What should be the optimal volume for a K145 woofer?
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What should be the optimal volume for a K145 woofer?
The optimum box volume would be the one where response is relatively flat in view of volume and tuning frequency you determined as giving what you're looking for (suits you) after modeling different scenarios in speaker software (bass extention/flatness vs cab size/tuning).
In the Enclosure Guide JBL suggests, for the E145, 4 cu.ft. tuned to 40hz. However, yours is slightly different being the K145. In the JBL box plans/porting info i have for the K145 the volume given is 3.75 cu.ft. (these appear to be NET cab volumes). So the volume difference calculated between those two is relatively small. If you implement the Giscard Vas correction mentioned below it might make sense to use the 4 cu.ft. box (subject to software confirmation).
The relevant driver parameters regarding cab sizing and tuning are Fs, Qts and Vas, as determined by Engineer D.B. Keele.
K145: Fs 35 hz, Qts 0.29, Vas 244 L, as per JBL TS table
E145: Fs 35 hz, Qts 0.25, Vas 275 L as per TS table, however there was a Vas correction here, issued by Giscard, at 428 L . Hopefully the above info will help you.
Richard
Basically what Richard said. I would model it you may be able to get a little more bass extension in a bigger box. They are not subwoofers.
Rob :)
After writing my post i uncovered a little wrench in the wheel with regards to K145. There were two versions of it! The older one from 1973 (document's year) which doesn't have Fs 35 hz as indicated in the TS table but instead has Fs 45 hz as mentioned in the specs column attached. Note also the 94 db sensitivity.
A 10 hz difference is notable and might well prevent that driver from going very low bass wise (at least not as comfortably deep as the 35 hz version).
Later during the 70's, but before the E series, i think the K145 was "reworked" to improve its performance based on some data in the K series brochure i have. At that time it could have been engineered to meet the Fs 35 hz spec. On the second pic note the more recent K145 has a sensitivity of 98 db.
The higher Fs on the oldest K145 units should only be a concern for owners of these and incite them to moderate somewhat their VLF expectations compared to those having the Fs 35 hz version. The bugger is knowing if your K145 units belong to the first or the second group... Need for measurements i guess.
Looking at D.B. Keele's equations to model a cab and tune it properly, i see that driver Fs is used not only to determine Fb but also to calculate F3. (btw to calculate Vb you need Vas and Qts). So driver Fs does matter and will have an impact on the results.
Richard
I have a box close to 5,5 cu ft. The environnement is in my house listening for film, live shows, vinyl and studio recording. And I will have electronic xover, triamplified system.
Will you be using a sub along with the K145s? For a movie playback system I can't imagine the K145s will be satisfactory without VLF help. They are awesome for the 50-800Hz range, but not so much below that.Quote:
Originally Posted by maxserg
I would use a 4 cu ft box tuned to 40Hz as a starting point and experiment from there... and I would plan on using a sub or two.
Widget
5 cu. ft. tuned to 45Hz with two 4 inch vents 3.68 inches long gives an F3 of 45 Hz according to WinISD
No sub for now. I know that for films I would need it! But to mate the output of the K145 it should have a hell of output.Quote:
Originally Posted by Mr. Widget
That seems reasonable. I need to get Bass Box Pro back up and running. :banghead:Quote:
Originally Posted by turnitdown
Widget
Interesting that the "145" series was used by JBL in box sizes ranging from the 4628 (4.5ft3) to the DD55000 (calling it a 150-4H) using something like 8ft3 and tuned low (around 35Hz) for the target market/environment... perhaps not everyone's cup of tea, but effective in its intended range/use.
https://www.audioheritage.org/html/p...bl/everest.htm
Thanks to all!