Planning a Mini Book Shelf speaker for a shoe string budget friend

[Hari Iyer]

I recently had a discussion with one non-FM friend of mine who was looking for a book shelf speaker on a shoe string budget. I initially could not figure out how it can be possible and he mentioned his all inclusive budget is just 18K. But the speaker should sound like a 80k+ speaker commercially available. Now this was a challenging objective as cost and SQ has got a direct relationship.

After a two weeks research, i think it could be possible to make one at his budget. I considered the following to arrive at this,

- Drivers has to be Peerless India or similar to meet the budget objective.
- Woofer has to be paper cone for smooth response in its bandwidth.
- Tweeter has to be textile or silk dome with not too high a resonance for again a smooth response.
- Crossover has to be simple, but again workable and not too fancy with proper simulations, measurements etc.
- Box has to be mini box and would go for a MLTL or Aperiodic loading.
- Laminates will be used instead of veneer to keep cost low.
- No compromise on crossover component quality, box build qualtiy, wood and other materials.
- This mini BS will mostly be used in the bed room kind of arrangement.

Am still in the process of finalizing the woofer and tweeter that can fit the bill and will narrow down within a week.

Thanks for looking.

 

[keith_correa]

Just throwing this out here as possible candidates:

Iwai Electronics Pvt. Ltd.
Iwai Electronics Pvt. Ltd.

 

[Hari Iyer]

Just throwing this out here as possible candidates:

Iwai Electronics Pvt. Ltd.
Iwai Electronics Pvt. Ltd.

@ Keith

Thanks for the link. In fact i was browsing through the website today morning and could not make up my mind. You made my job easy.

BTW, who are the dealers for IWAI speakers in Mumbai? I know Mr.Sunil personally when i purchased some 3.5" full range drivers from his factory. But i dont know of any dealers who deal with them. I am not sure if Sunil gives just a pair of drivers as his set-up is more for manufacturers and not for diyers like us.

Neverthless it will be good to touch base with him on this pretex of checking with him.

Cheers,

 

[keith_correa]

@ Keith

Thanks for the link. In fact i was browsing through the website today morning and could not make up my mind. You made my job easy.

BTW, who are the dealers for IWAI speakers in Mumbai? I know Mr.Sunil personally when i purchased some 3.5" full range drivers from his factory. But i dont know of any dealers who deal with them. I am not sure if Sunil gives just a pair of drivers as his set-up is more for manufacturers and not for diyers like us.

Neverthless it will be good to touch base with him on this pretex of checking with him.

Cheers,

Glad to be of help. They don't have any dealers. Just request Sunil to sell them to you and I'm sure he will. He's a nice guy and very accommodating that way.

 

[jmascreen]

Just throwing this out here as possible candidates:

Iwai Electronics Pvt. Ltd.
Iwai Electronics Pvt. Ltd.

Any idea where to buy? Also any experience to give a comparison with peerless Indian drivers?

 

[kpsthakur]

Looks like they are decent drivers, has anyone made any speakers yet using these? Please share results if possible


Sent from my iPhone using Tapatalk Pro

 

[sadik]

They do really sound good if used in proper designed enclosure. I have used them in bookshelf along with Dayton tweeters. The Result is awesome. You can have a look on my recent thread "Book Shelf for Small Room & Multimedia Speakers" http://www.hifivision.com/diy/67242-book-slelf-small-room-multimedia-speakers.html

Sadik

 

[Hari Iyer]

They do really sound good if used in proper designed enclosure. I have used them in bookshelf along with Dayton tweeters. The Result is awesome. You can have a look on my recent thread "Book Shelf for Small Room & Multimedia Speakers" http://www.hifivision.com/diy/67242-book-slelf-small-room-multimedia-speakers.html

Sadik

Thanks.
How did you arrive at the box dimensions? Did you use any simulation software?

 

[sadik]

Thanks.
How did you arrive at the box dimensions? Did you use any simulation software?

Our Forum Member Mr. Aniket designed this enclosure. He also designed the crossover for same. Secondly he has the Instrument to measure the parameters of Speaker, He has measured the Parameters of this driver and then designed the enclosure.

Below is the response curve of the designed enclosure.

You are the master in this field hence i hope you will have some idea after looking on the above graph.

Sadik

 

[Hari Iyer]

@ Sadik
Thanks for the details. Are these simulated response or measured response? Please advise.

 

[sadik]

@ Sadik
Thanks for the details. Are these simulated response or measured response? Please advise.

Those are stimulated response. & I think the below response is actual measured response of the Book Shelf's. However this actual response was measured by Aniket for the same designed bookshelf. He has not used any stuffing in his boxes, however i have damped all the walls of my enclosure & by my listening experience i can say these enclosures hit the frequency between 45 to 50 Hz easily.

Sadik

 

[keith_correa]

Maybe this time you are so inclined, you should try this: there is a popular misconception that only extensive [over-] bracing in a speaker cabinet reduces panel vibration. There is a simple inexpensive way that is more effective than extensive bracing - a sandwich layering [CLD?] of speaker walls. Buy sheets of roofing felt [asphalt sheet - a roll typically costs Rs. 800 - will last you for many speakers ]. Use ~half the thickness of wood sheets that you normally use for the walls [this is the base layer - a]. Use another wood sheet that is ~1/4th the thickness of "a" [this is the constraining layer - b]. Use rubber glue and glue the roofing felt between "a" and "b". Use the "b" face as the inner wall.

May not be as effective for small speakers as much as for mid/large speakers.

 

[Hari Iyer]

EggI usually use triangular interlocking joints on all 6 sides. This gives me the most rigid cabinet ever and is easier to build for a carpenter. Also avoiding internal braces also allows me to make an accurate estimates of internal cabinet volumes.

 

[keith_correa]

EggI usually use triangular interlocking joints on all 6 sides. This gives me the most rigid cabinet ever and is easier to build for a carpenter. Also avoiding internal braces also allows me to make an accurate estimates of internal cabinet volumes.

The edge joints would be rigid using interlocks but what about the large [relatively] area of the panels - those would be resonant no matter how rigid your edges are. The edge joints are usually the least of one's concerns - simple butt joints work just as well if cut well. But, whatever works for you!

 

[Hari Iyer]

I used the published TS parameters of this IWAI mid woofer and found a TQWT MLTL to be best suited for the job. I am getting a -3dB of around 50 Hz with this loading. One matter of concern was some high port nise around 560 Hz. Also the port velocity was quite high at 65Hz.. The box looks like my micro version of the Metronome speaker. I will still wait for the measured response after I purchase this driver.

 

[Hari Iyer]

The edge joints would be rigid using interlocks but what about the large [relatively] area of the panels - those would be resonant no matter how rigid your edges are. The edge joints are usually the least of one's concerns - simple butt joints work just as well if cut well. But, whatever works for you!

I usually tune my line a bit higher around 60Hz to 70Hz, so most low frequency energy below that escapes through the terminus from the high acoustic impedance of the box to the low acoustic impedance of the room. The output below the line tuning frequency is dominated by the terminus and not the driver. Also above the tuning of the line the driver becomes more active. Critical damping of the line is the key to get the right balance imo. Standing waves can be reduced a bit by using golden ratio for the box dimensions and stuffing too.

 

[asliarun]

Apologies in advance if this is off-topic and if so, please delete or ignore.

There was an interesting thread on another forum about a series on mods on ELAC speakers, and interestingly, Andrew Jones (the designer/engineer) chimed in. A part of the discussion was about cabinet design and stuffing, so i thought it would be interesting to share in this thread. To quote from this thread:

-------
Danny comments on the quality of the cabinet MDF and the thickness of the baffle and wrap. The cabinet is the major cost in a speaker. It would be nice, wouldn't it, to have thicker cabinet walls, internal bracing, more rigid MDF, more internal damping etc. However, all of this would greatly increase the cost, and for what? Lets think about cabinet vibration. The major excitation source if the reaction force imparted to the magnet and hence driver frame that feeds mechanical energy into the cabinet causing it to vibrate. Now, measures to thicken up the walls, or use a higher grade of MDF, absolutely do not remove the resonances. They move them up in frequency. In fact, they can become more audible!
The grade of MDF I chose is softer and so has better internal damping, and can actually sound better than the "better" grades. In fact my early prototype cabinets were better built, with internal bracing and thicker walls. When I looked at the cost I realized that this cost would be better spent on improved cone materials, larger voice coils, larger magnets, better-than-standard xover complexity and parts etc.

Regarding the internal damping material, the cabinet is not stuffed full. This is deliberate. Besides costing more for a higher grade and more of a better damping material, there is a fallacy involved in the effect of damping material. In theory, a heavily stuffed cabinet changes from adiabatic expansion to isothermal and as such appears to be up to 1.4 times larger. This effective increase in cabinet size is offset by the greater resistive losses and so the performance gain is not that great. In the practical quantities that we are likely to see used, the effective increase is negligible. However, in a vented box system, putting in too much damping material will severely reduce the output of the vent and greatly reduce bass output. The choice I made of damping material was optimized between damping to some degree the standing waves while not impacting bass performance.
Danny shows a measurement of the impedance of the speaker that shows some apparent resonances around 25Hz and 60Hz. He attributes these to internal standing waves. This is erroneous. The cabinet cannot support standing waves at these low frequencies. If they exist they are more likely to be mechanically coupled. However these blips in the impedance curve do not show up in my measurements. I suggest that they are due to something in the measurement procedure. I know the repeat measurement after the modifications shows they are gone, but I wouldnt attribute this to the added stuffing reducing internal standing waves. I would however encourage Danny to re-investigate these measurements.
-----

There also this interview by Andrew Jones where he talks about the design and engineering tradeoffs and choices he made with the ELAC B5/B6 speakers. He takes a different approach in this series and focuses on driver quality and uses other techniques to mitigate the adverse effect of cabinet stiffness. More relevant bits are from minutes 15 onwards and minutes 27 onwards.

 

[venki7744]

Hi Hari,

Good to see you back in action . I did a quick simulation of the IWAI mid and tried to simulate a TWQP. Here are the results, I dont think its the best enclosure but I believe SPL, Velocity and GD looks OK to me. Let me know your thoughts on this.







PS: Not able to load the rest of attachments. I can email you the figures.

Thanks
Venki

 

[Hari Iyer]

@ Venki
These boxes are huge and definitely not low budget ones. Mine is a TQWT, MLTL with BS dimensions. Will post asap.

Cheers,

 

[Hari Iyer]

These are the results of LA from published TS parameters. The box is just 15" tall and 7" deep and 7" wide with tapering profile at the top like my Metronome FS speaker.