Looking for dual E145 VB porting

[Izzy Weird]

Hello,

I am working on plans for a Fender Dual Showman style of cabinet for two JBL E145, and plan to add PVC tube ports. I am estimating the box will be about 7 cu. ft. I am guessing that four 4" dia PVC ports (maybe four 6" dia) are possible.

(I figure probably a QB3 alignment, but I could be talked out of it. This is for bass guitar, including 5-string.)

Unfortunately many of the free vented box calculators I have found seem to be for single drivers, or are not set to predict response for various porting schemes and a fixed Vb. Any recommendations?

Thanks,
Izzy

[Zilch]

Black = 50 Hz

Red = 40 Hz

Green = 30 Hz

F10 (cursor) is 48 - 50 Hz with any of them.

[Izzy Weird]

Hi Zilch,

Thanks a lot for the curves. My eyes lit up on the thought of 30 Hz tuning (Fb?, correction: F3) until I got to the lower graph.

Hmm, perhaps I should increase Vb a tad. I suppose 10 cu. ft. isn't out of the question for a portable cabinet.

I have had more experience playing through D140s, and Altec 421A. But people tell me the E145 was/is an excellent bass guital woofer. I guess it will be hard to hurt them using a tube amp that clips at 80 W.

(Oops, I intended for dual 15" drivers and somehow got dual postings. I hope a moderator can zap one of them.

Izzy

[Izzy Weird]

I found an old JBL document recommending a 9 cu. ft. cabinet for two E145 with a 40 Hz tuning.

http://www.jblpro.com/pub/components/eseries.pdf

Looking at this from another angle, an open B string on a 5-string bass has a fundamental of 30.86 Hz.

While a cabinet with two of these might be great for a 4-string (low E = 41.2 Hz), perhaps there are better speaker choices for a 5-string.

In either case, I sure do appreciate the graphs. They were very helpful.

Izzy

[Zilch]

I have tried on several occasions to model E145s to play low. It's not what they do.

Johnaec is a working bass player and has experience with this. Send him a PM and ask him to post in this thread.

While I do have E145s and E140s here, my experience with designing for them is limited. I'm basically just clicking buttons. The second graph is RMS power, and probably directly applicable to your design. Clipping makes the dissipation worse, of course, but it's excursion limits that are controlling at the frequencies of interest here.

I do also know that the models better represent actual performance than a couple of guys oogling E145s in a box with brews in their hands and babes at the bar....

[Izzy Weird]

Thanks again for the graphs, Zilch. I think I will need to play around with tunings before deciding on whether to do this, and how I might do it. Perhaps this amp may not be the best for the 5-string. I sure remember how much I loved playing through my JBL D140F speakers, even using a solid-state Kustom head.

I notice that Bassbox 6 Pro is not prohibitively expensive, is this the one you would recommend if I was going to play around with cabinet tunings?

If you can spare the time, could you possibly run another set of curves using 10 cu. ft., two E145-8 drivers, and favoring tunings 40 Hz and below? I don’t know if this stuff interests anyone else here, but I find it fascinating.

Thanks again,
Izzy

[johnaec]

Looking at this from another angle, an open B string on a 5-string bass has a fundamental of 30.86 Hz.

While a cabinet with two of these might be great for a 4-string (low E = 41.2 Hz), perhaps there are better speaker choices for a 5-string

While an E145 can get down to 40 hz, there's still some roll-off, and it just doesn't have the Xmax to handle 30 hz at levels typically found with live bass guitar, though 2 of them will still be capable for a lot of stuff - just don't expect earth shaking volume at 30 hz, (though you may be surprised - coupling helps a lot).

I play both 4 and 5 string bass, and other than getting multiple cabinets, there are only a few JBL options that can realistically do 30 hz at live, (club), volumes.

There's the 18" 2242H, ('still needs a somewhat large cabinet), the discontinued 15" Sub1500, (which is what I use, but in a 4628B cabinet, which is good for really solid 40 hz, but I need to build a new cabinet to get solid 30 hz, and I'm also using 900 watts RMS to compensate for the low efficiency), the 15" W15GTI car sub, ('probably your best bet for a small cabinet, but will also need a lot of power), and the newer JBL Pro differential drivers, ($$$!!).

You'll want a minimum of about 25mm Xmax for 30hz at club levels - that will do a pretty good job for live 5 string bass, (with a true, linear 30 hz capability). And like the 8" mid in the 4628B cabinet I'm using, for best sound, (especially with the W15GTI's very heavy cone), I recommend augmenting any of these speakers with something for the higher harmonics. My new cabinet will use a 10" E110 for this.

John

[Zilch]

A single in 10 CF tuned to 30 Hz will get 115 dB at 30 Hz F10 with 30 watts.

With duals it all moves up to 40 Hz, 121 dB, and 60 watts.

Interestingly, the acoustic power curve has it playing to 30 Hz if tuned that low, but the frequency response plot doesn't reflect that.

Yes, buy BB6P and do this stuff.

[Izzy Weird]

Thanks again, Zilch, and thank you John as well. This board is not only loaded with expertise, but most of us have similar preferences in speakers, like JBL.

The dual 15” might be sufficient for practice, studio, and small gigs, a nice vintage blonde Dual Showman repro with E145s. Sweet.

For larger venues how about a JBL SRX728S, a Bergantino NV610, and a couple of Fender Bassman Pro 300 heads to drive them? (Or substitute your favorite solid state amps.)

http://img3.guitarcenter.com/dbase/pics/products/5/7/2/280572.jpg

http://www.bassemporium.com/images_products/bergnv610.jpg

http://images.miretail.com/alternate//products/extra/Fender/432245.jpg

And when I’m not gigging (most of the time) I could augment my B460 subs with the SRX. I’m sure the Crown CE4000 will drive both to the levels I like to hear if I run it on 240 V.

Aren’t you glad you’re not one of my neighbors?

Izzy

[johnaec]

For larger venues how about a JBL SRX728S...

Or could could simply get a JBL VT4881A: http://www.jblpro.com/vertec1/new_vertec/vt4881a.html

It uses the new 18" 2269H differential drive speaker, with dual 4" voice coils and 3.5" peak-to-peak excersion!

If you want dual 2269H drivers, there's always the VT4880A: http://www.jblpro.com/vertec1/new_vertec/vt4880A.html

John

[Izzy Weird]

Yes, the VT4880A is another one I have been looking at, but it is much more expensive.

I wonder (not considering SPL capability) which of those two models sounds better, the SRX728S or the VT4880A.

I wonder if two separate cabinets would be a better way to use two E145 drivers, given the apparent Vb needed to go as low as possible. The later ('67) Fender Dual Showman cabinet had an outside volume of about 9 cu. ft. Use two repro versions of this, and cover the second 15" hole with a plate containing the port(s). This also makes it fairly simple to try different port dimensions.

Izzy

[Izzy Weird]

Well, looks we are comitted here. I hope to have the construction of this amplifier up on a web site. It is to be a blonde Fender Dual Showman "repro" with some serious upgrades (for use as a bass amp).

First of all I will use two JBL E145 speakers instead of D130 or D140. I won two E145 baskets today. Will be having them reconed at a JBL dealer with JBL kits. http://cgi.ebay.com/ws/eBayISAPI.dll...m=280135421077

I have yet to find a cabinet maker who can construct nice blonde Tolex "Fender-like" cabinets. A Weber chassis is on order as are the power and output transformers. The OT is a Hammond weighing almost 3 times as much as what Fender used.

Izzy