L-50R speakers – build quality impressions and DIY surround repair

Quote:
Originally Posted by goodpsusearch View Post
Believe it or not someone sells those speakers for 110€ :

https://www.badcaps.net/forum/attach...1&d=1646523403

He even claims that the sound is perfect.
Thanks!
That's soo funny!

Looks like only the surround got un-glued on that set as far as I can tell. If that's the case, that would be such an easy fix instead of that ugly (electrical?) tape.

Quote:
Originally Posted by kaboom View Post
It's interesting how certain "unassuming" cabinet/driver combos can be improved. Even a (not so?) random port addition did wonders.


Quote:
Originally Posted by kaboom View Post
A QnD test for the port is to play some "party music of choice" and cover the port.
You can tell if it's close- driver excursion increases while bass output goes down.
I think I tried that, and indeed the low-end bass output went back to almost nothing. Driver excursion didn't increase much, if at all, though. These drivers are really really weak. You seal/close the port, and the poor things just can't move their cones at all.

Quote:
Originally Posted by kaboom View Post
Don't be too hard on them- they're Philips...
That seriously made me laugh out loud.

But you know, they took my "abuse" surprisingly well - at least the 1st driver did. I was a little ticked off that the paper surround on the 1st driver was making a slight bit of noise due to that crappy paper towel I used on it. So to "break in" the surround, I put it through some 10-20 Hz bass test tones - open air, naturally, for the bigger excursion (more stretching of the surround.) After 10-15 minutes of doing that, the dust cap definitely felt warm. The magnet was only lukewarm. No "burned smells", though - I was careful to give it limited power per unit time (e.g. when doing the 10 Hz test tones, I had the volume envelope up and down from 0 to 100% in 2-3 second intervals.)

Quote:
Originally Posted by kaboom View Post
Try an L-pad on the tweeters. Calculators/value tables are easy to find. Drop it down 2-3 dB.
Don't use a single resistor in series, it shifts the XO point & slope.
The XO cap looks like 3.3u? Maybe drop it to 2.2u and raise the XO point.
Will keep it in mind the next time I go there. It's basically a "hidden" toy for me to play with while still in plain sight.

Quote:
Originally Posted by kaboom View Post
PMax is possibly short term (excursion limited?) power.
I don't think "PMPO" existed when they were made, and these look too "nice" for that kind of silliness.
Good point.

Quote:
Originally Posted by kaboom View Post
Interesting that your paper surround mod worked so well.
With my luck, I'd likely tear them apart while "testing," LOL...
Well, I was in an apartment building where these speakers are currently... so there's only so loud I can go with my music... hence the 10-20 Hz test tones.

Now those Realistic Nova 18's - I've literally bottomed out their VCs a few times. Of course, I then turned down the volume immediately when that happened to prevent damage (and surprisingly they were OK after this.) Since those were my first ever paper surrounds (and unpainted!), they came out a little "soft". Takes almost no effort to push on the speaker's cone and make the VC hit the bottom of the motor.
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