[mayhem13]

PLEASE READ FIRST BEFORE VOTING!


Ok, so as some might be pleased to hear, the results of the max SPL and efficiency polls have painted this design into a bit of a corner where bass extension is concerned. There appears to be a limited amount of 8-10" drivers that could fulfill our goals in a sealed alignment and while they are excellent candidates they have some tradeoffs in the areas of enclosure size and cost. If we were to include the option of a ported alignment we would be able to include a host of Proffesional use 8-10" drivers that are both efficient and cost effective and would allow for the use of a single unit, reducing overall enclosure size. These drive units can provide excellent LF extension to 60hz and remain completely linear while doing so. This begs the question if we are willing to trade away the advantage of a sealed alignment blend to the subwoofer system. Basically it's a matter of individual priorities so i ask that you cast a vote once more before we begin driver selection.


So i may remain neutral, i ask other AVS members to please post informative Pros and Cons of both Ported and Sealed alignments considering the maximum driver diameter supported by this design is 10". Discussions of larger diameter drivers are irrelevant to the discussion at hand so please refrain from including those options.

 

[Jay1]

I'm all for ported considering the intentions (high output HT) and restrictions (size, budget) of this design. I don't have a problem integrating my 55hz ported speakers with a sub, so I don't see that aspect as a negative.

 

[LTD02]

ported is a resonant system. whether that matters, who knows.


ported reduces distortion as driver movement is lower as tuning frequency is approached.


ported requires a high pass to protect it.


both can sound good. both can sound crappy.


parham likes ported. geddes likes sealed. jbl's totl use ported.


an interesting argument for sealed mains comes from geddes, who likes the shallow rolloff of sealed in that they can help smooth room modes and for most folks, room modes are a big problem in the bass.

 

[LTD02]

why not something like this mayhem?

http://www.jblsynthesis.com/products...=US&Region=USA

http://manuals.harman.com/JBL/HOM/Qu...F%20QSpecs.pdf

 

[LTD02]

maybe you are looking for something like the usher 8955a driver?


a pair in a 2 cubic footer sealed have an f3 of about 57hz.


not exactly my cup of tea, but it seems to fit your requirements.

 

[mayhem13]



Quote:
Originally Posted by LTD02 /forum/post/16873411


why not something like this mayhem?

http://www.jblsynthesis.com/products...=US&Region=USA

In essence, that's what the original design would have strived for with the use of 2 Hifi 8" woofers such as the SEAS CA22RNX yet would have had much lower bass extension. The JBL system looks to have an F10 of 60hz which unfortunatley doesn't meet our requirements. The dual SEAS option mentioned would have slightly higher efficiency with BSC and an F3 of 55hz but would struggle to remain linear at higher output at 60 hz. If we were to assume an 80hz XO to the subs, then this wouldn't be a problem. Also quite cost effective at around $160 USD per pair.


Truthfully considering a ported alignment without actually testing my design, a pair of Silver Flute W20RC38-08 woofers ported and tuned to 50hz in 45L is the most cost effective yet efficient option i've come across. If the specs are to be believed, this is one hell of a driver for the cost. Considering a 6.5" mid driver, we would only need to run these to 250-300hz in a three way which would discount most if not all cone breakup which given such a light cone i dooubt is even a consideration. Please take a look at the links and do the simms for yourself.....i had to recheck the T/S myself as i didn't believe it the first time. The other plus to a parallel pair of these is Z remains at near 4ohms through the passband where other Hifi 8's go well below which may be a problem for some amplifiers.

 

[mayhem13]



Quote:
Originally Posted by LTD02 /forum/post/16873459


maybe you are looking for something like the usher 8955a driver?

Unfortunaley given BSC, not efficient enough in parallel, Z a bit low and not very cost effective at $227 per pair. This is precisely why i'm looking for feedback for ported. A single B&C 10NDL64 ported outperforms a pair of Ushers for less money in a smaller box as does several other B&C 10" drivers. Even the 8NDL51 is an option ported, and this is one excellent speaker i might add. Not the prettiest thing to look at though.

 

[dlneubec]

I voted ported, as before, because I think you will need it to meet all your other requirements. The Silver Flute may be good, but how high can in go without getting into breakup or distortion? Is it good to 1khz, 1.5khz, 2khz? I have my doubts that it can cross over high enough. It is a rare 8" HiFi driver that can and it it does, what will the critical midrange sound like?


I repeat my suggestion from about a month ago. Do an MTM using the 18sound 6ND430-16 paired with the SB-Acoustics SB29RDC-C000-4 Ring Dome tweeter. The total cost of the drivers would be about $620/pair, leaving $130 for passive crossovers. Estimated crossover point around 2.5khz. The MTM configuration will reduce floor and ceiling bounce. A pair of the 6ND430's can get you and F3 of about 68hz ported in about 34 liters, assuming a 4" dia port about 4-7/8" long and a 2nd order butterworth highpass at 60hz, and up to about 117db before overexcursion at 150w. The cabinet width could be as little as 9" or so. The 6ND430 is available in 16, 8 and 4 ohm versions, I believe.
http://www.eighteensound.com/index.a...roduct&pid=243
http://www.madisound.com/catalog/pro...oducts_id=8540


If you check out Zaphs tests of these drivers you will see that they are extremely low distortion and should yeild a decent sensitivity in the low 90's, depending on the amount of BSC applied.

http://www.zaphaudio.com/6.5test/
http://www.zaphaudio.com/tweetermishmash/

 

[penngray]

I still think waveguides or coaxial designs would make AVS unique in its signature build.


I would love to have a DIY version of Mark Seaton's Sparks or even his higher end Catalysts. The Spark designs would easily fit under the buget...I would buy the Hpex amps for my design though

I wonder what Coaxial driver Mark uses in the Spark design?

 

[cc00541]

I often choose a vented alignment that emulates the rolloff of a sealed design down to f10 or so. Generally this results a small enclosure with a low tuning, and if the port is plugged, an acceptable Qtc. Sometimes you can have your cake and eat it too.

Here is a link to an article that may have some bearing on the present discussion.


C

 

[Ricci]

I voted no preference again. I still believe that it's best to leave the option open so that more combinations of drivers can be considered. I'd prefer sealed even if it came at the cost of a bit higher F3, but either can work if done right. If ported gets the job done better within the framework of the designs goals, so be it. Let the drivers dictate it.

 

[penngray]



Quote:
Originally Posted by Ricci /forum/post/16875178


I voted no preference again. I still believe that it's best to leave the option open so that more combinations of drivers can be considered. I'd prefer sealed even if it came at the cost of a bit higher F3, but either can work if done right. If ported gets the job done better within the framework of the designs goals, so be it. Let the drivers dictate it.

+1


I voted no preference for the same reason but Ricci explains things better then I do

 

[Looneybomber]

As of right now


Sealed: 7

Ported: 7

No pref: 6


Lawl.


I voted no preference because I don't know what the design's going to end up being. If it's small enough, but with sufficient output, I will put this design on top of my TD15h bass bins. So I'd make them sealed. If not, I'd make them ported since they wouldn't be used with a bass bin.


My prior vote was vented.

 

[lennon_68]



Quote:
Originally Posted by penngray /forum/post/16875181


+1


I voted no preference for the same reason but Ricci explains things better then I do

Quote:
Originally Posted by Ricci /forum/post/16875178


I voted no preference again. I still believe that it's best to leave the option open so that more combinations of drivers can be considered. I'd prefer sealed even if it came at the cost of a bit higher F3, but either can work if done right. If ported gets the job done better within the framework of the designs goals, so be it. Let the drivers dictate it.

+2 (or is it +3 with Looneybomber). Voted sealed last time and would prefer it but don't care enough either way that it would be a dealbreaker for me.

 

[mjg100]



Quote:
Originally Posted by Ricci /forum/post/16875178


I voted no preference again. I still believe that it's best to leave the option open so that more combinations of drivers can be considered. I'd prefer sealed even if it came at the cost of a bit higher F3, but either can work if done right. If ported gets the job done better within the framework of the designs goals, so be it. Let the drivers dictate it.

I voted ported, but I agree with this. An F3 of 80Hz sealed would be fine with me also.

 

[Monger]



Quote:
Originally Posted by penngray /forum/post/16874578


I still think waveguides or coaxial designs would make AVS unique in its signature build.


I would love to have a DIY version of Mark Seaton's Sparks or even his higher end Catalysts. The Spark designs would easily fit under the buget...I would buy the Hpex amps for my design though

I wonder what Coaxial driver Mark uses in the Spark design?

It's the B&C 8cxt.


I came so close to pulling the trigger on those hypex amps. With shipping they come in at around 400 a piece though. I think I'll just stick with the xpa5 and dcx.

 

[mjg100]



Quote:
Originally Posted by penngray /forum/post/16874578


I still think waveguides or coaxial designs would make AVS unique in its signature build.


I would love to have a DIY version of Mark Seaton's Sparks or even his higher end Catalysts. The Spark designs would easily fit under the buget...I would buy the Hpex amps for my design though

I wonder what Coaxial driver Mark uses in the Spark design?

I agree the Sparks should be doable and I would love to see a DIY version of them. Small size so they would fit in most any room. Are there any specs showing what this speaker can do? Is it the same 8" coaxial as in the Catalysts? What 1" HF driver is used?

 

[mayhem13]



Quote:
Originally Posted by cc00541 /forum/post/16874724


I often choose a vented alignment that emulates the rolloff of a sealed design down to f10 or so. Generally this results a small enclosure with a low tuning, and if the port is plugged, an acceptable Qtc. Sometimes you can have your cake and eat it too.

Here is a link to an article that may have some bearing on the present discussion.


C

Great read Curt.....thanx for the link. I hope all who plan on voting read it before doing so. I faithfully remain nuetral.

 

[mayhem13]



Quote:
Originally Posted by dlneubec /forum/post/16874245


I voted ported, as before, because I think you will need it to meet all your other requirements. The Silver Flute may be good, but how high can in go without getting into breakup or distortion? Is it good to 1khz, 1.5khz, 2khz? I have my doubts that it can cross over high enough. It is a rare 8" HiFi driver that can and it it does, what will the critical midrange sound like?


I repeat my suggestion from about a month ago. Do an MTM using the 18sound 6ND430-16 paired with the SB-Acoustics SB29RDC-C000-4 Ring Dome tweeter. The total cost of the drivers would be about $620/pair, leaving $130 for passive crossovers. Estimated crossover point around 2.5khz. The MTM configuration will reduce floor and ceiling bounce. A pair of the 6ND430's can get you and F3 of about 68hz ported in about 34 liters, assuming a 4" dia port about 4-7/8" long and a 2nd order butterworth highpass at 60hz, and up to about 117db before overexcursion at 150w. The cabinet width could be as little as 9" or so. The 6ND430 is available in 16, 8 and 4 ohm versions, I believe.
http://www.eighteensound.com/index.a...roduct&pid=243
http://www.madisound.com/catalog/pro...oducts_id=8540


If you check out Zaphs tests of these drivers you will see that they are extremely low distortion and should yeild a decent sensitivity in the low 90's, depending on the amount of BSC applied.

http://www.zaphaudio.com/6.5test/
http://www.zaphaudio.com/tweetermishmash/

Hey Dan. Nice to hear from you again. As indicated in earlier polling, this is a three way design, so a Pro Mid is a strong consideration given the needed outout and efficiency. Personally i'd like to see the XO up to 3khz and beyond and i think resurrecting the old TMW might be in order. Now the arguement is probobly why bother with 3way when subs are used and it's partially valid. I say let's look outside of conventional wisdom and look for a midrange driver capable of extremely low HD and flat FR from 400-3khz. Using the dedicated midrange driver allows us to do that at very high output levels. My only concern with using these types of driver for below 300hz comes down to linearity at high output levels. While Zaphs's HD plots show low HD products of all orders for the 18Sound, i fear the results would be quite different once this driver approached Xmax, while a driver of larger diameter and even low VC inductance would remain free of audible HD down to the tuning frequency. Such a driver could be used effectively in a WMTM as well with a pair of 5" mid drivers with high Fs who would never see excursion above .5mm and would not likely beam into the 3 khz range. All things to be considered during the selection phase.....hope to see you there!

 

[mayhem13]



Quote:
Originally Posted by cc00541 /forum/post/16874724


I often choose a vented alignment that emulates the rolloff of a sealed design down to f10 or so. Generally this results a small enclosure with a low tuning, and if the port is plugged, an acceptable Qtc. Sometimes you can have your cake and eat it too.

Here is a link to an article that may have some bearing on the present discussion.


C

Curt's findings prove to be even more interesting to me after a second read.


Follow for a second. If we suppose that his observations are true and put them into play by example there's some other added benefits as well. Consider the Silver Flute 8" woofer i've been mentioning. We find through Unibox sims that in 45L ported a parallel pair is capable of 114db output through it's passband and remains at 93db efficiency with full BSC. If we consider Curt's sugegstions as well, lowering the tune to 40hz, the F3 remains within spec at 63hz but power handling hasn't suffered. Probobly even more important is the 1st port resonance is non existant with a single 3" vent which is only possible at this kind of output because the port air speed or excess therof is well below the XO point to the subs. Given a standard 12db/oct filter at 80hz, the port contributes little to nothing to the audible output where Curt's discussions on reduced group delay should hold true. Basically between the LP filter to the woofers and the HP filter of the AVR, this type of alignment basically eliminates most of the negatives of a ported aligment yet allows for a small enclosure and hig power handling. Bravo Curt!