My frugal reference loudspeaker with Philips Fullrange.

[goldyrathore]

Mounting the tweeter: You could use PVC pipe of appropriate size to mount the tweeter. This is the way car co-axs generally mount the tweeter assembly.
Magnet mounting the drivers: The drivers are not parallel to each other so this will pose a structural problem. However it can be overcome. Do let me know if the drivers are pushed from the inside then can the driver mounting screws take the load? I will draw a figure to explain an idea to mount the magnets to the cab.

 

[t.antony]

Suri, Keith
I need to fabricate something in metal for magnet mounting the drivers - will post the pics once I finalize about this. I need to take a trip to the scrap market as well to see if I can get any substitute for what I have in mind.

Regds...

 

[t.antony]

Mounting the tweeter: You could use PVC pipe of appropriate size to mount the tweeter. This is the way car co-axs generally mount the tweeter assembly.
Magnet mounting the drivers: The drivers are not parallel to each other so this will pose a structural problem. However it can be overcome. Do let me know if the drivers are pushed from the inside then can the driver mounting screws take the load? I will draw a figure to explain an idea to mount the magnets to the cab.

I preferred a solid phase plug to avoid having another resonating air-column near the acoustic center of the speaker (of course the tube can be stuffed to avoid this). I might possibly try this material since it's pretty easy to obtain. I have already got a thick paper tube of suitable diameter.

The mounting screws can take the load in the way you indicated - plus now that I have the bottom plank removable, there is more freedom to fix the drivers. Ideas are welcome.

Regds...

 

[t.antony]

I made this phase plug last night from a bunch of toothpicks. They are stuck together with super glue. A metal screw at the bottom will magnetically attach this to the pole piece (similar to the planet-10 phase plugs - planet_10 hifi). I will shorten this to a suitable length and do a listening test tonight.

BTW here is a similar looking phase plug - http://www.tb-speaker.com/detail/1230_04/w6-1916.htm. There are claims that the unique shape aids in better performance at high frequencies compared to the bullet shaped ones.

Regds...

 

[suri]

the blade handle is from a Meccano set - and the scalpel blade from where?

 

[Thad E Ginathom]

It's a Swan Morton scalpel blade and, along with everything else in this thread, I am amazed at the skill and ingenuity.

Right at the start, when I saw the thermocool mockups, I thought, "Thermocool is harder to word than wood! How on earth to get it so neat?"

 

[t.antony]

Suri, Thad

It's a surgical blade, easily available in medical shops and cheap as well. A pack of 10 was 5 bucks.

Regds...

 

[t.antony]

It's a Swan Morton scalpel blade and, along with everything else in this thread, I am amazed at the skill and ingenuity.

Right at the start, when I saw the thermocool mockups, I thought, "Thermocool is harder to word than wood! How on earth to get it so neat?"

There is another excellent tool to work with thermocol and other soft materials, A textile cutting blade similar to the one used in this pic - http://emoallem.omnisitebuilder.com/_files/Image/Cuttin2.jpg.

I got a used one from a garment unit and amazed at how it retains it's sharpness even after deliberate misuse upon wood, thermocol, pcb etc .

Regds...

 

[t.antony]

Found this useful little program for designing coils(Calculation of electrical inductance). It accommodates square and rectangular coil geometry which makes it possible to use the easily available rectangular bobbins used in power transformers. The glitch is - this only allows the computation of air-core coils.

Does anyone know a program that has both features - ie: Rectangular geometry and use of different core material like laminated iron? Also I have used up all my speaker mounting gasket bought from corrson -( Corrson - India's only DIY Store for Hi-End Audio). Is it available locally/or is there any substitute that can be used?

Regds...

 

[quad]

Anthony,

Great work! Are you front baffles 0.5" thickness? The rebated edge
looked a bit on the thinner side.


Here's a nice coaxial tweeter install, if you are brave enough.

Pioneer B20 Coaxial Tweeter Install - diyAudio

 

[t.antony]

Great work! Are you front baffles 0.5" thickness? The rebated edge looked a bit on the thinner side.

They are 19mm panels, the edges look thin due to the dado cut inside.

Here's a nice coaxial tweeter install, if you are brave enough.

Pioneer B20 Coaxial Tweeter Install - diyAudio

Something similar to this was the initial idea but opted out as indicated in post #30

Regds...

 

[t.antony]

Did a listening test on the full rangers to test the effect of phase plug. The drivers were subjected to pink noise for about 8 hours prior to the testing. The results were very promising and the clarity of the upper mids and highs improved. While the phase plug was dropped in place, the effect was so noticeable as if I am connecting a new tweeter. Never thought beaming at the whizzer cone will do such damage to the high frequency response of this driver. I think every single driver user should try out this mod.

Also tried fixing the tweeter to the phase plug and tested with different crossover frequencies from 2.5 to 5k. There was a little lack of coherency in the overall sound across the crossover frequencies. I think fixing the tweeter at the acoustic center of the full range will do good to response. Finding the acoustic center will be a bit of a trial and error with different size phase plugs and probably with the help of a measurement mic. Will do that soon.

Here is a pic...

Regds...

 

[keith_correa]

how about using the oval light bulbs we get as a phase plug. Like this one.

 

[goldyrathore]

Very impressive results with such simple mod.

The drivers were subjected to pink noise for about 8 hours prior
to the testing.

I ve read that drivers need a 40 hr or more of pink noise to break-in. Maybe its worth breakin them in more.

The results were very promising and the clarity of the
upper mids and highs improved. While the phase plug was dropped
in place, the effect was so noticeable as if I am connecting a new
tweeter. Never thought beaming at the whizzer cone will do
such damage to the high frequency response of this driver.
I think every single driver user should try out this mod.

This is very informative. I didnt think the improvement would be so much.

Also tried fixing the tweeter to the phase plug and tested
with different crossover frequencies from 2.5 to 5k.
There was a little lack of coherency in the overall sound
across the crossover frequencies. I think fixing the tweeter
at the acoustic center of the full range will do good to response.
Finding the acoustic center will be a bit of a trial and error with
different size phase plugs and probably with the help of a
measurement mic.
Will do that soon.

The phase response is not that easy to measure IMHO, though if you could do it, then it would be good learning for me (and probably other too).
Alternatively, you could calculate the acoustic centres and place the tweeter such that it is within limits by shortening the phase plug accordingly. The limit as you know depends on the crossover frequency,Phase Correction - Myth or Magic.

Also adding a little dampening to the rear of the tweeter would help IMO.
I too have the same tweeter, since its a car tweeter, I doubt it was designed to be used below 3.5K-4k. The whizzer would have already started performing in that area. I did notice improvement in the tweeters sound after breakin , so urge you to do it too.

Regards,
Goldy

 

[t.antony]

I was putting off the idea of doing a dry run on the speakers as I needed some good gasket material. But yesterday fixed the drivers using the two sided sticky foam tape available in stationary shops. IMO it did a decent job in plugging the air leaks.This listening test was mainly for checking the bass response and cabinet resonances. Each box was stuffed equally with polyester fill taken from a pillow. The drivers were connected parallel and in phase, there was no crossover and the tweeter was not connected. Played Nirvana MTV unplugged album and was pleasantly surprised at the outcome. The bass was controlled and reasonably tight. It was very close to the open baffle bass, the transient response was equally good as I put some tracks from Metallica - Master of Puppets album. The lower mids seems to be represented well and the highs were detailed. There is some real issue with cabinet resonance and I am planning to take care of it by stiffening the cabinet with fiberglass lining at least 4mm thick inside and outside.

It seems like these does not require the baffle step correction(BSC) to the extend I had accounted before. Also the fullranger having difficulty with the lower octaves when driven high with my Sansui AU-919. I will cross the full ranger between - 200-3500 and apply BSC (3 to 6db), woofer @ 0-200 & tweeter above 3500. The band pass and low pass will be first order and the high pass will be 2nd order.

While testing the distance of the front baffle from the back and side walls were 3 feet, considering the 19.5 inch depth of the box, the rear driver is only about 1.5 feet from the back wall. I did increase this distance by a feet or two but the sonic benefits were not very noticeable.

I spent more than 6 hours listening to music last night with various tracks by Jimi Hendrix, Doors, Rush, Pearl Jam, Nirvana, Scorpions, Chris Rea, Pearl Jam, Michael Bolton & Elton John. Also tried some heavy metal numbers by Ozzy, Cinderella, Metallica & Iron Maiden. The drivers now have about 15hrs on them but they still seems to be breaking in. I think the 40hr break-in period as mentioned by Goldy is needed before any objective tests.

Regds...

 

[Rajiv]

Sansui AU 919

:clapping:


Hi Antony,

That is one superb amp.It will give several new high end amps a run for their money.

Regards
Rajiv

 

[t.antony]

That is one superb amp.It will give several new high end amps a run for their money.

Indeed, the AU-919 is a well refined beast. May be due to the insane frequency response of DC to 50000Hz, there is lots of power at the ultra low bass frequencies. I was using it to drive two of these pro-drivers in a Open Baffle setup. While watching Terminator Salvation there were times when I could feel the air movement of the lowest octaves .

Regds...

 

[t.antony]

Update...

The drivers seems to be broken in fully. So far the xover had been pc based with both drivers crossed at 200hz and some equalizer settings from 311Hz to 1khz to compensate for the baffle step loss. Even though the mids and lows seemed OK, there was something missing at the higher mids - it seems like the rhythm guitars are a bit muted and missing the "air". May be the plan of using a high xover point is not such a good idea...

To cross check what is happening, did some response measurements this weekend.The speakers were placed about a feet from the back walls and 1.5 feet from the side walls. Took two measurements. One close to the speaker and one at the listening position. Here is what I got.

The blue line is the near-field reading, everything looks OK till about 2k. The brown line is at my seat - there seems like a rather large suck-out happening just below 55hz.

It seems like I have to cross the tweeter around 2khz against my earlier plan of 3.5k. Hopefully my tweeter can rise up to the challenge . The xover design is getting a bit complicated for me now as my preference is to use both drivers in parallel, as it will drop the the impedance to 4ohm, I am planning to raise this to 6 ohms with the xover design.

Regds...

 

[t.antony]

Wound my first pair of air core inductors last night. These are the largest I will require for this project(6mH), they weigh 475 grams each with a DCR of 1.3ohms. I used 19SWG wire since I need high DCR inductors for my xovers.

Regds...

 

[gopib]

Looks very neat for a first attempt. How much time did each take you? Congratulations!!