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Old 28th April 2006, 03:55 AM   #1
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Default Experiment in single driver OB

Well I had some 24" wide sheets of MDF sitting around and a couple of cheapo 8" philco drivers that apparently came out of an old solid state console stereo, so the obvious thing to do was to cobble together some OBs and see what would come of it.

Very interesting indeed. I made baffles 3' tall by 2' wide and made side walls 10" deep on the outside and walls 14" deep on the inside. A 7" top plate was added and driver mounting holes cut about 1/3 of the way down and offset slightly to the outside.

Surprisingly I have usable output from about 40Hz up to 10 or 12kHz. I can honestly say that the level of bass surprised me. They don't have the strength in the very deep bass to be real bone crushers but you can feel the bass even in the next room. Much more than I expected. The high end is good enough that I have yet to find an instrument that has any noticeable lack of tibre. When a high violin entrance comes quivering in it is just as delicate as anything I have ever heard. When Horowits excersises his Steinway it is as if it is right in the room with me. Plenty of power for realistic levels at least for solo piano. Later I may add the tweeters from the old philco with condensers sized for 6dB/8va at 12kHz just to add a little air to the top end but it probably isn't really necessary.

Now these are far from perfect but their capability is way beyond what their trivial cost would indicate. They are so good that I am considering making them my main speakers and moving the JBLs up to my work room.

It is hard to decide because they really do need a sub for the full impact of organ music which I listen to a lot. They are also a little bit honky at times as if the high midrange might be a little hot (considering draping some insulation over the back of the driver). But interestingly enough my reaction when switching back to my old speakers was "eeewww, these have some colorations of their own that I haven't noticed before".

I would say their strengths are intimate music (like chamber music and solo piano) as well as some brass ensembles. Opera is also quite good on them. One of my favorites using these speakers was an African hymn (more like what we would call a gospel chorus) done by Selah called "Yesu Azali Awa". The African percussion and intricate vocals were truly exciting.

I also noticed some flaws in some CDs that I hadn't noticed before. A solo piano CD displayed some harshness (high frequency hash) on the percussive attacks that sounded like over driving the mics or over modulation of a record groove. Some large orchestral recordings sounded a bit mushy due to the hot midrange but this seemed more prevalent on the CDs rather than the LPs. In general these speakers seem to prefer LPs over CDs even if the records were digitally mastered. Especially interesting since my phono cartridge is just a lowly Shure 92 pushed around by a Rat Shack Lab 440 TT.

Anyway... just one more data point. Now if there was a way to match these up with a pair of 16Hz horn subs...

mike
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Old 28th April 2006, 10:27 AM   #2
adason is offline adason  United States
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hi mike,

great of you to share with us, I have similar experiences with various fr drivers on ob
one thing i noticed was that the sound improves even more if you free that driver from low frequencies, say below 150hz and let dedicated woofer take care of that

ed
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Old 29th April 2006, 02:00 AM   #3
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Yes, I was thinking that twin subs would be a very good enhancement. It seems that the distortion should be greatly reduced as well as improving the low bass impact. The wife said that we had to move them to the side walls if they were going to stay so I tried it. I was surprised that the imaging didn't really seem to suffer very much.

I think I will keep them there.

mike
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Old 8th May 2006, 10:51 PM   #4
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Default Update

I have gotten things set up with a subwoofer and an aux. tweeter. I am still running full range into the 8" but since I have the sub on line I don't have to boost the bass so the effect is to reduce the strain on the full range quite a bit. The tweeters are soft domes that I had from an earlier project. I have just a simple blocking cap to protect the tweeter. The cap I have crosses at 5K. I will probably get one for 10K but even as it is the sound is much smoother and less honky.

Here is a pic of the setup (sub not shown) as it sits now. Eventually I will mount the tweeters on the baffles right above the FR.

mike
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Old 9th May 2006, 08:01 AM   #5
Rudolf is offline Rudolf  Germany
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Default Re: Update

Quote:
Originally posted by mashaffer
The tweeters are soft domes that I had from an earlier project. I have just a simple blocking cap to protect the tweeter. The cap I have crosses at 5K. I will probably get one for 10K but even as it is the sound is much smoother and less honky.
Mike,
it is a good idea to x-over at 5k or even 10k. But in the long run you should consider a cone tweeter because it will better integrate with the philco. The dome tweeter will still radiate 180 at the x-over frequency while the philco is already beaming.

Rudolf
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Old 9th May 2006, 01:57 PM   #6
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hmm... good point. I will check the philco tweeters. I was getting no output from them the other day but that could have been the old caps. If push comes to shove a couple of cone tweets would be super cheap.

mike
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Old 11th May 2006, 08:13 AM   #7
Nuuk is offline Nuuk  United Kingdom
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Mike, I only just found this thread. You may be interested in my 'travels' with OB's that started just like yours. You can read all about it here .
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Old 12th May 2006, 12:22 AM   #8
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Thanks Nuuk. Some nice looking units there. It is a bit hard for me to see but the woofer looks like it has some sort of ring around the outside that makes it look like it is flush mounter rather than rear mounted.

It is interesting that you used the flooring for them. I was just thinking the other day how T&G flooring would make a nice veneer for speakers. I was also thinking that some sort of T&G product would be ideal for making large built in bass horns as it would make it much easier to produce an exponential flare. For that application though I think that a product that was at least as long as the width of the horn mouth would be better so that you don't have to try to make perfect joints where the ends butt together.

Rudolf, it turns out that the voice coils on the Philco tweeters are open. Oh well.

mike
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Old 12th May 2006, 08:27 AM   #9
Nuuk is offline Nuuk  United Kingdom
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Quote:
It is a bit hard for me to see but the woofer looks like it has some sort of ring around the outside that makes it look like it is flush mounter rather than rear mounted.
The units are rear mounted Mike.

I have not written anything up on DD yet but there is a thread showing my new baffles/woofers (and more flooring) here.
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Old 13th May 2006, 04:17 PM   #10
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Check out gravity well of a dark star thread on audiocircle. Its alive again and the happening OB thread at the moment
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