Building an Enclosure Around a D.A.S D-401 2395 Clone

[RMC]

Hi Robert,

Thinking about all this one more time, at this point it may be best to keep the 8 cu. ft. box since that volume IS correct and keeping the 45 hz tuning frequency also makes sense in the context of two possible driver Vas numbers (275 L. from JBL or 427.7 L./15.1 cu. ft. calculated by 4313B in a 2003 post about the purpose of the E-145). If JBL's number is right, you get a small bump in the lows to sort of "match" with driver rising mid response, therefore "balancing" the sound. If 4313B's number is right, you get flat bass response which you say is not a problem with your Driverack to adjust or equalize to again sort of "match" levels with the E-145 rising mid-bass response. Keeping things as is for now, you can get "the best of both worlds" as they say, or face either applicable scenario. Not a bad thing at all, and a great outcome in this dilemma.

As for the proper vent length issue in the new version of Win ISD, I'll install the software and check that, plus I'll also review my vent numbers in Winspeakers...
Will be back in the near future.

Richard

[robertg]

Hi Robert,
In the older versions I used when you opened a project in the "Box" Tab at bottom left there's an "Advanced" mention that can be clicked-on and shows for rear chamber the boxe's QL, Qa, Qp numbers used, plus these can be changed manually if you clicked on the QL number for example another box opened and you can write 7 instead of 10 or vice versa.
Richard

If I change the QL to 7 from 10, it flattens the hump at 50 Hz. The Qa and Qp are 100. When I change the box tuning frequency to 55Hz, it gives me a vent length of 3.26 cm, close to 1 1/4". There is still a bit of a hump at around 65 Hz and then it drops down around around 100 Hz.

[RMC]

Hi Robert,

No time now, I'll be back tonight to answer your issues in your last post # 47 plus some news on vent length...
After many attemps, the new Win ISD just won't install on my laptop computer... Free software with free bugs! That's why I paid $40.US to get Winspeakerz. See you tonight.

Richard

[RMC]

Hi Robert,

Using QL 7 as a starting point, like in most software, is more reasonable than QL 10. Losses do exist.

It's normal that at QL 7 instead of QL 10 the previous bass bump went away with same box volume/tuning . In a way, box air leaks mean air wasted that is not used to produce bass. Had you tried QL 3 or 5 you would have seen a dip in LF response! You've figured by now that low QL means lossy and high QL means air tight. But also that more lossy boxes mean weaker bass response... In addition to that, large boxes tend to be more lossy than small ones, hence Leach's suggestion to use lower QL (e.g. 5) for large cabinet design. You will have to go the extra mile to try to achieve QL 7 in a larger box. See further below. BTW don't change the Qa (absorption) and Qp (port losses) in the software unless you know what you are doing.

It's also normal that when you tuned the box to 55 hz in the software, instead of 45 hz, the small bump moved higher at 65 hz since you are then tuned higher. There remains the question of how long the vent need to be (see further below). Before settling on a 55 hz tuning frequency (Fb) I would definitely try to measure the Fb with the vents you have now with an Audio Test CD as I use (or an iPhone app or other that some also use) for frequency generation/counting to see what is the actual Fb you get now. With reasonable sound level, while frequencies go by in your sound system (e.g. from 60 hz to 40 hz) you barely touch the woofer cone near the surround to feel the woofer vibrations. At the point of least or no vibration you have the tuning frequency and take note of it. Any Fb in the range of 45-50 hz is ok for that box. This implies "finalizing" the boxes acoustically with the drivers in their place (no need to connect horn and tweeter), except the vents may be subject to re-work. For temporary caulking around the vent/cab junctions inside the cabinets I use Canadian Tire's Climashield, Crack Shield, product # 64-2545-0. Sticks on but removeable. Easy on, easy off, in case vents would need to be changed.

if you're not meticulous about air leaks you'll get more than you need and the bass will suffer. To compensate for box air leaks the remedy is usually an increase in box volume (Vb), not practical here because your boxes are built. You can model that in Win iSD by changing QL number. If you end-up with QL 3 or 5 (lossy box), instead of a QL 7 flat reponse for example, you will get a low-frequency dip for same volume/tuning, and to get flat response again you would need to increase box volume... You're better off working meticulously with the caulking tube/gun!

All inside joints, input terminals, around vents, etc. need to be really air tight. Plus, good quality gaskets (foam or rubber with some thickness to fill front panel minor defects where drivers sit when under pressure from screwed-in drivers) must be used to seal driver/cab, not the cheap cardboard/paper ones.

Input terminal leaks are often the bugger. The perimeter needs to be siliconed from inside the box once installed. Moreover, some input terminals even have some holes on their back side for whatever reason (seen from inside the box) and these holes somehow often connect or lead to binding posts, push terminals or 1/4" plugs on the outside face. ANY POSSIBLE way for air leaks here MUST be plugged with silicone. Seen some plastic terminals with a bit of loose around the back side's metal terminal: again silicone that minuscule space where the loose is. After all this is done, then you can hope for a large box with QL 7. As Bullock said, air must have absolutely no way to exit but through the vent... Amen !

Though the new Win ISD doesn't want to install itself on my laptop, In addition to Winspeakerz and older Win ISD, I still have other credible resources from the "good old days" of speaker building to determine vent diameter (Dv) and length (Lv). JBL Pro published a long time ago a porting chart, developed by R.H. Small, to help in tuning vented boxes. This is NOT the same as what JBL provided in the past with their "Speaker Enclosure Construction kits" for home or Pro builders. There is no reference whatsoever on this document to any JBL drivers or boxes. Just a lot of Vb, Fb, Va (vent area), Dv and Lv dimensions. Mc Cauley speakers also issued a similar one named "Alignment Graph". A smaller version of that chart or graph is also reproduced in John Eargle's (JBL) books: Handbook of Sound System Design, 1989, P. 109; and in his Loudspeaker Handbook, 1997, P. 68.

Since this chart/graph relates to a single vent and you have three of them (3 X 4"= 37.7 sq. in.) I took numbers for a tiny bit less than a 7" vent (38.48 sq. in., which in itself is already pretty close at ± 3/4 of a sq. in.) to get an idea regarding required vent length. For your given Vb (8 cu. ft.) and Fb (45 hz) with above-mentioned vent size, I get a vent length of 1" to 1 1/4", the latter number being what you already have in your boxes and also what Winspeakerz had given me. As I indicated above, in your shoes I would test your boxe's present tuning frequency before touching those vents. Regards,

Richard

[robertg]

I'm pretty sure it's going to be air tight, I used a lot of glue, and there is a screw every 4 inches. Hopefully I will have everything together in a couple of weeks so I can test.

[ivica]

Hi, the difference in the F/R response would not change much changing from 150 lit to 225 lit, but adding about 2 ohm resistor 'in-line' with the driver would reduce mid-bass rising in the response... regards ivica

Hi E145 & 225 Lit Fr=45Hz with 2 Ohms regards ivica

[RMC]

Hi Robert,

Sorry, but being pretty sure the box is air tight because you used a lot of glue isn't enough to be REALLY air tight. You DO have to silicone everywhere I mentioned otherwise you WILL have more losses than expected. And the bass will suffer...

When I built my first (of a pretty long series of boxes) in 1981 I had used LOTS of glue and screws as you did, only to find out later-on that I DID have a number of air leaks which affected bass from those low-frequency enclosures... Had to re-do all the interior air tightening to fix the problem, and doing it afterwards IS a pain in the neck. Since you are still at the construction phase its easier. Re-doing it after is too late and harder...

NOTE TO IVICA:

Out of curiosity which speaker design software do you use to show us these response curves?

I have a problem with using a resistor in series with a woofer, over and above a crossover...

Also, with a 300 W program material power capacity driver which 2 ohm resistor will easily handle that much power?

The resistor reduced the mids of 2-3 db but also seems to affect a little the bass from < 70 hz which one could have expected since a resistor in series with a woofer doesn't impact only woofer mids but the whole woofer...

To me it seems more natural to try to improve the response with some box tuning tweaking VS a resistor. Regards,

Richard

[RMC]

Hi Robert,

To satisfy my curiosity, I checked using D. B. Keele's formulas for vented-box design the ones (Imperial and Metric), he developed for vent length calculations, to see if any discrepancies with Small's chart/graph I mentioned yesterday (1"- 1 1/4") and what I gave you earlier from Winspeakerz (1.23").

BTW since I needed an exact diameter figure to plug into Keele's equation for vent length, I first had to determine the exact vent diameter your 3 X 4" vents would represent as a single vent. The answer is a Dv of 6.9282" which, as I mentioned yesterday, is pretty darn close to a tiny bit less than a 7" vent that I used in Small's chart/graph.

With that plugged into Keele's equation for Imperial measures along with other numbers (Vb 8 cu. ft., FB 45 hz, etc.) the vent length (Lv) determined is 1.2". On the Metric equation's side, the Lv is 2.91 cm (= 1.1447"). So all the vent length numbers I gave you (from three different sources) are pretty damn close to each other... That's another good reason to test your actual Fb before touching those vents! Since air leaks affect woofer performance ("perceived" box volume or air volume to "work" with), if you get weird Fb readings, box losses may be something to investigate, as well as the T/S of your bass drivers (e.g. original? reconed with aftermarket kits? etc.). Regards,

Richard

[ivica]

[QUOTE=RMC;408059....
NOTE TO IVICA:

Out of curiosity which speaker design software do you use to show us these response curves?

I have a problem with using a resistor in series with a woofer, over and above a crossover...

Also, with a 300 W program material power capacity driver which 2 ohm resistor will easily handle that much power?

The resistor reduced the mids of 2-3 db but also seems to affect a little the bass from < 70 hz which one could have expected since a resistor in series with a woofer doesn't impact only woofer mids but the whole woofer...

To me it seems more natural to try to improve the response with some box tuning tweaking VS a resistor. Regards,

Richard[/QUOTE]


Hi Richard,

I have used BassBox Pro sw,
Applying serial resistor with the bass driver has been applicable by JBL in the way that they enlarge the resistance of the L in their networks.
The result is lowering mid-bass, and some small amount of ultra low bass section.
Anyhow, I do not think E145 to be the best JBL driver for reaching ultra-low bass section, but may of the forum members love it for jazz reproduction, due to producing 'punch bass'/
Personally I would prefer 2245 (18") then 2231A (15", if possible to get), then 2235.
I have not heard 2216Nd (15", but 3inch vc, but would produce almost the same LF response as 2235), neither 2269ND (18").
It seems that with 2216Nd, and box (225Lit) tuned to 35Hz, F3 would 33Hz, almost flat response.

4367:
http://reconingspeakers.com/product/...2/#prettyPhoto
M2:
http://reconingspeakers.com/product/...bl-m2-5041785/


regards
ivica

[RMC]

Hi Ivica,

Thanks for your reply. Now I understand. It's not just putting a 2 ohm resistor in series with the woofer as your post # 51 implied... But rather "... has been applicable by JBL in the way that they enlarge the resistance of the L in their networks." That makes more sense, they do it in the crossover network, not just a 2 ohm series resistor alone.

As for the E-145 driver, well the thread name is "Building an enclosure around D-401/2395 clone" and Robert had a pair of E-145 sitting around (which CAN deliver some good bass). Why not make use of all that stuff (plus tweeters) since it CAN go all together in a box and make something worthwhile? The 8 cu. ft. box (largest recommended by JBL for E-145) is for the reason that Robert insisted on having the 2395 clone fit Inside the box perimeter as he didn't want the lens to extend 5 or 6" outside either side of the box...

As for the other woofers you mention they are irrelevant in the present context since Robert is not trying to build the best bass box possible but rather make good use of what drivers he already has... Plus the 2216Nd (links you referred to) in Canada would cost OVER $700.CAD each with just the currency exchange rate! I'm trying to help him make his thing fly (and I think it can do decently) instead of purchasing a new airplane! Gotta learn to work and find a way with what the "client" has, wants and can afford my friend. I always try to. Regards,

Richard

[robertg]

I do have a pair of 2226J drivers coming, but from what I have read everyone likes the E145 better.

Hopefully my DBX Driverack can straighten everything out without adding a resistor. I'm also thinking of making a single subwoofer if I need it. I doubt if I will, but I'll probably still make one anyway.

The cabinets are pretty well done, I'm just not sure if I like the shade of blue that I picked. They will be together when I finish restoring the lenses. That's a lot of work trying to straighten them.

[Ian Mackenzie]

Hi Robert

Have you seen this link?

http://www.audioheritage.org/vbullet...-E145-8-150-4H

Also Don's comments on the Everest

http://www.audioheritage.org/html/pr...bl/everest.htm

These links may provide some practical guidance on the application of the E145 for home Audio

Good luck

[robertg]

Hi Robert

Have you seen this link?

http://www.audioheritage.org/vbullet...-E145-8-150-4H

Also Don's comments on the Everest

http://www.audioheritage.org/html/pr...bl/everest.htm

These links may provide some practical guidance on the application of the E145 for home Audio

Good luck

It looks like I have the same low and high as the Everest, and the same cabinet volume. Those E145 graphs look like it doesn't reach its peak volume until 100Hz or so? I don't have very fussy ears, so I'm sure I will like the sound.

[RMC]

Hi Robert,

"I do have a pair of 2226J drivers coming, but from what I have read everyone likes the E145 better."
I don't own either drivers so I can't say for sure, but the E-145 is considered by many as one of the best drivers JBL made. Its a "darling" among the lineup.

On the other hand, It's not sure the 2226J (16 ohms version) would be a good fit for your present boxes, though JBL gives a recommended box size of 3-10 cu. ft. for 2226. It would have to be modeled in speaker design software to confirm a good fit or not, and a possible box re-tuning... The T/S parameters are different for E-145/2226 (Fs, Qts, Vas, etc.): 35/40hz; .25/.31; 275 (or 427.7?)/175 L, just to illustrate a few of them.

Are you planning the 2226 for subwoofer use??

I'm not a fan of a simple resistor in series with the woofer. Maybe in a pinch, as a last effort, if you are desperate... But then you would have to find a "large" power capacity resistor, if you can find one, and still use reasonable power input. Plus this would also affect driver impedance seen by amp.

My small bump tuning idea is also a way to "minimize" perceived different low/mid levels from E-145. Adjustable Parametric EQ on the "agressive or offensive" mid-bass level is another interesting alternative...

Richard

[robertg]

I wasn't planning on using the 2226 drivers for subs, could I? I was think of getting a 2242 or 2245. My preamp has a single sub output, 80Hz to 10Hz. I would run a UREI 6260 amp.