Introduction and question

ShawnL · « **on:** 12 Dec 2014, 07:17 pm »

Hello

My name is Shawn, I'm a science student at the University of Manitoba, 26 years old.

HiFi has been a hobby of mine since I could start spending babysitting money on it

I've been out of it for a while but have a living room that I can set up a system in again. I have sold most almost all of my equipment I had gathered over the years to pay for school and am currently using my first speakers I ever got (sentimental, the only ones I kept) Infinity RS6 (With a seas bass driver). And a newer Denon AVR-1712 that I picked up for very cheap.

I want to build a simple open baffle and was wondering if anyone has the time to give me some advice. This is what I want to do. All the parts I list, I have. Remember I'm a poor student. Just want something fun and different that will sound nice. (I tried using modelling software, to no avail)

Use single Aurasound NS3-8A fullrange for L-R open baffle (2 total)
Use Seas (P21RE) 8 inch for bass in enclosed box L-R (sub out powered by a seperate 2 ch Denon power amp)
Natural baffle rolloff around 120hz (Denon 1712 crossover)
Let Audyssey Multeq xt work out most of the kinks

I would really appreciate help in the dimensions of the OB for placement of the Aurasound NS3's
I believe it would make sense to have a closed box almost on the floor with the Seas 8", and a flat panel attached to it for the NS3.

No Passive Crossovers (let Audyssey/bi-amping handle that)

What do you think is this reasonable?

Thanks in advance
Shawn

ShawnL · « **Reply #1 on:** 12 Dec 2014, 07:36 pm »

Fwiw The reciever has crossover options of 80, 100, 110, 120, 150, 200, 250

ShawnL · « **Reply #2 on:** 12 Dec 2014, 07:45 pm »

Seas P21RE
http://www.seas.no/images/stories/vintage/pdfdataheet/h313.pdf

Aurasound NS3 (I have the older polypropylene model but the specs are similar)
http://www.madisound.com/store/manuals/aurasound/NS3-193-8A.pdf

ShawnL · « **Reply #3 on:** 13 Dec 2014, 04:05 pm »

That said if somebody has good reason to believe these two drivers will not mate up well. Then I would be open to *really affordable* suggestions. So long as its.

Single driver for 'full range' in open baffle
Single driver for bass/midbass in sealed box
Ideally no passive crossovers, or veeeery simple.

This is ultimately for ease of building. I don't have the time, or experience for anything more complicated.

I would like to make something work first and foremost with what I have. But I am open to very affordable alternatives.

Remember I'm in Canada so shipping is usually more expensive.

mcgsxr · « **Reply #4 on:** 13 Dec 2014, 04:22 pm »

The Aura driver has some of the requisite specs to perform well on OB.

Looks like someone else has taken a run at using it that way - http://www.diyaudio.com/forums/full-range/66949-aurasound-ns3-194-8e.html

Questions:

1. You will biamp? Meaning that the Aura will have an amp, and the bass drivers will have an amp?
2. You will use the Denon to actively Xover the OB driver to the box woofer?

Assuming 1 and 2 are yes - I would seriously start with cardboard.

Don't barf yet, we're just building mules and it is easy to cut.

Do some reading about width baffle will support that driver to approx 100Hz. You may realistically need to to higher with that 3 incher, but I have never used one.

Once you have a starting point, bring in the biamped woofer and see what you think.

I ran mdf baffles for 7 years, so once the experimentation with the cardboard is done, and you refine your baffle size and Xover compliment, use what material you desire. MDF is cheap and readily available in Manitoba I would bet. Sure is here in ON.

There are calculators out there that will assist with the baffle width calc, but nothing beats experimentation.

ShawnL · « **Reply #5 on:** 13 Dec 2014, 04:46 pm »

Thanks for the reply!

The answer to both of your questions is yes.

For MDF yes I think I have a couple 4x8 sheets in the garage...I don't know how straight they are. lol.

My confusion lies in the baffle dimensions. As you said to look around, I have and am confused. Are there set values? Like a certain amount of surface area, or square footage yields certain baffle rolloff? Or it seems more that the distances from the driver to each edge decide baffle rolloff?

Does this mean that a driver placed in a tall narrow baffle with have the bass rolloff at the furthest edge? (to the bottom) Do each of the 4 edges (simply put) cause rolloff at there respective frequencies?

Does this compound rolloff at equal distances? Or does more surface area at equal distances support more of the respective frequency? (Circle)

This is what's stumping me.

It makes me wonder, is there not a 'perfect' baffle shape that treats all frequencies equally (within limits). Almost like a flat response baffle? I assume that shape would likely be out of the realm of simple rectangles and circles.

Rudolf · « **Reply #6 on:** 13 Dec 2014, 07:54 pm »

Quote from: ShawnL on 13 Dec 2014, 04:46 pm

My confusion lies in the baffle dimensions. As you said to look around, I have and am confused. Are there set values? Like a certain amount of surface area, or square footage yields certain baffle rolloff? Or it seems more that the distances from the driver to each edge decide baffle rolloff?

There is science behind all of this for sure. But there is no single answer. The sounds that we hear are stretching over 10 octaves, human sight is only covering one. That makes baffle design a work of compromises. If you want to understand how to deal with that, you need to start with http://www.linkwitzlab.com/models.htm#A and http://www.linkwitzlab.com/models.htm#B, add http://www.linkwitzlab.com/frontiers.htm#B, move to http://www.linkwitzlab.com/faq.htm#Q14 and jump to http://www.musicanddesign.com/Equivalent_Baffles.html. You even might have a look at my view of things and download "How open baffles work" from http://www.dipolplus.de/thema11.php. At least that is what I would recommend to a science student.

Rudolf

ShawnL · « **Reply #7 on:** 13 Dec 2014, 08:06 pm »

Oh wow, I really appreciate that. I'm exited to read your paper as the layout looks excellent.

This will give me something to dive into once my last exam is done next week.

Thank you!
Shawn

JohnR · « **Reply #8 on:** 15 Dec 2014, 11:11 am »

In addition to reading Rudolf's paper, The Edge is fun and will give you a good idea what to expect. -> http://www.tolvan.com/edge/

120 Hz is probably unrealistic for a small driver like the NS3. You may also like to model your project after Martin King's (or at least read his report) -> http://www.quarter-wave.com/Project08/Project08.html

ShawnL · « **Reply #9 on:** 16 Dec 2014, 11:02 pm »

Thanks for the reply John!

I've started to do some reading on all the links offered. So far I have one question. What is the highest or most ideal point(s) recommended to cross over the sealed woofer to the OB without causing unwanted changes in sound due to the different baffle/box types/position of drivers.

Thanks
Shawn

Rudolf · « **Reply #10 on:** 16 Dec 2014, 11:19 pm »

Quote from: ShawnL on 16 Dec 2014, 11:02 pm

What is the highest or most ideal point(s) recommended to cross over the sealed woofer to the OB without causing unwanted changes in sound due to the different baffle/box types/position of drivers.

There is probably no single best answer, but I would vote for the Schroeder frequency, the transition frequency from discrete room modes in your room to a continuous reverberant field. Another possible point would be the baffle step region of your woofer.

ShawnL · « **Reply #11 on:** 16 Dec 2014, 11:44 pm »

Is there a certain region where the switch from an open baffle to sealed box will produce an unwanted transition? I've seen hints of this on the interweb.

ShawnL · « **Reply #12 on:** 17 Dec 2014, 12:03 am »

Also, using Edge for modelling, what are the point sources and speaker density?

I looked on the website but the explanation was unclear to me.

I appreciate your help in schooling me, I do not have much knowledge in this field, but would like to gain a practical amount in order to build some speakers and have a little fun.

JohnR · « **Reply #13 on:** 17 Dec 2014, 02:20 am »

Quote from: ShawnL on 17 Dec 2014, 12:03 am

Also, using Edge for modelling, what are the point sources and speaker density?

It's the number of points used by the simulation to approximate the baffle and driver. If you're asking what the number should be, don't know off hand but if you increase it and nothing changes then you don't need to go further. If set too high the simulation will slow down too much.

ShawnL · « **Reply #14 on:** 29 Jun 2015, 07:36 pm »

Well it's been a while but I am going to be building the speakers tonight. I'll ask a question now and maybe I will get a response in time.

The actual open baffle will be 160cm tall and 26cm wide. The 3 inch aurasound ns3 will be 100cm high and offset near the edge. For midbass/bass I will have a 20 liter sealed box attached to the bottom holding the 8 inch Seas p21re driver.

Here is my question

I would like to extend the 160cm baffle by approx. 25-30 cm so that it is also the front baffle for the midbass driver situated at the bottom. and then just build a 26 x 25-30ish cm box behind it. Does anyone see a problem with having such a large front baffle for the 8 inch driver? or any other problems for that matter?

Just to refresh anyone's memory the speakers will be bi-amped and all crossover work will hopefully be handled well by Audyssey. The 8 inch drivers will be recognized as subwoofers and I am expecting a crossover around 200hz

I appreciate any feedback
Thanks
Shawn

mcgsxr · « **Reply #15 on:** 29 Jun 2015, 09:50 pm »

If your specific question is about the possible effect of the wide baffle on the sealed 8 inch sub, I would say not an issue.

Operating at or below 200Hz, I'd think that's fine.

Good luck with the initial build, snap a few pics for those of us watching with interest!