3-way active dedicated stereo listening

Guiria

Guiria

Senior Audioholic
Another design data point that has me inquiring. The 1st port resonance at the above spec'd enclosure and tuning is around 218 Hz. I plan on crossing the subwoofer over at 300-350 Hz and if I'm not mistaken a general rule of thumb is having the 1st port resonance pushed at least 1 octave above the crossover frequency which would never happen in this case. Makes me think I'm back to the drawing board a little bit for design. This sub would have to use the passive radiators or be sealed.
 
TLS Guy

TLS Guy

Audioholic Slumlord
Another design data point that has me inquiring. The 1st port resonance at the above spec'd enclosure and tuning is around 218 Hz. I plan on crossing the subwoofer over at 300-350 Hz and if I'm not mistaken a general rule of thumb is having the 1st port resonance pushed at least 1 octave above the crossover frequency which would never happen in this case. Makes me think I'm back to the drawing board a little bit for design. This sub would have to use the passive radiators or be sealed.
How long is your port? If what you say is correct, then make the port slightly smaller and accept a slightly higher air vent velocity. Make sure the port is flared. Which driver are you using? May be I should model it as a TL for you. That might be your best solution of all.
 
Guiria

Guiria

Senior Audioholic
How long is your port? If what you say is correct, then make the port slightly smaller and accept a slightly higher air vent velocity. Make sure the port is flared. Which driver are you using? May be I should model it as a TL for you. That might be your best solution of all.
Current vent is 31x10.5x1.5”. I can play around with the vent size but driving the vent resonance up to 600 hz might not be achievable. The driver I’m currently modeling is a css sdx10. Here is a link to manufacturers site and the TS parameters.


T/S Parameters

Fs: 30.0 Hz

Qes: 0.63

Qms: 3.69

Qts: 0.54

Vas: 34 Liters

Re: 3.5 Ohms

Xmax: 18.4 mm

Sd: 330 cm^2

Le: 1.42 mH

BL: 11.8 NA

Mms: 112 g

SPL: 87.2 dB @ 2.83V/1M

A TL would be interesting, certainly not opposed to the idea.


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TLS Guy

TLS Guy

Audioholic Slumlord
Current vent is 31x10.5x1.5”. I can play around with the vent size but driving the vent resonance up to 600 hz might not be achievable. The driver I’m currently modeling is a css sdx10. Here is a link to manufacturers site and the TS parameters.


T/S Parameters

Fs: 30.0 Hz

Qes: 0.63

Qms: 3.69

Qts: 0.54

Vas: 34 Liters

Re: 3.5 Ohms

Xmax: 18.4 mm

Sd: 330 cm^2

Le: 1.42 mH

BL: 11.8 NA

Mms: 112 g

SPL: 87.2 dB @ 2.83V/1M

A TL would be interesting, certainly not opposed to the idea.


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I will play with that driver tomorrow. The Qts is on the high side for any loading except sealed. Honestly I tend to stay clear of drivers with a Qts above 0.4. That is an impossibly long port for what you want to do. I agree with the late Raymond Cooke founder of KEF that the sweet spot for bass drivers is Qts 0.3 to 0.4. His drivers were usually O.35 or close.
 
Guiria

Guiria

Senior Audioholic
I will play with that driver tomorrow. The Qts is on the high side for any loading except sealed. Honestly I tend to stay clear of drivers with a Qts above 0.4. That is an impossibly long port for what you want to do. I agree with the late Raymond Cooke founder of KEF that the sweet spot for bass drivers is Qts 0.3 to 0.4. His drivers were usually O.35 or close.
How about something like this for a TL?


Or buying a pair of these and using a slot vent.


I’ll have to model some other drivers as well.


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TLS Guy

TLS Guy

Audioholic Slumlord
How about something like this for a TL?


Or buying a pair of these and using a slot vent.


I’ll have to model some other drivers as well.


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If you want to use a Dayton Sub driver this is the one to use for your project. I have used this in my great room system. It is one of the most perfect drivers for TL application. It works fabulously.

Here are the details of that system, including the measurements of that driver in the in wall TL. I will try and look for the file to get you the pipe dimensions and stuffing weight. That would make a really impressive three way active speaker.
 
Guiria

Guiria

Senior Audioholic
If you want to use a Dayton Sub driver this is the one to use for your project. I have used this in my great room system. It is one of the most perfect drivers for TL application. It works fabulously.

Here are the details of that system, including the measurements of that driver in the in wall TL. I will try and look for the file to get you the pipe dimensions and stuffing weight. That would make a really impressive three way active speaker.
Thanks. I’ll look forward to seeing your TL specs.


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TLS Guy

TLS Guy

Audioholic Slumlord
First of all I sent you the wrong driver link. This happened because I have the wrong link on page describing the in wall system. Sorry about that.

This is the driver you need.

These are the build pictures of the speaker.





The plan is below.



Now what you will need to do is put the driver on the adjacent face by turning it 90 degrees. The internal depth of the cabinet is 12"". Now you may want to widen that dimension to make room for the driver on that different face. This you can do.

Pipe length Pl is 3'

The taper is 3:1.

The pipe volume Vp is 120 liters. So it is about a 4.25 cu.ft enclosure.

The beginning of he pipe (closed end) is 600 sq. cm.

The exit area (open end) is 250 sq.cm.

Stuff with polyfill from Walmart. The weight should be 960 GM, about a KG, which is 2.25 pound near enough. Distribute it evenly throughout the pipe, but keep it a little short of the exit. I staple netting around it to stop it settling. I do not use glue as it hardens the polyfill. I do not directly staple the polyfill as it compresses it.

That makes for an impressive and excellent sounding bass system. You can mount the mid and tweeter above the woofer. This maintains excellent output to 20 Hz.

I don't think you will need a sub. Since you are biamping you can blend in the LFE signal with the low pass output from your crossover.
 
Guiria

Guiria

Senior Audioholic
The design looks great, however, I think the size will be a gating item for them in my situation. They will be placed in an upstairs bonus room that has a sloping ceiling line and the 61” height would make them just a few feet apart. My current design height is closer to 48” which will give me more separation and better stereo imaging.

Going through this design makes me think of a few things.
1: An extended 3 way is actually very challenging.
2: Could turn this in to a 4-way design as I now see first hand the benefit from that. This ends up requiring additional amplification and drivers, is it really worth it for my first tower speaker DIY.
3: Maybe I keep it a 3 way, not chase extension and just add a stand-alone subwoofer.
4: Maybe I rebuild my 2-ways ported and just add stereo subs.

Guess I’ll sleep on it.


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annunaki

annunaki

Moderator
Looking closer at the CSS SDX10. If I went with the Parts-Express tune recommendation of 27Hz in 1.69 cubic feet I calculated a port size of 10.5"x1.5"x31" with max air velocity being around 15 m/s @ 200W input power. My box outer dimensions would be 36"x12"x14" for the sub.

The box could be a little smaller with the passive radiators, I haven't spec'd that out yet. Is WinISD alpha accurate for PR modeling?
It is accurate so long as you input the numbers for the PR accurately. Best way to do it is model the ideal vented enclosure and then adjust volume and added mass on the PR to match. The only difference is the steeper roll off with PR vs vented.
 
annunaki

annunaki

Moderator
Javad Shadzi used the CSS SDX10 with dual APR-10 in his Enthraals speaker design with great success. That would be worth looking into for a proven design concept with that driver.

 
Guiria

Guiria

Senior Audioholic
I think I have come to my acceptance of compromise for the design.

I'm going to build my midrange ported which gives me an f3 of 75Hz with a 2.0 x 4.4 port, box size is 0.25 cubic feet. With a crossover frequency around 200 Hz or so I'm not worried about port noise with that small of a port.

I'm going to use the Dayton 10" HF 4 ohm tuned to 27Hz in a 1.68 cubic foot box. A slot vent of 10.5x1.25x25.5" gives me a first port resonance around 264Hz and with 300W total power that puts the max air velocity at 25 m/s. If I put a 20Hz highpass filter on the driver to protect from unloading beneath the port tune it reduces the max air velocity even more (with decreased output as well). I'll have a pair of them in a normal sized room without vaulted ceilings so I probably would rarely be driving them hard enough to pull the 300W anyways.

At the end of the day the aesthetics of the 3 driver design with a slot vent is a driving factor. I never could settle in on the CSS with PR design and I've always wanted to use the Dayton HF line for something so that tips my choice as well. I'll be getting a model finalized in sketchup and post that if I can figure out how ;)

Comments, design flaws, etc I'm still open to discuss.
 
annunaki

annunaki

Moderator
What is your crossover on the Dayton to the Mid? What is the projected response bump from the vent resonance? If that is not adequately suppressed you may have to add a notch filter in your design or lower the cover point to 150hz-100hz to help reduce the impact. Just a thought.
 
Guiria

Guiria

Senior Audioholic
What is your crossover on the Dayton to the Mid? What is the projected response bump from the vent resonance? If that is not adequately suppressed you may have to add a notch filter in your design or lower the cover point to 150hz-100hz to help reduce the impact. Just a thought.

2 octaves above tuning frequency of mid would be 225hz. If I were to try and be 1 octave below the port resonance then really I would crossover below 190hz. I think I'll try it a couple different ways and see what models best once built.

I'm using WinISD pro alpha and not sure I can measure the projected bump from vent resonance.

I've tried to gather reliable information about 1st port resonance. Seems that if you are modeling resonance of something the materials would need to be considered as a plastic port is not going to resonant the same as 3/4" wood so the generalized "1st vent resonance" seen in WinISD has me scratching my head a little.

Enlighten me.
 
Guiria

Guiria

Senior Audioholic
Calculating the 1.5" bracing, the current box comes out to 2.1 cubic feet, which lowers the tune of my box by a couple of hz if I leave the port the same 25.5" long. The outer dims on this are 36x12x14.5" I will be working on my 2-way enclosure next, which is a wedge type design.
View attachment 35648
 
annunaki

annunaki

Moderator
If you can keep the vent resonance out by a full octave from the crossover point and are using at least a 2nd order filter I don’t think you will have anything to worry about. You would already be down by 12db and even with say a 3db bump in response from the resonance, it will not likely be audible at that point.
 
Guiria

Guiria

Senior Audioholic
Couple of box design questions.

When considering bracing, does it matter that you are literally breaking up the space in which the back wave of the loudspeaker travels. If done too much could this cause some kind of compression and affect the tune of the enclosure? Case in point I have a shelf brace planned with (4) 3x3.5” holes that allow access to the rest of the cabinet below. Does this cause a problem?

Also does anyone have a good article or forum discussion regarding polyfill in a bass reflex enclosure and how much should be used? I feel like I’ve read up on this in the past but that knowledge has since fled my mind.


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annunaki

annunaki

Moderator
Ideally, your bracing scheme should tie all 6 panels together. Using the shelf brace you mentioned will be fine.

50% fill is fine, but why are you using it? If it is about taming reflections, you are better off to use Rockwool/Thermafiber wrapped in a breathable fabric. Denim based insulation is also fairly decent if you have no access to the others.
 
Guiria

Guiria

Senior Audioholic
Ideally, your bracing scheme should tie all 6 panels together. Using the shelf brace you mentioned will be fine.

50% fill is fine, but why are you using it? If it is about taming reflections, you are better off to use Rockwool/Thermafiber wrapped in a breathable fabric. Denim based insulation is also fairly decent if you have no access to the others.
Yes I forgot about Rockwool. Really it would be for behind the 10” driver to help with the back wave. If I used Rockwool I’d probably place some on non opposite panels within the enclosure as well and would definitely use it on the midrange enclosure.

I would not want to over dampen the box and kill the effectiveness of the port.


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annunaki

annunaki

Moderator
Yes I forgot about Rockwool. Really it would be for behind the 10” driver to help with the back wave. If I used Rockwool I’d probably place some on non opposite panels within the enclosure as well and would definitely use it on the midrange enclosure.

I would not want to over dampen the box and kill the effectiveness of the port.


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In vented enclosures I have done, I placed the rockwool on the back but not, the front, top but not the bottom, and left but not the right. It provides about 50% coverage of reflective surfaces and I have had no issues with over damping for the vent. The bracing scheme can also help break up the rear waves some also.
 

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