Is there interest in a large three way "monkey coffin" collaboration?

[ngjockey]

Re: Is there interest in a large three way "monkey coffin" collaboration?

By comparison, I recently modelled a 8" powered sub for 40 Hz sealed and you could fit 3 of them inside a box that size. This project is making less sense.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

You are definitely right that the small signal models we use don't hold up at higher signal levels. But all the relatively cheap drivers we are looking at will probably decompensate similarly when pushed.

Do you know of a 15" that will work OK in a vented cabinet of the size we have in mind (about 100 liters give or take) and give a reasonable degree of extension. I hear you about the AVR's at 4 ohms. Is there a consensus here that we need to stick with 8 ohm woofers only? To be fair a 90 db sensitive box will be doing 100 db with 10 watts which is only 80 watt peaks assuming a 9db of crest factor.

I think spending a little more on the woofer is worth it if it helps. I mean I think the 6" Faital and the Vifa BC25SC06 would both work fine for this project and are very affordable. That in my mind frees up a little extra for the woofer.

8 ohms 15" ported might be a compromise or a better 12" ported woofer that digs deeper and is more efficient but costs more is another thing to play with. I'm thinking Xmax should be at least as low as 30 Hz and 105+ dB and I can see it taking 50+ watts @ 8 ohms to get there. I know that takes more copper in the XO, and hurts the "price point", but the dynamic impedance of a "4 ohm" woofer at high SPLs will shut down many AVRs who's power supplies are a bit marginal. I'm not that smart. I've been reading some of Tympany's "white papers" on some of their woofers. (Google translate from Chinese now.) At 1 watt, a driver reads the "spec sheet" graph. At 30 watts, it usually doesn't.

Ngjockey's idea I thought of too. It's a tough one. One 500 watt plate amp pushing two 15" 8 ohm subs are going to kill almost any 3-way with a 15" woofer unless you have a 250 WPC amp (OUCH!), but it blows the budget too.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

12 CF is 3 to 4 times the size I've been thinking of...

For any lurkers who like the idea but are willing to go bigger, take a look at this PRV 15 ($68.99; fs = 30, Qts = .59, Vas = 7.92 ft3)...

http://www.parts-express.com/prv-audio-15w700-15-high-power-pa-woofer-8-ohm--294-2740

12 ft3 sealed gets you down to 30 @ -6db. You can go vented, you can go smaller (more ripple of course). Then again you could run 2 in 24 ft3...for those of us in a position to regard ManCave and WAF as pertaining to separate magisteria.

John

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

An 8" that hits 40 hz sealed in 1 CF or so must not be terribly efficient.

I think the idea of a project making sense or not is all in the eye of the beholders.

There are many ways to skin a cat.

As far as the DC380 failing to dig very deep sealed, you are correct that it won't break an F3 of 40. If you put a DC380 in 100 liters vented tuned low at 20 hz you get a sealed type rolloff but with more LF extension and better control of excursion. In that box the DC380 will handle 50 watts without breaching excursion and has F3/F6/F10 of 35/28/21 and will do just shy of 108 db. Honestly that would probably work just fine for this. I think several other woofers would work fine too. Perhaps its paralysis by analysis going on here...

Here is the DC380 in the above mentioned box



The DS315-8 actually does look really nice in about 80 liters vented with Fb 27 hz. F3/F6/F10 of 27/24/20. Max output 107 db. Handles 75 watts before hitting xmax limit.



And then here is the ST305-8 Series II 12" in 100L with Fb of 30. It gives F3/6/10 of 29/26/22. Max output of 112db. Handles 140 watts before exceeding xmax. WBCD calculates the sensitivity at 90 db. That seems like a real solid choice to me. Who agrees with this LF driver and alignment? Solid 30 hz extension, reasonably good sensitivity, good power handling and decent xmax. Who was it that suggested it earlier? It seems like the right choice to me.

By comparison, I recently modelled a 8" powered sub for 40 Hz sealed and you could fit 3 of them inside a box that size. This project is making less sense.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

My DCS380 model was in 100 liters, with Qa of 6 which is a densely stuffed box. It gave Qt of .75 for the system.

Unfortunately, my calculator shows the DC380 coming up a bit a few shy of 40 Hz sealed and the DCS380 requiring a much bigger box, unless you want a Qtc around 0.9. Done 0.8 before with 6.5's and that wasn't bad. The DS315, ported, only requires about 2/3 that box and shows a F3 around 34 Hz but I haven't figured out how it models for a larger box. Wasn't that done already? Advantage there, either wider or shorter port

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

I think the Series II woofer I posted the alignment for above matches your idea of a compromise that is a better 12" woofer in a ported box.

I am all in on the ST305.

Who agrees?

8 ohms 15" ported might be a compromise or a better 12" ported woofer that digs deeper and is more efficient but costs more is another thing to play with. I'm thinking Xmax should be at least as low as 30 Hz and 105+ dB and I can see it taking 50+ watts @ 8 ohms to get there. I know that takes more copper in the XO, and hurts the "price point", but the dynamic impedance of a "4 ohm" woofer at high SPLs will shut down many AVRs who's power supplies are a bit marginal. I'm not that smart. I've been reading some of Tympany's "white papers" on some of their woofers. (Google translate from Chinese now.) At 1 watt, a driver reads the "spec sheet" graph. At 30 watts, it usually doesn't.

Ngjockey's idea I thought of too. It's a tough one. One 500 watt plate amp pushing two 15" 8 ohm subs are going to kill almost any 3-way with a 15" woofer unless you have a 250 WPC amp (OUCH!), but it blows the budget too.

[andy19191]

Re: Is there interest in a large three way "monkey coffin" collaboration?

I am all in on the ST305.

Who agrees?

The objectives for the speaker are still not clear. Is it supposed to be:
- a big, efficient, loud, easy to drive monitor that surrenders a bit of deep bass
- a big speaker that delivers deep bass and surrenders efficiency

If the objective is the former then for less than $100 in a 100 litre box the ST305 looks a significantly more suitable driver than the other two Dayton drivers that were discussed earlier. I don't know about drivers from other manufacturers. If this driver is selected then reducing the box size 25% or so is an option to consider.

The $44, 8 ohm, 95dB, 130W, 6", FaitalPro 6FE200 looks reasonable. I am not familiar with the alternatives at this price point and so this is not meant as a recommendation. Perhaps pencil it in, move to the next step and see if that throws up a reason it might need changing.

The $16, 4 ohm, 96dB, 25W, 1", Vifa BC25SC06 looks a less reasonable choice. The 25W power handling looks too low for a big monitor. Also it might be a pity to spoil an 8 ohm design with a 4 ohm tweeter and so perhaps a 6 or 8 ohm.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

Andy, when you say...

The objectives for the speaker are still not clear. Is it supposed to be:
- a big, efficient, loud, easy to drive monitor that surrenders a bit of deep bass
- a big speaker that delivers deep bass and surrenders efficiency

I look at post #104 where I said

I feel like the concept fits for sensitivity in the 90 db plus or minus 2db range. I also would think enclosure of 100 liters net plus or minus 15 liters will work just fine with this form factor. Finally I would think LF extension of F3 below 40 sealed and around 30 vented would be great targets. I also think with the whole vibe of the design a goal of 108 db or higher sustained output (on paper at least) would be reasonable. I think nominal 8 ohm impedance would be a plus but perhaps not mandatory. I feel like 12" or 15" woofer is the way to go if just for the reason of aesthetics and feel. Plus big cones do bass well especially when the drivers are on the cheap side.

For me that is all I have for goals for this design. My main goal however was to get anyone who wished to join in involved so we could come up with something that may appeal to a fair number of people.

I don't feel like 3 db of efficiency one way or the other makes a tremendous difference really so 89 db vs 92 db while a noticeable difference doesn't matter so much as a definite design objective for me. What do others think? Personally I'd pick 89 db and able to solidly to down close to 20 hz than 92 db and able to go only to 35hz. It seems that several others have chimed in however that they would rather focus on a little more efficiency than on the last 10 hz of LF extension. I think overall that is probably a good way to go. I think most people would agree that 30 hz F3 for a vented woofer for this design should be plenty of LF extension even though we could get an extra 1/2 octave or so by choosing the DCS-305 vented. So, thanks for the suggestion of the ST-305.

I do think your mention of "easy to drive" is probably pretty important and has been mentioned by others. In my mind that is the main reason to go away from the DCS-305 and the DCS-380 both of which will dig pretty deep in 3-4 CF but give up around 3db of efficiency to the ST-305.

As far as the mid, I looked around a lot and it was hard to find mids at a reasonable price (again $500 goal for parts including crossover parts for a pair of speakers) that would offer adequate sensitivity to match up with a 92 db woofer. I would love to hear suggestions from folks here. Also as I am not a crossover designer, how much sensitivity do we need from the mid if we have a 92db woofer, a 15" wide baffle and want something approaching full BSC?

For the tweeter, I think your point is well made. The Vifa is cheap and efficient, but the 4 ohm rating and it's lower power handling would both limit the design. Suggestions anyone?

Andy, where at in Europe are you?

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

In light of Andy's tweeter observations here are a couple possibilities

http://www.madisoundspeakerstore.com...weeter-4-ohms/
This is SB is 4 ohm and costs a fair bit but will have plenty of sensitivity, plenty of power handling and is extremely well regarded lately.

http://www.madisoundspeakerstore.com...22tff-tweeter/
This Seas is 6 ohm and also stretches the budget but should have sensitivity that is in the ballpark and does handle plenty of power.

http://www.madisoundspeakerstore.com...-dome-tweeter/
This Scan Disco is also 6 ohm and has probably adequate sensitivity and power handling. Still at the top of the budget.

http://www.parts-express.com/vifa-xt...eter--264-1012
This Vifa would probably fill the bill as well.

What other tweeters might work here on a budget of say $40 max per tweeter?

[Mayhem13]

Re: Is there interest in a large three way "monkey coffin" collaboration?

When looking at bass response, it's important to remember the sims are anechoic, which don't take into account the likely 6-8 db boost below 30hz common in most 'home' spaces.

when i initially modelled the DC380, i should have posted it. In 4 cuft with an Fc of 30hz, for $80 and almost 93db efficiency, it's really hard to beat for this project at $400 a pair for parts. I'd like to remind about the cost of XO components here and in the case of the drooping response of the DC380, the low pass filter won't be that bad if we're crossing to a mid in the 400hz range. A very simple LR2 filter will work here.

[djg]

Re: Is there interest in a large three way "monkey coffin" collaboration?

Loren, you have worked hard to get this project going.

Have you considered what sort of person is going to want to build this? I am thinking that there might be a significant number of people with older equipment that don't want to get into subwoofers and home theater. They have some old speakers that need replaced and would slide the Sansuis out and slide the "Lorens" in. They like their old style stuff and would be attracted to a project that is as much like what they had as possible.

And perhaps the deliberate retro fans. They have some money, they have their esoteric turntables and their monoblock tube amps. They might like a project with a deliberate retro tilt.

To me, both of these groups would be served by a high efficiency vs bass extension response.

It's your project, just some thoughts. I'm thinking you would like this project to be a bit different and unique.

[joeybutts]

Re: Is there interest in a large three way "monkey coffin" collaboration?

Do you like them?

I do. I have yet to play with eq'ing them, but I will tell you that sensitivity and power handling won't be an issue with them. I'll play around with them a bit today to really give you a personal critique.

[Whitneyville1]

Re: Is there interest in a large three way "monkey coffin" collaboration?

Most tweeters will "keep-up" with all but the most sensitive woofers with BSC and XO losses figured in. 4 cu. ft. is getting pretty big. That's the size of the "medium" mini-fridges or a keg-cooler (inside). Tossing some rough prices; $100-12" woofer; $45-mid; $30-tweeter, so $350 for drivers for a pair. $75 each for XO parts and misc. doable? I know I'm shooting a little high on drivers (safe).
Mayhem's room gain point is valid too. The lower you go, to about 23Hz or so, the more room gain I get in my living room. If an F3 of ~32 Hz helps the entire project $50-100 worth, which it might, it should be considered.
I think we need to focus on these being "music" speakers, and for home theater, they'll be "large front mains". You still will need a sub if you want the real HT experience. The advantage I see to these is you get an octave lower than most 14-16 liter 6 1/2-7" MT's for way less than a sub and the bookshelf monitors.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

Clearly room gain in the last octave shouldn't be ignored. My current speakers are in a "small vented box tuned low" alignment that starts sagging a little at 40 hz or so but the Fb is way down at 21. I love the bass presentation they give in my room.

I think a sealed box with F3 of 35 to 40 hz would be perfect for this project.

So the DC380 in 4 cubic feet would give a Q in the .6 range? I don't have my WBCD in front of me. I modeled it in 100 liters with walls covered (not stuffed) and it did a Q of .71 or so and had an F3 of 41 hz or something. It would work great from perspective of the response shape. I think it's main limiting factor is the limited xmax. 4mm is pretty meager and the output at 30 hz won't crack 100 db. Perhaps that is loud enough though. The drooping response would make crossover easy. I just wish it had a little more Xmax.

I'm open to DC380 if people think it works best, but the ST-305 has nearly the same sensitivity, will give better extension in the same size box (vented for the series 2) and has much more output capability due to better xmax and better power handling.

Which would be preferrable to more folks.

[ATTACH=CONFIG]48170[/ATTACH]When looking at bass response, it's important to remember the sims are anechoic, which don't take into account the likely 6-8 db boost below 30hz common in most 'home' spaces.

when i initially modelled the DC380, i should have posted it. In 4 cuft with an Fc of 30hz, for $80 and almost 93db efficiency, it's really hard to beat for this project at $400 a pair for parts. I'd like to remind about the cost of XO components here and in the case of the drooping response of the DC380, the low pass filter won't be that bad if we're crossing to a mid in the 400hz range. A very simple LR2 filter will work here.

[lorenmjones]

Re: Is there interest in a large three way "monkey coffin" collaboration?

These are well stated thoughts djg. I do want this to be something a little uncommon or unique relative to what is commonly built here, not that there is anything wrong with doing your own take on a small 3 way or a 2 way bookshelf or etc.

I think you are right that it would be nice to have these be a replacement for vintage boxes that finally give up. The goal would be similar form factor and feel, sound better than the original and do it for a reasonable budget.

I think I am seeing everyone's point on better efficiency, keeping impedance at 8 ohms and sacrificing the last 2/3 octave of extension in the tradeoff. Makes sense to me. ST-305 should give us that. DC380 sealed would as well but won't have the same output due to the xmax being limited. But perhaps the sealed 15" woofer has enough appeal on its own to overcome that limited max output.

Loren, you have worked hard to get this project going.

Have you considered what sort of person is going to want to build this? I am thinking that there might be a significant number of people with older equipment that don't want to get into subwoofers and home theater. They have some old speakers that need replaced and would slide the Sansuis out and slide the "Lorens" in. They like their old style stuff and would be attracted to a project that is as much like what they had as possible.

And perhaps the deliberate retro fans. They have some money, they have their esoteric turntables and their monoblock tube amps. They might like a project with a deliberate retro tilt.

To me, both of these groups would be served by a high efficiency vs bass extension response.

It's your project, just some thoughts. I'm thinking you would like this project to be a bit different and unique.