JBL 2235h as a backfire

[Dr.db]

Hey folks,

I was thinking about a backfire setup with my 2235h`s....

They would be mounted in the back of my stereo-speakers facing the wall. Would this be all right or any problems with that....!?

The will play just below ~100hz I reckon....


Thanks in advance!!
Olaf

[Lee in Montreal]

100Hz is quite high if you use the 2235 as a sub. JBL's B380 subwoofer was cut at 70Hz. I cut mine at 60Hz.

[Rolf]

What do you want to use from 100Hz and > ?


Hey folks,

I was thinking about a backfire setup with my 2235h`s....

They would be mounted in the back of my stereo-speakers facing the wall. Would this be all right or any problems with that....!?

The will play just below ~100hz I reckon....


Thanks in advance!!
Olaf

[Ruediger]

How do You calculate/ predict Your design?

How are You going to implement the crossover? Active or passive? If You are going passive: what components do You need? What is the value of Re in the series coil? What will be the influence on the speaker's Qt?

Ruediger

[Dr.db]

These question`s seem to make a lot sense, but unfortunatly I cannot answer all of them.....

My setup is a 4-Way system including 2235h(low), K-120(mid-bass), 2440h(mids) and 2405(high).....
2235h should be running in ~150liter bassreflex.... K-120 shell be running as direkt radiator too, but not shure about the encloshure jet....


The whole system will have a passive crossover-network. My friend is pretty good at this, so I leave it up to him as far as I do not understand anything about this...


This is the best I can answer your sensefull questions, I hope this will lead us forward. :)

[Ruediger]

These question`s seem to make a lot sense, but unfortunatly I cannot answer all of them.....

My setup is a 4-Way system including 2235h(low), K-120(mid-bass), 2440h(mids) and 2405(high).....
2235h should be running in ~150liter bassreflex.... K-120 shell be running as direkt radiator too, but not shure about the encloshure jet....


The whole system will have a passive crossover-network. My friend is pretty good at this, so I leave it up to him as far as I do not understand anything about this...


This is the best I can answer your sensefull questions, I hope this will lead us forward. :)

I would suggest a three-way system without the K120.

The point is: a series coil for an 80 Hz crossover which You can afford will have an Re which will spoil the Qt of the 2235.

Let Your friend recommend You a series coil, check the price and the electrical resistance Re, and calculate a new Qt for the 2235. Then calculate a cabinet for this "modified" 2235.

If You stay with a three way system the series coil can be 1/10th the inductivity.

Ruediger

[Lee in Montreal]

If the driver/cone is facing forward and used for up to 100Hz, while the bass reflex duct is directed toward the back and tuned to 20Hz, there will be no problem, providing you leave 30cm to allow the wave to spread. The 20Hz bass is non-directional. To about 40-50Hz, which is where it is possible to feel where it comes from. If you run a four way system, I would still crossover lower than 100Hz and use the 2235h as a sub.

To make a good quality passive crossover with good size inductors, you will easily be into the $700 budget in parts only. Not to mention all the electronic phase problems when crossing below 120Hz. Basically, be prepared to buy an active crossover and four amps. It will give you unlimited control. CDs and vinyl aren't engineered the same way. Today's music and the one from 30 years ago sound very differently. When you have a passive crossover, you are stuck with one setting. With an active crossover, you can taylor the sound to your sources.