Driver placement calculations in single driver enclosures

kinku · « **on:** 25 Mar 2013, 11:13 am »

How can I calculate the ideal location for Single driver Full range in a baffle?

DanH · « **Reply #1 on:** 25 Mar 2013, 08:01 pm »

If you have a wintel machine the edge program is very handy for this.

http://www.tolvan.com/

kinku · « **Reply #2 on:** 26 Mar 2013, 01:24 am »

Great software and very useful too. :thumb:thank you Dan. I guess without baffle compensation all speakers can have a midband peak.Is it the reason people complain about some full range speakers?using them without a baffle compensation?
In between something confusing reading the instructions
"The Edge suggests two different compensation circuits, circuit 1 is suited for passive realization in the crossover, in this case the driver should be connected in series with L and R2 in parallel."
Does that means Land R2 are parallel and both connected in series to speaker?
It is also interesting to see that the peak is lowest when speaker is centered little bit off from the center along the width too?Is it for real!!!

kinku · « **Reply #3 on:** 26 Mar 2013, 02:14 am »

FullRangeMan · « **Reply #4 on:** 26 Mar 2013, 02:42 am »

Quote from: kinku on 26 Mar 2013, 01:24 am

Great software and very useful too. :thumb:thank you Dan. I guess without baffle compensation all speakers can have a midband peak.Is it the reason people complain about some full range speakers?using them without a baffle compensation?
In between something confusing reading the instructions
"The Edge suggests two different compensation circuits, circuit 1 is suited for passive realization in the crossover, in this case the driver should be connected in series with L and R2 in parallel."
Does that means Land R2 are parallel and both connected in series to speaker?
It is also interesting to see that the peak is lowest when speaker is centered little bit off from the center along the width too?Is it for real!!!

Cover the baffle(out side) with a felt 5 or 10mm layer helps.

kinku · « **Reply #5 on:** 26 Mar 2013, 04:26 pm »

Fullrangeman where can I find some? Has anyone experimented with them any illustrations online how to do it?What is the principle behind felt padding?

DanH · « **Reply #6 on:** 26 Mar 2013, 04:50 pm »

The resistor and inductor are wired in parallel. Frequencies higher than the baffle step frequency are forced through the resistor and attenuated. Frequencies lower than the baffle step frequency flow through the coil and are not attenuated.

Madisound sells self-adhesive flannel. I found plain flannel at hobby-lobby.

kinku · « **Reply #7 on:** 26 Mar 2013, 04:57 pm »

Dan I just finish reading about self adhesive flannels in another post.Is it another controversy?
How accurate is Edge simulation compared to real life sound reproduction?
What I am waiting to hear though is about the placement of driver by one edge that will minimize the peak of midrange band to the lowest.Any one experimented with that before in real life with a FR speaker to one corner of Box?

MJK · « **Reply #8 on:** 26 Mar 2013, 05:04 pm »

You can model all of this in my MathCad worksheets including the floor bounce and reflections off of nearby walls. Much more accurate compared to the EDGE which only includes the impact of the baffle geometry. The box and the driver responses are not accounted for in the EDGE program. The MathCad results are very accurate.

kinku · « **Reply #9 on:** 26 Mar 2013, 05:16 pm »

MJK that sounds great already.Thank you. Which worksheet from your listing should I choose for a simple bass reflex box?

MJK · « **Reply #10 on:** 26 Mar 2013, 05:32 pm »

The TL_ML_Corner worsheet will do the trick. It will model a bass reflex enclosure and if it is long enough in the vertical direction (a floor stander) will take into account internal standing waves. Also look on my Horn Theory page for a new BLH design for the FF125WK, so far the feedback has been positive.

kinku · « **Reply #11 on:** 26 Mar 2013, 08:39 pm »

MJK total investment for getting the software simulation from you is reasonable but the platform to run it is expensive. I wish you had some free worksheets to try with a bass reflex enclosure. Thanks for suggestion though.

JohnR · « **Reply #12 on:** 27 Mar 2013, 01:11 pm »

Quote from: kinku on 26 Mar 2013, 08:39 pm

MJK total investment for getting the software simulation from you is reasonable but the platform to run it is expensive.

I always thought so too, but I downloaded the free MathCad Explorer from MJK's page today and it seems to work fine with the sample worksheet. Installed and ran on Win7.

http://www.quarter-wave.com/Back_Door/MathCad_Models.html (near bottom)

rjbond3rd · « **Reply #13 on:** 27 Mar 2013, 01:44 pm »

Also, there is an even more full-featured student version in this MathCAD book, so you can save your work as you go:

http://www.amazon.com/Essential-Mathcad-Engineering-Science-Edition/dp/012374783X/ref=sr_1_1?ie=UTF8&qid=1364390619&sr=8-1&keywords=mathcad

There are many other (very good!) tools which are great for getting started, but they are only simpler and easier because they ignore a lot of the physics. Even if you use -all- the other tools out there combined, they still don't add up to what MJK's software does (because they are simplifying the physics by excluding the majority of factors, e.g., the room etc.) I've been using MJK's software for a few years and I am still just scratching the surface (but I'm a slow learner).

Kinku, if you aren't ready to make the leap to MJK's software for whatever reason (there's no rush), and you just want to crank out a halfway decent box for the FF125WK, you could build a prototype which would have ~golden ratio dimensions, net volume of the driver's Vas (7.2 liters), tuned to Fs (67Hz), with the driver offset into the corner as your Edge model shows, and then place the speakers on the shelf to minimize baffle step (i.e., no speaker stands).

This is what gurus call a Vb=Vas, Fb=Fs alignment and it seems to work well with drivers of that approximate Qts (.42), in that scenario, certainly as a starting point. But if you are (as I suspect!) a perfectionist, in my opinion, you will need MJK's software to go all the way

For example, optimizing not only the tuning, port size, excursion etc. but also the port location which can flatten the response. If that's too much to consider at this point, I'd say just build the Vb=Vas, Fb=Fs alignment with the drivers offset, and mount the speakers on a shelf.

kinku · « **Reply #14 on:** 27 Mar 2013, 02:27 pm »

I think I am here because I imagine myself as a perfectionist. I try to play around with sample MATHCAD file at MJK site. First on explorer that opened up a file like pdf then with PTC software which is free for a month trial. Apparently it uses mcdx files and could not open the sample. I am expecting to get a feel before I use it since I have to purchase the worksheet file.
I am not trying to say it does not work but do not know how the whole platform work. It does not seems like a typical software application where you provide data in the input fields.
I wish I have a way to get a flavour of user interface before I buy it. If it is hard enough (like learning a programing language then I possibly can not do it).

JohnR · « **Reply #15 on:** 27 Mar 2013, 03:00 pm »

Quote from: kinku on 27 Mar 2013, 02:27 pm

I try to play around with sample MATHCAD file at MJK site. First on explorer that opened up a file like pdf ...I am expecting to get a feel before I use it since I have to purchase the worksheet file.

I'm new to it too, but I think what you're seeing (with the Explorer program) is what it is. Change the length of the line and scroll back down to the graphs and you will see that they have changed. There are other fields you can change, I forget which but it was in the instructions...

rjbond3rd · « **Reply #16 on:** 27 Mar 2013, 03:18 pm »

Quote from: kinku on 27 Mar 2013, 02:27 pm

...It does not seems like a typical software application where you provide data in the input fields.

MathCad definitely accepts inputs, from which it produces output (e.g., the graphs). One gotcha is that you have to scroll the worksheet to get it to recalculate. It's possible that the newest trial MathCad won't read the older .mcd format. I'd recommend following MJK's instructions exactly:

1. Download the free MathCad Explorer 8: www.quarter-wave.com/Back_Door/MathCad_Explorer.zip

2. Download MJK's sample problem: www.quarter-wave.com/Back_Door/Sample_Problem.mcd

3. Download MJK's worksheet tutorial: www.quarter-wave.com/Back_Door/Worksheet_Tutorial_7_03_09.pdf

If you get licensed, definitely join the Yahoo group which is very newbie-friendly.

kinku · « **Reply #17 on:** 27 Mar 2013, 09:03 pm »

Rjbond Thanks.I am sort of figured out how it works. I am not sure there is dedicated worksheet for bass reflex system with MJK,he mentioned some TL_ML worksheet.I looked through the listing could not find one. MJK can you please tell me what all things I can analyze with the TL_ml worksheet. Is it not transmission line speakers are different from bass reflex model?Especially of small dimensions of 6-10 litters.

rjbond3rd · « **Reply #18 on:** 27 Mar 2013, 10:24 pm »

Quote from: kinku on 27 Mar 2013, 09:03 pm

I am not sure there is dedicated worksheet for bass reflex system with MJK,he mentioned some TL_ML worksheet.I looked through the listing could not find one.

...Is it not transmission line speakers are different from bass reflex model?Especially of small dimensions of 6-10 litters.

Hi kinku,

Fortunately, there is an MJK worksheet for bass reflex systems, and it's the TL_ML_Corner worksheet which MJK mentions above in his post. A BR which goes from having cube-shaped or golden ratio dimensions can be stretched vertically (same net volume) so that it morphs into a TL with a port (vent), a.k.a. mass-loaded TL or ML TL. In other words, the interior resonances in the BR (which are not useful) are tuned to be useful in the ML TL.

Definitely check out Martin's research on his site. It's very dense but it's all there

MJK · « **Reply #19 on:** 28 Mar 2013, 12:46 am »

Robert has summed it up nicely, could not have done better myself.